The pathogenicity and persistence of Salmonella enteritidis (SE) phage type 8 and resulting egg contamination in normal and infectious bursal disease virus (IBDV)-infected white leghorn chicks were evaluated over 34 weeks and in some birds over a 64-week period. Four hundred 1-day-old specific-pathogen-free (SPF) straight-run white-leghorn chickens were allotted into four treatment groups: negative control, IBDV-infected, IBDV+SE-infected, and SE-infected. Chicks were infected with IBDV at 1 day of age and with SE phage type 8 at 2 days of age. SE persisted in the gut of more than 50% of the chicks of both SE-infected groups through 34 weeks postinoculation (PI), and SE could still be isolated from cloacal/rectal swabs taken at 64 weeks. IBDV+ SE-infected chicks had severe gross lesions and significantly (P < 0.001) higher mortality (32%) than the negative control (1%), IBDV-infected (10%), and SE-infected (1%) groups. Gross lesions consisting of fibrinous pericarditis, perihepatitis, peritonitis, airsacculitis, and inspissated yolk were observed only in the IBDV+SE-infected group. SE isolations from internal organs of chickens in the IBDV+SE-infected group decreased from 83% at 8 weeks to 0% at 14 weeks PI; isolations from the SE-infected group decreased from 50% at 8 weeks to 0% at 10 weeks PI. Salmonella isolations increased from 0% to 14% in both groups at 18 weeks, corresponding with the time of sexual maturity. Of the 1,050 eggs cultured from the IBDV+SE-infected group, SE was isolated from 88 shells, five albumens, and two yolks. In contrast, of 1,258 eggs from the SE-infected group, 33 shells and none of the albumens and yolks were positive for SE. All eggs that had SE-positive contents also had SE-positive shells.

Eighty-six Salmonella enteritidis isolates obtained during a surveillance program of poultry farms in Maine were subjected to phage-typing, plasmid profiling and fingerprinting, outer-membrane polypeptide analysis, and antimicrobial sensitivity testing. Isolates were obtained from a variety of sources, including poultry-farm environmental samples, chicken organ samples, human stool samples, cat feces, and live-trapped rats and mice. These isolates were compared with 21 S. enteritidis isolates originating outside of Maine. Phage types isolated in Maine included 13a (60%); 14b (29%); 23 (5%); 8 (2%); and 2 (2%). All S. enteritidis isolates from Maine carried plasmid DNA, and 97% of these isolates carried a 40.3-megadalton plasmid alone (6%) or in conjunction with several smaller plasmids (91%). All 52 phage-type 13a isolates harbored 40.3- and 3.0-megadalton plasmids. All 25 phage-type 14b isolates carried 3.3- and 1.3-megadalton plasmids, and 22 isolates also carried the 40.3-megadalton plasmid. All isolates displayed highly similar outer-membrane polypeptide profiles and were sensitive to a variety of antimicrobials commonly used against gram-negative organisms. The above data suggest that phage type and plasmid content may be related in the cases of phage-type 13a and 14b isolates, and that traditional plasmid-borne antimicrobial resistance determinants were not present in Maine isolates. Results also indicate that phage-typing can be a valuable epizootiological tool for monitoring the potential spread of these strains throughout the Northeast.