Long-term outcomes of treatment of Mycobacterium avium complex bacteremia using a clarithromycin-containing regimen.

OBJECTIVES: To describe the long-term outcomes of treatment of AIDS-related Mycobacterium avium complex (MAC) bacteremia using a standard clarithromycin-based regimen. DESIGN: Retrospective study of patients with MAC bacteremia diagnosed between April 1992 and April 1995. SETTING: An urban AIDS clinic SUBJECTS: One hundred seventy-six consecutive patients with MAC bacteremia. INTERVENTIONS: Clarithromycin 500 mg twice daily, ethambutol 800 or 1200 mg daily, and clofazimine 100 mg daily. MAIN OUTCOME MEASURES: Late treatment failure (defined as a positive blood culture more than 90 days after starting treatment), clarithromycin susceptibility of initial and treatment-failure isolates, DNA fingerprinting of isolates from treatment failures. RESULTS: Two out of 176 (1.1%) baseline isolates were resistant to clarithromycin. One hundred and fifty-one patients were treated for MAC bacteremia, 144 (95%) with the standard regimen. Of the 117 patients who survived > 90 days after starting therapy, 25 (21%) met the criteria for late treatment failure. Of the 22 treatment-failure isolates available for susceptibility testing, 19 (86%) were resistant to clarithromycin. Therefore, 13% of patients treated using the standard regimen (19 out of 144) had treatment failure associated with the emergence of clarithromycin resistance. Using logistic regression, non-compliance was associated with treatment failure (P = 0.02). Fourteen out of the 17 (82%) evaluable paired isolates had identical DNA fingerprint patterns, whereas three pairs showed that a different strain of MAC was present at the time of treatment failure. CONCLUSIONS: Initial resistance to clarithromycin was rare during this period. However, late treatment failure associated with the emergence of clarithromycin resistance was relatively common during long-term follow-up. Most late treatment failures represented emergence of clarithromycin resistance in the initial strain.

AIDS-related Mycobacterium kansasii infection with initial resistance to clarithromycin.

Clarithromycin is a promising drug for the treatment of Mycobacterium kansasii infection. We report a patient with AIDS and severe M. kansasii infection who had previously received a short course of clarithromycin for sinusitis. He had clinical failure of treatment using clarithromycin plus ethambutol, and the initial isolate was found to be highly resistant to clarithromycin. Nucleotide sequencing of the 23S rRNA gene of this isolate demonstrated a single base mutation at position 2058, the same as that found in clarithromycin-resistant Mycobacterium avium.

Evaluation of a disk diffusion method for determining susceptibility of Mycobacterium avium complex to clarithromycin.

We evaluated an agar disk diffusion method for determining the susceptibility of Mycobacterium avium complex to clarithromycin. Isolates were inoculated onto the surface of a Middlebrook 7H11 plate, followed by the application of a 15-microgram clarithromycin disk. Zone sizes were read after 5-7 days of incubation. Zone sizes had a bimodal distribution; 40 isolates (10%) had no zone of inhibition, whereas the zone sizes for the remaining isolates ranged from 11 to 60 mm. Most isolates (37/40) having no zone of inhibition came from patients who had been treated previously with clarithromycin. Fifty-one isolates were also tested for clarithromycin susceptibility using a microdilution broth method. Defining susceptibility as a zone size of > 10 mm, disk diffusion test results agreed with the results by the microdilution broth method for 50 of 51 (98%) isolates tested by both methods. Agar disk diffusion is a promising method for the determination of clarithromycin susceptibility testing for M. avium complex.

Comparison of BACTEC 12B vs solid media for the recovery of Mycobacterium avium complex from blood cultures in AIDS patients.

We compared liquid (BACTEC 12B) and solid culture media for the diagnosis of Mycobacterium avian complex (MAC) bacteremia among 258 AIDS patients with a positive blood culture. Neither culture media alone had adequate sensitivity; BACTEC 12B detected growth earlier. Use of both liquid and solid media may improve the yield of mycobacterial blood culture.

The diagnostic yield of acid-fast-bacillus smear-positive sputum specimens.

The yield of mycobacterial culture from acid-fast-bacillus smear-positive sputum specimens was 387 or 439 (88.2%). Forty-nine of 52 culture-negative specimens came from patients on treatment. We conclude that the yield of culture from smear-positive sputum specimens is very high and that only two acid-fast-bacillus smear-positive specimens are needed for the initial evaluation of pulmonary mycobacteriosis.

The incidence of false-positive cultures for Mycobacterium tuberculosis.

The frequency of false-positive cultures for Mycobacterium tuberculosis due to cross-contamination has been difficult to determine because of the lack of specific strain markers. Isolates collected prospectively over 5 yr from a municipal health department laboratory underwent DNA fingerprinting using the IS6110 and pTBN12 sequences. We reviewed the clinical and laboratory records of all isolates that had matching DNA fingerprints and were processed within 42 d of each other; 8 isolates were classified as probable or definite false-positives, representing 4.0% (8/199) of the culture-positive patients. A convenience sample of 42 isolates from three other mycobacterial laboratories also underwent DNA fingerprinting, and five (12%) were found to be definite or probable false-positives. Cross-contamination during initial processing of specimens was the most common source of false-positive cultures. The source of cross-contamination for three false-positive cultures was a laboratory proficiency survey specimen containing strain H37Ra. Ten of the 13 patients were misdiagnosed as having tuberculosis, and seven received unnecessary multidrug treatment. Clinicians should be aware of the potential for false-positive cultures for M. tuberculosis, and mycobacteriology laboratories need to carefully review procedures to minimize this occurrence. DNA fingerprinting provides a valuable tool for the study of false-positive cultures.

Prolonged incubation of blood and bone marrow cultures in 12B bottles processed on the BACTEC 460 TB system does not increase microbial recovery.

Standard references continue to recommend testing specimens processed on the BACTEC TB System for 8 weeks, despite evidence that mycobacteria are rarely recovered beyond 5-6 weeks. To clarify this issue, we retrospectively reviewed all positive blood/bone marrow cultures processed during a 17-month period when specimens were tested for 6 weeks. We then prolonged the incubation period to 8 weeks during the subsequent 5 months. Excluding Mycobacterium genavense, only 1 of 159 mycobacterial isolates was recovered during and none were recovered beyond the 5th week of incubation and testing on the BACTEC TB System.

Comparison of recovery rates for mycobacteria from BACTEC 12B vials, Middlebrook 7H11-selective 7H11 biplates, and Lowenstein Jensen slants in a public health mycobacteriology laboratory.

Recovery rates from Middlebrook 7H11-selective 7H11 biplates and Lowenstein-Jensen slants (LJ) used with BACTEC 12B vials were compared for 5,399 specimens. For 578 specimens that were inoculated onto three media, 580 mycobacteria were isolated, including 277 (48%) Mycobacterium avium complex isolates, 230 (40%) Mycobacterium tuberculosis isolates, and 73 (12%) other mycobacteria. For BACTEC 12B vials, 506 (87%) cultures were positive, 45 (8%) were negative, and 29 (5%) were lost to contamination; for 7H11-7H11-selective biplates, 469 (81%) cultures were positive, 95 (16%) were negative, and 16 (3%) were lost to contamination; for LJ, 230 (40%) cultures were positive, 111 (19%) were negative, and 239 (41%) were lost to contamination. For routine cultures, use of plate media is superior to use of LJ.

Utility of paired blood cultures and smears in diagnosis of disseminated Mycobacterium avium complex infections in AIDS patients.

For 273 patients evaluated for disseminated Mycobacterium avium complex infection, a total of 1,047 mycobacterial blood cultures (MBCs) were submitted; the M. avium complex was recovered from 140 (13%) of the specimens. Results for the paired MBCs were highly concordant: in 392 of 462 (85%) culture sets, both MBCs were negative, in 53 of 462 (11%) sets, both MBCs were positive, and in only 17 of 462 (4%) sets was one culture positive and the other negative. Acid-fast smears were done on sediments from 671 specimens; smears were positive for 4 of 98 (4%) cultures that grew the M. avium complex. A single MBC should be obtained and then repeated if negative and disseminated M. avium complex infection is still clinically suspected. Use of direct acid-fast smears of sediments is not a reliable means of detecting mycobacteremia.

The Drosophila 78C early late puff contains E78, an ecdysone-inducible gene that encodes a novel member of the nuclear hormone receptor superfamily.

We report the molecular definition of an early late puff locus, at position 78C, that is inducible by ecdysone at the onset of Drosophila metamorphosis. This puff contains a single ecdysone-inducible gene consisting of two nested transcription units, E78A and E78B. E78A mRNA is expressed during a brief interval in mid-pupal development and encodes a novel member of the nuclear hormone receptor superfamily. E78B encodes a truncated receptor isoform that lacks the DNA-binding domain and is predominantly expressed at puparium formation and immediately following E78A in pupae. E78B is directly inducible by ecdysone in late third instar larvae and depends on ecdysone-induced protein synthesis for its maximal level of expression. These observations indicate that E78 represents a distinct subset of early ecdysone-inducible regulatory genes.

Creativity and schizotypal traits. Creativity test scores and perceptual aberration, magical ideation, and impulsive nonconformity.

Using a nonclinical and noneminent population, this study demonstrates an overlap in creative and schizotypal traits in the areas of perceptual functioning, behavioral and personality styles, and interests. No such overlap is observed in the area of divergent thinking. A battery containing five creativity measures was administered to a group of college student subjects scoring high on either the Perceptual Aberration Scale or the Magical Ideation Scale (N = 52) and to a group of control subjects (N = 65). A multivariate analysis of variance indicated that subjects high on the schizotypal traits of Perceptual Aberration or Magical Ideation (Per-Mag subjects) differed significantly from control subjects on the five creativity tests. Per-Mag subjects scored significantly higher than control subjects on the Barron-Welsh Revised Art Scale, a measure of preferences for figures, and the How Do You Think, a biographical and personality measure. There was a tendency for female Per-Mag subjects to score higher than female control subjects on the Domino Creativity Scale of the Adjective Check List. Per-Mag and control subjects did not differ on the Gough Creative Personality Scale of the Adjective Check List or on the Alternate Uses test, a test of divergent thinking. Per-Mag subjects who scored above the median for their group and gender on the Impulsive Nonconformity Scale received the highest creativity scores on the Barron-Welsh Revised Art Scale and the How Do You Think, although these results only approached significance. These findings argue for the specificity of areas of similarity and difference in schizotypy and creativity.

Conotoxin GI: disulfide bridges, synthesis, and preparation of iodinated derivatives.

The 13 amino acid toxic peptide from the marine snail Conus geographus, conotoxin GI, blocks the acetylcholine receptor at the neuromuscular junction. In this report, we describe a method for analyzing disulfide bonding in nanomole amounts of small cystine-rich peptides. The procedure involves partial reduction and a double-label alkylation of cysteine residues. Using this method, we show that the natural conotoxin GI has a (2-7, 3-13) disulfide configuration. The structure of conotoxin GI has been confirmed by chemical synthesis. The preparation and purification of molecularly homogeneous, iodinated derivatives of this toxin are also described. All derivatives, including the [diiodohistidine,diiodotyrosine]conotoxin GI, retained at least half of the biological activity of unmodified toxin. Since the tetraiodinated toxin, which is greater than 25% by weight iodine, retains considerable toxicity, unmodified histidine and tyrosine residues in conotoxin GI are not crucial for biological activity.