Typhoid And Salmonella Paratyphi A Drug Resistance Surveillance, Detection And Expression Analysis, With The Full Genome Sequence Of Multi-drug Resistant Active Efflux Gene Acr

Objective To determine the resistance of Salmonella typhi and Salmonella paratyphi A to antimicrobial agents commonly used in clinic.Methods A total 44 strains of Salmonella typhi and Salmonella paratyphi A isolated from patients in the First Affiliated Hospital of Chongqing Medical University from January 1997 to December 2001 were tested with agar dilution of NCCLS recommended.Results Ofloxacin,ciprofloxacin and cefotaxime had excellent activities against Salmonella typhi and Salmonella paratyphi A with the MIC50 of 0.5, 0.25, 0.25μg/ml and MIC90 of 2, 0.5, 0.25μg/ml respectively. The rates of drug resistance and intermediate were 2.27%,2.27%,2.27% and 2.27%,0%, 2.27% respectively. Piperacillin,chloramphenicol,tetracycline and gentamicin had relatively good activities against Salmonella typhi andSalmonella paratyphi A with MIC50 of 4, 8, 4, 0.25μg/ml and MIC90 of >128, >128, 128, 16μg/ml respectively. The rate of resistance and intermediate were 22.73%,31.38%,31.38%,11.36% and 0%,11.36% ,13.64%, 0% respectively. The multi-drug(three or more) resistance presented in 11 isolates(25%) including three stains being resistant to piperacillin,chloramphenicol,tetracycline and gentamicin , six strains being resistant to piperacillin,chloramphenicol and tetracycline , one strains being resistant to chloramphenicol,tetracycline and gentamicin, one strains being resistant to cefotaxime,tetracycline and gentamicin. The rates of drug resistance to ofloxacin ,ciprofloxacin ,cefotaxime,piperacillin,chloramphenicol,tetracycline and gentamicin in 1997-1998 were 0%,0%,0%,60%,86.67%,80%,26.67%,and 3.45%,3.45%,3.45%,3.45%,3.45%,6.90% in 1998-2001 respectively.10 of the 11 multi-drug resistant strain were isolated before 1998 and just 1 strain after that time, and there just 1 strain resistant to both ofloxacin and ciprofloxacin after 1998.this suggested that the multi-drug resistant strains were existed in Salmonella typhi and Salmonella paratyphi A but had reduced in recent years.Conclusions The resistant rates of Salmonella typhi and Salmonella paratyphi A to fluoroquinolones and the third generation of cephalosporins were low in Chongqing. However, piperacillin,chloramphenicol andtetracycline resistant strains were common. So it is important to use antibiotics reasonably for delaying the occurrence of resistant strains .