儿童肺炎链球菌分离株青霉素、红霉素耐药性与耐药相关基因研究

目的了解苏州地区儿童肺炎链球菌(Streptococcuspneumoniae,Sp)临床分离株青霉素、红霉素耐药的状况。方法对呼吸道感染患儿痰标本中分离到的26株Sp进行青霉素、头孢呋辛、头孢曲松、头孢噻肟、红霉素E test药敏试验,和与青霉素、红霉素耐药相关的pbp2B、ermB、ermA/B、mefA基因PCR检测,测得pbp2B基因产物进行测序并与SpR6株(青霉素敏感株,登录号:NC003098)序列比较。结果(1)pbp2B基因突变15株(58%),均为点突变,突变类型有A型11株(73%)、B型2株(13%)、C型1株(7%)、D型1株(7%);(2)11株无突变菌中青霉素、头孢呋辛、头孢曲松、头孢噻肟敏感株分别为9株(82%)、10株(91%)、11株(100%)、11株(100%);15株突变菌中青霉素、头孢呋辛、头孢曲松、头孢噻肟不敏感株分别为13株(87%)、11株(73%)、1株(7%)、1株(7%);11株A型突变株对青霉素均不敏感,10株对二代头孢不敏感;(3)ermB基因阳性9株(35%)、ermA/B基因阳性16株(62%)、mefA基因阳性7株(27%)、erm或(和)mef基因阳性21株(81%);(4)erm或(和)mef基因阳性株红霉素最低抑菌浓度为2～>256mg/L。结论pbp2B基因突变是本地区Sp青霉素耐药机制的主要遗传学基础之一;突变株中,A类突变率最高,表现对青霉素、二代头孢不敏感;ermA、ermB和mefA3种红霉素耐药基因单独或共同表达

Relation of pbp2B, ermB, ermA/B, mefA genes with resistance to penicillin and erythromycin among Streptococcus pneumoniae isolates from children

Objective To investigate the relation of pbp2B, ermB, ermA/B and mefA genes to penicillin and erythromycin resistance among isolated Streptococcus pneumoniae (Sp) in children. Methods Twenty-six strains of Sp were collected from September 2002 to April 2003 at the Children Hospital of Suzhou University. (1)Twenty-six pneumococcal isolates were obtained from respiratory tract secretions of children with respiratory diseases. (2)Susceptibility of the isolates to penicillin, cefuroxime, ceftriaxone, cefotaxime and erythromycin was determined by E-test. (3)The genes pbp2B, ermB, ermA/B and mefA of the isolates were detected with PCR. (4)The PCR product of pbp2B gene was sequenced. (5)DNA sequences of pbp2B of pneumococcal isolates were compared with those of SpR6 penicillin sensitive(www.ncbi.nlm.gov/nucleotide, NC-003098)]. Results Among the 26 isolates studied, pbp2B gene mutation was found in 15(58%)isolates,all were point mutation of A, B, C and D genotypes which were seen in 11(73%),2(13%),1(7%) and 1(7%), respectively. The numbers of isolates susceptible to penicillin, cefuroxime, ceftriaxone and cefotaxime were 9(82%), 10(91%), 11(100%) and 11(100%), of 11 non-mutation isolates;numbers of isolates resistant to penicillin, cefuroxime, ceftriaxone, and cefotaxime were 13(87%), 11(73%), 1(7%) and 1(7%) out of 15 isolates with mutation.ErmB, ermA/B, mefA and erm/mef genes were positive in 9(35%), 16(62%), 7(27%) and 21(81%)isolates. MIC of erythromycin was 2 to >256 mg/L among pneumococcal isolates with erm/mef genes. Conclusion Among antibiotic resistant pneumococcal isolates in the area,the main basis of penicillin resistance was the mutation of pbp2B genes. Genotype A mutation had the highest rate among the isolates with mutation and manifested as resistance to penicillin and cefuroxime. Expression of either all or any of the ermA, ermB and mef genes led to erythromycin resistance. Antibiotics resistant Sp strains in this area are forming a challenge to efficacy of penicillin and erythromycin.