856. Invasive Haemophilus influenzae Disease in Children: A Canadian MultiCenter Study on Emerging Serotypes

BACKGROUND: Our objective was to describe the serotype distribution and clinical spectrum of invasive Haemophilus influenza (Hi) disease in children admitted to participating centers within the Paediatric Investigator’s Collaborative Network on Infections in Canada (PICNIC). METHODS: All cases of Hi bacteremia were identified from the PICNIC Database of Gram-negative bacteremia (2013–2017). Disease was defined as complicated if the following occurred: (a) >2 sites were affected, (b) surgical intervention was required, (c) organ failure, (d) ICU admission, (e) seizures, (f) sensory or motor deficits, (g) treatment-related complications, or (h) death. RESULTS: There were 98 cases of Hi bacteremia. Male to female ratio was 64:34 and median age was 12 (IQR: 7–48; range 0–216) months. Hi serotypes included: a (N = 31; 32%), b (N = 9; 9%), f (N = 15; 13%), c (N = 1;1%), e (N = 1; 1%), nontypeable (N = 34; 35%) and unknown (N = 7; 7%). Clinical foci included: bacteremia without a focus (N = 19; 19%), meningitis (N = 29; 30%), cellulitis (N = 8; 8%), septic arthritis (N = 6; 6%), pneumonia (n = 33; 34%), epiglottitis (N = 1; 1%), and endovascular infection (n = 3; 3%). Complicated disease occurred in 29 (30%) cases; there was one (1%) death. Where serotyping was available, complication rates were: 42%, 22%, 100%, 0%, 33%, and 21% for Hia, Hib, Hic, Hie, Hif and nontypeable Hi, respectively. Factors associated with complicated disease were: age <5 years (P = 0.009), bacteremia without a focus (P = 0.006) and a CNS focus (P < 0.001). Hia was the leading serotype in meningitis (55%; P = 0.022). Nontypeable Hi was most frequent in pneumonia cases (56%; P = 0.003) and never caused cellulitis (0% vs. 14%; P = 0.023). Neonatal disease (N = 5) was predominantly caused by nontypeable Hi (80%; P = 0.040). Of note, 26 (27%) of our Hi isolates were ampicillin resistant. CONCLUSION: In the era of efficacious conjugate Hib vaccines, serotype has emerged as the leading cause of typeable Hi disease in Canada and is highly associated with meningitis, especially in young children. Strategies for preventing Hi disease need to target this emerging serotype and efforts should be focused toward developing an effective vaccine for serotype a disease. DISCLOSURES: All Authors: No reported Disclosures.