Published online Sep 26, 2020. doi: 10.12998/wjcc.v8.i18.3988
Peer-review started: April 24, 2020
First decision: April 29, 2020
Revised: July 28, 2020
Accepted: August 22, 2020
Article in press: August 22, 2020
Published online: September 26, 2020
Streptococcus agalactiae (Group B Streptococcus, SGB) is a bacterium that inhabits the gastrointestinal and genital tracts of men and women as a component of their normal microbiota. The colonization of pregnant women by GBS in childbirth represents the main risk factor for the development of infections (pneumonia, meningitis, and sepsis) in newborns through a vertical transmission that occurs in approximately a half of the newborns from colonized mothers and, when antibiotic prophylaxis is not performed, about 1%-4% of the neonates develops an early or a late GBS infection.
The great importance of Group B streptococcal disease for clinical practice and health systems demands the expansion of the knowledge on GBS colonization detection methods and eradication regimens in order to aid in the development of health policies against that infection.
To compare the identification methods, to verify the sensitivity profile, and to determine resistance genes in the GBS strains isolated from pregnant women in prenatal care in basic health units from the county of Vitória da Conquista, in Bahia State, Brazil.
This is a quantitative transversal study that analyzed 186 samples of vaginal and rectal secretions from pregnant women attended in nine basic health units from the county of Vitória da Conquista, in Bahia State, Brazil. Pregnant women with gestational ages from 32 to 40 wk were eligible for this study. The biologic samples were collected with a single vaginorectal swab without speculum use, seeded by depletion onto Streptococcus chromIDTM Strepto B chromogenic media, inoculated in Todd Hewitt broth (BIOMERIÉUX), and placed at a bacteriological incubator under a 35ºC-37ºC temperature during 24 h. Subsequently, the Todd Hewitt broth samples were subcultured in chromogenic agar plates and kept in the incubator for other 24 h in the above-mentioned conditions.
All pink or red colonies (characteristics for GBS identification) underwent legitimate identification tests: CAMP test using the KIT composed by Todd Hewitt agar and Hemolisinabac (PROBAC DO BRASIL) and serogrouping using the SLIDEX®Strepto Plus B KIT (BIOMERIÉUX) for species confirmation.
All serogrouping-confirmed isolates (gold standard method for GBS identification) were forwarded for antibiogram performing by means of the disk-diffusion technique (Kirby and Bauer), following the Clinical and Laboratory Standards Institute recommendations, and an aliquot was preserved at -20ºC in a 15% glycerol brain-heart infusion broth for resistance genes investigation in erythromycin- and/or clindamycin-resistant strains through multiplex Polymerase Reaction Chain.
One hundred and eighty-six samples were analyzed by this study, and GBS strains were identified in 32 of them, representing a 17.2% prevalence among the included pregnant women. The GBS detection after subculturing in Todd Hewitt broth presented the higher sensitivity (96.9%). In six GBS isolates (18.8%), it was verified a clindamycin resistance, and eight isolates (25.0%) presented erythromycin resistance. The resistance was associated with ermB genes in 4 isolates. The mefA gene was detected in 4 strains and the ermTR gene was found in a single strain. In seven isolates, it was detected only one resistance gene (ermB or ermTR or mefA). One strain had two resistance genes (mefA+ermB).
For the first time, we compared identification methods and analyzed the antimicrobial susceptibility profile of GBS strains in the above-mentioned county. The data from this study may be useful in the development of future screening and antibiotic prophylaxis protocols aiming the prevention of GBS neonatal infection.
The information provided by this study is applicable for the elaboration of GBS colonization screening and eradication strategies. Therefore, this study potentially contributed to the reduction of children morbidity and mortality as well as to the decrease of health system costs with the hospitalization of neonates.