Isolation And Identification,Biofilm Detection And Drug Resistance Analysis Of Salmonella Isolates From Poultry

Salmonella may infect animals, which show septicemia or gastroenteritis, it may also infect human beings, which show food poison. Therefore, it is a zoonotic pathogen. Due to misuse of antibiotics, multiple drug resistance of Salmonella has become a focused problem worldwide. The development of poultry industry in our country is very fast, and Salmonella infections in poultry production are common phenomena. Since prevalence and drug resistance of Salmonella are changed along with time and environment, it is necessary to keep surveillance of prevalence and drug resistance of Salmonella. In this study, we identified the serotype of Salmonella isolates using multiple PCR, determined the drug resistance of Salmonella isolates by drug sensitive test, detected the biofilm-forming ability of Salmonella isolates, and analyzed the relationship between biofilm, class I integron and drug resistance of Salmonella. The study will provide epidemiological data for prevention and control of Salmonella infection.1 Isolation and identification of Salmonella from poultry and analysis of drug resistanceThe livers and gallbladders of ill chickens, ducks, and geese were collected in animal hospital of Yangzhou University from February 2014 to July 2015. Colorless, transparent or semi-transparent, round, smooth colonies were obtained by aseptic inoculation of sample on MacConkey agar and incubation, and identified as Salmonella by multiple PCR. A total of sixty-one Salmonella strains was isolated, in which the numbers of Salmonella typhimurium were 33, the numbers of Salmonella enteritidis were 3, and the numbers of Salmonella pullorum were 25. The chicken origin isolates were Salmonella pullorum (22/24,91.67%), while the goose origin were Salmonella typhimurium (29/33,87.88%). The drug sensitive test showed that all Salmonella isolates were resistant to benzylpenicillin, oxacillin, rifampicin, and vancomycin, and most Salmonella isolates were sensitive to cefoxitin, norfloxacin, amikacin, kanamycin, kanamycin, and florfenicol. More than ninety-six percentage of Salmonella isolates were resistant to six or more than six antibiotics, indicating that the ratio of multiple drug resistance of Salmonella isolates are high.2 Determination of biofilm in Salmonella isolates and it’s relationship with drug resistanceThe biofilm-forming ability of sixty-one Salmonella isolates was determined by crystal violet staining. Fifty four Salmonella isolates had biofilm-forming ability (54/61,88.52%), in which twenty eight isolates were Salmonella typhimurium (28/33,84.83%), twenty three isolates were Salmonella pullorum (23/25,92%), and three isolates were Salmonella enteritidis (3/3,100%). Three strains of each serotype, Salmonella typhimurium, Salmonella pullorum, and Salmonella enteritidis were selected for determination of MIC and MBC of antibiotics. Compared with Salmonella isolates in planktonic form, the MICs and MBCs of Salmonella isolates in biofilm were raised more than 20 folds. Therefore, most Salmonella strains have biofilm-forming ability, and Salmonella strains in biofilm are more resistant to antibiotics.3 Detection of class I integron in Salmonella isolates and it’s sequence analysisFifty nine multiple drug resistance Salmonella isolates were chosen for amplification of class I integron by gradient reduce PCR. The class I integrons were amplified from five Salmonella isolates and the length of class I integron was about 1.6 kb. Four class I integrons were amplified from Salmonella pullorum strains, one class I integron was amplified from a Salmonella enteritidis strain, while no class I integron was amplified from Salmonella typhimurium strain. The nucleotide homologies of five class I integrons were 100%. The gene cassette of class I integron included drfl7 and aadA5 genes by BLAST search in NCBI, indicated that these Salmonella isolates might be resistant to sulfamethoxazole, streptomycin, and TMP. The drug sensitive test showed that all five Salmonella isolates were resistant to SMZ-TMP. These data confirmed that class Ⅰ integron contributed to sulfanilamide resistance of these Salmonella isolates.