진주지역 A군 연쇄구균의 T항원, emm유전자형 분포와 Erythromycin 내성률 및 내성표현형 분포
Distribution of T types and emm genotypes of Group A Streptococci and Degree of Erythromycin Resistance and Its Genotypic and Phenotypic Characteristics in Jinju,
고은하 (Koh, Eun-Ha, 경상대학교 대학원)
- 주제(키워드) Group A streptococci , T type , emm genotype , ermB , mefA , erythromycin resistance
- 발행기관 경상대학교 대학원
- 지도교수 김선주
- 발행년도 2006
- 학위수여년월 2006. 2
- 학위명 박사
- 소속대학원 및 학과 대학원 의학과
- 전공 임상병리학전공
- 원문페이지 iv, 50
- 본문언어 한국어
- Group A streptococci (GAS), the most common cause of bacterial pharyngitis in children, is also a causative agent of severe life-threatening disease and non-suppurative sequelae. It was reported that serotypes of GAS causing rheumatic fever and post streptococcal glomerulonephritis are not rare in K...
- Group A streptococci (GAS), the most common cause of bacterial pharyngitis in children, is also a causative agent of severe life-threatening disease and non-suppurative sequelae. It was reported that serotypes of GAS causing rheumatic fever and post streptococcal glomerulonephritis are not rare in Korea. Continuous researches on clinical and bacteriologic characteristics of GAS are needed. Serotyping is essential for epidemiologic surveillance in outbreak of GAS infections. For accurate interpretation of serotypes of GAS from the patients, serotyping of GAS from the same-aged carriers in the same area is needed as well. The standard methods of epidemiology of GAS were T and M serotyping for many decades. While T typing is useful for screening, it does not completely identify organisms for epidemiological studies. The M protein is an important virulence marker but has a drawback for epidemiological studies in that it is difficult to maintain more than 80 kinds of sera. The emm gene, which encodes the M protein, has variable sequences at the 5' terminus by each M type, and emm genotyping using PCR and automatic sequencing has been utilized conveniently instead of M serotyping. Erythromycin (EM) or other macrolides have been used more commonly for the treatment of bacterial pharyngitis, especially regarding those patients allergic to penicillins. Recently, the proportion of EM-resistant GAS has been increased in many counturies including Korea. EM resistance mechanisms of GAS are mostly either target site modification due to methylase activity or efflux system. EM resistance is mediated by ermB, ermA and mefA genes. The phenotypic expression of macrolide resistance is classified as constitutive, inducible, or M according to the sensitivity results with EM and clindamycin (CC). Although EM resistance is a serious problem in our country, there are very few reports regarding to its genotypic or phenotypic characteristics. Throat cultures were taken from 2351 children of 4 elementary schools in Jinju, 2004. Two elementary schools are located in rural areas, while the other two are in urban areas. T typing and emm genotyping of GAS isolates was performed for epidemiologic study. Antibiotic susceptibility testing by disk diffusion and agar dilution method was performed against EM, CC, tetracycline (TC), chloramphenicol, ofloxacin and levofloxacin. The phenotypes of EM resistance were evaluated, and the frequency of ermB and mefA genes was determined by PCR. Isolation rate of GAS was 14.0% from 2351 elementary school children. There was no difference of isolation rate of GAS between boys (14.6%) and girls (13.1%). Children in rural areas showed significantly higher isolation rates compared to those in urban areas (P<0.05). T5/27/44 were the most common (29.6%). T12 (13.4%), T6 (10.7%) and T1 (7.6%) were relatively common. The emm44/61 was most frequent (29.2%) and emm6 (11.6%), emm22 (13.0%), emm2 (12.2%), and emm8 (8.1%) were relatively common. The resistance rate to EM, CC and TC was 9.8%, 8.8% and 18.3% respectively. EM resistance rate in rural areas showed significantly higher resistance rates compared to those in urban areas. Only 0.3% of isolates was resistant to ofloxacin. All isolates were susceptible to chloramphenicol and levofloxacin. Constitutive resistance was observed in 87.5%, the M phenotype in 9.4% and inducible resistance in only 3.1%. The ermB and mefA genes were present in 90.6% and 9.4% of strains, respectively. EM resistance rate of emm12 and emm77 was 81% and 60% respectively, and all of which showed constitutive resistance, while emm9 and emm18 showed the M phenotype. The organisms with most of the other emm genotypes (emm 1, 3, 5, 6, 22, 44/61, 75) were susceptible to EM. In conclusion, isolation rate of GAS was 14.0% from elementary school children in Jinju. Children in rural areas showed significantly higher isolation rates compared to thoses in urban areas. T5/27/44 and emm44/61 were prevalent while T12 and emm12 were significantly decreased compared to the past. Resistance rates of EM and CC were 9.8% and 8.8% respectively, which were dramatically decreased compared to the past. The resistance pattern was variable according to emm type, which suggests an association between the emm and resistance genes. M phenotype with the mefA gene was 9.4%, whereas constitutive resistance with the ermB gene was 90.6%. Dramatic decrease of EM and CC resistance might be related to the change of distribution of T and emm types. Socio-economic status seems to affect the carrier rates and antibiotic resistance of GAS. Continuous microbiologic and epidemiological surveillance should be conducted and the seriousness of antibiotic resistance should be underscored in our community.