Extended-spectrum beta-lactamase (ESBL) enzymes are produced by multidrug-resistant (MDR) pathogens and confer resistance to beta lactam antibiotics. Infections due to MDR organisms, particularly those ESBL producing pathogens, are of major concern worldwide and are associated with prolonged hospital stay and increased case-fatality rate. Carbapenems are the treatment of choice for severe infections however overuse of this class of antibiotics is leading Carbapenemase-producing pathogens. Variations have been observed in the prevalence of ESBL strains from different U.S. regions however it is unclear if morbidity and mortality follow a similar pattern. This study was conducted to explore the incidence of ESBL infections in the inpatient setting and factors that affect morbidity/mortality.
The National Inpatient Sample (NIS) was used to identify all hospitalizations during 2002 to 2014; all primary and secondary diagnoses were searched to identify resistant infection that utilized the ICD-9 code “V091”. All hospitalizations were stratified based on the indication of resistant infection, and comparisons were made with the chi-square test and linear regression for categorical and continuous variables, respectively. A multivariable binary logistic regression model was used to examine survival for those with ESBL infection. All analyses were conducted with SAS version 9.4; p< 0.005 was considered significant.
The analysis identified 320,888,511 hospitalizations with 17,732 identified with ESBL infection. Significant differences for those with and without an ESBL infection were found based on US region with the pertinent results as follows; Northeast: 19.95% vs. 23.30%, Midwest: 14.71% vs. 16.81%, South: 25.14% vs. 40.53%, and West: 40.20% vs. 19.35%; p< 0.001. Results indicated US region as a significant predictor of mortality for those with ESBL infection. Regions identified in Figure 1.
Notable findings from this study include a statistically significant variation in mortality risk between US regions. Comparatively lower risk of mortality as related to ESBL infection was noted in the Midwest region as compared to the West region. A greater understanding of the regional epidemiology of β-lactamases is needed to clarify why this disparity exists.