Antimicrobial Susceptibility Patterns of Escherichia coli and Shigella Isolated from Stool Samples from Adults and Children in Zambia

Introduction: Antimicrobial resistance (AMR) is a growing public health problem in low-to-middle income countries which have a high burden of infectious diseases. Poor antimicrobial stewardship in these regions has resulted in a rise in reported cases of AMR creating a need for country specific data to inform policy on the strategies of combating AMR. Here we show antimicrobial susceptibility patterns of Shigella, and E. coli isolated from stools of children under 5 years of age and adults. Methods: The study was nested under an enterotoxigenic Escherichia coli (ETEC) vaccine clinical trial and diarrhoea surveillance. Stool samples were collected at baseline, during scheduled visits and whenever the participants presented with diarrhoea as per study design. Following microbiological techniques for culture and microorganism identification, pure colonies were run on the BD Phoenix™ 100 for identification and antimicrobial susceptibility. For ETEC identification, colony PCR was done on all E. coli positive samples using heat-labile toxin and stable toxin specific primers, respectively. Results: Among the 211 samples analysed, 52.5% were from individuals with diarrhoea. Un-typed E. coli were the most common organism isolated (63.6%), followed by ETEC (12.7%) and 4.8% were Shigella sp. Majority of the organisms isolated were either susceptible or intermedial (80-100%) to all tested antibiotics except for Trimethoprim/Sulfamethoxazole which showed a high resistance of 82 – 93%. We also observed some multi-drug resistance (3.5%) among all organisms tested to the different antibiotics. Conclusions: The observed high prevalence of co-trimoxazole resistance and intermedial susceptibility to fluoroquinolones among ETEC, Shigella and other un-typed E. coli isolates, is critical for informing policy on the urgent need for antimicrobial stewardship and strengthening of AMR surveillance systems in Zambia.