Evidence from molecular fingerprinting of limited spread of drug-resistant tuberculosis in Texas.

To determine the contribution of recent transmission to spread of drug-resistant tuberculosis in Texas, we performed IS6110-based and pTBN12-based restriction fragment length polymorphism (RFLP) analyses on Mycobacterium tuberculosis isolates. Isolates collected from 201 patients in Texas between 1992 and 1994 were studied. The distribution of cases was strikingly focal. All cases were reported from 35 of the 254 counties in Texas, and 74% (148 of 201) were reported from only 9 counties. One hundred sixty-one (80%) of the patients had M. tuberculosis isolates with unique RFLP patterns, and 41 (20%) patients were in 20 clusters, each comprising 2 to 3 patients. The largest number of cases of drug-resistant tuberculosis were reported in counties bordering Mexico, but the percentage of clustered cases was highest in northeast Texas and in counties that included the cities of Dallas, Fort Worth, and Houston. Compared to nonclustered patients, clustered patients were more likely to be African American and to have been born in the United States. Clustered patients were significantly more likely to be from the same geographic area, and clustered patients from the same geographic area were more likely to have isolates with identical drug susceptibility patterns, suggesting that they were linked by recent transmission. In 11 of 20 clusters, clustered patients were from geographically separate regions, and most isolates did not have identical drug susceptibility patterns, suggesting that tuberculosis was contracted from a common source in the remote past. Based on the low percentage of clustered cases and the small cluster size, we conclude that there is no evidence for the extensive transmission of drug-resistant tuberculosis in Texas.

Multicenter evaluation of the BACTEC MGIT 960 system for recovery of mycobacteria.

We evaluated the BACTEC MGIT 960 system, which is a fully automated, noninvasive system for the growth and detection of mycobacteria with a capacity to incubate and continuously monitor 960 7-ml culture tubes. We studied 3,330 specimens, 2,210 respiratory and 1,120 nonrespiratory specimens, collected from 2,346 patients treated at six sites. Processed specimens were inoculated into the BACTEC MGIT 960 and BACTEC 460 TB systems, as well as onto Lowenstein-Jensen slants and Middlebrook 7H11/7H11 selective plates. From all culture systems, a total of 362 isolates of mycobacteria were recovered; these were recovered from 353 specimens collected from 247 patients. The greatest number of isolates of mycobacteria (289, or 80% of the 362 isolates) was recovered with the BACTEC MGIT 960, followed by the BACTEC 460 TB (271, or 75%) and solid media (250, or 69%). From all culture systems a total of 132 isolates of Mycobacterium tuberculosis complex were recovered. The greatest number of isolates of M. tuberculosis complex was recovered when liquid medium was combined with conventional solid media; the number recovered with BACTEC 460 TB plus solid media was 128 (97%), that recovered with BACTEC MGIT 960 plus solid media was 121 (92%), that recovered with BACTEC 460 TB was 119 (90%) and that recovered with all solid media combined was 105 (79%). The recovery with BACTEC MGIT 960 alone was 102 (77%). The mean times to detection (TTD) for M. tuberculosis complex were 14.4 days for BACTEC MGIT, 15.2 days for BACTEC 460 TB, and 24.1 days for solid media. The numbers of isolates of Mycobacterium avium complex (MAC) recovered were 172 (100%) for all systems, 147 (85%) for BACTEC MGIT 960, 123 (72%) for BACTEC 460 TB, and 106 (62%) for all solid media combined. The TTD for MAC in each system were 10.0 days for BACTEC MGIT 960, 10.4 days for BACTEC 460 TB, and 25.9 days for solid media. Breakthrough contamination rates (percentages of isolates) for each of the systems were 8.1% for BACTEC MGIT 960, 4.9% for BACTEC 460 TB, and 21.1% for all solid media combined.

Identification of Mycobacterium tuberculosis and M. avium complex directly from smear-positive sputum specimens and BACTEC 12B cultures by high-performance liquid chromatography with fluorescence detection and computer-driven pattern recognition models.

A high-performance liquid chromatography method that utilized fluorescence detection (HPLC-FL) of mycolic acid 6,7-dimethoxycoumarin esters was developed to identify Mycobacterium tuberculosis (MTB) and M. avium complex (MAC) directly from fluorochrome stain smear-positive sputum specimens and young BACTEC 12B cultures. HPLC-FL chromatograms from a training set that included 202 smear-positive clinical sputum specimens and 343 mycobacterial cultures were used to construct a calibrated peak-naming table and computer-based pattern recognition models for MTB and MAC. Pattern recognition model performance was measured with an evaluation set of samples that included 251 smear-positive clinical sputum specimens and 167 BACTEC 12B cultures. Evaluation sputum specimens were culture positive for MTB (n = 132) and MAC (n = 48). With evaluation sputa, the MTB and MAC models were 56.8 and 33.3% sensitive, respectively. Evaluation set BACTEC 12B cultures were culture positive for MTB (n = 97) and MAC (n = 53). The sensitivities of the MTB and MAC models for identification of BACTEC 12B cultures were 99.0 and 94.3%, respectively. The specificity of both models was 100% for both types of evaluation samples. The average times from BACTEC 12B inoculation to cell harvest were 10.2 and 7.4 days for MTB and MAC, respectively. HPLC-FL can identify MTB and MAC in 1 day from many smear-positive sputa. Rapid and sensitive identification of MTB and MAC from young BACTEC 12B cultures was achieved.

Rickettsia in Texas.

Since the first reported case in 1941, Rocky Mountain spotted fever in humans has been reported from many areas of Texas, with two major foci, one located in the north-central region and the other in the eastern region of the state. During the period 1979-1988, 421 cases of RMSF were reported, reaching 108 cases in 1983 and declining in subsequent years. Statewide surveillance programs to detect spotted fever group rickettsiae in tick populations were initiated in 1976. In recent years, the SFG infectivity rates in these tick species have included Dermacentor variabilis, 5.2%; Amblyomma americanum, 7.1%; Rhipicephalus sanguineus, 2.9%; and Ixodes scapularis, 10.2%. Further determination of involved rickettsial species and pathogenicity is needed, as many of these specimens are collected from humans and during epidemiological investigations. Various foci of murine typhus occur in Texas. During 1979-1988, 400 human cases were reported. The majority of cases occurred in people who resided in south Texas. Several investigations have shown a possible link between typhus infections and exposure to Ctenocephalides felis. Other rickettsial infections currently reported in Texas include Q fever and ehrlichiosis.

Cross-reaction of immune sera from patients with rickettsial diseases.

Rickettsia rickettsii and Rickettsia conorii are the causative agents of two common and serious diseases, Rocky Mountain spotted fever and Mediterranean spotted fever, respectively. In patients naturally infected with either of these organisms, antibodies are produced which cross-react with antigens of the other so extensively that diagnostic tests usually cannot identify the causative agents. The results of this study indicate that serodiagnostic tests with antigen from one of these two organisms could be used to detect antibodies in patients with either of the two rickettsial diseases.

Comparison of a latex agglutination procedure with the microimmunofluorescence test for Rickettsia typhi.

Sera submitted to the Texas Department of Health for the serodiagnosis of Rickettsia typhi were tested by the microimmunofluorescent antibody technique and a new latex agglutination procedure. Results indicated that the latex agglutination test was sensitive and specific and would serve well as a first-line screening test for murine typhus.

Comparative evaluation of commercial rubella virus antibody kits.

Comparative evaluation of six commercial rubella virus antibody kits is described. A set of serum samples skewed toward nonreactive and low-positive rubella antibody levels was used because the goal of an immunity screening test is the detection of susceptible individuals. The M. A. Bioproducts Rubastat and the Hynson, Westcott and Dunning Rubascan were superior in achieving high sensitivity, specificity, and reproducibility. They also were the easiest and fastest tests to perform, and they require equipment available in most laboratories.

Evaluation of latex-Rickettsia rickettsii test for Rocky Mountain spotted fever in 11 laboratories.

A latex-Rickettsia rickettsii test for detection of antibodies to Rocky Mountain spotted fever (RMSF) was evaluated during the 1980 RMSF season in 11 laboratories in nine states where the disease is endemic. In a double-blind study, all sera submitted to each laboratory for RMSF testing were also examined by the latex-R. rickettsii test. A portion of each specimen was then sent to the New York State laboratory for testing by latex-R. rickettsii and by the reference microimmunofluorescence test. Results were exchanged at the end of the examination period. At the usual ratio of reactive to nonreactive sera encountered in a diagnostic laboratory on a day-to-day basis, the efficiency of the latex-R. rickettsii test relative to microimmunofluorescence was 96.79% for New York and 93.30% for the collaborating laboratories. Both the latex and microimmunofluorescence tests detected antibodies to RMSF within 7 to 9 days of onset. With the latex-R. rickettsii test--but not necessarily with microimmunofluorescence--a high titer (greater than or equal to 128) on a single serum was diagnostic of active RMSF. Changes in serum titer for patients with multiple sera were similar for both tests. The test detects rickettsial antibodies in patients with active infection, but in most cases it does not detect antibody in patients with past infection. Test reactivity could not be uniquely linked to a particular immunoglobulin class.

Comparison of an enzyme-linked immunosorbent assay with indirect hemagglutination and hemagglutination inhibition for determination of rubella virus antibody: evaluation of immune status with commercial reagents in a clinical laboratory.

Comparative evaluations of immune status for rubella virus are described for enzyme-linked immunosorbent assay, hemagglutination inhibition, and indirect hemagglutination. A 92.1% agreement between enzyme-linked immunosorbent assay and indirect hemagglutination assay was demonstrated for rubella immune status. Enzyme-linked immunosorbent assay and hemagglutination inhibition demonstrated a 92.6% agreement and were compared in an attempt to define the quantitative usefulness of comparisons of single sera for determining immune status. These data support the relative lack of correlation between single enzyme-linked immunosorbent assay and hemagglutination inhibition quantitative values. Enzyme immunoassay was, however, an acceptable alternative to hemagglutination inhibition for the determination of immune status to rubella virus.

Reintroduction of dengue fever into the continental United States. I. Dengue surveillance in Texas, 1980.

Two surveillance systems were initiated in Texas in 1980 to detect cases of dengue fever. Physicians throughout the state were requested to report cases of dengue (passive surveillance), and 27 out-patient facilities serving geographically and ethnically high risk populations were asked to report cases of dengue-like illness weekly (active surveillance). Additionally, two clinics participating in active surveillance submitted acute-phase blood specimens weekly for dengue virus isolation. Sixty-three cases of illness due to dengue type 1 infection (dates of onset 2 August-10 November) were documented by virus isolation or serologic testing; 52 of them (83%) occurred n countries adjacent to the Texas-Mexico border. Fifty-six patients (89%) were Hispanic; 46 (73%) were females. Twenty-seven patients (43%) had not traveled outside the U.S. before becoming ill. Since no clinically apparent outbreak of dengue was ever recognized by public health officials in Texas in 1980, the active surveillance system in other Gulf Coast states should be considered when the risk of introduction of dengue is considered high.

Detection of typhus antibodies by latex agglutination.

A latex test for assay of antibodies to endemic and epidemic typhus rickettsiae is simple, group-specific, sensitive, and reproducible. Cross-reactivity within the typhus group was extensive.