Molecular Epidemiology of Antibiotic Resistance Genes and Virulence Factors in Multidrug-Resistant Escherichia coli Isolated from Rodents, Humans, Chicken, and Household Soils in Karatu, Northern Tanzania.

The interaction of rodents with humans and chicken in the household environment can facilitate transmission of multidrug-resistant (MDR) Escherichia coli (E. coli), causing infections that are difficult to treat. We investigated the presence of genes encoded for carbapenem, extended spectrum beta-lactamases (ESBL), tetracycline and quinolones resistance, and virulence among 50 MDR E. coli isolated from human (n = 14), chicken (n = 12), rodent (n = 10), and soil (n = 14) samples using multiplex polymerase chain reaction (PCR). Overall, the antimicrobial resistance genes (ARGs) detected were: blaTEM 23/50 (46%), blaCTX-M 13/50 (26%), tetA 23/50 (46%), tetB 7/50 (14%), qnrA 12/50 (24%), qnrB 4/50 (8%), blaOXA-48 6/50 (12%), and blaKPC 3/50 (6%), while blaIMP, blaVIM, and blaNDM-1 were not found. The virulence genes (VGs) found were: ompA 36/50 (72%), traT 13/50 (26%), east 9/50 (18%), bfp 5/50 (10%), eae 1/50 (2%), and stx-1 2/50 (4%), while hlyA and cnf genes were not detected. Resistance (blaTEM, blaCTX-M, blaSHV, tetA, tetB, and qnrA) and virulence (traT) genes were found in all sample sources while stx-1 and eae were only found in chicken and rodent isolates, respectively. Tetracycline resistance phenotypes correlated with genotypes tetA (r = 0.94), tetB (r = 0.90), blaKPC (r = 0.90; blaOXA-48 (r = 0.89), and qnrA (r = 0.96). ESBL resistance was correlated with genotypes blaKPC (r = 0.93), blaOXA-48 (r = 0.90), and qnrA (r = 0.96) resistance. Positive correlations were observed between resistance and virulence genes: qnrB and bfp (r = 0.63) also blaTEM, and traT (r = 0.51). Principal component analysis (PCA) indicated that tetA, tetB, blaTEM, blaCTX-M, qnrA, and qnrB genes contributed to tetracycline, cefotaxime, and quinolone resistance, respectively. While traT stx-1, bfp, ompA, east, and eae genes contributed to virulence of MDR E. coli isolates. The PCA ellipses show that isolates from rodents had more ARGs and virulence genes compared to those isolated from chicken, soil, and humans.

Occurrence of Multidrug-Resistant Staphylococcus aureus among Humans, Rodents, Chickens, and Household Soils in Karatu, Northern Tanzania.

We conducted this study to investigate the isolation frequency and phenotypic antibiotic resistance pattern of Staphylococcus aureus isolated from rodents, chickens, humans, and household soils. Specimens were plated onto mannitol salt agar (Oxoid, Basingstoke, UK) and incubated aerobically at 37 °C for 24 h. Presumptive colonies of S. aureus were subjected to Gram staining, as well as catalase, deoxyribonuclease (DNAse), and coagulase tests for identification. Antibiotic susceptibility testing was performed by using the Kirby-Bauer disc diffusion method on Mueller-Hinton agar (Oxoid, Basingstoke, UK). The antibiotics tested were tetracycline (30 µg), erythromycin (15 µg), gentamicin (10 µg), ciprofloxacin (5 µg), clindamycin (2 µg), and amoxicillin-clavulanate (20 µg/10 µg). The S. aureus strain American Type Culture Collection (ATCC) 25,923 was used as the standard organism. We found that 483 out of 956 (50.2%) samples were positive for S. aureus. The isolation frequencies varied significantly between samples sources, being 52.1%, 66.5%, 74.3%, and 24.5%, respectively, in chickens, humans, rodents, and soil samples (p < 0.001). S. aureus isolates had high resistance against clindamycin (51.0%), erythromycin (50.9%), and tetracycline (62.5%). The overall prevalence of multidrug-resistant (MDR) S. aureus isolates was 30.2%, with 8.7% resistant to at least four different classes of antibiotics.