Positive Regulation of Staphylococcal Enterotoxin H by Rot (Repressor of Toxin) Protein and Its Importance in Clonal Complex 81 Subtype 1 Lineage-Related Food Poisoning.
We previously demonstrated the clonal complex 81 (CC81) subtype 1 lineage is the major staphylococcal food poisoning (SFP)-associated lineage in Japan (Y. Sato'o et al., J Clin Microbiol 52:2637-2640, 2014, http://dx.doi.org/10.1128/JCM.00661-14). Strains of this lineage produce staphylococcal enterotoxin H (SEH) in addition to SEA. However, an evaluation of the risk for the recently reported SEH has not been sufficiently conducted. We first searched for staphylococcal enterotoxin (SE) genes and SE proteins in milk samples that caused a large SFP outbreak in Japan. Only SEA and SEH were detected, while there were several SE genes detected in the samples. We next designed an experimental model using a meat product to assess the productivity of SEs and found that only SEA and SEH were detectably produced in situ. Therefore, we investigated the regulation of SEH production using a CC81 subtype 1 isolate. Through mutant analysis of global regulators, we found the repressor of toxin (Rot) functioned oppositely as a stimulator of SEH production. SEA production was not affected by Rot. seh mRNA expression correlated with rot both in media and on the meat product, and the Rot protein was shown to directly bind to the seh promoter. The seh promoter sequence was predicted to form a loop structure and to hide the RNA polymerase binding sequences. We propose Rot binds to the promoter sequence of seh and unfolds the secondary structure that may lead the RNA polymerase to bind the promoter, and then seh mRNA transcription begins. This alternative Rot regulation for SEH may contribute to sufficient toxin production by the CC81 subtype 1 lineage in foods to induce SFP.
Department of Bacteriology, Hiroshima University Graduate School of Biomedical & Health Sciences, Hiroshima City, Hiroshima, Japan The United Graduate School of Veterinary Sciences, Gifu University, Gifu City, Gifu, Japan Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan.
Yusuke
Y
Sato'o
Department of Bacteriology, Hiroshima University Graduate School of Biomedical & Health Sciences, Hiroshima City, Hiroshima, Japan.
Junzo
J
Hisatsune
Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan.
Yuria
Y
Nagasako
Department of Microbiology and Immunology, Hirosaki University Graduate School of Medicine, Hirosaki, Aomori, Japan.
Hisaya K
HK
Ono
The United Graduate School of Veterinary Sciences, Gifu University, Gifu City, Gifu, Japan Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan.
Katsuhiko
K
Omoe
Department of Bacteriology, Hiroshima University Graduate School of Biomedical & Health Sciences, Hiroshima City, Hiroshima, Japan sugai@hiroshima-u.ac.jp.
Motoyuki
M
Sugai
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004768:Enterotoxins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D007564:Japan; D008892:Milk / Q000382:microbiology*; D060885:Multiplex Polymerase Chain Reaction; D060888:Real-Time Polymerase Chain Reaction; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D013202:Staphylococcal Food Poisoning / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D004768:Enterotoxins; D012097:Repressor Proteins; C402489:Staphylococcal enterotoxin H; C408643:rot protein, Staphylococcus aureus