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THE EFFECT OF AEROBIC MESOPHILIC MICROFLORAL LEVELS ON THE ISOLATION OF INOCULATED LISTERIA MONOCYTOGENES STRAIN LM82 FROM SELECTED FOODS (1990)

TRAN, TONY T. ; STEPHENSON, PATRICIA ; HITCHINS, ANTHONY D.

Oxford, UK : Blackwell Publishing Ltd

Journal of food safety 10 (1990), S. 0

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ISSN: 1745-4565

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology

Notes: The effect of aerobic mesophilic microfloral concentration on the isolation of Listeria monocytogenes LM82 was studied in 31 (18 cheeses and 7 noncheese) retail foods having standard plate counts of 101 to 108 colony forming units (CFU)/g. Foods were spiked with L. monocytogenes and enriched at 30°C for 24 h in a selective enrichment broth used in a U.S. Food and Drug Administration method. Inoculum levels for isolation on modified McBride agar ranged from 0.1 to 〉 5 × 103 with a geometric mean value of 5 inoculated CFU/g or 1.4 CFU/g. Pure Enterococcus (Streptococcus) faecalis (0 to 6 × 106 inoculated CFU/mL) in the absence of food matrix had no effect on the enrichment of L. monocytogenes. Ease of isolation of LM82 was independent of the food microflora concentration both generally and in the specific food type of 9 Brie cheeses. Competition, when it occurs, therefore, may be due to specific bacterial competitors rather than bacterial numbers.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-4565.1990.tb00027.x

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RECOVERY LIMITS OF HEAT-INJURED LISTERIA MONOCYTOGENES FROM ENRICHMENT BROTH AND ENRICHED CULTURES OF INOCULATED FOODS (1993)

TRAN, TONY T. ; HITCHINS, ANTHONY D.

Oxford, UK : Blackwell Publishing Ltd

Journal of food safety 13 (1993), S. 0

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ISSN: 1745-4565

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology

Notes: Recovery of heat-injured Listeria monocytogenes strain LM82 was evaluated quantitatively in Listeria enrichment broth (LEB) and in enriched cultures of cooked shrimp and Brie cheese. LM82 cells [108 colony forming units (CFU)/ml] were heated for 60 min at 52C in phosphate-buffered saline. After 24 and 48 h enrichment, injured LM82 (6 replicates at each of 5 inoculation levels) were isolated on 3 selective media: lithium chloride-phenylethanol-moxalactam agar (LPMA), modified McBride agar (MMA) and Oxford agar (OXA). The recovery limit was expressed as a 50% end point value (RL50), which is the calculated inoculation value necessary to recover LM82 on half of the replicates of each type of isolation agar plate after streaking from the enrichment of measured inoculum. The RL50 values for injured cells were comparable to those of uninjured cells after 48 h enrichment in LEB without food. The type of isolation agar did not affect the RL50 value, although with food, MMA gave consistently but not significantly higher values, i.e., recovery inferior to that of LPMA and OXA. RL50 values were higher in Brie and cooked shrimp, presumably because of the competitive microflora in those foods. Addition of lactose or pyruvate to LEB improved recovery but had little or no effect when foods were present.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-4565.1993.tb00105.x

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COMPETITION OF FOOD BACTERIA WITH LISTERIA MONOCYTOGENES DURING ENRICHMENT CULTURE (1991)

DALLAS, HUGH L. ; TRAN, TONY T. ; POINDEXTER, CHRISTINE E. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Journal of food safety 11 (1991), S. 0

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ISSN: 1745-4565

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology

Notes: Thirty-two foodborne bacterial isolates were tested as potential competitors of Listeria monocytogenes strain LM82 during enrichment because of their resistance to the selective agents in Listeria enrichment and isolation media. Competitive ability of each isolate was classified as weak, moderate, or strong by determining the ratio at which it masked identification of LM82 at an inoculation concentration of 10 colony forming units (CFU)/10 mL of Listeria enrichment broth. Of the competitive isolates identified, six were Enterococcus spp., two were Staphylococcus spp., and one was a Corynebacterium sp. Although several strains of Enterococcus faecium were examined, not all were competitive. Of six other bacterial strains associated with food fermentations and tested for competitiveness with LM82, one, a Gram-positive tetrad, was competitive. This study showed that although food microfloral strains that are able to survive in enrichment and isolation environments are fairly common, they do not necessarily compete with Listeria. Not all strains in a competitive species are necessarily competitive.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-4565.1991.tb00060.x

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Microbial survey of shared-use cosmetic test kits available to the public (1994)

Tran, Tony T. ; Hitchins, Anthony D.

Springer

Journal of industrial microbiology and biotechnology 13 (1994), S. 389-391

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ISSN: 1476-5535

Keywords: Shared-use cosmetics ; Cosmetic test kits ; Microbial survey

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Summary Some people like to try cosmetics before purchasing them. With repeated use by different customers, however, the tester kits provided by many retail outlets can become potential vectors of microbial pathogens. A survey was conducted to assess the health risk from bacteria found on shared-use cosmetics. A total of 3027 shared-use cosmetic product samples were collected from 171 retail establishments throughout the contiguous United States. Eye, face and lip cosmetics were tested within situ nondestructive swabbing and the use of the Transette 3R Modified Amies Charcoal Culture and Transport System. Bacteria were isolated from about 50% of the items for all three categories. Semiquantitatively-estimated mean densities were 2288, 1685 and 1088 CFU g−1 for eye, face and lip products, respectively. Ranges for all categories were 0–155 CFU g−1. About 5% of the items had bacterial counts above 5000 CFU g−1 (eye products) or 10 000 CFU g−1 (other products). More than 60% of isolates were typical of microflora from human skin; the remainder were environmental microbes. About 60% of the isolates were Gram-positive cocci:Staphylococcus spp. (especiallyS. epidermidis) andMicrococcus spp. The Gram-negative pathogenPseudomonas aeruginosa constituted 0.07% of the isolates. The survey results suggest that the preservation systems of some of the cosmetics failed under excessive use (abuse), and indicated a potential for microbiological safety problems with shared-use consmetics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01577224

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