a1 Exeter Public health Laboratory, Church Lane, Heavitree, Exeter, Devon EX2 5AD,
a2 PHLS Centre for Applied Microbiology and Research, Division of Pathology, Porton Down, Salisbury, Wiltshire SP4 OJG,
a3 Hull Public Health Laboratory, Hull Royal Infirmary, Anlaby Road, Hull HU3 2JZ,
a4 PHLS Division of Enteric Pathogens, Central Public Health Laboratory, 61 Colindale Avenue, London NW9 5HT,
a5 MAFF Veterinary Investigation Centre, Riseholme, Lincoln LN2 2LJ
Two small flocks of egg-laying hens, naturally infected with Salmonella enteritidis. were housed in individual cages so that their eggs could be identified. During a longitudinal study where the contents of 1119 eggs were examined, 11 were positive for S. enteritidis. One isolate was phage type (PT) 33 the others were PT4. The production of infected eggs was clustered though intermittent. The positive eggs. which were produced by 10 of the 35 hens, were all found to contain fewer than 10 salmonellas. Some birds were also apparently carrying S. hadar PT14 as this organism was isolated from the contents of six Cracked eggs.
(Accepted July 28 1989)