Donna J. Blazevic

Rapid Gentamicin Bioassay Using a Multiple-Antibiotic-Resistant Strain of Klebsiella pneumoniae

A rapid bioassay for gentamicin levels in serum was developed by using a strain of Klebsiella pneumoniae that has multiple resistance to antibiotics. Assays were comparable when performed on either small or large petri plates, and results were available in 2 to 4 h. Studies showed an overall recovery of 97.6% for gentamicin alone or 104.5% in the presence of commonly used antibiotics. The procedure can be performed without the need to inactivate other antibiotics that may be present in the serum sample.

Antibiotic Susceptibility of the Subspecies of Bacteroides fragilis

Strains (115) of Bacteroides fragilis were identified at the subspecific level and were tested for susceptibility to ampicillin, cephalothin, chloramphenicol, clindamycin, penicillin, and tetracycline using an agar dilution technique. We tested the following strains: B. fragilis subsp. distasonis, 12; B. fragilis subsp. fragilis, 39; B. fragilis subsp. ovatus, 10; B. fragilis subsp. thetaiotaomicron, 32; B. fragilis subsp. vulgatus, 10; and B. fragilis subsp. “other,” 12. There were no marked differences in susceptibility between the subspecies. One strain of B. fragilis subsp. thetaiotaomicron had a minimal inhibitory concentration of 12.5 μg/ml for clindamycin, but all other strains were susceptible. All the strains were susceptible to chloramphenicol. Susceptibility to tetracycline was variable. Only a few strains were susceptible to the penicillins and cephalothin.

Susceptibility of Anaerobic Bacteria to Carbenicillin

One hundred and seventy-one strains of anaerobes were tested for susceptibility to carbenicillin by using agar dilution, broth dilution, and two disk diffusion methods. The minimal inhibitory concentration (MIC) for 67% of 51 strains of Bacteroides fragilis, 7 of 9 strains of Bacteroides melaninogenicus, and all of 8 strains of Eubacterium was 100 μg or less per ml. The MICs of the remaining anaerobes were 50 μg or less per ml. The broth dilution results were felt to be the most accurate of the four methods utilized.

Campylobacter fetus infections

Summary C. fetus ss jejuni is an important cause of gastroenteritis in humans. Simple methods for isolation of the organism have been developed, and laboratories should seriously consider the possible presence of this organism when culturing stool specimens.

Evaluation of the Modified Broth-Disk Method for Determining Antibiotic Susceptibilities of Anaerobic Bacteria

A total of 110 strains of anaerobic bacteria including 9 different genera was tested for antibiotic susceptibility by the modified broth-disk method of Wilkins and Thiel (1973), using prereduced media and the VPI anaerobic culture system. Results were compared with those obtained with an agar dilution technique with incubation in a GasPak jar. There was greater than 95% agreement between the two methods with ampicillin, cephalothin, chloramphenicol, and clindamycin, and 90% or greater agreement with erythromycin, penicillin, and tetracycline.

Malpractice in the clinical microbiology laboratory: Can you be sued?

Abstract Any failure of a microbiologist to follow the appropriate standard of care for the particular situation which causes injury to the patient can result in a serious lawsuit worth millions of dollars. However, most medical malpractice lawsuits end up being dismissed, most of the remainder are settled, often for small amounts of money, and those that go to trial are by a great majority won by the defendants (hospital, microbiologist, physicians, etc.).

Laboratory diagnosis of Mycoplasma pneumoniae infection.

In man M. pneumoniae most often causes a primary atypical pneumonia. The serum of many patients so afflicted will quickly show positive cold agglutinin and complement-fixation tests. Although nonspecific, these tests are rapid. Laboratories can also culture organisms from throat swabs and sputum in special mediums, but growth takes at least seven days and sometimes six weeks.