A Case of Urinary Tract Infection Caused by Multidrug Resistant Streptococcus mitis/oralis

S. mitis/oralis has been previously reported in isolated cases of bacterial endocarditis and liver abscesses. Its presence in urine is generally considered a contaminant. A 66-year-old male patient was admitted to the hospital due to recurrent chest tightness and four-year history of exertional dyspnea. On the second day of admission, the patient presented with urgent and frequent urination, as well as dysuria. Both initial and subsequent urine cultures showed S. mitis/oralis infection, with polymorphonuclear leukocyte phagocytosis observed in the second sample. MALDI-TOF results confirmed the isolated strain as S. mitis/oralis. Drug susceptibility testing revealed multidrug resistance to penicillin, ceftriaxone, cefepime, levofloxacin, ofloxacin, and tetracycline, but sensitivity to quinupristin/dalfopristin, vancomycin, and linezolid. The clinician then prescribed vancomycin for anti-infective treatment, which proved effective. Keywords: S. mitis/oralis, UTI, MDR, phagocytosis

Automated summary

S. mitis/oralis is a common contaminant in urine, but it can also lead to bacterial endocarditis and liver abscesses. A 66-year-old male patient was admitted to the hospital due to recurrent chest tightness and exertional dyspnea. On the second day of admission, the patient presented with urgent and frequent urination, as well as dysuria. Both initial and subsequent urine cultures showed S. mitis/oralis infection, and phagocytosis of polymorphonuclear leukocytes was observed. Drug susceptibility testing revealed multidrug resistance to several antibiotics, but sensitivity to certain antibiotics. The patient was treated with vancomycin, which was effective.