Resistant mechanism of β-lactam antibiotic of invasive @(xt)Streptococcus pneumoniae

Abstract

Objective To understand the drug resistance and antibiotic resistance mechanism of β-lactam antibiotics of invasive Streptococcus pneumoniae isolated from Shanghai Children′s Hospital, provides the reference for the rational use of antimicrobial agents. Methods This study is based on the research of the mechanism of drug resistance. 62 isolates of invasive Streptococcus pneumoniae were collected from Shanghai Children′s Hospital from January 2005 to December 2011. Minimum inhibitory concentrations (MIC) of strains to 9 antimicrobial agents were determined by E-test method. The penicillin binding protein coding genes pbp2x, pbp2b, and pbp1a of Streptococcus pneumoniae were amplified by PCR. Then, the correlation between the gene mutation and β-lactam antibiotics resistant level were analyzed. The murM gene of Streptococcus pneumoniae was amplified by PCR and the correlation of mutation and β-lactam antibiotics resistant level was analyzed. Results Out of 62 strains of invasive Streptococcus pneumoniae from children, the detection rate of penicillin resistant Streptococcus pneumoniae was 43.6% (27/62). Between penicillin intermediate Streptococcus pneumoniae (PISP) (100%, 25/25) and penicillin sensitive Streptococcus pneumoniae (PSSP) (3/10), the difference of gene mutation rate near the pbp2b conserved sequence was statistically significant (χ2=21.875, P＜0.01). The same situation occurred between penicillin resistant Streptococcus pneumoniae (PRSP)(100%, 27/27)and PSSP (3/10) (χ2=23.310, P＜0.01). Also the difference of gene mutation rate of PISP (84%, 21/25) vs PSSP (0) and PSSP (0) vs PRSP (85.2%, 23/27) near or in the pbp2x conserved sequence were statistically significant (χ2=21.000，P＜0.01；χ2=22.513，P＜0.01). The difference of gene mutation rate near the pbp1a conserved sequence and Insertion sequence, which were statistically significant, occurred between PISP and PSSP (χ2=13.22，P＜0.01), between PRSP and PSSP (χ2=37.000，P＜0.01), between PISP and PRSP (χ2=10.211，P=0.001). MurM gene mutation rate was statistically significant different between the 2 group penicillin MIC≥8 mg/L or ceftriaxone MIC≥2 mg/L group (95.8%, 23/24) and penicillin MIC<8 mg/L or ceftriaxone MIC<2 mg/L group (0) (χ2=56.2，P=0.002 6). Conclusions The resistance phenomenon of invasive Streptococcus pneumoniae in Shanghai Children′s Hospital is serious. The gene mutations of pbps and murM play a role in amide in the beta of antibiotic resistance, and there is a certain correlation with the antibiotic resistance level. （Chin J Lab Med,2014,37:748-752） Key words: Streptococcus pneumoniae; Beta-Lactam resistance; Genotype; Penicillin-binding proteins; Bacterial proteins