Litter samples from 24 flocks of broilers and four flocks of broiler breeders were evaluated for Salmonella contamination, water activity (Aw), and total moisture content (MC). The drag swab (DS) monitoring system was used to collect samples to detect Salmonella contamination. Simultaneously, representative samples of the uppermost surfaces of dry (loose) litter and wet (caked) litter were collected for Aw and MC analyses. On dry litter surfaces, high Aw values (0.90-0.95) were associated with flocks Salmonella-positive using DS; low Aw values (0.79-0.84) were associated with flocks Salmonella-negative by DS; and transition Aw values (0.85-0.89) were associated with flocks having an increased risk for the presence of Salmonella. The association of high Aw values with Salmonella risk was not observed for wet (caked) litter surfaces. Observations suggest that limiting Aw in the litter base of broiler houses may create a less favorable environment for the multiplication of Salmonella and thus a more hygienic environment for broiler production.

Three flocks on 13 different broiler farms were monitored for Salmonella over three consecutive growout periods using the drag swab (DS) technique. One house was consistently negative for Salmonella contamination (7.7%); four houses were consistently positive (30.8%); and eight houses (61.5%) alternated between either a DS Salmonella-negative or -positive status. Simultaneously, numerous environmental parameters of the litter surface were measured, including water activity (Aw), ammonia, temperature, pH, moisture content (MC), ash content, and volatile solids. Analysis of these data as a corollary to either Salmonella-negative or -positive DS results revealed significant correlation coefficients for some of the parameters, especially Aw. The results suggest that there should be further exploration of remedial intervention based on control of some of the physical features of litter (e.g., controlling litter Aw and possibly MC and pH levels) in poultry houses.

A study was conducted to evaluate a new selective plating medium for isolating Salmonella using pure bacterial cultures, and poultry environmental specimens containing high numbers of competing enteric bacteria. Xylose-lysine-tergitol 4 (XLT4) agar was found to strongly inhibit Proteus, Pseudomonas, Providencia, and many other nonsalmonellae and to provide good differentiation between Salmonella and Citrobacter. The XLT4 medium significantly improved Salmonella isolation from chicken farm environmental drag-swab samples over the other selective plating media evaluated.

Drag-swab (DS) sampling, at the rate of four DS gauze pads per flock (house); modified culture procedures (novobiocin-supplemented plating media and delayed secondary selective enrichment); and Salmonella antigen-capture (SAC) technology were combined in screening one layer flock and 38 market-age broiler flocks. The results showed that low (negative) SAC sample-to-positive control (S/P) ratios were related to the negative culture recovery of Salmonella. Similarly, high (positive) S/P ratios were related to and indicative of positive culture recoveries. Extensive sampling and testing of 18 of the 39 flocks disclosed A) that five flocks with negative culture recoveries from feathers and freshly voided feces had essentially no positive DS-SAC values, and B) that 13 flocks with positive culture recoveries from feathers and/or fresh feces all had positive DS-SAC values.

A two-part study was conducted to examine the efficacy of several enrichment-broth techniques and of plating media for detecting salmonellae from poultry environmental samples. The data are reported on pooled samples collected from five poultry houses. The samples were cultured for salmonellae, using up to four different enrichment procedures and employing plating media with and without novobiocin. The primary enrichment-broth procedures were: 1) buffered peptone water preenrichment to Hajna's tetrathionate (TT) broth; and 2) direct inoculation in TT broth. The delayed secondary-enrichment procedure involved prolonged incubation at room temperature and transfer of the primary broths. The plating media consisted of: 1) xylose lysine desoxycholate agar (XLD); 2) xylose lysine desoxycholate agar containing 15 or 20 micrograms per mL of novobiocin (XLDN); 3) brilliant green sulfapyridine agar (BGSP); and 4) brillant green agar containing 20 micrograms per mL of novobiocin (BGN). Of the 94 Salmonella-positive recoveries from the enrichment broths in which complete comparisons could be made, an average of 75% were recovered from the primary enrichment broths and an average of 86% were recovered from the delayed secondary-enrichment broths. Of the 254 Salmonella-positive isolations in which complete comparisons could be made, an average of 65% were isolated on the plating media without novobiocin and an average of 97% were isolated on the plating media containing novobiocin. Overall, the delayed secondary enrichment and enteric plates supplemented with novobiocin significantly improved Salmonella detection from the farm environmental samples.