Methods: CF respiratory culture susceptibility data were collected from 1/1/2010 through 12/31/2014 from the clinical microbiology laboratory. Antimicrobial susceptibility for CF cultures are determined exclusively via the Etest® methodology and MICs are reported for each agent. The 2014 CLSI breakpoints were retrospectively applied to the previous years. Duplicate isolates for each year were removed prior to analysis. Multidrug resistance (MDR) was defined as resistance to 3 or more antibiotic classes tested.
Results: In total, 542 unique CF respiratory cultures were obtained. PSA was the most commonly isolated organism (41 %), followed by SA (40%) and Stenotrophomonas maltophilia (8%). Incidence of PSA isolation decreased from 47% of isolates in 2010 to 38% in 2014. Overall, 36% of PSA isolates were multidrug-resistant (MDR); however, MDR-PSA incidence increased each year from 26% to 43%; and no MBL producers were detected. SA incidence was stable between 40 and 43% until 2014 when incidence decreased to 38%. Overall MDR-SA incidence was 73%. Methicillin-resistant SA accounted for 63% of all SA isolated. Methicillin-sensitive SA (MSSA) represented 27% of SA isolates. MDR-MSSA was responsible for 11% SA infections and annual incidence increased from 3% in 2010 to 15% in 2013. There were no cases of vancomycin-intermediate SA reported; however, incidence of MICs ≥ 1.5 µg/mL was 6%. Overall, MDR organism incidence increased from 39% in 2010 to 49% in 2014. Stenotrophomonas maltophilia incidence increased from 7% in 2010 to 11% in 2014. All Stenotrophomonasisolates were susceptible to minocycline, 91% were susceptible to trimethoprim/sulfamethoxazole, and only 62% of isolates were susceptible to levofloxacin.
Conclusion: MDR organisms continue to be an increasing concern in CF patients. PSA and SA occur frequently and are responsible for about 40% of isolates each.
W. C. Rutter,
D. S. Burgess, None