Multilaboratory comparison of growth characteristics for anaerobes, using 5 different agar media.

A multilaboratory study compared the growth of 30 fastidious anaerobes, using 5 different agar media: Wilkins-Chalgren (WC), WC with either whole or laked sheep blood, and Brucella supplemented with vitamin K(1) and hemin and either laked or whole sheep blood. The media were compared for quality and quantity of growth. Experiments were conducted either entirely in an anaerobic chamber or inoculated in ambient air with anaerobic incubation. The results showed that (1) any medium plus whole or laked blood was better than unsupplemented WC, (2) whole blood and laked blood additives gave similar results, (3) supplemented Brucella with whole or laked blood was superior to WC and WC with whole or laked blood, and (4) anaerobic and aerobic inoculation with anaerobic incubation gave similar results. Brucella agar supplemented with whole or laked blood supports the growth of fastidious anaerobic species better than the WC agars do.

In vitro efficacy of beta-lactam/beta-lactamase inhibitor combinations against bacteria involved in mixed infections.

Mixed infections are usually caused by a relatively limited range of bacteria, with the anaerobes and opportunistic pathogens contributing to their severity. In order to make the best therapeutic choice for a patient with a life-threatening infection, which is probably of mixed etiology, clinicians must be aware of the organisms that are likely to be involved, and the fact that most of them will produce beta-lactamase. Of the options available for empiric therapy, the beta-lactam/beta-lactamase inhibitor combinations represent a good choice. Their antibacterial spectra include both aerobic and anaerobic pathogens. Five combinations are available in clinical practice: ampicillin-sulbactam, piperacillin-tazobactam, ticarcillin-clavulanic acid, amoxicillin-clavulanic acid, and cefoperazone-sulbactam. More strains of clinically important anaerobic bacteria are susceptible to ampicillin-sulbactam than to either piperacillin-tazobactam or ticarcillin-clavulanic acid, which are also available widely and suitable for more life-threatening infections. In addition, sulbactam itself has the highest intrinsic activity of the beta-lactamase inhibitors against the opportunistic pathogen, Acinetobacter baumannii. Thus, ampicillin-sulbactam could be considered a drug of choice for the empirical treatment of mixed infections where there is a reasonable possibility of the presence of A. baumannii.

Gangrenous and/or perforated appendix: clinical outcome and in vitro susceptibility testing.

The data from this study indicate that cefoxitin was effective and generally well tolerated in the management of gangrenous and/or perforated appendicitis. No strong correlation was identified between in vitro susceptibility testing results and clinical outcome.

Susceptibility of bite wound bacteria to seven oral antimicrobial agents, including RU-985, a new erythromycin: considerations in choosing empiric therapy.

The susceptibility of 93 aerobic and 59 anaerobic bacteria isolated from human and animal bite wounds was determined by agar dilution. No agent tested (penicillin, oxacillin, cephalexin, sulfamethoxazole-trimethoprim, minocycline, erythromycin, and RU-965) was consistently active against all isolates. A total of 21% of the Bacteroides species, all isolated from human bites, were resistant to penicillin; 14 and 18% of the Pasteurella multocida isolates were resistant to erythromycin and oxacillin, respectively.

Treatment of anaerobic infections: an overview.

Increasing resistance on the part of anaerobes to several antimicrobial agents has been a problem in recent years. Mechanisms of resistance include production of inactivating enzymes such as beta-lactamases, plasmid-mediated transferable resistance and failure of the drug to penetrate the bacterial cell. Fortunately, availability of several new agents permits us to treat anaerobic infections effectively. However, it is now desirable to do routine in vitro susceptibility testing of anaerobes, especially in seriously ill patients. Newly introduced drugs and others still undergoing study are compared with the standard agents.

Susceptibility of anaerobic bacteria to thiamphenicol.

The activity of thiamphenicol, an analogue of chloramphenicol without a nitro group, was compared with that of chloramphenicol against anaerobic bacteria. A plate dilution technique on brucella agar supplemented with laked sheep blood and vitamin K1 was used. Chloramphenicol exhibited slightly greater activity than thiamphenicol in vitro, but the difference was too small to be of potential clinical significance.

Antimicrobial therapy for anaerobic infections.

Our increasing understanding of anaerobes and the infections they cause has reaffirmed that benzyl-penicillin is a useful agent when B. fragilis group organisms can be ruled out. At the same time, however, we have also learned that the number of instances in which penicillin-resistant bacteroides can be ruled out seems to be diminishing. For the most serious anaerobic infections, the clinician must turn to an agent such as chloramphenicol, clindamycin, or metronidazole. As a group, these drugs are the most reliably effective against clinically significant B. fragilis and most other anaerobes; gaps in their spectrum can be covered with benzyl-penicillin. A major drawback with chloramphenicol, in particular, remains its potential toxicity, a feature that underscores the importance of matching the antimicrobial weapon to the target. The less consistently reliable agents tend to be the less potentially toxic; they should be used if the anaerobic infection is judged not serious or life threatening. The more potent, potentially more toxic drugs should be used when life is in danger.

Clinical evaluation of moxalactam.

Moxalactam was administered intravenously or intramuscularly or both in doses of 1 to 12 g/day to 45 patients with clinically significant infections (17 soft tissue or bone, 9 pleuropulmonary, 9 septicemic, 6 urinary tract, and 4 intraabdominal infections). Mean 0.5-h postinfusion levels were 105 micrograms/ml for a 4.0-g dose, 44.7 micrograms/ml for a 2.0-g dose, and 18 micrograms/ml for a 1.0-g dose. We identified 28 isolates of Enterobacteriaceae, 10 Pseudomonas aeruginosa isolates, 9 Staphylococcus aureus isolates, and 15 anaerobic bacterial isolates. A total of 15 patients were clinically cured, 8 patients improved, 13 patients improved initially but suffered subsequent relapses or superinfections, and 10 patients failed therapy. Toxicity was generally minimal (reversible eosinophilia, and mild liver function abnormalities, and elevated prothrombin time). The selection or emergence of resistant organisms in 17 patients during treatment (particularly Pseudomonas, enterococci, and Candida) was a disturbing feature of therapy. Our results were generally favorable, considering the complicated underlying medical problems of this group of patients.

Clostridium difficile and cytotoxin in feces of patients with antimicrobial agent-associated pseudomembranous colitis.

Thirty patients with antimicrobial agent-associated pseudomembranous colitis (PMC) were studied for the presence of Clostridium difficile and its cytotoxin in feces. Either colonoscopy or barium enema radiography was required in three patients for the diagnosis of PMC because of nondiagnostic findings at sigmoidoscopy. Both the organism and cytotoxin were detected in 27 of the 30 patients; Staphylococcus aureus was excluded as the cause of PMC in two of the remaining patients. Eighteen of 19 patients with C. difficile-induced PMC who were treated with oral vancomycin had a salutary response; seven patients, however, had a relapse of colitis following the discontinuation of vancomycin. In general, relapses of colitis responded to retreatment with vancomycin. The implication of C. difficile as a cause of diarrhea is best achieved by the demonstration of colonic mucosal plaques or of a pseudomembrane. The value of fecal culture for C. difficile and cytotoxin assay is limited by the existence of asymptomatic carriers.

Rapid method that aids in distinguishing Gram-positive from Gram-negative anaerobic bacteria.

Several species of anaerobic bacteria display variable Gram stain reactions which often make identification difficult. A simple, rapid method utilizing a 3% solution of potassium hydroxide to distinguish between gram-positive and gram-negative bacterial was tested on 213 strains of anaerobic bacteria representing 19 genera. The Gram stain reaction and KOH test results were compared with the antibiotic disk susceptibilities (vancomycin and colistin) the preliminary grouping of anaerobic bacteria. All three procedures were in agreement for the majority of strains examined. Some strains of clostridia, eubacteria, and bifidobacteria stained gram negative or gram variable; the KOH and antibiotic disk susceptibility tests correctly classified these strains as gram-positive. The KOH test incorrectly grouped some strains of Bacteroides sp., Fusobacterium sp., Leptotrichia buccalis, and Veillonella parvula, but all Gram stain results for these strains were consistent for gram-negative bacteria. The KOH test is a useful supplement to the Gram stain and antibiotic disk susceptibility testing for the initial classification of anaerobic bacteria.

Abnormalities in synovial fluid of patients with septic arthritis detected by gas-liquid chromatography.

Gas liquid chromatography was performed on synovial fluid of 94 patients with exudative arthritis. A relatively constant pattern of peaks was obtained in all synovial fluid samples. Lactic acid was increased in synovial fluid of patients with septic arthritis excluding gonococcal arthritis. In addition 2 constant peaks with retention time of 546 and 848 seconds in the chromatogram usually showed a significant increase in the synovial fluids of patients with septic arthritis (including gonococcal arthritis) but not in those from patients with sterile inflammatory or degenerative arthritis. In 1 patient with pseudomonas arthritis an increase in the peaks was noted with clinical and bacteriological relapse and subsequently there was a gradual return to normal levels during clinical improvement. Increase in synovial fluid lactic acid is useful in the diagnosis of septic arthritis. Identification of the compounds represented by the 2 peaks, which presumptively correspond to n-valeric and n-hexanoic acid, may provide further information on diagnosis, prognosis and pathogenesis of arthritis and may help in the differentiation between gonococcal and nongonococcal arthritis.

Fecal flora in different populations, with special reference to diet.

Although potent antimicrobial agents may effect rapid and significant changes in fecal microflora, changes in diet or dietary supplements usually produce modest changes by comparison. It may be, however, that even such minor changes may result in significant changes in metabolic activity, particularly in terms of production of possible carcinogens or cocarcinogens. It is clear that significant changes may occur in metabolic activity without major qualitative or quantitative changes in the fecal microflora. Other research that might help explain the epidemiological observations of the association between diet and colon cancer would be studies of the flora at different levels of the gastrointestinal tract (particularly the cecum and small bowel), studies of the mucosa-associated flora at different levels, and long-term dietary studies.

Synovial fluid lactic acid. A diagnostic aid in septic arthritis.

Lactic acid concentrations in the synovial fluid of 84 patients with acute monoarticular arthritis were determined by gas liquid chromatography. Lactic acid values in 27 cases of nongonococcal septic arthritis were strikingly higher (mean 1170 mg/100ml) than in 45 cases of inflammatory or degenerative arthritis (mean 34 mg/100 ml), as well as in 12 cases of gonococcal arthritis (mean 27 mg/100 ml). With the proper equipment, determination of lactic acid can be a relatively rapid, reliable procedure. Synovial fluid lactic acid concentrations therefore can be used as a rapid, supplemental diagnostic aid in differentiating nongonococcal septic arthritis from both gonococcal and nonseptic acute arthritis.

Effect of silver nitrate application on the conjunctival flora of the newborn: and the occurrence of clostridial conjunctivitis.

Newborn conjunctival cultures were obtained from 35 babies prior to silver nitrate application and 48 hours later. On initial culture, 46 facultative bacteria and 27 anaerobes were recovered; 48 facultative and 18 anaerobes were recovered after 48 hours. Haemophilus vaginalis, Bacteroides species and anaerobic cocci decreased in numbers, whereas S. epidermidis, Micrococcus and Propionibacterium acnes increased during this time interval. Clostridial species were isolated from two cases who developed conjunctivitis, along with Peptostreptococcus in one of the cases. In vitro experiments demonstrated lack of killing of C. perfringens in silver nitrate concentrations of 0.1 percent, even after 24 hours exposure.

Cefoxitin: clinical evaluation in thirty-eight patients.

Clinical and bacteriological efficacy, patient tolerance, and toxicity of cefoxitin, a beta-lactamase-resistant cephamycin, were evaluated in 38 patients; 13 had soft tissue infection, 12 had pneumonia, 3 had urinary tract infection, 2 had peritonitis, and 4 had miscellaneous infections. In five patients, infection was clinically evident, though not bacteriologically proven. The latter patients were evaluated with regard to tolerance and toxicity only. Among the 34 infections in 33 patients, 71% were considered clinically cured; 86% of those patients who could be recultured were bacteriologically cured. Phlebitis was noted in 32% of the total group, and eosinophilia was observed in 16%. Unexplained deterioration in renal function occurred in two patients. Mean peak cefoxitin levels in serum were 72 mug/ml 30 min after a 2-g infusion and 32 mug/ml 30 min after a 1-g infusion. Cefoxitin was more active against facultatively and obligately anaerobic gram-negative organisms isolated from these patients than was cephalothin.

Comparison of three procedures for biochemical testing of anaerobic bacteria.

The Analytab Products, Inc. (API), anaerobic multitest microsystem (MICRO) was compared with the Center for Disease Control conventional (CONV) thioglycolate (supplemented with hemin and vitamin K1) system and with pre-reduced anaerobically sterilized (PRAS) media as recommended by the Virginia Polytechnic Institute. Growth from a solid medium was suspended to produce standard inocula. Substrates included 16 carbohydrates, indole, urea, gelatin, and esculin. API strips were inoculated in air and incubated in GasPak (BBL) jars. MICRO tests were read at 1 and 2 days. CONV tests at 1, 2, and 7 days, and PRAS tests at 3 weeks. One hundred thirty well-characterized strains of anaerobes (76 gram-negative rods, 16 cocci, 26 gram-positive nonsporeforming rods, and 12 clostridia), including 48 reference strains, were studied. Of 2,600 tests performed, 2,085 (80.2%) showed agreement with all three methods. There was 90.9% agreement between the MICRO and CONV, 84.9% between the MICRO and PRAS, and 84.6% between the CONV and PRAS tests. All MICRO tests were reliable except for indole, which was not sensitive enough, and gelatin, which was very insensitive. The MICRO system permits performance of biochemical tests at the workbench in the average clinical laboratory without the need for expensive equipment and time-consuming procedures.