Staphylococcus aureus resistentes a la meticilina portadores del gen mecC: ¿un problema emergente? / Methicillin-resistant Staphylococcus aureus carrying the mecC gene: an emerging problem?

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Emergence of cfr-Mediated Linezolid Resistance in a Methicillin-Resistant Staphylococcus aureus Epidemic Clone Isolated from Patients with Cystic Fibrosis.

Resistance to linezolid (LZD) in methicillin-resistant Staphylococcus aureus (MRSA) isolates from patients with cystic fibrosis (CF) is due mainly to ribosomal mutations. We report on four CF patients with LZD-resistant MRSA bronchopulmonary infections by strains carrying the cfr gene. Strains from one patient also harbored the G2576U mutation (23S rRNA) and the G139R substitution (L3 protein). All strains belonged to the epidemic clone ST125 MRSA IVc. Our results support the monitoring of LZD resistance emergence in CF and non-CF MRSA isolates.

Endemic and epidemic Acinetobacter baumannii clones: a twelve-year study in a tertiary care hospital.

BACKGROUND: Nosocomial outbreaks of multidrug-resistant Acinetobacter baumannii are of worldwide concern. Using pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and multiple locus variable number tandem repeat sequence (VNTR) analysis (MLVA), the present work examines the genetic diversity of the endemic and epidemic A. baumannii clones isolated in a single hospital over a twelve-year period. RESULTS: PFGE analysis of 405 A. baumannii-calcoaceticus complex isolates detected 15 A. baumannii endemic/epidemic PFGE types (EE1 to EE15) that grouped into five clusters: EE1-EE8, EE9, EE10, EE11 and EE12-EE15. The MLST sequence type (ST) distributions were: international clone II (ST-2) 60%, international clone III (ST-3) 26.7%, ST-15 6.7%, and ST-80 6.7%. MLVA-8Orsay returned 17 allelic profiles. The large (L) VNTR marker profiles were fully concordant with the detected STs, and concordant with 14 up to 15 PFGE types. Imipenem resistance was detected in five PFGE types; the prevalence of the bla OXA-58-like and bla OXA-40-like genes was 60% and 40% respectively. CONCLUSIONS: PFGE proved to be a vital tool for analysis of the temporal and spatial distribution of the clones. MLST and the VNTR L-markers grouped the isolates into clonal clusters. The wide diversity of MLVA small (S)-markers, however, did not permit clustering. The present results demonstrate the persistence of several endemic PFGE types in the hospital, the involvement of some of them in outbreaks, and the inter hospital transmission of extensively drug-resistant ST-15 and ST-80.

An analysis of the association between genotype and antimicrobial resistance in methicillin-resistant Staphylococcus aureus clinical isolates / Análisis de la asociación entre genotipos y resistencia a múltiples antimicrobianos en aislados de Staphylococcus aureus resistente a meticilina

Genotyping methods are useful resources for the surveillance, detection, prevention and control of multidrug-resistant nosocomial agents, such as methicillin-resistant Staphylococcus aureus (MRSA). An understanding of the association between genotype and antibiotic susceptibility in MRSA clones may be useful in the surveillance of MRSA and to avoid inappropriate treatment future resistance. We genotyped MRSA clinical isolates from the Extremadura region of Spain using pulsed field electrophoresis (PFGE) and analyzed the spectrum of antibiotic susceptibility for each isolate to determine whether resistance is associated with specific genotypes. PFGE revealed six major genotypes: E8a (25%), E7b (17%), E7a (12%), E8B (8%), E10 (6%), and E20 (4%). Isolates with the genotypes E8a and E10 exhibit higher resistance ratios for levofloxacin than isolates with the other major pulsotypes. Similar results were obtained for isolates with the E20 pulsotype with respect to mupirocin. Although we identified no vancomycin-, tigecycline-, linezolid- or daptomycin-resistant strains, we observed significant differences in the mean MIC values obtained for some of these drugs among the major genotypes. Specifically, isolates with the E7b, E8b, and E20 genotypes have significantly higher MICs of tigecycline, vancomycin and linezolid, respectively, than the most sensitive pulsotypes. Isolates with the E8b profile also exhibit a significantly higher rate of reduced vancomycin susceptibility (RVS) (i.e., MIC between 1 and 2 mg/L) than clones with the E10 and E8a profiles. In conclusion, we report associations between genotype and antibiotic sensitivity that should be considered in programs for monitoring and controlling MRSA in health care settings (AU)

Los métodos de genotipaje son un recurso útil para la vigilancia, detención, prevención y control de agentes nosocomiales con multirresistencia antibiótica, como es Staphylococcus aureus resistente a meticilina (SARM). Nuestro grupo lleva a cabo el genotipaje mediante Electroforesis en Campo Pulsado (PFGE) de cepas SARM productoras de infección en la región de Extremadura (España), y realiza un estudio de asociación de los clones obtenidos, con respecto a la sensibilidad antibiótica mostrada por las cepas genotipadas, con el objetivo de conocer si existen resistencias que puedan asociarse específicamente a genotipos concretos. PFGE revela la existencia de 6 genotipos mayoritarios: E8a (25%), E7b (17%), E7a (12%), E8b (8%), E10 (6%), E20 (4%). A través del test Exacto de Fisher determinamos que los genotipos E8a y E10 se inclinan hacia ratios de resistencia mayores para levofloxacino en comparación a los mostrados por otros pulsotipos mayoritarios. De manera análoga ocurre para el pulsotipo E20 con mupirocina. Aunque no se encuentran cepas resistentes para vancomicina, tigeciclina, linezolid y daptomicina, encontramos en los tres primeros, diferencias significativas en el valor medio de CMI obtenido en los diferentes genotipos mayoritarios. Concretamente E7b, E8b y E20 presentan CMI significativamente más altas con respecto a tigeciclina, vancomicina y linezolid, respectivamente, en relación a los pulsotipos más sensibles. Además el perfil E8b muestra un mayor número de cepas con sensibilidad disminuida a vancomicina (SDV) (CMI entre 1 y 2 mg/L) que los clones E10 y E8a, de manera significativa. Creemos que esta información puede resultar útil en la vigilancia de la sensibilidad antibiótica de SARM en nuestro medio, para evitar tratamientos inadecuados y/o futuras resistencias (AU)

New patterns of methicillin-resistant Staphylococcus aureus (MRSA) clones, community-associated MRSA genotypes behave like healthcare-associated MRSA genotypes within hospitals, Argentina.

Methicillin-resistant Staphylococcus aureus (MRSA) burden is increasing worldwide in hospitals [healthcare-associated (HA)-MRSA] and in communities [community-associated (CA)-MRSA]. However, the impact of CA-MRSA within hospitals remains limited, particularly in Latin America. A countrywide representative survey of S. aureus infections was performed in Argentina by analyzing 591 clinical isolates from 66 hospitals in a prospective cross-sectional, multicenter study (Nov-2009). This work involved healthcare-onset infections-(HAHO, >48 hospitalization hours) and community-onset (CO) infections [including both, infections (HACO) in patients with healthcare-associated risk-factors (HRFs) and infections (CACO) in those without HRFs]. MRSA strains were genetically typed as CA-MRSA and HA-MRSA genotypes (CA-MRSAG and HA-MRSAG) by SCCmec- and spa-typing, PFGE, MLST and virulence genes profile by PCR. Considering all isolates, 63% were from CO-infections and 55% were MRSA [39% CA-MRSAG and 16% HA-MRSAG]. A significantly higher MRSA proportion among CO- than HAHO-S. aureus infections was detected (58% vs 49%); mainly in children (62% vs 43%). The CA-MRSAG/HA-MRSAG have accounted for 16%/33% of HAHO-, 39%/13% of HACO- and 60.5%/0% of CACO-infections. Regarding the epidemiological associations identified in multivariate models for patients with healthcare-onset CA-MRSAG infections, CA-MRSAG behave like HA-MRSAG within hospitals but children were the highest risk group for healthcare-onset CA-MRSAG infections. Most CA-MRSAG belonged to two major clones: PFGE-type N-ST30-SCCmecIVc-t019-PVL(+) and PFGE-type I-ST5-IV-SCCmecIVa-t311-PVL(+) (45% each). The ST5-IV-PVL(+)/ST30-IV-PVL(+) clones have caused 31%/33% of all infections, 20%/4% of HAHO-, 43%/23% of HACO- and 35%/60% of CACO- infections, with significant differences by age groups (children/adults) and geographical regions. Importantly, an isolate belonging to USA300-0114-(ST8-SCCmecIVa-spat008-PVL(+)-ACME(+)) was detected for the first time in Argentina. Most of HA-MRSAG (66%) were related to the Cordobes/Chilean clone-(PFGE-type A-ST5-SCCmecI-t149) causing 18% of all infections (47% of HAHO- and 13% of HACO-infections). Results strongly suggest that the CA-MRSA clone ST5-IV-PVL(+) has begun to spread within hospitals, replacing the traditional Cordobes/Chilean-HA-MRSA clone ST5-I-PVL(-), mainly in children. Importantly, a growing MRSA reservoir in the community was associated with spreading of two CA-MRSA clones: ST5-IV-PVL(+), mainly in children with HRFs, and ST30-IV-PVL(+) in adults without HRFs. This is the first nationwide study in Argentina providing information about the molecular and clinical epidemiology of CA-MRSA, particularly within hospitals, which is essential for designing effective control measures in this country and worldwide.

Situación actual de la infección por Staphylococcus aureus resistente a meticilina en Extremadura: sensibilidad, clonalidad, y protagonismo de la adquisición extrahospitalaria / State of infection caused by methicillin-resistant Staphylococcus aureus (MRSA) in Extremadura: susceptibility, clonality and role of community-associated MRSA

La correcta vigilancia y control de la infección por Staphylococcus aureus resistente a meticilina (SARM) pasa por el conocimiento actualizado de las propiedades específicas que la caracterizan en cada lugar. El objetivo de este trabajo es describir las características actuales de la infección por SARM en Extremadura. Durante el año 2010 se recogieron 309 SARM, procedentes de muestras clínicas en nuestra comunidad. A cada uno de los aislados se le realizó un estudio de sensibilidad que engloba 17 antibióticos, ensayados mediante tarjeta AST-588 Vitek 2® y método E-test. Además se genotipa mediante Electroforesis en Campo Pulsado (PFGE) una muestra de 100 cepas, escogidas por muestreo aleatorio estratificado. Se obtienen los siguientes resultados: la prevalencia de SARM en Extremadura es 20,2%. Don Benito-Villanueva es el área con mayor prevalencia y una de las de mayor incidencia. Mérida presenta la situación más favorable, con ratios relativamente bajos de prevalencia e incidencia. La adquisición extrahospitalaria alcanza el 44% en la región, mostrando claro predominio en las áreas de menor población (Navalmoral de la Mata y Coria). El patrón de multirresistencia más frecuente es tobramicina-levofloxacino-eritromicina (44%), seguido de tobramicina-eritromicina-clindamicina (20%). No se obtienen cepas resistentes a linezolid, daptomicina o tigeciclina, sin embargo el 42% presentan sensibilidad disminuida a vancomicina. El análisis por PFGE revela la existencia de 27 genotipos, con 3 genotipos mayoritarios: E8a (25%), E7b (17%) y E7a (12%). El estudio estadístico post-hoc, no revela diferencias significativas en la distribución de genotipos entre las diferentes áreas, pero si algunas tendencias que deben tenerse en consideración (AU)

The correct surveillance and control of infection caused by methicillin-resistant Staphylococcus aureus (MRSA) needs of update knowledge of its specific properties in each place. Our study aims to describe the current characteristics of infection due to MRSA in Extremadura. During 2010, 309 MRSA were collected from clinical samples in our region. A susceptibility test that included 17 antibiotics tested by AST -588 card Vitek 2 ® and E -test method was performed on all isolates. A sample of 100 strains, selected by stratified random sampling, were genotyped by pulsed field electrophoresis (PFGE). The prevalence of MRSA in Extremadura was 20.2%. Don Benito-Villanueva area showed the most prevalence and a higher incidence. Merida reported the most favourable situation, with a relatively low ratios of prevalence and incidence. The community acquired reached 44 % in the region, showing predominantly in less populated areas (Navalmoral and Coria). The most common multiresistant pattern was tobramycin-levofloxacin-erythromycin (44%), followed tobramycin-erythromycin-clindamycin (20%). No linezolid, daptomycin and tigecycline resistant strains were observed, but 42 % of the MRSA strains showed decreased susceptibility vancomycin (DSV). PFGE analysis reported 27 genotypes, with 3 major genotypes: E8a (25%), E7b (17%) and E7a (12%). The post-hoc statistical analysis did not reveal significant differences in the distribution of genotypes between different areas. However it revealed some trends that should be considered (AU)

Molecular epidemiology of community-associated methicillin-resistant Staphylococcus aureus in Spain: 2004-12.

OBJECTIVES: In Spain, despite the high rates of healthcare-associated methicillin-resistant Staphylococcus aureus (MRSA), the incidence of community-associated (CA) MRSA seems to be low on the basis of a small number of studies. We analysed the evolution of CA-MRSA in Spain from 2004 to 2012, and identified the clonal lineages and population structure. METHODS: The study included 8326 MRSA strains. Susceptibility to 18 antimicrobials was determined. Isolates were tested for the presence of mecA, Panton-Valentine leucocidin (PVL) and the arginine catabolic mobile element (ACME) by PCR, and typed by staphylococcal cassette chromosome mec, PFGE, spa, multilocus sequence typing and agr. RESULTS: Among the 8326 isolates, 246 (2.9%) were CA-MRSA. We identified genotypically 226 PVL-positive CA-MRSA isolates (88% agr type I, 10.2% agr type III and 1.8% agr type II) and 20 PVL-negative CA-MRSA isolates (all agr type I) from children and adults (82.1% from wounds) from 13 different geographical areas. A significant increase in the rates of CA-MRSA was observed when comparing 2004-07 (0.43%) with 2008-12 (5.44%). Resistance rates were as follows: only ß-lactams, 84.5%; erythromycin, 12.8%; tetracycline, 8.8%; clindamycin, 4.9%; ciprofloxacin, 3.1%; fusidic acid, 2.0%; others, 0.4%; and multiresistant, 6.2% (six isolates USA300). The strains belonged to the PVL-positive clones ST8-IVc (69.9%), ST8-IVa-ACME-positive (USA300, 8.9%), ST8-IVa-ACME-negative (0.8%), ST30-IVc (4.5%), ST80-IVc (2.0%), ST5-IVc (1.2%) and others (ST59, ST72, ST88, ST642, ST1472 and ST1829; 4.5%) and to the PVL-negative ST398-V (8.1%). CONCLUSIONS: We confirm an increase in CA-MRSA in Spain, the predominance of the ST8-IVc clone, the emergence of the USA300 clone, a high genetic diversity among PVL-positive CA-MRSA isolates and the recent emergence of the pig-associated ST398-V clone.

Methicillin-resistant Staphylococcus aureus carrying the mecC gene: emergence in Spain and report of a fatal case of bacteraemia.

OBJECTIVES: Methicillin-resistant Staphylococcus aureus (MRSA) strains carrying the mecC gene have been reported from humans and animals from several European countries, but never from Spain. We describe the first isolates of mecC-positive MRSA of human origin collected in Spain and report a fatal case of bacteraemia. METHODS: Isolates were tested for phenotypic resistance using cefoxitin, tested for the mecA/mecC genes and toxin genes by PCR, and typed by staphylococcal cassette chromosome mec (SCCmec), PFGE, spa, multilocus sequence typing and agr. RESULTS: During 2008-13 five MRSA isolates showing resistance to cefoxitin and carrying the mecC gene were recovered at one hospital in Spain. In a review of 5505 S. aureus strains received at the Spanish National Reference Centre for Staphylococci from the same period, we found two additional mecC-positive isolates. The isolates were recovered from blood (two), wounds (two), joint fluid (one), urine (one) and a nasal swab (one). All MRSA were mecA negative, presented SCCmecXI, belonged to agr group III and to clonal complex 130, and were negative for the production of the toxin genes tst1, eta, etb, etd and Panton-Valentine leucocidin. Six isolates belonged to spa type t843 (ST130 and ST1945, where ST stands for sequence type) and one to spa type t6220 (ST1945). One patient with mecC-positive MRSA sepsis died in the emergency department. CONCLUSIONS: We confirm the presence of MRSA carrying the mecC gene in Spain, the ability of this livestock-associated MRSA to cause severe infections in humans and the need to perform culture-based susceptibility testing methods in order to detect these emerging strains.

Draft Genome Sequence of Strain SA_ST125_MupR of Methicillin-Resistant Staphylococcus aureus ST125, a Major Clone in Spain.

Here, we report the draft genome sequence of a methicillin-resistant Staphylococcus aureus (MRSA) strain with high-level mupirocin resistance (SA_ST125_MupR), isolated from a patient with recurrent bacteremia. This strain belonged to sequence type ST125, which was responsible for more than 50% of the health care-associated infections caused by MRSA in Spain.

Outbreak of multiresistant OXA-24- and OXA-51-producing Acinetobacter baumannii in an internal medicine ward.

Here we describe the clinical, microbiological, epidemiological, and molecular characterization of an outbreak of multidrug-resistant Acinetobacter baumannii (MRAB) involving 5 patients admitted to the internal medicine ward of our hospital. Over a 6-week period, 5 MRAB isolates were recovered from 5 patients, including 1 with fatal meningitis, 3 with skin and soft tissue infections, and 1 with respiratory colonization. One sample obtained during environmental monitoring in the ward was A. baumannii-positive. According to the pulsed-field gel electrophoresis typing results, the strains isolated from all patients and the environmental sample belonged to a single clone, identified as ST79 by multilocus sequence typing. The blaOXA-24 and blaOXA-51 carbapenemases were detected in all isolates. Four patients died, but only the death of the meningitis patient was probably related to the A. baumannii infection. The infection source was probably the hands of the healthcare workers because the outbreak strain was isolated from the surface of a serum container. The results of the present study revealed the importance of strict adherence to control measures by all healthcare workers because the consequences of noncompliance can be very serious.

Emergence of OXA-48-producing Klebsiella pneumoniae and the novel carbapenemases OXA-244 and OXA-245 in Spain.

OBJECTIVES: To describe the molecular and population-level characterization of a selected group of OXA-48-like-producing Klebsiella pneumoniae isolates collected in Spain between January 2011 and May 2012. METHODS: During the study period, 151 OXA-48-like-producing K. pneumoniae isolates were collected from 10 hospitals in six different Spanish regions. From these, a representative sample of 21 isolates that caused hospital outbreaks and single infections was selected for further in-depth analysis. Molecular epidemiology was investigated using PFGE and multilocus sequence typing (MLST). Resistance genes were characterized by PCR and sequencing. Plasmids carrying bla(OXA-48-like) were studied by PFGE with S1 nuclease digestion. RESULTS: All 21 isolates had ertapenem MICs ≥ 1 mg/L, but 47.6% remained susceptible to imipenem and meropenem; bla(OXA-48) was identified in 19 isolates (90.5%) and the novel bla(OXA-244) and bla(OXA-245) genes were detected in 1 isolate each. With one exception, all isolates that contained bla(OXA-48-like) also contained bla(CTX-M-15). PFGE typing revealed six clusters comprising isolates that belonged to MLST types ST11, ST16, ST392, ST405, ST437 and ST663, respectively. Two main clusters were identified: PFGE cluster 1 (12 isolates, belonging either to ST405 or ST663, from seven hospitals), and PFGE cluster 2 (4 ST16 isolates from two hospitals). Six of seven donor isolates conjugated successfully; bla(OXA-48-like) (but not bla(CTX-M-15)) was carried on ≈ 60 kb Inc L/M plasmids. CONCLUSIONS: Multidrug-resistant K. pneumoniae producing OXA-48-like carbapenemase are emerging as important pathogens in Spain due to intra- and inter-hospital, clonal and non-clonal dissemination.

Epidemiology of the Acinetobacter-derived cephalosporinase, carbapenem-hydrolysing oxacillinase and metallo-ß-lactamase genes, and of common insertion sequences, in epidemic clones of Acinetobacter baumannii from Spain.

OBJECTIVES: To study the distribution, diversity and activity of Acinetobacter-derived cephalosporinase (ADC)-, carbapenem-hydrolysing oxacillinase (CHO)- and metallo-ß-lactamase (MBL)-encoding genes, and of the most common insertion sequences (ISs), in the genome of nosocomial, epidemic, multidrug-resistant Acinetobacter baumannii (MDRAB) clones from Spain. METHODS: The studied population included 59 MDRAB strains previously genotyped by PFGE and multilocus sequence typing. The search for the ADC (bla(ADC)), CHO (bla(OXA-51-like), bla(OXA-23-like), bla(OXA-40-like) and bla(OXA-58-like)) and MBL (bla(IMP), bla(VIM), bla(SIM-1), bla(GIM-1), bla(SPM-1) and bla(NDM-1)) genes, and for the ISs (ISAba1, ISAba2, ISAba3, ISAba4 and IS18) was done by PCR assays. The phenotypic presence of MBL enzymes was examined using imipenem/imipenem + EDTA strips. RESULTS: The most prevalent IS, ISAba1 (93.2%), was detected upstream of bla(ADC) and bla(OXA-51-like). These genes showed ample diversity (10 and 8 alleles, respectively). Four ADC sequences (ADC-1-like(P240S), ADC-2-like(N260H/T264N), ADC-11-like(Q163K) and ADC-11-like(G342R)) are described here for the first time. bla(OXA-58-like) was carried by 20.3% of strains, in association with ISAba2, ISAba3 or IS18. bla(OXA-40-like) was the most prevalent acquired CHO gene (57.6%), and was associated with none of the studied ISs. Neither bla(OXA-23-like) nor ISAba4 was detected in any strain. Some 67.8% of strains with MBL activity showed no corresponding gene in PCR; these results were more common in strains with a highly active CHO, such as OXA-40. CONCLUSIONS: All the studied genes and their related ISs showed a clonal distribution. Imipenem resistance was probably provided by OXA-40 for the most part, while MBL- and OXA-23-encoding genes were absent in the studied population.

Outbreak of multidrug-resistant CTX-M-15-producing Enterobacter cloacae in a neonatal intensive care unit.

Newborns are rarely infected by extended-spectrum ß-lactamase (ESBL)-producing members of the Enterobacteriaceae. In a neonatal intensive care unit, 14 newborns were infected or colonized by CTX-M-15-producing Enterobacter cloacae. All seven infected patients had underlying medical conditions, and five of them were treated successfully with meropenem, whilst one untreated patient died. Paediatric infections caused by multidrug-resistant ESBL-producing Enterobacter cloacae constitute a critical clinical and epidemiological issue.

Antimicrobial resistance and molecular epidemiology of Panton-Valentine leukocidin-positive community-associated methicillin-resistant Staphylococcus aureus from Gran Canaria (Canary Islands, Spain).

Among 3967 Staphylococcus aureus recovered from a Gran Canaria hospital (2003-2010), 28 strains were Panton-Valentine leukocidin-positive community-associated methicillin-resistant Staphylococcus aureus and were included in this study. Most isolates (89.3%) caused skin and skin-structure infections. Isolates belonging to clonal complex (CC)8 (ST8 and ST931; USA300) prevailed (82.1%). Among these, 5 (21.7%) were resistant to at least 3 antimicrobial classes.

Spread of epidemic MRSA-ST5-IV clone encoding PVL as a major cause of community onset staphylococcal infections in Argentinean children.

BACKGROUND: Community-associated methicillin-resistant Staphylococcus aureus-(CA-MRSA) strains have emerged in Argentina. We investigated the clinical and molecular evolution of community-onset MRSA infections (CO-MRSA) in children of Córdoba, Argentina, 2005-2008. Additionally, data from 2007 were compared with the epidemiology of these infections in other regions of the country. METHODOLOGY/PRINCIPAL FINDINGS: Two datasets were used: i) lab-based prospective surveillance of CA-MRSA isolates from 3 Córdoba pediatric hospitals-(CBAH1-H3) in 2007-2008 (compared to previously published data of 2005) and ii) a sampling of CO-MRSA from a study involving both, healthcare-associated community-onset-(HACO) infections in children with risk-factors for healthcare-associated infections-(HRFs), and CA-MRSA infections in patients without HRFs detected in multiple centers of Argentina in 2007. Molecular typing was performed on the CA-MRSA-(n: 99) isolates from the CBAH1-H3-dataset and on the HACO-MRSA-(n: 51) and CA-MRSA-(n: 213) isolates from other regions. Between 2005-2008, the annual proportion of CA-MRSA/CA-S. aureus in Córdoba hospitals increased from 25% to 49%, P<0.01. Total CA-MRSA infections increased 3.6 fold-(5.1 to 18.6 cases/100,000 annual-visits, P<0.0001), associated with an important increase of invasive CA-MRSA infections-(8.5 fold). In all regions analyzed, a single genotype prevailed in both CA-MRSA (82%) and HACO-MRSA(57%), which showed pulsed-field-gel electrophoresis-(PFGE)-type-"I", sequence-type-5-(ST5), SCCmec-type-IVa, spa-t311, and was positive for PVL. The second clone, pulsotype-N/ST30/CC30/SCCmecIVc/t019/PVL(+), accounted for 11.5% of total CA-MRSA infections. Importantly, the first 4 isolates of Argentina belonging to South American-USA300 clone-(USA300/ST8/CC8/SCCmecIVc/t008/PVL(+)/ACME(-)) were detected. We also demonstrated that a HA-MRSA clone-(pulsotype-C/ST100/CC5) caused 2% and 10% of CA-MRSA and HACO-MRSA infections respectively and was associated with a SCCmec type closely related to SCCmecIV(2B&5). CONCLUSIONS/SIGNIFICANCE: The dissemination of epidemic MRSA clone, ST5-IV-PVL(+) was the main cause of increasing staphylococcal community-onset infections in Argentinean children (2003-2008), conversely to other countries. The predominance of this clone, which has capacity to express the h-VISA phenotype, in healthcare-associated community-onset cases suggests that it has infiltrated into hospital-settings.

Nosocomial outbreak of VIM-1-producing Klebsiella pneumoniae isolates of multilocus sequence type 15: molecular basis, clinical risk factors, and outcome.

We study the epidemiology, molecular basis, clinical risk factors, and outcome involved in the clonal dissemination of VIM-1-producing Klebsiella pneumoniae isolates in the hospital setting. All patients infected/colonized by carbapenem-nonsusceptible K. pneumoniae (CNSKP) in 2009 were included. Molecular epidemiology was studied by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Antibiotic resistance genes were analyzed by PCR and sequencing. Plasmids were studied by PFGE with S1 nuclease digestion and for incompatibility group by a PCR-based replicon typing scheme. Risk factors associated with CNSKP colonization/infection were assessed by an observational case-control study. All 55 patients studied were infected (n = 28) or colonized (n = 27) by VIM-1-producing K. pneumoniae. All but one acquired isolates of a single clone (PFGE cluster 1 [C1], sequence type 15 [ST15]), while another clone (PFGE C2, ST340) was detected in four patients. C1 isolates also produced the new extended-spectrum ß-lactamase SHV-134. bla(VIM-1) was carried in a class 1 integron and an untypeable plasmid of ∼50 bp. The number of days that the patient received mechanical ventilation, the use of parenteral nutrition, previous treatment with linezolid, and treatment with extended-spectrum cephalosporins for more than 7 days were detected to be independent risk factors for CNSKP acquisition. The VIM-1-producing K. pneumoniae ST15 clone has a high capacity to spread among intensive care unit patients with severe underlying conditions. A high rate of associated mortality and great difficulty in controlling the spread of this clone, without permanent behavioral changes in the personnel, were observed.

Heterogeneous vancomycin-intermediate susceptibility in a community-associated methicillin-resistant Staphylococcus aureus epidemic clone, in a case of Infective Endocarditis in Argentina.

BACKGROUND: Community-Associated Methicillin Resistant Staphylococcus aureus (CA-MRSA) has traditionally been related to skin and soft tissue infections in healthy young patients. However, it has now emerged as responsible for severe infections worldwide, for which vancomycin is one of the mainstays of treatment. Infective endocarditis (IE) due to CA-MRSA with heterogeneous vancomycin-intermediate susceptibility-(h-VISA) has been recently reported, associated to an epidemic USA 300 CA-MRSA clone. CASE PRESENTATION: We describe the occurrence of h-VISA phenotype in a case of IE caused by a strain belonging to an epidemic CA-MRSA clone, distinct from USA300, for the first time in Argentina. The isolate h-VISA (SaB2) was recovered from a patient with persistent bacteraemia after a 7-day therapy with vancomycin, which evolved to fatal case of IE complicated with brain abscesses. The initial isolate-(SaB1) was fully vancomycin susceptible (VSSA). Although MRSA SaB2 was vancomycin susceptible (≤ 2 µg/ml) by MIC (agar and broth dilution, E-test and VITEK 2), a slight increase of MIC values between SaB1 and SaB2 isolates was detected by the four MIC methods, particularly for teicoplanin. Moreover, Sab2 was classified as h-VISA by three different screening methods [MHA5T-screening agar, Macromethod-E-test-(MET) and by GRD E-test] and confirmed by population analysis profile-(PAP). In addition, a significant increase in cell-wall thickness was revealed for SaB2 by electron microscopy. Molecular typing showed that both strains, SaB1 and SaB2, belonged to ST5 lineage, carried SCCmecIV, lacked Panton-Valentine leukocidin-(PVL) genes and had indistinguishable PFGE patterns (subtype I2), thereby confirming their isogenic nature. In addition, they were clonally related to the epidemic CA-MRSA clone (pulsotype I) detected in our country. CONCLUSIONS: This report demonstrates the ability of this epidemic CA-MRSA clone, disseminated in some regions of Argentina, to produce severe and rapidly fatal infections such as IE, in addition to its ability to acquire low-level vancomycin resistance; for these reasons, it constitutes a new challenge for the Healthcare System of this country.