Abstract
BACKGROUND: Antibiotic therapy is essential for the treatment of cystic
fibrosis (CF) lung infections. CF-specific airway pathophysiology and
frequent antimicrobial exposure increase the risk of resistant
infections, creating challenges to antibiotic selection. Antibiotic
selection is generally based on previous cultures or hospital-wide
antibiograms (HWA); however, most HWA exclude CF isolates. We developed
a multi-year CF antibiogram (CFA) to compare with HWA and inform
antibiotic selection. METHODS: CF culture data were collected 2015 -
2019 at a single pediatric CF center. All sputum and oropharyngeal swab
isolates are included in the CFA. Demographics, microorganism isolates,
and susceptibility information are presented. Susceptibilities were
reported for methicillin-susceptible Staphylococcus aureus (MSSA),
methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas
aeruginosa (PA), Achromobacter species, Burkholderia species and
Stenotrophomonas maltophilia. RESULTS: Over five years, the proportion
of all SA isolates having methicillin-resistance was higher in the HWA
(32%) than the CFA (28%). The most common gram-negative CF isolate was
PA. Both gram-positive and gram-negative microorganisms were less
susceptible in the CFA versus the HWA. CF isolates from sputum were less
susceptible than oropharyngeal. MSSA and MRSA had significantly lower
clindamycin susceptibility in the CFA compared to the HWA (MSSA 71% vs
79%, p<0.0001 and MRSA 39% vs 83%, p<0.0001). For
every antimicrobial tested, PA isolates were less susceptible in the CFA
compared to the HWA. There did not appear to be significant changes in
susceptibility of CF isolates over time. CONCLUSIONS: These findings
have clinical implications for empiric antimicrobial selection. A CFA
will allow monitoring of resistance over time.