Drug resistance and genomic characteristics of Salmonella enterica serovar London from clinical and food sources in Hangzhou City from 2017 to 2021 / 中华预防医学杂志

Objective: To analyze the drug resistance and genomic characteristics of Salmonella enterica serovar London isolated from clinical and food sources in Hangzhou City from 2017 to 2021. Methods: A total of 91 Salmonella enterica serovar London strains isolated from Hangzhou City from 2017 to 2021 were analyzed for drug susceptibility, pulsed field gel electrophoresis (PFGE) typing and whole genome sequencing. Multilocus sequence typing (MLST), core genome multilocus sequence typing (cgMLST) and detection of drug resistance genes were performed by using the sequencing data. Phylogenetic analysis was conducted to compare the 91 genomes from Hangzhou City with 347 genomes from public databases. Results: No significant difference in the drug resistance rate was observed between clinical strains and food strains to 18 drugs in Hangzhou City(all P>0.05), and the multidrug resistance (MDR) rate was 75.8% (69/91). Most strains were resistant to 7 drug classes simultaneously. One strain was resistant to Polymyxin E as well as positive for mcr-1.1, and 50.5% (46/91) of the strains were resistant to Azithromycin and were positive for mph(A). All 91 Salmonella enterica serovar London strains were ST155, which were subdivided into 44 molecular types by PFGE and 82 types by cgMLST. Phylogenetic analysis showed that most strains from Hangzhou City (83/91) were clustered together, and a small number of human isolates from Europe, North America and pork isolates from Hubei and Shenzhen were mixed in the cluster. Other strains from Hangzhou City (8/91) were closely related to strains from Europe, America and Southeast Asia. Strains isolated from pork were the most closely related to clinical strains. Conclusion: The epidemic of Salmonella enterica serovar London in Hangzhou City is mainly caused by the spread of ST155 strains, which is mainly transmitted locally. At the same time, cross-region transmission to Europe, North America, Southeast Asia, and other provinces and cities in China may also occur. There is no significant difference in the drug resistance rate between clinical strains and food strains, and a high level of MDR is found in the strains. Clinical infection of Salmonella enterica serovar London may be closely related to pork consumption in Hangzhou City.

Etiological and epidemiological characteristics of Vibrio cholerae in Beijing, 2015-2021 / 中华流行病学杂志

Objective: To analyze the etiological and epidemiological characteristics of Vibrio cholerae in Beijing during 2015-2021 and provide evidence for the prevention and control of cholera. Methods: The V. cholerae strains isolated in Beijing during 2015-2021 were analyzed by serotyping and virulence genes detection. Pulsed field gel electrophoresis (PFGE) was performed for the molecular typing of the strains. Based on the collected epidemiological and clinical data of cholera cases,the epidemiological characteristics of cholera were analyzed by descriptive epidemiology method. Results: A total of 76 Vibrio cholerae O1 strains were isolated in Beijing during 2015-2021, including 61 strains from human, 10 strains from environment and 5 strains from seafood. The 76 strains consisted of 68 Ogawa strains and 8 Inaba strains. Six Ogawa strains isolated from sporadic cases carried ctxAB. After NotⅠ digestion, 76 strains were divided into 33 PFGE patterns. From 2015 to 2021, a total of 38 cholera epidemics were reported in Beijing, most of them were sporadic ones, accounting for 92.11% (35/38). A total of 45 cases were reported, and the cases occurred during June-September accounted for 97.78% (44/45). Cholera cases occurred in 9 districts of Beijing, and the cases reported in Chaoyang district accounted for 42.22% (19/45) and in Changping district accounted for 31.11% (14/45). The age of the cholera cases ranged from 19 to 63 years. Except for one case with unknown clinical symptoms, 44 cases had diarrhea symptoms with 84.09% (37/44) of the cases reporting diarrhea (3-9 times/day), followed by yellow watery stool (95.45%, 42/44), abdominal pain (68.18%, 30/44), nausea and vomiting (40.91%, 18/44) and fever (36.36%, 16/44). Conclusion: Vibrio cholerae strains isolated in Beijing during 2015-2021 were mainly O1 serotype Ogawa,most of which were non-toxigenic. The PFGE of the strains varied. Cholera epidemics occurred in 9 districts of Beijing, but most were sporadic ones with incidence peak during June-September.

Early identification of a clustered epidemic of typhoid fever through pathogen molecular subtyping monitoring / 中华预防医学杂志

Objective: To identify a suspected clustered Typhoid fever by whole genome sequencing(WGS) and pulsed field gel electrophoresis (PFGE) subtyping. Methods: The nature of the epidemic was determined by combination of subtyping results of isolates and epidemiological information. Results: Five S. typhimurium isolates showed identical PFGE patterns and almost the same whole genome sequence. Epidemiological survey showed that five cases had dined in the same restaurant on the same day. Conclusion: Combined with the longest incubation period of typhoid fever, molecular subtyping of pathogenic bacteria and the field epidemiological survey, it can be preliminarily determined that the five cases have common infection sources.

Combined application of field epidemiology and laboratory etiology analysis in the investigation of a foodborne disease outbreak in Xinjiang uygur Autonomous Region, 2016 / 中华预防医学杂志

Objectives: To analyze the causes of a foodborne outbreak in rural areas of Xinjiang between April 2 and April 5 in 2016. Methods: Cases and the relevant background information were obtained by consulting outpatient records of local health centers and regional people's hospitals and interviewing doctors and residents. All samples were collected by the laboratory test through epidemiological and food hygiene investigations. The χ2 test (Fisher's exact probability method) was used to compare differences in incidence rates. Molecular typing, virulence genes and single nucleotide polymorphisms (SNPS) were analyzed by using Pulsed Field Gel Electrophoresis (PFGE) and Whole Genome Sequencing (WGS). Results: A total of 142 cases were found in this study, with incidence rate at 5.7‰ (142/24 979). Among all cases, the main symptoms were nausea (94%), vomiting (92%) and abdominal pain (67%), and the incubation period was about 2 h (1-7.5 h). There were 16 Staphylococcus aureus isolates identified and all of them could produce A+C+E mixed enterotoxin. PFGE showed 100% homology. WGS further revealed that there were 9 and 1 strains contained by Sequence Type 1 (ST1) and ST5405, respectively. All ST1 strains were in the same clade on the genome tree. Among these, 7 strains shared close proximity (74 SNPs) and 2 strains shared close relationships as well (127 SNPs). The S. aureus isolates that caused the outbreak were introduced by a mutant isolate from the milk supply station. Conclusions: This foodborne outbreak was mainly caused by Staphylococcus aureus contamination.

Caracterização molecular de Staphylococcus aureus isolados de queijos artesanais da Serra da Canastra / Molecular characterization of Staphylococcus aureus isolated from artisanal cheeses from Serra da Canastra

O queijo Minas Artesanal da Canastra é produzido na Serra da Canastra (MG), utilizando leite cru, coalho e pingo, que é uma cultura endógena natural de cada queijaria. Devido ao uso de leite cru, o produto pode veicular microrganismos causadores de doenças veiculadas por alimentos, como Staphylococcus aureus. A caracterização molecular é uma ferramenta importante para avaliar a população microbiana do alimento e direcionar a aplicação de medidas de controle na produção. Este estudo caracterizou a diversidade genética, o potencial de virulência e determinou o perfil de susceptibilidade a antimicrobianos de S. aureus isolados de queijos produzidos na Serra da Canastra. Para o estudo transversal foram analisados 248 isolados de queijos que tinham um tempo de maturação de 22 dias, provenientes de 83 propriedades. Por outro lado, no estudo longitudinal foram analisados outros 197 isolados coletados ao longo do processo de maturação, provenientes de três propriedades. Os isolados foram submetidos a testes bioquímicos para confirmação do gênero e para a confirmação da espécie de S. aureus, foi identificado o gene nuc por meio da técnica de PCR. Além disso, foi pesquisado o gene mecA para a detecção de S. aureus Resistente a Meticilina (MRSA). Após os testes de confirmação, 144 isolados do estudo transversal e 159 do estudo longitudinal foram positivos para o gene nuc, específico para S. aureus. Posteriormente, o perfil clonal foi determinado por Eletroforese de Campo Pulsado (PFGE) utilizando a enzima SmaI e tipagem do locus agr por PCR multiplex. A análise por PFGE foi realizada no programa BioNumerics. A técnica PCR foi realizada para identificar a presença de genes que codificam a produção de hemolisinas, toxina TSST-1, enterotoxinas SEs (SEA, SEB, SEC, SED, SEE, SEG, SEH, SEI, SEJ, SEO, SEM), formação de biofilme e Componentes Microbianos de Superfície que Reconhecem a Matriz de Moléculas Adesivas (MSCRAMMs). Os isolados foram submetidos ao teste de susceptibilidade a antimicrobianos por disco de difusão. Por último, a formação de biofilme em microplaca de 96 poços, em caldo TSB a 37°C, foi verificada pela metodologia de Cristal Violeta. O gene mecA foi detectado em 1,9% dos 445 isolados. A tipagem agrrevelou que 83 (27,4%) dos isolados são do tipo agr-I, 95 (31,4%) agr-II e 43 (14,2%) agr-III, sendo que não foram detectados isolados classificados como agr-IV. A tipagem por PFGE revelou um total de 54 perfis. Assim, um isolado representativo de cada perfil foi utilizado nos demais testes que mostraram a presença dos genótipos spa mais frequentes t127 e t605 (20,58%); t002 (14,70%), seguidos pelos tipos t267 (8,82%); t1234 e t693 (5,8%) e t021, t177, t306, t321, t359, t442, t521, t693 e t5493 (2,9%). Além disso, encontramos a presença dos genes do grupo SEs, sea 1 (1,8%), seh 11 (20,3%), sei 10 (18,5%), sej 7 (12,9%), seg e seo 14 (25,9%), sem 8 (14,8%), e os genes seb, sec, sed, see e tst não foram detectados. Para os genes das hemolisinas, hla foi positivo em todos os isolados e hlb foi positivo em 53 (98,1%) isolados. Os genes positivos para MSCRAMMS foram fnbA, fnbB 18 (33,3%), clfA, clfB e eno 53 (98,1%), fib 44 (81,4%), bbp 4 (7,4%), cna 17 (31,4%) e ebps 10 (18,5%). Por último, os genes de formação de biofilme icaA e icaD estiveram presentes em 38 (70,3%) e 25 (46,2%) dos isolados, respectivamente. Na avaliação de susceptibilidade a antibióticos dos 54 isolados escolhidos, 25 (46,3%) apresentaram maior resistência a penicilina e 13 (24,0%) a tetraciclina. Em menor porcentagem (1,8%), 1 isolado cada foi resistente a eritromicina, cefoxitina, clindamicina, gentamicina, cotrimazol, azitromicina e trimetropim. Além disso, 8 isolados (14,8%) apresentaram resistência intermediaria a tetraciclina, 3 (5,5%) a gentamicina e 1 (1,8%) a tobramicina. No teste para a determinação da formação de biofilme por cristal violeta, 13,7%, foram classificados em isolados não formadores, 60,8% em fracamente formadores, 25,5% moderadamente formadores e nenhum como fortemente formador. A alta diversidade de cepas de S. aureus observada neste estudo mostrou que existem vários tipos de linhagens circulando na região da Canastra. A caracterização revelou uma elevada frequência de genes de virulência e que mais estudos são necessários para avaliar o potencial de produção de enterotoxinas nos queijos artesanais. A melhora dos procedimentos de higienização durante todas as etapas de produção pode ser uma solução para a redução dos níveis de contaminação por S. aureus

Canastra Minas Artesanal cheese is produced in Serra da Canastra (MG), using raw milk, rennet and a natural endogenous culture called pingo. Due to the use of raw milk, the product can carry microorganisms that cause foodborne diseases, such as Staphylococcus aureus. Molecular characterization is an important tool to assess the microbial population of food and guide the application of control measures in production. This study characterized the genetic diversity, virulence potential and determined the antimicrobial susceptibility profile of S. aureus isolated from cheeses produced in Serra da Canastra. A total of 248 isolates from 22 days ripened cheeses were obtained from 83 properties (cross sectional study). Another 197 isolates were collected during maturation (longitudinal study), in three properties. The isolates were submitted to biochemical tests to confirm the genus and to confirm the S. aureus species, the nuc gene was identified by PCR. In addition, the detection of mecA gene was performed for the detection of Methicillin Resistant S. aureus (MRSA). After confirmation tests, 144 isolates from the cross-sectional study and 159 from the longitudinal study were positive for the nuc gene, specific for S. aureus. Subsequently, the clonal profile of the isolates was determined by Pulsed Field Gel Electrophoresis (PFGE) using the SmaI enzyme and typing of the agr locus by multiplex PCR. PFGE analysis was performed using the BioNumerics program. PCR was performed to identify the presence of genes encoding the production of hemolysins, TSST-1 toxin, enterotoxins SEs (SEA, SEB, SEC, SED, SEE, SEG, SEH, SEI, SEJ, SEO, SEM), biofilm formation and microbial surface components recognizing adhesive matrix molecules (MSCRAMMs). The isolates were submitted to the antimicrobial susceptibility test by disc diffusion. Finally, biofilm formation in a 96-well microplate in TSB broth at 37°C was verified by the Cristal Violeta method. The mecA gene was detected in 1.9% of the 445 isolates. Agr typing revealed that 83 (27.4%) of the isolates are agr-I, 95 (31.4%) agr-II and 43 (14.2%) agr-III, and no isolate was classified as agr-IV. PFGE typing revealed a total of 54 profiles. Thus, a representative isolate of each profile was used in the other tests that showed the presence of the most frequent spagenotypes t127, t605 (20.58%); t002 (14.70%), followed by types t267 (8.82%); t1234, t693 (5.8%) e t021, t177, t306, t321, t359, t442, t521, t693 and t5493 (2.9%). In addition, we found the presence of the genes of the SEs group: sea 1 (1.8%), seh 11 (20.3%), sei 10 (18.5%), sej 7 (12.9%), seg and seo 14 (25.9%), sem 8 (14.8%), while seb, sec, sed, see and tst genes were not detected. For hemolysin genes, hla was positive in all isolates and hlb was positive in 53 (98.1%) isolates. The positive genes for MSCRAMMS were: fnbA, fnbB 18 (33.3%), clfA, clfB e eno 53 (98.1%), fib 44 (81.4%), bbp 4 (7.4%), cna 17 (31.4%) and ebps 10 (18.5%). Finally, the biofilm formation genes icaA and icaD were present in 38 (70.3%) and 25 (46.2%) of the isolates, respectively. In the evaluation of antibiotic susceptibility of the 54 isolates, 25 (46.3%) showed greater resistance to penicillin and 13 (24.0%) to tetracycline. In a lower percentage (1.8%), 1 isolate each was resistant to erythromycin, cefoxitin, clindamycin, gentamicin, contrimazole, azithromycin and trimethoprim. In addition, 8 isolates (14.8%) showed intermediate resistance to tetracycline, 3 (5.5%) to gentamicin and 1 (1.8%) to tobramycin. In the test for the determination of biofilm formation by crystal violet, 13.7% were classified as non-forming isolates, 60.8% as weakly forming, 25.5% moderately forming and none as strongly forming. The high diversity of S. aureus strains observed in this study showed that there are several types of strains circulating in the Canastra region. The characterization revealed a high frequency of virulence genes and that further studies are needed to assess the potential for enterotoxin production in artisanal cheeses. The improvement of hygiene procedures during all stages of production can be a solution for reducing the levels of contamination by S. aureus

Distribución y caracterización fenotípica y genotípica de Listeria monocytogenes en aislamientos de alimentos, Colombia, 2010-2018 / Distribution and phenotypic and genotypic characterization of Listeria monocytogenes isolated from food, Colombia, 2010-2018

Resumen | Introducción. Listeria monocytogenes es un patógeno transmitido por alimentos que causa infecciones en humanos, entre ellas, meningitis, meningoencefalitis y septicemias, así como abortos. Con la tipificación serológica se han identificado 13 serotipos, siendo el 4b el causante de la mayoría de los brotes en el mundo. Objetivo. Determinar la frecuencia y la distribución de los serotipos y subtipos moleculares de L. monocytogenes aislados de alimentos en Colombia entre el 2010 y el 2018. Materiales y métodos. Se hizo un estudio descriptivo y retrospectivo a partir del análisis de 2.420 aislamientos que fueron identificados como L. monocytogenes y otras especies, por medio de pruebas bioquímicas, serológicas y de subtipificación molecular mediante electroforesis en gel de campo pulsado (PFGE). Resultados. De los 2.420 aislamientos recibidos, 2.326 fueron confirmados como L. monocytogenes. Los serotipos encontrados fueron: 4b (52%), 4d-4e (14,5%), 1/2a (11%), 1/2c (9,4%), 1/2b (9 %), y 3a, 3b, 3c, 4c, 4d, 4e y 7 (menos de 2%). Procedían de Bogotá (43%), Antioquia (25%), Valle (10%), Nariño (9%) y otros departamentos (7%). La caracterización genotípica agrupó los aislamientos evaluados en 167 patrones de PFGE; los perfiles más frecuentes se presentaron en productos lácteos, cárnicos y alimentos preparados. Conclusión. El 96,1 % de los aislamientos correspondieron a L. monocytogenes, con una buena concordancia entre el aislamiento y la identificación; el serotipo 4b, extremadamente virulento, fue el más frecuente. El análisis molecular evidenció la posible diseminación y permanencia en el tiempo de varios serotipos, lo que resalta la importancia de incluir este patógeno en los programas de vigilancia epidemiológica en alimentos.

Abstract | Introduction: Listeria monocytogenes is a food-borne pathogen that may cause infections in humans such as meningitis, meningoencephalitis, and septicemia, as well as abortions. By serological typing 13 serotypes have been identified of which 4b is responsible for most of the outbreaks in the world. Objective: To determine the frequency and distribution of serotypes and molecular subtypes of L. monocytogenes isolated in Colombia from food from 2010 to 2018. Materials and methods: We conducted a retrospective and descriptive study based on the analysis of 2,420 isolates confirmed as L. monocytogenes and other species using biochemical and serological tests, and pulsed-field gel electrophoresis (PFGE) for molecular subtyping. Results: Of the 2,420 isolates received, 2,326 were confirmed as L. monocytogenes. The serotypes found were 4b (52%), 4d-4e (14.5%), 1/2a (11%), 1/2c (9.4%), 1/2b (9%), and 3a, 3b, 3c, 4c, 4d, 4e and 7 (less than 2%). The isolates came from Bogotá (43%), Antioquia (25%), Valle (10%), Nariño (9%), and other departments (7%). The genotypic characterization grouped the isolates in 167 PFGE patterns. The most frequent patterns were identified in various dairy and meat products, and in prepared foods. Conclusion: A 96.1% of the isolates corresponded to L. monocytogenes showing good agreement between isolates and identification. Serotype 4b, highly virulent, was the most frequent. The molecular analysis showed the possible dissemination and permanence over time of several serotypes, which highlights the importance of including this pathogen in epidemiological food surveillance programs.

Streptococcus pneumoniae serotype 3 genotypes in invasive isolates from Colombia / Genotipos del serotipo 3 de Streptococcus pneumoniae en aislamientos invasivos en Colombia

Abstract | Introduction: Streptococcus pneumoniae serotype 3 is an important cause of pneumonia, bacteremia, and meningitis. Objective: To establish the circulating genotypes of S. pneumoniae serotype 3 isolates recovered from the invasive disease between 1994 to 2015 in Colombia. Materials and methods: Of the 365 S. pneumoniae serotype 3 isolates recovered through the laboratory national surveillance program, 117 isolates were analyzed. Pulsed-field gel electrophoresis was used for genotyping, and multilocus sequence typing was determined in representative isolates. Results: The frequency of this serotype increased from 2.7% between 1994 and 1998 to 9.1% between 2011 and 2015 (p=0.000); 91.7% of the isolates showed a genetic similarity greater than 77% and were related to the Netherlands3-31(PMEN31) clone CC180. Several subtypes were identified, two of which showed antimicrobial resistance. Conclusion: In Colombia, the pneumococcal population of the capsular type 3 shows a continuous and homogeneous circulation relating to the clonal group ST-180.

Resumen | Introducción. El serotipo 3 de Streptococcus pneumoniae es una causa importante de neumonía, bacteriemia y meningitis. Objetivo. Establecer los genotipos circulantes de aislamientos del serotipo 3 de S. pneumoniae recuperados de muestras de enfermedad invasiva de 1994 a 2015 en Colombia. Materiales y métodos. Se analizaron 117 de los 365 aislamientos del serotipo 3 de S. pneumoniae recuperados del programa nacional de vigilancia por el laboratorio. El genotipo se estableció con electroforesis en gel de campo pulsado y la tipificación se llevó a cabo mediante secuenciación multilocus en aislamientos representativos. Resultados. La frecuencia de este serotipo aumentó de 2,7 % entre 1994 y 1998 a 9,1 % entre 2011 y 2015 (p=0,000). El 91,7 % de los aislamientos evidenció una similitud genética superior al 77 % y se relacionó con el clon CC180 de Netherlands3-31 (PMEN31). Se identificaron varios subtipos, dos de los cuales mostraron resistencia a los antimicrobianos. Conclusión. En Colombia, la población neumocócica del tipo capsular 3 tiene una circulación continua y homogénea relacionada con el grupo clonal ST-180.

Molecular epidemiology and drug resistance of Acinetobacter baumannii isolated from a regional hospital in the Brazilian Amazon region

Abstract INTRODUCTION: In this study, we report a clonal dissemination of carbapenem resistant Acinetobacter baumannii isolates due to the acquisition of blaOXA-23 in a regional hospital located in Brazilian Amazon Region. METHODS: The isolates were identified by MALDI-TOF and the carbapenemase-encoding genes were detected by multiplex-PCR. The genetic similarity was investigated by pulsed-field gel electrophoresis (PFGE). RESULTS: Only 10 (55.6%) isolates harbored the gene bla OXA-23. PFGE analysis revealed that these isolates belong to a single clone. CONCLUSIONS: This dissemination strategy indicates the need for surveillance, adoption of control procedures defined in guidelines, and the careful administration of antimicrobials should be reinforced.

Pyomelanin biosynthetic pathway in pigment-producer strains from the pandemic Acinetobacter baumannii IC-5

BACKGROUND Acinetobacter baumannii outbreaks have been associated with pandemic International Clones (ICs), but the virulence factors involved with their pathogenicity are sparsely understood. Pigment production has been linked with bacterial pathogenicity, however, this phenotype is rarely observed in A. baumannii. OBJECTIVES This study aimed to characterise the reddish-brown pigment produced by A. baumannii strains, and to determine its biosynthetic pathway by genomic approaches. METHODS Pigment characterisation and antimicrobial susceptibility were conducted by phenotypic tests. The clonal relationship was obtained by pulsed field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). The genome of an A. baumannii was obtained for characterisation of genes involved with pigment production. FINDINGS The pyomelanin was the pigment produced by A. baumannii. Strains were extensively drug resistant and belonged to the IC-5/ST79. The pyomelanin biosynthetic pathway was determined and presented a particular architecture concerning the peripheral (tyrB, phhB and hpd) and central (hmgB, hmgC and hmgR) metabolic pathway genes. The identification of a distant HmgA homologue, probably without dioxygenase activity, could explain pyomelanin production. Virulence determinants involved with adherence (csuA/BABCDE and a T5bSS-carrying genomic island), and iron uptake (basABCDEFGHIJ, bauABCDEF and barAB) were characterised. MAIN CONCLUSION There is a biosynthetic pathway compatible with the pyomelanin production observed in persistent A. baumannii IC-5 strains.

Prevalence and Risk Factors for Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae Colonization in Intensive Care Units

Active surveillance culture (ASC) can help detect hidden reservoirs, but the routine use of ASC for extended spectrum β-lactamase-producing Enterobacteriaceae is controversial in an endemic situation. We aimed to determine the prevalence and risk factors of extended spectrum β-lactamase-producing Klebsiella pneumoniae (EBSL-Kpn) colonization among intensive care unit (ICU)-admitted patients. Prospective screening of ESBL-Kpn colonization was performed for ICU-admitted patients within 48 hours for two months. A perirectal swab sample was inoculated on MacConkey agar supplemented with 2 µg/mL ceftazidime. ESBL genotype was determined by PCR-sequencing, and clonal relatedness was evaluated by pulsed-field gel electrophoresis (PFGE). The risk factors of ESBL-Kpn colonization were evaluated. The ESBL-Kpn colonization rate among the 281 patients at ICU admission was 6.4% (18/281), and bla(CTX-M-15) was detected in all isolates. ESBL producers also showed resistance to fluoroquinolone (38.9%, 7/18). All isolates had the same ESBL genotype (bla(CTX-M-15)) and a highly clustered PFGE pattern, suggesting cross-transmission without a documented outbreak. In univariate analysis, the risk factor for ESBL-Kpn colonization over the control was the length of hospital stay (odds ratio=1.062; P=0.019). Routine use of ASC could help control endemic ESBL–Kpn for ICU patients.

Genetic factors related to the widespread dissemination of ST11 extensively drug-resistant carbapenemase-producing Klebsiella pneumoniae strains within hospital / 中华医学杂志(英文版)

BACKGROUND@#Carbapenemase-producing Klebsiella pneumoniae (CP-Kp) poses distinct clinical challenges due to extensively drug resistant (XDR) phenotype, and sequence type (ST) 11 is the most dominant blaKPC-2-bearing CP-Kp clone in China. The purpose of this current retrospective study was to explore the genetic factors associated with the success of XDR CP-Kp ST11 strains circulated in the intensive care unit (ICU) of a Chinese tertiary hospital.@*METHODS@#Six ST11 XDR CP-Kp strains were identified between May and December 2014 and validated by minimum inhibitory concentration examination, polymerase chain reaction, and pyrosequencing. The six ST11 XDR CP-Kp, as well as three multi-drug resistant (MDR) and four susceptible strains, were sequenced using single-molecule real-time method. Comprehensively structural and functional analysis based on comparative genomics was performed to identify genomic characteristics of the XDR ST11 CP-Kp strains.@*RESULTS@#We found that ST11 XDR blaKPC-2-bearing CP-Kp strains isolated from inpatients spread in the ICU of the hospital. Functionally, genes associated with information storage and processing of the ST11 XDR CP-Kp strains were more abundant than those of MDR and susceptible strains, especially genes correlative with mobile genetic elements (MGEs) such as transposons and prophages. Structurally, eleven large-scale genetic regions taken for the unique genome in these ST11 XDR CP-Kp strains were identified as MGEs including transposons, integrons, prophages, genomic islands, and integrative and conjugative elements. Three of them were located on plasmids and eight on chromosomes; five of them were with antimicrobial resistance genes and eight with adaptation associated genes. Notably, a new blaKPC-2-bearing ΔΔTn1721-blaKPC-2 transposon, probably transposed and truncated from ΔTn1721-blaKPC-2 by IS903D and ISKpn8, was identified in all six ST11 XDR CP-Kp strains.@*CONCLUSION@#Our findings suggested that together with clonal spread, MGEs identified uniquely in the ST11 XDR CP-Kp strains might contribute to their formidable adaptability, which facilitated their widespread dissemination in hospital.

Brote de intoxicación alimentaria en un jardín de infantes de la provincia de Buenos Aires / Food poisoning outbreak in a kindergarten in the Province of Buenos Aires, Argentina

Resumen El 27 de noviembre de 2008 ocurrió un brote de intoxicación alimentaria asociado al consumo de salpicón de ave en un jardín de infantes de Hurlingham, provincia de Buenos Aires. Treinta y siete niños y 10 adultos presentaron síntomas gastrointestinales. Cinco niños fueron internados con signos de deshidratación, y uno de ellos requirió cuidados intensivos. Se aisló Staphylococcus aureus subsp. aureus del alimento involucrado, de 4/5 muestras de materia fecal de pacientes y de 3/5 manipuladores (nariz del manipulador 1, manos de manipuladores 2 y 3). Las cepas aisladas portaban los genes que codifican las enterotoxinas SEA y SED. Por electroforesis de campo pulsado con la enzima SmaI, los patrones de macrorrestricción presentaron 100% de similitud. La investigación oportuna del brote permitió identificar al agente causal de la intoxicación, determinar las fallas en la elaboración del alimento e implementar las medidas correctivas correspondientes.

Abstract On November 27, 2008, a foodborne disease outbreak associated with the consumption of chicken salad occurred in a kindergarten in the District of Hurlingham, Province of Buenos Aires. Thirty-seven children and 10 adults with gastrointestinal symptoms were affected. Five children were hospitalized with signs of dehydration, one of them requiring intensive care. Staphylococcus aureus subsp. aureus was isolated from the mentioned food in 4 out of 5 stool specimens from the patients, and in 3 out of 5 food handlers (nose of food handler #1, hands of food handlers #2 and 3). The isolates carried the genes coding for enterotoxins SEA and SED. The macrorestriction patterns showed 100% similarity by pulsed-field gel electrophoresis using the SmaI enzyme. A timely outbreak investigation allowed us to identify the causative agent of the food poisoning as well as the failures in food processing and to implement corrective measures.

Caracterización genética de cepas de Listeria monocytogenes aisladas durante los años 2007-2014 en Chile / Genetic characterization of Listeria monocytogenes strains isolated during 2007-2014 in Chile

Resumen Introducción: Listeria monocytogenes es un patógeno transmitido por alimentos que causa listeriosis, una enfermedad que puede presentarse como gastroenteritis febril o en una forma invasora que tiene altas tasas de mortalidad. Hasta el momento, ha sido poco estudiada la diversidad genética de cepas de L. monocytogenes aisladas desde pacientes, alimentos y fuentes ambientales en Chile. Objetivo: Caracterizar genéticamente cepas de L. monocytogenes de estos tres orígenes recibidas por el Instituto de Salud Pública de Chile (ISP) entre los años 2007 y 2014. Material y Métodos: Se seleccionaron 94 cepas de L. monocytogenes correspondientes a 94 pulsotipos diferentes identificados por electroforesis en gel de campo pulsado (PFGE), se extrajo ADN y se realizó serotipificación mediante reacción de polimerasa en cadena (RPC) y tipificación de secuencias multilocus (MLST). Resultados: El serotipo más común fue 4b (55,3%), seguido de 1/2a (25,5%), 1/2b (17%) y 1/2c (2,2%). Se identificaron 32 secuencias tipo (ST), de las cuales cuatro fueron nuevas, y las predominantes fueron ST1 (28,7%) y ST2 (13,8%). La totalidad de las cepas se agrupó en los Linajes I y II. Conclusiones: Se observó una gran variabilidad genética en las cepas de L. monocytogenes analizadas, siendo predominantes las secuencias tipo ST1 y ST2, ambas pertenecientes al Linaje I. Nuestros resultados contribuyen a conocer la estructura poblacional de este patógeno en Chile y su presencia en muestras clínicas, alimentos y el medio ambiente.

Background: Listeria monocytogenes is a foodborne pathogen that causes listeriosis, a disease that can present as febrile gastroenteritis or as an invasive form that has high mortality rates. So far, the genetic diversity of strains of L. monocytogenes isolated from patients, foods and environmental sources in Chile has been poorly studied. Aim: To characterize genetically L. monocytogenes strains received by the Institute of Public Health of Chile (ISP) between 2007 and 2014. Methods: We selected 94 strains of L. monocytogenes corresponding to 94 different pulsotypes identified by pulsed field gel electrophoresis (PFGE), DNA was extracted and serotyping was performed by polymerase chain reaction (PCR) and multilocus sequence typing (MLST). Results: The most common serotype was 4b (55.3%), followed by serotypes 1/2a (25.5%), 1/2b (17%) and 1/2c (2.2%). 32 sequence-type (ST) were identified, of which 4 were new, and the predominant ones were ST1 (28.7%) and ST2 (13.8%). All the strains of L. monocytogenes were grouped in Lineages I and II. Conclusions: A great genetic variability was observed in the strains of L. monocytogenes analyzed, being predominant the ST1 and ST2, both belonging to Lineage I. Our results contribute to know the population structure of this pathogen in Chile and its presence in clinical samples, food and the environment.

Staphylococcus aureus in tonsils of patients with recurrent tonsillitis: prevalence, susceptibility profile, and genotypic characterization

ABSTRACT Introduction: Bacterial tonsillitis is an upper respiratory tract infection that occurs primarily in children and adolescents. Staphylococcus aureus is one of the most frequent pathogens in the etiology of tonsillitis and its relevance is due to its antimicrobial resistance and persistence in the internal tissues of the tonsils. Tonsillectomy is indicated in cases of recurrent tonsillitis after several failures of antibiotic therapy. Material and methods: In this study we evaluated 123 surgically removed tonsils from patients who had history of recurrent tonsillitis. The tonsils were submitted to microbiological analysis for detection of S. aureus. The isolates were identified by PCR for femA gene. Antimicrobial susceptibility of the isolates was determined by disk diffusion tests. All isolates were submitted to PCR to detect mecA and Panton-Valentine leucocidin (PVL) genes. The genetic similarity among all isolates was determined by pulsed field gel electrophoresis. Results: Sixty-one S. aureus isolates were obtained from 50 patients (40.7%) with mean age of 11.7 years. The isolates showed high level resistance to penicillin (83.6%), 9.8% had inducible MLSb phenotype, and 18.0% were considered multidrug resistant (MDR). mecA gene was detected in two isolates and the gene coding for PVL was identified in one isolate. The genetic similarity analysis showed high diversity among the isolates. More than one genetically different isolate was identified from the same patient, and identical isolates were obtained from different patients. Conclusions: MDR isolates colonizing tonsils even without infection, demonstrate persistence of the bacterium and possibility of antimicrobial resistance dissemination and recurrence of infection. A specific clone in patients colonized by S. aureus was not demonstrated.

High rate of detection of OXA-23-producing Acinetobacter from two general hospitals in Brazil

Abstract INTRODUCTION In recent decades, the prevalence of carbapenem-resistant Acinetobacter isolates has increased, and the production of oxacillinase (OXA)-type carbapenemases is the main mechanism underlying resistance. We evaluated OXA production from 114 Acinetobacter isolates collected between March and December 2013 from different clinical specimens of patients in two hospitals (Hospital 1 [n = 61] and Hospital 2 [n = 53]) located in Niterói, Rio de Janeiro, Brazil. We also evaluated the genetic diversity of OXA-producing isolates. METHODS All the isolates were identified through the automated system Vitek II and matrix-assisted laser desorption ionization-time of flight mass spectrometry MALDI-TOF MS as belonging to the A. baumannii-A. calcoaceticuscomplex. Antimicrobial susceptibility profiles were verified through agar diffusion tests. The presence of OXA-encoding genes was confirmed by PCR. The genetic diversity of isolates positive for carbapenemase production was analyzed through pulsed-field gel electrophoresis. RESULTS There was a high rate of resistance to carbapenems in the isolates (imipenem: 96%; meropenem: 92%) from both hospitals. Moreover, a high percentage (95.6%) of OXA-23-positive isolates was observed for both hospitals, indicating that this was the main mechanism of carbapenem-resistance among the studied population. In addition, most isolates (96.5%) were positive for bla OXA-51. A high genetic diversity and a few major genotypes were found among the OXA-23-positive isolates analyzed. Only intra-hospital dissemination was observed. CONCLUSIONS The elevated dissemination of bla OXA-23-like observed among Acinetobacter isolates from both the studied hospitals highlights the need for continuous epidemiological surveillance in these institutions.

Neuroprotective effects of an Nrf2 agonist on high glucose-induced damage in HT22 cells

BACKGROUND: Oxidative stress is the hallmark of diabetic encephalopathy, which may be caused by hyperglycaemic toxicity. We aimed to discover pharmacologic targets to restore redox homeostasis. We identified the transcription factor Nrf2 as such a target. METHODS: HT22 cells were cultured in 25 or 50 mM D-glucose with various concentrations of sulforaphane (SFN) (from 1.25 to 5.0 µM). Cell viability was tested with the Cell Counting Kit-8 assay. Reactive oxygen species (ROS) production was detected with an inverted fluorescence microscope using the dichlorodihydrofluorescein-diacetate fluorescent probe. The expression of NF-E2-related factor 2 (Nrf2), haem oxygenase-1 (HO-1) and nuclear factor-κB (NF-κB) at the mRNA and protein levels was detected by reverse transcription quantitative polymerase chain reaction and western blotting. RESULT: We found that a high glucose concentration (50 mM) increased the generation of ROS, downregulated the expression of Nrf2/HO-1 and upregulated the expression of NF-κB. Moreover, HT22 cell viability significantly decreased after culture in high-glucose medium for 24, 48 and 72 h, whereas the activation of the Nrf2/HO-1 pathway using a pharmacological Nrf2 activator abrogated this high-glucose-induced toxicity. CONCLUSION: This study suggests that the activation of the Nrf2-ARE signalling pathway might be a therapeutic target for the treatment of diabetic encephalopathy.

Molecular Epidemiology and Mechanisms of 43 Low-Level Linezolid-Resistant Enterococcus faecalis Strains in Chongqing, China

BACKGROUND: Enterococcus faecalis strains with low-level resistance to linezolid (an oxazolidinone antibiotic) have become common. No large-scale study has examined the underlying mechanisms in linezolid-resistant E. faecalis (LRE) strains. We investigated these mechanisms and molecular characteristics in Chongqing, China. METHODS: A total of 1,120 non-duplicated E. faecalis strains collected from August 2014 to June 2017 underwent drug susceptibility testing. LRE strains were screened for optrA, cfr, and mutations in the 23S rRNA and ribosomal proteins L3 and L4 by PCR amplification and sequencing. Multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were used for epidemiological analysis. RESULTS: All 43 low-level LRE strains (minimum inhibitory concentration: 8–16 mg/L) harbored optrA; cfr and 23S rRNA mutations were not detected. Novel mutations in the ribosomal proteins L3 and L4—one deletion (Q103del) and four substitutions (S113L, T35A, I98V, and N79D)—were identified. Novel amino acid substitutions at positions E60K, G197D, and T285P of the OptrA protein were observed. MLST revealed 20 types of LRE strains; the most common type was ST16 (32.6%). PFGE showed 14 strains of ST16 with unique banding patterns. Eight novel sequence types (ST823 to ST830) and one allele (gki95) were identified for the first time in China. CONCLUSIONS: optrA plays an important role in linezolid resistance and may serve as a marker for resistance screening. Since the L3 and L4 mutations did not simultaneously occur in the same strain, they play a negligible role in linezolid resistance. Epidemiological investigation suggested that the LRE cases were sporadic.

A large outbreak of Salmonella enterica serovar Thompson infections associated with chocolate cake in Busan, Korea / 한국역학회지

OBJECTIVES: This study aimed to reveal the epidemiologic characteristics of the outbreak of gastroenteritis caused by Salmonella enterica serovar Thompson in Busan Metropolitan City and to identify points for improvement to prevent of food-borne disease outbreak.METHODS: This was a case-control study. The control group comprised asymptomatic students in the same classes of the cases. The presence or absence of symptoms, ingestion of each food provided by school meal service, and commonly ingested foods in addition to those foods in meal service were investigated. Moreover, specimens collected from rectal swab, preserved foods, and environmental surface were tested.RESULTS: Of the 6,092 subjects, 1,111 (1,083 students, 22 school personnel, and 6 foodservice employees) were included in the case group; this corresponded to an 18.4% attack rate. Symptoms included diarrhea (n=1,051, 94.6%), abdominal pain (n=931, 83.8%), febrile sensation (n=502, 45.2%), and vomiting (n=275, 24.8%). The epidemic curves of each 10 schools were unimodal. Investigation of food intake showed a significantly high odds ratio for chocolate cake in 5 out of the 10 schools. Laboratory test detected Salmonella enterica serovar Thompson both in rectal swab specimens of 9 schools and in collected preserved chocolate cakes of 9 schools. Pulsed-field gel electrophoresis test result showed that Salmonella enterica seorvar Thompson isolated from human and foods were the same.CONCLUSIONS: The source of infection for the Salmonella enterica serovar Thompson outbreak in the 10 schools of Busan Metropolitan City is chocolate cake. Traceback investigation for origin of contaminated food in food-borne disease outbreak and safety control during food production should be more enhanced.

Comparison of Characteristics of Streptococcus dysgalactiae subsp. equisimilis Isolates Causing Repetitive vs Single Infections

No study has described Streptococcus dysgalactiae subsp. equisimilis (SDSE) isolates that cause repetitive infections (recurrence and reinfection). We compared the microbiological characteristics of SDSE causing repetitive infections with those causing single infections. Three patients with invasive infections were identified based on their medical records, and multiple SDSE isolates were collected at intervals over three weeks, using a laboratory repository. Isolates from 12 patients with single-episode infections served as controls. Six isolates were collected from three patients with first and second episodes of infection. All isolates causing either repetitive or single-episode infection were subjected to emm typing, multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and random amplified polymorphic DNA (RAPD) analyses. Amplification of five virulence genes (sicG, prtF1, prtF2, lmb, and cbp), biofilm formation (BF), and cell invasion abilities (CIAs) were measured as virulent phenotypes. We observed close genetic similarities in the data obtained by emm typing, MLST, PFGE, and RAPD in four isolates from two patients, suggesting recurrence, whereas two isolates from one patient indicated genetic differences in these data, suggesting re-infection. The presence of the five virulence genes and the BF and CIA measurements appeared not to contribute to repetitive infections, compared with isolates causing single-episode infection. In conclusion, clinicians encountering patients with repetitive infections should be aware of both possibilities: recurrence with closely related strains and reinfection with different strains.

A large outbreak of Salmonella enterica serovar Thompson infections associated with chocolate cake in Busan, Korea / 한국역학회지

OBJECTIVES: This study aimed to reveal the epidemiologic characteristics of the outbreak of gastroenteritis caused by Salmonella enterica serovar Thompson in Busan Metropolitan City and to identify points for improvement to prevent of food-borne disease outbreak. METHODS: This was a case-control study. The control group comprised asymptomatic students in the same classes of the cases. The presence or absence of symptoms, ingestion of each food provided by school meal service, and commonly ingested foods in addition to those foods in meal service were investigated. Moreover, specimens collected from rectal swab, preserved foods, and environmental surface were tested. RESULTS: Of the 6,092 subjects, 1,111 (1,083 students, 22 school personnel, and 6 foodservice employees) were included in the case group; this corresponded to an 18.4% attack rate. Symptoms included diarrhea (n=1,051, 94.6%), abdominal pain (n=931, 83.8%), febrile sensation (n=502, 45.2%), and vomiting (n=275, 24.8%). The epidemic curves of each 10 schools were unimodal. Investigation of food intake showed a significantly high odds ratio for chocolate cake in 5 out of the 10 schools. Laboratory test detected Salmonella enterica serovar Thompson both in rectal swab specimens of 9 schools and in collected preserved chocolate cakes of 9 schools. Pulsed-field gel electrophoresis test result showed that Salmonella enterica seorvar Thompson isolated from human and foods were the same. CONCLUSIONS: The source of infection for the Salmonella enterica serovar Thompson outbreak in the 10 schools of Busan Metropolitan City is chocolate cake. Traceback investigation for origin of contaminated food in food-borne disease outbreak and safety control during food production should be more enhanced.