Initial screening for antituberculous drug resistance at an inpatient facility in Leon, Nicaragua

Antituberculous (anti-TB) drug resistance has become a major tuberculosis control issue in the United States, where this situation has closely paralleled the current acquired immunodeficiency syndrome epidemic associated with human immunodeficiency virus type-1 (HIV-1) infections. In less developed countries, especially those like Nicaragua with an apparently low prevalence of known HIV-1 infections, less is known about the epidemiology of antituberculous drug resistance. To understand the potential extent of this problem in Nicaragua, we conducted a cross-sectional prevalence study at Nicaragua's only inpatient tuberculosis treatment facility, located in Leon, Nicaragua. A radiometric method was used during recovery, purification, and drug susceptibility testing of clinical Mycobacterium tuberculosis isolates. Resistance to at least one of the major anti-TB medications was found in 15 (40.5%) of 37 sputum isolates, of which seven (19%) were resistant to either isoniazid alone, or to isoniazid plus another agent other than rifampin. Five were resistant to at least isoniazid and rifampin (i.e., 13.5% demonstrated multidrug resistance). Two isolates were resistant to pyrazinamide alone, and one was resistant to streptomycin alone. These initial results suggest that anti-TB drug resistance is a defined problem for tuberculosis control programs in Nicaragua, a problem that is largely related to individual noncompliance, lack of extensive drug susceptibility testing facilities, and a general unavailability of expensive anti-TB medications for re-treatment. Ongoing surveillance for drug resistance, using the methodology presented here, might assist Nicaraguan public health officials in their tuberculosis control programs.

Cryptococcal antigen detection from the urine of AIDS patients

Cryptococcal disease occurs in < or = 10% of AIDS patients. Detection of the capsular polysaccharide antigen of the yeast in spinal fluid or serum is used to establish the diagnosis. In addition, cryptococcal antigen (CAg) analysis is used to adjust treatment and evaluate recurrence of active disease. A specimen such as urine, obtained noninvasively, would be optimum for this evaluation. Urine, cerebrospinal fluid (CSF), and serum for CAg analysis, and culture of urine and CSF, were obtained for 103 sets of specimens from 92 patients. CSF and urine specimens for CAg were analyzed with and without pronase treatment; serum was analyzed with pronase only. Twenty percent (21 of 103) of specimen sets showed CAg from eight patients. In all cases, patients with positive CSF and/or serum titers also had positive urine titers. Titers were always serum > CSF > urine, with ranges of 1: 64-65000; 1: 64-6250; and 1: 2-512, respectively. Pronase treatment did not affect CSF titers, but 14 of 23 titers from urine treated with pronase were at least one dilution higher than those without treatment. No false-positive reactions were observed during the study. CSF cultures were positive from seven of eight, and urine cultures were positive from five of eight patients with CAg. These results indicate that urine can be used as a specimen for detection of CAg in AIDS patients and that use of pronase may increase its sensitivity.

Detection and identification of Mycobacterium directly from BACTEC bottles by using a DNA-rRNA probe

Detection and identification of mycobacterial species using DNA-rRNA probes from colonies has been used for some time. Guidelines for probe use with a specific minimum growth index (GI) cutoff from BACTEC 12B bottles or its use with 7H9 broth has not been defined. This study defined this minimum GI guideline. Clinical specimens received during the study period were decontaminated and directly inoculated into BACTEC 12B bottles and appropriate solid media. An initial probe test was performed at a GI reading of > or = 100. An additional probe test was made at GI of > or = 300. A total of 1377 specimens were processed with 98 specimens containing 99 isolates of Mycobacterium. Of these, 82 were M. avium complex (MAC), six were M. tuberculosis (Mtb), and 11 were other species. At a GI of > or = 100, 82% of MAC were detected; at a GI of > or = 300, 89% were detected. All Mtb were detected at a GI of > or = 100. The probes correctly identified all isolates from backup 7H9 broths. There were no false-positive probe results for any of the isolates from either BACTEC 12B or 7H9 media. Therefore, the DNA-rRNA probe test at a GI of > or = 300 saves considerable time (on average, 21 days saved) for the detection and identification of Mtb and MAC. This time saving compares with waiting for the production of colonies while retaining acceptable sensitivity and excellent specificity.

Pseudoepidemic of Nocardia asteroides associated with a mycobacterial culture system

Nocardia isolations increased from 0.7 to 11.7/1,000 acid-fast bacillus and mycological cultures (P less than 0.000001). Only three isolations from one patient represented infection. Pseudoepidemic strain identity was confirmed by DNA fingerprinting; the isolate causing infection was distinct. The end of the pseudoepidemic was associated with changing the needle sterilizer and prolonging needle sterilization time on the BACTEC 460 machine. To our knowledge, this is the first reported Nocardia asteroides pseudoepidemic.