Antibiogram and Resistant Gene (Gentamicin and Estended Beta-lactam) Profile of Escherichia coli Isolated from Yoghurt

The antibiotic susceptibility profile of Escherichia coli isolated from yoghurt samples within the Port Harcourt metropolis was investigated. Yoghurt samples (sachets and bottled yoghurts) were randomly bought from vendors within Port Harcourt and were transferred in an ice-pack container to the microbiology laboratory, at Rivers State University where they were analyzed. Enumeration and isolation of faecal coliform were done using Eosin Methylene Blue Agar (EMB). Aliquot from 10-1 dilution of the sample was aseptically transferred into dried EMB agar plates in duplicates, spread evenly using a sterile bent glass rod and incubated at 45℃ for 24-48 hours. After incubation, plates were observed for growth and counts were recorded for the determination of colony forming unit while colonies on the plates were sub-cultured on freshly prepared nutrient agar plates. Morphological, gram reaction and biochemical tests were used for identification. The Kirby Bauer disk diffusion test on Mueller-Hinton agar using commercially prepared antibiotics was used in determining the antibiotic susceptibility profile of the isolates. Results showed that the mean range of the faecal coliform load of the yoghurts was 0.0-6.0×102 CFU/mL. More so, out of the samples analyzed, only two samples were positive for E. coli. Results of the antibiotics susceptibility showed that all five E. coli isolates were resistant to more than two antibiotics and exhibited multi-drug resistance. Some of the isolates possessed Inc-P and TEM-resistant genes. Although they were completely susceptible to Nalidixic acid, Levofloxacin, Ceftriaxone and Ofloxacin antibiotics. More so, 40% resistant isolates had a MAR index of 0.2, while the other 40 and 20% resistant isolates had a MAR index of 0.5 and 0.3, respectively. Contamination of the samples could be through manufacturing or packaging and distribution processes. Thus, good manufacturing practice is highly recommended.