Study On The Antibiotic Resistance And Mechanism Of Enteric Bacilli

Objective: To study the antibiotic resistance of Enteric Bacilli and identify the presence of their drug resistant genes.Methods: 5 reserved multi-drug resistant Salmonella typhi strains and 10 Shigella strains, 6 Escherichia coli strains isolated from clinic were selected. Their susceptibility to 12 different antibiotics were tested by K-B method. Reserpine inhibition test was used to detect the existence of the efflux system to Chloramphenicol in Salmonella typhi.β-lactamase gene TEM, aminoglycoside-modifying enzyme gene aac(6')-Ⅰb/aac3-Ⅱ, disinfectant and Sulfonamide-resistant gene qacEΔ1-sul1, Chloramphenicol acetyltransferase gene catA/catB and Chloramphenicol efflux gene cmlA were detected by PCR in Salmonella typhi. TEM gene, AmpC enzyme gene DHA/ACT-1, aac(6')-Ⅰb gene and qacEΔ1-sul1 gene were detected by PCR in Shigella and Escherichia coli.Results: 5 strains of multi-drug resistant Salmonella typhi resisted Ampicillin, Piperacillin, Cefuroxime, Cefoxitin, Gentamicin, Kanamycin, Chloramphenicol and Cotrimoxazole, but susceptive to Cefoperazone, Cefepime, Meropenem and intermediate to Cefalothim. 16 strains of Enteric Bacilli isolated from clinic resisted Ampicillin, Piperacillin and Cefalothim. The resistance rate of Cefuroxime, Kanamycin , Cefoxitin, Cotrimoxazole and Cefoperazone were 62.5%, 50%, 37.5%, 37.5% and 12.5%, respectively. They were susceptive to Meropenem, Cefepime, Gentamicin and Chloramphenicol. All 5 Salmonella typhi strains did show negative results in Reserpine inhibition test. 4 strains of Salmonella typhi showed positive PCR reaction to TEM gene but 1 strain showed negative. All strains did show positive PCR reaction to aac3-Ⅱ, qacEΔ1-sul1 and catA gene and negative reaction to aac(6′)-Ⅰb, catB and cmlA gene. Aac(6′)-Ⅰb gene was detected positively in Shigella and Escherichia coli resistant to Kanamycin. And qacEΔ1-sul1 gene was detected positively in 6 strains of Escherichia coli resistant to Cotrimoxazole while was negative in 10 strains of Shigella susceptive to Cotrimoxazole. ACT-1 gene was found positively in 2 strains of Shigella and Escherichia coli. DHA gene was negative in all strains.Conclusions: The multi-drug resistant Enteric Bacilli contains an array of drug resistant genes which have different structures and mechanisms. So they can resist many kinds of antibiotics simultaneously.