Association of Quarterly Antimicrobial Class Exclusion and Resistance Rates ssociation of Quarterly Antimicrobial Class Exclusion and Resistance Rates

Author(s):
Christopher Guidry; Addison May

Background:

Our Surgical Intensive Care Unit (SICU) utilizes an antimicrobial rotation protocol that includes quarterly exclusion of key antimicrobial classes.

Hypothesis:

We hypothesized that the exclusion of these classes would be associated with reduction in quarterly resistance rates.

Methods:

All isolates from culture-proven pneumonias diagnosed in the SICU from October 2013 through December 2016 were retrospectively evaluated. Resistances to beta-lactam / beta-lactamase inhibitor combinations (BLIC), fluoroquinolones (FQ), carbapenams (CARB), and 3^rd– and 4^th-generation cephalosporins (3/4 CEPH) were evaluated and recorded for each isolate. Quarterly resistance rates were evaluated based on quarterly exclusion of one of the above antimicrobial classes. BLIC’s were excluded in the first quarter, FQ’s in the second, CARB’s in the third, and 3/4 CEPH’s in the fourth quarter. Cumulative quarterly rates of resistance to each of these classes, including multi-drug resistance (MDR), were evaluated.

Results:

There were 442 isolates identified during the study period. Overall class-specific resistance rates during the study period were 9.8% for BLIC, 14.5% for FQ, 7.7% for CARB, and 10.6% for 3/4 CEPH. Quarterly resistance rates displayed below. Exclusion of BLIC’s in the first quarter was statistically associated with lower resistance rates (BLIC Q1 vs. Q2: 4.5% vs. 17.1%, p-value = 0.04 and 3/4 CEPH Q1 vs. Q2 4.5% vs. 19.5%, p-value = 0.02). The decrease in resistances in Q4 was not statistically significant. There was a statistically lower rate of CARB resistance in the quarter following its exclusion (Q3 vs. Q4: 10.3% vs. 1.4%, p-value = 0.05). There was no clear statistical association between MDR or FQ resistance by quarter.

Conclusions:

We identified a temporal relationship between exclusion of antimicrobial classes and quarterly resistance rates. Further evaluation is needed to fully evaluate the impact of excluding antimicrobial classes on overall resistance patterns.