An assessment of genetic fingerprinting tools for typing of multidrug-resistant and biofilm forming Staphylococcus aureus

Abstract

Staphylococcus aureus is a ubiquitous organism that has been associated with foodborne and nosocomial infections that may be difficult to treat due to the development of multiple antibiotic resistances. Genetic variation may also impact disease severity and transmission in susceptible populations. The occurrence and genetic diversity of multidrug-resistant and biofilm-forming S. aureus from drinking water troughs, milk, and milking environments at the North-West University dairy farm, were determined. A cross-sectional study design was employed to collect 39 samples from different sampling sites. Samples were screened by culture and the identity of the isolates was confirmed by PCR amplification of the Gap gene. Confirmed isolates were subjected to the Kirby-Bauer antibiotic susceptibility test against 11 antibiotics and antibiotic resistance genes (ARGs) detection by PCR. The biofilm-forming potential of the isolates were determined phenotypically. Genetic fingerprinting assays including REP, ERIC, and RAPD-PCR were used to determine the genetic relatedness of the drug-resistant of S. aureus. Out of 144 putative isolates, 124 (86.11%) harboured the gap gene. These isolates showed varied resistance abilities to cefoxitin (51.25%) penicillin (32%) and clindamycin (24,22%). Three ARGs, namely, mecA, blaZ, and tetO were amplified in 31.14%, 21.95% and 3.65% of the isolates respectively. The dominant MAR phenotypes were CLI-PEN-TET-FOX and PEN-ERY-RIF-FOX each in 15.38% of the isolates. Proportions of 34.83%, 42.86%, and 61.29% of the S. aureus isolates were capable of producing biofilms at 4 ºC, 25 ºC, and 37 ºC respectively. PCR-based DNA fingerprinting grouped the 33 S. aureus isolates into 19 distinct profiles. The study findings revealed MDR and biofilm-forming strains of S. aureus with high genetic diversity from various sampling sites, which could serve as a reservoir for the dissemination of severe and difficult-to-treat infection in susceptible populations.