Background
Infection is a major cause of morbidity and mortality in cancer patients. Gram-positive bacteria account for more than half of all documented bacterial infections in cancer patients, and streptococci are the most frequent pathogen among them. Rarely, group C, F, and G β-hemolytic streptococci have been shown to cause human disease. In this study, we describe the clinical characteristics and outcomes of these infections in cancer patients.
Methods
We performed a retrospective chart review of 157 patients who tested positive for group C, F, or G Streptococcus at the Moffitt Cancer Center between February 2012 and June 2018. Of those 157 patients, 79 were diagnosed as having a true Streptococcus infection. The study population was identified by positive cultures obtained from the microbiology laboratory during the same period.
Results
Of those 79 patients, 67 (85%) had solid tumor malignancies. The leading underlying diseases among these patients were gynecologic cancers (18%), head and neck squamous cell carcinoma (16%), and colorectal cancer (13%). Group G infections (23%) were significantly more common in patients with hematologic malignancies compared with group C or F streptococcal infections (4%). Other bacteria were isolated in 56 patients, the most common being Streptococcus species, Staphylococcus species including methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa. Seventy-two (92%) patients received antibiotics as soon as an infection was suspected, with the most common treatment regimen being a combination of vancomycin and a β-lactam antibiotic to treat polymicrobial infections.
Conclusions
Group C, F, and G streptococci are common pathogens in patients with an underlying malignancy, particularly solid tumor malignancies. Their usual association with other pathogens furthers the need for combinatorial therapeutic strategies to combat polymicrobial infections.
There has been increasing evidence in recent literature of the link between acquired antibodies to cytokines and manifestations of immune deficiency, for example, the emerging association between acquired interferon gamma autoantibody and susceptibility to intracellular organisms, in particular, nontuberculous mycobacterium (NTM). Although the presence of these autoantibodies does not always reflect pathology, their presence in high titers in a healthy individual in the setting of an opportunistic infection necessitates greater research with regard to their role. We report a case of refractory NTM with herpes zoster reactivation in an adult South Asian woman developing in association with acquired interferon gamma autoantibody. Consider testing for this rare adult onset immunodeficiency and similar ones in the setting of severe refractory or disseminated NTM and other opportunistic pathogens in patients without human immunodeficiency virus infection or acquired immunodeficiency syndrome.
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