Population-based laboratory surveillance for tribe Proteeae isolates in a large Canadian health region

The tribe Proteeae comprises the genera Proteus, Morganella and Providencia. Few studies have specifically investigated the epidemiology of infections caused by the Proteeae, and none has been conducted in a large non-selected population. The present study was a population-based laboratory surveillance in the Calgary Health Region (population 1.2 million), Canada during 2000-2005 that aimed to define the incidence, demographical risk-factors for acquisition and antimicrobial susceptibilities of Proteeae isolates. In total, 5047 patients were identified from whom Proteeae isolates were obtained (an annual incidence of 75.9/100 000), with females and the elderly being at highest risk. Incidence rates were 64.8, 7.7 and 3.4/100,000/year for the genera Proteus, Morganella and Providencia, respectively. Overall, 85% of infections were community-onset, and the overall rate of bacteraemic disease was 2.0/100,000. Compared with other species, Proteus mirabilis occurred at a much higher frequency, especially among females, and was less likely to be isolated from hospital-onset infections or to be part of a polymicrobial infection. Among isolates from community-onset infections, Providencia spp. were less likely to be from outpatients and more likely to be from nursing home residents. There were low overall rates of resistance to ciprofloxacin (4%) and gentamicin (5%), with Prot. mirabilis generally being the most susceptible. Members of the Proteeae were isolated frequently in both the community and hospital settings, but were infrequent causes of invasive disease. The occurrence, demographical risk-factors and microbiology of Proteeae isolates varied according to the individual species.