In vitro activity of cefpodoxime against Russian clinical isolates of Haemophilus influenzae, Streptococcus pneumoniae and Streptococcus pyogenes
Authors: Kozlov R.S. , Ivanchik N.V. , Skleenova E.Yu. , Mikotina A.V. , Azizov I.S. , Trushin I.V. , Dekhnich A.V. 
Published: March 2024

Objective.
To determine in vitro activity of oral III generation cephalosporin cefpodoxime against clinical isolates of Haemophilus influenzae, Streptococcus pneumoniae and Streptococcus pyogenes isolated from patients with community-acquired respiratory tract infections in different regions of the Russian Federation.

Materials and Methods.
The study included isolates of bacterial pathogens of community-acquired respiratory tract infections isolated from outpatients and hospitalized patients in different regions of the Russian Federation. A total of 558 isolates were included in the study, including 184 isolates of H. influenzae, 186 isolates of S. pneumoniae and 188 isolates of S. pyogenes. Species identification was performed using the MALDI-TOF mass spectrometry (Bruker Daltonics, Germany), for S. pneumoniae identification was also performed taking into account the morphology of colonies on blood agar, the presence of α-hemolysis, negative catalase reaction, sensitivity to optochin and positive results of latex-agglutination using DrySpot kit (OXOID, UK). Antimicrobial susceptibility to cefpodoxime and comparative antimicrobials was determined using broth microdilution method; interpretation of susceptibility testing results was performed in accordance with the recommendations of EUCAST, v.13.0. Data analysis and visualization were performed using the online platform AMRcloud.

Results.
Despite the generally low incidence of antibiotic resistance in the tested H. influenzae isolates, cefpodoxime, to which all tested isolates were susceptible, was superior to all other oral antibiotics in terms of in vitro activity: aminophenocillins (R – 8.7%), amoxicillin/clavulanate (R – 1.1%), co-trimoxazole (R – 31.5%), levofloxacin (R – 3.8%), moxifloxacin (R – 3.8%), tetracycline (R – 11%), cefixime (R – 2.2%), ceftibuten (R – 3.3%). Among the studied S. pneumoniae isolates, 81.7% were susceptible to cefpodoxime. All isolates resistant to penicillin, amoxicillin and ceftriaxone were also resistant to cefpodoxime. Cefpodoxime was inferior to levofloxacin (R – 0%), moxifloxacin (R – 0%), linezolid (R – 0%), vancomycin (R – 0%), ertapenem (R – 8.6%), ceftaroline (R – 2.3%), and chloramphenicol (R – 3.2%) in terms of in vitro activity against S. pneumoniae. However, all these drugs are either not available in oral form or have a less favorable safety profile compared to cefpodoxime. When compared with other III generation oral cephalosporins cefixime and ceftibuten, the activity of cefpodoxime against S. pneumoniae was significantly higher based on MIC50/90 values (cefixime – 0.125⁄8 mg/l, ceftibuten – 2/≥ 128 mg/l, cefpodoxime – 0.06/4 mg/l) and MICs range (cefixime – 0.06/≥ 128 mg/l, ceftibuten – 0.06/≥ 128 mg/l, cefpodoxime – 0.03/32 mg/l). No strains resistant to β-lactam antibiotics were detected among the tested S. pyogenes isolates. Based on the MIC50/90 values and the range of MIC values, the in vitro activity of cefpodoxime was higher than that of ceftibuten and comparable to that of cefixime.

Conclusions.
According to the results of our study, as well as in view of its pharmacokinetic profile, high safety and compliance, cefpodoxime can be considered as one of the options for oral therapy of community-acquired bacterial upper and lower respiratory tract infections.