Abstract
Acinetobacter species have been found in a variety of environments, including soil, food, plants, hospital environments and water. Acinetobacter baumannii is an opportunistic and emerging waterborne pathogen. It has been implicated in several nosocomial infections that demonstrate resistance to commonly administered antibiotics. We investigated phenotypic antibiotic resistance (PAR) and relevant antibiotic resistance genes (ARGs) in A. baumannii isolated from three freshwater resources in the Eastern Cape Province, South Africa; A. baumannii (410) was confirmed by the recA and gyrB genes of 844 suspected Acinetobacter species in the water samples. The PAR of the confirmed isolates was assessed using a panel of 11 antibiotics by the disc diffusion method, while ARGs were investigated in isolates exhibiting PAR. The A. baumannii isolates were resistant to piperacillin-tazobactam (11.2%), ceftazidime (12%), cefotaxime (18.8%), cefepime (8.8%), imipenem (2.7%), meropenem (4.15%), amikacin (2.4%), gentamicin (8.8%), tetracycline (16.8%), ciprofloxacin (11%) and trimethoprim/sulfamethoxazole (20.5%). For multidrug resistance (MDR), two isolates were resistant to all antibiotics and 28 isolates were resistant to imipenem and meropenem. Moreover, β-lactamases blaTEM (64.4%) and blaOXA-51 (28.70%) as well as sulphonamides sul1 (37.1%) and sul2 (49.4%) were common ARGs. Overall, PAR and ARGs had positive correlations (r) in all rivers. Detection of MDR-A. baumannii in freshwater resources could be linked to possible wastewater discharge from the nearby animal farms, indicating potential implications for public health.
Highlights
Acinetobacter species are known lactose non-fermenters that were formerly regarded as colonisers of different natural habitats, with low ability to cause infection [1,2]
The detection of antibiotic resistance genes (ARGs) in A. baumannii recovered from the aquatic environments in the study area might be an indication of the secondary impact of antibiotic mismanagement, which presents a significant challenge to public health
This could be the case, especially at sampling site GF4, which is characterized with discharge of wastewater effluent from the downstream Craddock wastewater plant (WWTP), animal rearing and refuse dumping
Summary
Acinetobacter species are known lactose non-fermenters that were formerly regarded as colonisers of different natural habitats, with low ability to cause infection [1,2]. Phenotypic antibiotic resistance (PAR) in A. baumannii from Great Fish, Keiskamma and Tyhume Rivers. The multiple drug resistance (MDR) phenotypes of A. baumannii isolated from the freshwater sources (Great Fish, Keiskamma and Tyhume Rivers) are highlighted in Figure 1 (heatmap). While no significant difference (p < 0.05) was seen among the A. baumannii isolates that harboured qnrB in the samples, those that possessed qnrD genes in the Great Fish (p < 0.05) and Tyhume (p < 0.05) Rivers were significantly higher (p < 0.05) than other fluoroquinolone resistance genes investigated in all the rivers. Apart from other reasons, possession of these genes could induce resistance to carbapenems (IMI and MEM), β-lactams (PTZ), and cephems (CAZ, CTX and CPM) in A. baumannii because these isolates typically exhibited MDR to all the four Ambler classes (A, B, C and D) of β-lactamases [33,34]. Future studies on the rivers should be conducted to examine residual antibiotics in the freshwater resources
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