The impact of penicillin resistance on the outcome of invasive Streptococcus pneumoniae infection in children

Background: Invasive infections caused by Streptococcus pneumoniae with red uced susceptibility to penicillin are increasing in prevalence in Australia . Aims: To determine the impact of reduced susceptibility of S. pneumoniae to penicillin on morbidity, mortality and treatment of invasive infection. Methods: Retrospective case note review of children with invasive S. pneumo niae infection over a 26 month period. Penicillin minimum inhibitory concen trations (MIC) were determined by E test. Primary clinical outcome measures included days to defervescence, duration of hospital stay, complication ra tes and mortality. The secondary outcome of financial cost was examined. Co mparisons between outcomes of patients with infections caused by susceptibl e and non-susceptible strains were performed with Student's t test, Pearson chi(2), Mann-Whitney U tests and multiple logistic regression. Results: Sixty-eight episodes of invasive pneumococcal disease were reviewe d: 14 isolates (21.1%) had reduced susceptibility or resistance to penicill in (PNSSP, MIC 0.125 mg/L-1.5 mg/L). Ten patients had meningitis, 21 had pn eumonia, 22 had bacteraemia with another focus and 15 had bacteraemia witho ut an obvious focus. PNSSP were more common in patients with meningitis and pneumonia. No patients died. Overall, patients with infections caused by P NSSP had significantly longer hospitalisation and longer time to defervesce nce. Complication rates were not significantly different between groups. Ou tcome differences were no longer significant when meningitis patients were excluded from the analysis. The PNSSP group received more expensive intrave nous antibiotics and their infections were significantly more costly to tre at. Conclusions: Infections with penicillin non-susceptible S. pneumoniae are a ssociated with higher morbidity than infections with penicillin susceptible strains, and treatment of these infections is more expensive, due to highe r drug costs and longer hospital stay.