Despite the necessity for studies of group B streptococci (GBS), due to the increase in serious adult infections, the emergence of new serotypes, and the increased resistance to macrolide antibiotics, such studies have been limited in Korea. The primary purpose of the present study was to determine the frequency trends of GBS serotypes, including serotypes VI, VII, and VIII. The final objective was to elucidate the relationship between the genotypes and serotypes of macrolide-resistant GBS isolates from a Korean population. Among 446 isolates of Streptococcus agalactiae, isolated between January 1990 and December 2002 in Korea, the frequency of serotypes were III (36.5%), Ib (22.0%), V (21.1%), Ia (9.6%), VI (4.3%), II (1.8%), VIII (1.3%), IV (1.1%), and VII (0.9%). The resistance rates to erythromycin, by serotype, were 85% (V), 23% (III), 21% (VI), 3% (Ib), and 2% (Ia). Of 135 erythromycin- resistant S. agalactiae, ermB was detected in 105 isolates, mefA in 20 isolates, and ermTR in seven isolates; most type V isolates harbored the ermB gene, Ib type isolates had an equal distribution of resistance genes, type III isolates accounted for 70% of all isolates carrying mefA genes, and one fourth of type VI isolates had mefA genes.
Anti-Bacterial Agents/*pharmacology ; Drug Resistance, Bacterial ; Erythromycin/*pharmacology ; Genotype ; Serotyping ; Streptococcus agalactiae/*classification/*drug effects/genetics

PURPOSE: Erythromycin-resistant beta-hemolytic streptococci (BHS) has recently emerged and quickly spread between and within countries throughout the world. In this study, we evaluate the antimicrobial susceptibility patterns and erythromycin resistance mechanisms of BHS during 2003-2004. MATERIALS AND METHODS: The MICs of seven antimicrobials were determined for 204 clinical isolates of BHS from 2003 to 2004. Resistance mechanisms of erythromycin-resistant BHS were studied by the double disk test as well as by polymerase chain reaction (PCR). RESULTS: Compared with our previous study, resistance among Streptococcus pyogenes isolates to a variety of drugs decreased strikingly: from 25.7% to 4.8% in erythromycin; 15.8% to 0% in clindamycin; and 47.1% to 19.0% in tetracycline. The prevalent phenotypes and genotypes of macrolide-lincosamide-streptograminB (MLSB) resistance in Streptococcus pyogenes isolates have been changed from the constitutive MLSB phenotype carrying erm(B) to the M phenotype with mef(A) gene. In contrast with Streptococcus pyogenes, resistance rates to erythromycin (36.7%), clindamycin (43.1%), and tetracycline (95.4%) in Streptococcus agalactiae isolates did not show decreasing trends. Among the Streptococcus dysgalactiae subsp. equisimilis isolates (Lancefield group C, G), resistance rates to erythromycin, clindamycin, tetracycline and chloramphenicol were observed to be 9.4%, 3.1%, 68.8%, and 9.4%, respectively. CONCLUSION: Continual monitoring of antimicrobial resistance among large-colony-forming BHS is needed to provide the medical community with current data regarding the resistance mechanisms that are most common to their local or regional environments.
Anti-Bacterial Agents/*pharmacology ; Drug Resistance, Multiple, Bacterial ; Erythromycin/*pharmacology ; Genes, Bacterial ; Genotype ; Hospitals ; Humans ; Incidence ; Korea ; Microbial Sensitivity Tests ; Streptococcus/*drug effects/genetics/isolation & purification ; Streptococcus agalactiae/drug effects/genetics/isolation & purification ; Streptococcus pyogenes/drug effects/genetics/isolation & purification

This study evaluated the antimicrobial susceptibilities and macrolide resistance mechanisms of beta-hemolytic streptococci (BHS), and an additional objective was to assess the effects of 'the separation of prescribing and dispensing (SPD) of medications' on bacterial resistance rate and distribution of phenotypes and genotypes of erythromycin-resistant BHS by comparing the antimicrobial susceptibility data before (1990- 2000) and after the implementation of SPD at one tertiary care hospital in South Korea. Between the period of January 2001 and December 2002, the minimal inhibitory concentrations of six antimicrobials were determined for 249 clinical isolates of BHS. Resistance mechanisms of erythromycin-resistant (intermediate and resistant) isolates were studied by using the double disk test and PCR. Overall, the resistance rates to tetracycline, erythromycin, and clindamycin were 75.5%, 32.9%, and 32.5%, respectively. Sixty-seven (81.7%) of 82 erythromycin- resistant isolates expressed constitutive resistance to macrolide- lincosamide-streptogramin B antibiotics (a constitutive MLSB phenotype) ; 11 isolates (13.4%) expressed an M phenotype; and four isolates (4.9%) had an inducible MLSB resistance phenotype. erm (A) was found in isolates with constitutive/ inducible MLSB phenotypes, erm (B) with the constitutive/ inducible MLSB phenotype, and mef (A) with the M phenotype. We found that resistance rates to erythromycin and clindamycin among S. agalactiae, S. pyogenes, and group C streptococci isolates were still high after the implementation of the SPD policy in Korea, and that the constitutive MLSB resistance phenotype was dominant among erythromycin- resistant BHS in this Korean hospital.
Anti-Bacterial Agents/*therapeutic use ; Cross Infection/drug therapy ; Drug Resistance, Bacterial ; Erythromycin/*therapeutic use ; Genotype ; Humans ; Korea ; Microbial Sensitivity Tests ; Phenotype ; Streptococcal Infections/*drug therapy ; Streptococcus agalactiae/*drug effects/genetics ; Streptococcus pyogenes/*drug effects/genetics

OBJECTIVETo test the antibiotic susceptibility and study mechanisms of macrolide resistance in group B streptococcus isolates (GBS).

METHODSThe GBS investigated in this study included 140 and 47 colonizing strains isolated from vaginal or cervical swabs from pregnant women in Beijing (from 1994 to 1999) and Guangzhou obstetrics and gynecology hospitals (from 1999) and 6 invasive strains isolated from infants in Beijing Children's Hospital. Susceptibility to ampicillin, penicillin G, erythromycin, lincomycin, cephazolin, cefuroxime, cefoperazone was assessed by K-B disc diffusion. The mechanisms, methylation or efflux, of macrolide resistant GBS isolates, were analyzed by PCR for ermB and mefA genes.

RESULTSSusceptibility testing revealed that none of the GBS isolates were resistant to beta-lactam drugs, but 17% isolates showed intermediate susceptibility to penicillin G and ampicillin. The rate of erythromycin resistance increased from 8% in 1998 to 16% in 1999 in Beijing, while the rate of lincomycin resistance increased from 20% to 28% in that period. However, 21 (45%) and 12 (26%) isolates were resistant to erythromycin and lincomycin, respectively in Guangzhou city where erythromycin resistance rate was higher than that in Beijing. Of 45 erythromycin resistant isolates, 20 (20/45, 44%) possessed the ermB gene and 13 (13/45, 29%) harbored the mefA gene; 6 isolates harbored both genes, 6 isolates had possessed neither ermB gene nor mefA gene.

CONCLUSIONThe susceptibility of GBS isolates to penicillin G and ampicillin suggests use of penicillin G or ampicillin as a first-line drug in prophylactic treatment regimes against early-onset neonatal GBS disease. Erythromycin and lincomycin should not be recommended as the second-line antimicrobial in Beijing and Guangzhou city. The clinical relevance of macrolide resistant GBS in women treated with macrolides for intrapartum prophylaxis needs to be assessed. Ribosomal modification by a methylase encoded by erm gene may play a major role in the mechanisms of macrolide resistance of GBS isolates in China.

Anti-Bacterial Agents ; pharmacology ; Cervix Uteri ; microbiology ; China ; Drug Resistance, Multiple, Bacterial ; genetics ; Female ; Humans ; Infant ; Macrolides ; pharmacology ; Microbial Sensitivity Tests ; Pregnancy ; Streptococcus agalactiae ; drug effects ; genetics ; Vagina ; microbiology