Detection of Bacteroides fragilis Enterotoxin from Extraintestinal Clinical Isolates of B. fragilis Group Organisms

Kato, Naoya; Kato, Haru; Tanaka-Bandoh, Kaori; Watanabe, Kunitomo; Ueno, Kazue

doi:10.11150/kansenshogakuzasshi1970.69.903

Cited by 1 publication

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“…Several bacterial proteases are known to be cytotoxic (1,12,21). A metalloprotease toxin of Bacillus fragilis is associated with diarrheal disease in farm animals and humans and is an important virulence factor in B. fragilis associated with diarrhea and sepsis (20,29). Our in vitro study showed cell-rounding effects of the novel 34-to 36-kDa protease on several cell lines and indicated its cytotoxic activity.…”

Section: Discussionmentioning

confidence: 99%

Cytotoxic Activity of Coagulase-Negative Staphylococci in Bovine Mastitis

Zhang

Maddox

2000

Infect Immun

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Secreted toxins play important roles in the pathogenesis of bacterial infections. In this study, we examined the presence of secreted cytotoxic factors of coagulase-negative staphylococci (CoNS) from bovine clinical and subclinical mastitis. A 34-to 36-kDa protein with cell-rounding cytotoxic activity was found in many CoNS strains, especially in Staphylococcus chromogenes strains. The protein caused cell detachment and cell rounding in several cell lines, including HEp-2, Int 407, CHO-K1, and Y-1 cells. Native protein recovered from nondenatured polyacrylamide gel electrophoresis showed both cytotoxic activity and casein hydrolysis activity. The purified protein had a pH optimal at 7.2 to 7.5 and a pI of 5.1 and was heat labile. The proteolytic activity could be inhibited by zinc and metal specific inhibitors such as 1,10-phenanthroline and EDTA, indicating that it is a metalloprotease. Protein mass analysis and peptide sequencing indicated that the protein is a novel metalloprotease. Different bacterial strains expressed variable levels of 34-to 36-kDa protease, which may provide an indication of strain virulence.Coagulase-negative staphylococcus (CoNS) has been considered a minor pathogen of bovine mastitis; however, many studies recently have shown the importance of CoNS infection in the bovine mammary gland. Several studies indicated that CoNS is the most frequently recovered isolate from mastitis samples, especially in first lactation and unbred heifers (16,18,26,30). CoNS also caused mastitis problems in other species such as milking goats (11). CoNS infections usually are more mild than Staphylococcus aureus (one coagulase-positive Staphylococcus sp.) which is a major and contagious pathogen of bovine mastitis. The somatic cell counts of CoNS-infected cows are generally two-to threefold higher than that of uninfected cows (18, 30). CoNS-infected mammary tissues exhibited greater leukocyte infiltration and increased connective tissue stroma over an uninfected control (37). One study showed that CoNS infections caused an 8.7% loss in milk production from a 305-day milk yield total (36).Even though more researchers have realized the importance of CoNS intramammary infections, the virulence factors of CoNS remain poorly understood. The virulence factors of staphylococci have been studied most extensively in the species of S. aureus. Secreted toxins play very important roles in the pathogenesis of S. aureus (9, 10, 41). S. aureus strains isolated from bovine mastitis have been shown to express alpha, beta, gamma, and delta toxins, leukocidins, enterotoxin, and coagulase (8, 25). CoNS strains also produce several toxins and enzymes that could contribute to virulence, such as hemolysin, leucocidin, lipase, proteases, and DNase (17, 34, 39). Many CoNS strains isolated from mastitis samples had higher protease, DNase, and lecitinase activity than that of CoNS from normal cows (19). However, the roles of these enzymes on the pathogenesis of CoNS are unclear. A delta-like toxin from CoNS strains causes membrane ble...

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Section: Discussionmentioning

confidence: 99%