Abstract
OBJECTIVES: To determine the antibiotic susceptibility of community-acquired respiratory tract infection (CA-RTI) isolates of Streptococcus pneumoniae and Haemophilus influenzae collected in 2018-21 from two hospitals in Tunisia. METHODS: MICs were determined by CLSI broth microdilution, and susceptibility data were interpreted using CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints. RESULTS: S. pneumoniae (n = 58) and H. influenzae (n = 71) isolates were collected; 22.4% of pneumococci were penicillin-susceptible by CLSI oral/EUCAST low-dose breakpoints, but 89.7% were susceptible by EUCAST high-dose/CLSI intravenous administration breakpoints. Susceptibility to ceftriaxone, levofloxacin and moxifloxacin was ≥91.4% by CLSI or PK/PD breakpoints which reduced to 82.8%-87.9% for amoxicillin, amoxicillin/clavulanic acid and cefotaxime. Tetracyclines, macrolides and trimethoprim/sulfamethoxazole were 41.4%-65.5% susceptible, with cefdinir and second-generation cephalosporins less active (24.1%-51.7% susceptible). EUCAST indicated ≥96.6% susceptibility only to high-dose ceftriaxone, moxifloxacin and high-dose levofloxacin. Most H. influenzae (66.2%) were β-lactamase negative, of which six and two isolates were ampicillin-resistant following EUCAST and CLSI criteria, respectively. Antibiotic susceptibility was ≥91.5% (CLSI) except for ampicillin (60.6%) and trimethoprim/sulfamethoxazole (77.5%). Susceptibility by EUCAST was lower than CLSI for most other antimicrobials, except for high dose amoxicillin/clavulanic acid (93.0% by EUCAST, 97.2% high dose PK/PD). Both CLSI and EUCAST showed 100% susceptibility to ceftriaxone. CONCLUSIONS: Few therapeutic options with ≥90% susceptibility for the treatment of S. pneumoniae from CA-RTIs in Tunisia remain. Although H. influenzae isolates displayed higher susceptibility, only ceftriaxone provides 100% coverage for both species following CLSI and EUCAST guidelines. Continued surveillance is important for guiding empiric therapy.