Original Research

Evolution of antimicrobial resistance of Salmonella enteritidis (1972–2005)

Jermaine Khumalo, Bamusi Saidi, Joshua Mbanga
Onderstepoort Journal of Veterinary Research | Vol 81, No 1 | a807 | DOI: https://doi.org/10.4102/ojvr.v81i1.807 | © 2014 Jermaine Khumalo, Bamusi Saidi, Joshua Mbanga | This work is licensed under CC Attribution 4.0
Submitted: 23 April 2014 | Published: 12 November 2014

About the author(s)

Jermaine Khumalo, Department of Applied Biology and Biochemistry National University of Science and Technology, Zimbabwe
Bamusi Saidi, Central Veterinary Laboratory, Veterinary Diagnostics and Research Branch, Department of Veterinary and Technical Services, Zimbabwe
Joshua Mbanga, Department of Applied Biology and Biochemistry National University of Science and Technology, Zimbabwe


With the extensive use of antibiotics in livestock production, surveillance revealed an increase in Salmonella resistance to the commonly used antimicrobials in veterinary and public health. This serious threat to health care is further exacerbated by the limited epidemiological information about the common zoonotic agent, Salmonella enteritidis, required to determine antibiotic therapy. The aim was to characterise the antimicrobial resistance patterns of S. enteritidis isolates across different timelines (1972–2005) with accompanying genetic changes being investigated. Thirty-seven stored S. enteritidis isolates were collected from the Central Veterinary Laboratory, Harare, with antimicrobial susceptibility determined against eight antibiotics. Plasmids were isolated to analyse any genetic variation. An overall significant increase in resistance (p < 0.05) to nalidixic acid (0% – 10%), ampicillin (14.3% – 50%), tetracycline (14.3% – 30%) and erythromycin (71.4% – 100%) was observed across the timeline. However, the highest rates of susceptibility were maintained for gentamicin, sulphamethoxazole-trimethoprim, kanamycin and chloramphenicol. We report an increase in multidrug resistance (MDR) of 14.2% – 50% with an increase in resistotypes and plasmid profiles across the timeline. Eleven plasmid profiles were obtained in the 37 isolates studied with a minority of isolates (21.6%, 8/37) harbouring a 54 kb plasmid, commonly serovar-specific. A concerning increase in antimicrobial resistance to commonly administered drugs was observed across the timeline. The surge in MDR is of great concern and implies the need for consistent antimicrobial stewardship. No correlation was observed between the plasmid and antibiotic profiles.


Salmonella enteritidis, antimicrobial resistance, plasmid profiles


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