Identification of hypermucoviscous Klebsiella pneumoniae K1, K2, K54 and K57 capsular serotypes by Raman spectroscopy.

Antimicrobial resistance poses a significant challenge in modern medicine, affecting public health. Klebsiella pneumoniae infections compound this issue due to their broad range of infections and the emergence of multiple antibiotic resistance mechanisms. Efficient detection of its capsular serotypes is crucial for immediate patient treatment, epidemiological tracking and outbreak containment. Current methods have limitations that can delay interventions and increase the risk of morbidity and mortality. Raman spectroscopy is a promising alternative to identify capsular serotypes in hypermucoviscous K. pneumoniae isolates. It provides rapid and in situ measurements with minimal sample preparation. Moreover, its combination with machine learning tools demonstrates high accuracy and reproducibility. This study analyzed the viability of combining Raman spectroscopy with one-dimensional convolutional neural networks (1-D CNN) to classify four capsular serotypes of hypermucoviscous K. pneumoniae: K1, K2, K54 and K57. Our approach involved identifying the most relevant Raman features for classification to prevent overfitting in the training models. Simplifying the dataset to essential information maintains accuracy and reduces computational costs and training time. Capsular serotypes were classified with 96 % accuracy using less than 30 Raman features out of 2400 contained in each spectrum. To validate our methodology, we expanded the dataset to include both hypermucoviscous and non-mucoid isolates and distinguished between them. This resulted in an accuracy rate of 94 %. The results obtained have significant potential for practical healthcare applications, especially for enabling the prompt prescription of the appropriate antibiotic treatment against infections.

Covert dissemination of pLVPK-like virulence plasmid in ST29-K54 Klebsiella pneumoniae: emergence of low virulence phenotype strains.

This study aimed to explore the epidemic, clinical characteristics, and molecular and virulence attributes of Klebsiella pneumoniae serotype K54 (K54-Kp). A retrospective study was conducted on 328 strains of Klebsiella pneumoniae screened in a Chinese hospital from January 2016 to December 2019. The virulence genes and antibiotic resistance genes (ARGs) were detected by PCR, and a drug sensitivity test was adopted to detect drug resistance. Multilocus sequence typing (MLST) and PFGE were performed to determine the clonal correlation between isolates. Biofilm formation assay, serum complement-mediated killing, and Galleria mellonella infection were used to characterize the virulence potential. Our results showed that thirty strains of K54-Kp were screened from 328 strains of bacteria, with an annual detection rate of 2.29%. K54-Kp had a high resistance rate to antibiotics commonly used in the clinic, and patients with hepatobiliary diseases were prone to K54-Kp infection. MLST typing showed 10 sequence typing, mainly ST29 (11/30), which concentrated in the B2 cluster. K54-Kp primarily carried virulence genes of aerobactin, silS, allS, wcaG, wabG, and mrkD, among which the terW gene was closely related to ST29 (p<0.05). The strains infected by the bloodstream had strong biofilm formation ability (p<0.05). Most strains were sensitive to serum. Still, the virulence of pLVPK-like virulence plasmid in ST29-K54 Klebsiella pneumoniae was lower than that of ST11 type and NTUH-K2044 in the Galleria mellonella model. Therefore, these findings supply a foundation to roundly comprehend K54-Kp, and clinicians should strengthen supervision and attention.

Serotyping and molecular profiles of virulence-associated genes among Klebsiella pneumoniae isolates from teaching hospitals of Ardabil, Iran: A cross-sectional study.

Background and Aims: Klebsiella pneumoniae is a Gram-negative bacterium that colonized various organs. This bacterium is associated with different community-acquired and hospital-acquired infections. The present study aims to assess the capsular serotypes and frequency of virulence-associated genes in K. pneumoniae isolates from teaching hospitals in Ardabil, Iran. Methods: From October 1, 2019, to November 31, 2021, different clinical samples were collected and K. pneumoniae isolates were diagnosed using conventional biochemical tests. The final identification of K. pneumoniae was performed through the polymerase chain reaction (PCR) method using a specific primer targeting the khe gene. The PCR method was employed to confirm the presence of virulence-associated genes and aerobactin, and the main capsular serotypes based on the specific primers. Results: Of all 100 K. pneumoniae isolates, 4% and 2% were typeable with K5 and K2 primers, respectively. In addition, entB (94%), fimH (91%), and wcaG (87%) had the highest frequency among the virulence-associated genes. 24% of K. pneumoniae isolates harbored the entB-wcaG-fimH genes simultaneously. Moreover, 50% of capsular serotype 5 harbored the ybts-mrkD-entB-wcaG-fimH genes simultaneously. Conclusion: The findings revealed that 6% of all K. pneumoniae isolates were typeable, distributed in the two serotypes K5 and K2. Most K. pneumoniae isolates were positive for multiple types of virulence genes. Identifying bacterial virulence genes aids in molecular detection, assay development, and therapeutic pathways.

Serotype replacement and an increase in non-encapsulated isolates among community-acquired infections of Streptococcus pneumoniae during post-vaccine era in Japan.

Objectives: It is feared that the serotype replacement of Streptococcus pneumoniae occurred by the introduction of pneumococcal vaccines as periodical inoculation leads to reduced efficacy of the approved vaccines and altered antimicrobial susceptibility. Methods: We determined serotypes of 351 S. pneumoniae isolates collected at a commercial clinical laboratory in Hokkaido prefecture, Japan, from December 2018 to February 2019 by using the polymerase chain reaction procedure of the US Centers for Disease Control and Prevention. Antimicrobial susceptibility and resistance gene profiles were also examined. Results: Vaccine coverage rates were 7.9% for 13-valent conjugate vaccine, and 32.5% for 23-valent polysaccharide vaccine, respectively. Non-typable strains were 19.7%. cpsA-positive isolates (group I), and null capsule clade (NCC)1, NCC2 and NCC3 (group II) comprised 31.3%, 28.4%, 32.8%, and 7.5% of the 69 non-typable strains, respectively. No penicillin-resistant/intermediate isolates were found; however, serotypes 35B and 15A/F showed low susceptibility to ß-lactams. Only five strains (1.4%) were levofloxacin-resistant, and all were from the older persons, and three strains were serotype 35B. Conclusion: The progression of serotype replacement in non-invasive pneumococcal infections has occurred during the post-vaccine era in Japan, and non-encapsulated isolates, such as NCC, have increased. Antimicrobial susceptibility is not worsened.

Study on Virulence Genes, Drug Resistance and Molecular Epidemiology of Klebsiella pneumoniae with High Virulence in Inner Mongolia, China.

Objective: The purpose of this study was to analyse the clinical, microbiological and molecular epidemiological characteristics of patients with pyogenic liver abscess (PLA) caused by Klebsiella pneumoniae (KPN) in Inner Mongolia, China. Methods: The KPN isolates from 78 KPN-PLA cases admitted to a tertiary teaching hospital in Baotou, Inner Mongolia, from 2016 to 2019 were studied systematically and described comprehensively. The virulence factors, drug resistance and sequence types of KPN in different samples were identified by a wire-drawing test, polymerase chain reaction, a drug susceptibility test and multi-site sequence typing. Results: There were more male than female KPN-PLA patients (P<0.05). The mortality rate was 2.5%, and KPN-PLA was significantly associated with diabetes mellitus (P<0.05). Most of the KPN isolates in the puncture fluid of patients with KPN-PLA were hypervirulent KPN (HvKP). The positive rate of the KPN-PLA specimens was higher than that of the blood and urine specimens. The KPN isolates of the urine specimens had higher drug resistance than the other two (P<0.05). The hypermucoviscous KPN, aerobic actin (aero) (+), K1 and K2 serotypes accounted for 80.8%, 89.7%, 56.4% and 26.9%, respectively. In addition to ironB (3.8%), the detection rates of virulence factors rmpA, irp2, entB, iucD, aero, wcaG, iutA, kfu, ybtA, iron, fimH and mrkD were higher (69.2%-100.0%). The positive rate of KPN isolates of the KPN-PLA puncture fluid was higher than that of the blood and urine samples (P<0.05). In addition, ST23 was found to be the dominant ST (32.1%) of KPN-PLA in the Baotou region. Conclusion: In the KPN-PLA specimens, the KPN isolates were more virulent than those in the blood and urine specimens, and a carbapenem-resistant HvKP strain emerged. This research will help improve the understanding of HvKP and provide useful suggestions for KPN-PLA treatments.

Characterization of hypervirulent Klebsiella pneumoniae isolates in Belgium.

Hypervirulent Klebsiella pneumoniae (hvKp) raised concern worldwide. We studied 22 hvKp clinical invasive isolates referred to the Belgian national reference laboratory between 2014 and 2020. Sixty-four percent of the isolates expressed K2 capsular serotype and belonged to 7 different MLST lineages, while 32% expressed K1 (all belonging to ST23) and were associated with liver abscesses. Primary extra-hepatic infections were reported in 36% and sepsis for 95% of the patients with 30% of deaths. Improved clinical and microbiological diagnostics are required as hvKp may represent an underestimated cause of community-acquired invasive infections in Belgium.

Identifying large-scale recombination and capsular switching events in Streptococcus agalactiae strains causing disease in adults in the UK between 2014 and 2015.

Cases of invasive group B streptococcal infection in the adult UK population have steadily increased over recent years, with the most common serotypes being V, III and Ia, but less is known of the genetic background of these strains. We have carried out in-depth analysis of the whole-genome sequences of 193 clinically important group B Streptococcus (GBS) isolates (184 were from invasive infection, 8 were from non-invasive infection and 1 had no information on isolation site) isolated from adults and submitted to the National Reference Laboratory at the UK Health Security Agency between January 2014 and December 2015. We have determined that capsular serotypes III (26.9%), Ia (26.4%) and V (15.0%) were most commonly identified, with slight differences in gender and age distribution. Most isolates (n=182) grouped to five clonal complexes (CCs), CC1, CC8/CC10, CC17, CC19 and CC23, with common associations between specific serotypes and virulence genes. Additionally, we have identified large recombination events mediating potential capsular switching events between sequence type (ST)1 serotype V and serotypes Ib (n=2 isolates), II (n=2 isolates) and VI (n=2 isolates); between ST19 serotype III and serotype V (n=5 isolates); and between CC17 serotype III and serotype IV (n=1 isolate). The high genetic diversity of disease-causing isolates and multiple recombination events reported in this study highlight the need for routine surveillance of the circulating disease-causing GBS strains. This information is crucial to better understand the global spread of GBS serotypes and genotypes, and will form the baseline information for any future GBS vaccine research in the UK and worldwide.

Group B Streptococcus (GBS) Invasive Infections in Women of Childbearing Age, France, 2012-2020: GBS CC-17 Hypervirulence in Intrapartum Infections.

Group B Streptococcus (GBS) is the leading cause of neonatal infections and an important pathogen in pregnancy. However, the features of pregnancy-associated infections are poorly reported. We analyzed 336 cases of GBS invasive infections in women aged 18-50 years, including 242 (72.0%) pregnancy-associated infections. In pregnancy, most cases were intra-amniotic infections (55.8%), occurred preterm (61.3%), and were associated with obstetrical and neonatal complications (81.7%). The GBS clone CC-17 (18.8% of the cases) was overrepresented intrapartum (35.2%; odds ratio, 5.1 [95% confidence interval, 1.6-19.3]). This work highlights the burden of GBS and of the CC-17 clone infections during pregnancy.

Community-acquired Haemophilus influenzae meningitis in adults.

BACKGROUND: Haemophilus influenzae is an uncommon cause of meningitis in adults. METHODS: We analyzed episodes of community-acquired H. influenzae meningitis in adults included in a prospective nationwide cohort study in the Netherlands. RESULTS: From 2006 to July 2018, 82 of 2272 (4%) bacterial meningitis episodes were caused by H. influenzae (mean annual incidence 0.5 patients per 1,000,000). Median age was 61 years (IQR 46-68), and 48 episodes (59%) occurred in woman. Predisposing factors were otitis and/or sinusitis in 33 of 76 patients (49%), immunocompromising conditions in 19 of 75 patients (25%) and cerebrospinal fluid leak in 13 of 79 patients (17%). Serotyping showed 63 of 80 isolates (79%) were non-typeable (NTHi). Three patients (4%) died and 14 patients (17%) had an unfavorable outcome (Glasgow Outcome Scale score < 5 at discharge). Pneumonia (odds ratio [OR] 5.8, 95% confidence interval [95%CI] 1.1-30.8), presence of immunocompromising conditions (OR 6.0, 95%CI 1.5-24.4), and seizures on admission (OR 10.7, 95%CI 1.6-72.8) were associated with an unfavorable outcome, while NTHi was associated with a favorable outcome (OR 5.6, 95%CI 1.6-19.5). CONCLUSION: H. influenzae is an uncommon cause of adult bacterial meningitis patients mainly causing disease in those with predisposing factors, such as CSF leakage, ENT infections, and immunocompromised state. In adult patients the majority of H. influenzae meningitis is caused by non-typeable strains.

Relationship between intrapartum antibiotic prophylaxis and group B streptococcal colonization dynamics in Japanese mother-neonate pairs.

INTRODUCTION: In Japan, universal screening for group B streptococcal (GBS) colonization in pregnant women and intrapartum antibiotic prophylaxis (IAP) are recommended to prevent neonatal GBS infection. However, the dynamics of GBS colonization in Japanese mother/neonate pairs have not been adequately studied. METHODS: A prospective cohort study was conducted from July 2018 to March 2019. Rectovaginal samples were collected from pregnant women (33-37 gestation weeks) once. In neonates, nasopharyngeal and rectal samples were collected at three time points: after birth, 1 week after birth, and 1 month after birth. All samples were analyzed for GBS using real-time PCR testing and culture methods. Capsular typing was performed for all GBS isolates and GBS-positive samples using real-time PCR testing. RESULTS: The overall maternal and neonatal GBS-positivity rates were 22.7% (57/251) and 8.8% (22/251), respectively. IAP for GBS-positive mothers (96.5%) was highly administered. Eleven (19.3%) neonates born to GBS-positive mothers were GBS-positive, which was significantly higher than the 11 (5.7%) neonates born to GBS-negative mothers. The rate of GBS-positivity in neonates increased with an increased number of GBS colonies in mothers. More neonates were GBS-positive 1 month after birth than 1 week after birth, and there was a higher rate of GBS-positive rectal swabs than nasopharyngeal swabs. Capsular types of GBS that were isolated from each mother and neonate pair were the same, namely, Ib, III, V, and VI. CONCLUSIONS: These findings indicate that the efficacy of IAP in preventing GBS transmission to neonates might be limited to within a few weeks after birth.

Serotyping of Klebsiella pneumoniae and Its Relation with Capsule-Associated Virulence Genes, Antimicrobial Resistance Pattern, and Clinical Infections: A Descriptive Study in Medical Practice.

OBJECTIVE: Klebsiella pneumoniae, one of the clinical superbugs, causes diverse infections because of its variable capsular antigens. This study focused on K. pneumoniae and aimed to assess any correlation between capsular serotype, capsule-associated virulence genes, and evaluate its resistance to conventional antibiotics in order to gain insight into any regional differences. MATERIALS AND METHODS: A total of 61 K. pneumoniae collected from various clinical specimens were confirmed genotypically. Clinical and demographic data for all patients were reviewed. All isolates were subjected to antimicrobial susceptibility tests. Capsular serotyping and capsule-associated virulence genes were studied using the molecular method. RESULTS: All typeable isolates were typed into K5, K20, and K54 serotypes, and among them, K54 was observed to be predominant. The most common capsule-associated virulence genes comprised uge (93.4%), ycfM (91.8%), and wabG (88.5%), while wcaG (29.5%) and rmpA (21.3%) were noted at much lower prevalence rates. The gene wcaG was significantly associated with K54 positive isolates (p = 0.001), while rmpA was associated with K20 positive isolates (p = 0.01). CONCLUSION: Serotype K54 had a high frequency in isolates collected from patients with pulmonary diseases, while serotype K20 was associated with burn patients. Carbapenems and levofloxacin were the best therapeutic options for the treatment of infections with serotypes K20 and K54.

Development of risk factor-based scoring system for detection of hypervirulent Klebsiella pneumoniae bloodstream infections.

BACKGROUND: Hypervirulent Klebsiella pneumoniae (HVKp) infections have distinct clinical manifestations from classical K. pneumoniae infections. The hallmark of HVKp infections are liver abscess formation and metastatic infections. Due to the severe sequelae of these complications, method to identify patients at-risk of HVKp infections should be developed. RESULTS: A retrospective cohort study of 222 patients with K. pneumoniae bloodstream infections (BSIs) was performed. Patient demographics, clinical manifestations, and bacterial characteristics were investigated. Ten cases of liver abscesses were identified. Characteristics such as community-onset BSIs, hypermucoviscosity phenotype, and capsular serotype K1 were identified as risk factors for HVKp infections. A scoring system was developed based on the risk factors. The area under the receiver operating characteristic curve for the scoring system was 0.90. A score of ≥ 2 points provided sensitivity and specificity of 0.70 and 0.94, respectively. CONCLUSIONS: Simple scoring system was developed for the diagnosis of HVKp infections. The system allows early identification of patients with K. pneumoniae BSIs in whom hypervirulent infections should be evaluated. Prospective evaluation is expected.

Clinical and microbiological characteristics of hypervirulent Klebsiella pneumoniae (hvKp) in a hospital from North China.

INTRODUCTION: The clinical and molecular characteristics of hypervirulent Klebsiella pneumoniae (hvKp) in various provinces of China have been reported, however, there have been few reports in Hebei Province, North China. METHODOLOGY: The hvKp was identified by PCR amplification of hypervirulence-related genes, the hypermucoviscous phenotype was determined by the "string test", the drug susceptibility analysis was performed using the VITEK® 2 Compact Bacterial Identification and Monitoring System. Logistic regression was used to identify risk factors for hvKp infection. The molecular epidemiological characteristics of the strains were analyzed by pulsed-field gel electrophoresis (PFGE), and the capsular serotype of hvKp strain was detected by PCR. RESULTS: Overall, 52.21% (59/113) of K. pneumoniae isolates were hvKp, and the ratios of patients with older ages or a higher PMN cell count among hvKp infection were higher than those among classical Klebsiella pneumoniae (cKp) infection. hvKp are more susceptible to antibacterial drugs than cKp, and one ESBLs-producing hvKp strain was detected. The main capsular serotype of hvKp were K2, K57 and K1. PFGE indicated that the 59 strains of hvKp could be classified into 51 PFGE band types, forming 6 PFGE clusters. CONCLUSIONS: In this study, the detection rate of hvKp was 52.21% (59/113) identified by virulence genes. People with older ages or a higher PMN cell count are more likely to gain hvKp infection. ESBLs-producing hvKp is emerging, indicating the importance of epidemiologic surveillance and clinical awareness of this pathogen in this region.

Whole-Genome-Sequencing characterization of bloodstream infection-causing hypervirulent Klebsiella pneumoniae of capsular serotype K2 and ST374.

Hypervirulent K. pneumoniae variants (hvKP) have been increasingly reported worldwide, causing metastasis of severe infections such as liver abscesses and bacteremia. The capsular serotype K2 hvKP strains show diverse multi-locus sequence types (MLSTs), but with limited genetics and virulence information. In this study, we report a hypermucoviscous K. pneumoniae strain, RJF293, isolated from a human bloodstream sample in a Chinese hospital. It caused a metastatic infection and fatal septic shock in a critical patient. The microbiological features and genetic background were investigated with multiple approaches. The Strain RJF293 was determined to be multilocis sequence type (ST) 374 and serotype K2, displayed a median lethal dose (LD50) of 1.5 × 102 CFU in BALB/c mice and was as virulent as the ST23 K1 serotype hvKP strain NTUH-K2044 in a mouse lethality assay. Whole genome sequencing revealed that the RJF293 genome codes for 32 putative virulence factors and exhibits a unique presence/absence pattern in comparison to the other 105 completely sequenced K. pneumoniae genomes. Whole genome SNP-based phylogenetic analysis revealed that strain RJF293 formed a single clade, distant from those containing either ST66 or ST86 hvKP. Compared to the other sequenced hvKP chromosomes, RJF293 contains several strain-variable regions, including one prophage, one ICEKp1 family integrative and conjugative element and six large genomic islands. The sequencing of the first complete genome of an ST374 K2 hvKP clinical strain should reinforce our understanding of the epidemiology and virulence mechanisms of this bloodstream infection-causing hvKP with clinical significance.

Streptococcus infantis, Streptococcus mitis, and Streptococcus oralis Strains With Highly Similar cps5 Loci and Antigenic Relatedness to Serotype 5 Pneumococci.

Streptococcus pneumoniae is a highly impactful bacterial pathogen on a global scale. The principal pneumococcal virulence factor and target of effective vaccines is its polysaccharide capsule, of which there are many structurally distinct forms. Here, we describe four distinct strains of three Mitis group commensal species (Streptococcus infantis, Streptococcus mitis, and Streptococcus oralis) recovered from upper respiratory tract specimens from adults in Kenya and the United States that were PCR-positive for the pneumococcal serotype 5 specific gene, wzy5. For each of the four strains, the 15 genes comprising the capsular polysaccharide biosynthetic gene cluster (cps5) shared the same order found in serotype 5 pneumococci, and each of the serotype 5-specific genes from the serotype 5 pneumococcal reference strain shared 76-99% sequence identity with the non-pneumococcal counterparts. Double-diffusion experiments demonstrated specific reactivity of the non-pneumococcal strains with pneumococcal serotype 5 typing sera. Antiserum raised against S. mitis strain KE67013 specifically reacted with serotype 5 pneumococci for a positive Quellung reaction and stimulated serotype 5 specific opsonophagocytic killing of pneumococci. Four additional commensal strains, identified using PCR serotyping assays on pharyngeal specimens, revealed loci highly homologous to those of pneumococci of serotypes 12F, 15A, 18C, and 33F. These data, in particular the species and strain diversity shown for serotype 5, highlight the existence of a broad non-pneumococcal species reservoir in the upper respiratory tract for the expression of capsular polysaccharides that are structurally related or identical to those corresponding to epidemiologically significant serotypes. Very little is known about the genetic and antigenic capsular diversity among the vast array of commensal streptococcal strains that represent multiple diverse species. The discovery of serotype 5 strains within three different commensal species suggests that extensive capsular serologic overlap exists between pneumococci and other members of the diverse Mitis group. These findings may have implications for our current understanding of naturally acquired immunity to S. pneumoniae and pneumococcal serotype distributions in different global regions. Further characterization of commensal strains carrying homologs of serotype-specific genes previously thought to be specific for pneumococci of known serotypes may shed light on the evolution of these important loci.

Microbiological characterisation of Klebsiella pneumoniae isolates causing bloodstream infections from five tertiary hospitals in Beijing, China.

OBJECTIVES: Klebsiella pneumoniae is prevalent in China. Little is known about the microbiological characteristics of clinical K. pneumoniae isolates causing bloodstream infections (BSIs). METHODS: BSI-causing K. pneumoniae (BSI-Kpn) were collected from five tertiary-care hospitals in Beijing. Genetic relatedness was analysed by PFGE, antimicrobial susceptibility was determined by agar dilution, and sequence types (STs) were evaluated by MLST. Hypermucoviscosity (HV) phenotype was identified by positive string test. Carbapenemase, capsular serotype and HV-associated genes were detected by PCR. RESULTS: A total of 219 non-duplicate BSI-Kpn were collected from December 2013 to December 2014 and were categorised into 203 types (strains) with unique PFGE patterns. Among 203 BSI-Kpn, 105 STs were identified. Overall, ST11 and ST23 were the predominant clones (14 strains each; 6.9%), followed by ST412 (n=13), ST37 (n=9), ST65 (n=7), ST15 (n=6), ST86 (n=6), ST592 (n=5) and ST29 (n=4). There were 74 STs containing only a single strain. Approximately 8.4% (17/203) of the strains exhibited carbapenem resistance, most producing KPC carbapenemase. The majority (75.9%; 154/203) of isolates were associated with non-K1/K2/K5/K20/K54/K57 serotypes. Only 16.3% (33/203) of the strains had K1/K2 serotypes. A total of 66 (32.5%) of the BSI-Kpn strains exhibited a HV phenotype. rmpA was a predominant factor in determining a HV phenotype. CONCLUSIONS: The majority of BSI-Kpn strains exhibited high genetic diversity and low resistance to commonly used antimicrobials. The specific capsular serotype and HV phenotype were not major features of BSI-Kpn strains in China.

Virulence genes and homology analysis of Klebsiella pneumoniae associated with pyogenic liver abscess / 临床检验杂志

Objective To investigate the distribution of hypervirulent capsular serotypes and virulence genes of Klebsiella pneumoniae associated with pyogenic liver abscess(PLA),and analyze the homology of strains.Methods Twelve strains of liver abscess-related Klebsiella pneumoniae were isolated in Wuxi Second People's Hospital during January 2016 and August 2017.Among them,five were also detected in blood samples.All the strains were performed the viscous thread test,and the hypervirulent capsular serotypes and main virulence genes were detected by PCR.The homology of the strains was analyzed by the multilocus sequence types(MLST) and pulsed-field gel electrophoresis(PFGE).Results The positive rate of the viscous thread test for 12 strains of liver abscess-related Klebsiella pneumoniae was 75％.Three kinds of hypervirulent capsular serotypes,including K1 (6/12,50％),K54(1/12,8.3％) and K57(5/12,41.7％),were detected.The positive rates of virulence genes,such as wcaG,rmpA,ureA,fimH,mrkD,uge,Aer and iroNB,were all 100％,while that of iucB was 83.3％.The cf29a gene was not found,and the magA,allS and kfuBC genes were only detected in K1 serotype strains.MLST found that ST23(4/12,33.3％) and ST25(3/12,25％) were main sequence types,and then were ST412(2/12,16.7％),ST1660(1/12,8.3％),ST1049(1/t2,8.3％) and ST11 (1/12,8.3％).PFGE showed that 12 strains of Klebsiella pneumoniae were divided into 8 types,and that only 3 strains of K1 serotype belong to the same clonotype.Conclusion All the isolated liver abscess-related Klebsiella pneumoniae strains are highly virulent.ST23 and ST25 are main sequence types,and ST1049 is first reported.PFGE results show genetic diversity,and Kl-type Klebsiella pneumoniae has a certain epidemic tendency.

Galleria mellonella infection model for evaluating the virulence of Klebsiella pneumoniae / 中华微生物学和免疫学杂志

Objective@#To establish a Galleria mellonella model of liver abscess-related Klebsiella pneumoniae (K.pneumoniae) infection and to evaluate its feasibility for virulence detection.@*Methods@#Twelve liver abscess-related K. pneumoniae strains were collected in Wuxi No.2 People′s Hospital from January 2016 to December 2017. Twenty K. pneumoniae strains isolated from sputum and urine samples were used as classic strains. All isolates were analyzed by String test. Common capsular serotypes (K1, K2, K5, K16, K20, K54 and K57) of highly virulent K. pneumoniae strains were detected by PCR. Virulence test was performed to measure 80% lethal doses (LD80) of different serotypes in the same time period and the lethal time for 80% of larvae (LT80) at the same concentration.@*Results@#The 12 strains of liver abscess-related K. pneumoniae belonged to five serotypes, which were K1 (41.7%, 5/12), K2 (8.3%, 1/12), K5 (8.3%, 1/12), K20 (8.3%, 1/12) and K57 (33.4%, 4/12). High-virulence serotypes were not detected in the classic group. The positive rates of String test in the liver abscess group and the classic group were 75% and 10% (2/20), respectively. Results of the virulence test showed that when the concentration ranged from 1×105 CFU/ml to 1×108 CFU/ml, the lethal effects of different strains on Galleria mellonella larvae were in a concentration dependent manner. Twelve hours after infection, the numbers of dead larvae in K1 and K57 serotype groups were significantly higher than those in K2, K5, K20 and classic groups. The LD80 values of the liver abscess group at 96 hours after infection were as follows: 1×106 CFU/ml (K1, K57) and 1×107 CFU/ml (K2, K5, K20).@*Conclusion@#The liver abscess-related K. pneumoniae isolates are all highly virulent strains. The virulence of K. pneumoniae can be detected at 12 hours after infection of Galleria mellonella.

Effects of Intrapartum Antibiotic Prophylaxis on Neonatal Acquisition of Group B Streptococci.

OBJECTIVES: To assess the incidence of colonization with group B streptococci (GBS) among neonates as influenced by maternal GBS carriage and intrapartum antibiotic prophylaxis (IAP). STUDY DESIGN: Between October 2014 and May 2015, nasopharyngeal and rectal swab samples were collected from 730 neonates at 1 week and 1 month after birth. GBS and capsular serotype were identified by real-time polymerase chain reaction and by culture. IAP at delivery was determined retrospectively from hospital records. RESULTS: Sixty-four neonates (8.8%) were GBS-positive by real-time polymerase chain reaction and culture. Among neonates born to mothers who were GBS carriers (n = 107), 94.4% (101/107) had maternal IAP; 19.6% nonetheless were GBS-positive, compared with 6.5% of neonates born to noncarrier mothers (P <.01). Among neonates born to mothers receiving IAP, more were positive only at 1 month of age than at both 1 week and 1 month. The frequency of GBS in neonates born to mothers receiving IAP was significantly lower than that in neonates born to mothers not receiving IAP (P <.05). Capsular serotypes V (25%) and III (23.4%) were common, followed by Ib (15.6%), Ia (14.1%), II (7.8%), IV (6.3%), nontypeable (4.7%), and VI and VIII (each 1.6%). CONCLUSIONS: Delayed colonization with GBS occurs in infants born to GBS carrier mothers receiving IAP. GBS should be considered in all infants at 1 month after birth with signs of infection.

Recent advances in the understanding and management of Klebsiella pneumoniae.

Klebsiella pneumoniae, a gram-negative bacillus of the Enterobacteriaceae family, is a component of the normal human microbiota and a common cause of community- and healthcare-associated infections. The increasing prevalence of antimicrobial resistance among K. pneumoniae isolates, particularly among those causing healthcare-associated infections, is an important public health concern. Infections caused by these multidrug-resistant organisms, for which safe and effective antimicrobial therapy options are extremely limited, are associated with poor outcomes for patients. The optimal approach to the treatment of infections caused by these multidrug-resistant strains remains undefined, and treatment decisions for an individual patient should be based on a number of organism- (for example, minimum inhibitory concentration) and patient-specific (for example, site of infection) factors. The emergence of pandrug-resistant strains of K. pneumoniae highlights the critical need for consistent implementation of effective strategies for prevention of transmission and infection and for the development of new antimicrobials with activity against these emerging pathogens.