Assessment of microbial quality and detection of extended spectrum β-lactamase genes in Gram-negative bacterial isolates of herbal mixtures commonly hawked in Sagamu metropolis, Ogun State, Nigeria

Abstract

Background: The use of herbal mixtures in the treatment of diseases is on the rise. Many of these herbal drugs are not produced under hygienic conditions and safety issues associated with herbal medicines may have an exacerbated impact in immunocompromised and elderly individuals. This study aimed to determine the microbial loads of locally prepared herbal mixtures and detect extended spectrum beta-lactamase (ESBL) genes  in any isolated Gram-negative bacteria pathogen.

Methodology: Fifty local herbal mixtures were purchased randomly from three locations in Sagamu town (Sagamu market, Ita-Oba Road and Isale  Oko) in Ogun State, Nigeria. The mean total viable bacterial (MTVB), mean total coliform (MTC), and mean total fungal (MTF) counts were  determined by the plate count method. The bacterial isolates were streaked on differential bacteriological media while the fungi isolates were  grown on potato dextrose agar. The isolates were identified upon growth on culture media using conventional biochemical tests. Antibiotic  susceptibility pattern of the isolates was determined using Kirby-Bauer disk diffusion technique. Phenotypic detection of ESBL was done by the  modified double disc synergy test followed by amplification detection of blaTEM, blaCTX-M and blaSHV genes with polymerase chain reaction (PCR)  assay.

Results: Bacteria and fungi were isolated from 38 (76.0%) and 25 (50.0%) of the herbal samples respectively. Ten (20.0%) and 14 (28.0%) of the  samples had mean bacterial and fungal load that exceeded 105CFU/mL or g, respectively. Nineteen (38.0%) of the herbal samples analyzed had total  coliforms. Fifty-one isolates belonging to eight bacterial genera and 28 fungi isolates belonging to four fungal genera were obtained. Thirty-  two (62.7%) of the bacterial isolates were Gram-negative while 19 (37.3%) isolates were Gram-positive. Staphylococcus aureus was the most  common bacterial isolate (33.3%) while Aspergillus species was the most prevalent fungus (60.7%). Sixteen (84.2%) S. aureus and 26 (81.3%) Gram- negative isolates were multidrug resistant, and 6 (18.8%) of 32 Gram-negative isolates were ESBL producers. ESBL-encoding genes were detected in  7 (27%) of the 26 multidrug resistant Gram-negative bacteria with TEM and SHV being the most prevalent 4 (14.8%) while CTX-M was identified in  only one isolate.

Conclusion: This study reported the presence of microbial contaminants which exceeded the safety limits of 105 CFU/g according  to World Health Organization. The use of locally prepared herbal medicines poses a major health risk due to the lack of microbial quality standards.