A Serotype V Clone Is Predominant among Erythromycin-Resistant Streptococcus agalactiae Isolates in a Southwestern Region of Germany

Abstract

One hundred ninety-three Streptococcus agalactiae isolates of neonatal origin and 146 isolates from adult women were analyzed for macrolide resistance and investigated for clonality. Among erythromycin-resistant isolates, serotype V turned out to be the most frequent. Comparative pulsed-field gel electrophoresis analysis revealed genetic clustering of resistant strains and predominance of a single clone family within an otherwise heterogeneous serotype V population. [GBS]) is the leading cause of meningitis and early-onset sepsis in neonates (3,21). Penicillin or ampicillin is the drug of choice for prophylaxis and treatment of GBS disease (1, 5). However, erythromycin and clindamycin are the recommended second-line drugs and the first alternative in case of a ␤-lactam allergy. In recent years, increasing macrolide resistance rates have been reported (9,15,16,17,19). Resistance mechanisms include target site modification mediated by erm genes leading to resistance to macrolides-lincosamides-streptogramin B (MLS phenotype) with either inducible or constitutive expression or an efflux mechanism encoded by mef genes mediating resistance only to 14-and 15-membered macrolides (M phenotype). After the first description of serotype V in 1977 (26), several studies reported a major increase of serotype V GBS among clinical isolates in the early 1990s (8,13). To analyze the recent increase in macrolide resistance among GBS isolates in our region, the present study aimed to explore the issue of a clonal spread of resistant strains by means of randomly amplified polymorphic DNA (RAPD) analysis and restriction digest patterns (RDP) derived from pulsed-field gel electrophoresis (PFGE). Moreover, a possible correlation between the increase of a certain serotype and macrolide resistance was explored. Streptococcus agalactiae (group B StreptococcusThe bacterial strains used in this study have been presented previously (20). In brief, of 193 neonatal GBS strains, 26 invasive isolates were cultured from blood or cerebrospinal fluid while 167 isolates were grown from urine samples and swab cultures. A total of 146 GBS isolates from vaginal swabs of pregnant women were randomly collected. Serotyping was performed by using an enzymatic extraction method (2). All erythromycin-resistant isolates were screened by PCR analysis for erythromycin resistance genes (mefA or mefE, ermB, and ermTR) by using primers previously described (7,23,24). PCR assays were reproducibly repeated at least three times for every strain. Differentiation of specific MLS phenotypes was performed by use of a triple-disk test (10). For RAPD analysis, the core sequence of phage M13 and the previously described primer OPS16 were used (6, 12) and visual inspection of bands served to compare RAPD patterns for similarity. Different isolates with the same migration distances of all visible bands were considered highly similar. The presence or absence of two distinct bands was deemed to indicate a difference. Chromosomal DNA of GBS strains was prepared by modifications o...

Serotypes and Genotypes of Erythromycin-Resistant Group B Streptococci in Korea

“…The rates of resistance to erythromycin found among our serotypes, in decreasing order, were 76% (V), 50% (IV), 28% (III), 20% (II), 19% (NT), 4% (Ia), and 2% (Ib). These results were consistent with those of other reports (11,15,21), suggesting a relationship between erythromycin resistance and serotype. In contrast, Ko et al (13) reported that serotype Ib isolates had a lower rate of susceptibility to erythromycin than did serotype Ia, III, or V isolates.…”

“…Serotyping has been used as an epidemiological tool to explain GBS infections because the distribution of GBS serotypes is associated with patient type and the site of infection and the prevalent serotype may also change with time (4,13,14,20). Over the past decade, several investigators have reported that an increasing proportion of GBS disease is due to serotype V (1,4,8,21). In addition, several reports have documented an association between macrolide resistance and GBS serotype V (4,7,10,20).…”

“…The distribution of MLS B resistance genes of GBS is influenced by geographical variation and serotypes (3,6,11,21). The predominant MLS B resistance gene of GBS was ermB in Spain (3), France (11), and Germany (21), whereas ermTR was prevalent in Canada (6).…”

Association between capsular serotype V and macrolide resistance in group B Streptococcus

“…This is in line with previous findings in the Asia, Europe and the United States (Table 1 [ [6][7][8][9][10][11][12][13][14][15][16][17][18][19]). In the study by Morozumi et al [2], 7/32 (21·9%) serotype Ia and 24/88 (27·3%) serotype III GBS isolates showed ML resistance.…”

Molecular Epidemiology and Distribution of Serotypes, Surface Proteins, and Antibiotic Resistance among Group B Streptococci in Italy

“…Other studies have also identified serotype V GBS isolates associated with erythromycin resistance (10,26,41). Moreover, a study from Korea showed that the most prevalent serotype of the erythromycinresistant GBS strains examined was type V, with all the isolates harboring the erm(B) gene (40).…”