Resistance Of Pathogenic Strains Isolated From Stools Of Outpatients In Wuhan And Study On The Primary Mechanism Of Resistance To Quinolone

ObjectivesTo investigate consititution of Pathogenic Strains isolated from Stools of outpatients in Wuhan and study on the primary mechanism of resistance of Salmonella enterica serotype typhimurium(STM) and molecular epidemiology of STM of community acquired infection. The aim of all above was to provide update data for antimicrobial resistant monitoring ,clinical reasonable usage of antimicrobial agents, new drug or vaccine developing and epidemiology.MethodsA total of 126 pathogenic strains isolated between June 30. 2004 and Oct 31.2004 were received from 4536 stool of outpatients who were from four big hospitals in Wuhan. Antibiotic susceptibility tests were evaluated by the Agar Dilution method. And Salmonella enterica serotype typhimurium isolated were studied for the occurrence of mutations in the genes coding for gyrase(gyrA andgyrB) and topoisomerase IV(parC and parE) by PCR amplimer conformation analysis.To type STM by REP-PCR, and compared with antibiotic susceptibility and the results of conventional biotypingResults126 pathogenic strains isolated from 4536 stool included 33 salmonella typhimurium(0.7%) ,18 salmonella enteritidis(0.4%) ,13 other nontyphoidal salmonella(0.3%) , 33 enteropathogenic E .coli(0.7%) and 29 shigella(0.6%). The rate of the resistant to Cip of nontyphoidal salmonella ,shigella and enteropathogenic E .coli were 39.1%,6.9% and 12.1% respectively. The resistant rates of other antimirobial agents, such as ampicillin, nalidix acid, tetracycline, trimethroprim/sulfamethoxazole exceeded 50% .They kept well sensitive to the third cephalosporin because of their resistance rates lower than 5%. Among 33 salmonella typhimurium, the squencing of the quinolone resistance-deterning region of these genes in highly quinolone-resistant mutants(MICs of 4 to 16 ug/ml) of the 24 STM revealed the presence of gyrA mutation at condons corresponding to Ser83 associated with a mutation at Asp87 and parC mutation at condons corresponding to Ser80. Few mutations were founded in the gyrB and parE genes, and only a few were founded a suspicious inserted base in the gyrB and parE genes.With aid of REP-PCR, the 32 strains were divided into 9 profiles which were correlated to the antibiotic susceptibility spectrums.ConclusionsThe pathogenic bacterium of septic diarrhea mostly included nontyphoidal salmonella, enteropathogenic E .coli and shigella in Wuhan community in which nontyphoidal salmonella accounting for 51%. These pathogenic strains were severely resistant to the ordinary antibiotics of gastroenteritis, especially with salmonella typhimurium. The study suggest the resistance of salmonella typhimurium of community acquired infection in WuHan were associated with mutations of the quinolone resistance-determining regions. It maybe a epidemic outbreak in community.