Bone infections involving anaerobic bacteria.

Over 700 cases of anaerobic osteomyelitis have been reported in the literature. Nonetheless, most reviews of osteomyelitis have paid little attention to the potential role of anaerobes in bone infections. There have, as yet, been no prospective studies of osteomyelitis utlizing optimal anaerobic transport and culture techniques. In a retrospective study of osteomyelitis at Wadsworth VA Hospital from 1973--1975, 39 percent of 58 patients with osteomyelitis had an infection involving anaerobes. Anaerobes were isolated from 81 percent of 27 patients whose specimens were cultured anaerobically. Anaerobes were isolated from nine of ten samples of bone. Anaerobic bacteria were part of a mixed flora involving facultative bacteria in all but two cases. All of the patients with anaerobic infection had non-hematogenous osteomyelitis. Non-hematogenous disease comprises 80--90 percent of the osteomyelitis seen in adults. Our experience at Wadsworth VA Hospital and a review of the literature lead us to believe that anaerobes play a much larger role in osteomyelitis than has been appreciated previously. Infections of the calvarium, mastoid, mandible, maxilla and the extremities are most likely to involve anaerobes. Predisposing conditions include paranasal sinusitis, otitis media, periodontal disease, trauma, peripheral vascular disease, peripheral neuropathy and/or chronic osteomyelitis. The presence of a foul odor is a valuable clinical clue to the presence of anaerobes. Bacteroides, fusobacteria and anaerobic cocci have been reported with almost equal frequency from anaerobic bone infections. While Bacteroides fragilis is the most common anaerobe isolated in infections of other organ systems, it does not appear to be a common pathogen in anaerobic bone infections. The role of anaerobes in osteomyelitis is not yet resolved. They have been isolated in pure culture from infected bone, and under those circumstances are clearly pathogenic. Anaerobes are found more frequently as part of a mixed flora with facultative streptococci, gram-negative bacilli, and less often with S. aureus. In this setting it is unclear which organism or organisms are the primary invaders, or whether there is a synergistic mechanism of infection. The reliability of sinus drainage cultures also remains to be determined. Our retrospective study suggests that certain anaerobes isolated from sinus drainage are not present in infected bone. Cultures of bone or an abscess adjacent to bone would be expected to give more reliable data. The majority of anaerobes other than B. fragilis are susceptible to levels of penicillin achievable with parenteral administration of the antibiotic. Anaerobic pathogens should be sought in the situations noted above. We feel that parenteral penicillin should be part of the initial antibiotic regimen in patients with suspected or documented anaerobic bone infection...     

Treatment of anaerobic infections with metronidazole.

Metronidazole (Flagl), a compound widely used in man with minimal side-effects, has been used in the treatment of anaerobic infections caused by Bacteroides fragilis and other Bacteroides species. Seven patients were treated and all were restored to full health. Four of them did not respond to lincomycin or clindamycin which so far have been the drugs of choice against anaerobic infections. The reasons for the good results during metronidazole therapy such as the good penetration through the blood/brain barrier and into abscess cavities are discussed.     

Metronidazole in the treatment of anaerobic infections.

Using metronidazole in oral dosages of 1.5 to 2 g daily, we treated 13 adults who had anaerobic pleuropulmonary infections, including 11 with lung abscess, one with necrotizing pneumonia, and one with thoracic empyema. Five patients (four with lung abscess and one with necrotizing pneumonia) were cured. The lung abscesses of 5 patients did not respond. For 3 patients (one with epigastric distress who refused metronidazole, one with undrained empyema, and one who died while receiving metronidazole), therapy could not be evaluated. Side effects included leukopenia (2 patients), leukopenia and neutropenia (one), neutropenia (one), dark urine (two), bitter taste (two), and epigastric distress (one). In light of our findings, metronidazole is not uniformly effective in the treatment of anaerobic pleuropulmonary infections.     

Laboratory diagnosis of anaerobic pleuropulmonary infections

Anaerobic organisms play a major role in pleuropulmonary infections. Clinical manifestations range from simple aspiration to acute, severe, necrotizing pneumonias to chronic infections, such as lung abscess and empyema. Implicated pathogens are usually of endogenous origin. Laboratory diagnosis of anaerobic pleuropulmonary infections is based on recovering the etiological agent from clinical specimens. Appropriate specimens include pleuml fluid, transtracheal aspirates, transthoracic aspirates and fiberoptic bronchoscopic aspirates. Collection and transport of uncontaminated specimens is crucial to the recovery of the causative agents. Evaluation of a Gram's stain of clinical material provides a guide to initial therapy. Pigmented and non-pigmented Prevotella species, Fusobacterium nucleatum, Peptostreptococcus species, and Bacteriodes species are the most commonly recovered anaerobes in pleuropulmonary infections. Successful treatment of anaerobic pleuropulmonary infections requires a combination of antibiotic therapy and surgical interventions. Routine susceptibility testing of recovered isolates is rarely warranted.     

Rapid gas chromatographic diagnosis of anaerobic infections

The microbial culture for the isolation and identification of anaerobic causative organisms is very expensive with regard to material and time. By means of the gas-chromatographic proof of short-chain fatty acids in the clinical material within a short time (30-45 minutes) the tentative diagnosis of an anaerobic infection can be made. In the present paper methods and advantages of this kind of determination are described.     

Risk factors for anaerobic bloodstream infections in bone marrow transplant recipients.

The incidence of anaerobic bloodstream infections (BSI) in patients who underwent bone marrow transplantation (BMT) recently increased at our institution. A retrospective case-control study of patients undergoing BMT from January 1995 through December 1998 was performed to determine the microbiological characteristics, epidemiology, and outcome of anaerobic BSI and to identify independent risk factors for infection. Anaerobic BSI occurred in 23 patients, for a rate of 4 BSIs per 100 BMT procedures, and it accounted for 17% of all BSIs that occurred during the study period. Infection occurred at a mean (+/- standard deviation) of 7+/-4 days after BMT and 7+/-5 days after the onset of neutropenia. Fusobacterium nucleatum was the most frequently isolated pathogen (in 17 patients), followed by Leptotrichia buccalis (in 4), Clostridium septicum (in 1), and Clostridium tertium (in 1). Two case patients (9%) died. Severity of mucositis was an independent predictor of anaerobic BSI (odds ratio, 4.4; P=.01). Controlling mucositis is critical for the prevention of anaerobic BSI in this patient population.     

The clinical importance of anaerobic bacteria in wound infections after gastrointestinal surgery.

Wound cultures from 54 patients with infections after gastrointestinal surgery were examined. Cultures from wounds after surgery on the upper gastrointestinal tract grew few organisms, mainly aerobic gram-positive cocci. Culture from wounds on the lower gastrointestinal tract grew strains of bacteria, aerobic and anaerobic gram-negative rods dominating. Indirect immunofluorescence studies on acute and convalescent phase sera showed significant immune response against Bacteroides fragilis in a majority of cases. Immune response against anaerobic cocci was seldom found. Very high antibody titres against Clostridium perfringens were often found, both in patients' and control sera.     

Treatment of anaerobic pulmonary infections; carbenicillin compared to clindamycin and gentamicin.

Twenty-three patients with anaerobic infections of the lung were treated with either two antibiotics, clindamycin and gentamicin (11 patients) or with a single antibiotic, carbenicillin (12 patients). Cultures were obtained prior to therapy, either by transtracheal needle aspiration (17 patients) or thoracocentesis (six patients). Anaerobic bacteria were found in all. Fifteen patients had aerobic and facultative bacteria in addition. The anerobic isolates were peptostreptococci (12), peptococci (12), Bacteroides organisms (eight), clostridia (three), actinomycetes (two), eubacteria (one), and fusobacteria (one). Aerobes included streptococci (nine), enterococci (seven), Neisseria organisms (two), Klebsiella organisms (one), Citrobacter organisms (one), Pseudomonas organisms (one), Mycobacterium tuberculosis (two), and Nocardia (one). The two patients with pulmonary tuberculosis with anaerobic and superinfection received antituberculosis chemotherapy in addition. Therapeutic response was considered excellent in both groups. This suggests that carbenicillin may be used as a single antibiotic in the treatment of anaerobic and mixed infections of the lung.