Penicillin Susceptibility of Viridans Group Streptococci Isolated from the Oropharynx of Patients with Hematological Malignancy

Objective: The objective of this study is to determine the susceptibility to penicillin and teicoplanin of viridans group streptococci (VGS) isolated from the oropharynx of patients with hematological malignancies and to assess the risk factors for penicillin resistance.Methods: This prospective cohort study was conducted between January 2007 and December 2008 in patients with hematological malignancies. Oropharyngeal cultures were obtained and risk factors for reduced susceptibility to penicillin of VGS were analyzed. Results: VGS were isolated from the oropharynx in 75 of 122 patients. Penicillin minimum inhibitor concentration (MIC) range was 0.047-3.0 mg/L. Thirty-two (42.7%) isolates were susceptible to penicillin. High-level penicillin resistance (MIC ≥4 mg/L) was determined in none of the isolates. However, 43 (57.3%) of the isolates had reduced susceptibility to penicillin. Teicoplanin MIC range was 0.047-0.94 mg/L. Type and duration of hematological malignancy, presence of comorbidities, previous hospitalization within a year, length of hospital stay, antibiotic use within the previous six months, immunosuppressive drugs, and smoking were not a risk factor for reduced susceptibility to penicillin. Conclusions: The determination of antibiotic susceptibility of VGS in the oropharyngeal flora has significant implications for empirical therapy of the infections in patients with hematological malignancies. It is important to design larger studies to determine a therapeutic guideline based on local data for patients with hematological malignancies.