Epidemiological Analysis of Staphylococcus aureus Isolated from Cows and the Environment of a Dairy Farm in Japan

Abstract

ABSTRACT. A case of Staphylococcus aureus intramammary infection (IMI) on a Japanese dairy farm was monitored for 9 months. S. aureus isolates from cows and environmental samples consisted of specific strains with sequence types 352 and 705, as determined by multilocus sequence typing. Clonal strains of these sequence types are isolated from cows worldwide, indicating that they are adapted to the bovine environment. These results explain why many IMI cases are persistent and lead to subclinical mastitis. The strain isolated from milk was identical to those isolated from the cows' bodies and cows carrying S. aureus, milking units, personnel, heifers and cats in the dairy barn. These locations and factors should be emphasized as sources and routes of strains causing IMI.

Bovine mastitis outbreak in Japan caused by methicillin-resistant Staphylococcus aureus New York/Japan clone

“…Most IMI cases caused by MSSA belonging to CC97 and CC705 are asymptomatic and are characterized by persistent infection, and thus they are difficult to eliminate from herds. 17 The MSSA of ST352 and ST705 in the present case were also consistently isolated from bovine milk without obvious mastitic symptoms throughout the investigation period as has been conventionally reported. 17 The reason that MSSA belonging to CC97 and CC705 can tenaciously infect the bovine udder may be that these strains possess a toxin with strong cytotoxicity against bovine immune cells (i.e., LukM/LukF′-PV).…”

“…17 The MSSA of ST352 and ST705 in the present case were also consistently isolated from bovine milk without obvious mastitic symptoms throughout the investigation period as has been conventionally reported. 17 The reason that MSSA belonging to CC97 and CC705 can tenaciously infect the bovine udder may be that these strains possess a toxin with strong cytotoxicity against bovine immune cells (i.e., LukM/LukF′-PV). 1 The S. aureus isolates from this outbreak that were ST352 and ST705 possessed LukM/LukF′-PV, as well.…”

“…17 Therefore, IMI due to S. aureus spreads insidiously and is very difficult to prevent and cure. 17 Moreover, bovine mastitis due to methicillin-resistant S. aureus (MRSA), well known as a typical multidrug-resistant organism, has been reported in all parts of the world and has attracted a great deal of attention. 12,19 Notably, MRSA possesses the mecA gene encoding PBP2a, which is a modified penicillin (PC)-binding protein that plays a role in methicillin resistance.…”

“…The PTs and genotypes of the MRSA isolates from milking machines and towels used in milking corresponded to those of the MRSA isolates from milk samples, therefore the process of milking is believed to be the main route of the spread of MRSA, as with MSSA. 17 The main infection sources of MRSA are also believed to be the milk and the bodies of carrier cows, as with MSSA. 17 Finally, the presence of MSSA and MRSA with identical genotypes was confirmed in this outbreak.…”

“…17 The main infection sources of MRSA are also believed to be the milk and the bodies of carrier cows, as with MSSA. 17 Finally, the presence of MSSA and MRSA with identical genotypes was confirmed in this outbreak. Furthermore, these MSSA and MRSA genotypes were isolated from the same cows.…”