Lung abscess due to Streptococcus mitis: case report and review

Pulmonary actinomycosis and polymicrobial empyema in a patient with ABPA and bronchocoele

We present a 43-year-old woman, with a history of allergic bronchopulmonary aspergillosis and a chronic bronchocoele, who was admitted to hospital with an infection of the bronchocoele, progressing to a pulmonary abscess and polymicrobial empyema, following dental extraction and regular Lactobacillus probiotic ingestion. Interval chest imaging following this procedure demonstrated worsening right upper lobe opacities and a right-sided pleural effusion. Bronchoscopies identified copious mucoid secretions and an infected bronchocoele with a right upper lobe airways impaction. Oral cavity organisms including Actinomyces odontolyticus were cultured on bronchial washings. Streptococcus mitis and Lactobacillus rhamnosus were cultured in pleural fluid. Treatment with endoscopic mucoid secretion suctioning; intercostal catheter insertion and therapeutic drainage; and antibiotic, glucocorticoid and anti-IgE therapy resulted in clinical and radiological improvement. Our case illustrates the potential pulmonary complications from oral cavity organisms following tooth extraction and probiotic use in patients with chronic lung disease associated with mucoid lesions and airways obstruction.

Abscessing Infection by Streptococcus mitis Mimicking Metastatic Lesions in a 5-Year-Old Girl With Nephroblastoma: A Case Report

Streptococcus mitis is a common pathogen causing infections in oncological patients. However, cases of abscesses caused by Streptococcus mitis in oncological patients have not been reported so far. We report on 5-year-old child with nephroblastoma and pulmonary and hepatic metastases at diagnosis who went into complete remission undergoing chemotherapy and nephrectomy, and who developed new round lesions in liver and lungs under continuous chemotherapy suggestive of new metastases. Biopsy of the lesions revealed abscesses with detection of Streptococcus mitis. The child was successfully treated with antibiotics, finished chemotherapy per protocol and has been in complete remission for 14 months. Infectious lesions involving organs of typical metastatic dissemination can easily be misdiagnosed as metastases, especially in the absence of symptoms. Histologic proof of lesions suspicious of metastases is mandatory if it leads to a change of prognosis and therapy. Streptococcus mitis can be a causative organism of pulmonary and hepatic abscesses in oncological patients.

Diverse virulent pneumophages infect Streptococcus mitis

Streptococcus mitis has emerged as one of the leading causes of bacterial endocarditis and is related to Streptococcus pneumoniae. Antibiotic resistance has also increased among strains of S. mitis and S. pneumoniae. Phages are being reinvestigated as alternatives to antibiotics for managing infections. In this study, the two virulent phages Cp-1 (Podoviridae) and Dp-1 (Siphoviridae), previously isolated from S. pneumoniae, were found to also infect S. mitis. Microbiological assays showed that both pneumophages could not only replicate in S. mitis but also produced more visible plaques on this host. However, the burst size and phage adsorption data were lower in S. mitis as compared to S. pneumoniae. A comparison of the genomes of each phage grown on both hosts produced identical nucleotide sequences, confirming that the same phages infect both bacterial species. We also discovered that the genomic sequence of podophage Cp-1 of the Félix d'Hérelle collection is different than the previously reported sequence and thus renamed SOCP.

Streptococci and Actinomyces induce antibodies which cross react with epithelial antigens in periodontitis

Perturbation of epithelial structure is a prominent but poorly understood feature of the immunopathological response to bacterial antigens which characterizes the destructive lesion of periodontitis. Western analysis of sera from 22 patients with periodontitis detected multiple antigens in extracts of epithelial cells whereas sera from 12 periodontally healthy subjects displayed only trace reaction with epithelial antigens. To investigate a possible relationship between the bacterial flora adjacent to diseased sites and the presence of antibodies reactive with epithelium, subgingival plaque samples were taken from deep periodontal pockets and cultured anaerobically. Gram positive bacteria containing antigens cross-reactive with epithelial cells were reproducibly isolated by probing membrane colony-lifts with affinity-isolated (epithelium-specific) antibodies and identified by 16S rDNA sequence homology as streptococci (S. mitis, S. constellatus and two S. intermedius strains) and Actinomyces (A. georgiae, and A. sp. oral clone). Conversely, when serum from patients with periodontitis was absorbed with the captured bacterial species the number of epithelial antigens recognized was specifically reduced. It was concluded that development of cross-reactive antibodies related to these organisms may contribute to perturbation of the epithelial attachment to the tooth and the progression of periodontitis. These autoreactive antibodies could also be a contributing factor in other diseases affecting epithelia.

Empyema thoracis and lung abscess caused by viridans streptococci

We retrospectively studied the bacteriology and clinical features of empyema thoracis and lung abscess caused by viridans streptococci in 72 patients seen from January 1984 to September 1996. A total of 76 strains of viridans streptococci were isolated, of which the most common isolates were Streptococcus constellatus (21 strains), S. intermedius (17), and S. sanguis (10). Species belonging to the S. milleri group accounted for the majority (68%) of isolates. In 38 (53%) patients these organisms were recognized as the sole pathogens. Of the 72 patients, 53 had empyema, 14 had lung abscesses, and five had both empyema and lung abscess. Forty-six (64%) patients had underlying diseases. Of these, malignancies were the most common (17 patients), followed by diabetes mellitus (12 patients) and central nervous system diseases (10 patients). Of the 48 patients who underwent chest-tube drainage, 27 (56%) received further treatments, including intrapleural streptokinase (18 cases), surgery (9), and both intrapleural streptokinase and surgery (3). Two (14%) of the patients with lung abscess alone underwent surgical treatment. Although all viridans streptococcal isolates were susceptible to penicillin, the patients in the study had a high mortality (21%). Univariate and multivariate analysis of data for patients with empyema alone (n = 53) showed a significantly increased risk of death in those with underlying malignancy (OR = 16.0, p = 0.023) and those with non-S. milleri-group isolates (OR = 3.72, p = 0.030). These data imply a strong clinical significance of viridans streptococci in the pathogenesis of empyema and lung abscess, as well as the need for species identification of viridans streptococci in patients with pleuropulmonary diseases.