Emerging trends in invasive and noninvasive isolates of Streptococcus agalactiae in a Latin American hospital: a 17-year study.

BACKGROUND: Streptococcus agalactiae or group B Streptococcus (GBS) has been recognized as a lethal pathogen in neonates worldwide. S. agalactiae infections also severely affect pregnant women and immunosuppressed adults with substantial attributable morbidity and mortality. However, in Latin America, studies on the epidemiology and behaviour of S. agalactiae infections remain limited. METHODS: To better understand the behaviour of S. agalactiae infections in our region, we conducted a retrospective study to phenotypically describe S. agalactiae isolates collected in one of the largest hospitals in Colombia at two time periods: 1994-2001 and 2004-2012. The isolates were identified by biochemical analysis and tested for antimicrobial susceptibility. RESULTS: In 1994-2001 a total of 201 S. agalactiae isolates were found in urine 38.3%, vaginal exudates 27.8%, soft tissue 12.9%, and blood 8.5%. Susceptibility to ampicillin or penicillin was 94% whereas resistance to erythromycin and clindamycin were 2.8% and 5.2% respectively. In total 46 culture-positive cases of invasive infections were reported, 11 (24%) in neonates and 35 (76%) in adults. In 2004-2012 a total of 671 isolates were found in urine 47.8%, vaginal exudates 32.6%, soft tissue 2.7% and blood 9%. Susceptibility rates to ampicillin and penicillin were 98% whereas resistance to erythromycin and clindamycin were 12.5% and 9.4%. A total of 95 severe infections were reported: 12 (12.6%) were in neonates, 5 (5.3%) in children and 78 (82.1%) in adults. Over the 17-year study period the averaged prevalence of invasive S. agalactiae isolates was 17.4%. The estimated incidence for neonatal infections was 1.34 per 1000 livebirths (0.99 × 1000 livebirths for early- onset disease and 0.35 × 1000 livebirths for late- onset disease) whereas for non-pregnant adults the estimated incidence was 0.75 × 1000 admissions. CONCLUSIONS: A remarkable increase in bloodstream infections in immunosuppressed adults and a shift to early neonatal S. agalactiae infections were seen over time. We also found an increase in S. agalactiae resistance to erythromycin and clindamycin during the study period, and the emergence of penicillin-nonsusceptible isolates. Our findings are consistent with the global trends described elsewhere, reinforcing the need for S. agalactiae control measures in our region.

Estrategias para la implementación y reporte de los puntos de corte CLSI vigentes y pruebas fenotípicas confirmatorias para BLEE y carbapenemasas en bacilos Gram negativos en laboratorios clínicos de Colombia / Strategies for implementation and reporting of current CLSI Breakpoints and phenotypic confirmatory tests for ESBLs and carbapenemases in Gram-negative bacilli in Colombian clinical laboratories

En 2010, el Instituto Americano de Estándares Clínicos y de Laboratorio (CLSI) inició un proceso de revisión y actualización de los puntos de corte para microdilución y disco difusión para cefalosporinas (cefazolina, cefotaxima, ceftriaxona, ceftizoxima, ceftazidima), monobactámicos (aztreonam) y carbapenémicos (imipenem, meropenem, ertapenem, doripenem). Los cambios se basaron en modelos PK/PD que buscan predecir la respuesta clínica con el uso exclusivo de la concentración inhibitoria mínima (CIM) y esquemas específicos de dosificación de forma independiente al mecanismo de resistencia expresado. Este nuevo paradigma eliminaría la necesidad de realizar pruebas fenotípicas para beta-lactamasas de espectro extendido (BLEE) y carbapenemasas para tomar decisiones terapéuticas y permitiría utilizarlas únicamente para fines epidemiológicos. Sin embargo, ante las limitaciones de las metodologías actuales para pruebas de susceptibilidad en Colombia, el desconocimiento de estos cambios y la alarma epidemiológica por la aparición de nuevas ß-lactamasas en el país, se hace necesario generar recomendaciones para los laboratorios clínicos, con el fi n de unifi car los criterios para la realización e informe de los antibiogramas en bacilos Gram negativos, incluyendo la implementación de los puntos de corte actuales y la aplicación de las pruebas fenotípicas para la detección de BLEE y carbapenemasas.

In 2010, the Clinical and Laboratory Standards Institute (CLSI) began a process to revise and update the breakpoints for broth microdilution and disk diffusion for cephalosporins (Cefazolin, Cefotaxime, Ceftriaxone, Ceftazidime), monobactams (Aztreonam) and carbapenems (Imipenem, Meropenem, Ertapenem and Doripenem). The changes made were based on PK/PD models that attempt to predict clinical outcomes using minimum inhibitory concentration (MIC) and specific dosage regimens, regardless of the resistance mechanism expressed by the organism. The new breakpoints would eliminate the need to perform screening and confirmatory testing for ESBLs and carbapenemases for treatment decisions, and thus they would be used only for infection control purposes. Nevertheless, there are limitations to current methods in Colombia, a lack of knowledge regarding the recent changes and epidemiologic alarm over new B-lactamases spreading in our country. Therefore it was necessary to formulate and issue recommendations for clinical laboratories, with the aim of standardizing the criteria for reports on antibiograms in Gram-negative bacilli, including the current CLSI breakpoints and applying phenotypic confirmatory testing to detect ESBLs and Carbapenemases.