Optimización de metodologías de cribaje para la búsqueda de Streptococcus agalactiae en embarazadas / Optimization of screening methodologies for the detection of Streptococcus agalactiae in pregnant women

Streptococcus agalactiae es una causa importante de morbimortalidad en mujeres embarazadas y neonatos en todo el mundo. El objetivo del presente trabajo fue determinar la utilidad del medio cromogénico chromID Strepto B de bioMérieux para detectar S. agalactiae en embarazadas cuando la muestra es sembrada directamente en dicho medio o después del enriquecimiento en caldo de Todd Hewitt selectivo, opciones que se compararon con la metodología propuesta por el CDC . Se analizaron 1924 hisopados, 962 de introito vaginal y 962 rectales, correspondientes a 962 embarazadas entre la semana 35 y 37 de gestación, asistidas en distintos hospitales. Los hisopados se sembraron directamente en el medio chromID Strepto B (CR) y luego se colocaron en un caldo de Todd Hewitt selectivo, suplementado con 15 µg/ml de ácido nalidíxico y 10 µg/ml de colistina (CTH-sel). Luego de 24 h de incubación, se realizaron subcultivos en el medio CR y en agar con 5% de sangre de carnero (ASO). La prevalencia global de S. agalactiae fue de 17,4%. La sensibilidad, la especificidad y los valores predictivos positivo y negativo del subcultivo en CR del material desarrollado en el CTH -sel fueron 98,8%, 100%, 100% y 99,7% respectivamente, con una incubación de 48 h. Los valores correspondientes de la siembra directa fueron 57,8%, 100%, 100% y 90%. La sensibilidad del subcultivo en ASO del material desarrollado en el CTH -sel fue del 85%. Se destaca el excelente rendimiento del subcultivo en CR luego del enriquecimiento en caldo de Todd Hewitt selectivo en comparación con el método propuesto por el CDC.

Streptococcus agalactiae is a significant worldwide cause of morbidity and mortality in pregnant women and their newborn infants. The objective of this work was to determine the usefulness of bioMrieux chromogenic medium chromID Strepto B (CR) for detecting S. agalactiae in pregnant women from the selective Todd-Hewitt broth (sel-THB ) against the methods proposed by the CDC . A total of 1924 swabs were analyzed, 962 from vaginal introitus and 962 rectal, belonging to 962 women in weeks 35-37 of pregnancy. The swabs were directly seeded in CR. Both swabs were later placed in sel-THB with 15 µg/ml supplement of nalidixic acid and 10 µg/ml colistin. After 24 h of incubation, subcultures in CR medium and agar containing 5% sheep blood (SBA) were performed. The prevalence found was 17.4%. Sensitivity, specificity, positive and negative predictive values of sel-THB subcultures with CR supplement and 48 h incubation were: 98.8, 100, 100 and 99.7%, respectively. The corresponding values of direct harvest of the sample were 57.8, 100, 100, and 90%, respectively. Sensitivity of sel-THB in SBA was 85%. Sel-THB subculture performance in CR was outstanding in comparison with the method proposed by the CDC.

Sepsis neonatal por Streptococcus Grupo B / Group B Streptococcus neonatal sepsis: up-to-date

Group B Streptococcus is one of the leading bacterias causing early onset neonatal sepsis. It constitutes an important factor of neonatal morbidity and mortality and high costs in health. Many strategies have been formulated to avoid vertical transmission from the colonized mother to the newborn, in an attempt to prevent infection of the infant. The most used nowadays is antibiotic prophylaxis given to the mother during labor, depending on the results of recto-vaginal culture taken during 35 to 37 weeks of gestation. This strategy has importantly diminished the prevalence of early onset neonatal sepsis by this agent, although there is still concern about the potential generation of antibiotic resistance and drug-induced adverse reactions in the mother. New techniques for prevention are being developed, such as vaccines against Streptococcus. In the newborn, infection caused by Streptococcus has a broad spectrum of clinical manifestations, like sepsis and meningitis which are the most frequent and lethal. Neurological sequelae are common among the survivors, so an early suspicion of disease must lead to a prompt antibiotic treatment.

El Streptococcus grupo B (SGB) es uno de los principales agentes causales de sepsis neonatal precoz, siendo un importante factor de morbimortalidad neonatal y de costos en salud pública. Se han implementado múltiples estrategias para evitar la transmisión vertical desde la madre colonizada a su recién nacido, de modo de prevenir la infección de éste último. La más usada en la actualidad es la profilaxis antibiótica administrada a la madre en el momento del parto dependiendo del resultado de un cultivo perineal realizado entre las semanas 35 y 37 de gestación. Mediante esta estrategia se ha logrado disminuir de manera importante la incidencia de la sepsis neonatal por este agente, pero existen aprehensiones acerca de la posible generación de resistencia antibiótica o reacciones adversas a fármacos por parte de la madre. Por esto último, nuevas técnicas de prevención se encuentran en estudio, como las vacunas contra el SGB. En los recién nacidos la infección por Streptococcus agalactiae puede manifestarse de diversas maneras, siendo la sepsis y la meningitis las más frecuentes y mortales. El porcentaje de secuelas entre los sobrevivientes es elevado, por lo que ante la sospecha precoz de infección debe iniciarse tratamiento antibiótico a la brevedad.

Comparación de medios de cultivos y procedimientos para detectar colonización por Streptococcus agalactiae en mujeres embarazadas / Comparison between culture media and procedures to detect Streptococcus agalactiae in pregnant women

Introducción: La detección de Streptococcus agalactiae en la vagina y/o el recto de las mujeres embarazadas y la administración de profilaxis antimicrobiana intraparto en las colonizadas, es el método recomendado para prevenir la infección neonatal precoz por este patógeno. En consecuencia, es importante seleccionar los medios de cultivos y el sitio de toma de muestra más adecuado para la detección de S. agalactiae en mujeres colonizadas. Objetivo: Comparar diferentes medios de cultivos y procedimientos para la recuperación de S. agalactiae en mujeres embarazadas con complicaciones gineco-obstétricas. Metodología: Se tomaron hisopados vagino-ano-rectales y endocer-vicales de 60 mujeres embarazadas. Con la primera muestra se realizó cultivo directo en agar sangre Columbia selectivo (ASCSD), y caldo selectivo Todd Hewitt (CSTH) incubados a 37 °C, y subcultivos a las 4 y 18 horas en agar sangre Columbia selectivo (ASCS). La segunda muestra se cultivó en ASCS. El ASCSD y ASCS se incubaron en atmósfera microaeróñla a 37 °C durante 24 a 48 horas. La identificación de S. agalactiae se realizó mediante pruebas convencionales. Resultados: Utilizando hisopado vagino-ano-rectal se detectaron 21 pacientes colonizadas con S. agalactiae, de la siguiente manera: 19(31,7 por ciento) en el ASCSD, 21 (35 por ciento) en el CSTH a las 4 horas y 20 (33,3 por ciento) a las 18 horas. De las 21 pacientes colonizadas sólo a una paciente se le detectó S. agalactiae en la muestra de secreción vagino-ano-rectal y endocervical simultáneamente. Conclusión: Los tres procedimientos ensayados presentaron igual efectividad para la recuperación de S. agalactiae; sin embargo, con el uso del ASCSD, se disminuyen los costos y el tiempo de identificación de dicho microorganismo. Por otra parte, el hisopado vagino-ano-rectal resultó ser la muestra más idónea para detectar colonización por S. agalactiae en mujeres embarazadas.

Detection of Streptococcus agalactiae in pregnant women's vagina and rectum and intrapartum antibiotic prophylaxis administered to colonized women are currently recommended to prevent neonatal precocious infections by this organism. In turn, it is very important to select the culture media and adequate sample collection site for S. agalactiae detection in colonized women. To standardize this methods in laboratory, different culture media and procedures for S. agalactiae recovery in pregnant women with obstetric and gynecologic complications were compared. Vaginorectal and endocervical swab specimens were collected from 60 pregnant women. The first sample was placed onto selective Columbia blood agar directly and onto selective Todd-Hewitt broth incubated at 37 °C and subcultured onto selective Columbia blood agar at 4 and 18 hours. The second sample was cultured on selective Columbia blood agar. Both culture media were incubated in a microaerophilic atmosphere at 37 °C from 24 to 48 hours. S. agalactiae was identified using conventional tests. 21 patients colonized with S. agalactiae were detected using vaginoanorectal samples. 19 (31.7 percent) patients tested positive for S. agalactiae through the culture of specimens directly onto selective Columbia blood agar; 21 (35 percent) and 20 (33 percent) patients were found to be positive for S. agalactiae by the selective Todd-Hewitt broth at 4 and 18 hours, respectively. Only one patient tested positive for S. agalactiae in the endocervical tract. The results show that the three procedures followed for S. agalactiae recovery are effective. Nevertheless, the procedure in which the sample was placed directly onto selective Columbia blood agar permits reducing costs and the time for bacteria identification. On the other hand, the vaginoanorectal swab was the best sample to detect colonization by S. agalactiae in pregnant women.

Diversity of surface protein expression in group B streptococcal colonizing & invasive isolates.

BACKGROUND & OBJECTIVES: The classification of group B streptococcal (GBS) isolates is based on the capsular polysaccharides (Ia-VIII), and antigenic characterization of clinical isolates is augmented by the detection of various surface-localized protein antigens. In our laboratory, all GBS isolates are routinely analysed for the alpha trypsin-resistant and the beta trypsin-sensitive c protein antigens, as well as other trypsin-resistant proteins R1, R3, and R4, as well as BPS. The purpose of this work was to study diversity of protein expression in colonizing isolates (vaginal and rectal sites) from nonpregnant women and from invasive isolates (blood or CSF) from mothers and their less than seven day old newborn infants. METHODS: A total of 289 invasive isolates and 2660 colonizing isolates were collected between 1993-2002. All isolates were tested for polysaccharide serotype and cell surface-expressed protein profile by double immunoprecipation in agarose using monospecific antisera. RESULTS: Among the 289 invasive isolates, 89.6 per cent expressed one or more trypsin-resistant proteins; 93 per cent of the colonizing isolates expressed one or more of these proteins. Overall, the most common surface protein expression profile by GBS serotype was: alpha in type Ia; alpha plus beta in type Ib; alpha and R4 in type II; R4 in type III; and co-expression of R1 plus R4 in isolates of type V. BPS was found in five (1.7%) invasive isolates, alone in two isolates and with other proteins in three isolates. Among 2660 colonizing isolates, BPS was found alone in 15 (0.6%) and in 57 additional isolates with other proteins. Among the total isolates, BPS was found predominantly in serotype Ia isolates, also expressing R1. Uncommon protein profiles of known serotypes included 11 type III isolates expressing alpha plus beta. Among 72 nontypable colonizing isolates, expression of R1 plus R4 was the commonest (33.3%) profile. INTERPRETATION & CONCLUSION: The GBS surface proteins and the common serotypes were distributed comparably in colonizing and invasive isolates. Trypsin-resistant, alpha and alpha-like proteins, R1 and R4 were the most prevalent. The phenotypic diversity of the surface-localized protein antigens of GBS is intriguing, and genotypic analysis will permit consensus in nomenclature from laboratory to laboratory.

Vaginal carriage of group B Streptococcus in infertile women.

From May, 1999 to April, 2000, 256 high vaginal swabs were culture from asymptomatic infertile women attending the out-patient department of the Institute of Reproductive Medicine. 41 strains of Streptococcus agalactiae were isolated from 33 patients (12.89%). Five patients had repeated isolations even after adequate therapy.