Comparison of methods for recovery and enumeration of Campylobacter from freshly processed broilers.

Most traditional Campylobacter detection and enumeration procedures are difficult and time consuming. Estimations of Campylobacter populations by the most probable number (MPN) method are especially laborious. The objective of this collaborative study, performed in duplicate in Agricultural Research Service and Food Safety Inspection Service laboratories, was to compare two MPN procedures (utilizing different selective enrichment broths and plating media) to the direct plating technique for enumeration of Campylobacter from freshly processed (postchill, postdrip) broiler chicken carcasses. Results obtained from the direct plating of carcass rinse samples on Campy-cefex agar were not significantly different (P > 0.05) from an MPN procedure employing Hunt's Campylobacter selective enrichment broth followed by recovery on modified Campylobacter charcoal differential agar. However, both of these procedures provided significantly (P < 0.05) better recovery than a second MPN procedure using Rosef's selective enrichment broth followed by plating on Mueller-Hinton blood agar with antibiotics. The direct plating method offers a more simple, less expensive, more rapid alternative to traditional MPN procedures for estimating Campylobacter populations associated with freshly processed broiler carcasses.

Intestinal colonization and organ invasion in chicks experimentally infected with Salmonella enteritidis phage type 4 and other phage types isolated from poultry in the United States.

Phage type 4 Salmonella enteritidis strains have only recently been isolated from poultry and humans in the United States, although this phage type predominates in many other countries. The present study assessed the ability of S. enteritidis isolates of various phage types found in the United States (including phage type 4) to colonize the intestinal tract and invade to reach internal organs in experimentally infected chicks. Groups of 5-day-old single-comb white leghorn chicks were inoculated with a range of oral doses of three phage type 4 isolates and three isolates of other phage types. Although some significant differences were observed between individual S. enteritidis isolates in the frequencies at which they colonized the intestinal tracts and invaded to reach the spleens of inoculated chicks, no consistent overall pattern differentiated phage type 4 isolates from isolates of other phage types.

The comparative virulence for chicks of Salmonella enteritidis phage type 4 isolates and isolates of phage types commonly found in poultry in the United States.

Phage type 4 Salmonella enteritidis has been associated with morbidity and mortality in broiler chickens in the United Kingdom. The recent isolation of this phage type from poultry in the United States has raised concerns about whether the current regulatory approach to S. enteritidis should be modified to consider phage type 4 differently from other phage types. The present study assessed and compared the virulence of phage type 4 S. enteritidis isolates, S. enteritidis isolates of other phage types, and an S. pullorum isolate in both single-comb white leghorn and white Plymouth Rock chicks. The mean incidence of severe illness or death following oral inoculation with phage type 4 S. enteritidis was significantly lower than the incidence associated with S. pullorum inoculation in both lines of chicks. Nevertheless, some individual phage type 4 S. enteritidis isolates caused severe effects at a frequency similar to that of S. pullorum in single-comb white leghorn chicks. In general, severe morbidity or mortality following infection with S. enteritidis isolates of all phage types tested occurred more often in single-comb white leghorn chicks than in white Plymouth Rock chicks. The mean frequency at which chicks were severely affected following inoculation with phage type 4 isolates was significantly higher than the mean for isolates of other phage types. However, in both lines of chicks, some significant differences in virulence were apparent within the set of phage type 4 strains tested. The observed virulence for chicks of recent U.S. poultry isolates of phage type 4 S. enteritidis was similar to that of earlier isolates from various sources, including poultry isolates from the United Kingdom.

Antibacterial properties of sodium nalidixate against avian Salmonellae in liquid and on solid media.

The in vitro inhibitory effect of sodium nalidixate (NaNA) for 206 avian salmonella cultures of varying serotypes was established in both liquid and on solid media. Salmonella cultures were much more resistant to the lethal effects of NaNA in veal infusion broth than on a solid medium such as MacConkey agar. The inhibitory effects of NaNA varied in liquid media, depending on the nutritive support afforded by the medium. Growth-suppressive effects were enhanced by less nutritive media. Reasons are suggested as to the possible differences in the inhibitory effect of NaNA on avian salmonella cultures grown in liquid and on solid media.

Survival of Salmonella typhimurium in poultry feed and litter at three temperatures.

Poultry feed and litter were contaminated with a large number of Salmonella typhimurium cells and then stored at 11, 25, or 38 C. Samples of feed and litter were cultured at daily or weekly intervals. The organisms survived best at the two lower temperatures. Persistence was as follows: at 11 C, at least 18 months in both feed and litter; at 25 C, 16 months in feed and 18 months in litter; and at 38 C, about 40 days in feed and only 13 days in litter. Hence, samples of feed and litter collected for bacteriologic examination should be stored at low temperatures.