Abstract
Food-borne methicillin resistant Staphylococcus aureus (MRSA) is involved in two-fold higher mortality rate compared to methicillin susceptible S. aureus (MSSA). Eventhough Mysuru recognized as cleanest city in the world, prevalence of food contamination is not detailed. The aim is to screen food samples from Mysuru area and to characterize MRSA strain, employing MALDI-Biotyper, multiplex PCR to distinguish between MRSA and MSSA by PCR-coupled single strand conformation polymorphism (PCR-SSCP). Of all the food-borne pathogens, S. aureus contamination accounts for 94.37 ± 0.02% (P < 0.01), strains characterized by means of nuc genes, followed by species specific identification by Coa, Eap and SpA genes and multiplex PCR to confirm the presence of three methicillin resistant staphylococcal species simultaneously using nuc and phoP genes. Amplification of mecA gene in 159 isolates confirmed that all strains are methicillin resistant, except UOM160 (MSSA) and multi-drug resistant (MDR) in 159 isolates confirmed by 22 sets of β-lactam antibiotics. MSSA and MDR-MRSA were discriminated by PCR-SSCP using nuc gene for the first time. From the present studies, compared to conventional methods MALDI-Biotyper emerged as an effective, sensitive (>99%), robust (<2 min), and alternative tool for pathogen identification, and we developed a PCR-SSCP technique for rapid detection of MSSA and MRSA strains.
Highlights
Staphylococcus aureus[1] is recognized as one of the most common pathogens responsible for food poisoning and causing various infections in animal and humans[2]
The methicillin susceptible S. aureus (MSSA) strain acquiring genetic element ‘Staphylococcal cassette chromosome’ called mec (SCC mec) which reduces affinity to the group of β-lactam antibiotics by encoding the altered penicillin-binding protein 2a -PBP2a expressed by mecA gene and allowed bacteriocin to assemble cell wall in presence of drugs4, 6? Recent reports state that, acquisition of resistance in Staphylococci is by transposons and/or plasmids mediated by conjugate transfer, which spreads resistance elements among Staphylococci species
Food samples collected from Devaraj Urs road and Bamboo bazaar areas are highly contaminated as compared to others
Summary
Staphylococcus aureus[1] is recognized as one of the most common pathogens responsible for food poisoning and causing various infections in animal and humans[2]. This facultative anaerobe is a natural flora in 20–30% of people, present within the anterior nares and on the skin. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has emerged as a rapid and robust tool for microbial identification and diagnosis. In this proteomic approach, microbes are identified using either intact cells or cell extracts. The process is rapid, sensitive, and economical because the data generated in MALDI-TOF-MS was compared against inbuilt proprietary database of well characterized reference strains[12, 13]
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