Pulsed-field gel electrophoresis, virulence determinants and antimicrobial susceptibility profiles of type Ia group B streptococci isolated from humans in Brazil

Abstract

Group B streptococci (GBS) infections occur worldwide. Although serotyping has been used for epidemiologic purposes, this does not accurately characterize enough members of a genetically heterogeneous bacterial population. The aims of this work were to evaluate the genetic diversity of 45 type Ia GBS strains isolated in Brazil byGroup B streptococci (GBS) are responsible for a large variety of human infections and have been recognized over the last few decades as a leading cause of perinatal disease worldwide (Farley 2001, Weisner et al. 2004. GBS are classified in serotypes (Ia, Ib and II-VIII) that occur in combination with different protein antigens (alpha, beta and rib) (Dmitriev et al. 2001). Currently, serotypes Ia, III and V are the most common in many countries (Duarte et al. 2005, Fluegge et al. 2005, Bergseng et al. 2008, Poyart et al. 2008, von Both et al. 2008.Pulsed-field gel electrophoresis (PFGE), used to examine GBS strains, is a powerful technique employed for the classification of microorganisms after digestion of the genomic DNA by restriction enzymes (Benson & Ferrieri 2001, Oliveira et al. 2005, von Both et al. 2008. Using polymerase chain reaction (PCR), Franken et al. (2001) suggested that the scpB and lmb genes (encoding c5a peptidase and laminin binding protein) must exist in GBS strains that infect humans. The hylB gene is frequently detected in these strains (Dore et al. 2003). The bac and bca genes are present in 23% and 100% of type Ia strains, respectively (Maeland et al. 1997(Maeland et al. , 2000.The lack of information on Ia Brazilian strains and the availability of DNA techniques led us to investigate the genetic make-up of type Ia GBS strains isolated in distinct regions of Brazil. Additionally, antimicrobial susceptibility was examined to better characterize these isolates. MATERIALS AND METHODSBacterial strains -Forty-five human type Ia GBS strains derived from clinical specimens were obtained in Florianopolis, Santa Catarina (n = 3), a city located in the Southern Region of Brazil, in São Paulo, São Paulo (SP) (n = 1), and in Rio de Janeiro, Rio de Janeiro (n = 40), in the Southeast Region of the country. The source of one strain was unknown.Isolates were obtained from 1981-2002 from public health laboratories, gynaecological clinics, hospitalsand universities. The clinical sources included urine (n = 16), oropharynx (n = 9), vagina (n = 5), anus (n = 2), lung (n = 2), placenta (n = 1), external ear canal (n = 1) and perineum (n = 1). The sources of eight specimens were unknown. A confirmatory identification of serotypes was carried out again by immunoprecipitation in agarose using sera produced in the research facilities of the authors and HCl antigenic extracts from the streptococci (Benchetrit et al. 1982).PFGE -PFGE was performed as previously described (Oliveira et al. 2005). DNA was digested with the SmaI restriction enzyme (Amersham) and submitted to electrophoresis with a program as follows: switch time of 1-30 sec during 23 h, with a 120º angle, at a temperature of ...

Streptococcus agalactiae in Brazil: serotype distribution, virulence determinants and antimicrobial susceptibility

“…The uniform susceptibility of GBS to beta-lactam antibiotics detected in this study is consistent with previously published data on S. agalactiae isolates in Brazil [10-15,30], as well as in several regions in the world [8,25]. However, an extensive network national surveillance should be implemented since isolates with reduced susceptibility to penicillin have been described in various regions of the world [16-18].…”

“…The presence of the bac, bca, lmb and scpB genes, which encode for alpha and beta proteins, laminin binding protein, and C5a peptidase, respectively, was evaluated in all 434 isolates by PCR using previously described primers [29,30]. …”

Molecular epidemiology of Streptococcus agalactiae isolated from mastitis in Brazilian dairy herds

“…This discrepancy can be explained by the replacement of this gene by other adhesion factors, such as proteins encoded by fbsB and other genes that were not screened in this study. The detection of hylB here was similar to that by other researchers in both human and bovine strains, but distinct from fish strains, suggesting that this gene might be related to mammalian hosts 8, 21, 27. Furthermore, the frequency of the bac gene was similar to that previously described in bovine strains 27, 46, 50.…”

“…The detection of hylB here was similar to that by other researchers in both human and bovine strains, but distinct from fish strains, suggesting that this gene might be related to mammalian hosts 8, 21, 27. Furthermore, the frequency of the bac gene was similar to that previously described in bovine strains 27, 46, 50. Perhaps during the infectious process in bovines, the S. agalactiae strains use other surface-associated proteins that were not screened here.…”

“…Virulence genes were detected by performing PCR screening for the genes bac , bca , bibA , cfb , hylB , fbsA , fbsB , PI-1, PI-2a, and PI-2b, as described previously 21, 27, 28, 29. All the primers used in this study and their respective references can be accessed in supplementary material 2.…”