Abstract

Bacteria belonging to the family Enterobacteriaceae are facultative anaerobic, Gram-negative, non-spore forming rod-shaped bacilli. Members of this heterogeneous group of bacteria do not only form part of the normal flora of humans and animals, but are also widely distributed in various environments such as water, soil and plants. Most members of the Enterobacteriaceae were previously considered to be harmless. However, there is evidence that some strains potentially cause diseases and pathological conditions such as diarrhoea, gastroenteritis, urinary tract infections and inflammatory bowel diseases in animals and humans. The aim of the present study was to isolate and determine the antibiotic resistant profiles of Enterobacteriaceae isolated from dogs that visited the North West University animal hospital. Fifteen (15) faecal samples were collected from the rectum of dogs that visited the Hospital, using sterile swabs and the samples were placed in transport media.  The samples were immediately transported on ice to the laboratory for analysis.  MacConkey agar with crystal violet was used for selective isolation of bacteria belonging to the family Enterobacteriaceae. Only isolates that satisfied the preliminary identification tests (Gram staining, triple sugar iron agar test, citrate agar test and oxidase test) and confirmatory identification test (API 20E) were retained for further analyses.Antibiotic susceptibility tests were performed on all positively confirmed isolates to determine their antibiotic resistant profiles against tetracycline (30 µg), ampicillin (10 µg), amoxicillin (10 µg), penicillin (10 µg), gentamycin (30 µg) and streptomycin (10 µg). A total of 120 isolates were positively identified as members of the Enterobacteriaceae. All the isolates were Gram negative rods and oxidase negative.  A large proportion (92.5%) of these isolates fermented the sugars in the TSI agar with only a small proportion (23.3%) producing hydrogen sulphide gas.  However, a relatively larger proportion of these isolates (62.5%) produced gas from the fermentation of sugars. On characterizing these isolates for the ability to hydrolyze citrate, a large proportion (71.7%) were negative for this test. The API 20E test results indicated that bacteria species belonging to four main genera (Escherichia, Salmonella, Shigella and Klebsiella) were indentified. A large proportion (50%) of these isolates were identified as Escherichia coli while 25, 15.8 and 9.2% wereSalmonella spp., Klebsiella spp. and Shigella species, respectively.  Isolates from all the samples were most often, resistant to penicillin, ampicillin, tetracycline and amoxicillin while very little resistance was observed against gentamycin and streptomycin.  The MDR phenotypes PG-AP-A-T, PG-AP-A-T-S, PG-AP-A, PG-A-T and PG-AP-A-T-GM-S were dominant in isolates from samples analyzed.  Although a large proportion of the isolates were resistant to three or more antibiotics, a cause for concern was the fact that some isolates were resistant to all antibiotics screened. The identification of multiple antibiotic resistance among the isolates ignites the need to establish appropriate testing procedures before the administration of drugs to animals, thus reducing the possibility of the development and transfer of antibiotic resistant genes between animals and humans.

Key words: Enterobacteriaceae, multiple antibiotic resistance, multi drug resistance (MDR) phenotypes.