Phenotypic and genotypic characterization of Streptococcus agalactiae in pregnant women: first study in a province of Argentina

Abstract

Group B Streptococcus (GBS) is the leading cause of neonatal infections. Our purpose was to characterize GBS colonization in pregnant women, current serotypes, resistance phenotypes and genes associated with virulence. In Misiones, Argentina, there are no previous data on this topic. Vaginal-rectal swabs from 3125 pregnant women were studied between 2004 and 2010. GBS strains were identified by conventional and serological methods (Phadebact Strep B Test, ETC International, Bactus AB, Sweden). Serotypes were detected using Strep-B Latex (Statens Serum Institut, Denmark). Resistance phenotypes were determined by the double-disk test. Genes were studied by PCR. Maternal colonization was 9.38%. Resistance to erythromycin was 11.6%, and the constitutive phenotype was the predominant one. Serotype Ia was the most frequent, whereas serotypes IV, VI, VII and VIII were not detected. The lmb, bca and hylB genes were detected in more than 79% of the strains. In this study, the colonization rate with GBS and the serotype distribution were compared with studies reported in other areas of the country. The high resistance to erythromycin in Misiones justifies performing antibiotic susceptibility testing. The serotype distribution, the genes encoding putative virulence factors, and the patterns of resistance phenotypes of GBS may vary in different areas. They thus need to be evaluated in each place to devise strategies for prevention.

Molecular Characterization of Group B Streptococcus Serotypes By Multiplex Polymerase Chain Reaction

“…3,8,19,[29][30][31] In Brazil, a country of continental proportions, a recent study revealed that in 434 isolates obtained from symptomatic adults and from colonized patients, serotypes Ia (27,6%), II (19,1%), Ib (18,7%) and V (13,6%) were the most predominant; when only the colonized patients were considered, serotype II was the most prevalent in the southeastern region, followed by serotype Ia, while in the northeastern region serotype Ib is the most prevalent, followed by serotype V. Serotype Ia is most prevalent in the mid-western and south regions of the country, followed by serotypes II and V. Another study involving GBS isolates from women of reproductive age identified in most cases of GBS the capsular serotypes Ia (42,2%), II (10,8%), III (14,5%) and V (30,1%). 8 Focused on pregnant women, this study found that serotype Ia was the most prevalent serotype, in agreement with previous literature reports indicating that despite geographic differences in prevalence, this serotype is the most frequently isolated from pregnant women in Latin America; 23 with regard to the prevalence of GBS serotypes in relation to anatomical sites (vaginal and rectal) of sample collection, serotype I prevalence at the two sites was consistent with previous findings. 21,23 Surprisingly, serotype V was also frequent at both sites.…”

“…8 Focused on pregnant women, this study found that serotype Ia was the most prevalent serotype, in agreement with previous literature reports indicating that despite geographic differences in prevalence, this serotype is the most frequently isolated from pregnant women in Latin America; 23 with regard to the prevalence of GBS serotypes in relation to anatomical sites (vaginal and rectal) of sample collection, serotype I prevalence at the two sites was consistent with previous findings. 21,23 Surprisingly, serotype V was also frequent at both sites. One possible reason for this discrepancy with other studies may be that most of the previous investigations used conventional serotyping techniques that yielded high rates of untypable strains, possibly including serotype V; this bias in detection probably affected the conclusions regarding the serotypic profile of the study population.…”

“…Serotype VI is rarely described: it had never been reported in Brazil or in other Latin American countries until this day. 3,21,23 The tests currently available for bacterial serotyping, such as the capillary precipitation test developed by Lancefield 20 and latex agglutination, are based on antiserum reactivity against the capsular polysaccharides of the ten known serotypes. However, both tests yield a large proportion of untypable strains, in addition to problems related to their high cost and reproducibility during routine laboratory use.…”

Group B streptococcal carriage among pregnant women and its implications

“…8 A very recent study and first of its kind from Argentina by Oviedo P et al has observed a colonization rate of more than 9% among pregnant women and the serotype Ia was most common isolate. 9 Study performed among Romanian women by Usein CR et al have collected vaginal swabs from 100 subjects and noted that serotypes II (26%), III (26%) and Ia (19%) were more frequently isolated. The same study has also observed that the group B streptococci isolated were most sensitive to penicillin (100%) and ampicillin (100%), chloramphenicol (87%) and least sensitive to tetracycline (5%).…”

Study of Serotypes, Susceptibility to Macrolide and Virulence and Resistance Molecular Profiles in Invasive Strains of <i>Streptococcus agalactiae</i> in Two Argentine Provinces

“…Vaginal colonization rate in pregnant women is not equal between different geographical areas, the data world ranging from 5% to 30% [4], communicating data in the range of 1.4% to 18.15% for Argentina [5]. Published data for Misiones, a province of Argentina, show a colonization rate of 8.6% [6]. About 50% of babies born from these women are colonized with GBS during labor and 1% develop a severe infection [5].…”