The enumeration of thermotrophic types amongst the Enterobacteriaceae colonizing perishable foods

Abstract

A total of 41 pure cultures of Enterobacteriaceae, comprising 32 thermotrophic and nine psychrotrophic strains, pathogens or marker organisms, were examined for numbers of colony forming units obtained at 37 degrees and 42.5 degrees C (thermotrophs) and 30 degrees C (psychrotrophs), when surface-plated on a rich infusion agar and violet red bile agar. In addition 42 food and water samples, collected in a rural area of the Philippines, were examined by surface inoculating violet red bile AIPC (agar immersion plating and contact; 'dip') slides and incubating at 37 degrees and 42.5 degrees C. At 42.5 degrees C there was almost total recovery of the thermotrophic Enterobacteriaceae, whereas the psychrotrophic strains were completely suppressed. At 37 degrees C the psychrotrophs were only slightly inhibited. The Philippine foods, predominantly cooked meals, milk and drinking water, appeared to be significantly colonized by thermotrophic Enterobacteriaceae. It is concluded that incubation at 42.5 degrees C satisfactorily selects enteropathogenic and other enteric Enterobacteriaceae while suppressing the psychrotrophic types which are mainly of vegetable origin. It is emphasized that, regardless of the temperature used, a resuscitation procedure for Enterobacteriaceae populations that have incurred sublethal injury in food has to precede counts on or in the usual selective media.

Some aspects of the gastrointestinal microflora of veal calves fed different rations: A pilot study

“…Thermotrophic enterobacteriaceae: poured plates of Violet Red Bile Glucose agar (VRBG; Oxoid CM 485) with overlayer, incubated for 18 hours at 42,5° C (27). Pseudomonas aeruginosa: spread plates of Pseudomonas Agar Base (PAB; Oxoid SR 103) + Cetrimide/Nalidixine Supplement (CN; Oxoid SR 102), incubated for 48 hours at 42.5°C (6).…”

Rapid Detection of Excessive CFU Counts of Enterobacteriaceae, S. aureus and Yeasts by Nitrate Reduction/Glucose Dissimilation (NGD) Monitoring in Selective Media

“…Eight Gram positive bacterial isolates, nine Gram negative rod shaped bacteria strains, and one yeast (Listed in Table 1) were used in this investigation. Their origin has been described in detail in previous studies (Mossel et al, 1975(Mossel et al, , 1986van Doome et al, 1982;Visser et al, 1985).…”

“…Their origin has been described in detail in previous studies (Mossel et al, 1975(Mossel et al, , 1986van Doome et al, 1982;Visser et al, 1985).…”

“…3.0 4.5 5.5 3.5 5.0 6.5 3.0 5.0 6.0 3.0 4.5 5.5 (Oxoid CM 485) by the overlayered technique using 1 ml amounts of appropriate food dilutions, and incubated for 24 hr at 42.5"C (Mossel et al, 1986). 5. aureus was counted by spreading 0.1 mL aliquots of appropriate food dilutions in duplicate on Baird Parker agar medium (Oxoid CM 275) and incubating at 42.5"C for 24 hr (van Doorne et al, 1982).…”

“…The purpose of this study was: (1) to increase the velocity Authors of both biochemical responses; and (2) to limit detection signals to bacteria of health significance by incubation at 42.X, since most Enterobacteriaceae of health significance (Mossel et al, 1986) and Staphylococcus aureus (van Doome et al, 1982) are thermotrophic species.…”