[The Antimicrobial Resistance Analysis of 73 Strains of Streptococcus pneumoniae Isolated from Infant Respiratory Tract].

OBJECTIVE: To preliminary study of the resistance mechanisms of S. pneumoniae (S. pn) by determining the resistance rates and gene of S. pn isolated from the lower respiratory tract infection infants. METHODS: Drug susceptibility test with disk diffusion and broth micro-dilution was conducted to evaluate the resistance rates of 73 strains of S. pn isolated from the lower respiratory tract infection infants to penicillin, levofloxacin and other 10 antibiotics. PCR method was used to analysis the antimicrobial resistant genes tet M, mef A, erm A, erm B and int Tn of the isolates. RESULTS: The antibiotic resistance rates of the S. pn isolates to erythromycin, clindamycin and tetracycline were 95. 9%, 94. 5%, 87. 7% and 0% to vancomycin when tested with disk diffusion method. The antibiotic resistance rates of these isolates to penicillin, cefotaxime and ceftriaxone were 45. 2%, 47. 9% and 46. 6% respectively when tested with broth micro-dilution method. The carrier frequencies of tet M, mef A, erm A, erm B, int Tn genes in the 73 isolates were 91. 8%, 63. 0%, 58. 9%, 39. 7% and 61. 6% respectively. CONCLUSION: The S. pn strains isolated from infant respiratory tract in Chengdu perform a serious drug resistance problem, especially to routine antibiotics like erythromycin, clindamycin and tetracycline and cephalosporin, the resistance rate to levofloxacin, chloramphenicol remained at a low level; the resistance to tetracycline was closely related with the tet M gene fragment, the resistance to macrolide was mainly decided by active efflux pump and secondarily by the alternation of gene targeting, int Tn had close relation with tet M, erm B.

[Sequence analysis of G glycoprotein gene of human respiratory syncytial virus].

OBJECTIVE: To understand the variation of G glycoprotein gene of human respiratory syncytial virus (HRSV) obtained from Sichuan in 2010 and determine the dominant genotypes. METHODS: G glycoprotein gene of seven cases of subtype A and eleven cases of subtype B of HRSV were amplified by RT-PCR and sequenced. The phylogenetic trees were constructed to determine the subtype of samples. And then, the genetic variations of the second hypervariable region of G glycoprotein gene were studied. RESULTS: The nucleotide genetic distances of G glycoprotein gene in subtype A and subtype B HRSV were 0.022 +/- 0.005 and 0.073 +/- 0.010, respectively. Transitions were more prevalent than transversions, GA -AG were the most frequent transitions detected among group A viruses, while UC+CU transitions were the most among group B. Phylogenetic analyses demonstrated that 7 subtype A virus could be clustered into one genotype, genotype GA2, and 11 subtype B virus could be clustered into two genotypes, GB2 and BA. The length of G protein gene in group A was all 298aa, but in group B included 295aa, 312aa and 315aa. Selective pressure was purifying selection in both subtypes. 9 positively selected sites in group A and 1 in group B on the second hypervariable region of G protein were identified. CONCLUSION: GA2, GB2 and BA were the main genotype. The changes may favor virus escape from the host immune response including the variation of the G protein gene length, frequency of nucleotide changes and selective pressure.