William J. Martin

In Vitro Antimicrobial Susceptibility of Anaerobic Bacteria Isolated from Clinical Specimens

The minimal inhibitory concentrations of 601 clinical isolates of anaerobic bacteria to 10 different antimicrobial agents were determined by an agar-dilution technique. Nearly all strains were resistant to kanamycin and gentamicin, although moderate activity to both drugs was noted with Fusobacterium sp., anaerobic cocci, some strains of Bacteroides melaninogenicus, and nonsporeforming gram-positive bacilli. Chloramphenicol at 12.5 μg/ml inhibited all but three of the strains tested. Tetracycline at 6.25 μg/ml had high activity against all groups tested, with the exception that only 39% of strains of Bacteroides fragilis were inhibited at this concentration. Excluding certain species of Bacteroides, the majority of anaerobes were inhibited by penicillin at 3.1 μg/ml or less and by cephalothin at 12.5 μg/ml or less. Lincomycin at 6.2 μg/ml or less was active against nearly all strains. Erythromycin at a concentration of 3.1 μg/ml was active against B. fragilis; however, erythromycin was less active against the other groups. Most of the minimal inhibitory concentrations of lincomycin exceeded those of clindamycin by fourfold. Rifampin inhibited virtually all strains at 3.1 μg/ml.

Cytomegalovirus Infections Associated with Leukocyte Transfusions

Patients randomized to receive or not to receive prophylactic leukocyte transfusions were evaluated prospectively for serologic, histologic, and cultural evidence of cytomegalovirus infection. Recipients of prophylactic leukocyte transfusions and control subjects were similar with regard to age, sex, underlying disease, immunosuppressive therapy, and number of other transfusions. The recipients of prophylactic leukocyte transfusions (mean, 23.1) had significantly more cytomegalovirus infections (19 of 31 versus seven of 27, p = 0.01) than did control patients receiving no leukocytes or only therapeutic leukocyte transfusions (mean, 3.8). Twenty-seven of 66 donors of leukocytes were seropositive for cytomegalovirus complement-fixation antibody, but cytomegalovirus was not isolated from any of 62 leukocyte transfusions cultured for virus. These results are consistent with the hypothesis that latent cytomegalovirus may be present in leukocytes of blood donors with previous cytomegalovirus infection and after transfusion may be activated to produce active cytomegalovirus infection.

Gram-negative rod bacteremia: microbiologic, immunologic, and therapeutic considerations.

During the last 2 decades, Gram-negative rod bacteremia has become the leading infectious disease problem in American hospitals. With improvements in conventional microbiologic techniques, bacteremic infection can be diagnosed reliably within 3 days using only three sets of cultures. Clinical management still requires aggressive, presumptive use of antimicrobials in patients with the most adverse host factors. In the latter group, the use of combinations of antibiotics that interact synergistically in vitro has improved clinical results. In bacteremia due to anaerobes, particularly Bacteroides species, drainage of infected sites is probably more important than specific drug therapy. Various host defects have been associated with Gram-negative bacteremia; the most common in the nonleukopenic patient is impaired opsonization. The evidence that endotoxins are involved in the pathophysiology of Gram-negative bacillemia is inferential. Nevertheless, both clinical and experimental evidence suggest that active or passive immunization with endotoxin components or antigens similar to Gram-negative polysaccharides may be protective.

BACTEREMIA OWING TO GRAM-NEGATIVE BACILLI: EXPERIENCES IN THE TREATMENT OF 137 PATIENTS IN A 15-YEAR PERIOD

Excerpt The evolution of effective antibiotic therapy has greatly altered the outlook of many infectious states, one of which is the invasion of the blood stream by microorganisms. With the multipl...

Intravenous Tubing Containing Burettes Can Be Safely Changed at 72 Hour Intervals

No studies testing the safety of changing intravenous systems containing in-line burettes at 72 hours in an intensive care setting have been performed. Patients entering a medical or surgical intensive care unit were alternatively assigned to have any line with an in-line burette changed at either 48 hour (105 patients) or 72 hour (65 patients) intervals. Daily quantitative cultures with a 2 ml aliquot of burette fluid were obtained. Contaminated burette fluid was detected in 60 of 1181 (5.0%, 95% confidence interval, 3.7% to 6.3%) samples from the burettes changed at 48 hour intervals, and in 40 of 901 (4.4%, 95% confidence interval, 3.0% to 5.8%) samples from 72 hour interval burettes. Significant bacterial contamination of burette fluid, defined as ten or more colonies per milliliter, occurred in only seven (0.6%) cultures from patients in the 48 hour interval group compared with only three (0.3%) cultures in the 72 hour group. None of the contaminated burette fluids was associated with a primary bacteremia. Change of in-line burettes in patients in intensive care at 72-hour intervals is safe and should result in substantial cost savings to hospitals.

Comparative in vitro activity of moxalactam, cefotaxime, cefoperazone, piperacillin, and aminoglycosides against gram-negative bacilli.

The in vitro activities of four new beta-lactam antimicrobial agents (moxalactam, cefotaxime, cefoperazone, and piperacillin) and the aminoglycosides against 744 recent clinical isolates of facultative gram-negative bacilli were compared simultaneously by the agar dilution method. The major in vitro difference of these newer beta-lactam compounds appeared to be their antipseudomonal activity; cefoperazone was the most active, whereas cefotaxime had the least potency. The aminoglycosides, however, had the most effective in vitro activity on a weight basis against Pseudomonas aeruginosa.

Comparative in vitro synergistic activity of new beta-lactam antimicrobial agents and amikacin against Pseudomonas aeruginosa and Serratia marcescens.

The in vitro synergistic activities of moxalactam, cefoperazone, or cefotaxime in combination with amikacin or piperacillin were compared against aminoglycoside-susceptible and aminoglycoside-resistant isolates of Pseudomonas aeruginosa and Serratia marcescens by the checkerboard agar dilution method. All antimicrobial combinations demonstrated some synergy, and no antagonism was observed. Moxalactam plus amikacin and piperacillin plus amikacin were most frequently synergistic (two-thirds of the isolates inhibited synergistically by each combination), whereas combinations of moxalactam, cefotaxime, or cefoperazone with piperacillin were synergistic against only 18 to 25% of the isolates. Moxalactam plus amikacin was the combination most often synergistic for amikacin-susceptible P. aeruginosa, and piperacillin plus amikacin was the combination most frequently synergistic for amikacin-resistant P. aeruginosa and amikacin-susceptible S. marcescens. These results demonstrate frequent in vitro synergistic activity between the new beta-lactam agents and amikacin (especially moxalactam or piperacillin with amikacin), but comparative clinical trials are needed to establish the relative efficacy and toxicity of these combinations.

In Vitro Studies of Piperacillin, a New Semisynthetic Penicillin

Piperacillin, a new semisynthetic penicillin, was compared with other semisynthetic penicillins, cephalosporins, and aminoglycosides by the agar dilution method against 3,600 isolates of facultative gram-negative bacilli, Bacteroides fragilis, and enterococci. At 64 μg/ml, piperacillin inhibited 90% of the isolates in each group of organisms tested except for Escherichia coli (83% inhibited by 64 μg/ml). Compared with carbenicillin, piperacillin had a 16-fold increase in activity by weight against Pseudomonas aeruginosa and the enterococcus, an 8-fold increase against Serratia marcescens, and a 4-fold increase against B. fragilis and Enterobacter species. Piperacillin was highly active against carbenicillin-resistant Klebsiella pneumoniae and inhibited many aminoglycoside-resistant organisms. Except for P. aeruginosa, the minimum bactericidal concentration of piperacillin was usually within one tube dilution of the minimum inhibitory concentration. Approximately one-third of the gram-negative bacilli were inhibited synergistically by piperacillin plus amikacin, but no synergy could be demonstrated against enterococci. Piperacillins in vitro activity against gram-negative bacilli was similar to gentamicins except that it also included B. fragilis, and piperacillin was decidedly superior to presently available penicillins against K. pneumoniae.

Chronic Osteomelitis: II. Treatment With Closed Irrigation and Suction

A study was made of chronic osteomyelitis in 75 patients, 40 of whom were treated by saucerization followed by closed irrigation and suction (group 1), and 35 patients who also were treated by saucerization but, instead of closed irrigation and suction thereafter, the bone defect was filled with either autogenous bone or muscle implants or simply closed secondarily (group 2). A comparison of these two groups (years 1962 through 1966) and a group of 112 patients (years 1953 through 1961) who could have been treated with closed irrigation and suction indicates that the highest rate of success was observed in the 40 patients treated by closed irrigation and suction after saucerization.

MICROCOCCAL BACTEREMIA WITHOUT ENDOCARDITIS: CLINICAL DATA AND THERAPEUTIC CONSIDERATIONS IN 109 CASES

Excerpt Infections caused byMicrococcus pyogenesvar.aureus(Staphylococcus pyogenes aureus)continue to offer a major therapeutic challenge. Micrococci appear to possess an almost singular ability to...