HIV-related tuberculosis: mortality risk in persons without vs. with culture-confirmed disease.

BACKGROUND: Tuberculosis (TB) diagnosis in human immunodeficiency virus (HIV) positive persons is difficult, particularly in resource-limited settings. The relationship between TB culture status and mortality in HIV-positive persons treated for TB is unclear. METHODS: We evaluated HIV-positive adults treated for TB at or after their first HIV clinic visit in Argentina, Brazil, Chile, Honduras, Mexico or Peru from 2000 to 2015. Anti-tuberculosis treatment included 2 months of isoniazid, rifampicin (RMP)/rifabutin (RBT), pyrazinamide ± ethambutol, followed by continuation phase treatment with isoniazid + RMP/RBT. RESULTS: Of 759 TB-HIV patients, 238 (31%) were culture-negative, 228 (30%) had unknown culture status or did not undergo culture and 293 (39%) were culture-positive. The median CD4 at TB diagnosis was 96 (interquartile range 40-228); 636 (84%) received concurrent antiretroviral therapy (ART) and anti-tuberculosis treatment. There were 123 (16%) deaths: 90/466 (19%) with TB culture-negative, unknown or not performed vs. 33/293 (11%) who were TB culture-positive (P = 0.005). In Kaplan-Meier analysis, mortality in TB patients without culture-confirmed disease was higher (P = 0.002). In a Cox model adjusted for age, sex, CD4, ART timing, disease site and stratified by study site, mortality in persons without culture-confirmed TB was not significantly increased compared to those with culture-positive TB (hazard ratio 1.39, 95%CI 0.89-2.16, P = 0.15). CONCLUSION: Most HIV-positive patients treated for TB did not have culture-confirmed TB, and mortality tended to be higher in patients without culture-confirmed disease, although the association was not statistically different after adjusting for other variables. Accurate TB diagnosis in HIV-positive persons is crucial.

Outcomes of HIV-positive patients with cryptococcal meningitis in the Americas.

BACKGROUND: Cryptococcal meningitis (CM) is associated with substantial mortality in HIV-infected patients. Optimal timing of antiretroviral therapy (ART) in persons with CM represents a clinical challenge, and the burden of CM in Latin America has not been well described. Studies suggest that early ART initiation is associated with higher mortality, but data from the Americas are scarce. METHODS: HIV-infected adults in care between 1985-2014 at participating sites in the Latin America (the Caribbean, Central and South America network (CCASAnet)) and the Vanderbilt Comprehensive Care Clinic (VCCC) and who had CM were included. Survival probabilities were estimated. Risk of death when initiating ART within the first 2 weeks after CM diagnosis versus initiating between 2-8 weeks was assessed using dynamic marginal structural models adjusting for site, age, sex, year of CM, CD4 count, and route of HIV transmission. FINDINGS: 340 patients were included (Argentina 58, Brazil 138, Chile 28, Honduras 27, Mexico 34, VCCC 55) and 142 (42%) died during the observation period. Among 151 patients with CM prior to ART 56 (37%) patients died compared to 86 (45%) of 189 with CM after ART initiation (p=0.14). Patients diagnosed with CM after ART had a higher risk of death (p=0.03, log-rank test). The probability of survival was not statistically different between patients who started ART within 2 weeks of CM (7/24, 29%) vs. those initiating between 2-8 weeks (14/53, 26%) (p=0.96), potentially due to lack of power. INTERPRETATION: In this large Latin-American cohort, patients with CM had very high mortality rates, especially those diagnosed after ART initiation. This study reflects the overwhelming burden of CM in HIV-infected patients in Latin America.

Ring and peg electrodes for minimally-Invasive and long-term sub-scalp EEG recordings.

OBJECTIVE: Minimally-invasive approaches are needed for long-term reliable Electroencephalography (EEG) recordings to assist with epilepsy diagnosis, investigation and more naturalistic monitoring. This study compared three methods for long-term implantation of sub-scalp EEG electrodes. METHODS: Three types of electrodes (disk, ring, and peg) were fabricated from biocompatible materials and implanted under the scalp in five ambulatory ewes for 3months. Disk electrodes were inserted into sub-pericranial pockets. Ring electrodes were tunneled under the scalp. Peg electrodes were inserted into the skull, close to the dura. EEG was continuously monitored wirelessly. High resolution CT imaging, histopathology, and impedance measurements were used to assess the status of the electrodes at the end of the study. RESULTS: EEG amplitude was larger in the peg compared with the disk and ring electrodes (p<0.05). Similarly, chewing artifacts were lower in the peg electrodes (p<0.05). Electrode impedance increased after long-term implantation particularly for those within the bone (p<0.01). Micro-CT scans indicated that all electrodes stayed within the sub-scalp layers. All pegs remained within the burr holes as implanted with no evidence of extrusion. Eight of 10 disks partially eroded into the bone by 1.0mm from the surface of the skull. The ring arrays remained within the sub-scalp layers close to implantation site. Histology revealed that the electrodes were encapsulated in a thin fibrous tissue adjacent to the pericranium. Overlying this was a loose connective layer and scalp. Erosion into the bone occurred under the rim of the sub-pericranial disk electrodes. CONCLUSIONS: The results indicate that the peg electrodes provided high quality EEG, mechanical stability, and lower chewing artifact. Whereas, ring electrode arrays tunneled under the scalp enable minimal surgical techniques to be used for implantation and removal.

Detection and management of drug-resistant tuberculosis in HIV-infected patients in lower-income countries.

SETTING: Drug resistance threatens tuberculosis (TB) control, particularly among human immunodeficiency virus (HIV) infected persons. OBJECTIVE: To describe practices in the prevention and management of drug-resistant TB under antiretroviral therapy (ART) programs in lower-income countries. DESIGN: We used online questionnaires to collect program-level data on 47 ART programs in Southern Africa (n = 14), East Africa (n = 8), West Africa (n = 7), Central Africa (n = 5), Latin America (n = 7) and the Asia-Pacific (n = 6 programs) in 2012. Patient-level data were collected on 1002 adult TB patients seen at 40 of the participating ART programs. RESULTS: Phenotypic drug susceptibility testing (DST) was available in 36 (77%) ART programs, but was only used for 22% of all TB patients. Molecular DST was available in 33 (70%) programs and was used in 23% of all TB patients. Twenty ART programs (43%) provided directly observed therapy (DOT) during the entire course of treatment, 16 (34%) during the intensive phase only, and 11 (23%) did not follow DOT. Fourteen (30%) ART programs reported no access to second-line anti-tuberculosis regimens; 18 (38%) reported TB drug shortages. CONCLUSIONS: Capacity to diagnose and treat drug-resistant TB was limited across ART programs in lower-income countries. DOT was not always implemented and drug supplies were regularly interrupted, which may contribute to the global emergence of drug resistance.

Acid-induced expression of an LPS-associated gene in Helicobacter pylori.

To investigate urease-independent mechanisms by which Helicobacter pylori resists acid stress, subtractive RNA hybridization was used to identify H. pylori genes whose expression is induced after exposure to acid pH. This approach led to the isolation of a gene that encoded a predicted 34.8kDa protein (WbcJ), which was homologous to known bacterial O-antigen biosynthesis proteins involved in the conversion of GDP-mannose to GDP-fucose. An isogenic wbcJ null mutant strain failed to express O-antigen and Lewis X or Lewis Y determinants and was more sensitive to acid stress than was the wild-type strain. Qualitative differences in LPS profiles were observed in H. pylori cells grown at pH 5 compared with pH 7, which suggests that H. pylori may alter its LPS structure in response to acidic pH. This may be an important adaptation facilitating H. pylori colonization of the acidic gastric environment.

Analysis of F1F0-ATPase from Helicobacter pylori.

The adaptive mechanisms that permit Helicobacter species to survive within the gastric mucosa are not well understood. The proton-translocating F1F0-ATPase is an important enzyme for regulating intracellular pH or synthesizing ATP in many other enteric bacteria; therefore, we used degenerate primers derived from conserved bacterial F1F0-ATPase sequences to PCR amplify and clone the gene (atpD) encoding the H. pylori F1F0-ATPase beta subunit. The deduced amino acid sequences of the F1F0-ATPase beta subunits from H. pylori and Wolinella succinogenes were 85% identical (91% similar). To characterize a potential functional role of F1F0-ATPase in H. pylori, H. pylori or Escherichia coli cells were incubated for 60 min in buffered solutions at pH 7, 6, 5, or 4, with or without 100 microM N,N'-dicyclohexylcarbodiimide (DCCD), a specific inhibitor of F1F0-ATPase. At pH 5 and 4, there was no significant decrease in survival of H. pylori in the presence of DCCD compared to its absence, whereas incubation with DCCD at pH 7 and 6 significantly decreased H. pylori survival. E. coli survival was unaffected by DCCD at any pH value tested. We next disrupted the cloned beta-subunit sequence in E. coli by insertion of a kanamycin resistance cassette and sought to construct an isogenic F1F0-ATPase H. pylori mutant by natural transformation and allelic exchange. In multiple transformations of H. pylori cells grown at pH 6 or 7, no kanamycin-resistant F1F0 mutants were isolated, despite consistently successful mutagenesis of other H. pylori genes by using a similar approach and PCR experiments providing evidence for integration of the kanamycin resistance cassette into atpD. The sensitivity of H. pylori to DCCD at pH 7 and 6, and failure to recover F1F0 H. pylori mutants under similar conditions, suggests that the function of this enzyme is required for survival of H. pylori at these pHs.

Helicobacter pylori and gastric acid: biological and therapeutic implications.

Helicobacter pylori is highly adapted to its unusual ecological niche in the human stomach. Urease activity permits H. pylori survival at a pH of <4 in vitro and is required for the organism to colonize in animal models. However, urease does not play an important role in the survival of the organism in a pH range between 4 and 7. Other mechanisms of pH homeostasis remain poorly understood, but preliminary studies indicate that novel proteins are produced when H.pylori cells are shifted from pH 7 to 3, and the gene encoding a P-type adenosine triphosphatase that may catalyze NH4+/H+ exchange across the cytoplasmic membrane has been cloned. Mechanisms of pH homeostasis in other enteric bacteria are reviewed and provide insight into additional pathways that may be used by H. pylori. An important adaptation of H. pylori to the gastric environment may be its ability to alter gastric acid secretion. Acute infection is associated with transient hypochlorhydria, whereas chronic infection is associated with hypergastrinemia and decreased somatostatin levels. Thus, the survival of H. pylori in the gastric environment may be attributed to both the development of specialized intrinsic defenses and the organism's ability to induce physiological alterations in the host environment.

The proton pump inhibitor omeprazole inhibits acid survival of Helicobacter pylori by a urease-independent mechanism.

BACKGROUND/AIMS: Omeprazole, a benzimidazole proton pump inhibitor, has an antibacterial effect against Helicobacter pylori at neutral pH and inhibits its urease activity. The aim of this study was to characterize H. pylori acid resistance and to determine whether omeprazole effects its survival at low pH. METHODS: We studied survival of H. pylori and other enteric organisms in buffered solutions (pH 2-7) in the presence or absence of 10 mmol/L urea and/or omeprazole. RESULTS: In the absence of urea, the acid tolerances of wild-type H. pylori, a urease-negative H. pylori mutant, Escherichia coli, and Proteus mirabilis were similar. In the presence of urea, the survival of the wild-type H. pylori at pH 2 was significantly greater than that of the other organisms. Omeprazole (100 micrograms/mL) had a marked inhibitory effect on the survival of both wild-type and urease-negative H. pylori at low pH, and similar effects on E. coli, P. mirabilis, and Salmonella typhimurium. CONCLUSIONS: Whereas survival of H. pylori below pH 4 is urease dependent, H. pylori uses non-urease-mediated mechanisms at or above pH 4. Omeprazole inhibits the survival of H. pylori at low pH through a mechanism independent of its effect on urease, an antibacterial effect that extends to other enteric bacteria.