What are anaerobic cocci?

Gram-positive anaerobic cocci

Gram-positive anaerobic cocci (GPAC) are a heterogeneous group of organisms defined by their morphological appearance and their inability to grow in the presence of oxygen; most clinical isolates are identified to species in the genus Peptostreptococcus. GPAC are part of the normal flora of all mucocutaneous surfaces and are often isolated from infections such as deep organ abscesses, obstetric and gynecological sepsis, and intraoral infections. They have been little studied for several reasons, which include an inadequate classification, difficulties with laboratory identification, and the mixed nature of the infections from which they are usually isolated. Nucleic acid studies indicate that the classification is in need of radical revision at the genus level. Several species of Peptostreptococcus have recently been described, but others still await formal recognition. Identification has been based on carbohydrate fermentation tests, but most GPAC are asaccharolytic and use the products of protein degradation for their metabolism; the introduction of commercially available preformed enzyme kits affords a physiologically more appropriate method of identification, which is simple and relatively rapid and can be used in routine diagnostic laboratories. Recent reports have documented the isolation in pure culture of several species, notably Peptostreptococcus magnus, from serious infections. Studies of P. magnus have elucidated several virulence factors which correlate with the site of infection, and reveal some similarities to Staphylococcus aureus. P. micros is a strongly proteolytic species; it is increasingly recognized as an important pathogen in intraoral infections, particularly periodontitis, and mixed anaerobic deep-organ abscesses. Comparison of antibiotic susceptibility patterns reveals major differences between species. Penicillins are the antibiotics of choice, although some strains of P. anaerobius show broad-spectrum beta-lactam resistance.

Susceptibility testing of anaerobic bacteria: myth, magic, or method?

The demand for susceptibility testing of anaerobes has increased, yet consensus as to procedure and interpretation in this area has not been achieved. While routine testing of anaerobic isolates is not needed, certain isolates in specific clinical settings should be tested. Also, laboratories may monitor their local antibiograms by doing periodic surveillance batch testing. The National Committee for Clinical Laboratory Standards has published a protocol of methods approved for susceptibility testing of anaerobic bacteria. Both agar and broth microdilution are included; however, the broth disk elution method is no longer approved by the National Committee for Clinical Laboratory Standards because of method-related interpretive errors. A number of newer methods are undergoing evaluation and seem promising. Clinicians and microbiologists reviewing susceptibility reports should be aware of sources of variability in the test results. Variables in susceptibility testing of anaerobes include the media and methods used, organisms chosen for testing, breakpoints chosen for interpretation, antibiotic, and determination of endpoint. Clustering of MICs around the breakpoint may lead to significant variability in test results. Adherence of testing laboratories to approved methods and careful descriptions of the method and the breakpoints used for interpretation would facilitate interlaboratory comparisons and allow problems of emerging resistance to be noted. A variety of resistance mechanisms occurs in anaerobic bacteria, including the production of beta-lactamase and other drug-inactivating enzymes, alteration of target proteins, and inability of the drug to penetrate the bacterial wall. Antimicrobial resistance patterns in the United States and abroad are described.

In vitro activity of cefoperazone plus sulbactam compared with that of other antimicrobial agents against anaerobic bacteria

The activity of two cefoperazone-sulbactam combinations against anaerobic bacteria was tested and compared both with that of cefoperazone alone and with that of other commonly used antimicrobial agents. Imipenem was the most active of the tested agents, followed by chloramphenicol, metronidazole, and cefoperazone-sulbactam (90 to 100% of bacterial growth inhibited). Clindamycin and cefoxitin inhibited approximately 80%, cefoperazone inhibited 63%, and penicillin G inhibited 47% of the strains tested. The agents were variable in activity against the Bacteroides fragilis group, with percents susceptible as follows: cefoperazone-sulbactam, imipenem, metronidazole, and chloramphenicol, 99 to 100%; cefoxitin and clindamycin, approximately 80%; cefoperazone, 49%; and penicillin G, 15.5%.

Effect of culture medium and carbon dioxide concentration on growth of anaerobic bacteria and medium pH

Two Danish agars, Danish Blood Agar (D.B.A.) and Anaerobic Agar (A.A.), were evaluated for their ability to support growth of 47 clinically isolated anaerobic strains in 5 different CO2-concentrations ranging from 0-10% CO2. CO2 and the use of an enriched medium (A.A.) are essential for satisfactory recovery of anaerobes. No gain could be seen when raising the CO2-concentration above 5%. The surface pH of the agars was measured both on non-inoculated and inoculated plates at room temperature and anaerobic incubation in the 5 different CO2-concentrations at 37 degrees C. Temperature change from room temperature to 37 degrees C resulted in a pH decrease of 0.1 units. There was a CO2-mediated decrease in pH (approximately 0.05 units/pr. CO2%) on non-inoculated media. On inoculated plates there was a minor additional fall in pH, which increased with time of incubation, but first became significant when the plates were incubated for more than 24 h. The use of 5% CO2 and A.A. is recommended for antimicrobial susceptibility studies on solid media.

Survival of gram positive anaerobic cocci on swabs and their isolation from the mouth and vagina

The survival of Gram positive anaerobic cocci on plain cotton wool and albumin coated swabs held in various transport media was investigated. Results suggested that in most cases Amies', Stuart's and VMGII media do not offer any more protection to the bacteria than storing swabs dry in their containers. A technique was developed for the isolation and identification of Gram positive anaerobic cocci from the mouth and vagina, incorporating bicozamycin in the medium as a selective agent. Few strains were recovered from the oral cavity, but larger numbers were isolated from the vagina. Using a minimum number of antibiotic sensitivity and biochemical tests, including analysis of end products by gas-liquid chromatography, most isolates were identified to species level.

Prophylaxis with tinidazole in oral surgery. Tissue penetration and effect on the oral microflora

10 patients with odontogenic cysts were given 500 mg tinidazole orally every 12 h for infection prophylaxis before cystectomy. The administration started 48 h before operation and lasted for 7 days. Samples for assay of tinidazole were collected from blood plasma and cystic fluid during surgery. Saliva samples for microbiological studies of the normal flora were obtained before, during and after the antibiotic administration period. Mean concentrations of tinidazole in plasma and cystic fluid were 10.7 mg/l and 10.0 mg/l, respectively. The anaerobic flora was suppressed in all patients and two patients were colonized with enterobacteria, and two with fungi. No anaerobic bacterial strains resistant to tinidazole emerged during the treatment period. It is concluded that tinidazole can be administered prophylactically 48 h before oral surgery, in order to obtain maximal tissue concentration, without risk of the emergence of resistant bacterial strains or severe ecological disturbances of the oral microflora.

The enumeration of Bacteroides fragilis group organisms from sewage and natural waters

A membrane filtration technique has been developed for the enumeration of Bacteroides fragilis group (BFG) organisms from sewage and natural waters. The method uses the agar medium of Wilkins and Chalgren supplemented with gentamicin, penicillin, aesculin and ferric ammonium citrate. Membrane filters with 0.22 micron pores were significantly more efficient than those with 0.45 micron pores in the isolation of BFG. A preliminary incubation period of 4 h at 30 degrees C prior to 44 h at 37 degrees C yielded significantly higher numbers of BFG than direct incubation at 37 degrees C for 48 h.

A selective agent for anaerobic cocci

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Tinidazole--microbiology, pharmacology and efficacy in anaerobic infections

Tinidazole is a 5-nitroimidazole with selective activity against anaerobic bacteria and protozoa. It is bactericidal at low concentrations and its spectrum covers most anaerobic bacteria and some capnophilic microorganisms. Anaerobic bacteria known to be resistant to tinidazole include anaerobic streptococci, actinomyces and propionibacteria. Tinidazole is one of the most active antibacterial agents against Bacteroides fragilis which is one of the most resistant species of anaerobic bacteria. Only a few strains have been reported to be resistant. Tinidazole has been shown to be efficacious in protozoal infections such as trichomonal vaginitis, amoebiasis and giardiasis. Clinical studies have also shown that tinidazole is efficacious in the treatment of anaerobic infections including respiratory tract infections, intra-abdominal sepsis and obstetrical and gynecological infections. Since tinidazole has no activity against aerobic bacteria, it must be combined with other antibacterial agents in the treatment of mixed infections involving aerobic and anaerobic bacteria. Tinidazole has also been used successfully alone or in combination with other antimicrobial agents for prophylaxis in patients undergoing elective colonic and abdominal surgery, emergency appendectomy and gynecological surgery.

Dispersal of non-sporeforming anaerobic bacteria from the skin

Dispersal of non-sporeforming anaerobic bacteria was studied. Skin samples were taken from the subjects, and dispersed from different parts of the body was examined. The number of anaerobic bacteria dispersed was not correlated to their density on the surface of skin area exposed. The highest density of anaerobic bacteria on the skin was found in the face and upper trunk, but the highest yield of anaerobic bacteria dispersed came from the lower trunk. The dominant anaerobic bacteria dispersed were Propionibacterium acnes, but Propionibacterium avidum, Propionibacterium granulosum and Gram-positive cocci were also isolated from the dispersal samples. Peptococcus magnus was the most common coccus isolated. For the less frequently isolated bacteria, the best correlation was found between the perineal flora and airborne bacteria. A comparison was also made of bacterial dispersal by naked and dressed subjects. The dispersal of both aerobic and anaerobic bacteria was higher when the subjects were dressed in conventional operating theatre cotton clothing than when they were naked. The increased dispersal of anaerobic bacteria when the subjects were dressed was mainly due to increased dispersal of Propionibacterium sp.

Prevalence of bacteria in the vagina of normal young women

We report on factors related to the prevalence of bacteria in the vagina of 1498 women who were attending a family planning clinic. Anaerobes were significantly commoner in women with an abnormal vaginal discharge on clinical examination, in women with a history of a troublesome vaginal discharge and in women who used an intrauterine contraceptive device (IUCD) than in others. The association between anaerobes and abnormalities of vaginal discharge was found both in women who used the IUCD and in women who did not. We found no significant associations between symptoms and other bacterial species or combinations of species. Coliforms were significantly commoner in women who did not use tampons, in women who used the diaphragm and in women who had received recent antibacterial or antifungal treatment than in others. Lactobacilli were significantly commoner in women who used the contraceptive pill, and were significantly less common in women who harboured Candida albicans, anaerobes, coliforms or enterococci and in women who had been treated with antibacterial drugs, than in others. We found no important associations between the presence of bacteria and the patients' age, parity or social class.

Mechanisms of pathogenicity of anaerobic bacteria of clinical interest

The host factors leading to anaerobic infection and the various models of anaerobic infection, namely direct effect of a single toxin, multiple toxin-aggressin-systems, enterotoxic mechanisms, endogenous infections with non-clostridial anaerobes, and synergistic infections, are reviewed. Production of carcinogens and co-carcinogens by anaerobes is also discusssed.

Effect of tinidazole on the oral, throat, and colon microflora of man

Tinidazole in capsules was given orally in doses of 150 mg twice per day for 7 days to ten subjects. Saliva, throat, and faecal specimens were taken up to 16 days after administration for cultivation of aerobic and anaerobic bacteria and for assay of tinidazole. Mean peak serum levels of tinidazole varied between 3.3 microgram/ml to 5.4 microgram/ml. The saliva concentrations of tinidazole were between 2.9 microgram/ml to 5.9 microgram/ml. No concentration of tinidazole was detected in faeces. In saliva, a slight decrease in the numbers of fusobacteria was found, but no other changes in the oral, throat, or colon microflora were observed.