Presence, characteristics and antibiotics resistance of E. coli (bacteria) found in retailed milk in Benin City, Nigeria

Published In: African Journal of Clinical and Experimental Microbiology
Article Link: https://www.ajol.info/index.php/ajcem/article/view/205631/193910
Author(s): Igbinosa, I. H. and Chiadika, C.

Prevalence, characteristics and antibiotics resistance of E. coli (bacteria) found in retailed milk in Benin City, Nigeria
Photo Illustration: Prevalence, characteristics and antibiotics resistance of E. coli (bacteria) found in retailed milk in Benin City, Nigeria
Photo Credit
: The Courier Mail

This study conducted into the presence, characteristics and antibiotics resistance of Escherichia coli (bacteria) in raw and fermented (nono) milk was conducted in Benin City, Nigeria by Igbinosa, I. H. and Chiadika, C. both of Applied Microbial Processes & Environmental Health Research Group (AMPEHREG), Faculty of Life Sciences, University of Benin, Benin City, Nigeria.

The researchers posited that most Escherichia coli strains are harmless commensals, but some serotypes can cause serious food poisoning in their hosts, and are infrequently responsible for product recalls due to food contamination. That the present study was carried out to determine the occurrence of E. coli O157:H7 and other E. coli strains from raw and fermented (nono) milk in Benin City, Nigeria.

The researchers obtained a total of 66 (33 raw and 33 nono) milk samples from retailers in 3 different stations in Aduwawa market, Benin City, Nigeria between January and June 2017. 

The samples were analysed by cultural methods for faecal coliforms using M-Fc agar, E. coli using Chromocult coliform agar, and E. coli O157:H7 using sorbitol MacConkey agar supplemented with cefixime and potassium tellurite. Presumptive E. coli andE. coli O157:H7 isolates were confirmed by polymerase chain reaction (PCR) assay using specific primers. 

The antimicrobial susceptibility profile of confirmed isolates was performed by the researchers using the Kirby-Bauer disk diffusion method, with zones of inhibition interpreted according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). The study data were analysed using the SPSS version 21.0.

 The researchers reported that from the 66 nono and raw milk samples assessed in this study, all (100%) were phenotypically positive for E. coli O157:H7. A total of 19 E. coli O157:H7 and 41 other strains of E. coli were confirmed by PCR. 

Also, the resistance profile of the 19 E. coli O157:H7 isolates showed 100% (19/19) resistance to penicillin G and ampicillin; 94.7% (18/19) to chloramphenicol; 89.5% (17/19) to erythromycin; and 78.9% (15/19) to sulfamethoxazole and oxytetracycline, while the sensitivity profile showed that 100% (19/19) E. coli O157:H7 isolates were sensitive to gentamicin and ofloxacin. 

The resistance profile of other 41 E. coli isolates showed 100% (41/41) resistance to penicillin G and ampicillin; 97.6% (40/41) to chloramphenicol; and 92.7% (38/41) to erythromycin, while 97.6% (40/41) were sensitive to gentamicin and kanamycin. Ten E. coli O157:H7 isolates (52.6%) showed extensive drug resistance patterns to 11 antibiotics in 7 antimicrobial classes with multiple antibiotic resistance (MAR) index of 0.46.

The researchers reiterated that findings from the study indicated that the safety and quality of fresh and fermented milk sold in the study area were not satisfactory and could be of public health concern.

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