Bacterial interference by oropharynegeal and clinical isolates of anaerobic bacteria.

Anaerobic isolates were tested for bacterial inhibitory activity. Of 144 isolates, 102 were from oropharynegeal washings, and 42 were from clinical specimens. Thirteen facultative bacterial species (seven members of the Enterobacteriaceae and six species of gram-positive cocci) were used as indicators of inhibition. Eleven anaerobic species were isolated from oral secretions. All isolates of Bacteroides melaninogenicus, the most commonly recovered species, consistently inhibited several species of indicator bacteria. Bacteroides fragilis, Bacteroides oralis, and Peptostreptococcus anaerobius had unprecictable inhibitory activity, whereas most of the other oral anaerobes were noninhibitory. The 42 clinical species were generally noninhibitory.     

Septic arthritis caused by Bacteroides fragilis

As improvements in bacteriologic techniques have enhanced the recovery of anaerobic bacteria from clinical specimens, there has been an increasing awareness of the role of anaerobes in disease. Bacteroides fragilis is the most common anaerobic organism found in clinical specimens. Although it is the anaerobe most frequently associated with bacteremia and a common isolate in intraabdominal infections, infections of the female genital tract, wounds, and abscesses, B. fragilis is a rare cause of septic arthritis. The isolation of this organism from four patients with septic arthritis in three Cleveland hospitals between 1978 and 1982 suggests that septic arthritis due to B. fragilis may be a more common clinical entity than previously appreciated. In this report we describe these cases and review the pertinent literature.     

Microbiologic profile of intra-abdominal infections at Belo Horizonte,Brazil

Intra-abdominal infections (IAIs) represent one of the most common clinical problems in hospital practice, especially in surgical areas and centers of intensive care. The treatment of IAIs generally involves the draining of abscesses and empirical antimicrobial therapy. In this study, among 150 patients suffering from IAI, 106 (70.7%) yielded samples that presented microbial growth. Polyinfection was detected in 51.9% of the cases and varied from 2 to 9 distinct microbes per specimen. The overall mean number of micro-organisms isolated per patient was 2.17. Aerobic bacteria (as strict aerobes and facultative anaerobes), strict anaerobic bacteria, and fungi of the genus Candida represented 93.4%, 30.2%, and 13.2% of the cases positive for micro-organisms, respectively. The most common aerobic bacteria were those of the genera Staphylococcus, Escherichia, Proteus, and Streptococcus. Despite the frequent prior use (52%) with antimicrobials of recognized action against strict anaerobes, these micro-organisms constituted 30.9% of the total isolates, and the most frequently found were of the Bacteroides fragilis group and Prevotella species. The high prevalence of anaerobes in the specimens obtained from IAI demonstrates the need to give greater importance to these micro-organisms by making available material and human resources to carry out culture of the anaerobes as part of routine hospital procedures.     

Bacterial colonization, tracheobronchitis, and pneumonia following tracheostomy and long-term intubation in pediatric patients.

Serial tracheal cultures for aerobic and anaerobic bacteria were obtained from 27 pediatric patients during one year of follow-up. The patients had required tracheostomy and prolonged intubation for periods ranging from 3 to 12 months (average, 7 1/2 months). Cultures of tracheal aspirates yielded 1,508 isolates of pathogenic aerobic (969 isolates) and anaerobic (539 isolates) bacteria. The most frequent aerobic isolates were Streptococcus pneumoniae and Staphylococcus aureus. The predominant anaerobes were anaerobic gram-positive cocci, Fusobacterium nucleatum, and Bacteroides fragilis. Replacement of one pathogen by another occurred frequently. Tracheobronchitis occurred in 24 patients, all of whom had episodes of pneumonia. The data suggest that anaerobic bacteria are a part of the bacterial flora in colonization, tracheobronchitis, and pneumonia in patients with tracheostomy and prolonged intubation.     

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...     

Acute appendicitis and Bacteroides fragilis.

Bacteria belonging to the Bacteroides fragilis group (B. fragilis, B. ovatus, B. vulgatus, B. distasonis, B. thetaiotaomicron and B. uniformis) were cultured in quantities of less than or equal to 10(5) c.f.u./ml from the excised appendix from 30 patients. Twenty-two patients (group I) had an acute purulent appendicitis (three with perforation), four were classified as slightly inflamed cases (group 2) and four had a normal appendix (group 3). The B. fragilis group of bacteria dominated among the anaerobic isolates, but Bifidobacteria, Fusobacteri, Clostridium perfringens, Lactobacilli, Leptotrichia and Veillonella, in decreasing order, were isolated as well. Among isolates of aerobic bacteria, E. coli was most frequently isolated (26/30 patients). No other genus was isolated from more than four of the appendices. Serological investigations of the humoral antibody response to polysaccharide antigens from four of the Bacteroides species showed that a doubling of the titer, or more, in paired serum samples could be observed as follows: against B. fragilis 6/22 patients (group 1), 3/8 patients (groups 2 and 3). The corresponding figures for B. ovatus were 11/22 and 2/8, B. vulgatus 3/22 and 0/8 and B. distasonis 4/22 and 0/8. Sera from two patients with ruptured appendix, and B. fragilis cultivated, showed the highest titer increases against the B. fragilis antigen. The data from the bacteriological and immunological investigations make us conclude that (i) the B. fragilis group of bacteria is the most common anaerobic group of bacteria isolated from normal and diseased appendices, (ii) the mere isolation of B. fragilis, encapsulated or not, does not imply an etiological role in appendicitis since there was no obvious difference in titer increases against B. fragilis in sera from patients with or without an inflamed appendix, and (iii) high, and significant, titer increases against B. fragilis are seen in sera from patients with ruptured appendix.     

The bacteriology of aspiration pneumonia

A prospective study of 54 cases of pulmonary infection following aspiration was performed. Specimens utilized for bacteriologic study were either transtracheal aspirates, empyema fluid or blood. Appropriate anaerobic bacteriologie methods were employed. Anaerobic bacteria were recovered in 50 patients (93 per cent) and were the only pathogens in 25 (46 per cent). The predominant species were Bacteroides melanino-genicus, Fusobacterium nucleatum and anaerobic or microaerophilic gram-positive cocci. Bacteroides fragilis, which is resistant to many commonly used antibiotics, was recovered in nine patients (17 per cent). Aerobic and facultative bacteria were present in 29 patients (54 per cent), but anaerobes were present concurrently in all but 4. Enteric gram-negative bacilli and pseudomonads were particularly common in patients whose disease developed in the hospital. Eleven patients with mixed aerobic and anaerobic infections were treated successfully with antibiotics which were active only against the anaerobic isolates, thereby further implicating the pathogenic role of these microorganisms. The results indicate that anaerobes play a key role in most cases of infection following aspiration.     

Endocarditis due to anaerobic bacteria

This review describes the microbiology, diagnosis and management of endocarditis due to anaerobic bacteria. Anaerobic bacteria are an uncommon but important cause of endocarditis. Most cases of anaerobic endocarditis are caused by anaerobic cocci, Propionibacterium acnes and Bacteroides fragilis group. Predisposing factors and signs and symptoms of endocarditis caused by anaerobic bacteria are similar to those seen in endocarditis with facultative anaerobic bacteria with the following exceptions: the gastrointestinal tract was the most common source for B. fragilis group endocarditis, the head and neck were the most common origin for Fusobacterium and Bacteroides spp., and the head and neck and genitourinary tract were the most common source for peptostreptococci. Complications with anaerobic endocarditis include valvular destruction, multiple mycotic aneurysms, aortic-ring abscess, aortitis, cardiogenic shock, dysrhythmias and septic shock. The mortality rate for patients with anaerobes endocarditis is 21-43%. Treatment of endocarditis involving anaerobic bacteria includes the use of antibiotic therapy effective against these organisms.     

Pericarditis due to anaerobic bacteria

This review describes the microbiology, diagnosis and management of pericarditis due to anaerobic bacteria. The predominant anaerobes recovered from patients with pericarditis were: gram-negative bacilli (mostly of the Bacteroides fragilis group), anaerobic streptococci, Clostridium spp., Fusobacterium spp., and Bifidobacterium spp. Anaerobic bacteria can be isolated in pericarditis resulting from the following mechanisms: (1) spread from a contiguous focus of infection, either de novo or after surgery or trauma (pleuropulmonary, esophageal fistula or perforation, and odontogenic); (2) spread from a focus of infection within the heart, most commonly from endocarditis; (3) hematogenous infection, and (4) direct inoculation as a result of a penetrating injury or cardiothoracic surgery. No differences were found in the clinical diagnostic features between cases of pericarditis due to anaerobic bacteria and those due to aerobic and facultative bacteria. Anaerobic gram-negative bacilli have increased their resistance to penicillins and other antimicrobials in the last decade. Complete identification and testing for antimicrobial susceptibility and lactamase production are therefore essential for the management of infections caused by these bacteria. Treatment of pericarditis involving anaerobic bacteria includes the use of antibiotic therapy effective against these organisms.     

Susceptibility of isolates of Bacteroides to the bactericidal activity of normal human serum.

Seventy-one strains of species from the Bacteroides fragilis group, including 46 isolates of B. fragilis, were tested for susceptibility to the bactericidal effect of serum from healthy subjects. Twenty-seven (38%) of the isolates were killed by serum. Isolates from feces were significantly more sensitive to serum than were isolates from patients with clinical infections. Killing of bacteria required heat-labile serum components and was an exponential function of serum concentration. Among the various species tested, B. fragilis was clearly the most resistant to bactericidal activity of serum. These observations may be important to the understanding of infections caused by the B. fragilis group, which contains the anaerobes of greatest clinical importance.     

Susceptibility of the liver and biliary tract to anaerobic infection in extrahepatic biliary tract obstruction. Bacteriological investigations - an experimental study in rabbits.

The influence of common duct occlusion on susceptibility to infection with anaerobic gram-negative rods was investigated in rabbits. Intravenous inoculation was performed with three B. fragilis strains isolated from human infections and with a stock culture of Fusobacterium mortiferum. Liver tissue, gallbladder, bile, and blood were investigated. Anaerobic culture procedures were based on the use of a 'glove-box' with an oxygen-free atmosphere and pre-reduced, anaerobically sterilized media. Anaerobic transport was based on flushing of samples with oxygen-free carbon dioxide and transport-time less than 30 minutes. In regard to two B. fragilis strains (ss. fragilis) and in regard to Fusobacterium mortiferum, common duct occlusion significantly increased the number of infected animals compared to a control group of inoculated animals without common duct occlusion. Spontaneous infection did not arise in a control group of animals with common duct ligation. It is concluded that: 1) in biliary tract occlusion, anaerobic bacteria are able to invade the biliary tract from the blood stream, and 2) biliary tract occlusion produces sufficient anaerobic conditions for obligate anaerobic bacteria to multiply in the bile.     

Anaerobic infection of the liver and biliary tract in experimental common duct occlusion.

The pathogenicity of single anaerobic, single aerobic, and mixed anaerobic and aerobic bacterial inocula was studied in 3 groups of 12 rabbits with biliary tract obstruction. B. fragilis, ss. fragilis and E. coli serotype 01:K1:H7 were used. The investigation was made 7 days after bacterial inoculation and included bacteriological studies of the liver and bile as well as studies of liver function and morphology of the liver and biliary tract. Inoculation of 10(5)--10(6) E. coli did not cause biliary tract infection, liver abscesses or death. Inoculation of 10(9) B. fragilis caused biliary tract infection in 83 per cent and liver abscesses in 17 per cent of the animals inoculated, without any mortality. Combined inoculation with B. fragilis and E. coli in reduced doses significantly increased mortality (42 per cent) and frequency of liver abscesses in surviving animals (86 per cent). All abscesses, however, yielded pure culture of B. fragilis only. 84 per cent of the animals inoculated with B. fragilis alone or with B. fragilis in combination with E. coli developed biliary tract infection with B. fragilis, the bile yielding from 10(7)--)0(9) B. fragilis per ml, gall bladder bile yielding significantly higher bacterial counts than common duct bile. E. coli was never recovered from bile in surviving animals but from both bile and blood in animals not surviving the experimental period.     

Retrospective analysis of Fusobacterium associated infections; experience at Aomori Prefectural Hospital with 108 cases from 1995 to 1999

We experienced 108 cases of Fusobacterium associated infections, including otolaryngeal, oral, pleuropulmonary, intraabdominal, skin and soft tissue infections, at Aomori Prefectural Hospital during The 5 year-period from 1995 to 1999. A total of 433 organisms, included 113 Fusobacterium spp. (80 Fusobacterium nucleatum, 18 Fusobaterium necrophorum, 5 Fusobacterium varium, 4 Fusobacterium mortiferum, 6 Fusobacterium spp.), were recovered with an average of 4.0 organisms per case of the 108 cases, 68% were mixed aerobic and anaerobic and yielded 185 anaerobic bacteria (2.5 per case) and 137 aerobic bacteria (1.9 per case) with an average of 4.4 per case. The remaining 32% were purely anaerobic and yielded 111 organisms with an average of 3.2 per case, Prevotella spp., Bacteroides fragilis group, Streptococcus milleri group, Enterobacteriaceae, Peptostreptococcus spp. Staphylococcus spp. were most frequently coisolated with Fusobacterium spp.     

Characteristics of brain abscess with isolation of anaerobic bacteria

In view of its localization, brain abscess (BA) usually requires medical and surgical care. A broad spectrum of bacteria is involved. Recent reports stress the increasing frequency of anaerobes, but their impact has not been well evaluated. A retrospective review was conducted of all episodes of documented BA admitted in a tertiary-care hospital over a 10 y period. BA due to anaerobic bacteria (group A) were compared with other cases (group B) to determine the frequency and eventual characteristics of BA with isolated anaerobic bacteria. Between 1991 and 2000, BA were diagnosed in 42 patients (28M, 14F, mean age 54.6 y). No differences in clinical features and laboratory findings were found between patients with BA caused by anaerobic (n = 22) and only aerobic (n = 20) bacteria. Using appropriate microbiological techniques, 41 anaerobic bacteria strains were isolated in 22 of 42 patients (52.4%) with BA. Anaerobic bacteria were associated with aerobic strains in 5 patients (12%), whereas in 17 patients (40.5%) only anaerobic strains were isolated in cerebral puncture cultures. The most frequently isolated species were Fusobacterium nucleatum (n = 14), Prevotella sp. (n = 8), Actinomyces sp. (n = 6) and Bacteroides sp. (n = 4). Compared with group B, group A had more cases of a single abscess (p = 0.03) and ear, nose and throat (ENT) as a source of infection (p = 0.04), and seemed to have a better outcome (p = 0.07). These results emphasize the important role that anaerobic bacteria play in BA. The presence of such pathogens must be evoked when faced with a single abscess, an ENT infection, or both. Therapy should take into account this high frequency.     

Gastric microflora in patients receiving H2-blocker

The gastric microflora of 21 cases receiving histamine H2-receptor antagonists (H2-blocker) were studied. Patients not given H2-blocker were also examined for gastric microflora. The gastric pH of patients who were receiving H2-blocker ranged from 1.91 to 6.51 (mean, 4.32). The gastric pH of over 5.00 was seen in 10 cases. Aerobic bacteria were isolated from 20 cases (95%). Aerobic bacterial counts per ml of gastric aspirates correlated positively with the pH of those aspirates but was little correlation between the pH of the gastric aspirates and the number of anaerobic bacteria of the samples, which were positive in 7 cases (33%). Candida and Staphylococcus were predominant isolates with positive rates of 82% and 41%, respectively. While Fusobacterium was isolated from 33% of the samples, none of the Bacteroides fragilis group organisms were isolated. It was also observed in the control group that aerobic and anaerobic bacteria were isolated from the gastric aspirates with high pH. These results suggest that in patients receiving H2-blocker anaerobes as well as aerobes may have the possibility to become pathogen for aspirate pneumonia and so on because of the overgrowth of anaerobic bacteria in the gastric fluid.     

Anaerobic pulmonary infections.

The main cause of anaerobic pulmonary infections is aspiration of saliva, upper airway secretions or gastric content. Predisposing conditions include prominent dental disease, chronic upper respiratory tract infections and reduced consciousness. Fusobacterium nucleatum, Bacteroides melaninogenicus and anaerobic Gram-positive cocci are the most frequently encountered organisms. The clinical presentations are lung abscess, lung gangrene and empyema, which all tend to take a slow and indolent course. Preferred localization are dependent lung segments, most often on the right side. For bacteriological examination in these infections, only transtracheal aspirate and aspirate from the lung or pleural space are considered adequate. In 26 cases of empyema treated in our hospital during the last 3 years, adequate specimens had been taken in 19. Fifteen had been adequately examined, and anaerobes were cultured in 6. Among 29 abscesses treated during the same period, adequate specimens had been taken in only 14, and 11 had been properly examined. Seven specimens grew anaerobes on culture. In prospective studies of transtracheal aspirate in 15 chronic bronchitics without emphysema, anaerobes were not demonstrated. In 11 patients with bronchiectasis, anaerobic bacteria were cultured in 3. Finally, no anaerobic bacteria could be demonstrated in the transtracheal aspirate from 76 patients with acute exacerbation of chronic bronchitis. Anaerobic, pulmonary infections do not represent an intriguing medical problem in our region. However, knowledge of these infections is necessary to secure adequacy in collection of specimens and in their bacteriological examination.     

Clinical spectrum of bacteroidaceae in a tertiary care hospital

Members of Bacteroidaceae family are the most commonly isolated anaerobic pathogens in humans. This study summarises our experience of isolation and antimicrobial susceptibility pattern of these anaerobes from diverse clinical infections in a tertiary care hospital. Over a period of 5 years, 611 samples were received for anaerobic culture. Of these, 53 specimens yielded 62 anaerobic isolates. Thirty of the 62 isolates (48.4%) belonged to Bacteroidacea family obtained from 29 patients. They comprised of 14 (14/32; 43.7%) Prevotella spp., 13 (13/32; 40.6%) Bacteroides spp., 3 (3/32; 9.3%) Porphyromonas spp and Fusobacterium (2/32; 6.2%). In 14 of 27 patients (48%) the infection was polymicrobial. All the isolated strains were sensitive to metronidazole. This study highlights need for adopting anaerobic culture technique as a routine diagnostic procedure and constant monitoring of antimicrobial susceptibility of all anaerobic isolates.     

Clinical characteristics of anaerobic bactibilia.

During a two-year period, 1,892 patients underwent biliary tract surgery at the Mayo Clinic. Both aerobic and anaerobic bile cultures were performed in 371 patients and 253 of these were positive. Anaerobes were isolated from 100 patients, although only twice in pure culture. Only aerobes grew from cultures from 153 patients. One hundred cases of biliary tract infections involving anaerobes and an equal number involving aerobes only were reviewed in order to determine their clinical characteristics. Prominent features of anaerobic bactibilia included (1) a history of complex, multiple, biliary tract surgeries often involving biliary-intestinal anastomoses and common bile duct manipulation, (2) severe symptoms, (3) high incidence of postoperative infectious complications, especially wound infections. Further analysis of anaerobic biliary infections suggested that Bacteroides fragilis was more often associated with serious pathologic conditions of the biliary tract than was Clostridium.     

Bacteriology of bronchial secretions in non-tubercular lower respiratory tract infections

Fifty samples of bronchial secretions collected from patients of non-tubercular lower respiratory tract infections through fiberoptic bronchoscopy (FOB) were cultured both for aerobic and anaerobic organisms. Thirty-three (66%) samples yielded bacteria. Out of these, thirty were isolated in pure culture and from three, a mixed growth of aerobic and anaerobic micro-organisms was obtained. Aerobic bacteria were the predominant isolates. Stephylococcus aureus (10), pseudomonas (9) and streptococcus pneumoniae (8) were the major aerobic isolates. Ciprofloxacin was found to be the most effective drug against aerobes and metronidazole against anaerobes in vitro susceptibility tests.     

Aerobic and anaerobic microbiology of paronychia

Pus specimens from 28 patients with paronychia of the finger yielded bacterial growth by techniques for cultivation of aerobic and anaerobic bacteria. Anaerobic and aerobic organisms only were isolated in pure culture in five (18%) and eight patients (29%), respectively; mixed aerobic and anaerobic flora were present in 15 patients (54%). Seventy-two isolates were recovered, or 2.6 isolates per specimen. The predominant anaerobic organisms were Gram-positive anaerobic cocci, Bacteroides species, and Fusobacterium species. The predominant aerobic organisms were Staphylococcus aureus, gamma-hemolytic streptococci, Eikenella corrodens, group A beta-hemolytic streptococci, alpha-hemolytic streptococci, and Klebsiella pneumoniae. Candida albicans was recovered in four cases. This study demonstrates the mixed aerobic and anaerobic bacteriology of paronychia.