Detection of volatile sulfide-producing bacteria isolated from poultry-processing plants

Inhibitory effects of enterococci on the production of hydrogen sulfide by hydrogen sulfide-producing bacteria in raw meat

AIMS

Applying competitive exclusion micro-organisms to control hydrogen sulfide (H₂S) gas produced by hydrogen sulfide-producing bacteria (SPB) in chicken meat.

METHODS AND RESULTS

Five SPB strains, isolated from animal by-products, were used for screening lactic acid bacteria (LAB) that can inhibit the production of H₂S by SPB in trypticase soy broth supplemented with L-cysteine (TSB-L-cys). A sensitive and accurate test strip method was developed for H₂S determination in real time. One LAB strain, isolate L86, from cheese whey, demonstrated the highest inhibitory activity against the production of H₂S by SPB. The isolate L86 was confirmed as Enterococcus faecium that does not possess genes encoding for vancomycin resistance based on PCR analysis. Enterococcus faecium strain L86 reduced (P < 0·05) the yield of H₂S upto 51·2% in 10 h at 35°C in TSB-L-cys medium. In fresh chicken meat, the yield of H₂S produced by the artificially inoculated SPB was reduced (P < 0·05) by 48·6, 49·7 and 69·8% in 10 h at 35, 30 and 25°C, respectively. Enterococcus faecium strain L86 also reduced (P < 0·05) by 53·8% on the yield of H₂S produced by the indigenous SPB in partially spoiled chicken meat at 35°C for 10 h.

CONCLUSIONS

Enterococcus faecium strain L86 is effective on inhibiting the production of H₂S by SPB.

SIGNIFICANCE AND IMPACT OF THE STUDY

The application of this biological agent to raw animal by-products will provide a safer working environment in rendering processing plants and produce higher-quality rendered products.

Identification of Brevibacterium from clinical sources

Coryneform bacteria of the genus Brevibacterium occur on the normal skin surface, but reports of human infection with this genus are lacking. A number of cultures of coryneform bacteria sent to the National Collection of Type Cultures for identification have been identified as Brevibacterium spp on the basis of their cell wall composition and ability to produce methane-thiol from L-methionine. We describe a rapid method for the detection of methane-thiol and confirmatory tests which differentiate Brevibacterium from morphologically similar genera.

Volatile compounds associated with the aerobic growth of some Pseudomonas species on beef

Five strains representing four clusters of meat spoilage pseudomonads were grown on sterile beef at 5 degrees C. After 7 days incubation sensory assessments were made and the chemical composition of the headspace gases determined by gas chromatography-mass spectrometry. There was good correlation between odour descriptions and chemical data for three of the strains. The most numerous types of product were esters and sulphur-containing compounds. Of 45 compounds identified only 1-undecene was common to all the tested strains.

A critical review of the literature on hydrogen sulfide toxicity

The information available on the biological activity of hydrogen sulfide has been examined for present status of critical results pertaining to the toxicity of hydrogen sulfide. This review of the literature is intended as an evaluative report rather than an annotated bibliography of all the source material examined on hydrogen sulfide. The information was selected as it might relate to potential toxic effects of hydrogen sulfide to man and summarized, noting information gaps that may require further investigation. Several recommendations are listed for possible consideration for either toxicological research or additional short- and long-term tests. Two bibliographies have been provided to assist in locating references considered in this report: (1) literature examined but not cited and (2) reference citations. The majority of the references in the first bibliography were considered peripheral information and less appropriate for inclusion in this report.

Identification of volatile organic compounds produced by fluorescent pseudomonads on chicken breast muscle

Four different fluorescent pseudomonads were isolated from spoiled, uncooked chicken breasts and were grown in pure culture on initially sterile chicken breast muscle at 2 to 6 degrees C for 14 days. The volatile compounds produced by each culture were concentrated on a porous polymer precolumn and separated and identified by high-resolution gas chromatography-mass spectrometry.

Spoilage association of chicken skin

The bacterial succession on the skin of broiler chicken carcasses stored at 2 degrees C was traced, and the ability of representative isolates to produce off-odors was determined by using sterile leg and breast muscle sections. Off-odors were identified by olfactory and chemical means. The inability of peptone-iron agar to detect sulfide-producing strains was noted.