Beneath the surface: a case report on nonencapsulated Streptococcus pneumoniae-associated invasive disease in an immunocompromised patient.

Background: Streptococcus pneumoniae, a prominent human pathogen linked to various systemic diseases, includes non-typeable pneumococci marked by the absence of a detectable capsule. However, the majority of invasive infections are attributed to encapsulated strains. This case report details the first documented instance of invasive disease caused by non-typeable S. pneumoniae in Argentina since 2017. Case Presentation: A 19-year-old woman presented with haemorrhagic injuries attributed to chronic oral mucosa irritation. Subsequent hospitalization revealed bone marrow aplasia, leading to antibiotic, antifungal, antiviral, and immunosuppressive treatments, culminating in her discharge. Two weeks later, she was readmitted with sepsis related to a respiratory focus, exhibiting a negative COVID-PCR test. After ten days, ICU admission revealed additional infections: positive COVID-PCR test, fungal sinusitis, and S. pneumoniae bacteremia. Targeted treatments led to improvement, and the patient was subsequently discharged. S pneumoniae characterization: Verification of the capsule's absence utilized traditional methods such as the Quellung reaction, transmission electron microscopy, molecular assays, and Whole Genome Sequencing (WGS). The isolate, identified as ST18335, displayed genetic features and antibiotic resistance patterns, concordant between WGS and the agar dilution method. It demonstrated non-susceptibility to penicillin and cefotaxime, based on meningitis breakpoints, as well as meropenem and cotrimoxazole. Conclusion: This case underscores the clinical significance of non-typeable S. pneumoniae, emphasizing the necessity for a comprehensive approach to identification and characterization. The findings contribute to ongoing discussions regarding the challenges posed by non-typeable strains in vaccine development, understanding clinical impacts, and addressing antibiotic resistance. As the pneumococcal epidemiological landscape evolves, this case serves as a valuable addition to the evolving knowledge surrounding non-typeable S. pneumoniae, highlighting the continued need for surveillance and research in infectious diseases.

Antimicrobial resistance of Streptococcus pneumoniae from invasive pneumococcal diseases in Latin American countries: a systematic review and meta-analysis.

Background: Invasive pneumococcal disease has declined since pneumococcal conjugate vaccine introduction in Latin America and the Caribbean (LAC). However, serotype distribution and antimicrobial resistance patterns have changed. Methods: We conducted a systematic review to evaluate the frequency of antimicrobial resistance of Streptococcus pneumoniae from invasive disease in LAC. Articles published between 1 January 2000, and 27 December 2022, with no language restriction, were searched in major databases and gray literature. Pairs of reviewers independently selected extracted data and assessed the risk of bias in the studies. The quality of antimicrobial resistance (AMR) studies was evaluated according to WHO recommendations (PROSPERO CRD42023392097). Results: From 8,600 records identified, 103 studies were included, with 49,660 positive samples of S. pneumoniae for AMR analysis processed. Most studies were from Brazil (29.1%) and Argentina (18.4%), were cross-sectional (57.3%), reported data on AMR from IPD cases (52.4%), and were classified as moderate risk of bias (50.5%). Resistance to penicillin was 21.7% (95%IC 18.7-25.0, I2: 95.9), and for ceftriaxone/cefotaxime it was 4.7% (95%IC 3.2-6.9, I2: 96.1). The highest resistance for both penicillin and ceftriaxone/cefotaxime was in the age group of 0 to 5 years (32.1% [95%IC 28.2-36.4, I2: 87.7], and 9.7% [95%IC 5.9-15.6, I2: 96.9] respectively). The most frequent serotypes associated with resistance were 14 for penicillin and 19A for ceftriaxone/cefotaxime. Conclusion: Approximately one-quarter of invasive pneumococcal disease isolates in Latin America and the Caribbean displayed penicillin resistance, with higher rates in young children. Ongoing surveillance is essential to monitor serotype evolution and antimicrobial resistance patterns following pneumococcal conjugate vaccine introduction.

Different evolution of S. aureus methicillin-resistant and methicillin-susceptible infections, Argentina.

Staphylococcus aureus-(SA) is widespread among healthcare-associated-(HA) and the community-associated-(CA) infections. However, the contributions of MRSA and MSSA to the SA overall burden remain unclear. In a nationally-representative-survey conducted in Argentina, 668 SA clinical isolates from 61 hospitals were examined in a prospective, cross-sectional, multicenter study in April 2015. The study aimed to analyze MRSA molecular epidemiology, estimate overall SA infection incidence (MSSA, MRSA, and genotypes) in community-onset (CO: HACO, Healthcare-Associated-CO and CACO, Community-Associated-CO) and healthcare-onset (HO: HAHO, Healthcare-associated-HO) infections, stratified by age groups. Additionally temporal evolution was estimated by comparing this study's (2015) incidence values with a previous study (2009) in the same region. Erythromycin-resistant-MSSA and all MRSA strains were genetically typed. The SA total-infections (TI) overall-incidence was 49.1/100,000 monthly-visits, 25.1 and 24.0 for MRSA and MSSA respectively (P = 0.5889), in April 2015. In adults with invasive-infections (INVI), MSSA was 15.7 and MRSA was 11.8 (P = 0.0288), 1.3-fold higher. HA SA infections, both MSSA and MRSA, surpassed CA infections by over threefold. During 2009-2015, there was a significant 23.4 % increase in the SA infections overall-incidence, mainly driven by MSSA, notably a 54.2 % increase in INVI among adults, while MRSA infection rates remained stable. The MSSA rise was accompanied by increased antimicrobial resistance, particularly to erythromycin, linked to MSSA-CC398-t1451-ermT + -IEC+-pvl- emergence. The SA-infections rise was primarily attributed to community-onset-infections (37.3 % and 62.4 % increase for TI and INVI, respectively), particularly HACO-MSSA and HACO-MRSA in adults, as well as CACO-MSSA. The main CA-MRSA-PFGE-typeN-ST30-SCCmecIVc-PVL+/- clone along with other clones (USA300-ST8-IV-LV-PVL+/-, PFGE-typeDD-ST97-IV- PVL-) added to rather than replaced CA-MRSA-PFGE-typeI-ST5-SCCmecIVa-PVL+/- clone in HA invasive-infections. They also displaced clone HA-MRSA-PFGE-typeA-ST5-SCCmecI, mainly in HAHO infections. The overall-burden of SA infections is rising in Argentina, driven primarily by community-onset MSSA, particularly in adults, linked to increased erythromycin-resistance and MSSA-CC398-t1451-ermT + -IEC+-pvl- emergence. Novel knowledge and transmission-control strategies are required for MSSA.

Emergence of optrA-mediated linezolid resistance in clinical isolates of Enterococcus faecalis from Argentina.

OBJECTIVES: The aim of this study was to characterize the first 14 optrA-carrying linezolid resistant E. faecalis clinical isolates recovered in seven Argentinian hospitals between 2016 and 2021. The epidemiology of optrA-carrying isolates and the optrA genetic context were determined. METHODS: The isolates were phenotypically and genotypically characterized. Susceptibility to 13 antimicrobial agents was performed; clonal relationship was assessed by pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Data provided by the whole-genome sequencing were used for identification of sequence types, antimicrobial resistance genes, optrA variants, phylogenetic tree, and mobile genetic elements responsible to the dissemination of these strains. RESULTS: All the optrA-carrying E. faecalis isolates were multidrug-resistant and harboured several antimicrobial resistance genes. They carried three optrA variants and belonged to different lineages; however, three of them belonged to the hyperepidemic CC16. Mobile genetic elements were detected in all the isolates. The analysis of the optrA flanking region suggests the plasmidic localization in most of the isolates. CONCLUSIONS: To the best of our knowledge, this is the first report of optrA-mediated linezolid resistance in Argentina. The emergence and dissemination of the optrA genes in clinical E. faecalis isolates are of concern and highlights the importance of initiating the antimicrobial surveillance of Enterococcus spp. under a One Health strategy.

First Isolation of Methicillin-Resistant Livestock-Associated Staphylococcus aureus CC398 and CC1 in Intensive Pig Production Farms in Argentina.

Since the mid-2000s, livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) has been identified among pigs worldwide, CC398 being the most relevant LA-MRSA clone. In the present work, nasal swabs were taken from healthy pigs of different age categories (25 to 154 days) from 2019 to 2021 in four intensive farms located in three provinces of Argentina. The aim of the present study was to characterize the first LA-MRSA isolates that colonized healthy fattening pigs in Argentina in terms of their resistance phenotype and genotype and to know the circulating clones in the country. Antimicrobial susceptibility, presence of the mecA gene and PCR screening of CC398 were evaluated in all the isolates. They were resistant to cefoxitin, penicillin, tetracycline, chloramphenicol and ciprofloxacin but susceptible to nitrofurantoin, rifampicin, vancomycin and linezolid. Furthermore, 79% were resistant to clindamycin and lincomycin, 68% to erythromycin, 58% to gentamicin and 37% to trimethoprim/sulfamethoxazole. All the isolates were multidrug resistant. The clonal relation was assessed by SmaI-PFGE (pulsed-field gel electrophoresis) and a representative isolate of each PFGE type was whole genome sequenced by Illumina. MLST (multilocus sequence typing), resistance and virulence genes and SCCmec typing were performed on sequenced isolates. The isolates were differentiated in three clonal types by PFGE, and they belonged to sequence-type ST398 (58%) and ST9, CC1 (42%) by MLST. SCCmec typeV and several resistance genes detected showed complete correlation with resistance phenotypes. The present study revealed that LA-MRSA colonizing healthy pigs in Argentina belongs to CC398 and CC1, two MRSA lineages frequently associated to pigs in other countries.

Beta-lactam antibiotics and viridans group streptococci / Antibióticos beta-lactámicos y estreptococos grupo viridans

Abstract The aim of this review is to present an update on the susceptibility of viridans groupstreptococci (VGS) to -lactam antimicrobials, with emphasis on the Argentinean scenario. VGSare a heterogeneous group including five groups of species, each one exhibiting peculiar sus-ceptibility patterns to penicillin (PEN). Species of the Streptococcus mitis group are frequentlynonsusceptible to PEN. PEN resistance is associated with changes in PEN-binding proteins. InArgentina, one to two thirds of VGS are nonsusceptible to PEN. Third generation cephalosporinsand carbapenems are currently more effective in vitro than PEN against VGS. Mortality was asso-ciated to nonsusceptibility to PEN in at least two studies involving patients with bacteremiacaused by VGS. Treatment of endocarditis due to VGS should be adjusted/to the PEN suscepti-bility of the isolates. Vancomycin may be an alternative choice for treating endocarditis causedby PEN-resistant isolates (MIC 4 g/ml).

Resumen El objetivo de esta revisión es presentar una actualización sobre la sensibilidad de los estreptococos del grupo viridans (EGV) a los antimicrobianos p-lactámicos, con énfasis en el escenario argentino. Los EGV son un grupo heterogéneo que incluye cinco grupos de especies, y cada una presenta su patrón especial de sensibilidad a la penicilina (PEN). Las especies del grupo Streptococcus mitis, con mayor frecuencia, no son sensibles a la PEN. La resistencia a la PEN se asocia con cambios de las proteínas ligadoras de PEN. En la Argentina, de uno a dos tercios de los EGV no son sensibles a la PEN. Las cefalosporinas de tercera generación y los carbapenemes son actualmente más eficaces in vitro que la PEN contra los EGV. La mortalidad se asoció con la no sensibilidad a la PEN en al menos dos estudios de pacientes con bacteriemia por EGV. El tratamiento de las endocarditis por EGV debe ajustarse según la sensibilidad a la PEN de los aislados. La vancomicina podría ser una elección alternativa para el tratamiento de las endocarditis por cepas resistentes a PEN (CIM >4 ^g/ml).

Beta-lactam antibiotics and viridans group streptococci.

The aim of this review is to present an update on the susceptibility of viridans group streptococci (VGS) to ß-lactam antimicrobials, with emphasis on the Argentinean scenario. VGS are a heterogeneous group including five groups of species, each one exhibiting peculiar susceptibility patterns to penicillin (PEN). Species of the Streptococcus mitis group are frequently nonsusceptible to PEN. PEN resistance is associated with changes in PEN-binding proteins. In Argentina, one to two thirds of VGS are nonsusceptible to PEN. Third generation cephalosporins and carbapenems are currently more effective in vitro than PEN against VGS. Mortality was associated to nonsusceptibility to PEN in at least two studies involving patients with bacteremia caused by VGS. Treatment of endocarditis due to VGS should be adjusted/to the PEN susceptibility of the isolates. Vancomycin may be an alternative choice for treating endocarditis caused by PEN-resistant isolates (MIC≥4µg/ml).

Invasive Streptococcus pneumoniae isolates from pediatric population in Argentina for the period 2006-2019. Temporal progression of serotypes distribution and antibiotic resistance.

Streptococcus pneumoniae is a major cause of severe invasive disease associated with high mortality and morbidity worldwide. A total of 2908 pneumococcal isolates were analyzed between 2006 and 2019. Gold standard pneumococcal serotyping (the Neufeld-Quellung reaction) was performed to identify the serotypes associated with infection in children < 5 years in Argentina and agar dilution method was carried out to determine their profiles to 14 antimicrobial agents. In 2012, the 13-valent pneumococcal conjugate vaccine (PCV13) was included in the National Immunization Program. In this work we have analyzed the local epidemiology of invasive pneumococcal diseases before and after the introduction of this vaccine in order to understand the epidemiological relevance and impact of PCV13. During the periods compared in the present study there was a significant increase in the proportion of non-PCV13 serotypes, serogroup 24 (246.7%) and 12F (85.7%), and a significant decrease in PCV13 serotypes, including serotypes 14 (91.2%), 5 (95.6%) and 1 (84.6%) among others. Another observation was that serotypes 3 (7.4%) and 19A (4.9%) still remain among the most frequent serotypes despite being part of the PCV13 formulation. Regarding antimicrobial resistance, in the present study we observed an increase in erythromycin resistance during the period of study mainly associated to serotype 14 in the pre-PCV13 period and to serogroup 24 in the post-PCV13 period, which also was the major NVT serotype associated with antimicrobial resistance and MDR. Serotypes 14, 24A/B/F and 19A were in the first three places among isolates resistant to all the antibiotics tested. Our data highlight the importance of continuous surveillance to assess the impact of pneumococcal vaccines and the use of antibiotics in the dynamic of pneumococcal serotypes.

Staphylococcus pseudintermedius's PBP4 Is Directly Associated with the Dissociated Oxacillin and Cefoxitin Phenotype.

Staphylococcus pseudintermedius is an important pathogen responsible for infections in dogs and in humans. The emergence and dissemination of methicillin-resistant S. pseudintermedius (MRSP) and the multidrug resistance frequently seen in this species make difficult the treatment of these pathogens. The cefoxitin disk is widely used as a marker of methicillin resistance mediated by the mecA gene in Staphylococcus aureus and other staphylococcal species; however, it is not useful to detect ß-lactam resistance of MRSP in clinical microbiology laboratories. The purpose of this study was to elucidate the molecular bases of the dissociated phenotype between oxacillin and cefoxitin antibiotics. By using a combinatorial approach that included the Penicillin-Binding Proteins' (PBP) profile, their affinity for different ß-lactam antibiotics and the analyses of PBPs' sequence, we provide evidence that PBP4 showed still affinity for its target cefoxitin, impairing its phenotypic resistant detection in MRSP. Together, these findings provide evidence that S. pseudintermedius PBP4 is directly associated with the dissociated oxacillin and cefoxitin phenotype.

Population genetic structure, serotype distribution and antibiotic resistance of Streptococcus pneumoniae causing invasive disease in children in Argentina.

Invasive disease caused by Streptococcus pneumoniae (IPD) is one of the leading causes of morbidity and mortality in young children worldwide. In Argentina, PCV13 was introduced into the childhood immunization programme nationwide in 2012 and PCV7 was available from 2000, but only in the private market. Since 1993 the National IPD Surveillance Programme, consisting of 150 hospitals, has conducted nationwide pneumococcal surveillance in Argentina in children under 6 years of age, as part of the SIREVA II-OPS network. A total of 1713 pneumococcal isolates characterized by serotype (Quellung) and antimicrobial resistance (agar dilution) to ten antibiotics, belonging to three study periods: pre-PCV7 era 1998-1999 (pre-PCV), before the introduction of PCV13 2010-2011 (PCV7) and after the introduction of PCV13 2012-2013 (PCV13), were available for inclusion. Fifty-four serotypes were identified in the entire collection and serotypes 14, 5 and 1 represented 50 % of the isolates. Resistance to penicillin was 34.9 %, cefotaxime 10.6 %, meropenem 4.9 %, cotrimoxazole 45 %, erythromycin 21.5 %, tetracycline 15.4 % and chloramphenicol 0.4 %. All the isolates were susceptible to levofloxacin, rifampin and vancomycin. Of 1713 isolates, 1061 (61.9 %) were non-susceptible to at least one antibiotic and 235(13.7 %) were multidrug resistant. A subset of 413 isolates was randomly selected and whole-genome sequenced as part of Global Pneumococcal Sequencing Project (GPS). The genome data was used to investigate the population structure of S. pneumoniae defining pneumococcal lineages using Global Pneumococcal Sequence Clusters (GPSCs), sequence types (STs) and clonal complexes (CCs), prevalent serotypes and their associated pneumococcal lineages and genomic inference of antimicrobial resistance. The collection showed a great diversity of strains. Among the 413 isolates, 73 known and 36 new STs were identified belonging to 38 CCs and 25 singletons, grouped into 52 GPSCs. Important changes were observed among vaccine types when pre-PCV and PCV13 periods were compared; a significant decrease in serotypes 14, 6B and 19F and a significant increase in 7F and 3. Among non-PCV13 types, serogroup 24 increased from 0 % in pre-PCV to 3.2 % in the PCV13 period. Our analysis showed that 66.1 % (273/413) of the isolates were predicted to be non-susceptible to at least one antibiotic and 11.9 % (49/413) were multidrug resistant. We found an agreement of 100 % when comparing the serotype determined by Quellung and WGS-based serotyping and 98.4 % of agreement in antimicrobial resistance. Continued surveillance of the pneumococcal population is needed to reveal the dynamics of pneumococcal isolates in Argentina in post-PCV13. This article contains data hosted by Microreact.

Resistance to ß-lactams in Streptococcus pneumoniae.

Streptococcus pneumoniae is an important causal agent of pneumonia, meningitis, sepsis, bacteremia, and otitis media. Penicillin resistance rates in S. pneumoniae have remained stable in Argentina in the last years. In the late '90s more isolates with MIC of penicillin ≥2µg/ml were observed; however, their frequency has decreased in recent years. The phenotypic expression of penicillin resistance is due to a modification in penicillin-binding proteins associated with a mosaic structure in the coding genes. The expansion of successful resistant clones varies among the different regions and is influenced by the use of antibiotics, vaccines, particularly conjugated ones, as well as population density. Parenteral treatment with high doses of penicillin G continues to be effective for the treatment of pneumonia and bacteremia, oral aminopenicillins for otitis media and sinusitis and third generation cephalosporins for meningitis.

[Evolution of the performance of Latin America Reference Laboratories in the detection of mechanisms of antimicrobial resistanceEvolução do desempenho dos Laboratórios de Referência na América Latina na detecção de mecanismos de resistência antimicrobiana]. / Evolución del desempeño de Laboratorios de Referencia de América Latina en la detección de mecanismos de resistencia a los antimicrobianos.

OBJECTIVE: The objective is to present the results of the Latin American Program for Quality Assurance in Bacteriology and Antimicrobial Resistance (LA-EQAS) between 2000 and 2018 and the evolution of the detection of resistance mechanisms with clinical impact. METHODS: The participating National Reference Laboratories (NRLs) received 25 surveys with 10 strains in each one, representing a total of 86 bacterial species and 40 resistance mechanisms. To evaluate the performance of the NRLs, five indicators were analyzed: bacterial identification, interpretation of susceptibility testing, acceptable ranges for zones of inhibition, inferred resistance mechanism, and delay time for the response. RESULTS: The average concordance was 82.6% (range: 74-95%) for bacterial identification, 93.3% (85-98%) for the interpretation of susceptibility testing, 84.6% (70-94%) for the zones of inhibition, and 82.5% (73-96%) for the inferred resistance mechanisms. The average delay time for the response was 34 days. Improvements in the detection of mechanisms of clinical importance, such as resistance to methicillin, macrolides and glycopeptides in Gram-positive cocci, and extended-spectrum, AmpC plasmid and carbapenemase beta-lactamases in Gram-negative bacilli, were observed. CONCLUSIONS: The LA-EQAS is an excellent tool for continuous quality improvement in the diagnosis of infections due to multiresistant microorganisms in NRLs in Latin America.

OBJETIVO: O objetivo deste trabalho é apresentar os resultados do Programa Latino-Americano de Garantia da Qualidade em Bacteriologia e Resistência Antimicrobiana (LA-EQAS, na sigla em inglês) entre 2000 e 2018 e a evolução na detecção de mecanismos de resistência com impacto clínico. MÉTODOS: Os Laboratórios Nacionais de Referência (LNRs) participantes receberam 25 inquéritos com 10 cepas bacterianas cada, representando um total de 86 espécies bacterianas e 40 mecanismos de resistência. Para avaliar o desempenho dos LNRs, foram analisados cinco indicadores: identificação bacteriana, interpretação dos testes de sensibilidade, faixas das zonas de inibição aceitáveis, mecanismo de resistência inferido e tempo de demora na resposta. RESULTADOS: A concordância média foi de 82,6% (intervalo: 74-95%) na identificação bacteriana, 93,3% (85-98%) na interpretação dos testes de sensibilidade, 84,6% (70-94%) nas zonas de inibição, 82,5% (73-96%) no mecanismo de resistência inferido e 34 dias na demora na resposta. Observou-se uma melhoria na detecção de mecanismos clinicamente relevantes, como a resistência a meticilina, macrolídeos e glicopeptídeos em cocos Gram-positivos, beta-lactamases de espectro ampliado, AmpC plasmídica e carbapenemases em bacilos Gram-negativos. CONCLUSÕES: O LA-EQAS é uma excelente ferramenta para a melhoria contínua da qualidade no diagnóstico de infecções por microrganismos multirresistentes nos LNRs da América Latina.

Evolución del desempeño de Laboratorios de Referencia de América Latina en la detección de mecanismos de resistencia a los antimicrobianos

[RESUMEN]. Objetivo. El objetivo es presentar los resultados del Programa Latinoamericano de Aseguramiento de la Calidad en Bacteriología y Resistencia a los Antimicrobianos (LA-EQAS) entre 2000 y 2018 y la evolución en la detección de mecanismos de resistencia de impacto clínico. Métodos. Los Laboratorios Nacionales de Referencia (LNR) participantes recibieron 25 encuestas con 10 cepas cada una, representando un total de 86 especies bacterianas y 40 mecanismos de resistencia. Para evaluar el desempeño de los LNR, se analizaron cinco indicadores: identificación bacteriana, interpretación de las pruebas de sensibilidad, rangos de las zonas de inhibición aceptables, mecanismo de resistencia inferido, y tiempo de demora en la respuesta. Resultados. La concordancia media fue 82,6% (rango: 74-95%) en la identificación bacteriana, 93,3% (85-98%) en la interpretación de las pruebas de sensibilidad, 84,6% (70-94%) en las zonas de inhibición, 82,5% (73-96%) en el mecanismo de resistencia inferido, y la demora en la respuesta, 34 días. Se observó una mejora en la detección de mecanismos de relevancia clínica como resistencia a meticilina, macrólidos y glucopéptidos en cocos gram positivos, y betalactamasas de espectro extendido, AmpC plasmídico y carbapenemasas en bacilos gram negativos. Conclusiones. El LA-EQAS es una excelente herramienta para la mejora continua de la calidad en el diagnóstico de las infecciones por microorganismos multirresistentes en los LNR de América Latina.

[RESUMEN]. Objetivo. El objetivo es presentar los resultados del Programa Latinoamericano de Aseguramiento de la Calidad en Bacteriología y Resistencia a los Antimicrobianos (LA-EQAS) entre 2000 y 2018 y la evolución en la detección de mecanismos de resistencia de impacto clínico. Métodos. Los Laboratorios Nacionales de Referencia (LNR) participantes recibieron 25 encuestas con 10 cepas cada una, representando un total de 86 especies bacterianas y 40 mecanismos de resistencia. Para evaluar el desempeño de los LNR, se analizaron cinco indicadores: identificación bacteriana, interpretación de las pruebas de sensibilidad, rangos de las zonas de inhibición aceptables, mecanismo de resistencia inferido, y tiempo de demora en la respuesta. Resultados. La concordancia media fue 82,6% (rango: 74-95%) en la identificación bacteriana, 93,3% (85-98%) en la interpretación de las pruebas de sensibilidad, 84,6% (70-94%) en las zonas de inhibición, 82,5% (73-96%) en el mecanismo de resistencia inferido, y la demora en la respuesta, 34 días. Se observó una mejora en la detección de mecanismos de relevancia clínica como resistencia a meticilina, macrólidos y glucopéptidos en cocos gram positivos, y betalactamasas de espectro extendido, AmpC plasmídico y carbapenemasas en bacilos gram negativos. Conclusiones. El LA-EQAS es una excelente herramienta para la mejora continua de la calidad en el diagnóstico de las infecciones por microorganismos multirresistentes en los LNR de América Latina.

[RESUMO]. Objetivo. O objetivo deste trabalho é apresentar os resultados do Programa Latino-Americano de Garantia da Qualidade em Bacteriologia e Resistência Antimicrobiana (LA-EQAS, na sigla em inglês) entre 2000 e 2018 e a evolução na detecção de mecanismos de resistência com impacto clínico. Métodos. Os Laboratórios Nacionais de Referência (LNRs) participantes receberam 25 inquéritos com 10 cepas bacterianas cada, representando um total de 86 espécies bacterianas e 40 mecanismos de resistência. Para avaliar o desempenho dos LNRs, foram analisados cinco indicadores: identificação bacteriana, interpretação dos testes de sensibilidade, faixas das zonas de inibição aceitáveis, mecanismo de resistência inferido e tempo de demora na resposta. Resultados. A concordância média foi de 82,6% (intervalo: 74-95%) na identificação bacteriana, 93,3% (85-98%) na interpretação dos testes de sensibilidade, 84,6% (70-94%) nas zonas de inibição, 82,5% (73-96%) no mecanismo de resistência inferido e 34 dias na demora na resposta. Observou-se uma melhoria na detecção de mecanismos clinicamente relevantes, como a resistência a meticilina, macrolídeos e glicopeptídeos em cocos Gram-positivos, beta-lactamases de espectro ampliado, AmpC plasmídica e carbapenemases em bacilos Gram-negativos. Conclusões. O LA-EQAS é uma excelente ferramenta para a melhoria contínua da qualidade no diagnóstico de infecções por microrganismos multirresistentes nos LNRs da América Latina.

Characterization of the First mecA-Positive Multidrug-Resistant Staphylococcus pseudintermedius Isolated from an Argentinian Patient.

Staphylococcus pseudintermedius is commonly associated with colonization or infection in dogs, and was identified as a novel species within the genus Staphylococcus in 2006. Methicillin resistance emerged in S. pseudintermedius during the last decade. We describe here a genomic characterization of the first methicillin-resistant S. pseudintermedius (MRSP) recovered from a human patient in Argentina. The strain was phenotypically identified as MRSP 8510 by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and antimicrobial susceptibility testing. We assessed genetic characterization by mecA PCR, SCCmec (staphylococcal chromosomal cassette) typing, and whole-genome sequencing. MRSP 8510 was phenotypically resistant to six classes of antimicrobial agents, consistent with the genes found in its genome. We concluded that MRSP 8510 was a multidrug-resistant ST1412 isolate. This study highlights the importance of the detection and characterization of pathogens with potential risks of zoonotic transmission to humans, as they may constitute a reservoir of genes associated with antimicrobial resistance.

MRSA dynamic circulation between the community and the hospital setting: New insights from a cohort study.

Dissemination of methicillin-resistant-Staphylococcus aureus/(MRSA) is a worldwide concern both in hospitals [healthcare-associated-(HA)-MRSA] and communities [community-associated-(CA)-MRSA]. Knowledge on when and where MRSA colonization is acquired and what clones are involved is necessary, to focus efforts for prevention of hospital-acquired MRSA-infections. METHODS: A prospective/longitudinal cohort study was performed in eight Argentina hospitals (Cordoba/ October-December/2014). Surveillance cultures for MRSA (nose-throat-inguinal) were obtained on admission and at discharge. MRSA strains were genetically typed as CA-MRSAG and HA-MRSAG genotypes. RESULTS: Overall, 1419 patients were screened and 534 stayed at hospital for ≥3 days. S. aureus admission prevalence was 30.9% and 4.2% for MRSA. Overall MRSA acquisition rate was 2.3/1000 patient-days-at-risk with a MRSA acquisition prevalence of 1.96% (95%CI: 1.0%-3.4%); 3.2% of patients were discharged back to community with MRSA. CA-MRSAG accounted for 84.6% of imported, 100.0% of hospital-acquired and 94% of discharged MRSA strains. Most imported and acquired MRSA strains belonged to two major epidemic CA-MRSA clones spread in Argentina: PFGEtypeI-ST5-IVa-t311-PVL+ and PFGEtypeN/ST30-IVc-t019-PVL+. CONCLUSIONS: CA-MRSA clones, particularly ST5-IV-PVL+ and ST30-IV-PVL+, with main reservoir in the community, not only enter but also are truly acquired within hospital, causing healthcare-associated-hospital-onset infections, having a transmission capacity greater or similar than HA-MRSAG. This information is essential to develop appropriate MRSA infection prevention-control programs, considering hospital and community.

Identification and molecular epidemiology of methicillin resistant Staphylococcus pseudintermedius strains isolated from canine clinical samples in Argentina.

BACKGROUND: Staphylococcus pseudintermedius is the leading cause of pyoderma in dogs and the frequent use of antimicrobial treatment is associated to the development of resistance to nearly all classes of antibiotics. Despite S. pseudintermedius significance, our understanding of the molecular mechanism of ß-lactam resistance and its genetic diversity remains limited. We aimed to: i) determine the phenotypic resistance profile of methicillin resistant Staphylococcus pseudintermedius (MRSP) isolated from infected dogs in three different veterinary hospitals in Buenos Aires, Argentina; ii) identify the SCCmec elements and resistance genes; and iii) analyze the clonal relationship between isolates and in regard of dominant lineages found in the world. RESULTS: In addition to the differential levels of ß-lactam resistance, MRSP isolates (n = 10) showed resistance to 5-6 families of antibiotics, and were therefore categorized as multidrug-resistant. All the isolates were variant of SCCmec V homologous to S. aureus; additional SCCmecFinder analysis classified five of the genomes as SCCmec type V (5C2&5) with mecA (encodes for PBP2a), mecRI and mecI and all the genes closely related to the reference SCCmec type V S. aureus TSGH17 strain. In the remaining five strains, mecA was present, although other genes associated with SCCmec V including mecR1 and mecI were missing. PBP2a was inducible in low level resistance strains (MRSP 8151), and constitutively expressed in MRSP 8150, suggesting different mecA regulatory mechanisms. MRSP isolates showed significant genetic diversity: eight PFGE clonal types and six multilocus-sequence typing (MLST) sequence types (STs) (339, 649, 919, 920, 921 and 922), including four new STs genetically distinct from STs reported in other geographic areas. Comparative genomics and phylogenetic analyses of the MRSP showed a correlation between the genetic content and the phenotypes, and established the genetic relationship between the isolates. CONCLUSIONS: MRSP could be a threat to animal health due to it concerning level of antimicrobial resistance. Our study highlights genetic and epidemiological aspects of multidrug-resistant MRSP strains from Argentina showing high degree of correlation between the resistance genes and the phenotype of the isolates and, furthermore, they appeared evolutionary closer to major worldwide reported ST68 and ST71.

Resistencia a los β -lactámicos en enterococos / Resistance to β-lactams in enterococci

Enterococci are intrinsically resistant to several antimicrobial classes and show a great ability to acquire new mechanisms of resistance. Resistance to β-lactam antibiotics is a major concern because these drugs either alone or in combination are commonly used for the treatment of enterococcal infections. Ampicillin resistance, which is rare in Enterococcus faecium occurs in most of the hospital-associated Enterococcus faecium isolates. High-level resistance to ampicillin in E. faecium is mainly due to the enhanced production of PBP5 and/or by polymorphisms in the beta subunit of this protein. The dissemination of high-level ampicillin resistance can be the result of both clonal spread of strains with mutated pbp5 genes and resistance horizontal gene transfer.

Los enterococos son intrínsecamente resistentes a varias clases de antimicrobianos y presentan una gran capacidad para adquirir mecanismos de resistencia. La resistencia a los antibióticos p-lactámicos es preocupante porque estos fármacos solos o combinados se usan comúnmente para el tratamiento de las infecciones enterocócicas. La mayoría de los aislamientos hospitalarios de Enterococcus faecium presentan resistencia a la ampicilina, la cual es rara en Enterococcus faecalis. El alto nivel de resistencia a la ampicilina en E. faecium se debe principalmente a la hiperproducción de PBP5 y/o a polimorfismos en la subunidad beta de esta proteína. La propagación de esta resistencia puede deberse tanto a la diseminación clonal de cepas con genes pbp5 mutados como a la transferencia horizontal de genes.

Resistance to ß-lactams in enterococci.

Enterococci are intrinsically resistant to several antimicrobial classes and show a great ability to acquire new mechanisms of resistance. Resistance to ß-lactam antibiotics is a major concern because these drugs either alone or in combination are commonly used for the treatment of enterococcal infections. Ampicillin resistance, which is rare in Enterococcus faecalis, occurs in most of the hospital-associated Enterococcus faecium isolates. High-level resistance to ampicillin in E. faecium is mainly due to the enhanced production of PBP5 and/or by polymorphisms in the beta subunit of this protein. The dissemination of high-level ampicillin resistance can be the result of both clonal spread of strains with mutated pbp5 genes and horizontal gene transfer.

Susceptibility to β-lactams in β-hemolytic streptococci / Sensibilidad a los β-lactámicos en estreptococos β-hemolíticos

Group A (GAS), B (GBS), c (GCS) and G (GGS) β-hemolytic streptococci are important human pathogens. They cause infections of different severity and frequency. Nowadays, after 70 years of use, penicillin is still universally active against GAS, GCS and GGS. However, therapeutic failures have been recorded in 2-28% of pharyngitis cases (median: 12%) attributable to different causes. By contrast, some GBS with reduced susceptibility to penicillin have been described, especially in Japan. In this group of bacteria, it is important to highlight that confirmation by reference methods is mandatory when decreased susceptibility to penicillin is suspected as well as checked for the detection of the mechanisms involved.

Los estreptococos β-hemolíticos de los grupos A (GAS), B (GBS), C (GCS) y G (GGS) son importantes patógenos humanos. Ellos producen infecciones de diversa gravedad y frecuencia. Aún después de más de 70 años de uso, la penicilina sigue siendo activa in vitro frente al 100% de los GAS, GCS y GGS. No obstante se han producido fallas terapéuticas entre el 2-28% de los casos de faringitis (media: 12%), atribuibles a diversas causas. En cambio se han descrito aislados de GBS con sensibilidad reducida a la penicilina, especialmente en Japón. Es importante que toda sospecha de sensibilidad disminuida a la penicilina en este grupo de bacterias sea confirmada por los métodos de referencia y comprobada mediante la detección de los mecanismos involucrados.

Susceptibility to ß-lactams in ß-hemolytic streptococci.

Group A (GAS), B (GBS), C (GCS) and G (GGS) ß-hemolytic streptococci are important human pathogens. They cause infections of different severity and frequency. Nowadays, after 70 years of use, penicillin is still universally active against GAS, GCS and GGS. However, therapeutic failures have been recorded in 2-28% of pharyngitis cases (median: 12%) attributable to different causes. By contrast, some GBS with reduced susceptibility to penicillin have been described, especially in Japan. In this group of bacteria, it is important to highlight that confirmation by reference methods is mandatory when decreased susceptibility to penicillin is suspected as well as checked for the detection of the mechanisms involved.