Molecular characterization and antimicrobial susceptibility profiles in Streptococcus agalactiae colonizing strains: association of erythromycin resistance with subtype III-1 genetic clone family

Abstract

Knowledge of the epidemiology of Streptococcus agalactiae in Portugal is limited: therefore, the present study aimed to investigate the carriage rate of S. agalactiae among Portuguese women of reproductive age and the prevalence of antibiotic resistance, as well as to perform a molecular characterization of the clinical isolates. S. agalactiae was recovered from 6.2% of 4269 women during the period 2005-2007, with a predominance of capsular genotypes III (35%), V (33%), Ia (16%) and II (10%) in a sample of 100 isolates. To our knowledge, this is the first report of the S. agalactiae colonization rate in Portugal determined according to CDC guidelines. All isolates were susceptible to penicillin and vancomycin, whereas resistance to clindamycin and erythromycin was detected in 10% and 19% of isolates, respectively. Among the 19 erythromycin-resistant isolates, ten (53%) displayed the constitutive MLS B phenotype (conferring highlevel resistance to macrolides), eight (42%) had the inducible MLS B , and the M phenotype accounted for one isolate (5%). erm methylase genes were exclusively associated with MLS B phenotype isolates, whereas the M phenotype was a result of the presence of mefA.Multilocus sequence typing analysis of the genetic relatedness among isolates presenting resistance to erythromycin demonstrated a novel association between erythromycin resistance and the subtype III-1/ST-19 genetic clone family.

Accuracy of prenatal culture in predicting intrapartum group B streptococcus colonization status

“…We observed a resistance rate of 7.4% to erythromycin and 1.8% to clindamycin, which were low when compared to our previous data [3].…”

“…None of the 88 parturients without prior GBS screening revealed intrapartum GBS colonization; however, 9/9 attending to the private hospital and 17/79 attending to public hospitals (the ones presenting risk factors: preterm deliveries [n ¼ 14]; GBS bacteriuria during the current pregnancy [n ¼ 2]; previous child with EOD [ 1/54 [1.9%]), which was quite similar to that described in Portugal for GBS colonization during the last trimester of pregnancy [3]. The lineage ST17 was identified in 56% (14/25) of the isolates belonging to serotype III; however, no newborn developed EOD during hospital stay.…”

“…Capsular typing was performed by using specific antisera for serotypes Ia to V (Essum AB) and cps genotyping [3]. The detection of ST-17 lineage was achieved by PCR, as described elsewhere [8].…”

“…Maternal GBS carriage has been recognized as the major risk factor of early onset disease in newborns (EOD, 57 days of age) [1,2]. Up to 30% of pregnant women are anogenital colonized, although the carrier status is considered dynamic during pregnancy [2,3]. CDC guidelines [2,4] recommend GBS screening at 35-37 weeks of gestation in order to identify women at risk that should undergo intrapartum antibiotic prophylaxis (IAP) to avoid transmission to the newborn during labor; IAP became responsible for the reduction of EOD in developed countries.…”

Epidemiological surveillance of colonising group B Streptococcus epidemiology in the Lisbon and Tagus Valley regions, Portugal (2005 to 2012): emergence of a new epidemic type IV/clonal complex 17 clone

“…Thus, the continuous monitoring of circulating GBS isolates is important in assessing changes in GBS serotype distribution, which is essential for the development of polysaccharide-based vaccines suitable for different geographical areas [4,5]. Serotypes Ia, II, III and V have been the most frequently described in European countries such as the Czech Republic, France, Germany, Greece, Ireland, Italy, the Netherlands, Portugal, Sweden, and the United Kingdom [6], as well as in the United States (US) [7], whereas serotypes VI and VIII, to date scarcely found in these countries, could frequently be identified in Japan [8]. With the exception of a study carried out in Abu Dhabi, United Arab Emirates, where serotype IV predominated among colonised pregnant women (15/57, 26% of the GBS isolates) [9], there are few reports among other countries worldwide of serotype IV as a predominant serotype both in cases of colonisation and infection [6][7][8][10][11][12][13].…”