Scientific and technical factors affecting the setting of Salmonella criteria for raw poultry: a global perspective.

Concerns about foodborne salmonellosis have led many countries to introduce microbiological criteria for certain food products. If such criteria are not well-grounded in science, they could be an unjustified obstacle to trade. Raw poultry products are an important part of the global food market. Import and export ambiguities and regulatory confusion resulting from different Salmonella requirements were the impetus for convening an international group of scientific experts from 16 countries to discuss the scientific and technical issues that affect the setting of a microbiological criterion for Salmonella contamination of raw chicken. A particular concern for the group was the use of criteria implying a zero tolerance for Salmonella and suggesting complete absence of the pathogen. The notion can be interpreted differently by various stakeholders and was considered inappropriate because there is neither an effective means of eliminating Salmonella from raw poultry nor any practical method for verifying its absence. Therefore, it may be more useful at present to set food safety metrics that involve reductions in hazard levels. Such terms as "zero tolerance" or "absence of a microbe" in relation to raw poultry should be avoided unless defined and explained by international agreement. Risk assessment provides a more meaningful approach than a zero tolerance philosophy, and new metrics, such as performance objectives that are linked to human health outcomes, should be utilized throughout the food chain to help define risk and identify ways to reduce adverse effects on public health.

Combined antimicrobial resistance in Enterococcus faecium isolated from chickens.

Nineteen E. faecium strains isolated from chicken caecum samples, collected in slaughterhouses and highly resistant to vancomycin or gentamicin, were coresistant to erythromycin, and/or tetracyclines, and/or streptogramins, and/or avilamycin. Multiple antibiotic resistance was related to the presence in various combinations of aac(6')-aph(2"), erm(B), emtA, mef(A), tet(L), tet(M), and vanA genes.

Influence of a nonfavorable environment, egg white, on resistance to heat and disinfectant, adhesion, and virulence of Salmonella enteritidis.

Although liquid egg white may be subjected to limited heat treatment when it is used in the fabrication of various foodstuffs, pathogenic bacteria such Salmonella Enteritidis could persist in this environment. Liquid egg white is not a favorable medium for Salmonella growth because of its alkaline pH and iron deficiency and the presence of ovotransferrin. Microorganisms adapted to a nonfavorable environment are often more resistant to stresses than are their laboratory-cultured counterparts. The objective of this study was to determine whether Salmonella exposed to an environment mimicking egg white conditions exhibited modified behavior that could have an impact on food safety. A medium resembling egg white (filtrate of egg white with added ovotransferrin) was used as an adaptation treatment to mimic the stress imparted by the egg white environment. There were no changes in resistance to heat and disinfection, in stainless steel adhesion, or in the virulence of Salmonella Enteritidis cultivated in the egg white medium. Egg white conditions do not appear to make Salmonella more virulent or more difficult to inactivate.

Antimicrobial resistance in Campylobacter from broilers: association with production type and antimicrobial use.

The isolation and antimicrobial resistance of Campylobacter jejuni and Campylobacter coli strains from broilers arriving in French slaughterhouses, were analysed according to production types (i.e. standard, export or free-range) and antimicrobial (i.e. coccidiostats, growth promoters or therapeutic agents) administration in flocks. Prevalence was 56.6% in standard, 51.3% in export and 80.0% in free-range broilers. Three hundred and ninety-three strains were identified. Two-thirds of the strains belonged to the species C. jejuni. The others were C. coli. Antimicrobial susceptibility testing was carried out for ampicillin, nalidixic acid, enrofloxacin, tetracycline, erythromycin and gentamicin according to a dilution method. The percentages of resistant strains were, 23, 25, 17, 57, 0.3 and 0% for C. jejuni and 29, 43, 40, 70, 31 and 0% for C. coli. Statistical analysis revealed significant difference in distribution of C. jejuni and C. coli and antimicrobial resistance according to production type or antimicrobial administration.

Detection of Salmonella in fresh cheese, poultry products, and dried egg products by the ISO 6579 Salmonella culture procedure and the AOAC official method: collaborative study.

Three food types were analyzed for the presence of Salmonella by the AOAC culture method and by the International Organization for Standardization (ISO 6579:2002) culture method. Paired test portions of each food type were simultaneously analyzed by both methods. A total of 21 laboratories representing federal government agencies and private industry, in the United States and Europe, participated in this interlaboratory study. Foods were artificially contaminated with Salmonella and competing microflora if naturally contaminated sources were not available. No statistical differences (p < 0.05) were observed between the AOAC and ISO culture methods for fresh cheese and dried egg products. A statistically significant difference was observed for one of the 2 lots of poultry from the first trial. The poultry meat used in this run was radiation sterilized, artificially contaminated with Salmonella and competitive flora, and then lyophilized. A second trial was conducted with 2 separate lots of raw ground chicken that were naturally contaminated. The results from the second trial showed no statistical difference between the 2 culture methods. A third trial involving 4 laboratories was conducted on 2 separate lots of naturally contaminated raw poultry. Again, no statistically significant differences occurred. It is recommended that ISO 6579:2002 culture method for Salmonella be adopted Official First Action for the analysis of fresh cheese, fresh chilled and frozen poultry, and dried egg products.

Improvements required for the detection of Salmonella Pullorum and Gallinarum.

Detection of the specific Salmonella serovar Gallinarum, which is divided into the biovars Pullorum and Gallinarum, is compulsory under the national hygienic and sanitary control regulations of France for breeding flocks whose offspring are exported. Our aim was to examine the suitability of bacteriologic and serologic methods routinely used in France to screen serum samples and organs for S. Gallinarum. Since bacteriologic reference techniques are designed to isolate the commonly occurring non-typhoid serovars, such as S. Typhimurium, S. Enteritidis, and others that cause outbreaks of foodborne illness, they may not be particularly suitable for detecting S. Pullorum and S. Gallinarum. This hypothesis was confirmed by the inoculation of 10-wk-old chickens and 1-d-old chicks with various strains of S. Pullorum and S. Gallinarum. The most reliable enrichment media were selenite cystine and Rappaport-Vassiliadis broths. Moreover, on the usual plating media, colonies were small, grew more slowly than the common serovars (in 48 h instead of 24 h), and had an unusual appearance. Since the rapid slide agglutination (RSA) test is based only on antigens from standard and variant strains of S. Pullorum, it may not readily detect S. Gallinarum. In our study, it detected infection in all 10-wk-old chickens inoculated with S. Pullorum strains but did not detect any antibodies against S. Gallinarum. Therefore, S. Gallinarum antigens must be added to the S. Pullorum antigens used in the RSA test in order to detect antibodies produced by birds infected with either biovar.

Miniaturized Most Probable Number and Enrichment Serology Technique for the Enumeration of Salmonella spp. on Poultry Carcasses.

The ability of two 8-tube most probable number (MPN) techniques to quantitatively recover Salmonella spp. from 26 fresh, naturally contaminated chicken skin samples was compared. Individual macerated skin samples were tested in parallel using a traditional (tMPN) and a miniaturized (mMPN) analytical procedure. In the tMPN assay, replicate aqueous portions from each macerated sample were preenriched individually in buffered peptone water, selectively enriched in Müller-Kauffmann tetrathionate brilliant green broth (MKTBG), and plated on Rambach agar. Each MKTBG was also postenriched in M Broth, and the resulting postenrichment culture screened for the presence of Salmonella cells by enrichment serology (ES). Although a similar analytical approach was used in the mMPN assay, it differed from the tMPN in the use of smaller test volumes dispensed in microplates, and on a sedimented portion of skin macerate as test material. Of the 26 Salmonella -contaminated samples examined in this study, the tMPN coupled to Rambach agar or ES identified 23 and 24 positive samples, respectively. Under homologous conditions, the mMPN detected all 26 positive Salmonella contaminated samples. The most probable numbers in 100-g skin samples analyzed by the tMPN ranged from 18/100 g to 9,530,000/100 g with a median value of 570/100 g. Levels of contamination by the mMPN procedure ranged from 90/100 g to 556,000/100 g with a median value of 1,200/100 g. Statistical analysis of experimental data underlined the equivalence of the tMPN and the mMPN procedures and nonequivalence of the Rambach plating and ES conditions. It is suggested that the microplate mMPN coupled to ES offers a reliable and more cost-effective analytical approach for the quantitative recovery of Salmonella on broiler carcasses.

Recommended Assay for Treatment of Chicks to Prevent Salmonella Colonization by 'Competitive Exclusion'.

An assay is described for evaluating live-culture treatment material that may be given orally to chicks to prevent intestinal colonization by non-host-specific salmonellae. Both pre-treated and control chicks are challenged with ca 104 salmonellae/chick, using a strain bearing an antibiotic resistance marker. Chicks are examined 5 d after challenge to determine both the proportion of positive birds in treated and control groups and the levels of Salmonella in the caeca of infected individuals. The efficacy of the treatment is determined by calculation of values for Infection Factor and Protection Factor.