Antimicrobial Susceptibility Testing and Resistance Mechanisms of Escherichia Coli Bloodstream Infections in Patients Aged 18–65 at Victoria Chitepo Provincial Hospital from 2023 to 2025

Abstract

Bloodstream infections (BSI) are a primary global health concern, particularly in developing countries, such as Zimbabwe. In Zimbabwe, the delayed turnaround of blood culture results and lack of data on antibiotic resistance patterns emphasize the need for improved empirical treatment guidelines. This study aimed to identify Escherichia coli isolates in positive blood cultures, their antimicrobial resistance patterns and resistance mechanisms in patients aged 18–65 years clinically suspected of bloodstream infections. A hospital-based cross-sectional study was done at Victoria Chitepo Provincial Hospital, analysing 1046 blood culture records from January 2023 to October 2025. Patients were consecutively enrolled based on clinical suspicion of bloodstream infection, and blood samples were collected as part of routine diagnostic care. All positive blood cultures yielding E. coli during the study period were included through purposive sampling, resulting in 108 eligible isolates. Blood cultures were incubated using the BACTEC system, followed by biochemical identification of bacteria and antimicrobial susceptibility testing using the Kirby–Bauer disk diffusion method on cultures that would have shown growth. Phenotypic methods were used to detect resistance mechanisms such as β lactamase production. A list of Escherichia coli-positive blood culture patient results was created in an Excel sheet using data from medical records. Of the 108 E. coli culture positive samples, 63 (57.6%) were from male patients and 45 (42.4%) were from female patients. E. coli isolates showed high resistance to ampicillin (84%), cotrimoxazole (60%), and cefepime (41%) with a consistent susceptibility of a 100% to meropenem. High moderate susceptibility was observed for Ceftriaxone (89%), Ceftazidime (86%), and Ciprofloxacin (82%). Phenotypic testing for resistance mechanisms revealed that 16% of E. coli isolates were β-lactamase producers, signifying the emergence of extended spectrum β-lactamase (ESBL) activity. This study emphasized that E. coli accounted for 10.3% of bloodstream infections at Victoria Chitepo Provincial Hospital and exhibited substantial antimicrobial resistance patterns and emerging resistance mechanisms. A broader sampling across multiple healthcare facilities to ensure a representative population would assist in the guidance of effective BSI empiric antimicrobial treatment in patients.