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Objective To investigate the factors affecting the isolation of fastidious bacteria such as Streptococcus pneumoniae and Haemophilus influenzae from lower respiratory tract specimens in children.Methods A total of 210 lower respiratory tract specimens from children were collected and inoculated on both blood agar plate and chocolate agar plate 0.5 h,2 h,6 h,12 h,and 24 h after collection.The effect of specimen turnaround time,transport medium,and inoculation medium on the isolation of fastidious bacteria was studied.Results The results of 200 qualified specimens showed that the isolation of S.pneumoniae and H.influenzae significantly decreased with the increasing of specimen turnaround time (P＜0.05),but no significant difference was observed between 0.5 h and 2 h timepoints.The isolation of fastidious bacteria in semi-solid medium was non-significantly higher than the other two transport medium (P＞0.05).No significant difference was found in the isolation and growth ofS.pneumoniae and H.influenzae on different inoculation media (P＞0.05).Conclusions The appropriate specimen turnaround time,transport medium,and inoculation medium are important for improving the isolation of fastidious bacteria from lower respiratory tract in children.
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Objective To understand the mutations of macrolide resistance gene locus (23S rRNA) of Mycoplasma pneumoniae (MP) and its correlation with clinical features .Methods A total of 354 respiratory tract samples were collected from children pa-tients with pneumonia .MP and its mutations in 23S rRNA gene locus were detected by real-time PCR .The children cases of MP positive were divided into the mutation group and non-mutation group .Then the clinical data were compared between the two groups .Results Among 354 respiratory tract samples ,166 cases(46 .9% ) were MP positive ,moreover the mutation of 23S rRNA gene locus existed in 135 MP positive samples with the positive detection rate of 81 .3% ,while no 23S rRNA gene locus mutations were detected in 31 samples .Analyzing the clinical data of the mutation group and non-mutation group found that there was no sta-tistical difference in the aspects of age and gender between the two groups .The occurrence rates of severe pneumonia and extrapul-monary complications in the mutation group were higher than those in the non-mutation group (P<0 .05) ,moreover the average hospitalization time and fever duration in the mutation group were longer than those in the non-mutation group (P<0 .05) .Conclu-sion 23S rRNA gene locus mutation has higher detection rate ,prompting that MP shows high resistant rate to macrolides ,which could provide a certain basis for treatment of M P infections .
ABSTRACT
Objective To understand the drug resistance and antibiotic resistance mechanism ofβ-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 andβ-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.