INCIDENCE OF RECTOVAGINAL COLONIZATION BY STREPTOCOCCUS AGALACTIAE IN PREGNANT WOMEN AND EVALUATION OF COMBINED SWAB CULTURES

ROCCHETTI T. T.(1), MARCONI C.(1), BORGES V. T. M.(2), RALL V. L. M.(3), TRISTÃO A. R.(2), CORRENTE J. E.(4), SILVA M. G.(1)

(1) Department of Pathology, Botucatu Medical School, UNESP - São Paulo State University, Botucatu, Brazil. (2) Department of Gynecology and Obstetrics, Botucatu Medical School, UNESP - São Paulo State University, Botucatu, Brazil. (3) Department of Microbiology and Immunology, Botucatu Institute of Bioscience, UNESP - São Paulo State University, Botucatu, Brazil. (4) Department of Biostatistics, Botucatu Institute of Biosciences, UNESP - São Paulo State University, Botucatu, Brazil.

ABSTRACT: This study aimed to associate Streptococcus agalactiae colonization with vaginal flora of pregnant women and to evaluate the efficacy of combined swabs in S. agalactiae detection. Four hundred and five pregnant women assisted by the pre-natal service of University Hospital of Botucatu Medical School with gestational age between 35 and 37 weeks were included. Samples from anorectal region (AR), vaginal introitus (VI) and distal vaginal wall (VW) were collected with sterile swabs and cultivated in Todd Hewitt broth supplemented with colistin(10ug/mL) and nalidixic acid(15ug/mL) for 24 hours at 37ºC. Next, a subculture in 5% blood-agar was made at same conditions. Those S. agalactiae suggestive colonies were submitted to Gram staining, catalase test and CAMP test. The vaginal flora was evaluated by Gram stain vaginal smears. Socio-demographic and obstetrics data were collected by forms. By considering S. agalactiae colonization or not as the response variable, a logistic regression model was fitted adopting stepwise method and taking into account quantitative and qualitative explanatory variables. Tukey test was used for culture positivity on combined and isolated swabs. Findings show that maternal colonization by S. agalactiae was 25.4%. As regards vaginal flora, the most frequent alterations were cytolytic vaginosis (11.3%), bacterial vaginosis (10.9%), candidiasis (8.2%) and Flora II (8.1%). Fitting the logistic regression model, the variables maternal age, number of sexual intercourses/week, occurrence of previous spontaneous abortion, candidiasis and cytolytic vaginosis were associated with colonization. In relation to the collection sites, from the total positive patients for S. agalactiae (103), 14.5% had simultaneous positive cultures for VI and VW; 5.8% for VI and AR and 3.9% for VW and AR. In 47.5% of the patients the cultures were positive in 3 collection sites and in 28.1% had positive culture in one site(9.7% in VI;3.9% in VW and 14.5% in AR). The association of two swabs increased the rate of S. agalactiae in relation to an isolated swab (p<0.05),except for isolated swabs from AR. The association of three collection sites was higher for detection of S. agalactiae colonization (p<0.05). In conclusion, this study points to a high incidence of S. agalactiae in pregnant women and its association with number of sexual intercourse, previous abortion and candidiasis or cytolytic vaginosis. Additionally, the use of combined swabs is more efficient in S. agalactiae detection.

KEY WORDS: Streptococcus agalactiae, maternal colonization, vaginal flora, combined swabs.

CONFLICTS OF INTERESTS: There is no conflict.

FINANCIAL SUPPORT: FAPESP.

CORRESPONDENCE TO: Márcia Guimarães da Silva, Department of Pathology, Botucatu Medical School, UNESP - São Paulo State University, Botucatu, Brazil.

Phone +55 14 3811 6238.  Email: mgsilva@fmb.unesp.br