Pneumonia due to Branhamella catarrhalis

Pulmonary thin-section CT findings in acute Moraxella catarrhalis pulmonary infection

OBJECTIVE

Moraxella catarrhalis is an important pathogen in the exacerbation of chronic obstructive pulmonary disease. The aim of this study was to assess the clinical and pulmonary thin-section CT findings in patients with acute M. catarrhalis pulmonary infection.

METHODS

Thin-section CT scans obtained between January 2004 and March 2009 from 292 patients with acute M. catarrhalis pulmonary infection were retrospectively evaluated. Clinical and pulmonary CT findings in the patients were assessed. Patients with concurrent infection including Streptococcus pneumoniae (n = 72), Haemophilus influenzae (n = 61) or multiple pathogens were excluded from this study.

RESULTS

The study group comprised 109 patients (66 male, 43 female; age range 28-102 years; mean age 74.9 years). Among the 109 patients, 34 had community-acquired and 75 had nosocomial infections. Underlying diseases included pulmonary emphysema (n = 74), cardiovascular disease (n = 44) or malignant disease (n = 41). Abnormal findings were seen on CT scans in all patients and included ground-glass opacity (n = 99), bronchial wall thickening (n = 85) and centrilobular nodules (n = 79). These abnormalities were predominantly seen in the peripheral lung parenchyma (n = 99). Pleural effusion was found in eight patients. No patients had mediastinal and/or hilar lymph node enlargement.

CONCLUSIONS

M. catarrhalis pulmonary infection was observed in elderly patients, often in combination with pulmonary emphysema. CT manifestations of infection were mainly ground-glass opacity, bronchial wall thickening and centilobular nodules.

Moraxella catarrhalis: clinical significance, antimicrobial susceptibility and BRO beta-lactamases

Moraxella catarrhalis is an important pathogen of humans. It is a common cause of respiratory infections, particularly otitis media in children and lower respiratory tract infections in the elderly. Colonisation of the upper respiratory tract appears to be associated with infection in many cases, although this association is not well understood. Nosocomial transmission is being increasingly documented and the emergence of this organism as a cause of bacteremia is of concern. The widespread production of a beta-lactamase enzyme renders Moraxella catarrhalis resistant to the penicillins. Cephalosporins and beta-lactamase inhibitor combinations are effective for treatment of beta-lactamase producers, and the organism remains nearly universally susceptible to the macrolides, fluoroquinolones, tetracyclines and the combination of trimethoprim and sulfamethoxazole. Two major beta-lactamase forms, BRO-1 and BRO-2, have been described on the basis of their isoelectric focusing patterns. The BRO-1 enzyme is found in the majority of beta-lactamase-producing isolates and confers a higher level of resistance to strains than BRO-2. The BRO enzymes are membrane associated and their production appears to be mediated by chromosomal determinants which are transmissible by an unknown mechanism. The origin of these novel proteins is unknown.

New pathogens in pneumonia

It appears that many commonly recognized syndromes such as the ARDS may well be caused by agents that have only recently emerged as respiratory pathogens. HPS represents one such entity. It appears likely that the increasing pressure of antibiotic use as well as the reemergence of certain pathogens will continue to challenge the clinician. Paramount to the identification and treatment of unusual pneumonias will be the degree with which an effort is made to make an etiologic diagnosis through sputum examination, transtracheal aspirate, bronchoscopy, or lung biopsy. Although pneumococcal pneumonia is the most common community-acquired pneumonia seen by practicing physicians, in all likelihood from time to time a physician will encounter pneumonia caused by one of the unusual pathogens described in this article or else by an altogether new pathogen.

Life threatening Branhamella catarrhalis pneumonia in young infants

Branhamella catarrhalis is a common nasopharyngeal commensal organism but is also a recognised pathogen. Lower respiratory tract infections caused by this organism have been reported in adults but not, to our knowledge, in otherwise healthy infants. Two infants, born prematurely, suffered near fatal pneumonia. Branhamella catarrhalis was the only microbial pathogen isolated in each case. We suggest that initial antibiotic therapy for severe pneumonia in young infants should be tailored to cover B. catarrhalis infection.

Branhamella catarrhalis: an organism gaining respect as a pathogen

Branhamella catarrhalis was formerly regarded as a common, essentially harmless inhabitant of the pharynx. This misapprehension was caused, in part, by confusion with another pharyngeal resident, Neisseria cinerea. The two organisms can now be differentiated by the positive reactions of B. catarrhalis in tests for nitrate reduction and hydrolysis of tributyrin and DNase. B. catarrhalis is currently recognized as the third most frequent cause of acute otitis media and acute sinusitis in young children. It often causes acute exacerbations of chronic bronchopulmonary disease in older or immunocompromised adults and is incriminated occasionally in meningitis, endocarditis, bacteremia, conjunctivitis, keratitis, and urogenital infections. Virulence-associated factors, such as pili, capsules, outer membrane vesicles, iron acquisition proteins, histamine-synthesizing ability, resistance to the bactericidal action of normal human serum, and binding to the C1q complement component, have been identified in some strains. beta-Lactamase producing strains, first detected in 1976, have risen to approximately 75% worldwide. Thus far, however, practically all American strains of B. catarrhalis remain susceptible to alternative antibiotics. A possible selective advantage of recent isolates is their reportedly heightened tendency for adherence to oropharyngeal cells from patients with chronic bronchopulmonary disease.