Enzymatic Detection of the Growth of Staphylococcus aureus in Foods1

Abstract

A specific method has been developed for the extraction and measurement of staphylococcal nuclease in foods in which Staphylococcus aureus has grown. The method was used to. compare staphylococcal growth with nuclease production in foods under varying conditions of temperature, aerobiosis, and competition from other microorganisms. It was concluded that the nuclease is produced under any conditions that permit growth of S. aureus, and little or no interference with the test was encountered either from mixed, natural populations or from a variety of pure, laboratory cultures. Nuclease and enterotoxin A production were shown to vary in synchrony for the 234 (Casman) strain of S. aureus, and the sensitivity of the enzymatic detection of nuclease was comparable to the sensitivity of serological detection of enterotoxin A. It was found that 15 min at 121 C was required to reduce the nuclease activity in slurries of contaminated ham below the level present in the unheated slurry. The extraordinary heat resistance of the nuclease permits its detection even in foods heated subsequent to the growth of S. aureus. The nuclease analysis requires about 3 hr to complete and requires no unusual equipment or reagents.

A Simple Sensitive Method for Determining Staphylococcal Thermonuclease in Cheese

“…THE DETECTION of staphylococcal thermostable nuclease (thermonuclease) in food can serve as an indication of substantial growth of Staphylococcus aureus and possible presence of staphylococcal enterotoxins. This was established by a number of workers including Chesbro & Auborn (1967), Lachica et al (19724 and Cords & Tatini (1973). Determination of counts of Staph.…”

“…aureus, and, unlike Staph. aureus cells, has a marked resistance to extensive heating, storage and biological activity of other micro-organisms (Chesbro & Auborn 1967;Cords & Tatini 1973;Ibrahim & Baldock 1981).…”

“…A number of methods have been proposed for the determination of thermonuclease in foods (Chesbro & Auborn 1967;Lachica et al 1972~;Cords & Tatini 1973;Koupal & Deibel 1978;van Schouwenburg-van Foeken et al 1978). These methods either lacked sensitivity or were laborious, cumbersome and time-consuming.…”

DETECTION OF STAPHYLOCOCCUS AUREUS PRODUCTS IN FOODS USING ENZYME LINKED IMMUNOSORBENT ASSAY AND SPECTROPHOTOMETRIC THERMONUCLEASE ASSAY

“…The spectrophotometric assay methods were modifications of those of Chesbro and Auborn (1967) and Kamman and Tatini (1973). Purified micrococcal nuclease E. C. 3.1.4.7 (Worthington) and crude enzyme of boiled S. aureus cultures were employed.…”

Significance of Staphylocoagulase in Food Microbiology: A Review

“…Unfortunately, the procedure of enterotoxin detection is time consuming and laborious; thus researchers have been seeking easier methods to detect the presence of S. aureus indirectly and/or the enterotoxins in food. One of the compounds tested a s a n indirect measurement of S. aureus contamination in food is the heat stable deoxyribonuclease (Chesbro and Auborn 1967;Lachica 1980), a n enzyme produced extracellularly by S. aureus. The utilization of this enzyme a s a n indicator of contamination is due to its remarkable heat stability (Elston and Fitch 1946) which is similar to that of staphylococcal enterotoxins (Fung et al 1973).…”