The importance of recognising Streptococcus milleri as a cause of orbital cellulitis

Update in pathological diagnosis of orbital infections and inflammations

Orbital infections and inflammations include a broad spectrum of orbital diseases that can be idiopathic, infectious, from primary or secondary inflammatory processes. Being able to properly diagnose and manage these orbital diseases in a timely manner can avoid permanent vision loss and possibly save a patient's life. When clinicians are faced with such patients, quite often the exact diagnosis cannot be made just based on clinical examination, various laboratory tests and imaging are needed. Moreover, orbital biopsies with histopathological analyses are often required, especially for the atypical cases. Thus, it is important for the clinicians to be familiar with the pathological features and characteristics of these orbital diseases. This review provides a comprehensive update on the clinical and pathological diagnosis of these orbital infections and inflammations.

Macrolide and clindamycin resistance in Streptococcus milleri group isolates from the airways of cystic fibrosis patients

Organisms belonging to the Streptococcus milleri group (SMG) are known for their role in pyogenic infections but have recently been implicated as etiological agents of pulmonary exacerbation in adult patients with cystic fibrosis (CF). The prolonged exposure of CF patients to antibiotics prompted us to investigate the susceptibility profiles of 118 SMG isolates from the airways of CF patients to 12 antibiotics compared to 43 SMG isolates from patients with invasive infections. We found that approximately 60% of all isolates failed to grow using the standard medium for disc diffusion, Mueller-Hinton blood agar (MHBA), so we explored the usefulness of brain heart infusion (BHI) agar for susceptibility testing. Zone-of-inhibition comparisons between BHI and MHBA showed strong correlations for six antibiotics, and interpretations were similar for both medium types. For ceftriaxone and cefepime, both groups of isolates were highly susceptible. Tetracycline resistance levels were comparable between the two groups (22% in CF isolates and 17.4% in invasive isolates). However, more than half of the CF isolates were not susceptible to azithromycin, erythromycin, and clindamycin, compared to 11%, 13%, and 6.5% of invasive isolates, respectively. There were 5-fold and 8-fold increased risks of azithromycin and clindamycin resistance, respectively, for the isolates from the airways of CF patients relative to the invasive isolates. Macrolide resistance was strongly linked to chronic azithromycin therapy in CF patients. This study shows that BHI agar is a suitable alternative for antimicrobial susceptibility testing for the SMG and that SMG isolates from the airways of CF patients are more resistant to macrolides and clindamycin than strains isolated from patients with invasive infections.

A polymicrobial perspective of pulmonary infections exposes an enigmatic pathogen in cystic fibrosis patients

Lung disease is the leading cause of morbidity and mortality in cystic fibrosis (CF) patients. A modest number of bacterial pathogens have been correlated with pulmonary function decline; however, microbiological and molecular evidence suggests that CF airway infection is polymicrobial. To obtain a more complete assessment of the microbial community composition and dynamics, we undertook a longitudinal study by using culture-independent and microbiological approaches. In the process, we demonstrated that within complex and dynamic communities, the Streptococcus milleri group (SMG) can establish chronic pulmonary infections and at the onset of 39% of acute pulmonary exacerbations, SMG is the numerically dominant pathogen. We report the comprehensive polymicrobial community dynamics of a CF lung infection in a clinically relevant context. If a given organism, such as Pseudomonas aeruginosa, becomes resistant to antibiotic therapy, an alternative treatment avenue may mediate the desired clinical response by effectively managing the composition of the microbial community.

Bilateral cavernous sinus thromboses and intraorbital abscesses secondary to Streptococcus milleri

PURPOSE

To report the first case of bilateral cavernous sinus thromboses and bilateral intraorbital abscesses secondary to Streptococcus milleri.

STUDY DESIGN

Single interventional case report.

INTERVENTION AND TESTING

The findings of the ophthalmic evaluation, radiographic imaging, medical and surgical intervention, specimen cultures, and clinical course were analyzed.

RESULTS

A 17-year-old female had bilateral proptosis, decreased vision in the left eye, and altered mental status at presentation. An orbital compartment syndrome developed in the left eye and purulent material was present after lateral canthotomy, suggestive of an intraorbital abscess. Magnetic resonance imaging (MRI) scans revealed bilateral cavernous sinus thromboses, and subsequent computed tomographic (CT) scans revealed bilateral intraorbital abscesses in the setting of acute ethmoid and sphenoid sinusitis. Antibiotic treatment and surgical drainage of the orbital abscess and sinuses was performed, and specimen cultures revealed S. milleri. After surgery, the patient experienced hearing loss and a right internal capsule infarct, in addition to complete vision loss in the left eye. A second intraorbital abscess developed in the right eye and was drained surgically. The vision remained 20/20.

CONCLUSIONS

Streptococcus milleri is a virulent organism with a propensity to form abscesses in multiple areas of the body and should be considered as a possible etiologic agent in abscess formation of the orbit and cavernous sinus thrombosis.