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Fig. 2 | BMC Microbiology

Fig. 2

From: Genomic and phenotypic profiling of Staphylococcus aureus isolates from bovine mastitis for antibiotic resistance and intestinal infectivity

Fig. 2

Antibiotic-resistance mechanisms and virulence factors in S. aureus isolates. a Assessment of efflux pump activity in five antibiotic-resistant and five susceptible isolates. EtBr efflux assay was performed using 3 µg/mL of EtBr and 30 µg/mL of CPZ. The fluorescent intensity (530 nm/590 nm) was monitored for 60 min after reenergizing the bacterial cells to trigger EtBr efflux with glucose (0.4% v/v). b Assessment of ß-lactamase enzyme activity in the isolates. The isolates were subjected to a Nitrocefin assay where the absorbance of the cell-free extract mixed with Nitrocefin was detected at 490 nm for 15 min. c Distribution of hemolysin manifestation by the 43 isolates. d Alpha hemolysin manifestation by Sa30. Each isolate was cultured in TSA plates with 5% sheep blood for 24 h. The hemolysis was detected visually by the translucency around the bacterial colony. e Distribution of biofilm-forming ability by the 43 isolates. The biofilm formation was assessed using a crystal violet assay. All isolates were classified into weak, moderate, and strong biofilm-formers based on their biofilm-forming ability. f Fluorescence microscopic image of extracellular polymeric substances (EPS) and Sa30 cells. A green (505 nm) filter was used to acquire the GFP-labeled Sa30 biofilms using a high-content screening microscope, Cell Discoverer 7. Alphabets (in tabular data) indicate a significant difference (p < 0.05). ‘N/A’ stands for not applicable. More data on the resistance mechanisms and virulence factors are provided in Tables S3 and S5. The experiment was performed in quadruplicates and repeated thrice to ensure reproducibility

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