2336. Resistance Mechanisms and Factors Associated With CTX-M-9 Group Extended-Spectrum β-Lactamase (ESBL)-Producing Enterobacteriaceae Infections in Children

BACKGROUND: There is an increasing incidence of extended-spectrum β-lactamase (ESBL) producing Enterobacteriaceae infections in children. However, most studies focus only on CTX-M-1 group (CTX-M-15). We sought to define the epidemiology of the CTX-M-9 group (CTX-M-9) producing Enterobacteriaceae infections in children to devise more effective treatment and prevention strategies. METHODS: A case–control study of children (0–21 y), cared for by 3 Chicago area hospitals during 2011–16, was performed. Cases were 44 children diagnosed with third-generation cephalosporin (3GC) resistant and/or carbapenem-resistant (CR) Enterobacteriaceae infections who had CTX-M-9 genes accounting for β-lactam resistance. PCR amplification, DNA sequencing, and DNA microarray analysis (Check-Points®) assessed for bla genes. MLST, rep-PCR and phylogenetic analysis were also performed. Controls were 135 children with 3GC and carbapenem susceptible Enterobacteriaceae infections matched by age range and hospital. Demographics; comorbidities; device, antibiotic, and healthcare exposures; and the impact of location of patient residence were evaluated. Race categories were white, black, Hispanic, and other. Stratified analysis and multivariable logistic regression were used to explore associations between predictors and CTX-M-9 infection. Data were analyzed in SAS 9.4. RESULTS: The median age of cases was 4.1 years. The predominant organism (39/44, 89%) was E. coli of virulent phylogroups B2 (41%) and D (59%). MLST analysis revealed that this collection of strains was polyclonal. On multivariable analysis, children with CTX-M-9 Enterobacteriaceae infections were more likely to be diagnosed in an outpatient clinic (OR 4.5), have E. coli infection (OR 7.0), and be of race “other” (OR 7.6) vs. controls. Residents of South Chicago were 6.7 times more likely to have a CTX-M-9 Enterobacteriaceae infection than controls; while residence in Northwest Chicago was associated with a 81% decreased risk. Significant differences in other demographics, comorbidities, invasive devices, antibiotic use, or recent healthcare were not found. CONCLUSION: We observed striking regional differences in occurrence of CTX-M-9 producing Enterobacteriaceae, suggesting that environmental influences and plasmid transfer may contribute to acquisition. It is worrisome that a large number of ESBL Enterobacteriaceae strains bearing CTX-M ESBLs circulate in the community among children. DISCLOSURES: All authors: No reported disclosures.