Genotyping of erythromycin resistant group C & G streptococci isolated in Chennai, south India.

Background & objectives: Increasing resistance to erythromycin has been observed worldwide in group C and group G streptococci (GCS/GGS). The information available from India is scanty. The aim of the study was to identify erythromycin resistant GCS/GGS isolates in Chennai, south India, and to compare erythromycin resistant genotypes with emm types. Methods: One hundred and thirty one GCS/GGS isolates were tested for erythromycin resistance by disc diffusion and agar dilution methods. Erythromycin resistance genotypes [erm(A), erm(B) and mef(A)] were determined by a multiplex PCR. emm types of erythromycin resistant GCS/GGS isolates was also assessed using emm gene sequencing method. Results: Sixteen of the 131 isolates (12.21%) were resistant to erythromycin. Majority of the isolates were GGS (15/16). Eight of the 16 (50%) were S. dysgalactiae subsps. equisimilis. Twelve isolates (75%) were MLSB phenotype and four (25%) were M phenotype. Of the 12 isolates which exhibited MLSB resistance, seven showed cMLSB phenotype and were positive for erm(B) gene. The remaining five were iMLSB phenotype of which three were positive for erm(A) gene and two for erm(B) gene. erm(A) was common among carriers whereas erm(B) was common among clinical isolates. Interpretation & conclusions: MLSB was the predominant phenotype and erm(B) was the common genotype in the present study. The emm type stC1400.0 was frequently associated with erythromycin resistant GCS/GGS in our study.

Antimicrobial Susceptibility Patterns and Macrolide Resistance Genes of beta-Hemolytic Viridans Group Streptococci in a Tertiary Korean Hospital

The aim of this study was to investigate antimicrobial susceptibilities and macrolide resistance mechanisms of beta-hemolytic viridans group streptococci (VGS) in a tertiary Korean hospital. Minimum inhibitory concentrations (MICs) of seven antimicrobials were determined for 103 beta-hemolytic VGS isolated from various specimens. The macrolide resistance mechanisms of erythromycin-resistant isolates were studied by the double disk test and polymerase chain reaction (PCR). The overall resistance rates of beta-hemolytic VGS were found to be 47.5% to tetracycline, 3.9% to chloramphenicol, 9.7% to erythromycin, and 6.8% to clindamycin, whereas all isolates were susceptible to penicillin G, ceftriaxone, and vancomycin. Among ten erythromycin-resistant isolates, six isolates expressed a constitutive MLSB (cMLSB) phenotype, and each of the two isolates expressed the M phenotype, and the inducible MLSB (iMLSB) phenotype. The resistance rates to erythromycin and clindamycin of beta-hemolytic VGS seemed to be lower than those of non-beta-hemolytic VGS in our hospital, although cMLSB phenotype carrying erm(B) was dominant in beta-hemolytic VGS.

Erythromycin Resistance Phenotype and Resistance Gene to Streptococcus pneumoniae / 中华医院感染学杂志

OBJECTIVE To investigate the prevalence of erythromycin resistance genes ermB and mefA and the relationship of drug resistance and genes in Streptococcus pneumoniae.METHODS Forty three strains of S. pneumoniae were collected from respiratory system infected children from Dec 2004 to Oct 2005 at Yuying Pediatric Hospital of Wenzhou Medical College.Erythromycin sensitivity test was done by using MIC method.The erythromycin resistance genes ermB and mefA were detected by PCR.RESULTS In all forty three strains,forty were erythromycin resistant(93%),three were erythromycin sensitive.The total detection rate of erythromycin resistance genes ermB and mefA was 76.7% and 23.3%,respectively.There were neither gene ermB nor gene mefA in 3 erythromycin-sensitive S.pneumoniae.In 40 strains the detection rate of gene ermB was 82.5% and that of gene mefA was 25%.The erythromycin resistance gene ermB or mefA were detected in 35 of the 43 strains.The total detection rate of erythromycin resistance gene was 81.4%.In the 35 erythromycin resistance strains there were 25 strains in which gene ermB existed lonely and 2 strains in which gene mefA existed lonely.There were both genes ermB and gene mefA in 8 of the 35 erythromycin resistance strains.CONCLUSIONS The erythromycin resistance of S.pneumoniae can be caused mainly by gene expression of ermB or mefA,but the gene mefA seems to be less important than gene ermB.Obviously the erythromycin isn′t useful in treating S.pneumoniae infection.

A Decrease in Erythromycin Resistance Rate of Streptococcus pyogenes in 2004 in Jinju / 대한임상미생물학회지

BACKGROUND: The erythromycin (EM) resistance rates and emm genotypes of Streptococcus pyogenes could vary by geographical location and study period. The purpose of this study, involving a large number of children, was to determine EM resistance rate and its resistance mechanism of S. pyogenes, and to compare these results with those of previous studies performed at the same area. METHODS: Throat cultures were taken from 2,351 healthy children of four elementary schools from October through December, 2004 in Jinju. A total of 328 strains of S. pyogenes were isolated. Antimicrobial susceptibility test was performed by the agar dilution method against six antimicrobial agents. The phenotypes of EM resistance were evaluated by the double-disk diffusion test and the frequency of ermB and mefA genes was determined by polymerase chain reaction. RESULTS: Resistance rates of S. pyogenes to EM, clindamycin and tetracycline were 9.8%, 8.8% and 18.3%, respectively. Almost all isolates were susceptible to ofloxacin, levofloxacin and chloramphenicol. Constitutive resistance (CR) was observed in 87.5%, M phenotype in 9.4%, and inducible resistance only in 3.1%. The ermB and mefA genes were present in 90.6% and 9.4% of the isolates, respectively. CONCLUSION: The resistance rate to EM of S. pyogenes was 9.8% in 2004, which was a large drop from the 51% shown in 2002. CR with the ermB gene was predominant, suggesting that most of the EM resistant isolates have a high level of resistance.

Analysis of Phenotypic and Genotypic Distribution of Erythromycin and Clindamycin Resistance of Group A Streptococci Isolated from Acute Pharyngitis / 대한진단검사의학회지

BACKGROUND: Erythromycin (EM) or other macrolides have been used commonly for the treatment of bacterial pharyngitis. Recently, however, EM-resistant group A streptococci (GAS) are being reported with increasing frequency. The phenotypic expression of macrolide resistance is classified as constitutive, inducible, and M. EM resistance is mediated by ermB, ermTR, or mefA genes. The emm gene encoding M protein has variable sequences at 5'end terminus. METHODS: GAS was isolated from patients with acute pharyngitis at a local clinic in Jinju from November 2001 to May 2002. Antimicrobial susceptibility testing was performed using the disk diffusion method. The phenotypes of EM and clindamycin (CC) resistance were evaluated, and the frequency of ermB and mefA genes was determined by PCR. The emm genotype was identified with PCR and sequencing. RESULTS: A total of 125 strains of group A streptococci was isolated. The resistance rate to EM and CC was 44.8% and 19.2%, respectively. Constitutive resistance was observed in 42.1%, M phenotype in 57.9%, but inducible resistance was not seen. The ermB and mefA genes were positive in 39.3% and 58.9%, respectively. Most emm12 strains showed constitutive resistance, while emm18 and emm75 showed M phenotype. CONCLUSIONS: The EM and CC resistance rates of group A streptococci isolated from acute pharyngitis were remarkably high compared to the previous reports. M phenotype was more common than constitutive resistance in acute pharyngitis. The resistance pattern was variable according to the emm types, suggesting an association between the emm gene and resistant genes.

Antibiotic Resistance and Its Mechanism of Group A Streptococci in School Children of Jinju / 대한임상미생물학회지

BACKGROUND: Group A streptococci (GAS) is the most common cause of bacterial pharyngitis. Recently, a high frequency of resistance to erythromycin (EM), the drug of choice for penicillin-allergic patients, has been reported, especially in countries where antibiotics are overused. Resistance is classified as constitutive, inducible, or M according to the sensitivity results with EM and clindamycin (CC). These EM resistance phenotype is attributable to the erm , ermTR, and mefA genes, respectively. Although EM resistance of GAS is a serious problem in our country, there are very few reports regarding to its mechanism. METHODS: GAS were isolated from elementary school children of Jinju in 2002. Antibiotic sensitivity testing by disk diffusion was performed against tetracycline (TC), ofloxacin, EM and CC, and the results were compared to the previous one in 1995 at the same area. The phenotypes of EM resistance were evaluated, and the frequency of ermB and mefA genes was determined by PCR. The resistance pattern was analyzed by each emm genotype. RESULTS: The resistance rate to EM and CC was 51% and 34%, respectively, which is significantly higher than the rate of 25% and 9% recorded in 1995. Constitutive resistance was seen in 64% of the EM-resistant strains, the M phenotype in 34%, and inducible resistance in only 2%, compared to 38% of constitutive resistance and 62% of M phenotype in 1995. The ermB and mefA genes were present in 64% and 34% of strains, respectively. Most (88%) of the emm12 strains showed constitutive resistance, while emm18 and emm75 showed M phenotype. The organisms with most of the other emm genotypes were susceptible to EM. CONCLUSION: The EM and CC resistance rate had increased more than twofold. Constitutive resistance was twice as common as the M phenotype, whereas the mefA gene was more common in 1995. The resistance pattern was variable according to emm type, which suggests an association between the emm and resistance genes. Continuous microbiologic and epidemiological surveillance should be conducted and the seriousness of antibiotic resistance should be underscored in our community.

Distributions of Macrolide-Lincosamide-Streptogramin (MLS) Resistance Types in beta-hemolytic Streptococci / 대한임상미생물학회지

BACKGROUND: Macrolide resistance in beta-hemolytic streptococci has increased during the 1990s, and the proportion of MLS (Macrolide-lincosamide-streptogramin) resistance phenotypes and genotypes of beta-hemolytic streptococci are quite different by geographical variation and study period. The aim of the present study was to determine the distribution of MLS resistance phenotypes and genotypes in beta-hemolytic streptococci isolated from Wonju Christian Hospital. METHODS: The minimal inhibitory concentrations of erythromycin and clindamycin of 426 beta- hemolytic streptococci isolated from clinical specimens between 1990 to 1999 were determined by agar dilution method. MLS resistance phenotypes were determined by double disk diffusion method using erythromycin and clindamycin disk, and genotypes were determined by polymerase chain reaction (PCR). The PCR primers for erm(A), erm(B), erm(C), erm(TR), and mef(A) were used in these study. RESULTS: The proportion of MLS resistance phenotypes of 80 erythromycin-resistant beta-hemolytic streptococci were 60.0% for constitutive phenotype, 23.8% for M phenotype, and 16.2% for inducible phenotype. The proportion of three MLS resistance phenotypes of group A streptococci were nearly equal. About three-fourths of group B streptococci had the constitutive phenotypes, whereas three-fourths (75%) of group G streptococci had the M phenotypes. All MLS resistant strains carried the erm(B) genes in constitutive phenotypes, erm(TR) genes in inducible phenotypes, and mef(A) genes in M phenotypes, respectively. CONCLUSIONS: Mechanisms and phenotype proportions of MLS resistance are different by species in beta-hemolytic streptococci. It is possible that MLS resistance genes have transferred among beta- hemolytic streptococci because the erythromycin resistance genes are the same in beta-hemolytic streptococci.

Detection of ermAM Gene and mefA Gene in Erythromycin-resistant Streptococcus Pyogenes / 감염

BACKGROUND: The mechanism of erythromycin resistance of Streptococcus pyogenes results from target modification or active efflux. The purpose of this study was to determine the positive rate of ermAM gene modifying 23S rRNA and that of mefA gene related with efflux for erythromycin-resistant S. pyogenes. METHODS: The minimal inhibitory concentrations (MICs) of erythromycin, azithromycin, clarithromycin, and clindamycin against S. pyogenes were tested by agar dilution method. ermAM and mefA genes were amplified by polymerase chain reaction (PCR) for 32 strains of erythromycin-resistant S. pyogenes. RESULTS: Among the 32 erythromycin-resistant S. pyogenes strains, 20 (62.5%) strains were positive for ermAM gene and 10 (31.1%) for mefA gene. Eighteen (90.0%) out of 20 strains with ermAM gene showed high-level erythromycin resistance (MIC> OR =64 microgram/mL), while all ten strains with mefA gene had low-level erythromycin resistance (MIC< OR =16 microgram/mL). CONCLUSION: Two-thirds of the S. pyogenes strains acquired erythromycin resistance by modification of target site, while the others by active efflux. Each mechanism of resistance is closely associated with range of MICs of erythromycin.