Isolation and characterization of Streptococcus mitis from blood of child with osteomyelitis

Streptococcus mitis as a New Emerging Pathogen in Pediatric Age: Case Report and Systematic Review

Streptococcus mitis, a normal inhabitant of the oral cavity, is a member of Viridans Group Streptococci (VGS). Generally recognized as a causative agent of invasive diseases in immunocompromised patients, S. mitis is considered to have low pathogenic potential in immunocompetent individuals. We present a rare case of sinusitis complicated by meningitis and cerebral sino-venous thrombosis (CSVT) caused by S. mitis in a previously healthy 12-year-old boy with poor oral health status. With the aim of understanding the real pathogenic role of this microorganism, an extensive review of the literature about invasive diseases due to S. mitis in pediatric patients was performed. Our data define the critical role of this microorganism in invasive infections, especially in immunocompetent children and in the presence of apparently harmful conditions such as sinusitis and caries. Attention should be paid to the choice of therapy because of VGS's emerging antimicrobial resistance patterns.

Epidural abscess related to Streptococcus mitis in a 57-year-old immunocompetent patient

A 57-year-old immunocompetent male patient presented himself to our emergency department with lumbar pain for 10 days, after a lumbar torsion. He was neurologically intact, but showed signs of systemic inflammatory syndrome. A lumbar MRI found a spinal epidural abscess from L3-L4 to L5-S1 levels. The patient was operated early before occurrence of neurological deficit. The abscess cultures found a Streptococcus mitis infection. The patient made a good recovery after surgical decompression, washout with samples taken for cultures and targeted antibiotic therapy for 6 weeks.

Cytotoxic property of Streptococcus mitis strain producing two different types of cholesterol-dependent cytolysins

Streptococcus mitis strain Nm-65 secretes an atypical 5-domain-type cholesterol-dependent cytolysin (CDC) called S. mitis-derived human platelet aggregation factor (Sm-hPAF) originally described as a platelet aggregation factor. Sm-hPAF belongs to Group III CDC that recognize both membrane cholesterol and human CD59 as the receptors, and shows preferential activity towards human cells. Draft genome analyses have shown that the Nm-65 strain also harbors a gene encoding another CDC called mitilysin (MLY). This CDC belongs to Group I CDC that recognizes only membrane cholesterol as a receptor, and it is a homolog of the pneumococcal CDC, pneumolysin. The genes encoding each CDC are located about 20 kb apart on the Nm-65 genome. Analysis of the genomic locus of these CDC-encoding genes in silico showed that the gene encoding Sm-hPAF and the region including the gene encoding MLY were both inserted into a specific locus of the S. mitis genome. The results obtained using deletion mutants of the gene(s) encoding CDC in Nm-65 indicated that each CDC contributes to both hemolysis and cytotoxicity, and that MLY is the major hemolysin/cytolysin in Nm-65. The present study aimed to determine the potential pathogenicity of an S. mitis strain that produces two CDC with different receptor recognition properties and secretion modes.

Inhibitory effect of a mouth rinse formulated with chlorhexidine gluconate, ethanol, and green tea extract against major oral bacterial species

Mouth rinses are a useful supplementary tool for the prevention of oral infectious diseases. Although the antimicrobial effects of mouth rinses have been investigated, there are few studies focusing on the comparison of the effects among various oral bacterial species. In the present study, the inhibitory effect of a commercial mouth rinse, "ConCoolF," and each of its major components, chlorhexidine gluconate, ethanol, and green tea extract, on multiple species of oral bacteria were investigated. Inhibition of bacterial growth was observed in all cariogenic streptococcal species with different genera, serotypes, and strains isolated from different countries when either the complete mouth rinse or chlorhexidine gluconate were used. However, no growth inhibition was observed when the bacteria were exposed to ethanol or green tea extract. Interestingly, growth inhibition was greatly reduced in non-cariogenic streptococci compared with cariogenic streptococci. In addition, both the mouth rinse and chlorhexidine gluconate inhibited the biofilms formed by both Streptococcus mutans (S. mutans) and Porphyromonas gingivalis (P. gingivalis), among which the inhibitory effect against S. mutans was higher than that against P. gingivalis. These results suggest that a mouth rinse containing chlorhexidine gluconate, ethanol, and green tea extract, or chlorhexidine gluconate alone, exhibits antimicrobial activity against several oral bacteria species, having greater activity against pathogenic bacteria.

Acute Streptococcus mitis Sacroiliitis in a Teenager with Unclear Source of Bacteremia: A Case Report and Literature Review

Septic arthritis is an orthopedic emergency that is commonly caused by Staphylococcus aureus. Old age, diabetes mellitus, rheumatoid arthritis, prosthetic joint, and recent surgery are the main predisposing risk factors. Most cases of septic arthritis are caused by hematogenous spread of infection. Infectious sacroiliitis is a rare form of septic arthritis which is often clinically challenging to diagnose due its various and nonspecific presentations. Streptococcus mitis belongs to viridans group streptococci (VGS) bacteria, which is a component of body flora that is commonly involved in bacterial endocarditis. VGS in general and S. mitis specifically is an uncommon cause of osteoarticular infections. Here, we report a case of spontaneous Streptococcus mitis bacteremia complicated by septic sacroiliitis in a healthy teenager in the absence of infective endocarditis or a clear source of bacteremia.

Atypical presentation of thoracic spondylodiscitis caused by Streptococcus mitis

Spondylodiscitis, which is most commonly caused by Staphylococcus aureus, is an uncommon infection in adults. The diagnosis of spondylodiscitis is often delayed by its vague and non-specific presentations. As part of the normal flora in human mouth and sinuses, Streptococcus mitis is a very rare cause of spondylodiscitis. We report a case of thoracic spondylodiscitis caused by S. mitis in a patient with chronic sinusitis. The patient atypically presented with a sharp chest pain that radiated to the back and the imaging studies were initially negative. He failed outpatient pain management and the diagnosis of spondylodiscitis was confirmed by bone biopsy 6 weeks later. Treatment with antibiotics completely alleviated the pain. Increased awareness and a high index of suspicion are essential for early diagnosis of spondylodiscitis with an atypical presentation.