Delayed identification of treatment failure causes high levels of acquired drug resistance and less future drug options among HIV-1-infected South Indians.

PURPOSE: HIV-1 Drug Resistance Mutations (DRMs) among Immunological failure (IF) on NRTI based first-line regimens, Thymidine analogue (TA) - AZT & D4T and Non-Thymidine Analogue (NTA) -TDF; and predict viral drug susceptibility to gain vision about optimal treatment strategies for second-line. METHODS: Cross-sectionally, 300 HIV-1 infected patients, failing first-line HAART were included. HIV-1 pol gene spanning 20-240 codons of RT was genotyped and mutation pattern was examined, (IAS-USA 2014 and Stanford HIV drug resistance database v7.0). RESULTS: The median age of the participants was 35 years (IQR 29-40), CD4 T cell count of TDF failures was low at 172 cells/µL (IQR 80-252), and treatment duration was low among TDF failures (24 months vs. 61 months) (p < 0.0001). Majority of the TDF failures were on EFV based first-line (89 % vs 45 %) (p < 0.0001). Level of resistance for TDF and AZT shows, that resistance to TDF was about one-third (37 %) of TDF participants and onefourth (23 %) of AZT participants; resistance to AZT was 17 % among TDF participants and 47 % among AZT participants; resistance to both AZT and TDF was significantly high among AZT participants [21 % vs. 8 %, OR 3.057 (95 % CI 1.4-6.8), p < 0.0001]. CONCLUSION: Although delayed identification of treatment failure caused high levels of acquired drug resistance in our study. Thus, we must include measures to regularize virological monitoring with integrated resistance testing in LMIC (Low and Middle Income Countries) like in India; this will help to preserve the effectiveness of ARV and ensure the success of ending AIDS as public health by 2030.

Nucleoside Analog 2',3'-Isopropylidene-5-Iodouridine as Novel Efficient Inhibitor of HIV-1.

Nucleoside reverse transcriptase inhibitors are the first class of drugs to be approved by the FDA for the suppression of HIV-1 and are widely used for this purpose in combination with drugs of other classes. Despite the progress in HIV-1 treatment, there is still the need to develop novel efficient antivirals. Here the efficiency of HIV-1 inhibition by a set of original 5-substituted uridine nucleosides was studied. We used the replication deficient human immunodeficiency virus (HIV-1)-based lentiviral particles and identified that among the studied compounds, 2',3'-isopropylidene-5-iodouridine was shown to cause anti-HIV-1 activity. Importantly, no toxic action of this compound against the cells of T-cell origin was found. We determined that this compound is significantly more efficient at suppressing HIV-1 compared to Azidothymidine (AZT) when taken at the high non-toxic concentrations. We did not find any profit when using AZT in combination with 2',3'-isopropylidene-5-iodouridine. 2',3'-Isopropylidene-5-iodouridine acts synergistically to repress HIV-1 when combined with the CDK4/6 inhibitor Palbociclib in low non-toxic concentration. No synergistic antiviral action was detected when AZT was combined with Palbociclib. We suggest 2',3'-isopropylidene-5-iodouridine as a novel perspective non-toxic compound that may be used for HIV-l suppression.

Can plant-derived anti-HIV compounds be used in COVID-19 cases?

People living with HIV are more exposed to the adverse health effects of the worldwide COVID-19 pandemic. The pandemic's health and social repercussions may promote drug abuse and inadequate HIV management among this demographic. The coronavirus pandemic of 2019 (COVID-19) has caused unprecedented disruption worldwide in people's lives and health care. When the COVID-19 epidemic was identified, people with HIV faced significant obstacles and hurdles to achieving optimal care results. The viral spike protein (S-Protein) and the cognate host cell receptor angiotensin-converting enzyme 2 (ACE2) are both realistic and appropriate intervention targets. Calanolides A, Holy Basil, Kuwanon-L, and Patentiflorin have anti-HIV effects. Our computational biology study investigated that these compounds all had interaction binding scores related to S protein of coronavirus of -9.0 kcal /mol, -7.1 kcal /mol, -9.1 kcal /mol, and -10.3 kcal/mol/mol, respectively. A combination of plant-derived anti-HIV compounds like protease inhibitors and nucleoside analogs, which are commonly used to treat HIV infection, might be explored in clinical trials for the treatment of COVID-19.

Pricing Retrovir: Wellcome PLC and the Role of Pharmaceutical Companies in the Global AIDS Crisis, 1986 to 1991.

In spring 1987, British pharmaceutical company Wellcome PLC released azidothymidine (AZT) sold under trade name Retrovir, the first successful treatment for AIDS. In the context of a global public health emergency and with no competing products, Wellcome invested heavily in upfront costs to bring Retrovir to market, reflected in the original launch price of $188 (US dollars), applied to all other markets. Retrovir subsequently faced backlash in the United States for its high cost and Wellcome's profits became a target of debates about prescription drugs in the American healthcare system. As a result, the company agreed to two price reductions within the first two years of market release. Events in the US had global impact, discouraging the company from providing AZT via commercial channels in African countries. Drawing from new archival material, this article explores how Retrovir's pricing reflected the uncertainties of the global AIDS crisis as well as the unique risks Wellcome faced as a foreign company in its most important market of the US. It argues that, contrary to critical opinion, Wellcome's pricing of Retrovir did reflect an underlying principle regarding the appropriate role of for-profit research-intensive pharmaceutical companies during an unprecedented pandemic.

Gold nanoparticles capped DHPMs for meliorate detection of antiretroviral drug: Azidothymidine.

Anti-human immunodeficiency (HIV)-drug azidothymidine interferes with the reverse transcriptase enzyme, which results in reduced activity of HIV thereby inhibiting the growth of the virus. Owing to the side effects of high doses and short half-life of this antiviral drug azidothymidine (AZT): a fast and convenient method for its detection would be helpful for HIV patients getting treated with AZT. Referring to this, we synthesized a Biginelli based receptor R1 and evaluated its sensing properties towards AZT with different techniques (UV-Visible, circular dichroism (CD), cyclic voltammetry (CV) by preparing its organic nanoparticles (ONPs) and gold-coated ONPs (AuNP@ONP). The formation of AuNP@ONP was confirmed by UV-Visible spectroscopy, cyclic voltammetry, and HRTEM. It was observed that both the probes selectively sense AZT among various thymidine analogs but AuNP@ONP showed better response on CV, Differential pulse voltammetry (DPV) and, linear sweep voltammetry (LSV) with a detection limit of 6 nM. Proton NMR (1H NMR) reveals that the azide group present at the 3' position is responsible for the selective response of AZT with probes. Quantitative determination by the probes in the pharmaceutical sample gives the recovery percentage above 97%. Hence, economic, affordable, ready-to-use chemosensor for AZT (in an aqueous medium) with low detection limit having satisfactory utility for HIV supplements have been developed.

Giardia intestinalis thymidine kinase is a high-affinity enzyme crucial for DNA synthesis and an exploitable target for drug discovery.

Giardiasis is a diarrheal disease caused by the unicellular parasite Giardia intestinalis, for which metronidazole is the main treatment option. The parasite is dependent on exogenous deoxyribonucleosides for DNA replication and thus is also potentially vulnerable to deoxyribonucleoside analogs. Here, we characterized the G. intestinalis thymidine kinase, a divergent member of the thymidine kinase 1 family that consists of two weakly homologous parts within one polypeptide. We found that the recombinantly expressed enzyme is monomeric, with 100-fold higher catalytic efficiency for thymidine compared to its second-best substrate, deoxyuridine, and is furthermore subject to feedback inhibition by dTTP. This efficient substrate discrimination is in line with the lack of thymidylate synthase and dUTPase in the parasite, which makes deoxy-UMP a dead-end product that is potentially harmful if converted to deoxy-UTP. We also found that the antiretroviral drug azidothymidine (AZT) was an equally good substrate as thymidine and was active against WT as well as metronidazole-resistant G. intestinalis trophozoites. This drug inhibited DNA synthesis in the parasite and efficiently decreased cyst production in vitro, which suggests that it could reduce infectivity. AZT also showed a good effect in G. intestinalis-infected gerbils, reducing both the number of trophozoites in the small intestine and the number of viable cysts in the stool. Taken together, these results suggest that the absolute dependency of the parasite on thymidine kinase for its DNA synthesis can be exploited by AZT, which has promise as a future medication effective against metronidazole-refractory giardiasis.

Repurposing of Ciclopirox to Overcome the Limitations of Zidovudine (Azidothymidine) against Multidrug-Resistant Gram-Negative Bacteria.

Multidrug-resistant (MDR) Gram-negative bacteria are the top-priority pathogens to be eradicated. Drug repurposing (e.g., the use of non-antibiotics to treat bacterial infections) may be helpful to overcome the limitations of current antibiotics. Zidovudine (azidothymidine, AZT), a licensed oral antiviral agent, is a leading repurposed drug against MDR Gram-negative bacterial infections. However, the rapid emergence of bacterial resistance due to long-term exposure, overuse, or misuse limits its application, making it necessary to develop new alternatives. In this study, we investigated the efficacy of ciclopirox (CPX) as an alternative to AZT. The minimum inhibitory concentrations of AZT and CPX against MDR Gram-negative bacteria were determined; CPX appeared more active against ß-lactamase-producing Escherichia coli, whereas AZT displayed no selectivity for any antibiotic-resistant strain. Motility assays revealed that ß-lactamase-producing Escherichia coli strains were less motile in nature and more strongly affected by CPX than a parental strain. Resistance against CPX was not observed in E. coli even after 25 days of growth, whereas AZT resistance was observed in less than 2 days. Moreover, CPX effectively killed AZT-resistant strains with different resistance mechanisms. Our findings indicate that CPX may be utilized as an alternative or supplement to AZT-based medications to treat opportunistic Gram-negative bacterial infections.

Synergistic Combination of AS101 and Azidothymidine against Clinical Isolates of Carbapenem-Resistant Klebsiella pneumoniae.

Owing to the over usage of carbapenems, carbapenem resistance has become a vital threat worldwide, and, thus, the World Health Organization announced the carbapenem-resistant Enterobacteriaceae (CRE) as the critical priority for antibiotic development in 2017. In the current situation, combination therapy would be one solution against CRE. Azidothymidine (AZT), a thymidine analog, has demonstrated its synergistically antibacterial activities with other antibiotics. The unexpected antimicrobial activity of the immunomodulator ammonium trichloro(dioxoethylene-o,o')tellurate (AS101) has been reported against carbapenem-resistant Klebsiella pneumoniae (CRKP). Here, we sought to investigate the synergistic activity between AS101 and AZT against 12 CRKP clinical isolates. According to the gene detection results, the blaOXA-1 (7/12, 58.3%), blaDHA (7/12, 58.3%), and blaKPC (7/12, 58.3%) genes were the most prevalent ESBL, AmpC, and carbapenemase genes, respectively. The checkerboard analysis demonstrated the remarkable synergism between AS101 and AZT, with the observable decrease in the MIC value for two agents and the fractional inhibitory concentration (FIC) index ≤0.5 in all strains. Hence, the combination of AS101 and azidothymidine could be a potential treatment option against CRKP for drug development.

A Novel Method for Predicting the Human Inherent Clearance and Its Application in the Study of the Pharmacokinetics and Drug-Drug Interaction between Azidothymidine and Fluconazole Mediated by UGT Enzyme.

In order to improve the benefit-risk ratio of pharmacokinetic (PK) research in the early development of new drugs, in silico and in vitro methods were constructed and improved. Models of intrinsic clearance rate (CLint) were constructed based on the quantitative structure-activity relationship (QSAR) of 7882 collected compounds. Moreover, a novel in vitro metabolic method, the Bio-PK dynamic metabolic system, was constructed and combined with a physiology-based pharmacokinetic model (PBPK) model to predict the metabolism and the drug-drug interaction (DDI) of azidothymidine (AZT) and fluconazole (FCZ) mediated by the phase II metabolic enzyme UDP-glycosyltransferase (UGT) in humans. Compared with the QSAR models reported previously, the goodness of fit of our CLint model was slightly improved (determination coefficient (R2) = 0.58 vs. 0.25-0.45). Meanwhile, compared with the predicted clearance of 61.96 L/h (fold error: 2.95-3.13) using CLint (8 µL/min/mg) from traditional microsomal experiment, the predicted clearance using CLint (25 µL/min/mg) from Bio-PK system was increased to 143.26 L/h (fold error: 1.27-1.36). The predicted Cmax and AUC (the area under the concentration-time curve) ratio were 1.32 and 1.84 (fold error: 1.36 and 1.05) in a DDI study with an inhibition coefficient (Ki) of 13.97 µM from the Bio-PK system. The results indicate that the Bio-PK system more truly reflects the dynamic metabolism and DDI of AZT and FCZ in the body. In summary, the novel in silico and in vitro method may provide new ideas for the optimization of drug metabolism and DDI research methods in early drug development.

Azidothymidine Downregulates Insulin-Like Growth Factor-1 Induced Lipogenesis by Suppressing Mitochondrial Biogenesis and Mitophagy in Immortalized Human Sebocytes.

BACKGROUND: Increased sebum secretion is considered the main causative factor in the pathogenesis of acne. There is an unmet pharmacological need for a novel drug that can control sebum production with a favorable adverse effect profile. OBJECTIVE: To investigate the effect of azidothymidine on lipid synthesis in sebocytes and to identify the underlying mechanism of the inhibitory effect of azidothymidine on insulinlike growth factor (IGF)-1-induced lipid synthesis in sebocytes. METHODS: Immortalized human sebocytes were used for the analysis. Thin-layer chromatography (TLC) and Oil Red O staining were performed to evaluate lipid synthesis in the sebocytes. The differentiation, lipid synthesis, mitochondrial biogenesis, and mitophagy in sebocytes were investigated. RESULTS: TLC and Oil Red O staining revealed that azidothymidine reduced IGF-1 induced lipid synthesis in the immortalized human sebocytes. Azidothymidine also reduced IGF-1-induced expression of transcriptional factors and enzymes involved in sebocyte differentiation and lipid synthesis, respectively. Moreover, we found that IGF-1 upregulated the levels of peroxisome proliferator-activated receptorgamma coactivator-1α, LC-3B, p62, and Parkin, major regulators of mitochondrial biogenesis and mitophagy in immortalized human sebocytes. In contrast, azidothymidine inhibited IGF-1 induced mitochondrial biogenesis and mitophagy in the sebocytes. CONCLUSION: These results suggest that azidothymidine downregulates IGF-1-induced lipogenesis by dysregulating the quality of mitochondria through suppression of mitochondrial biogenesis and mitophagy in immortalized human sebocytes. Our study provides early evidence that azidothymidine may be an effective candidate for a new pharmacological agent for controlling lipogenesis in sebocytes.

Rapid, user-friendly, and inexpensive detection of azidothymidine.

Strict adherence to highly active antiretroviral therapy (HAART) is very important to improve the quality of life for HIV-positive patients to reduce new infections and determine treatment success. Azidothymidine (AZT) is an antiretroviral drug commonly used in HAART treatment. In this research, an "add, mix, and measure" assay was developed to detect AZT within minutes. Three different probes designed to release fluorophores when samples containing AZT are added were synthesized and characterized. The limit of detection to AZT in simulated urine samples was determined to be 4 µM in 5 min for one of the probes. This simple and rapid point-of-care test could potentially be used by clinicians and health care workers to monitor the presence of AZT in low resource settings.

Combination of Colistin and Azidothymidine Demonstrates Synergistic Activity against Colistin-Resistant, Carbapenem-Resistant Klebsiella pneumoniae.

Carbapenem-resistant Enterobacteriaceae (CRE) is listed as an urgent threat by the World Health Organization because of the limited therapeutic options, rapid evolution of resistance mechanisms, and worldwide dissemination. Colistin is a common backbone agent among the "last-resort" antibiotics for CRE; however, its emerging resistance among CRE has taken the present dilemma to the next level. Azidothymidine (AZT), a thymidine analog used to treat human immunodeficiency virus/acquired immunodeficiency syndrome, has been known to possess antibacterial effects against Enterobacteriaceae. In this study, we investigated the combined effects of AZT and colistin in 40 clinical isolates of colistin-resistant, carbapenem-resistant K. pneumoniae (CCRKP). Eleven of the 40 isolates harbored Klebsiella pneumoniae carbapenemase. The in vitro checkerboard method and in vivo nematode killing assay both revealed synergistic activity between the two agents, with fractional inhibitory concentration indexes of ≤0.5 in every strain. Additionally, a significantly lower hazard ratio was observed for the nematodes treated with combination therapy (0.288; p < 0.0001) compared with either AZT or colistin treatment. Toxicity testing indicated potentially low toxicity of the combination therapy. Thus, the AZT-colistin combination could be a potentially favorable therapeutic option for treating CCRKP.

Effect of Different Media on the Bactericidal Activity of Colistin and on the Synergistic Combination With Azidothymidine Against mcr-1-Positive Colistin-Resistant Escherichia coli.

Antimicrobial susceptibility testing (AST) performed according to defined guidelines is important to identify resistance and to predict the clinical success or failure of specific antibiotic therapy. However, these guidelines do not cover all physiological conditions that can have a tremendous impact on in vivo resistance. In this study, we tested the susceptibility of thirteen mcr-1-positive Escherichia coli strains against colistin, one of the last resort antibiotics for treating multi-drug resistant pathogens, in media recommended for ASTs as well as - physiologically more relevant - in human serum and artificial urine (AU). Minimal inhibitory concentration (MIC) values in heat-inactivated human serum were similar to those in cation-adjusted Mueller-Hinton broth (CAMHB), but reduced in native serum for almost all strains that could grow in this media. In AU MIC values for mcr-1 positive E. coli were increased significantly up to 16-fold compared to that in CAMBH, which did not apply to the colistin-susceptible E. coli strains tested. Although different growth media could affect the MIC of colistin alone, their impact on the synergistic effect of the combination with the antiviral drug azidothymidine was minimal. The higher divalent cation concentration combined with acidic pH values is most likely responsible for the increased MIC values of the mcr-1 harboring E. coli strains tested against colistin in AU compared to that in CAMHB. Antimicrobial susceptibility screening procedures for colistin using CAMHB only could lead to an underestimation of resistance under different physiological conditions. Therefore, not only pharmacokinetic but also pharmacodynamic studies in urine are as important as in serum or plasma.

The Anticancer Efficacy of Platinum Azidothymidin on Hepatocellular Carcinoma Via Affecting the Telomerase and the BcL-2 Genes Expression.

PURPOSE: The study of correlation between cancer biomarkers after treatment with anticancer drugs would represent a promising insight into the effectiveness of the drug. METHODS: In this study, after induction of hepatocellular carcinoma, rats were divided into four groups: groups A and B as healthy or control group and negative untreated cancer group respectively; groups C and D were treated with platinum azido-thymidine (0.9 mg/kg/day), a novel anti-cancer drug, and azido-thymidine (AZT) (0.3 mg/kg/day) respectively. After induction of cancer, the telomerase and Bcl-2 expression were evaluated by real-time PCR (RT-qPCR), and also Bcl-2 concentration and telomerase activity were measured by enzyme-linked immunosorbent assay (ELISA) and telomerase repeat amplification protocol (TRAP) respectively. RESULTS: A significant correlation was observed between telomerase and Bcl-2 in untreated HCC-induced rats as compared to the control group. In untreated cancer group, a direct significant correlation between telomerase activity and expression (r = 0.453, p = 0.022*) and also a negative significant correlation between telomerase activity and Bcl-2 concentration (r = - 0.43, p = 0.034*) and also between telomerase and Bcl-2 expression (r = - 0.088, p = 0.006*) was observed. In drug-treated groups, there was a significant negative correlation between telomerase expression and Bcl-2 concentration (r = - 0.45, p = 0.025) only in the AZT-treated groups. CONCLUSION: Our results indicated a correlation between cancer factors in the untreated cancerous group B and in treated groups only limited to the azithoimidin-treated group (group D). Hence, it may be possible to use this strategy to develop remarkable anticancer drugs in future studies, though this hypothesis requires more in-depth research.

Infectious stress triggers a POLG-related mitochondrial disease.

A 3-year-old girl presented with severe epilepsy in the context of Borrelia infection. After ceftriaxone/lidocaine administration, she showed secondarily generalized focal crises that led to neurological and motor sequelae. Genetic studies identified in the patient two heterozygous POLG mutations (c.2591A>G; p.Asn864Ser and c.3649G>C; p.Ala1217Pro). Through analysis of POLG activity in cultured fibroblasts, we confirmed that the mutations altered the mtDNA turnover. Moreover, patient fibroblasts were more sensitive than controls in the presence of a mitochondrial replication-affecting drug, the antiretroviral azidothymidine. To test if ceftriaxone treatment could worsen the deleterious effect of the patient mutations, toxicity assays were performed. Cell toxicity, without direct effect on mitochondrial respiratory function, was detected at different antibiotic concentrations. The clinical outcome, together with the different in vitro sensitivity to ceftriaxone among patient and control cells, suggested that the mitochondrial disease symptoms were hastened by the infection and were possibly worsened by the pharmacological treatment. This study underscores the benefit of early genetic diagnosis of the patients with mitochondrial diseases, since they may be a target group of patients especially vulnerable to environmental factors.

Increasing the anticancer activity of azidothymidine toward the breast cancer via rational design of magnetic drug carrier based on molecular imprinting technology.

Cancer treatment based anticancer drugs face serious obstacles. To prevail these obstacles, an effective targeted drug carrier can be imperative. This study aimed to design rationally an imprinting strategy for the carrying of a model anticancer drug, Azidothymidine via molecular imprinting technology. Considering the identity and affinity of monomers and cross-linkers to AZT, this work succeeded to establish an exclusive procedure to significantly improve the process of imprinting the Azidothymidine. Imprinting process was carried out on the surface of vinyl-modified silica coated Fe3O4 nanoparticles toward the delivery of azidothymidine to targeted tissue by external magnetic field. The resultant carrier was characterized by FT-IR, XRD, VSM, FESEM, EDX, BET, TGA. The AZT loading process on the nanocarrier is followed with Freundlich adsorption isotherm (QMAX:170 mg/g) and pseudo-second order fast adsorption kinetic (5 min). The release process of AZT from nanocarrier was fitted with First-Order and Higuchi dynamic model. Eventually, the involvement of magnetic nanocarrier was investigated on apoptosis in MCF-7 (cancer cell line) and MCF-10 (normal cell line). The cytotoxicity percentage on MCF-7 cells for magnetic nanocarrier was about 49 times greater than the azidothymidine, but did not affect MCF-10 cells. The corresponding results appropriately disclosed that the cytotoxicity of proposed nanocarrier on MCF-7 cells is through the caspase3 activity. The drug loading and release process as well as in-vitro studies of magnetic carrier were compared with bare carrier. This study indicates that the proposed magnetic carrier can be used as a promising drug carrier toward the breast cancer treatment.

Molecular and structural basis of nucleoside diphosphate kinase-mediated regulation of spore and sclerotia development in the fungus Aspergillus flavus.

The fundamental biological function of nucleoside diphosphate kinase (NDK) is to catalyze the reversible exchange of the γ-phosphate between nucleoside triphosphate (NTP) and nucleoside diphosphate (NDP). This kinase also has functions that extend beyond its canonically defined enzymatic role as a phosphotransferase. However, the role of NDK in filamentous fungi, especially in Aspergillus flavus (A. flavus), is not yet known. Here we report that A. flavus has two NDK-encoding gene copies as assessed by qPCR. Using gene-knockout and complementation experiments, we found that AfNDK regulates spore and sclerotia development and is involved in plant virulence as assessed in corn and peanut seed-based assays. An antifungal test with the inhibitor azidothymidine suppressed AfNDK activity in vitro and prevented spore production and sclerotia formation in A. flavus, confirming AfNDK's regulatory functions. Crystallographic analysis of AfNDK, coupled with site-directed mutagenesis experiments, revealed three residues (Arg-104, His-117, and Asp-120) as key sites that contribute to spore and sclerotia development. These results not only enrich our knowledge of the regulatory role of this important protein in A. flavus, but also provide insights into the prevention of A. flavus infection in plants and seeds, as well as into the structural features relevant for future antifungal drug development.

Urinary bactericidal activity of colistin and azidothymidine combinations against mcr-1-positive colistin-resistant Escherichia coli.

A phase 1 clinical study was performed to assess the pharmacokinetics and safety of intravenous (i.v.) administration of colistin methanesulfonate (CMS) and azidothymidine (AZT) alone and in combination. Seven healthy subjects received three (every 12 h) 1-h i.v. infusions of 4, 2 and 2 million international units (MIU) of CMS co-administered with 200, 100 and 100 mg of AZT, respectively. In an ex vivo study, urinary bactericidal titres (UBTs) and time-kill curve determinations were performed in artificial urine spiked with colistin sulfate and AZT according to median and minimum peak concentrations in urine measured after the first and third dose using four mcr-1-positive colistin-resistant and five colistin-susceptible Gram-negative isolates. Reciprocal UBTs for the different colistin concentrations obtained in urine ranged from 1-128 and 0-2 for colistin-susceptible and colistin-resistant isolates, respectively. Combination with AZT could increase UBTs up to two dilution steps each for the Enterobacteriaceae and Acinetobacter strains tested. In contrast, the combination had no activity against Pseudomonas strains. In time-kill curves, the combination showed bactericidal activity against colistin-resistant strains even when the substances alone were not bactericidal. Thus, combination of CMS with AZT shows promising synergistic activity against Gram-negative uropathogens, including colistin-resistant Enterobacteriaceae. According to the urinary bactericidal activity, a maintenance dosage of 2 MIU of CMS combined with 100 mg of AZT twice daily may be sufficient for the treatment of urinary tract infections (UTIs) caused by colistin-susceptible strains. However, the dosage requires optimisation for efficient treatment of UTIs caused by colistin-resistant strains.

[AntiHIV/AIDS drug 6HP: antiviral activity, pre-clinical study. Efficiency in adult HIV-infected patients.]

The new domestic antiretroviral drug 6HP, which is ammonium-3'-azido-3'-deoxythymidine-5'-carbomoylphosphonate, shows a high level of anti-HIV activity in cultures of lymphoblastoid cells. In a organism, the 6HP is converted to azidothymidine, and the its pharmacokinetic parameters indicate a prolonged nature of action of this compound in vivo. It is an important indicator that allows to formulate optimal therapeutic regimens during clinical application of 6HP. The complex of its antiviral properties and the results of its exhaustive preclinica study, as well as the results of studying its safety and tolerability in adult HIV-infected patients, including important first data of its use as a specific therapeutic antiHIV / AIDS drug, certainly indicate on its prospects and its usefulness in clinical use in patients with HIV infection, including as part of combination antiretroviral therapy.

Synergistic activity of colistin with azidothymidine against colistin-resistant Klebsiella pneumoniae clinical isolates collected from inpatients in Greek hospitals.

BACKGROUND: New antibiotics are urgently needed to treat multi-drug resistant infections; however, production of novel antibiotics is diminishing. Synergistic combination drug therapy to enhance the activity of available antibiotics may improve management of patients with resistant infections. METHODS: Colistin-resistant Klebsiella pneumoniae isolates were collected from inpatients in 10 Greek hospitals and used to study combination activity of colistin plus azidothymidine. Combination activity was evaluated with the sum of fractional inhibitory concentrations (ΣFIC) using the mini checkerboard broth microdilution method. RESULTS: A hundred individual strains were tested. Synergistic activity was noted in 79% (79/100) of isolates and additive activity in the remaining 21% (21/100). ΣFIC50 and ΣFIC90 were 0.28 and 0.56, respectively. CONCLUSION: Colistin with azidothymidine exhibited promising synergistic activity against colistin-resistant Klebsiella pneumoniae isolates warranting further investigation of the combination.