Group B Streptococcus in a General Hospital

171

159

Macrolide resistance has been demonstrated in group B streptococcus (GBS), but there is limited information regarding mechanisms of resistance and their prevalence. We determined these in GBS obtained from neonatal blood cultures and vaginal swabs from pregnant women. Of 178 isolates from cases of neonatal GBS sepsis collected from 1995 to 1998, 8 and 4.5% were resistant to erythromycin and clindamycin, respectively, and one isolate showed intermediate penicillin resistance (MIC, 0.25 g/ml). Of 101 consecutive vaginal or rectal/vaginal isolates collected in 1999, 18 and 8% were resistant to erythromycin and clindamycin, respectively. Tetracycline resistance was high (>80%) among both groups of isolates. Of 32 erythromycin-resistant isolates, 28 possessed the erm methylase gene (7 ermB and 21 ermTR/ermA) and 4 harbored the mefA gene; one isolate harbored both genes. One isolate which was susceptible to erythromycin but resistant to clindamycin (MIC, 4 g/ml) was found to have the linB gene, previously identified only in Enterococcus faecium. The mreA gene was found in all the erythromycin-resistant strains as well as in 10 erythromycin-susceptible strains. The rate of erythromycin resistance increased from 5% in 1995-96 to 13% in 1998-99, which coincided with an increase in macrolide usage during that time.Group B streptococcus (GBS), although a normal commensal of the gastrointestinal and genitourinary tracts, is capable of causing invasive infections in neonates, pregnant women, and persons with underlying medical conditions (26). Between 15 and 35% of pregnant women are asymptomatic carriers of GBS, and in the early 1990s 0.2 to 0.8% of neonates had GBS bacteremia (26).

Section: Discussionsupporting

confidence: 66%

Prevalence and Mechanisms of Macrolide Resistance in Invasive and Noninvasive Group B Streptococcus Isolates from Ontario, Canada

Azavedo

McGavin

Duncan

et al. 2001

171

159

“…Group B streptococci are important human pathogens, particularly in the neonatal period (2,3,10,30,31). Serotype Ib streptococci are most frequently associated with septicemia occurring in the first few days after birth (2,10,30,31).…”

mentioning

confidence: 99%

“…Serotype Ib streptococci are most frequently associated with septicemia occurring in the first few days after birth (2,10,30,31). Infections with these bacteria have high mortality rates, even with the prompt application of chemotherapy (4,10).…”

mentioning

confidence: 99%

Hypersusceptibility of penicillin-treated group B streptococci to bactericidal activity of human polymorphonuclear leukocytes

Horne¹,

Tomasz²

1981

Pretreatment of serotype Ib group B streptococci with benzylpenicillin, other beta-lactam antibiotics, or vancomycin increased the susceptibility of these bacteria to the bactericidal activity of a mixture of human polymorphonuclear leukocytes and normal human serum. Increased susceptibility of the bacteria to killing by phagocytes was elicited even by exposure to subinhibitory levels of the beta-lactam antibiotics. Inhibitors of protein synthesis did not induce such susceptibility. We investigated the possible biochemical basis of penicillin-induced susceptibility to phagocytosis. Penicillin treatment induced the release of substantial quantities of group B streptococcal surface components into the growth medium (lipoteichoic acid, lipid, and capsular polysaccharide). Labeling of the live streptococci with 3H-labeled penicillin was used to evaluate the effect of exposure to subinhibitory concentrations of this antibiotic on the penicillin-binding proteins. Our results suggested that beta-lactam antibiotics and components of the immune system may act in concert to eliminate invading bacteria.

“…Strains of group B Streptococcus have become increasingly fiequent isolates from neonates and infants with serious bacterial infection during the past decade (1,2,4,8). Because this microbial species has previously been noted to be uniformly susceptible to the penicillins (7,9), penicillin G has been the recommended drug of choice for the treatment of group B streptococcal infections (3,7).…”

mentioning

confidence: 99%

Antimicrobial Susceptibility of Group B Streptococci Isolated from a Variety of Clinical Sources

Baker

Webb²,

Barrett³

1976

The minimal inhibitory concentration of 10 antibiotics for 244 isolates of group B streptococci was determined. Susceptibility to penicillin G, ampicillin, cephalothin, chloramphenicol, and carbenicillin was uniform. Tetracycline and bacitracin resistance among these isolates was frequent (87.5 and 97.9%, respectively). Three strains (1.2%) failed to be inhibited by 100 μg of lincomycin or clindamycin per ml. Susceptibility of these 244 strains to the agents tested was unrelated to source of the isolate, year of isolation, or strain serotype. No apparent change in the suceptibility of group B streptococci to penicillin G has occurred during the past 2 decades.