Staphylococcal cassette chromosome mec (SCCmec) characterization and molecular analysis for methicillin-resistant Staphylococcus aureus and novel SCCmec subtype IVg isolated from bovine milk in Korea.
OBJECTIVE
To identify the staphylococcal cassette chromosome mec (SCCmec) types of methicillin-resistant Staphylococcus aureus (MRSA) isolated from bovine milk, and examine the genetic relatedness between MRSA from bovine milk and MRSA from human isolates.


METHODS
Antimicrobial susceptibility tests were performed on MRSA isolated from bovine milk. PCR and sequencing analysis were performed to determine the SCCmec type of MRSA, and to confirm their toxin carriage. Genetic relatedness among the bovine isolates and between bovine and human isolates was detected with PFGE and multilocus sequence typing (MLST).


RESULTS
Fourteen MRSA and a silent mecA-carrying methicillin-susceptible S. aureus (smMSSA) were isolated from the milk of cows with an isolation ratio of 0.18%. SCCmec of 14 MRSA strains were designated as new subtype IVg, and one smMSSA strain was not classified. All 14 MRSA strains shared Panton-Valentine leucocidin (PVL) and staphylococcal enterotoxin D (SED), SEI and SEJ; the smMSSA strain had only PVL. All MRSA and smMSSA isolates showed no multidrug resistance and had community-acquired MRSA (CA-MRSA) characteristics. PFGE revealed that all isolates except the smMSSA belonged to the same genetic lineage, and MLST analysis showed that they had no genetic relatedness with CA-MRSA which had caused human infection in Korea.


CONCLUSIONS
MRSA isolated from bovine milk harboured a unique SCCmec subtype, and they may not be correlated with the emergence of CA-MRSA in human infection in Korea.
Kwon
Nam Hoon
NH
Department of Microbiology, College of Veterinary Medicine and School of Agricultural Biotechnology, Seoul National University, Shillim dong, Gwanak gu, Seoul 151-742, Korea.
Park
Kun Taek
KT
Moon
Jin San
JS
Jung
Woo Kyung
WK
Kim
So Hyun
SH
Kim
Jun Man
JM
Hong
Soon Keun
SK
Koo
Hye Cheung
HC
Joo
Yi Seok
YS
Park
Yong Ho
YH
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002417:Cattle; D006801:Humans; D007723:Korea; D008712:Methicillin / Q000494:pharmacology; D016106:Methicillin Resistance / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology*; D008969:Molecular Sequence Data; D046915:Penicillin-Binding Proteins; D010802:Phylogeny; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification*
D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; C487789:mecA protein, Staphylococcus aureus; D008712:Methicillin