Abstract
OBJECTIVES: To determine the antibiotic susceptibility of Streptococcus pneumoniae and Haemophilus influenzae isolates from community-acquired respiratory tract infections (CA-RTIs) collected in 2018-21 from Pakistan. METHODS: MICs were determined by CLSI broth microdilution; susceptibility data were interpreted using CLSI, EUCAST and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints. RESULTS: S. pneumoniae (n = 57) and H. influenzae (n = 67) were collected from the Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, Pakistan. The proportion of penicillin-susceptible pneumococci was 28.1% by CLSI oral/EUCAST low-dose breakpoints; 98.3%/98.2% were susceptible by EUCAST high-dose/CLSI intravenous breakpoints. Good activity (≥93.0%) was observed using CLSI or PK/PD breakpoints for amoxicillin, amoxicillin/clavulanic acid, cefotaxime, cefpodoxime, ceftriaxone, cefuroxime, levofloxacin and moxifloxacin. Cefdinir and cefaclor were less active (75.4% and 57.9%, respectively, by CLSI and 61.4% and 19.3%, respectively, by PK/PD). Tetracyclines, macrolides and trimethoprim/sulfamethoxazole were poorly active (5.3%-36.8%). EUCAST high-dose breakpoints indicated similar activity, although susceptibility to cefaclor (0%), cefpodoxime (70.2%) and cefuroxime (68.4%) was lower than by CLSI. Most H. influenzae isolates were β-lactamase negative (95.5%). Generally, antibiotic susceptibility was >83.6% by CLSI for all antibiotics except trimethoprim/sulfamethoxazole (13.4%). Susceptibility by EUCAST was similar, except for cefuroxime (oral), with 0% susceptible isolates versus 95.5% by CLSI and 67.2% by PK/PD, fluoroquinolones and macrolides (no EUCAST breakpoint). Macrolide susceptibility by PK/PD breakpoints was low. CONCLUSIONS: Although antimicrobial resistance was observed, many therapeutic options remain to treat S. pneumoniae and H. influenzae from CA-RTI in Pakistan despite concerns about high levels of inappropriate antibiotic use. Continued surveillance of antibiotic susceptibility is important for guiding empiric therapy of CA-RTIs.