Anaerobic bacteria are infrequent pulmonary pathogens, and, even then they are, they are almost never recovered due to the need for specimens uncontaminated by the upper airway flora and failure to do adequate anaerobic bacteriology. These bacteria are relatively common in selected types of lung infections including aspiration pneumonia, lung abscess, necrotizing pneumonia and emphyema. Preferred antibiotics for these infections based on clinical experience are clindamycin and any betalactam-betalactamase inhibitor.

Anaerobic bacteria are relatively frequent pathogens in pulmonary infections that are associated with aspiration and its associated complications including aspiration pneumonitis, lung abscess, necrotizing pneumonia and empyema. These conditions have been studied since the early 1900's and substantial data with important clinical and microbiologic information are now readily available. However, the reports of these infections in the past 20 years have been sparse in number and much of the previous information relevant to this topic seems much less visible or apparent. The purpose of this report is to summarize the previous data and to celebrate the enormous contributions of Dr. Sydney Finegold to this topic.

Aspiration pneumonia occurs most commonly in patients with a predisposition to aspiration (eg, those with neurological bulbar dysfunction). There is limited evidence regarding the involvement of anaerobes in most cases of aspiration pneumonia. Most patients respond to treatment for aspiration pneumonia without specific anti-anaerobic therapy such as metronidazole. Metronidazole has adverse side effects, and widespread use where not indicated can promote carriage of multiresistant intestinal flora such as vancomycin-resistant enterococci. Use of metronidazole may be appropriate in patients with aspiration pneumonia and evidence of a lung abscess, necrotising pneumonia, putrid sputum or severe periodontal disease.

The order Actinomycetales includes phylogenetically diverse but morphologically similar aerobic and anaerobic bacteria that exhibit filamentous branching structures which fragment into bacillary or coccoid forms. The aerobic actinomyces are a large, diverse group of gram-positive bacteria including Nocardia, Gordona, Tsukamurella, Streptomyces, Rhodococcus, Streptomycetes, Mycobacteria, and Corynebacteria. The anaerobic genera of medical importance include Actinomyces, Arachnia, Rothia, and Bifidobacterium. Both Actinomyces and Nocardia cause similar clinical syndromes involving the lung, bone and joint, soft tissue, and the central nervous system. The medically important Actinomyces organisms cause infections characterized by chronic progression, abscess formation with fistulous tracts and draining sinuses. Called "great masqueraders," diagnosis of actinomycosis and nocardiosis is often delayed. Once recognized, treatment of these infections requires long courses of parenteral and oral therapy. This review will compare and contrast infections due to Actinomyces and Nocardia.

Aspiration pneumonia (AP) and primary lung abscess (PLA), are diseases following aspiration of infectious material from the oropharynx or stomach. An antibiotic therapy, also covering anaerobic pathogens, is the treatment of choice. In this study we compared moxifloxacin (MXF) and ampicillin/sulbactam (AMP/SUL) concerning efficacy and safety in the treatment of AP and PLA.Patients with pulmonary infections following aspiration were included in a prospective, open-label, randomized, multicenter trial. Sequential antibiotic therapy with MXF or AMP/SUL was administered until complete radiologic and clinical resolution.A total of 139 patients with AP and PLA were included, 96 were evaluable for efficacy (EE, 48 patients in each treatment group). The overall clinical response rates in both groups were numerically identical (66.7%). MXF and AMP/SUL were both well tolerated, even after long-term administration [median duration of treatment (range) in days MXF versus AMP/SUL: AP 11 (4-45) vs 9 (3-25), PLA 30.5 (7-158) vs 35 (6-90)].In the treatment of aspiration-associated pulmonary infections moxifloxacin appears to be clinically as effective and as safe as ampicillin/sulbactam; but, however, having the additional benefit of a more convenient (400 mg qd) treatment.

Pneumonia and primary lung abscesses may result from aspiration of infectious material from the oropharyngeal cavity and the upper respiratory tract. Most subjects suffer from an impaired mechanical or immunologic defense, for example alcoholism or dysphagia following stroke. The early course of the disease is uncharacteristic. Necrotizing pneumonia, pulmonary abscesses and the characteristic, foul-smelling, putrid discharge only occur 8-14 days after the initial aspiration event. Although common respiratory pathogens are frequently isolated from the lower airways of these patients, anaerobic bacteria play a pivotal role in cavitary lung disease following aspiration. Anaerobic coverage is therefore a requirement for an adequate antibiotic regimen, and antibacterial activity against common respiratory pathogens appears reasonable in most cases. Aminopenicillins/beta-lactamase inhibitors, newer fluoroquinolones with anaerobic activity (moxifloxacin) and clindamycin have demonstrated equal clinical efficacy in the treatment of aspiration pneumonia and primary lung abscess. Prolonged antibiotic therapy is required in cases with extensive damage of lung tissue. Since antibiotics can provide cure in 80-90% of cases, surgical procedures are limited to severe complications, such as pleural empyema. Cavitary lung disease has a broad differential diagnosis, including aspiration of sterile gastric content (Mendelson syndrome), staphylococcal pneumonia, tuberculosis, primary carcinoma of the lung, metastases and vasculitis.

Aspiration pneumonia is an important and frequent complication following aspiration of infectious material from the oropharynx or stomach. Therefore the microbiological flora generally comprises a mixed spectrum of microbes including aerobic, microaerobic and anaerobic mircoorganisms. There are a number of risk factors for aspiration such as compromised consciousness or esophageal diseases. Aspiration pneumonia presents as a subacute or chronic disease. An endoscopic inspection of the bronchial system and a bacteriological evaluation should be performed in all patients. The principal therapeutic strategy for aspiration pneumonia is an antibiotic therapy. In uncomplicated cases a treatment for 7-10 days should be sufficient, but in case of complications like necrotizing pneumonia or lung abscess a prolonged administration (14-21 days, up to weeks or months) will be necessary. Recommended antibiotic regimens include clindamycin +/- cephalosporin, ampicillin/sulbactam and moxifloxacin.

The goal of this study was to determine the pathogens of the necroses of pulmonary tissue. These debilitating diseases are usually diagnosed based on clinical and radiological findings, while the more difficult microbiological diagnosis often remains uncertain. The study involved 115 patients diagnosed with lung abscess or necrotizing pneumonia; the investigations were performed in the laboratory of the "Leon Daniello" Clinical Hospital of Pneumology, Cluj-Napoca, Romania, in the period 1999-2000. The laboratory samples (sputum, transtracheal aspiration, pleural fluid, blood samples) were studied by direct microscopy and in culture. Our results concerning the pathogens are as follows: aerobes - 20 patients (17%), mixed pathogens - 57 patients (50%). We found that the most dominant pathogens from those encountered are the anaerobes (83%), which were present either alone, or in mixed infections.

Antibacterial therapy is the most important component of the complex management of pyo-destructive forms of LRTI. Since the microbial flora is rather variable and polymorphous, antibiotics used in the treatment of LRTI should be active against both aerobic (especially gramnegative) and anaerobic pathogens. The aim of the study was to prove, on the basis of the bacteriological and clinical findings, the validity of the use of cefoperazone/sulbactam (CS), the only inhibitor-protected cephalosporin, for the monotherapy of patients with LRTI. The trial enrolled 32 patients (29 males and 3 females) with various forms of LRTI, including 22 patients with destructive pneumonia, 8 patients with acute and chronic lung abscesses and 2 patients with lung gangrene. Complications of the main disease such as empyema, bronchopleural fistula, pyopneumothorax and hemoptysis in 63.5% of the patients were recorded. To verify the microbiological diagnoses, bacteriological assay of the sputum, endobronchial secretion or the contents of the abscess and pleural cavities was performed. The main component of the complex conservative treatment was the monotherapy with CS administered intravenously in an average daily dose of 5.9+/-1.59 g divided into 2 portions. The maximum daily dose for the patients with lung gangrene was 12 g. The bacteriological efficacy was evaluated by the ESCMID (1993) criteria. The clinicoroentgenologic efficacy was estimated by regression of the main signs of LRTI. The pathogens of LRTI were isolated and identified in 87.5% of the patients. Nonsporulating anaerobic bacteria such as Prevotella spp., Bacteroidesfragilis, Fusobacterium spp., Peptococcus spp. and Peptostreptococcus spp. were isolated from 24 (75%) of them. AD the anaerobic organisms proved to be susceptible to CS (100%). As for the aerobic organisms, 85.5% of them was susceptible to CS. The clinical effect of the antibacterial therapy in 29 (90.6%) patients was registered. In 20 patients (64.5%) both clinical and roentgenologic cure was shown. The lethal outcome in 1 patient (3.1%) was stated.

Pulmonary infections due to anaerobic bacteria usually occur in children prone to aspiration. The source of the anaerobic bacteria is the oropharyngeal bacterial flora, where these organisms outnumber aerobic and facultative organisms in a 10:1 ratio. The most common lower respiratory tract infections where anaerobic bacteria are recovered mixed with aerobic organisms are aspiration pneumonia, lung abscess, and empyema. The predominant isolated anaerobic bacteria are Peptostreptococcus, Fusobacterium, pigmented Prevotella, and Porphyromonas spp. and Bacteroides fragilis group. Management of these infections includes the administration of antimicrobials effective against the anaerobic as well as the aerobic pathogens.