Bacteriological studies on some multidrug resistant pathogens isolated from different animals and their effect on public health

Abstract

This study aimed to investigate the role of multidrug resistant pathogens on public health. For the MRSA study: A total of 134 nasal swabs were collected from diseased companion animals (48 horses, 41 dogs and 45 cats) showing symptoms of coughing, sneezing and nasal discharges. All samples were cultured on MRSA CHROM agar and subcultured on mannitol salt agar. Afterward, Gram’s stain films, biochemical tests and coagulase test were carried out. All coagulase positive strains were tested for antimicrobial susceptibility using the disk diffusion method using the following antibiotics: cefoxitin, ceftaroline, penicillin, oxacillin, tetracycline, doxycycline, erythromycin, azithromycin, clindamycin, trimethoprim/sulfamethoxazole, norfloxacin, quinupristin/dalfopristin, gentamicin and nitrofurantoin according to the recommendations of Clinical and Laboratory Standards Institute. Bacteriological examination of the samples showed that MRSA was recovered from 4 of 48 horses’ nasal swabs with a percentage of 8.33% and from one dog’s nasal swab with a percentage of 2.44%. All the examined cats were MRSA negative. The molecular identification was performed using MecA gene. A PCR product of mecA gene of one MRSA isolate from a dog and another from a horse was purified using the QIAquick purification. The two obtained sequences accession numbers in the GenBank are MN938919 and MN938920. For the ESBL study: A total of 135 rectal swabs were collected (72 dogs, 33 cats and 30 horses), all animals were suffering from diarrhea. All swabs were cultured on MaCconkey agar supplemented with 2mg/L cefotaxime to enhance selection of b lactamases producer and assure selection of Enterobacteriaceae. The biochemical confirmation was done using TSI, MIO, citrate and urease production and tryptophan reduction. All the chosen isolates were tested against cefotaxime (30 g), cefotaxime with clavulanic acid (30/10 g), ceftazidime (30 g), ceftazidime with clavulanic acid (30/10 g), ceftazidime with clavulanic acid (30/10 g), ceftazidime with clavulanic acid (30/10 g). DNA was extracted and PCR was performed using CTX, TEM, OXA and SHV specific primers on 70 phenotypically suspected ESBL isolates. Fifty three strains of them contain ESBL genes (46 E.coli and 7 Klebsiella pneumoniae), single or in combination. Bla TEM, bla CTX-M, bla SHV and bla OXA genes were detected in 51 (72.9%), 29 (41.4%) and 24 (34.3%) of the samples, respectively. None of the tested isolates was positive for blaOXA. According to molecular analyses.33 out of 70 isolates (47.1%) carried several bla genes (more than one gene), 20/70 (28.6%) of samples harbored a single bla gene, while 17(24.3%) isolates were negative for all 4 genes.