This study was carried out to detect the distribution of antibiotic-resistant genes in Escherichia coli isolates from slaughtered commercial chickens in Iran by PCR. The investigated genes included aadA1, tet(A), tet (B), dfrA1, qnrA, sul1, bla SHV , bla CMY , ere(A), catA1 and cmlA. According to biochemical experiments, 57 isolates from 360 chicken meat samples were recognized as E. coli. The distribution of antibiotic-resistance genes in the E. coli isolates included tet(A) and tet(B) (52.63%), dfrA1, qnrA, catA1 and cmlA (36.84%) and sul1 and ere(A) (47.36%), respectively. Nine strains (15.78%) were resistant to a single antimicrobial agent and 11 strains (19.29%) showed resistance to two antimicrobial agents. Multi-resistance which was defined as resistance to three or more tested agents was found in 64.91% of E. coli strains. The results indicate that all isolates harbour one or more of antibiotic resistance genes and that the PCR technique is a fast, practical and appropriate method for determining the presence of antibiotic-resistance genes.

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Brucellosis and leptosrirosis are important causes of livestock abortion, that can be serologically diagnosed. Generally, direct methods as bacteriological isolation are employed, but they are dangerous, taking up much time and not enough reliable. The polymerase chain reaction (PCR) has been reported to be successful for simultaneous detection of microorganism. The aim of this study was to use multiplex-PCR as an accurate, safe and rapid method to detect Brucella spp. and Leptospira spp. in aborted fetuses of bovine, ovine and caprine herds in Isfahan province (Iran). DNA was obtained directly from the stomach contents of aborted fetuses and PCR was performed by two pair novel primers. In total of the 276 specimens, 40 (14.4%) and 25 (9.0%) were identified positive for Brucella spp. and Leptospira spp., respectively. The convenience and the possibility of detection of both bacteria at a time, strongly support the use of this mPCR for routine diagnostics.

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Leptospira is recognized as an important public health problem worldwide, especially in tropical countries, and is a common cause of abortion in dairy and beef herds. The aim of the present study was to detect and characterize Leptospira as the causative agent of abortion in cattle using a PCR-RFLP in Chaharmahal va Bakhtiari and Isfahan provinces, Iran. A total of 220 bovine aborted foetuses and 120 vaginal discharges from an aborted calf were collected from 64 commercial dairy herds. After isolation of 60 Leptospira spp. from samples, RFLP analysis was carried out with HindIII and HaeIII restriction enzymes in reference strains and isolated for characterization. In a total of 340 specimens, 46 (20.9%) and 14 (11.66%) were identified positive for Leptospira spp. from aborted bovine foetuses and vaginal discharges, respectively. The present results also suggest that L. interrogans serovar hardjo has the highest prevalence in the region under study and L. hardjo is a major pathogen causing bovine abortion in Chaharmahal va Bakhtiari and Isfahan provinces of Iran.