Viridans Streptococci Isolated by Culture from Blood of Cancer Patients: Clinical and Microbiologic Analysis of 50 Cases

Abstract

Clinical and microbiologic studies of 50 cases of viridans streptococcal bacteremia in cancer patients were performed. The bacteria were identified to species level by sequencing analysis of the 16S rRNA gene. At least nine Streptococcus spp. were found, including S. mitis (25 strains, 50.0% of 50); currently unnamed Streptococcus spp. (11 strains); S. parasanguis (five strains); S. anginosus (three strains); S. salivarius (two strains); and one strain each of S. gordonii, S. sanguis, S. sobrinus, and S. vestibularis. There were no S. oralis strains. Among 11 antibiotics of nine classes tested, no resistance to vancomycin, linezolid, or quinupristin-dalfopristin was seen. Resistance to penicillin (MIC, 4 to 12 g/ml) was noted only among S. mitis strains (28.0%, 7/25) and not non-S. mitis strains (0/25) (P ‫؍‬ 0.004). Significantly more S. mitis strains than non-S. mitis strains were resistant to fluoroquinolones and to >3 classes of antibiotics. Isolation of quinolone-resistant organisms was associated with the prior usage of quinolones (P ‫؍‬ 0.002). Quantitative blood cultures showed that the strains resistant to levofloxacin or gatifloxacin were associated with higher colony counts than were their corresponding nonresistant strains. The young and elderly patients also had higher levels of bacteremia caused predominantly by S. mitis. Septic shock was present in 17 (34.0% of 50) patients, and 13 of those cases were caused by S. mitis (P ‫؍‬ 0.007). These results suggest that S. mitis is the most common cause of viridans streptococcal bacteremia in cancer patients and is more resistant to antibiotics than other species.Viridans streptococci represent a group of 24 currently described Streptococcus species that are nutritionally fastidious and mainly alpha-hemolytic on sheep blood agar (30). These gram-positive cocci are commensals of the oral cavity, upper airway, and gastrointestinal and genitourinary tracts. Despite the overall low virulence, they may cause infective endocarditis, contribute to polymicrobic abscess, and invade the bloodstream during the state of neutropenia.The bloodstream infection usually occurs in cancer patients with mucositis and neutropenia due to antineoplastic chemotherapy-related toxicity. In these patients, studies have found that viridans streptococci are among the most common organisms isolated from the cultures of bacteremia samples (17). As cancer care has improved and intensified over recent decades and the patients survive longer, these and other infectious complications become more pronounced. A study from our institution showed that the rate of viridans streptococcal bacteremia increased from 1 per 10,000 admissions to 47 per 10,000 during the 13-year period from 1977 to 1989 (11). These bacteremias cause substantial morbidity, and mortality in these patients is at 6 to 12% (17, 29).The most common viridans streptococci that cause neutropenic bacteremia have been S. oralis, S. mitis, and S. salivarius (4,11,15,17). Identification of these species, however, was reached through...

Streptococcus salivarius bacteremia and spontaneous bacterial peritonitis in liver transplantation candidates

“…Eight patients had underlying chronic liver disease (5 with chronic hepatitis C and 1 each with primary sclerosing cholangitis, alcoholic liver disease, and cryptogenic cirrhosis); 1 patient had fulminant hepatic failure of unknown cause. The median Child-Turcotte-Pugh score of patients with chronic liver disease was 10 (range, 6-10), and the median Model for End-Stage Liver Disease score was 17 (range, [13][14][15][16][17][18][19][20][21][22].…”

“…Han et al 17 reported that 92% of levofloxacin-resistant streptococci cases had either prophylaxis or treatment with one of the quinolones within a week of a positive culture. In another series, all isolates of VGS were susceptible to levofloxacin and moxifloxacin, and minimum inhibitory concentrations of fluoroquinolones did not differ in patients with or without norfloxacin prophylaxis.…”

“…In 1 study, 68% of the isolates were considered either contaminants or of unclear significance. 13 There are case reports of S salivarius infection involving the eyes, 14 the endocardium, 15 the bloodstream in neutropenic patients, 16,17 and the central nervous system in patients with neoplasia or iatrogenia. 18,19 There are few reports of S salivarius SBP in patients with underlying liver disease.…”

Viridans group streptococci causing spontaneous bacterial peritonitis and bacteremia in patients with end-stage liver disease

“…The emergence of levofloxacin-resistant VGS infection following prophylaxis has been reported in neutropenic patients. 3,4 In the study of Gautam et al, 1 only 1 isolate from a patient receiving norfloxacin was resistant to levofloxacin. However, primary prophylaxis is likely to be increasingly given to patients awaiting liver transplantation because it has been recently shown to improve survival.…”

Human pathogenic streptococcal proteomics and vaccine development

“…S. mutans is the main causative agent of human dental caries, one of the most common infectious diseases afflicting humans [10]. Infection by commensal and zoonotic streptococcal species occurs primarily in immunocompromised individuals and the elderly [11][12][13][14][15]. Commensal organisms colonizing the oral mucosa, the surface of teeth (organisms of the groups S. mitis, S. mutans, S. salivarius, S. anginosus) and other mucosal niches (S. anginosus group), may cause infective endocarditis and have also been associated with serious suppurative infections (Table 1) [10,[16][17][18][19].…”