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Isolation of methicillin-resistant coagulase-negative staphylococci from chickens
J Kawano1, A Shimizu, Y Saitoh
1Department of Animal Science, Faculty of Agriculture, Kobe University, Japan.
Abstract:
Methicillin-resistant coagulase-negative staphylococci were isolated from the nares and skin of 1- to 8-week-old healthy chickens in three flocks from a farm. Isolation of methicillin-resistant coagulase-negative staphylococci was positive for 72 (25.7%) of the 280 chickens tested, with the frequency varying from 2.2 to 100% according to flock. A total of 45 appropriate isolates were selected and subjected to identification. Of the 45 methicillin-resistant coagulase-negative staphylococcal isolates selected, 37 were identified as Staphylococcus sciuri, 5 were identified as Staphylococcus epidermidis, and 3 were identified as Staphylococcus saprophyticus. The distribution of the species was different among the flocks. Comparative analysis of the SmaI-digested chromosomal DNA by pulsed-field gel electrophoresis revealed that the isolates could have originated from a single clone of each of S. sciuri and S. saprophyticus and three clones of S. epidermidis. By two methods based on the PCR technique, the mecA gene was detected in all five representative isolates of each methicillin-resistant coagulase-negative staphylococcal clone. The nucleotide sequence of a PCR fragment obtained from an isolate of S. sciuri was completely identical to the corresponding region of mecA genes reported in human methicillin-resistant Staphylococcus aureus isolates and Staphylococcus epidermidis isolates. The representative methicillin-resistant coagulase-negative staphylococcal isolates were resistant to many beta-lactam antibiotics, and some isolates were also resistant to macrolide and aminoglycoside antibiotics. This is the first evidence of the existence of methicillin-resistant coagulase-negative staphylococci from animals possessing the mecA gene.
Insights
Methicillin-resistant coagulase-negative staphylococci carrying the mecA gene were found in healthy chickens. This study provides the first evidence of these resistant bacteria in animals, highlighting potential public health concerns.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Resistance
- Molecular Biology
Background:
- Methicillin-resistant coagulase-negative staphylococci (MRCNs) are a growing concern in human and animal health.
- The presence and characteristics of MRCNs in poultry, particularly in young, healthy chickens, remain under-investigated.
- Understanding the genetic basis and clonal origins of MRCNs in food animals is crucial for assessing transmission risks.
Purpose of the Study:
- To investigate the prevalence and identify the species of methicillin-resistant coagulase-negative staphylococci in healthy chickens.
- To determine the presence of the mecA gene in these isolates.
- To analyze the clonal relatedness and antibiotic resistance profiles of the identified MRCNs.
Main Methods:
- Bacterial isolation from chicken nares and skin.
- Species identification using standard microbiological techniques.
- Detection of the mecA gene via Polymerase Chain Reaction (PCR).
- Pulsed-field gel electrophoresis (PFGE) for chromosomal DNA analysis and clonal typing.
- Antibiotic susceptibility testing for beta-lactam, macrolide, and aminoglycoside antibiotics.
Main Results:
- Methicillin-resistant coagulase-negative staphylococci were isolated from 25.7% of 280 chickens across three flocks.
- Identified species included Staphylococcus sciuri (37 isolates), Staphylococcus epidermidis (5 isolates), and Staphylococcus saprophyticus (3 isolates).
- The mecA gene was detected in all analyzed MRCN clones, with nucleotide sequences identical to those found in human isolates.
- Isolates exhibited resistance to multiple beta-lactam antibiotics, and some were also resistant to macrolides and aminoglycosides.
Conclusions:
- This study presents the first evidence of methicillin-resistant coagulase-negative staphylococci harboring the mecA gene in healthy chickens.
- The findings indicate a potential reservoir of antimicrobial resistance in poultry, with implications for public health.
- Further research is warranted to understand the transmission dynamics and impact of MRCNs in food-producing animals.