Prevalence of cefotaxime resistance in group B streptococcus isolates from Osaka, Japan

Molecular characteristics of group B Streptococcus isolates from infants in southern mainland China

BACKGROUND

Invasive group B Streptococcus (GBS) disease in Chinese infants has gradually gained attention in recent years, but the molecular epidemiology of the pathogen is still not well known.

METHODS

This multicenter study retrospectively investigated distribution of capsular serotypes, sequence types (STs), and hypervirulent GBS adhesin gene (hvgA) in clinical GBS isolates that caused invasive disease in infants aged < 3 months of age in southern mainland China between January 2013 and June 2016. Genes for antibiotic resistance to tetracycline, erythromycin, and clindamycin were also examined.

RESULTS

From a total of 93 GBS isolates taken from 34 early-onset disease (EOD, 0-6 days after birth) and 59 late-onset disease (LOD, 7-89 days after birth) cases, four serotypes were identified: serotypes III (79.6%), Ib (12.9%), Ia (4.3%), and V (3.2%). Serotype III accounted for 73.5% of EOD and 83.1% of LOD and was responsible for 75.5% of cases involving meningitis. Fifteen STs were found, with the majority being ST17 (61.3%), ST12 (7.5%), ST19 (7.5%), and others (23.7%). 96.8% of STs belonged to only five clonal complexes (CCs): CC17 (64.5%), CC10 (12.9%), CC19 (9.7%), CC23 (6.5%), and CC1 (3.2%). The hvgA gene was detected in 66.7% of GBS isolates and 95% of CC17 isolates, all of which were serotype III except one serotype Ib/CC17 isolate. A large proportion of GBS isolates were found to be resistant to tetracycline (93.5%), clindamycin (65.5%), and erythromycin (60.2%). Genes of tetO (74.7%) and tetM (46.0%) were found in tetracycline resistant isolates, linB (24.6%) in clindamycin resistant isolates, and ermB (87.5%) and mefA (3.6%) in erythromycin resistant isolates.

CONCLUSION

Our results reveal higher prevalence of serotype III, ST17, CC17, hvgA expressing, and antibiotic resistant GBS isolates than previously reported in southern mainland China. This study provides guidance for appropriate measures of prevention and control to be taken in the future.

Epidemiology of group B streptococcus in Korean pregnant women

Between January 2006 and May 2008, 2624 pregnant S. Korean women between 35–37 weeks gestation were screened for group B streptococcus (GBS). Resistance to antimicrobials was tested by disk diffusion and serotype determined using co-agglutination assays and microarray methods. Overall, 8% of pregnant women were colonized. Serotype III was the predominant serotype (43·8%), followed by serotypes V (20·3%), Ia (12·1%), and Ib (9·5%). GBS was frequently resistant to clindamycin (54·0%) and erythromycin (25·6%); 3·7% were resistant to cefazolin. More than three-quarters of serotype V were resistant to clindamycin or erythromycin or both, and 71% of serotype III were resistant to clindamycin but only 12% were resistant to erythromycin. GBS prevalence exceeded earlier reports by one-third. This is the first report of cefazolin resistance in Korea. These results underscore the need to establish screening measures and chemoprophylaxis guidelines regarding GBS infections in Korea.

Genetic heterogeneity in pbp genes among clinically isolated group B Streptococci with reduced penicillin susceptibility

The recent emergence of group B streptococcal isolates exhibiting increased penicillin MICs at the Funabashi Municipal Medical Center and other hospitals in Japan prompted a comparative analysis of the penicillin-binding proteins (PBPs) from those strains with the PBPs from penicillin-susceptible strains comprising four neonatal invasive strains isolated from 1976 to 1988 and two recent isolates. The PBP sequences of the penicillin-susceptible strains were highly conserved, irrespective of their isolation date. Of six strains with reduced susceptibility to penicillin (penicillin MICs, 0.25 to 0.5 mug/ml), strains R1, R2, R5, and R6 shared a unique set of five amino acid substitutions, including V405A adjacent to the (402)SSN(404) motif in PBP 2X and one in PBP 2B. The remaining two strains, R3 and R4, shared several substitutions, including Q557E adjacent to the (552)KSG(554) motif in PBP 2X, in addition to the substitutions in PBP 2B, which are commonly found among penicillin-insusceptible strains. Strains R7 and R8, which had a penicillin MIC of 1 mug/ml, shared a unique set of eight amino acid substitutions (two in PBP 2X; two in PBP 2B, including G613R adjacent to the (614)KTG(616) motif; three in PBP 1A; and one in PBP 2A), and the Q557E substitution in PBP 2X was common to R3 and R4. The binding of Bocillin FL was reduced or not detected in some PBPs, including PBP 2X of penicillin-insusceptible strains, but no significant reduction in the level of pbp2x transcription was found in such strains. The results of phylogenetic comparative analyses imply the absence of epidemic penicillin-insusceptible strains, and several genetic lineages of penicillin-insusceptible strains have been independently emerging through the accumulation of mutations in their pbp genes, especially in pbp2x.

First molecular characterization of group B streptococci with reduced penicillin susceptibility

Group B streptococci (GBS; Streptococcus agalactiae) are the leading cause of neonatal invasive diseases and are also important pathogens for adults. Penicillins are the drugs of first choice for the treatment of GBS infections, since GBS have been regarded to be uniformly susceptible to penicillins so far. Here we characterize the first strains of GBS with reduced penicillin susceptibility (PRGBS) identified in Japan. Fourteen PRGBS strains were clinically isolated from the sputa of elderly patients from 1995 to 2005; and the MICs of penicillin, oxacillin, and ceftizoxime ranged from 0.25 to 1 microg/ml, 2 to 8 microg/ml, and 4 to 128 microg/ml, respectively. Moreover, some strains were also insusceptible to ampicillin, cefazolin, cefepime, and cefotaxime. All the PRGBS isolates tested possessed a few amino acid substitutions adjacent to the conserved SSN and KSG motifs (amino acids 402 to 404 and 552 to 554, respectively) of PBP 2X, and the amino acid substitutions could be classified into two types, Q557E and V405A. Western blotting analysis of the 14 clinical isolates with anti-PBP 2X-specific serum suggested that the amount of PBP 2X among the 14 PRGBS isolates was reduced, although the 2 ATCC strains produced a significant amount of PBP 2X. The introduction of PRGBS-derived PBP 2X genes into penicillin-susceptible strains through allelic exchange elevated their penicillin insusceptibility, suggesting that these altered PBP 2X genes are responsible for the penicillin insusceptibility in PRGBS strains. In this study, we characterized for the first time PRGBS strains on a molecular basis, although several reports have so far mentioned the existence of beta-lactam-insusceptible GBS from a phenotypic standpoint.

A composite transposon associated with erythromycin and clindamycin resistance in group B Streptococcus

Group B Streptococcus (GBS) resistant to erythromycin and clindamycin has been isolated with increasing frequency since the mid-1990s. This work studied GBS isolates from three US cities to determine the genetic basis of the macrolide resistance phenotype. ermB genes were amplified from five isolates collected in Boston, Pittsburgh and Seattle from infant and adult sources. Gene-walking methods were used to determine the chromosomal location of ermB and to identify associated genes. Southern mapping and random amplified polymorphic DNA (RAPD) analyses were used to distinguish the isolates. The ermB gene was present on the chromosome within a composite Tn917/Tn916-like transposon similar to one identified in Streptococcus pneumoniae. Four strains from Boston and Pittsburgh were serotype V and identical by Southern hybridization and RAPD analysis. The Seattle isolate was serotype Ib, with different patterns on RAPD analysis and Southern mapping. The composite transposon was integrated at an identical chromosomal site in all five isolates. The presence of this composite transposon in both GBS and pneumococci suggests that ermB-mediated macrolide resistance in streptococci may be due to the horizontal transfer of a mobile transposable element, and raises concern for further dissemination of high-grade erythromycin and clindamycin resistance among streptococcal species.

Prolonged fetal bradycardia as the presenting clinical sign in Streptococcus agalactiae chorioamnionitis

Group B Streptococcus remains a leading infectious cause of neonatal morbidity and mortality. We report a case of a 37 weeks' gestation infant with severe birth asphyxia, status epilepticus and GBS chorioamnionitis, in which a prolonged fetal bradycardia was the only prenatal clinical sign.

Clinical microbiology of bacterial and fungal sepsis in very-low-birth-weight infants

Twenty percent of very-low-birth-weight (<1500 g) preterm infants experience a serious systemic infection, and despite advances in neonatal intensive care and antimicrobials, mortality is as much as threefold higher for these infants who develop sepsis than their counterparts without sepsis during their hospitalization. Outcomes may be improved by preventative strategies, earlier and accurate diagnosis, and adjunct therapies to combat infection and protect the vulnerable preterm infant during an infection. Earlier diagnosis on the basis of factors such as abnormal heart rate characteristics may offer the ability to initiate treatment prior to the onset of clinical symptoms. Molecular and adjunctive diagnostics may also aid in diagnosing invasive infection when clinical symptoms indicate infection but no organisms are isolated in culture. Due to the high morbidity and mortality, preventative and adjunctive therapies are needed. Prophylaxis has been effective in preventing early-onset group B streptococcal sepsis and late-onset Candida sepsis. Future research in prophylaxis using active and passive immunization strategies offers prevention without the risk of resistance to antimicrobials. Identification of the differences in neonatal intensive care units with low and high infection rates and implementation of infection control measures remain paramount in each neonatal intensive care unit caring for preterm infants.

In vitro activities of DA-7867, a novel oxazolidinone, against recent clinical isolates of aerobic and anaerobic bacteria

In vitro activities of DA-7867, a novel oxazolidinone, were compared to those of linezolid and commonly used antimicrobials. DA-7867 had the lowest MIC for 90% of the aerobic gram-positive bacterial strains tested, </=0.25 micro g/ml, and it was more potent than linezolid.