Production of Exfoliative Toxin A by Staphylococcus aureus Isolated from Mastitic Cow's Milk and Farm Bulk Milk.

Abstract

ABSTRACT. The production of exfoliative toxins A and B (ETA and ETB) by Staphylococcus aureus isolated from mastitic cow's milk and farm bulk milk was examined by the reverse passive latex agglutination method (RPLA). ETA was detected in 2 (1.2%) of 162 isolates from mastitic cow's milk and in 1 (0.6%) of 166 isolates from farm bulk milk. RPLA titers of these isolates were much lower than in human isolates. No ETB was detected in any of the isolates tested. These ETA-positive isolates belonged to bovine ecovar. They were non-typable using the international phage set for human strains. When these ETA-positive isolates were subcutaneously inoculated into neonatal mice, general exfoliation of the epidermis accompanied by the so-called Nikolsky sign was not recognized. By the immunoblotting and PCR methods, however, ETA and eta gene were recognized in the ETA-positive isolates from mastitic cow's milk and farm bulk milk. These data suggest that ETA is also produced by bovine isolates of S. aureus, but in smaller quantities. -KEY WORDS: bovine mastitis, exfoliative toxin A, Staphylococcus aureus.J. Vet. Med. Sci. 60(11): 1281-1283, 1998 farm bulk milk, respectively, obtained at 71 dairy farms in Ishikawa Prefecture during the period from 1991 to 1994. Six human strains of S. aureus, isolated from patients affected with staphylococcal scalded-skin syndrome, were used as ETA and ETB positive controls. The organisms were inoculated into 5 ml of brain heart infusion (Nissui Pharmaceutical Co., Ltd., Tokyo, Japan) and cultured at 37°C for 18 hr. The culture fluids were centrifuged at 12,000 × g at 4°C for 5 min and then the resulting culture supernatants were tested for ETA and ETB by a reverse passive latex agglutination (RPLA) test using EXT-RPLA kit (Denka Seiken Co., Ltd., Tokyo, Japan). Briefly, 20 µl of the culture supernatants, diluted 5-fold, were placed into the wells of V-type microtiter plates. An equal volume of latex particles, sensitized with specific anti-ETA or anti-ETB immunoglobulins, was added to each well of the plates. After thorough mixing, the plates were incubated at room temperature for 24 hr. When the aggulutinating reaction was obtained, the culture supernatants of the positive isolates were serially diluted twofold in microtiter plates to determine the quantity of ETA or ETB.

PCR detection of staphylococcal enterotoxin genes and exfoliative toxin genes in methicillin-resistant and methicillin-susceptible Staphylococcus aureus strains from raw human breast milk

“…sea was the most prevalent enterotoxin gene detected in this study (24.1%), similar to the result reported by Mehrotra et al [10] (19.6%) versus 41% for Rall et al [1] and 44.4% for Xie et al [39]. The eta gene rate observed in this study was 12.9%, compared to 2.4% and 0.6% for Hayakawa et al [41], 0.9% for Xie et al [39], and 0.8% for Wang et al [40].…”

Genotypic characterization ofStaphylococcus aureusisolated from bovines, humans, and food in Indonesia

“…In contrast to eta , etb was not found in this study. Hayakawa et al [10] reported that the production of exfoliative toxins by S. aureus isolates from cattle with bovine mastitis seems to be rare.…”

Prevalence of staphylococcal enterotoxins, toxin genes and genetic-relatedness of foodborne Staphylococcus aureus strains isolated in the Marmara Region of Turkey

“…Similar to our results, Oh et al (2007) and Karahan et al (2009) could not find eta and etb in S. aureus isolated from ready-to-eat food and mastitic milk samples. On the other hand, Hayakawa et al (1998) reported ETA in 1.2% (2/162) and 0.6% (1/166) of S. aureus isolates from mastitic cows' milk and bulk milk, respectively. Interestingly, these eta-positive S. aureus isolates did not cause general exfoliation of the epidermis accompanied by the socalled Nikolsky sign when inoculated into neonatal mice.…”

“…Moreover, clinical strains of S. aureus are known to produce immunologically distinct exfoliative toxin A and/or B (Bailey et al, 1980). The production of exfoliative toxin A by S. aureus isolated from foods and animals has been reported (Adesiyun et al, 1991;Hayakawa et al, 1998).…”