Conditions required for the antibacterial activity of zidovudine

Design and Synthesis of Novel Antimicrobial Agents

The necessity for the discovery of innovative antimicrobials to treat life-threatening diseases has increased as multidrug-resistant bacteria has spread. Due to antibiotics' availability over the counter in many nations, antibiotic resistance is linked to overuse, abuse, and misuse of these drugs. The World Health Organization (WHO) recognized 12 families of bacteria that present the greatest harm to human health, where options of antibiotic therapy are extremely limited. Therefore, this paper reviews possible new ways for the development of novel classes of antibiotics for which there is no pre-existing resistance in human bacterial pathogens. By utilizing research and technology such as nanotechnology and computational methods (such as in silico and Fragment-based drug design (FBDD)), there has been an improvement in antimicrobial actions and selectivity with target sites. Moreover, there are antibiotic alternatives, such as antimicrobial peptides, essential oils, anti-Quorum sensing agents, darobactins, vitamin B6, bacteriophages, odilorhabdins, 18β-glycyrrhetinic acid, and cannabinoids. Additionally, drug repurposing (such as with ticagrelor, mitomycin C, auranofin, pentamidine, and zidovudine) and synthesis of novel antibacterial agents (including lactones, piperidinol, sugar-based bactericides, isoxazole, carbazole, pyrimidine, and pyrazole derivatives) represent novel approaches to treating infectious diseases. Nonetheless, prodrugs (e.g., siderophores) have recently shown to be an excellent platform to design a new generation of antimicrobial agents with better efficacy against multidrug-resistant bacteria. Ultimately, to combat resistant bacteria and to stop the spread of resistant illnesses, regulations and public education regarding the use of antibiotics in hospitals and the agricultural sector should be combined with research and technological advancements.

Repurposing the anti-viral drug zidovudine (AZT) in combination with meropenem as an effective treatment for infections with multi-drug resistant, carbapenemase-producing strains of Klebsiella pneumoniae

Multi-drug resistant (MDR) Klebsiella pneumoniae represent a global threat to healthcare due to lack of effective treatments and high mortality rates. The aim of this research was to explore the potential of administering zidovudine (AZT) in combination with an existing antibiotic to treat resistant K. pneumoniae infections. Two MDR K. pneumoniae strains were employed, producing either the NDM-1 or KPC-3 carbapenemase. Efficacy of combinations of AZT with meropenem were compared with monotherapies against infections in Galleria mellonella larvae by measuring larval mortality and bacterial burden. The effect of the same combinations in vitro was determined via checkerboard and time-kill assays. In vitro, both K. pneumoniae strains were resistant to meropenem but were susceptible to AZT. In G. mellonella, treatment with either AZT or meropenem alone offered minimal therapeutic benefit against infections with either strain. In contrast, combination therapy of AZT with meropenem presented significantly enhanced efficacy compared to monotherapies. This was correlated with prevention of bacterial proliferation within the larvae but not elimination. Checkerboard assays showed that the interaction between AZT and meropenem was not synergistic but indifferent. In summary, combination therapy of AZT with meropenem represents a potential treatment for carbapenemase-producing MDR K. pneumoniae and merits further investigation.

In-utero triple antiretroviral exposure associated with decreased growth among HIV-exposed uninfected infants in Botswana

OBJECTIVE

To assess associations between in-utero triple antiretrovirals (cART) versus zidovudine (ZDV) monotherapy exposure and growth among HIV-uninfected children of HIV-infected women in Botswana.

DESIGN

Secondary retrospective data analysis from two randomized intervention trials of mother-to-child HIV transmission prevention.

METHODS

The Mashi and Mma Bana studies enrolled HIV-infected pregnant women, following their children through 24 months of age. This analysis includes singleton, full-term, HIV-exposed uninfected children. Mothers received cART or ZDV at least 2 weeks predelivery, and breastfed up to 6 months. Weight-for-age (WAZ), length-for-age (LAZ) and weight-for-length (WLZ) z-scores were derived. Mean z-scores were compared by exposure group at 24 months (t-test, linear regression).

RESULTS

Of 819 children, 303 were ZDV- and 516 cART-exposed in utero. Maternal median enrolment CD4 was higher among ZDV versus cART-treated mothers (393 versus 324 cells/μl; P < 0.0001). Median duration of antepartum antiretroviral use was shorter among ZDV-treated women (5.7 versus 12.0 weeks; P < 0.0001). Median months breastfed were similar (5.9 and 6.0; P = 0.43). At 24 months, mean LAZ and WAZ were significantly lower among cART-exposed children (LAZ -1.01 versus -0.74; P = 0.003) (WAZ -0.53 versus -0.30; P = 0.002) in unadjusted analyses. Adjusting for maternal CD4, viral load, enrolment site and maternal anthropometric measures, cART-exposed children had significantly lower LAZ and WAZ at 24 months (P = 0.0004 for both).

CONCLUSION

At 24 months, in-utero cART-exposed children had significantly lower LAZ and WAZ. Poor growth impacts childhood and adult mortality. These findings raise concerns for potential lasting health impacts among HIV-exposed uninfected children with in-utero cART exposure.

The effect of thymidine on the antibacterial and antiviral activity of zidovudine

The effect of thymidine and deoxyadenosine on the antiviral and antibacterial effect of zidovudine was studied in human immunodeficiency virus type 1 (HIV-1) Escherichia coli and Salmonella typhimurium. In quantitative assays, 10 μg mL−1 thymidine was shown to increase the 50% inhibitory concentration (IC50) of zidovudine for HIV-1 by approximately 100-fold and to reduce zidovudine (1 μm)-induced protection of C8166 cells from 204 to 0·18 log syncytial-forming units. Thymidine also antagonized the antibacterial effect of zidovudine for two E. coli and three S. typhimurium species in a dose-dependent manner; 10 μg mL of thymidine increased the minimum inhibitory concentration of zidovudine for E. coli strains by 10–40-fold and for S. typhimurium strains by three-fold. Deoxyadenosine reduced the minimum inhibitory concentration of zidovudine against all five bacterial strains but had no effect on the IC50 of zidovudine for HIV-1, nor did it significantly reverse the antagonism of the antibacterial and antiviral activity of thymidine. The induction of the SOS response in E. coli was reversed in a dose-dependent manner by thymidine while the presence of deoxyadenosine increased induction of the SOS response by zidovudine at suboptimal concentrations.

Purification and properties of theEscherichia colinucleoside transporter NupG, a paradigm for a major facilitator transporter sub-family

NupG from Escherichia coli is the archetype of a family of nucleoside transporters found in several eubacterial groups and has distant homologues in eukaryotes, including man. To facilitate investigation of its molecular mechanism, we developed methods for expressing an oligohistidine-tagged form of NupG both at high levels (>20% of the inner membrane protein) in E. coli and in Xenopus laevis oocytes. In E. coli recombinant NupG transported purine (adenosine) and pyrimidine (uridine) nucleosides with apparent K(m) values of approximately 20-30 microM and transport was energized primarily by the membrane potential component of the proton motive force. Competition experiments in E. coli and measurements of uptake in oocytes confirmed that NupG was a broad-specificity transporter of purine and pyrimidine nucleosides. Importantly, using high-level expression in E. coli and magic-angle spinning cross-polarization solid-state nuclear magnetic resonance, we have for the first time been able directly to measure the binding of the permeant ([1'-(13)C]uridine) to the protein and to assess its relative mobility within the binding site, under non-energized conditions. Purification of over-expressed NupG to near homogeneity by metal chelate affinity chromatography, with retention of transport function in reconstitution assays, was also achieved. Fourier transform infrared and circular dichroism spectroscopy provided further evidence that the purified protein retained its 3D conformation and was predominantly alpha-helical in nature, consistent with a proposed structure containing 12 transmembrane helices. These findings open the way to elucidating the molecular mechanism of transport in this key family of membrane transporters.

Synthesis and in vitro antibacterial activity of novel 5'-O-analog derivatives of zidovudine as potential prodrugs

An efficient, short synthesis of four potential prodrugs of 3'-azido-3'-deoxythymidine (AZT) and their antibacterial activity are reported. The 5'-OH group of AZT was functionalized with oxalyl chloride obtaining an acyl chloride derivative (AZT-Ox), which by further transformation with leucine, isoleucine and valine amino acids led to the corresponding AZT analogs, namely AZT-Leu, AZT-iLeu and AZT-Val. A carboxyl acid derivative (AZT-Ac) was also obtained by hydrolysis of AZT-Ox. These compounds, which exhibit anti HIV activity, have killed collection and clinical strains of some opportunistic infectious agents in AIDS-related complex. Thus, the clinical strains, K. oxytoca, S. typhi and K. pneumoniae, and collection strain K. pneumoniae ATCC 10031 showed sensitivity to antibiotics. The activity order for the studied compounds against the most sensitive strain (K. pneumoniae ATCC 10031) was AZT-Leu > AZT-iLeu > AZT-Val > AZT-Ac > AZT. On the other hand, the activity order for the second most sensitive strain (K. oxytoca) was AZT-Leu > AZT-Val = AZT-Ac > AZT-iLeu > AZT. The most effective antibacterial drug AZT-Leu, M.I.C.=0.125 microgmL(-1)) was 16 times more active than AZT (AZT, M.I.C.=2 microg mL(-1)) against K.

The effects of disease progression and zidovudine therapy on semen quality in human immunodeficiency virus type 1 seropositive men

OBJECTIVE

To investigate the effects of disease progression and zidovudine antiretroviral therapy on semen parameters in human immunodeficiency virus type 1 (HIV-1) seropositive men.

DESIGN

Cross-sectional analysis of semen parameters of 166 HIV-1 seropositive men in various stages of disease progression as defined by peripheral CD4+ cell count. Clinical symptoms and zidovudine therapy status were obtained from medical records and clinical interviews.

PATIENTS

Human immunodeficiency virus type 1 seropositive men participating in clinical studies at the Fenway Community Health Center (Boston, MA), the University of San Francisco (San Francisco, CA), and Brown University (Providence, RI).

MAIN OUTCOME MEASURES

Ejaculate volume; sperm concentration, motility, forward progression, morphology, total sperm count; seminal immature germ cell; and white blood cell (WBC) concentrations.

RESULTS

Human immunodeficiency virus type 1 seropositive men that were not on zidovudine therapy and were in early disease stage (> 200 CD4+ cells/mm3) had normal semen parameters as defined by World Health Organization criteria. In contrast untreated men in advanced disease stage (< or = 200 CD4+ cells/mm3) had significant reductions in sperm concentration and total sperm count and an increased percentage of abnormal sperm forms. Men receiving zidovudine antiretroviral therapy, regardless of disease stage, had normal semen parameters similar to those of untreated early disease stage patients. Seminal WBC concentrations were not affected significantly by disease progression but were reduced in patients receiving zidovudine.

CONCLUSION

Most HIV-1-infected men in this study had semen parameters consistent with fertility. Disease progression was associated with reduced semen quality, but this effect appeared to be abrogated by zidovudine therapy. Zidovudine was also associated with a significant reduction of WBC numbers in semen. As seminal WBC are principal HIV-1 host cells in ejaculates of HIV-1-infected men, this effect could explain recent laboratory and epidemiological evidence that zidovudine therapy is associated with a reduced prevalence of HIV-1 in semen and a lower rate of sexual transmission.

In vitro activity of zidovudine alone and in combination with ciprofloxacin against Salmonella and Escherichia coli

The in vitro antibacterial activity of zidovudine alone and in combination with ciprofloxacin was investigated. Zidovudine showed a good activity against Escherichia coli and Salmonella (MIC range 0.5-8 micrograms/ml and 1.5-62 micrograms/ml respectively) isolated from biological samples of HIV-infected patients. These strains proved to be extremely susceptible to ciprofloxacin alone. The interaction between zidovudine and ciprofloxacin ranged from additive activity to indifference. No antagonism was observed: the FIC index for every combination resulted < or = 1.5. The addition of AZT 1 mg/l (clinically achievable plasma concentration after therapeutic doses of 1200 mg/day) did not affect the bactericidal activity of ciprofloxacin; on the contrary, in some cases we observed an increase of bactericidal effect of the quinolone. These data have to be considered in patients with AIDS who can be treated concomitantly with zidovudine and ciprofloxacin.

In vitro activities of nucleoside analog antiviral agents against salmonellae

Zidovudine (ZDV) has antibacterial activity against many members of the family Enterobacteriaceae, including Salmonella species, and may be responsible for a decrease in the frequency of salmonellosis in persons infected with human immunodeficiency virus (HIV). Other nucleoside analogs, such as didanosine (2',3'-dideoxyinosine [ddI]) and zalcitabine (2',3'-dideoxycytidine [ddC]), which have undefined anti-salmonella activity, increasingly are being used in the treatment of HIV infection. To evaluate the anti-Salmonella activity of the antiviral agents ZDV, ddI, ddC, and acyclovir (ACV), we determined MICs for 39 nontyphoidal Salmonella blood isolates. ZDV (MIC for 50% of strains tested [MIC50], 0.5 microgram/ml; MIC range, 0.125 to 4 micrograms/ml) and ddI (MIC50, 8 micrograms/ml; MIC range, 2 to 125 micrograms/ml) had concentration-dependent activity. Anti-Salmonella activity was not observed for ddC or ACV. Nine Escherichia coli blood isolates were inhibited by ZDV (MIC50, 0.125 microgram/ml; MIC range, 0.031 to 1 microgram/ml) to a greater degree than they were by ddI (MIC50, 62.5 micrograms/ml; MIC range, 31 to > 62.5 micrograms/ml). Inoculum size affected susceptibility to ZDV and ddI for Salmonella and E. coli isolates. Resistance to ZDV or to ddI could be induced in vitro in Salmonella isolates, but cross-resistance was not observed. These results indicate that at concentrations achieved during the treatment of HIV infection, ZDV has activity against nontyphoidal salmonellae, although resistance can develop. ddI, ddC, and ACV at currently used dosages would not be expected to be effective in the prevention or treatment of Salmonella infections.

Intracellular activity of zidovudine (3'-azido-3'-deoxythymidine, AZT) against Salmonella typhimurium in the macrophage cell line J774-2

The antibacterial effect of zidovudine (AZT) has been demonstrated both in vitro and in vivo with experimental models of gram-negative bacterial infections. It has been associated with the absence or low occurrence of nontyphoid Salmonella infections in AIDS patients treated with AZT. Using the macrophage cell line J774-2, we demonstrate the inhibition of intracellular growth of Salmonella typhimurium by AZT. This effect is obtained with one-half of the MIC (1 microgram/ml) of AZT for S. typhimurium. Inhibition of intracellular growth is observed after 4 h of incubation and persists at 24 h. Maximal inhibition is shown at a concentration of 128 micrograms/ml, and no further effect is observed with higher concentrations. When the inhibitory effect of AZT is compared with that of pefloxacin or that of ceftriaxone at half their MICs (0.2 and 0.02 microgram/ml, respectively), AZT and pefloxacin give better results than ceftriaxone. In this study, using an intracellular model, we show that AZT is able to inhibit the intracellular multiplication of S. typhimurium at a minimal effective concentration lower than the MIC, indicating its potential for antibacterial accumulation in the macrophages.

Isolation of zidovudine resistant Escherichia coli from AIDS patients

Zidovudine-resistant Escherichia coli were isolated from faecal samples from 6 out of 11 AIDS patients receiving zidovudine. Resistance appeared to be due to the loss of thymidine kinase activity which is required for the phosphorylation of zidovudine to its active form. No zidovudine resistant enterobacteria were isolated from 30 control faecal samples. Hence, clinically, there appeared to be a high correlation between the development of zidovudine-resistance in E. coli and exposure to zidovudine (chi 2: 11.77, P less than 0.001). However the development of zidovudine resistance does not appear to be associated with cross-resistance to other antimicrobial agents as the zidovudine-resistant E. coli did not display a high degree of resistance to other antibacterials.