Background Nosocomially acquired multidrug-resistant (MDR) Gram-negative bacteria are important contributors to paediatric intensive care unit (PICU) mortality and morbidity, with limited treatment options.

Aim To investigate the outcomes of all children treated with colistin for infection with MDR Gram-negative bacteria while admitted to PICU.

Methods Retrospective observational study of 19 months. Primary endpoints were all-cause intensive care unit mortality and safety. Secondary endpoints evaluated clinical and microbiological outcomes. Cases were stratified according to HIV status.

Results Twenty-seven children received 30 colistin courses during the study period. Eight patients (29.6%) were HIV infected, six (22.2%) were HIV uninfected but exposed, and 11 (40.7%) were HIV uninfected and unexposed. Common MDR Gram-negative bacteria cultured were: Acinetobacter species (n=22, 81.5%), Pseudomonas aeruginosa (n=11, 40.7%) and Klebsiella pneumoniae (n=7, 25.9%). Mortality was 37%, with no significant difference between HIV strata. No adverse drug reactions were noted. A composite clinical improvement was noted in 16 courses (53.3%) of colistin. Only 30% of colistin courses used in HIV-infected children resulted in an improved clinical assessment as compared with 83.3% of courses in HIV-uninfected/unexposed children (p=0.04). In HIV-infected children, five of 10 (50%) courses of colistin showed bacteriological clearance compared to the HIV uninfected/unexposed group where all cases showed bacterial eradication (p=0.02).

Conclusions HIV-infected children had poorer clinical and bacteriological responses to colistin treatment than HIV uninfected/unexposed. These results require confirmation with prospective studies to determine whether findings are due to poor microbial response, immunodeficiency or repeated reinfections.