Catherine C. McGowan

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

Abstract 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 affects 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 coll , 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 μ/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.

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 34.8 kDa 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.

Mortality during the first year of potent antiretroviral therapy in HIV-1-infected patients in 7 sites throughout Latin America and the Caribbean.

Background:Although nearly 2 million people live with HIV in Latin America and the Caribbean, mortality rates after initiation of highly active antiretroviral therapy (HAART) have not been well described. Methods:Five thousand one hundred fifty-two HIV-infected, antiretroviral-naive adults from clinics in Argentina, Brazil, Chile, Haiti, Honduras, Mexico, and Peru starting HAART during 1996-2007 were included. First-year mortality rates and their association with demographics, regimen, baseline CD4, and clinical stage were assessed. Results:Overall 1-year mortality rate was 8.3% [95% confidence interval (CI): 7.6% to 9.1%], although variable across sites: 2.6%, 3.7%, 6.0%, 13.0%, 10.8%, 3.5%, and 9.8% for clinics in Argentina, Brazil, Chile, Haiti, Honduras, Mexico, and Peru, respectively. Eighty percent of deaths occurred within the first 6 months. Median baseline CD4 was 107 cells per milliliter, ranging from 79 (Peru) to 163 (Argentina). Mortality estimates adjusting for CD4 were similar across sites (1.1%-2.8% for CD4 = 200), except for Haiti, 7.5%, and Honduras, 7.0%. Death was associated with lower CD4 [adjusted hazard ratio for CD4 = 200 vs. CD4 = 50 was 0.58; 95% CI: 0.40 to 0.85] and clinical AIDS (hazard ratio = 3.1; 95% CI: 2.1 to 4.5). Conclusions:Mortality rates were similar to those reported elsewhere for resource-limited settings. Disease stage at HAART initiation, treatment eligibility criteria, program age, and background mortality rates may explain some variability in prognosis between sites.

Immunodeficiency at the start of combination antiretroviral therapy in low-, middle- and high-income countries

Objective:To describe the CD4 cell count at the start of combination antiretroviral therapy (cART) in low-income (LIC), lower middle-income (LMIC), upper middle-income (UMIC), and high-income (HIC) countries. Methods:Patients aged 16 years or older starting cART in a clinic participating in a multicohort collaboration spanning 6 continents (International epidemiological Databases to Evaluate AIDS and ART Cohort Collaboration) were eligible. Multilevel linear regression models were adjusted for age, gender, and calendar year; missing CD4 counts were imputed. Results:In total, 379,865 patients from 9 LIC, 4 LMIC, 4 UMIC, and 6 HIC were included. In LIC, the median CD4 cell count at cART initiation increased by 83% from 80 to 145 cells/&mgr;L between 2002 and 2009. Corresponding increases in LMIC, UMIC, and HIC were from 87 to 155 cells/&mgr;L (76% increase), 88 to 135 cells/&mgr;L (53%), and 209 to 274 cells/&mgr;L (31%). In 2009, compared with LIC, median counts were 13 cells/&mgr;L [95% confidence interval (CI): −56 to +30] lower in LMIC, 22 cells/&mgr;L (−62 to +18) lower in UMIC, and 112 cells/&mgr;L (+75 to +149) higher in HIC. They were 23 cells/&mgr;L (95% CI: +18 to +28 cells/&mgr;L) higher in women than men. Median counts were 88 cells/&mgr;L (95% CI: +35 to +141 cells/&mgr;L) higher in countries with an estimated national cART coverage >80%, compared with countries with <40% coverage. Conclusions:Median CD4 cell counts at the start of cART increased 2000–2009 but remained below 200 cells/&mgr;L in LIC and MIC and below 300 cells/&mgr;L in HIC. Earlier start of cART will require substantial efforts and resources globally.

Cross-Sectional Analysis of Late HAART Initiation in Latin America and the Caribbean: Late Testers and Late Presenters

Background Starting HAART in a very advanced stage of disease is assumed to be the most prevalent form of initiation in HIV-infected subjects in developing countries. Data from Latin America and the Caribbean is still lacking. Our main objective was to determine the frequency, risk factors and trends in time for being late HAART initiator (LHI) in this region. Methodology Cross-sectional analysis from 9817 HIV-infected treatment-naïve patients initiating HAART at 6 sites (Argentina, Chile, Haiti, Honduras, Peru and Mexico) from October 1999 to July 2010. LHI had CD4+ count ≤200cells/mm3 prior to HAART. Late testers (LT) were those LHI who initiated HAART within 6 months of HIV diagnosis. Late presenters (LP) initiated after 6 months of diagnosis. Prevalence, risk factors and trends over time were analyzed. Principal Findings Among subjects starting HAART (n = 9817) who had baseline CD4+ available (n = 8515), 76% were LHI: Argentina (56%[95%CI:52–59]), Chile (80%[95%CI:77–82]), Haiti (76%[95%CI:74–77]), Honduras (91%[95%CI:87–94]), Mexico (79%[95%CI:75–83]), Peru (86%[95%CI:84–88]). The proportion of LHI statistically changed over time (except in Honduras) (p≤0.02; Honduras p = 0.7), with a tendency towards lower rates in recent years. Males had increased risk of LHI in Chile, Haiti, Peru, and in the combined site analyses (CSA). Older patients were more likely LHI in Argentina and Peru (OR 1.21 per +10-year of age, 95%CI:1.02–1.45; OR 1.20, 95%CI:1.02–1.43; respectively), but not in CSA (OR 1.07, 95%CI:0.94–1.21). Higher education was associated with decreased risk for LHI in Chile (OR 0.92 per +1-year of education, 95%CI:0.87–0.98) (similar trends in Mexico, Peru, and CSA). LHI with date of HIV-diagnosis available, 55% were LT and 45% LP. Conclusion LHI was highly prevalent in CCASAnet sites, mostly due to LT; the main risk factors associated were being male and older age. Earlier HIV-diagnosis and earlier treatment initiation are needed to maximize benefits from HAART in the region.

Rates and reasons for early change of first HAART in HIV-1-infected patients in 7 sites throughout the Caribbean and Latin America.

Background HAART rollout in Latin America and the Caribbean has increased from approximately 210,000 in 2003 to 390,000 patients in 2007, covering 62% (51%–70%) of eligible patients, with considerable variation among countries. No multi-cohort study has examined rates of and reasons for change of initial HAART in this region. Methodology Antiretroviral-naïve patients > = 18 years who started HAART between 1996 and 2007 and had at least one follow-up visit from sites in Argentina, Brazil, Chile, Haiti, Honduras, Mexico and Peru were included. Time from HAART initiation to change (stopping or switching any antiretrovirals) was estimated using Kaplan-Meier techniques. Cox proportional hazards modeled the associations between change and demographics, initial regimen, baseline CD4 count, and clinical stage. Principal Findings Of 5026 HIV-infected patients, 35% were female, median age at HAART initiation was 37 years (interquartile range [IQR], 31–44), and median CD4 count was 105 cells/uL (IQR, 38–200). Estimated probabilities of changing within 3 months and one year of HAART initiation were 16% (95% confidence interval (CI) 15–17%) and 28% (95% CI 27–29%), respectively. Efavirenz-based regimens and no clinical AIDS at HAART initiation were associated with lower risk of change (hazard ratio (HR) = 1.7 (95% CI 1.1–2.6) and 2.1 (95% CI 1.7–2.5) comparing neverapine-based regimens and other regimens to efavirenz, respectively; HR = 1.3 (95% CI 1.1–1.5) for clinical AIDS at HAART initiation). The primary reason for change among HAART initiators were adverse events (14%), death (5.7%) and failure (1.3%) with specific toxicities varying among sites. After change, most patients remained in first line regimens. Conclusions Adverse events were the leading cause for changing initial HAART. Predictors for change due to any reason were AIDS at baseline and the use of a non-efavirenz containing regimen. Differences between participant sites were observed and require further investigation.

Non-AIDS-defining events among HIV-1-infected adults receiving combination antiretroviral therapy in resource-replete versus resource-limited urban setting

Objective:To compare incidence and distribution of non-AIDS-defining events (NADEs) among HIV-1-infected adults receiving combination antiretroviral therapy (cART) in urban sub-Saharan African versus United States settings. Design:Retrospective cohort analysis of clinical trial and observational data. Methods:Compared crude and standardized (to US cohort by age and sex) NADE rates from two urban adult HIV-infected cART-initiating populations: a clinical trial cohort in Gaborone, Botswana (Botswana) and an observational cohort in Nashville, Tennessee (USA). Results:Crude NADE incidence rates were similar: 10.0 [95% confidence interval 6.3–15.9] per 1000 person-years in Botswana versus 12.4 [8.4–18.4] per 1000 person-years in the United States. However, after standardizing to an older, predominantly male US population, the overall NADE incidence rates were higher in Botswana [18.7 (8.3–33.1) per 1000 person-years]. Standardized rates differed most for cardiovascular events (8.4 versus 5.0 per 1000 person-years) and non-AIDS-defining malignancies (8.0 versus 0.5 per 1000 person-years) – both higher in Botswana. Conversely, hepatic NADE rates were higher in the United States (4.0 versus 0.0 per 1000 person-years), whereas renal NADE rates [3.0 per 1000 person-years (United States) versus 2.4 per 1000 person-years (Botswana)] were comparable. Conclusion:Crude NADE incidence rates were similar between cART-treated patients in a US observational cohort and a sub-Saharan African clinical trial. However, when standardized to the US cohort, overall NADE rates were higher in Botswana. NADEs appear to be a significant problem in our sub-Saharan African setting, and the monitoring, prevention, and treatment of NADEs should be a critical component of care in resource-limited settings.

Drug Use and Receipt of Highly Active Antiretroviral Therapy among HIV-Infected Persons in Two U.S. Clinic Cohorts

Objective Drug use and receipt of highly active antiretroviral therapy (HAART) were assessed in HIV-infected persons from the Comprehensive Care Center (CCC; Nashville, TN) and Johns Hopkins University HIV Clinic (JHU; Baltimore, MD) between 1999 and 2005. Methods Participants with and without injection drug use (IDU) history in the CCC and JHU cohorts were evaluated. Additional analysis of persons with history of IDU, non-injection drug use (NIDU), and no drug use from CCC were performed. Activity of IDU and NIDU also was assessed for the CCC cohort. HAART use and time on HAART were analyzed according to drug use category and site of care. Results 1745 persons were included from CCC: 268 (15%) with IDU history and 796 (46%) with NIDU history. 1977 persons were included from JHU: 731 (35%) with IDU history. Overall, the cohorts differed in IDU risk factor rates, age, race, sex, and time in follow-up. In multivariate analyses, IDU was associated with decreased HAART receipt overall (OR = 0.61, 95% CI: [0.45–0.84] and OR = 0.58, 95% CI: [0.46–0.73], respectively for CCC and JHU) and less time on HAART at JHU (0.70, [0.55–0.88]), but not statistically associated with time on HAART at CCC (0.78, [0.56–1.09]). NIDU was independently associated with decreased HAART receipt (0.62, [0.47–0.81]) and less time on HAART (0.66, [0.52–0.85]) at CCC. These associations were not altered significantly whether patients at CCC were categorized according to historical drug use or drug use during the study period. Conclusions Persons with IDU history from both clinic populations were less likely to receive HAART and tended to have less cumulative time on HAART. Effects of NIDU were similar to IDU at CCC. NIDU without IDU is an important contributor to HAART utilization.

Promoter analysis of Helicobacter pylori genes with enhanced expression at low pH

To identify Helicobacter pylori genes with expression that is enhanced under low pH conditions, we used subtractive hybridization methodology. We identified 28 acid‐induced genes, of which 18 have known or putative functions. Six pairs of genes were co‐transcribed. Primer extension analysis identified single or multiple transcriptional start points (tsp) for 14 of the 22 loci. Sequence analysis of the −10 regions upstream of the tsps revealed consensus motifs for multiple RNA polymerase sigma factors present in H. pylori (σ80, σ54 and σ28). No sequences resembling the −35 Escherichia coli consensus sequence (TTGACA) were present upstream of any of the genes. Both increased gene transcription and decreased mRNA decay contribute to the observed increase in H. pylori transcript abundance at acid pH. These studies document the complex response of H. pylori to environmental pH changes, and provide insight into mechanisms used for intragastric survival.

Relationship between HIV stigma and self-isolation among people living with HIV in Tennessee.

Introduction HIV stigma is a contributing factor to poor patient outcomes. Although HIV stigma has been documented, its impact on patient well-being in the southern US is not well understood. Methods Thirty-two adults participated in cognitive interviews after completing the Berger HIV or the Van Rie stigma scale. Participant responses were probed to ensure the scales accurately measured stigma and to assess the impact stigma had on behavior. Results Three main themes emerged regarding HIV stigma: (1) negative attitudes, fear of contagion, and misperceptions about transmission; (2) acts of discrimination by families, friends, health care providers, and within the workplace; and (3) participants’ use of self-isolation as a coping mechanism. Overwhelming reluctance to disclose a person’s HIV status made identifying enacted stigma with a quantitative scale difficult. Discussion Fear of discrimination resulted in participants isolating themselves from friends or experiences to avoid disclosure. Participant unwillingness to disclose their HIV status to friends and family could lead to an underestimation of enacted HIV stigma in quantitative scales.