Salmonellosis in North Thames (East), UK: associated risk factors

We assessed the rate of salmonella infections and risk factors associated w ith infection in North East Thames in 1993. Cases of culture confirmed infe ction were identified through microbiology laboratories and environmental h ealth officers in the North East Thames. A total of 1730 cases were reporte d and 209 of these individuals (those who could be contacted within a 3-wee k interval after onset of symptoms) and matched controls were interviewed b y telephone. In addition randomly selected controls were interviewed over a 4-month period about recent gastric acid lowering medication and antimicro bial ingestion. Sixty-six serotypes were identified: S. enteritidis was iso lated from 1179 (69 %) cases, S. typhimurium from 221 (13 %), S. virchow fr om 77 (4 %) and S. newport 25 (1 %). Infections were more frequent in summe r months. Highest rates were documented in children under 2 years of age fo r S. enteritidis (108/100000) and under 1 year for S. typhimurium (36/10000 0). Using the Townsend score, highest isolation rates of S. enteritidis wer e in more prosperous areas (36/100000 vs. 27/100000; odds ratio (OR) 1.3, 9 5% confidence intervals (CIs) 1.2-1.6, P < 0.0001), while for S. typhimuriu m, there was no relation between deprivation index and isolation rates area s (6.4/100000 vs. 6.1/100000; OR 1.1, 95 % CIs 0.8-1.5, P = 0.77). The case control study showed a significant association between ingestion of produc ts containing raw eggs and S. enteritidis infection (8/111 cases vs. 0/110 controls; OR undefined, lower 95% CIs 3.4). Individuals with salmonella inf ection were significantly more likely to have travelled abroad in the week before the onset of illness [42/186 (23 %) vs. 1/182 (0.5 %); OR 40, 95 % C Is = 5.5-291, P < 0.001] and to report gastroduodenal disease [11/143 (7 %) vs. 3/143 (2 %); OR 5.0, 95% CIs = 1.1-23, P = 0.04]. There was an associa tion between illness and gastric acid-lowering medications [unmatched contr ols OR 22.3 (95% CIs 1.5-3.7, P = 0.0002), matched controls OR 3.7 (95 % CI s 1.0-3.8, P = 0.07)], but no association with antimicrobial ingestion.