The impact of ageing on the incidence and mortality rate of bloodstream infection: A hospital-based case-cohort study in a tertiary public hospital of Brazil.

Objective: Over the past few decades, life expectancy in Brazil has increased from 48 years in 1950s to 76 years in 2017. The aim of this study was to investigate the impact of ageing on: (1) the frequency of hospitalisations due to bloodstream infection (BSI); (2) the incidence of hospital-acquired BSI (H-BSI); (3) the incidence of BSI caused by multidrug-resistant (MDR) agents and (4) the mortality rate of BSI in a public hospital.

Methods: A hospital-based case-cohort study was conducted between 1 December 2013 and 31 December 2015. The data were analysed using multivariable logistic regression.

Results: A total of 500 BSI episodes were detected, among 11,102 hospitalizations. The incidence of hospitalisations resulting from BSI was significantly higher in older than younger patients (3.7/100 vs. 2.0/100, p < 0.01). Similarly, the incidence of hospital-acquired BSI was significantly higher in older patients (2.7/100 vs. 0.9/100, p < 0.01). Klebsiella pneumoniae (15.9%), Staphylococcus aureus (14.3%), Escherichia coli (13.1%) and Acinetobacter spp. (12.1%) were the most common agents isolated. MDR agents caused 37.6% of the BSI episodes; enteric Gram-negative bacilli resistant to third- or fourth-generation cephalosporins (9.7%) and carbapenem-resistant Acinetobacter spp. (9.2%) were the most common MDR agents. The following complications were independently associated with ageing: Charlson comorbidity index (OR = 1.16; 95% CI = 1.09-1.24); BSI secondary to urinary tract infection (OR = 2.14; 95% CI = 1.29-3.55); BSI secondary to pneumonia (OR = 1.77; 95% CI = 1.07-2.93) and 30-day mortality following BSI (OR = 2.19; 95% CI = 1.43-3.36).

Conclusions: These data suggest ageing has a significant impact on hospitalisations due to BSI, H-BSI incidence and mortality from BSI in older patients attending a Brazilian public hospital. Age was not significantly associated with MDR-related BSI. These results indicate that age plays an important role in the increase in morbidities and mortality resulting from BSI in Brazil and that with the increased life expectancy observed over recent decades in Brazil, the burden of BSI will be expected to continue to increase. This dynamic needs to be better understood with additional studies.