Biomedical subjects

R E Badal

Publications and source records attributed to R E Badal.

6 recordsLinked to original sources

PubMed1979

Piperacillin susceptibility tests by the single-disk agar diffusion technique.

Piperacillin is a new semisynthetic penicillin with a spectrum of activity broader than that of carbenicillin or ticarcillin. Studies were performed to establish standards for agar diffusion susceptibility tests with piperacillin disks. Tests with 100-, 150-, and 200-micrograms piperacillin disks and with 100-micrograms carbenicillin disks were evaluated. With both penicillins, 100-micrograms disks were satisfactory, in spite of the fact that piperacillin is a larger molecule and diffuses at a slower rate. With both carbenicillin and piperacillin disks, resistant strains of Staphylococcus aureus produced zones less than or equal to 28 mm and susceptible strains gave zones greater than or equal to 29 mm in diameter. When testing other microorganisms, zone standards of less than or equal to 13 mm for resistant (minimal inhibitory concentration, greater than or equal to 256 micrograms/ml) and greater than or equal to 17 mm for susceptible (minimal inhibitory concentration, less than or equal to 64 micrograms/ml) are recommended for tests with 100-micrograms piperacillin disks. Similar zone standards are currently recommended for carbenicillin and ticarcillin disk tests.

Bacteria↗

PubMed1979

Rapid identification of Enterobacteriaceae with the micro-ID system versus API 20E and conventional media.

The Micro-ID system for rapid (4 h) identification of Enterobacteriaceae was evaluated by testing 433 enteric bacilli and 9 other gram-negative bacilli. Each isolate was identified with conventional tubed media and was also tested in the Micro-ID and API 20E systems. The overall accuracy of both systems was 97%. Micro-ID tests for the Voges-Proskauer reaction, indole and H2S production, and ornithine and lysine decarboxylase all demonstrated a 97 to 99% correlation with conventional methods. Only 86% of the Micro-ID urease tests agreed with Christenson urea agar. Two inoculum densities were tested in Micro-ID panels, with 157 stock cultures. Over 90% of the tests were unaffected by changes in inoculum density. Tests with four control strains suggested that the Micro-ID system was more reproducible when a light inoculum was used. The Micro-ID system was found to be a very convenient method for rapid, accurate, and precise identification of the Enterobacteriaceae.

Bacteriological Techniques↗

PubMed1979

Identification of Enterobacteriaceae in frozen microdilution trays prepared by Micro-Media Systems.

Frozen microdilution trays, with 20 different biochemical test media for identification of Enterobactericeae, were evaluated. The test panels were those provided by Micro-Media Systems (MMS), who also provided a code book for interpretation of the test results. The interpretations of the MMS test system and of the Analytab API 20E test system were compared with those obtained from tests with conventional media. Tests with 468 Enterobacteriaceae demonstrated nearly comparable results with the two commercial systems. About 6% (API) and 7% (MMS) of the isolates could not be identified without additional tests, and another 3% (MMS) to 4% (API) of the isolates gave test patterns that were not found in the code books. One to three percent of the isolates were misidentified. It was concluded that the MMS Enteric Quad Panels provide an efficient, relatively inexpensive, and reasonably accurate method for identification of the Enterobacteriaceae.

Bacteriological Techniques↗

PubMed1979

Piperacillin (T-1220), a new semisynthetic penicillin. II. In vitro antimicrobial activity and synergy comparison with carbenicillin and gentamicin.

Piperacillin, a new semisynthetic penicillin, was found to have potent antimicrobial activity against nearly all (405) tested bacterial species. Piperacillin was consistently 4 approximately 16-fold more active than carbenicillin against the Enterobacteriaceae, 16 approximately 32-fold against Pseudomonas aeruginosa and Pseudomonas species, and 16-fold against Streptococcus faecalis. Carbenicillin and piperacillin were equally effective against Staphylococcus aureus, but inactivated by beta-lactamase. A 38% overall synergy rate for the piperacillin-gentamicin combination was identified, a finding similar to that for carbenicillin-gentamicin. Highest incidences of synergy were found for both antibiotic pairs tested on gentamicin-resistant isolates (Ps. aeruginosa and Providencia). In vitro findings suggest that piperacillin alone or in combination with aminoglycosides may be highly efficacious in the treatment of most serious bacterial infections.

Bacteria↗

PubMed1977

Reliability of the microdilution technic for detection of methicillin-resistant strains of staphylococcus aureus.

To determine whether the microdilution technic for antimicrobic susceptibility testing could detect the hetero-resistance of "methicillin"-resistant Staphylococcus aureus, 100 stock cultures (54 methicillin-susceptible and 46 methicillin-resistant) were tested against methicillin, oxacillin, nafcillin and cephalothin. Each drug was diluted in Mueller-Hinton broth and in Mueller-Hinton broth with 5% NaCl. Minimum inhibitory concentration (MIC) determinations were made after 20-24 hours at 35 C and again after 48 hours of incubation. With one exception, methicillin resistance was detected in Mueller-Hinton broth when the trays were reincubated and read after 48 hours. Earlier detection of methicillin resistance was possible when the penicillinase-stable penicillins were diluted in broth containing 5% NaCl. Further studies suggest that the addition of NaCl to the broth medium might improve the stabilities of methicillin, oxacillin, and nafcillin during storage of the frozen microdilution trays. Either nafcillin or oxacillin would appear to be the best representative of the penicillinase-stable penicillins. Standardized disk-diffusion tests with cephalothin disks indicated that most methicillin-resistant strains are susceptible to cephalothin. However, there is reason to believe that such in-vitro test results might be inappropriate. With microdilution tests, most methicillin-resistant isolates were more resistant to cephalothin than were the methicillin-susceptible strains, but the MIC's for both types of staphylococci were generally within the range of concentrations that can be obtained during therapy. The addition of NaCl to the microdilution tests with cephalothin did not alter the test results significantly.

Indicator Dilution Techniques↗

PubMed1976

Short-term storage of six penicillins and cephalothin in microdilution trays for antimicrobial susceptibility tests.

To perform microdilution antimicrobial susceptibility tests efficiently, broth dilutions of the antimicrobial drugs should be prepared in large batches and stored frozen until needed. Studies were carried out to document the stability of ampicillin, benzylpenicillin, carbenicillin, methicillin, oxacillin, nafcillin, and cephalothin in microdilution trays during storage at -20 and -60 C. No significant deterioration was noted after 21 days of storage, as detected by bioassay and by replicate minimal inhibitory concentration determinations with control organisms. No significant differences were noted moreover between trays stored for three weeks at -20 C and those stored at -60 C. The microdilution technique was found to be a highly reproducible method for quantitative determination of antimicrobial susceptibility.

Biological Assay↗