Effects of Varying Concentrations of Novobiocin Incorporated into Two Salmonella Plating Media on the Recovery of Four Enterobacteriaceae

Abstract

Hydrogen sulfide-producing strains of salmonellae, Escherichia coli, Citrobacter freundii, and Proteus mirabilis were isolated from fresh pork sausage. All the strains produced black-centered colonies on Hektoen enteric agar (HE). On xylose lysine deoxycholate agar (XLD), C. freundii produced yellow colonies, and the strains of the other three genera formed black-centered colonies. The selectivity of HE and XLD for salmonellae was improved by the addition of novobiocin to both media. With increasing concentrations of novobiocin, the degree of growth inhibition for the four genera was less on HE than on XLD. Novobiocin concentrations of 80 jug/ml in HE and 5 ,ug/ml in XLD did not affect the growth or colonial morphology of salmonellae. When 80 ,ug of novobiocin per ml was incorporated into HE, P. mirabilis strains were not recovered, 40% of C. freundii strains failed to form black-centered colonies, and growth of E. coli strains was not affected but colonies were altered without eliminating the black centers. When novobiocin at 5 ,tg/ml was incorporated into XLD, colonies ofP. mirabilis strains were not recovered, C. freundii formed yellow colonies, and the colonies of the H2S-producing E. coli strains were unaffected.

Improved Salmonella recovery from moderate to highly polluted waters

“…The findings are in agreement with previous results reported for sodium novobiocin addition to the enrichment broth (Jeffries 1959) or to the plating media (Hargrove et al 1971 ;Boothroyd & Baird-Parker 1973;Hoben et al 1973;Restaino et al 1977). The method described in the We especially thank Manuel Serra for his generous contributions to the statistical analysis.…”

“…Several authors (Jeffries 1959;Hargrove et al 1971;Boothroyd & Baird-Parker 1973;Hoben et al 1973;Restaino et al 1977) This antibiotic inhibits the growth of Proteus, Pseudomonas and Escherichia coli which are usually present in large numbers in surface waters. A much modified Rappaport medium (R10/43"C) recently described (Vassiliadis et al 1978) permits the recovery of a wide range of salmonellas.…”

DETERMINATION OF THE EFFECTIVENESS OF NOVOBIOCIN ADDED TO TWO AGAR PLATING MEDIA FOR THE ISOLATION OF SALMONELLA FROM FRESH MEAT PRODUCTS

“…The stock solution of N was filtersterilized through a 0.45-p membrane filter (Falcon). A specific volume of N stock solution and a predetermined volume of media were aseptically mixed to obtain 5 and 80 pg/ml (Restaino et al 1977) of the antibiotic in XLD and HE agars, respectively. the method described by A.…”

“…Only H S positive Salmonella, producing black-centered colonies on XLD and HE with a n without N, were considered for Salmonella presumptive isolates. As shown in a previous study (Restaino et al 1977), P. mirabilis was dominant false positive on XLD agar (88.4%). On HE agar the false positives were distributed between P. mirabilis (53.8%) and freundii (38.5%).…”

“…which grow well on plain BG agar and interfere with Salmonella isolation from feeds and meats (Litchfield 1973). and without 5 pg/ml and 80 pg/ml (Restaino et al 1977) of N, respectively, and BG agar with 8 mg of sulfadiazine/100 ml of medium was compared for isolating salmonellae from various fresh meat products.…”