Methods: A retrospective records review and comparison of antimicrobial susceptibility data for GNB isolated at the Detroit VAMC over a 7-year period, pre- and post- FQ restriction, implemented in 2013. Susceptibility testing was performed by reference broth micro-dilution methods in a central laboratory. Antibiotic usage data were obtained from pharmacy computer records from 2011-17. Antibiotic use in inpatients was expressed as days of therapy/1000 patient-days (DOT/PD) and as number of prescriptions filled for outpatients. Data were analyzed using Pearson correlation coefficient score.
Results: In 2016-17, the most common GNB isolated in our institution were E. coli (n=303), Klebsiella pneumoniae (n=100) and P. aeruginosa (n=70). Inpatient: During 2011-12, DOT/1000 PD for CIP, LEV and MOX were 34, 10 and 5 respectively, that dropped to 14, 5 and 3 during 2014-17, post- FQ restriction initiated in 2013. Outpatient: During 2013-17, outpatient CIP and MOX prescriptions decreased from 1936 to 781 and from 478 to 86 respectively; however, prescriptions for LEV, TMP/SMX and NFT increased from 33 to 128, 680 to 1074 and 95 to 322 respectively. Overall: Resistance to CIP, LEV and MOX had increased by 8% in E. coli (14 to 22%) and by 7% in P. aeruginosa (10 to 17%) during 2015-17; FQ-R in K. pneumonia and NFT-R in E coli stayed low at 7% and 2% respectively. Also, isolates of TMP/SMX-resistant E. coli and NFT-resistant K. pneumonia increased from 20- to 27% and 40-51% respectively.
Use of FQ among outpatients was still high (781 scripts in 2017) despite a 4-year restriction, resulting in high FQ-R in E. coli and P. aeruginosa; a concomitant increase in TMP/SMX and NFT resistance was noted, attributed to a compensatory increased use of these agents during the study period (p<0.05). Reversal of resistance trends may take a few years. Antimicrobial stewardship activities need to be enhanced in both ambulatory and inpatient settings in order to achieve optimal results.
S. Krishnan Natesan,