Underwent Resistance Testing Research Articles

A Multicenter Evaluation of Clopidogrel Resistance and Its Role in Predicting Stent Thrombosis in Transcarotid Artery Revascularization

OBJECTIVEClopidogrel resistance testing is not routine prior to Transcarotid Artery Revascularization (TCAR) and resistance rates are not well described in this setting, despite frequent use of periprocedural clopidogrel. We compared two resistance testing modalities to determine the relationship between resistance and stent outcomes. METHODSConsecutive patients undergoing TCAR at three institutions were retrospectively identified. Clopidogrel-resistance testing results and outcomes were described. RESULTSA total of 210 patients underwent TCAR from 2018-2022. 154 (73%) were on dual antiplatelet therapy (DAPT) for at least 7 days prior to TCAR. Twenty-nine patients were not on DAPT due to therapeutic anticoagulation and most (38/56, 68%) received a loading dose of a second antiplatelet the day of surgery. Twenty-five patients (11.9%) experienced stent thrombosis within 30 days. Patients not on DAPT for at least 7 days prior to surgery were more prone to stent thrombosis (16.7% vs 10.4%, p=.164). Over half (133/210, 63%) of patients underwent resistance testing, 25 with thromboelastogram with platelet mapping (TEG-PM), 103 with VerifyNow P2Y12 platelet reactivity assay, and 5 with both. Prevalence of Clopidogrel resistance among tested patients was 41%. In patients tested using both TEG-PM and VerifyNow, agreement was poor (Cohen’s Kappa -0.05). Among patients with resistance, 12 (22%) experienced stent thrombosis. Comparatively, 8 (10%) patients without resistance developed thrombosis (p=.021). VerifyNow P2Y12 platelet reactivity assay correctly predicted Clopidogrel-resistance more accurately than TEG-PM (70% versus 40%, p=.025) and had sensitivity of 56% and specificity of 73% for stent thrombosis. CONCLUSIONOur multi-institutional cohort confirms a high rate of Clopidogrel resistance in patients undergoing TCAR, with higher acute stent thrombosis rates noted in patients with resistance. VerifyNow P2Y12 platelet reactivity assays more reliably predict Clopidogrel resistance than TEG-PM.

In-silico insights of ESBL variants and tracking the probable sources of ESBL-producing Escherichia coli in a small-scale poultry farm

Commercial broiler farms face challenges of extended spectrum beta-lactamase (ESBL)-producing Escherichia coli transmitted from both vertical and horizontal routes. Understanding the dynamics of ESBL-E. coli transmission in compromised biosecurity settings of small-scale rural poultry farms is essential. This study aimed to elucidate the probable transmission pathways of ESBL-E. coli in such settings, employing phylogenetic analysis and molecular docking simulations to explore the catalytic properties of β-lactamase variants. Sampling was conducted on a small-scale poultry farm in West Bengal, India, collecting 120 samples at three intervals during the broiler production cycle. E. coli isolates underwent resistance testing against eight antimicrobials, with confirmation of ESBL production. Genotypic analysis of ESBL genes and sequencing were performed, alongside molecular docking analyses and phylogenetic comparisons with publicly available sequences. Among 173 E. coli isolates, varying resistance profiles were observed, with complete resistance to cefixime and high resistance to amoxicillin and tetracycline. The incidence of ESBL-E. coli fluctuated over the production cycle, with dynamic changes in the prevalence of blaCTX-M-type and blaSHV-type genes. Phylogenetic analysis indicated partial clonal relationships with human clinical strains and poultry strains from the Indian subcontinent. Molecular docking confirmed the catalytic efficiencies of these ESBL variants. The study highlights probable vertical transmission of ESBL-E. coli and emphasizes drinking water as a potential source of horizontal transmission in small-scale poultry farms. Strict biosecurity measures could prevent the spread of antimicrobial-resistant bacteria in birds and their products in a small scale poultry farm.

Comparing albuvirtide plus ritonavir-boosted lopinavir regimen to two nucleotide reverse transcriptase inhibitors plus ritonavir-boosted lopinavir in HIV-infected individuals who failed initial treatment: a retrospective comparative cohort study.

Albuvirtide (ABT), a fusion inhibitor against human immunodeficiency virus (HIV) infection, has good efficacy and tolerability for HIV treatment. However, there is a paucity of data regarding ABT-based regimen as second-line therapy. This current study evaluated the efficacy and safety of switching to ABT + ritonavir-boosted lopinavir (LPV/r) treatment in a cohort of HIV-infected individuals who failed initial treatment. This retrospective comparative cohort study included patients who failed initial treatment and switched to either ABT + LPV/r (the ABT group) or two nucleotide reverse transcriptase inhibitors (NRTIs) + LPV/r (the NRTI group) between November 2019 and December 2020 in the People's Hospital of Zhaojue County in Liangshan Yi Autonomous Prefecture, China. All individuals were followed up from baseline to 12 weeks after conversion, or until the patient developed unacceptable toxic effects or was loss of follow-up. The proportion of patients who achieved virological suppression (viral load <50 copies/mL) at week 12 was considered a primary efficacy endpoint. Safety outcomes included the incidence of adverse events and laboratory abnormalities. All participants underwent resistance testing before regimen conversion. The linear regression model was applied to evaluate the association of CD4+ T cell count with the patient's clinical characteristics. A total of 71 patients were included in this study, the two groups were comparable at baseline in terms of age, sex, CD4+ T cell count, and viral load. The suppression of HIV-1 RNA to levels <50 copies/mL was achieved in 82.4% (28/31) and 29.7% (11/34) of patients in the ABT group and the NRTI group, respectively (P<0.001). Older age (P=0.016) and higher alkaline phosphatase (ALP) levels (P=0.038), but not rescue regimen, were associated with attenuated CD4+ T cell recovery. Most adverse events mild in severity, with abdominal pain as the most reported event in two groups (26.8%, 19/71), and no severe adverse events were detected. Conversion to ABT + LPV/r therapy appears to be an effective and safe strategy. This treatment regimen has great potential to be generalized in the HIV-infected population, although further testing in a larger patient population is required to verify these results.

Safety and effectiveness of switching to Abacavir/Lamivudine plus rilpivirine for maintenance therapy in virologically suppressed HIV-1 individuals in Singapore (SEALS)

BackgroundThe efficacy and tolerability of an antiretroviral regimen are important considerations for selection of HIV-1 infection maintenance therapy. Abacavir/lamivudine plus rilpivirine (ABC/3TC + RPV) has been shown in international studies to be effective and well-tolerated in virologically suppressed individuals. This study evaluated the effectiveness and safety of switching to ABC/3TC + RPV as maintenance therapy in virologically suppressed HIV-1 infected individuals in Singapore.MethodsIn this retrospective, single-centre study, we included individuals who were prescribed ABC/3TC + RPV, had HIV-1 viral load (VL) < 50 copies/ml immediately pre-switch, and had no documented history of resistance mutations or virologic failure to any of the components. The follow-up period was 48 ± 12 weeks. The primary outcome was the proportion of individuals who maintained virologic suppression of HIV-1 VL < 50 copies/ml at the end of follow-up period based on on-treatment analysis. The secondary outcomes were the resistance profiles associated with virologic failure, changes in immunologic and metabolic parameters, and the safety profile of ABC/3TC + RPV.ResultsA total of 222 individuals were included in the study. The primary outcome was achieved in 197 individuals [88.8%, 95% confidence interval: 83.7–92.4%]. There were 21 individuals (9.5%) who discontinued treatment for non-virologic reasons. The remaining 4 individuals experienced virologic failure, of whom, 3 of these individuals had developed emergent antiretroviral resistance and had HIV-1 VL > 500 copies/ml at the end of the 48 ± 12 weeks follow-up period. The remaining individual experienced sustained low level viremia and subsequently achieved viral suppression without undergoing resistance testing. A total of 49 adverse events were observed in 31 out of 222 individuals (14.0%), which led to 13 individuals discontinuing therapy. Neuropsychiatric adverse events were most commonly observed (53.1%). A statistically significant increase in CD4 was observed (p < 0.01), with a median absolute change of 31 cells/uL (interquartile range: − 31.50 to 140.75). No significant changes in lipid profiles were detected.ConclusionABC/3TC + RPV is a safe and effective switch option for maintenance therapy in virologically suppressed HIV-1 individuals with in Singapore.

Investigation of multidrug-resistance mutations of hepatitis B virus (HBV) in a large cohort of chronic HBV-infected patients with treatment of nucleoside/nucleotide analogs

Multidrug-resistance hepatitis B virus (MDR HBV), defined as those with mutations resistant to both nucleoside analogs lamivudine/telbivudine/entecavir (LAM/LdT/ETV) and nucleotide analog adefovir (ADV), has potential to cause treatment difficulty. To clarify clinical prevalence and virological features of MDR HBV, we investigated serum samples from 28,236 chronic HBV-infected patients with treatment of nucleoside/nucleotide analogs. All patients underwent resistance testing in the Fifth Medical Center of Chinese PLA General Hospital between 2007 and 2019. MDR mutations were screened by direct sequencing; MDR strains (with mutations co-located on the same viral genome) were verified by clonal sequencing (≥20 clones/sample) and subjected to phenotypic analysis if necessary. MDR mutations were detected in 0.81% (229/28,236) patients. MDR strains were verified in 83.0% (190/229) of MDR mutation-positive patients. As ETV-resistance mutation (ETVr) had additional mutation(s) on LAMr conferring more resistance, MDR mutations fell into LAMr + ADVr and ETVr + ADVr subsets. Sixteen mutation patterns of MDR strains were verified, including eight with LAMr + ADVr and eight with ETVr + ADVr. Refractory to sequential therapies of LAM/LdT/ETV and ADV were closely linked with MDR HBV development. Ten representative MDR strains (five LAMr + ADVr and five ETVr + ADVr) tested all had decrease in replication capacity compared to wild-type strains and decrease extent was positively related with the number of primary resistance on viral genome. Compared to ADV + ETV, TDF/TDF + ETV showed higher inhibitory rates on MDR HBV, especially for the five ETVr + ADVr strains (74.5%–97.6% vs. 60.2%–79.5%, all P < 0.05). This study significantly extends the knowledge on MDR HBV and has clinical implications for resistance management.

Investigation of immune escape-associated mutations of hepatitis B virus in patients harboring hepatitis B virus drug-resistance mutations.

BACKGROUNDIt is unclear whether immune escape-associated mutations in the major hydrophilic region of hepatitis B virus surface antigen (HBsAg) are associated with nucleoside/nucleotide analog resistance.AIMTo evaluate the association between immune escape-associated mutations and nucleoside/nucleotide analog resistance mutations.METHODSIn total, 19440 patients with chronic hepatitis B virus infection, who underwent resistance testing at the Fifth Medical Center of Chinese PLA General Hospital between July 2007 and December 2017, were enrolled. As determined by sequence analysis, 6982 patients harbored a virus with resistance mutations and 12458 harbored a virus lacking resistance mutations. Phenotypic analyses were performed to evaluate HBsAg production, replication capacity, and drug-induced viral inhibition of patient-derived drug-resistant mutants with or without the coexistence of sA159V.RESULTSThe rate of immune escape-associated mutation was significantly higher in 9 of the 39 analyzed mutation sites in patients with resistance mutations than in patients without resistance mutations. In particular, these mutations were sQ101H/K/R, sS114A/L/T, sT118A/K/M/R/S/V, sP120A/L/Q/S/T, sT/I126A/N/P/S, sM133I/L/T, sC137W/Y, sG145A/R, and sA159G/V. Among these, sA159V was detected in 1.95% (136/6982) of patients with resistance mutations and 1.08% (134/12,458) of patients lacking resistance mutations (P < 0.05). The coexistence of sA159V with lamivudine (LAM) and entecavir (ETV)-resistance mutations in the same viral genome was identified during follow-up in some patients with drug resistance. HBsAg production was significantly lower and the replication capacity was significantly higher, without a significant difference in LAM/ETV susceptibility, in sA159V-containing LAM/ETV-resistant mutants than in their sA159V-lacking counterparts.CONCLUSIONIn summary, we observed a close link between the increase in certain immune escape-associated mutations and the development of resistance mutations. sA159V might increase the fitness of LAM/ETV-resistant mutants under environmental pressure in some cases.

Hepatitis B virus mutation pattern rtA181S+T184I+M204I may contribute to multidrug resistance in clinical practice: Analysis of a large cohort of Chinese patients

The study aimed to characterize the prevalence and virological features of the rtA181S + T184I + M204I mutant in a large cohort of patients with chronic HBV infection. In total, 22,009 nucleoside/nucleotide analog-treated patients who underwent resistance testing at the Fifth Medical Center of Chinese PLA General Hospital between 2007 and 2016 were enrolled. Serum samples were collected for HBV reverse-transcriptase gene sequencing. Phenotypic analysis of the viral replication capacity and drug susceptibility was performed. The rtA181S mutation was detected in 0.82% (180/22,009) of samples. rtA181S-positive patients had significantly higher lamivudine (LAM), adefovir (ADV), and entecavir (ETV) exposure than rtA181S-negative patients. Of 180 rtA181S-positive patients, 42 had no coexistent resistance mutations, 34 had coexisting LAM-resistance mutation (LAMr), 17 had coexisting ADV-resistance mutation (ADVr), and 86 had coexisting ETV-resistance mutation (ETVr), and one had ADVr + ETVr. rtA181S + T184I + M204I occurred in 79.1% (68/86) of patients with rtA181S + ETVr and 37.8% (68/180) of all rtA181S-positive patients. Longitudinal analysis of the clinical course of resistant mutant evolution for four representative cases showed that rtA181S + T184I + M204I developed in all patients who had received LAM/telbivudine ± ADV and was receiving ETV or ADV + ETV. Compared with wild-type, the rtA181S + T184I + M204I mutant had 53.7% lower replication capacity and >1000-, 3.9-, and 383.3-fold greater LAM, ADV, and ETV resistance, respectively, but remained sensitive to tenofovir. Artificial elimination of rtA181S from the rtA181S + T184I + M204I mutant restored viral susceptibility to ADV but decreased viral replication capacity. Our study presented the first evidence that HBV rtA181S + T184I + M204I mutation had features of multidrug-resistance that contributed to resistance to both nucleoside and nucleotide analogs.

Myopathy secondary to empagliflozin therapy in type 2 diabetes.

SummarySodium/glucose co-transporter 2 (SGLT2) inhibitors are novel oral hypoglycaemic agents that are increasingly used in the management of type 2 diabetes mellitus (T2DM). They are now recommended as second-line pharmacotherapy (in conjunction with metformin) in patients with type 2 diabetes and established atherosclerotic heart disease, heart failure or chronic kidney disease due to their favourable effects on cardiovascular and renal outcomes. We report a case of a 69-year-old man who developed muscle pain, weakness and wasting after commencing the SGLT2 inhibitor empagliflozin. This persisted for 1 year before he underwent resistance testing, which confirmed muscle weakness. His symptoms resolved within weeks of ceasing empagliflozin, with improvement in muscle strength on clinical assessment and resistance testing and reversal of MRI changes. No other cause of myopathy was identified clinically, on biochemical assessment or imaging, suggesting that empagliflozin was the cause of his myopathy.Learning points:Empagliflozin, a commonly used SGLT2 inhibitor, was associated with myopathy.A high degree of suspicion is required to diagnose drug-induced myopathy, with a temporal relationship between starting the medication and symptom onset being the main indicator.Recognition of drug-induced myopathy is essential, as discontinuation of the offending drug typically improves symptoms.

Investigation of hepatitis B virus (HBV) rtS78T/sC69* mutation in a large cohort of chronic HBV-infected patients with nucleoside/nucleotide analogue treatment

This study aimed to investigate clinical occurrence and significance of the rtS78T/sC69* mutation of hepatitis B virus (HBV). A total of 22,009 consecutive chronic HBV-infected patients who underwent resistance testing at the Fifth Medical Center of Chinese PLA General Hospital (Original name Beijing 302 Hospital) from 2007 to 2016 were enrolled. Serum samples were collected for sequence analysis of HBV reverse-transcriptase (RT) and S regions. Phenotypic analysis was performed to evaluate the viral replication capacity and drug susceptibility. The rtS78T mutation was detected in 0.83% (182/22,009) of the patients’ samples. All mutations simultaneously created a stop codon at sC69 (sC69*). The prevalence of rtS78T/sC69* did not differ significantly between the patients with and without entecavir/tenofovir treatment. Of the 182 mutation-positive samples, 41 (22.5%) were detected with signature drug-resistance mutations to adefovir (n = 26), lamivudine (n = 11), entecavir (n = 3), and lamivudine plus adefovir (n = 1). The HBV DNA and RNA levels of the rtS78T/sC69* mutant were significantly increased compared to the wild-type; while the mutant had undetectable secreted and intracellular HBsAg, and its half maximal effective concentration to lamivudine, adefovir, entecavir, and tenofovir were 3.73-, 1.61-, 4.76-, and 3.71-fold of the wild-type, respectively. Artificial elimination of the rtS78T mutation had a limited effect on the drug susceptibilities. The data obtained in the present study suggested that the emergence of the rtS78T/sC69* mutation was not closely related to entecavir/tenofovir treatment and itself appeared insufficient to confer drug resistance unless it coexisted with signature drug-resistance mutations.

Sofosbuvir/Velpatasvir/Voxilaprevir for Previous Treatment Failures With Glecaprevir/Pibrentasvir in Chronic Hepatitis C Infection.

Chronic hepatitis C-infected patients who do not respond to nonstructural 5A inhibitor-containing regimens have few treatment options. It is unclear if patients who fail glecaprevir/pibrentasvir (G/P) (Mavyret) can be re-treated with sofosbuvir/velpatasvir/voxilaprevir (SOF/VEL/VOX) (Vosevi) because the latter's registration trials antedated the availability of the former. Adherent virologic failures to G/P were re-treated with 12 weeks of SOF/VEL/VOX, and all subjects underwent resistance testing at baseline and again with subsequent relapse. Ninety-four percent of subjects achieved sustained virologic response with re-treatment, despite 90% of 31 subjects harboring nonstructural 5A inhibitor resistance-associated mutations at baseline. SOF/VEL/VOX is an effective regimen for virologic failures to G/P.

Hepatitis B virus mutation pattern rtL180M+A181C+M204V may contribute to entecavir resistance in clinical practice

ABSTRACT Background and Aims: Entecavir (ETV) resistance of hepatitis B virus (HBV) conventionally requires rt184, 202, or 250 mutations plus lamivudine-resistance mutation (rtM204V/I ± L180M). This study aimed to clarify whether rtL180M+A181C+M204V mutations may contribute to HBV ETV resistance. Methods: Serum samples were collected from 22,009 patients who underwent resistance testing in Beijing 302 Hospital from 2007 to 2016. HBV reverse transcriptase (RT) gene was screened by direct sequencing and verified by clonal sequencing. Phenotypic analysis was performed for evaluating replication capacity and drug susceptibility. Results: Classical ETV-resistance mutations of HBV were detected in 1252 patients who were receiving ETV therapy. The rtA181C mutation was detected with rtL180M+M204V mutations in 18 lamivudine-experienced ETV-treated patients, and the emergence of the mutations was associated with virological breakthrough or inadequate virological response to ETV. Patient-derived representative rtA181C-containing mutants, rtL180M+A181C+M204V, rtL180M+A181C+M204V+M250V, and rtL180M+A181C+S202G+M204V, exhibited 45.7%, 25.9%, and 25.0% replication capacity and 85.6-, 356.1-, and 307.1-fold decreased susceptibility to ETV respectively compared to the wild-type strain, while the three mutants remained sensitive to tenofovir (TDF). Artificial elimination of rtA181C largely restored the rtL180M+A181C+M204V mutant’s sensitivity to ETV. Molecular modelling of viral RT binding to ETV showed that the rtL180M+A181C+M204V mutant had a less stable conformation compared to rtL180M+M204V mutant. In clinical practice, undetectable serum HBV DNA was achieved in two of five longitudinally followed rtA181C-positive patients who received switching-to TDF therapy, but not in the other three who received add-on adefovir therapy during observation. Conclusions: Both clinical and experimental data support rtL180M+A181C+M204V as a novel non-classical ETV-resistance mutation pattern.

Pretreatment HIV drug resistance among adults initiating ART in Namibia.

Continued use of standardized, first-line ART containing NNRTIs and NRTIs may contribute to ongoing emergence of HIV drug resistance (HIVDR) in Namibia. A nationally representative cross-sectional survey was conducted during 2015-16 to estimate the prevalence of significant pretreatment HIV drug resistance (PDR) and viral load (VL) suppression rates 6-12 months after initiating standardized first-line ART. Consenting adult patients (≥18 years) initiating ART were interviewed about prior antiretroviral drug (ARV) exposure and underwent resistance testing using dried blood spot samples. PDR was defined as mutations causing low-, intermediate- and high-level resistance to ARVs according to the 2014 WHO Surveillance of HIV Drug Resistance in Adults Initiating ART. The prevalence of PDR was described by patient characteristics, ARV exposure and VL results. Results were weighted to be nationally representative. Successful genotyping was performed for 381 specimens; 144 (36.6%) specimens demonstrated HIVDR, of which 54 (12.7%) demonstrated PDR. Resistance to NNRTIs was most prevalent (11.9%). PDR was higher in patients with previous ARV exposure compared with no exposure (30.5% versus 9.6%) (prevalence ratio = 3.17; P < 0.01). This survey demonstrated overall PDR at >10% among adults initiating ART in Namibia. Patients with prior ARV exposure had higher rates of PDR. Introducing a non-NNRTI-based regimen for first-line ART should be considered to maximize benefit of ART and minimize the emergence of HIVDR.

Risk Factors for the Development of Cytomegalovirus Resistance in Solid Organ Transplantation: A Retrospective Case-Control Study

BackgroundCytomegalovirus (CMV) resistance is an emerging problem in solid organ transplant recipients. Risk factors are not well defined. MethodsRecipients with CMV viremia of solid organ transplants who underwent CMV resistance testing between January 2010 and March 2016 were divided in 2 groups: proven CMV resistance and refractory CMV infection. A third group was added to compare patients with viremia during the study period with patients with no resistance proven or suspected. We aimed to identify risk factors associated with the occurrence of CMV genotypic resistance. ResultsForty-nine patients underwent resistance testing. Eleven (22.45%) developed genotypic mutations. Group 1 vs groups 2 and 3 had higher prednisone (P = .01) and tacrolimus levels (P = .03); did not respond to antivirals (P < .0001); and had a higher rate of fungal infections (P = .03). CMV resistance was less common in liver and kidney vs heart, small bowel, and mutivisceral recipients (P = .0007). There was no difference in duration of antiviral prophylaxis, viremia while on antiviral prophylaxis, rate of end-organ disease, graft loss, and overall survival. Persistent clinical disease and viremia despite antiviral therapy was the most important risk factor for development of CMV resistance. ConclusionPersistent clinical disease despite antiviral therapy is an important risk factor and may in part be due to a high degree of immunosuppression. Graft loss and survival were not impacted by CMV resistance.

Intensive adherence counselling for HIV-infected individuals failing second-line antiretroviral therapy in Johannesburg, South Africa.

In resource-limited settings, where genotypic drug resistance testing is rarely performed and poor adherence is the most common reason for treatment failure, programmatic approaches to handling treatment failure are essential. This study was performed to describe one such approach to adherence optimisation. This was a single-arm study of patients on second-line protease inhibitor (PI)-based antiretroviral therapy (ART) with a HIV-1 RNA ≥400 copies/ml in Johannesburg, South Africa, between 1 March 2012 and 1 December 2013. Patients underwent enhanced adherence counselling. Those with improved adherence and a repeat viral load of >1000 copies/ml underwent HIV-1 drug resistance testing. We describe results using simple proportions and 95% confidence intervals. Of the 400 patients who underwent targeted adherence counselling after an elevated viral load on second-line ART, 388 (97%) underwent repeat viral load testing. Most of these (n = 249; 64%, 95% CI 59-69) resuppressed (<400 copies/ml) on second line. By the end of follow-up (1 March 2014), among the 139 (36%, 95% CI: 31-41%), who did not initially resuppress after being targeted, 106 had a viral load >400 copies/ml, 11 switched to third line, 5 were awaiting third line, 4 had died and 13 were lost to follow-up. Among the unsuppressed, 48 successfully underwent resistance testing with some resistance detected in most (41/48). Most (64%) second-line treatment failure in this clinic is related to adherence and can be overcome with careful adherence support. Controlled interventions are needed to determine what the optimal approach is to improving second-line outcomes and reducing the need for third-line ART.

Drug resistance of Mycobacterium tuberculosis in Malawi: a cross-sectional survey.

ObjectiveTo document the prevalence of multidrug resistance among people newly diagnosed with – and those retreated for – tuberculosis in Malawi.MethodsWe conducted a nationally representative survey of people with sputum-smear-positive tuberculosis between 2010 and 2011. For all consenting participants, we collected demographic and clinical data, two sputum samples and tested for human immunodeficiency virus (HIV).The samples underwent resistance testing at the Central Reference Laboratory in Lilongwe, Malawi. All Mycobacterium tuberculosis isolates found to be multidrug-resistant were retested for resistance to first-line drugs – and tested for resistance to second-line drugs – at a Supranational Tuberculosis Reference Laboratory in South Africa.FindingsOverall, M. tuberculosis was isolated from 1777 (83.8%) of the 2120 smear-positive tuberculosis patients. Multidrug resistance was identified in five (0.4%) of 1196 isolates from new cases and 28 (4.8%) of 581 isolates from people undergoing retreatment. Of the 31 isolates from retreatment cases who had previously failed treatment, nine (29.0%) showed multidrug resistance. Although resistance to second-line drugs was found, no cases of extensive drug-resistant tuberculosis were detected. HIV testing of people from whom M. tuberculosis isolates were obtained showed that 577 (48.2%) of people newly diagnosed and 386 (66.4%) of people undergoing retreatment were positive.ConclusionThe prevalence of multidrug resistance among people with smear-positive tuberculosis was low for sub-Saharan Africa – probably reflecting the strength of Malawi’s tuberculosis control programme. The relatively high prevalence of such resistance observed among those with previous treatment failure may highlight a need for a change in the national policy for retreating this subgroup of people with tuberculosis.

The Impact of Transmitted Drug-Resistance on Treatment Selection and Outcome of First-Line Highly Active Antiretroviral Therapy (HAART)

The study aim was to determine how resistance testing influences outcome of first-line highly active antiretroviral therapy (HAART) in routine practice in the United Kingdom. The prevalence of transmitted drug resistance and the genotypic sensitivity score (GSS) of first-line HAART regimens were determined using data from the UK Collaborative HIV Cohort(CHIC) Study. Factors associated with starting a regimen with a reduced GSS and subsequent virological responses were analyzed by logistic and Cox regression. Amongst patients tested in 1999–2006, 116 of 1175 (10%) had $1 resistance mutation; 64 patients (5.4%) had $1 mutation associated with resistance to drugs in the initial HAART regimen and 54 (4.6%) showed a GSS, 3. Factors independently associated with a GSS, 3 were starting HAART in 1999–2001 vs. 2004–2006 (odds ratio = 2.63; 95% confidence interval: 1.19 to 5.83) and use of ritonavir-boosted protease inhibitor (PI/r)–based vs. nonnucleoside reverse transcriptase inhibitor–based regimens (1.97; 1.06 to 3.64). AGSS .3 was independently associated with virological suppression(hazard ratio for GSS, 3 = 0.60; 95% confidence interval 0.41 to 0.87). Most patients starting HAART after undergoing resistance testing received regimens with a GSS $3. PI/r-based therapy was often selected in patients with resistance to the nucleoside reverse transcriptase inhibitor backbone. Low GSS predicted poor virological suppression and the association persisted after adjusting for PI/r use.

Genotypic Resistance Profile and Clinical Progression of Treatment-Experienced HIV Type 1-Infected Patients with Virological Failure

We explored the relationship between HIV-1 drug resistance in treatment-experienced patients and disease progression in a cohort of patients undergoing resistance testing to guide treatment decisions. A total of 601 treatment-failing individuals tested for genotypic HIV-1 drug resistance between 1998 and 2004 were selected. At genotypic testing, median HIV-1 RNA levels and CD4 counts were 3.8 log copies/ml and 293 cells/mul, respectively; 84% had resistance mutations to nucleoside reverse transcriptase inhibitors (NRTIs), 42% had resistance mutations to non-NRTIs, 51% had major resistance mutations to protease inhibitors (PI), 12% had no major resistance mutations to any drug class, 22% had mutations to one class, 42% had mutations to two classes, and 23% had mutations to three classes. During a follow-up of 714.7 patients/year, 80 patients showed an AIDS-defining event or died. In multivariable models adjusting for prior AIDS, baseline CD4 counts, HIV-1 RNA, and calendar year, viral resistance variables associated with increased hazards of clinical progression were the presence of reverse transcriptase substitution T215F (p = 0.002) and the presence of three or more protease substitutions among L33F/I/V, V82A/F/L/T, I84V, and L90M (p = 0.003). Resistance to three drug classes remained independently predictive of clinical progression only when calendar year was not used as an adjustment factor. Prevention and treatment of multiple drug class resistance are clinical priorities for HIV-infected patients. In recent years, improved treatment options may have helped in reducing part of the resistance-associated clinical progression.

Declining Prevalence of HIV-1 Drug Resistance in Treatment-Failing Patients: A Clinical Cohort Study

A major barrier to successful viral suppression in HIV type 1 (HIV-1)-infected individuals is the emergence of virus resistant to antiretroviral drugs. We explored the evolution of genotypic drug resistance prevalence in treatment-failing patients from 1999 to 2005 in a clinical cohort. Prevalence of major International AIDS Society-USA HIV-1 drug resistance mutations was measured over calendar years in a population with treatment failure and undergoing resistance testing. Predictors of the presence of resistance mutations were analysed by logistic regression. Significant reductions of the prevalence of resistance to all three drug classes examined were observed. This was accompanied by a reduction in the proportion of treatment-failing patients. Independent predictors of drug resistance were the earlier calendar year, prior use of suboptimal nucleoside analogue therapy, male sex and higher CD4 levels at testing. In a single clinical cohort, we observed a decrease in the prevalence of resistance to all three examined antiretroviral drug classes over time. If this finding is confirmed in multicentre cohorts it may translate into reduced transmission of drug-resistant virus from treated patients.

Declining Prevalence of HIV-1 Drug Resistance in Treatment-Failing Patients: A Clinical Cohort Study

ObjectivesA major barrier to successful viral suppression in HIV type 1 (HIV-1)-infected individuals is the emergence of virus resistant to antiretroviral drugs. We explored the evolution of genotypic drug resistance prevalence in treatment-failing patients from 1999 to 2005 in a clinical cohort.Patients and MethodsPrevalence of major International AIDS Society-USA HIV-1 drug resistance mutations was measured over calendar years in a population with treatment failure and undergoing resistance testing. Predictors of the presence of resistance mutations were analysed by logistic regression.ResultsSignificant reductions of the prevalence of resistance to all three drug classes examined were observed. This was accompanied by a reduction in the proportion of treatment-failing patients. Independent predictors of drug resistance were the earlier calendar year, prior use of suboptimal nucleoside analogue therapy, male sex and higher CD4 levels at testing.ConclusionsIn a single clinical cohort, we observed a decrease in the prevalence of resistance to all three examined antiretroviral drug classes over time. If this finding is confirmed in multicentre cohorts it may translate into reduced transmission of drug-resistant virus from treated patients.

Relationship between drug resistance and HIV-1 disease progression or death in patients undergoing resistance testing.

To evaluate factors associated with drug resistance detected by genotypic antiretroviral resistance testing (GART), and to determine the association between the level of resistance and subsequent human immunodeficiency type 1 (HIV-1) disease progression or death. Observational cohort study. We identified highly active antiretroviral therapy (HAART)-treated patients who had GART as part of clinical management. Factors associated with greater numbers of resistance mutations were assessed by ordinal logistic regression. Survival analysis was used to assess time to a new opportunistic condition or death following GART. A total of 572 patients were identified who had GART: of these, 50% had 0-2 resistance mutations, 33% had 3-6 mutations, and 17% had >/= 7 mutations. In multivariate analysis, prolonged use of HAART in the setting of incomplete viral suppression was significantly associated with more drug resistance. Patients with fewer resistance mutations were significantly more likely to achieve viral suppression after GART than patients with more mutations. Compared to patients with two or less resistance mutations, those with three to six mutations, or seven or more mutations were not at higher risk of HIV-1 disease progression or death over a median follow-up of 15 months. In contrast, continued HAART use following GART was strongly associated with slower disease progression, particularly at lower CD4 cell counts. These results support the hypothesis the drug-resistant HIV-1 may be less pathogenic than wild-type virus, and that continued use of HAART might provide clinical benefit, despite persistent viremia and HIV-1 drug resistance.