Epidemiology of non-typhoid Salmonella infection in the Australian Capital Territory over a 10-year period.

AIM

To describe the epidemiology of non-typhoid Salmonella (NTS) infection in the Australian Capital Territory (ACT), including factors associated with hospitalisation.

METHODS

This was a retrospective descriptive and observational study of culture-confirmed NTS infections using data collected from ACT public health, public pathology and hospital services in the period 2003-2012. Outcome measures include incidence and NTS serotype for total reported and hospitalised cases and focus of infection, complications and antibiotic susceptibility for hospitalised cases.

RESULTS

In total, 1469 cases of NTS infection were reported, with the crude annual incidence increasing from 24.4 to 61.3 cases per 100 000 population; 14% were hospitalised, representing an incidence of 5.9 hospitalisations per 100 000 population, without significant change over time. Hospitalisation incidence peaked at the extremes of age. Comorbid disease and age ≥ 80 years were associated with complications during hospitalisation. Salmonella serotype Typhimurium was the most common serotype, accounting for 64% of NTS. Independent risk factors for invasive disease included non-S. Typhimurium serotype (aRR 5.46, 95%CI 1.69-17.65 P = 0.005), ischaemic heart disease (aRR 4.18, 95%CI 1.20-14.60 P = 0.025) and haematological malignancy (aRR 6.93, 95%CI 2.54-18.94 P < 0.001). Among hospitalised patients, resistance to ampicillin, ceftriaxone, trimethoprim-sulfamethoxazole and quinolones was 9.9%, 0%, 4.4% and 2.5% respectively.

CONCLUSIONS

NTS notifications in the ACT have increased over time, with outbreaks of food-borne disease contributing to this increase. Crude age-specific incidence is highest in the very young, while rates of hospitalisation are highest in the elderly. Comorbid disease and infection with a non-S. Typhimurium serotype were associated with complicated NTS disease course. Antimicrobial resistance in NTS is low and has not increased over time.