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. 2020 Apr 2;9(4):156.
doi: 10.3390/antibiotics9040156.

Genotypic and Phenotypic Evaluation of Biofilm Production and Antimicrobial Resistance in Staphylococcus aureus Isolated from Milk, North West Province, South Africa

Marie Ebob Agbortabot Bissong  1   2 , Collins Njie Ateba  1   3
Affiliations

Genotypic and Phenotypic Evaluation of Biofilm Production and Antimicrobial Resistance in Staphylococcus aureus Isolated from Milk, North West Province, South Africa

Marie Ebob Agbortabot Bissong et al. Antibiotics (Basel). .

Abstract

Background: Biofilm formation in S. aureus may reduce the rate of penetration of antibiotics, thereby complicating treatment of infections caused by these bacteria. The aim of this study was to correlate biofilm-forming potentials, antimicrobial resistance, and genes in S. aureus isolates. Methods: A total of 64 milk samples were analysed, and 77 S. aureus were isolated. Results: Seventy (90.9%) isolates were biofilm producers. The ica biofilm-forming genes were detected among 75.3% of the isolates, with icaA being the most prevalent (49, 63.6%). The icaB gene was significantly (P = 0.027) higher in isolates with strong biofilm formation potentials. High resistance (60%-90%) of the isolates was observed against ceftriaxone, vancomycin, and penicillin, and 25 (32.5%) of S. aureus showed multidrug resistance (MDR) to at least three antibiotics. Five resistance genes, namely blaZ (29, 37.7%), vanC (29, 37.7%), tetK (24, 31.2%), tetL (21, 27.3%), and msrA/B (16, 20.8%) were detected. Most MDR phenotypes possessed at least one resistance gene alongside the biofilm genes. However, no distinct pattern was identified among the resistance and biofilm phenotypes. Conclusions: The high frequency of potentially pathogenic MDR S. aureus in milk samples intended for human consumption, demonstrates the public health relevance of this pathogen in the region.

Keywords: Staphylococcus aureus; antimicrobial resistance; biofilm; genes; milk; public health.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Agarose (1% w/v) gel of the ica gene products of S. aureus isolates. Lane M = DNA marker (100 base pairs DNA Ladder); Lane 1 = icaA amplicon of positive control (S. aureus ATCC 25923); Lane 2 = icaA amplicon of negative control (E. coli ATCC 25922); Lanes 3–6 = icaA amplicons; Lane 10 = icaB amplicons; Lanes 11–14 = icaC amplicons; Lanes 15–19 = icaD amplicons.
Figure 2
Figure 2
A dendrogram showing the clustering of biofilm genes based on OD680 of S. aureus isolates (the dendrogram was obtained by using the unweighted paired group method).
Figure 3
Figure 3
Antimicrobial resistance of S. aureus isolates.
Figure 4
Figure 4
A Boxplot of penicillin diameter and blaZ gene (0=blaZ-negative, 1=blaZ-positive).
See this image and copyright information in PMC

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