Multiple drug resistant enterobacteria from biofilms in some tap water supplies in a Nigerian university

Abstract

Tap outlets have been found to contain biofilms, which are a consortium of bacteria, fungi, viruses and protozoa. These microorganisms, especially Gram negative bacteria, could be pathogenic and highly resistant to antibiotics, leading to an increase in the prevalence of diseases worldwide. The university community depends on water from boreholes for consumption and domestic uses; as such, the need to identify the Gram negative bacteria is expedient. The main objective of this research is to determine the potability of the water released from the taps, and ultimately reduce the incidence of biofilm-related water infections. Water samples were collected from five boreholes and five tap outlets were swabbed with a sterile swab stick. Coliforms were estimated from the water samples using the Most Probable Number (MPN) technique. Gram negative bacteria were isolated and identified from the swabbing using standard bacteriological and biochemical tests. The antibiotic resistance patterns of the isolates were also determined, and the genes responsible for the multiple antibiotic resistance were identified using the DNA extraction and Polymerase Chain Reaction (PCR) methods. Bacterial counts of the samples ranged from 6.0×105cfu/mL to 1.4×106cfu/mL. MPN values of the tap water samples ranged from 4 to 1100+cfu/100mL, which exceeded the WHO standards of water quality. A total of 31 bacteria were isolated, of which 8 (25.8%) were Pseudomonas sp, 7 (22.6%) were Proteus sp, 4 (12.9%) were Klebsiella sp, 4 (12.9%) were Escherichia coli, 3 (9.7%) were Enterobacter sp, 3 (9.7%) were Citrobacter sp and 2 (6.5%) were Salmonella sp. All the bacteria showed multiple drug resistance to different antibiotics used, especially the cephalosporins. The gene found to be responsible for the cephalosporin resistance was the TEM - 445. Tap swabbing and water samples were found to contain a high value of coliforms (4 – 1100cfu/100mL), showing heavy faecal pollution, many of which could be pathogenic microorganisms that renders the water unfit for human consumption. The presence of these multidrug resistant microorganisms in the tap outlets could pose a serious threat to public health.