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Genotyping of Staphylococcus aureus by Ribosomal Spacer PCR RS-PCR
Published on: November 4, 2016
Genotyping of methicillin-resistant Staphylococcus aureus (MRSA) isolated from milk and dairy products in South Italy
M G Basanisi1, G La Bella1, G Nobili1
1Istituto Zooprofilattico Sperimentale della Puglia e della Basilicata, Via Manfredonia, 20, 71121 Foggia, Italy.
Abstract:
Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogen emerging in hospitals as well as community and livestock. MRSA is a significant and costly public health concern because it may enter the human food chain and contaminate milk and dairy products causing foodborne illness. This study aimed to determine the occurrence and the characteristics of MRSA isolated from 3760 samples of milk and dairy products in a previous survey conducted in southern Italy during 2008-2014. Overall out of 484 S. aureus strains isolated, 40 (8.3%) were MRSA and were characterized by spa-typing, Multi-Locus Sequence Typing, SCCmec typing, Staphylococcal enterotoxins (SEs) genes, Panton-Valentine Leukocidin (PVL) genes and ability to form biofilm. The most frequently recovered STs were ST152 (t355-67.5%), followed by ST398 (t899, t108-25%), ST1 (t127-5%) and ST5 (t688-2.5%). All isolates harboured the SCCmec type V (92.5%) or IVa (25%). In one isolate (2.5%), ST398/t899, the SCCmec resulted not detected. Three isolates (7.5%) carried one or more enterotoxin encoding genes (one strain had seg, sei, sem, sen and seo genes; two strains had seh gene). The 50% of isolated strains harboured PVL-encoding genes. Molecular analysis for icaA and icaD genes showed: 72.5% icaA and icaD positive, 25% only icaD gene and one icaA and icaD negative. The detection of MRSA in food of animal origin is a potential health hazard, thus it is necessary monitoring of food-producing animals and improving hygiene standards in food practices in order to reduce the microbiological risk to minimum.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) was found in 8.3% of milk and dairy products in southern Italy. This pathogen poses a food safety risk, necessitating enhanced monitoring and hygiene practices.
Area of Science:
- Food safety and public health
- Microbiology and infectious diseases
- Veterinary medicine and animal husbandry
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) is a significant public health concern due to its emergence in various settings, including livestock.
- MRSA contamination in milk and dairy products presents a potential risk for foodborne illness, impacting the human food chain.
- Previous surveys have indicated the presence of Staphylococcus aureus in food products, highlighting the need for further investigation into MRSA occurrence.
Purpose of the Study:
- To determine the prevalence and characteristics of MRSA in milk and dairy products from southern Italy.
- To analyze the genetic profiles, including spa-typing, Multi-Locus Sequence Typing (MLST), and SCCmec typing, of isolated MRSA strains.
- To investigate the presence of virulence factors such as Staphylococcal enterotoxin (SE) genes and Panton-Valentine Leukocidin (PVL) genes, as well as biofilm formation capability.
Main Methods:
- Isolation and identification of Staphylococcus aureus from 3760 milk and dairy product samples.
- Characterization of MRSA isolates using spa-typing, MLST, and SCCmec typing.
- Detection of Staphylococcal enterotoxin genes, PVL genes, and biofilm-forming genes (icaA, icaD).
Main Results:
- Out of 484 Staphylococcus aureus strains, 40 (8.3%) were identified as MRSA.
- The predominant sequence types (STs) were ST152 (67.5%), ST398 (25%), ST1 (5%), and ST5 (2.5%).
- SCCmec type V and IVa were commonly detected. Enterotoxin genes were found in 7.5% of isolates, and 50% harbored PVL genes. Biofilm-related genes (icaA/icaD) were present in most strains.
Conclusions:
- The detection of MRSA in milk and dairy products highlights a potential health hazard associated with food of animal origin.
- Continuous monitoring of food-producing animals and stringent hygiene standards in food handling practices are crucial.
- Implementing robust control measures is essential to minimize the microbiological risk posed by MRSA in the food supply chain.
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