Sensitivity of Streptococcus viridans to antibacterial agents in HIV-positive patients coupled to respiratory diseases

The streptococcus group consists of multiple species of globular Gram-positive facultative anaerobic bacteria, the classification of which is based on assessing their capacity to erythrocyte hemolysis. The viridans group streptococci produce a green coloration being a part of normal microflora in the oral cavity. However, in case of developing immunodeficiency states, oncology, and neutropenia, this pathogen can cause diseases such as bacteremia, sepsis, endocarditis, as well as pneumonia in some cases. Respiratory diseases commonly require medical assistance in HIV-infected patient cohort. The role of commensal S. viridans in development of bacterial diseases in HIV-infected patients remains poorly examined. A potential association between S. viridans and other bacterial communities, including pathogenic microorganisms is obscure. In addition, it might be worth evaluating sensitivity of S. viridans to antibacterial agents in regions with high HIV infection incidence. The aim of the study was to evaluate sensitivity to antibiotics in sputum viridans group streptococci collected from HIV-infected patients with symptomatic pneumonia. Materials and methods. The data on sputum microbiological study conducted within the 01.01.2012—01.01.2019 interval were collected from all HIV-infected patients with suspected pneumonia (n = 684) and analyzed at the Infectious Clinical Hospital No. 1 named after D.M. Dalmatov, among which S. viridans was detected in 193 patients (28.2%). Bacteriological examination of patient samples was conducted to isolate pure bacterial culture by using standard methods. Next, S. viridans was assessed for sensitivity to antibacterial agents (n = 78) according to the 2018 clinical recommendations. Initially, antibiotic resistance was assessed by disk-diffusion method as a routine approach broadly used in clinical laboratory. After that, the minimal inhibitory concentration was measured by using AutoScan 4 Microscan analyzer (bacteriological semi-automatic analyzer, Beckman Coulter, USA) to identify and determine antibacterial sensitivity. Results. A disk-diffusion method allowed to find in sputum samples streptococci resistant to penicillin in 28.2% cases, ampicillin — in 42.3% and cefazolin — in 43.6%. While assessing the minimal inhibitory concentration for antibacterial agents, similar data were obtained. Good sensitivity was found for cefotaxime, ceftriaxone, cefepime, fluoroquinolones and vancomycin.