Distribution of genotypes and antibiotic resistance genes among invasive Streptococcus agalactiae (group B streptococcus) isolates from Australasian patients belonging to different age groups

Abstract

Serotype distribution and antibiotic resistance (AR) among group B streptococci (GBS) affect GBS disease prevention strategies, but vary among patient groups. A multiplex PCR-based reverse line blot (mPCR/RLB) hybridisation assay was used to compare the distributions of GBS serotypes, serotype III subtypes and AR-associated genes among 666 invasive isolates from 663 patients, divided into five age groups: infants, early-onset (EO; 0-6 days) and late-onset (LO; 7-90 days); children (aged 3 months to 14 years); women of childbearing age (WCBA; aged 15-45 years); and other adults (males aged >15 years; females aged >45 years). Serotypes Ia and V and serosubtype III-1 accounted for 60% of infections. Serosubtype III-2, which corresponds to a virulent clone belonging to sequence type (ST)17, was relatively uncommon overall (7%), but was associated strongly with LO infant infections, in which it was significantly more common than in adult infections (25/104 (24%) vs. 9/392 (2%), p <0.0001) or in EO infections (25/104 (24%) vs. 14/155 (9%), p <0.005). Erythromycin resistance genes were found in 8% of all isolates (ermB 3%, ermA 2.5% and mefA/E 2%), in 11-15% of isolates of serotypes II and V and subtype III-1, but in none of the isolates of serosubtype III-2 (III-2, 0/49 vs. all others, 54/618 (9%), p <0.04). In summary, the virulent serosubtype III-2 was associated strongly with LO infant GBS infection, but was less likely than other serotypes or serosubtype III-1 to carry AR genes.

Serotypes and antibiotic resistance in Group B streptococcus isolated from patients at the Maternity Hospital, Kuwait

“…With regard to the distribution of resistance determinants among GBS serotypes, the common resistance genotypes, tetM and aph3, were widely distributed across serotypes, with the majority of the isolates belonging to serotype V, in agreement with observations reported by Zhao et al (2008). In contrast to the findings in our study, Zeng et al (2006) reported aph3 mostly in serotype III but not in serotype V isolates.…”

“…Most of the erythromycin-resistant GBS isolated in our study (Table 3) contained ermB or ermTR. Other studies have also reported high prevalence of ermB among macrolide-resistant GBS isolates (Betriu et al, 2003;Diekema et al, 2003;Zhao et al, 2008), and ermTR was the most common macrolideresistance determinant in the USA and Canada, followed by ermB (de Azavedo et al, 2001;Dogan et al, 2005). The low prevalence of mef genes in the Kuwaiti GBS isolates is similar to those reported by others (Aracil et al, 2002;de Azavedo et al, 2001).…”

“…However, unlike kanamycin resistance, high-level streptomycin resistance was detected in only 3.5 % of the isolates in the present study, and only one of these isolates was positive for ant6, suggesting that streptomycin resistance in the ant6-negative isolates was due to other resistance mechanisms. Similarly, Poyart et al (2003) reported low prevalence of high-level streptomycin resistance in GBS isolates.With regard to the distribution of resistance determinants among GBS serotypes, the common resistance genotypes, tetM and aph3, were widely distributed across serotypes, with the majority of the isolates belonging to serotype V, in agreement with observations reported by Zhao et al (2008). In contrast to the findings in our study, Zeng et al (2006) reported aph3 mostly in serotype III but not in serotype V isolates.…”

“…In comparison to what was previously reported for GBS isolates (Poyart et al, 2003;Zeng et al, 2006;Zhao et al, 2008), we detected a higher proportion of isolates (76.9 %) resistant to high-level kanamycin. It is uncertain whether this observation represents a new development in Kuwait or a new awareness of a previously existing problem, since high-level kanamycin resistance was not assessed in our previous evaluation (Al-Sweih et al, 2005a).…”

“…As serotype V GBS isolates have become the predominant GBS serotype causing invasive infections in adult patients and neonates in the USA and Canada (Castor et al, 2008;Dogan et al, 2005), Australia and New Zealand (Zhao et al, 2008), the predominance of serotype V among Kuwaiti women may be considered an emerging public health concern. Curiously, our results differed from those reported for pregnant women in neighbouring countries such as the United Arab Emirates, where serotype IV (26.3 %) was the most common serotype among GBS isolates (Amin et al, 2002), or Iran, where serotype III (41.8 %) was the most common serotype (Mansouri et al, 2008).…”