# Results from the Survey of Antibiotic Resistance (SOAR) 2018–21 in Türkiye: data based on CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints

## TL;DR

This study analyzed antibiotic resistance in bacteria from respiratory infections in Türkiye, showing varying susceptibility based on different testing methods.

## Contribution

The study provides updated antibiotic susceptibility data for S. pneumoniae and H. influenzae in Türkiye using multiple breakpoint standards.

## Key findings

- Penicillin susceptibility in S. pneumoniae was 35.9% using CLSI/EUCAST low-dose breakpoints and 82.4% using high-dose/CLSI intravenous breakpoints.
- Fluoroquinolones showed the highest activity (≥97.9%) against S. pneumoniae, while other cephalosporins and tetracyclines were less effective.
- Most H. influenzae isolates were β-lactamase negative, with high susceptibility to most antibiotics except trimethoprim/sulfamethoxazole and ampicillin.

## Abstract

To determine the antibiotic susceptibility of Streptococcus pneumoniae and Haemophilus influenzae from community-acquired respiratory tract infections from four hospitals in Türkiye in 2018–21.

MICs were determined by CLSI methodology, and susceptibility was interpreted using CLSI, EUCAST and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints.

S. pneumoniae (n = 142) and H. influenzae (n = 315) isolates were collected. Penicillin susceptibility in pneumococci was 35.9% by CLSI oral/EUCAST low-dose breakpoints and 82.4% by EUCAST high-dose/CLSI intravenous administration. Similar susceptibility (78.2%–82.4%, CLSI) was observed for ceftriaxone, amoxicillin/clavulanic acid, amoxicillin and cefotaxime. Other cephalosporins, tetracyclines, macrolides and trimethoprim/sulfamethoxazole were poorly active (42.3%–59.2%); fluoroquinolones (≥97.9%) were most active. Susceptibility by EUCAST was lower for high-dose amoxicillin (64.8%), high-dose amoxicillin/clavulanic acid (59.2%) and cefaclor (0%), but higher for high-dose ceftriaxone (99.3%). High-dose PK/PD breakpoints for amoxicillin and amoxicillin/clavulanic acid increased susceptibility (87.3% and 88.0%). Most H. influenzae were β-lactamase negative (n = 294, 93.3%); 26 (8.3%) were β-lactamase-negative ampicillin-resistant by EUCAST breakpoints and eight (2.5%) by CLSI breakpoints. Antibiotic susceptibility was ≥91.8% (CLSI) except ampicillin (85.4%) and trimethoprim/sulfamethoxazole (64.1%). EUCAST or PK/PD breakpoint susceptibility was similar, except for oral cefuroxime (0% EUCAST, 71.7% PK/PD and 99.4% CLSI) and macrolides (no EUCAST breakpoint, 1.0%–2.5% PK/PD and 96.5%–99.1% CLSI).

Susceptibility in S. pneumoniae was <60% except for fluoroquinolones, amoxicillin and amoxicillin/clavulanic acid, cefotaxime and ceftriaxone. H. influenzae susceptibility to most antibiotics was >90% except for trimethoprim/sulfamethoxazole and ampicillin. These data are similar to recent surveillance of antibiotic resistance data in Türkiye.