Salmonella typhimuriumphage type 141 infections in Sheffield during 1984 and 1985: association with hens' eggs

Abstract

SUMMARYFood poisoning due toSalmonella typhimuriumphage type 141 was unusual inthe Sheffield area before 1984. The sudden increase in incidence of this phage type during 1984 and 1985, and its causative role in several small outbreaks in this period have been investigated. Epidemiological and laboratory investigations suggested that hens' eggs were the most likely source ofS. typhimuriumphage type 141.

Eggs and salmonella food-poisoning: an evaluation

“…19 As most laying flocks are uninfected, the overall frequency of infection in British eggs is likely to be much lower than 1 in 1000. A MAFF study in 1989 showed a contamination rate of about 1 in 15 000 eggs (cited by Stevens et al) and even lower rates have been estimated.…”

Persistent and transient clones of Salmonella typhimurium of phage type 141 recognized by biotyping

“…Most (74%) of the animal incidents in 1984 that were associated with strains of S. typhimurium of phage type 141 were from poultry or from liquid egg suggesting that poultry and egg products were major vehicles of human infection (Communicable Disease Surveillance Centre Report, 1986). Five outbreaks and a number of sporadic cases which occurred between 1 January 1984 and 31 July 1985 in the Sheffield area were traced to the consumption of contaminated hens' eggs (Chapman, Rhodes & Rylands, 1988).…”

“…Of the 81 cultures of S. typhimurium of phage type 141 examined, 72 were received from Mr P. A. Chapman as representatives of those isolated in the Sheffield area in 1984 and 1985. These cultures included: 10 human isolates representative of those present in the five outbreaks described by Chapman et al (1988); 3 cultures from 3 different food sources associated with one of the outbreaks; 3 from samples of liquid egg from 3 separate farms; and 56 from sporadic cases of human infection. The other 9 cultures were received fromn the Scottish Salmonella Reference Laboratory, Stobhill Hospital, Glasgow; they ha(d been isolated from diverse animal sources (cattle, dog, horse, man, poultry) in Scotland in 1986 and 1987.…”

“…This is the first demonstration of any large-scale involvement of phage-type 141 strains of the FIRN biogroup in human or animal infections in the UK. Epidemiological investigations had implicated poultry and poultry products as the likely vehicles in the human infections with type 141 strains that reappeared in England andWales in 1984 (Communicable Disease Surveillance Centre Report, 1986); this may have been because of the increased heat-resistance of phage-type 141 strains (Chapman et al 1988). It was, therefore, encouraging to obtain the additional information that all English strains from Table 1.…”

Salmonellosis and eggs.

“…Salmonella organisms in egg have been shown experimentally to survive conventional light cooking methods, especially if the eggs have previously been stored in a refrigerator. 8 There seems to be little doubt that infection by S enteritidis, type 4 in particular, albeit subclinical, is currently a problem among many broiler and layer flocks in Britain. Though a survey in 1987 showed levels of salmonella contamination of retail chilled and frozen poultry carcases of 53% and 64%, respectively (D Roberts and R J Gilbert, personal communication), it is much more difficult to quantify infection in eggs.…”