Drug-resistant Mycobacterium tuberculosis in Korean isolates.

Tuberculosis is a common disease in developing countries. An increasing incidence of resistance to isoniazid (INH) and streptomycin in organisms isolated from patients who contracted their disease in these countries, particularly in the Far East, is well recognized. This drug resistance has led to the recommendation of empirically beginning a regimen in patients with tuberculosis from the Far East of INH, ethambutol, and rifampin. This report documents the increasing incidence of resistance in isolates from Korea to ethambutol and rifampin in addition to INH and streptomycin. It suggests that the empiric use of INH, ethambutol, and rifampin in this group of patients could potentially lead to resistance to all of these drugs because of a significant amount of multidrug resistance. A regimen of INH, rifampin, pyrazinamide, and capreomycin is suggested as appropriate initial therapy in these patients based on the in vitro sensitivity data presented and initial clinical experience.

Antibiotic susceptibilities of human isolates of Pasteurella multocida.

Seventeen human strains of Pasteurella multocida, biochemically similar to, if not identical with, isolates of animal origins, were tested for susceptibility to 16 antimicrobial agents utilizing a microtiter broth dilution technique. Ten of these isolates were also tested against 11 antibiotics by disk diffusion. The most active drugs with respect to the median minimal inhibitory concentration (micrograms per milliliter) were tetracycline (0.09), penicillin G (0.78), ampicillin (0.78), carbenicillin (1.56), cephalothin (1.56), and chloramphenicol (1.56). With the exception of tetracycline, the median minimal inhibitory concentration and minimal bactericidal concentration values were equal or differed by no more than a factor of two. The semisynthetic penicillins clindamycin, erythromycin, and aminoglycosides had relatively low activities, suggesting that these agents would be poor choices for the treatment of P. multocida infections.

Infections caused by Rhodochrous.

Organisms conforming to "rhodochrous taxon" were isolated from three immunocompromised patients, suggesting a pathogenic role for the organisms. The organisms are partially acid-fast, gram-positive catalase positive rods which form orange or red colonies aerobically in three or four days on Sabouraud, Mueller-Hinton and Middlebrook 7H-10 agars. They are differenitated from Nocardia by morphology and ability to degrade ethylene glycol in 7H-10 media. Two of these clinical isolates and a reference strain were injected intraperitoneally into guinea pigs, half of which received methylprednisolone intramuscularly beginning three days prior to inoculation. Steroid-treated animals exhibited clinical illness, diffuse peritonitis and recovery of inoculated organisms whereas one of three nonsteroid-treated animals exhibited a localized abscess without recovery of organisms. This study suggests that rhodochrous may be pathogenic under conditions of immune compromise.

Evaluation of the oxi/ferm tube system with selected Gram-negative bacteria.

The Oxi/Ferm test system was evaluated for accuracy and reliability for identification of nonfermentative and oxidase-positive fermentative bacteria by using 375 bacterial strains obtained from stock culture and clinical specimens. The Oxi/Ferm system is a compartmentalized tube containing eight media to provide nine biochemical test results. When combined with the oxidase test, the results corresponding to the positive reactions are totaled and the composite number is located in the coding manual to identify the organisms. The 375 isolates studied were evaluated for accuracy of identification, using both the original and revised code manuals. In comparison with the conventional media used, there was 100% correlation in tests for hydrogen sulfide and indole production, over 96% for nitrogen gas, arginine, and urease, over 92% for xylose and dextrose oxidation, and less than 90% for citrate utilization and dextrose fermentation. There was an overall accuracy in identification of 89.3% using the original manual, with accuracy revised slightly upward to 90.7% using the revised manual. There was 100% accuracy in identification with 44.0% of the strains tested (11 species) using the original manual and with 66.1% (16 species) using the revised manual. Thirteen of the 40 original misidentifications and 14 of 35 revised misidentifications resulted from failure to code and were unidentifiable by Oxi/Ferm. The remainder were incorrectly identified or could not be differentiated from closely related strains. Eleven strains of Alcaligenes odorans were correctly identified using the original code, whereas no code was provided in the revised manual. The Oxi/Ferm system is both simple and rapid and is satisfactory for identification of the more common isolates.

Evaluation of the rapid decarboxylase and dihydrolase test for the differentiation of nonfermentative bacteria.

A rapid medium for the detection of lysine and ornithine decarboxylase and arginine dihydrolase activity of 439 strains of gram-negative, nonfermenting bacteria was evaluated and compared with Moeller decarboxylase medium. Results were obtained in 4 to 24 h using the rapid medium, whereas Moeller medium often required extended (3 to 7 days) incubation. There was 100% agreement in the lysine tests with both media and almost 100% agreement in the ornithine tests. There was 91% agreement in the arginine tests, with the significance of discrepant results discussed. The sensitivity, specificity, and quick results obtained by the rapid test make it a suitable substitute for Moeller medium for the identication of gram-negative, nonfermenting bacteria.