A bionanohybrid ZnAl-NADS ecological pesticide as a treatment for soft rot disease in potato (Solanum tuberosum L.).

Pectobacterium carotovorum (Pc) is a phytopathogenic strain that causes soft rot disease in potato (Solanum tuberosum L.), resulting in postharvest losses. Chemical control is effective for managing this disease, but overdoses cause adverse effects. Because farmers insist on using chemical agents for crop protection, it is necessary to develop more effective pesticides in which the active compound released can be regulated. In this context, we proposed the synthesis of ZnAl-NADS, in which nalidixic acid sodium salt (NADS) is linked to a ZnAl-NO3 layered double hydroxide (LDH) host as a nanocarrier. XRD, FT-IR, and SEM analyses confirmed the successful intercalation of NADS into the interplanar LDH space. The drug release profile indicated that the maximum release was completed in 70 or 170 min for free NADS (alone) or for NADS released from ZnAl-NADS, respectively. This slow release was attributed to strong electrostatic interactions between the drug and the anion exchanger. A modulated release is preferable to the action of the bulk NADS, showing increased effectiveness and minimizing the amount of the chemical available to pollute the soil and the water. The fitting data from modified Freundlich and parabolic diffusion models explain the release behavior of the NADS, suggesting that the drug released from ZnAl-NADS bionanohybrid was carried out from the interlamellar sites, according to the ion exchange diffusion process also involving intraparticle diffusion (coeffect). ZnAl-NADS was tested in vitro against Escherichia coli (Ec) and Pc and exhibited bacteriostatic and biocidal effects at 0.025 and 0.075 mg mL-1, respectively. ZnAl-NADS was also tested in vivo as an ecological pesticide for combating potato soft rot and was found to delay typical disease symptoms. In conclusion, ZnAl-NADS can potentially be used to control pests, infestation, and plant disease.

Characterization of antimicrobial resistance markers & their stability in Salmonella enterica serovar Typhi.

BACKGROUND & OBJECTIVES: Typhoid fever is a major cause of morbidity and mortality in the developing countries including India. Resistance to multiple antimicrobial agents is an emerging global problem that has serious impact on the treatment of disease. There are many factors associated with the emergence of resistance. Most important of them is the acquisition and further transmission and spread of resistance markers among various bacterial species. Therefore, we conducted this study to characterize the resistance plasmids in terms of their transferability and stability among Salmonella enterica serovar Typhi. METHODS: Six multidrug-resistant S. Typhi isolates were evaluated for the stability and transfer of resistance markers. The resistance plasmids were also checked for the presence of RepHI1A replicon. RESULTS: All resistance markers were found to be transferred to the recipient through conjugation and transformation, except for nalidixic acid. None of the resistance plasmid was found to harbour RepHI1A replicon and therefore, did not belong to incompatibility group IncHI1. Resistance markers were found to be highly stable in all the isolates during serial passages and storage as stab cultures at different temperatures for different time periods. INTERPRETATION & CONCLUSIONS: Resistance markers for chloramphenicol, ampicillin, streptomycin and trimethoprim were transferred through conjugation as well as transformation whereas that for nalidixic acid was not transferred in any of the isolates. Markers for chloramphenicol and streptomycin resistance were found to be most stable during various storage conditions. Presence of small-sized non-IncHI1 resistance plasmids is a matter of concern due to their capability to exist inside the host, thereby increasing the possibility of their transmission and spread among S. Typhi and other bacterial species.

Synergy Potential of Indole Alkaloids and Its Derivative against Drug-resistant Escherichia coli.

Antibacterial and synergy potential of naturally occurring indole alkaloids (IA): 10-methoxy tetrahydroalstonine (1), isoreserpiline (2), 10 and 11 demethoxyreserpiline (3), reserpiline (4), serpentine (5), ajmaline (6), ajmalicine (7), yohimbine (8), and α-yohimbine (9) was evaluated using microbroth dilution assay. Further, α-yohimbine (9) was chemically transformed into six semisynthetic derivatives (9A-9F), and their antibacterial and synergy potential in combination with nalidixic acid (NAL) against E. coli strains CA8000 and DH5α were also evaluated. The IA 1, 2, 4, 5, 9 and the derivative 9F showed eightfold reduction in the MIC of NAL against the DH5α and four- to eightfold reduction against CA8000. These alkaloids also reduced MIC of another antibiotic, tetracycline up to 8folds, against the MDREC-KG4, a multidrug-resistant clinical isolate of E. coli. Mode of action study of these alkaloids showed efflux pumps inhibitory potential, which was supported by their in silico binding affinity and downregulation of efflux pump genes. These results may be of great help in the development of cost-effective antibacterial combinations for treating patients infected with multidrug-resistant Gram-negative infections.

Typhoid Fever in an inner city hospital: a 5-year retrospective review.

BACKGROUND: Typhoid is a leading cause of fever in returning travelers. The prevalence is highest in migrants visiting friends and relatives (VFR travelers) in the Indian subcontinent, where reports of resistance have been of concern. This study is a retrospective analysis of patients with typhoid, seen over a 5-year period, in a tertiary center that serves a large immigrant population. METHODS: Patients with blood cultures positive for Salmonella Typhi were identified between 2006 and 2010. Charts were reviewed for demographic data, travel history, symptoms and signs, basic laboratory results, susceptibility profiles, treatment, and clinical course. Resistance to nalidixic acid was used as a marker of decreased susceptibility to quinolones. RESULTS: Seventeen patients were identified with S Typhi. The median age was 12 years (range: 2-47 y) and 94% (16 of 17) were hospitalized with a median stay of 7 days; two were admitted to the intensive care unit. Fourteen patients (82%) had a history of recent travel. Twelve were VFR travelers in Bangladesh and Pakistan and two had recently immigrated. In our study, typhoid patients had low eosinophil counts and elevated transaminases. Seventy-six percent (12 of 17) of all isolates were resistant to nalidixic acid, 23.5% (4 of 17) were resistant to ampicillin and co-trimoxazole, and one was resistant to ciprofloxacin. All isolates were susceptible to third-generation cephalosporins. CONCLUSIONS: Younger VFR travelers appear to be at greater risk of acquiring infection and developing complications. Absolute eosinopenia and increased liver function test values could be useful early diagnostic clues in a returning traveler with fever, once malaria has been excluded. There was a high rate of decreased susceptibility to fluoroquinolones, confirming that the use of third-generation cephalosporins or macrolides in patients from the Indian subcontinent is most appropriate. Prevention in VFR travelers to South Asia is critical and efforts should be targeted at better education and pre-travel immunization.

Infection-responsive drug delivery from urinary biomaterials controlled by a novel kinetic and thermodynamic approach.

PURPOSE: The pH-dependent physicochemical properties of the antimicrobial quinolone, nalidixic acid, were exploited to achieve 'intelligent' drug release from a potential urinary catheter coating, poly(2-hydroxyethylmethacrylate) (p(HEMA)), in direct response to the elevated pH which occurs at the onset of catheter infection. METHODS: p(HEMA) hydrogels, and reduced-hydrophilicity copolymers incorporating methyl methacrylate, were loaded with nalidixic acid by a novel, surface particulate localization method, and characterized in terms of pH-dependent drug release and microbiological activity against the common urease-producing urinary pathogen Proteus mirabilis. RESULTS: The pH-dependent release kinetics of surface-localized nalidixic acid were 50- and 10-fold faster at pH 9, representing the alkaline conditions induced by urease-producing urinary pathogens, compared to release at pH 5 and pH 7 respectively. Furthermore, microbiological activity against P. mirabilis was significantly enhanced after loading surface particulate nalidixic acid in comparison to p(HEMA) hydrogels conventionally loaded with dispersed drug. The more hydrophobic methyl methacrylate-containing copolymers also demonstrated this pH-responsive behavior, but additionally exhibited a sustained period of zero-order release. CONCLUSIONS: The paradigm presented here provides a system with latent, immediate infection-responsive drug release followed by prolonged zero-order antimicrobial delivery, and represents an 'intelligent', infection-responsive, self-sterilizing biomaterial.

Synthesis and evaluation of uniformly sized nalidixic acid-imprinted nanospheres based on precipitation polymerization method for analytical and biomedical applications.

For the first time in this work, uniform molecularly imprinted polymer (MIP) nanoparticles were prepared using nalidixic acid as a template. The MIP nanoparticles were successfully synthesized by precipitation polymerization applying methacrylic acid (MAA) as a functional monomer and trimethylolpropane trimethacrylate (TRIM) as a cross-linking monomer at different mole ratios. The morphology, binding, recognition, selectivity, and in vitro release behaviors of obtained particles were studied. The produced polymers were characterized by Fourier transform infrared spectroscopy and differential scanning calorimetric. Furthermore, their morphology was analyzed accurately by scanning electron microscopy, photon correlation spectroscopy, and Brunauer-Emmett-Teller analysis. The nanospheres and microspheres with mean diameter values of 94 nm, 256 nm, and 1.2 µm were obtained using nalidixic acid-MAA-TRIM various mole ratios. Among the MIPs, the product with nalidixic acid-MAA-TRIM mole ratio of 1:12:12 established nanospheres with the lowest polydispersity index (0.003), an average pore diameter (12 nm), and the highest specific surface area (280 m(2) g(-1)) and selectivity factor (10.4). Results from binding experiments demonstrated that the imprinted nanospheres with a 94-nm mean diameter and a binding capacity of 28 mg of nalidixic acid per gram of polymer had higher specific affinity to nalidixic acid in contrast with the other imprinted nanospheres, microspheres, and nonimprinted particles. However, the binding performance of imprinted nanospheres in human serum was estimated using high-performance liquid chromatography analysis (binding approximately 98% of nalidixic acid). In addition, release experiments proved to be successful in the controlled release of nalidixic acid during a long period. The 20% of loaded nalidixic acid was released from the imprinted nanospheres within the first 20 h, whereas the remaining 80% was released in the after 120 h. The nalidixic acid release kinetics from the MIPs was highly affected by properties of the particles.

Effect of nalidixic acid on the morphology and protein expression of Pseudomonas aeruginosa.

OBJECTIVE: To determine the effect of nalidixic acid on the morphology and protein expression of Pseudomonas aeruginosa (P. aeruginosa). METHODS: Nalidixic acid solution of 1 600 µg/mL was prepared. The minimum inhibitory concentration (MIC) for P. aeruginosa was determined with tube dilution test. The effect of nalidixic acid on the morphology of P. aeruginosa was studied using light microscope and scanning electron microscope. Changes in protein profile were studied using SDS-PAGE. RESULTS: The MIC of nalidixic acid was 700 µg/mL against P. aeruginosa. The exposure of P. aeruginosa to different concentrations of nalidixic acid resulted in deformation of most of the growing cells. At the concentration of 600 µg/mL most of the cells turned into elongated and adhere to each other while some of the cells were bulged. The intensity of protein bands were changed when they exposed to nalidixic acid. CONCLUSIONS: The present findings suggest that the morphology and protein expression of P. aeruginosa is greatly affected by nalidixic acid.

Trends in antimicrobial resistance in Shigella species in Karachi, Pakistan.

BACKGROUND: Shigellosis is a common cause of morbidity, especially in the very young and old, in developing countries. The disease is treated with antibiotics. Surveillance of antimicrobial resistance trends is essential owing to the global emergence of antimicrobial resistance. METHODOLOGY: The study involved 1,573 isolates of Shigella species (1996-2007) that were analyzed for trends in antimicrobial resistance. RESULTS: The majority of the specimens (1046; 66.5%) were from the pediatric population, and of these 887 (84.8%) were under 5 years of age (p = 0.001). S. flexineri was the most frequent species (54.5%) isolated. Isolation of S. sonnei increased from 15.4 % (1996) to 39% (2007) (p = 0.001). Although none of the isolates was found sensitive to all the antibiotics tested, 58% (n =9 07) were resistant to ampicillin and 85% (n = 1,338) were resistant to trimethoprim-sulfamethoxazole (TMP-SMX). Out of a total of 198 (12.6%) nalidixic acid resistant isolates, 6 (3.0%) were also resistant to ofloxacin. Overall 1.7 % of isolates were resistant to ofloxacin, 2.4% to ceftriaxone and 2.3% were resistant to combination of ampicillin, nalidixic acid and TMP-SMX. CONCLUSION: Ofloxacin is still an effective drug for treatment of acute shigellosis in Pakistan. Emergence of resistance to ceftriaxone in Shigella may have grave implications in treatment of severe shigellosis in very young patients.

Modeling and measurement of a whole-cell bioluminescent biosensor based on a single photon avalanche diode.

Whole-cell biosensors are potential candidates for on-line and in situ environmental monitoring. In this work we present a new design of a whole-cell bioluminescence biosensor for water toxicity detection, based on genetically engineered Escherichia coli bacteria, carrying a recA::luxCDABE promoter-reporter fusion. Sensitive optical detection is achieved using a single photon avalanche photodiode (SPAD) working in the Geiger mode. The present work describes a simple mathematical model for the kinetic process of the bioluminescence based SOS toxin response of E. coli bacteria. We find that initially the bioluminescence signal depends on the time square and we show that the spectral intensity of the bioluminescence signal is inverse proportional to the frequency. We get excellent agreement between the theoretical model and the measured light signal. Furthermore, we present experimental results of the bioluminescent signal measurement using a SPAD and a photomultiplier, and demonstrate improvement of the measurement by applying a matched digital filter. Low intensity bioluminescence signals were measured after the whole-cell sensors were exposed to various toxicant concentrations (5, 15 and 20ppm).

Efficient approach to acyloxymethyl esters of nalidixic acid and in vitro evaluation as intra-ocular prodrugs.

Various alkylcarbonyloxymethyl esters of nalidixic acid ranging from 3 to 15 carbon units in the pro-moiety have been prepared and assessed as potential prodrugs. Their chromatographic retention factors k', silicone oil solubilities and in vitro conversion to nalidixic acid by a commercial esterase were determined together with their in vitro antimicrobial activity and cytotoxicity. The preliminary results suggest that silicone oil may have potential for the intra-ocular delivery of antibacterial compounds. Moreover, the in vitro release rate can be controlled by the lipophilicity of the prodrug.

Biodegradable polymer releasing antibiotic developed for drainage catheter of cerebrospinal fluid: in vitro results.

The authors developed a biodegradable polymer that releases an antibiotic (nalidixic acid) slowly and continuously, for prevention of catheter-induced infection during drainage of cerebrospinal fluid. We investigated the in vitro antibiotic releasing characteristics and bacterial killing effects of the new polymer against E. coli. The novel fluoroquinolone polymer was prepared using diisopropylcarbodiimide, poly (e-capro-lactone) diol, and nalidixic acid. FT-IR, mass spectrometry, and elemental analysis proved that the novel antibacterial polymer was prepared successfully without any side products. Negative MS showed that the released drug has a similar molecular weight (M.W.=232, 350) to pure drug (M.W.=232). In high pressure liquid chromatography, the released drug and drug-oligomer showed similar retention times (about 4.5-5 min) in comparison to pure drug (4.5 min). The released nalidixic acid and nalidixic acid derivatives have antibacterial characteristics against E. Coli, Staphylococcus aureus, and Salmonella typhi, of more than 3 months duration. This study suggests the possibility of applying this new polymer to manufacture drainage catheters that resist catheter-induced infection, by delivering antibiotics for a longer period of more than 1 month.

Biodegradable Polymer Releasing Antibiotic Developed for Drainage Catheter of Cerebrospinal Fluid:In Vitro Results

The authors developed a biodegradable polymer that releases an antibiotic (nalidixic acid) slowly and continuously, for prevention of catheter-induced infection during drainage of cerebrospinal fluid. We investigated the in vitro antibiotic releasing characteristics and bacterial killing effects of the new polymer against E. coli. The novel fluoroquinolone polymer was prepared using diisopropylcarbodiimide, poly (e-capro-lactone) diol, and nalidixic acid. FT-IR, mass spectrometry, and elemental analysis proved that the novel antibacterial polymer was prepared successfully without any side products. Negative MS showed that the released drug has a similar molecular weight (M.W.=232, 350) to pure drug (M.W.=232). In high pressure liquid chromatography, the released drug and drug-oligomer showed similar retention times (about 4.5-5 min) in comparison to pure drug (4.5 min). The released nalidixic acid and nalidixic acid derivatives have antibacterial characteristics against E. Coli, Staphylococcus aureus, and Salmonella typhi, of more than 3 months duration. This study suggests the possibility of applying this new polymer to manufacture drainage catheters that resist catheter-induced infection, by delivering antibiotics for a longer period of more than 1 month.

Studies on molecular interactions between nalidixic acid and liposomes.

The interaction between nalidixic acid sodium salt (NANa) and liposomes prepared from alpha-L-dipalmitoyl-phosphatidylcholine (DPPC) or from its binary mixture with dioleoyl-phosphatidylcholine (DOPC) was studied with differential scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) spectroscopy. We evaluated the role of broadband ultraviolet-B (UV-B) irradiation on the molecular interactions between the lipids and the NANa, and determined the decay-kinetics of the incorporated spin labeled fatty-acid free radicals. Multilamellar and unilamellar vesicles were prepared by sonication and extrusion. The entrapment efficiencies were determined spectrophotometrically. The size-distribution of the liposomes and its change in time was checked by dynamic light scattering (DLS). Our results indicate that NANa mainly interacts with lipid head groups. However, its effect and presumably the formation of the free radicals, induced by broadband ultraviolet-B, is not localized only to the head group region of the lipid molecules. Depending on DOPC content, interaction between the NANa and the lipids modifies the phase-transition parameters of the liposome dispersions.

Azithromycin as an alternative to nalidixic acid in the therapy of childhood shigellosis.

In an outbreak of shigellosis in a kibbutz in Northeastern Israel, oral nalidixic acid failed clinically in 35% and microbiologically in 28.4% of 14 children as compared with no clinical and microbiologic failure in 25 children who were treated with oral azithromycin (P < 0.01 and 0.012, respectively). Thus azithromycin could be a suitable alternative to nalidixic acid.

Nalidixic acid susceptibility test to screen ciprofloxacin resistance in Salmonella typhi.

BACKGROUND & OBJECTIVES: Clinical non response to ciprofloxacin therapy in enteric fever is increasingly being encountered in endemic areas possibly due to the increase in the levels of resistance to ciprofloxacin in Salmonella typhi. The antimicrobial susceptibility tests for S. typhi performed by the disc diffusion method using NCCLS breakpoints fail to detect the increasing MIC of ciprofloxacin, leading to the inappropriate treatment of enteric fever with ciprofloxacin. We explored the possibility of testing S. typhi strains for their susceptibility to nalidixic acid by disc diffusion method as a marker for high MIC to ciprofloxacin. METHODS: Isolates (94) of S. typhi were tested for in vitro susceptibility to nalidixic acid (30 micrograms) and ciprofloxacin (5 micrograms) by disc diffusion method using NCCLS guidelines. The MIC of these strains to ciprofloxacin was also determined by E-test. RESULTS: Of the 94 strains tested, 56 were NARST (nalidixic acid resistant S. typhi) and 34 were NASST (nalidixic acid sensitive S. typhi). MIC of ciprofloxacin in the NASST strains varied from 0.002-0.125 microgram/ml while that for NARST strains varied from 0.023-0.38 microgram/ml, which is about 10-folds higher than that of NASST strains. INTERPRETATION & CONCLUSION: Our study shows that resistance to nalidixic acid is associated with a high MIC to ciprofloxacin in S. typhi. These strains would have been interpreted as ciprofloxacin sensitive by routine antimicrobial susceptibility testing by disc diffusion method. Hence screening of S. typhi isolates by the nalidixic acid susceptibility test may be incorporated in a clinical bacteriology laboratory to alert the treating physicians of the possibility of the failure to ciprofloxacin therapy in patients with enteric fever.

A bioassay evaluation of the urinary antibacterial efficacy of low dose prophylactic antibiotics in children with vesicoureteral reflux.

PURPOSE: We evaluated by means of a bioassay the efficacy of 4 different antibiotics administered in a prophylactic dose to children with vesicoureteral reflux. MATERIALS AND METHODS: A total of 159 urine samples from 53 children taking prophylactic antibiotics with proved vesicoureteral reflux were tested. The children were divided into 4 groups according to the antibiotic given, which included nalidixic acid, cephalexin, cotrimoxazole and cefixime. Urine samples were collected in the morning, at noon and in the evening, and each sample was bioassayed for growth inhibition of a standard Escherichia coli. The urine volume used was specifically determined for each antibiotic, and growth inhibition by this specific volume was equivalent to that produced by standard diffusion disks. In addition, the specific gravity, which reflected urinary concentration of each sample, was measured. RESULTS: Mean patient age plus or minus standard deviation of the 4 groups was 53 +/- 41 for nalidixic acid, 23 +/- 34 for cephalexin, 55 +/- 35 for cotrimoxazole and 47 +/- 35 months for cefixime, respectively. In children less than 2 years old specific gravity was higher in the morning (1.021 +/- 0.0006 versus 1.0008 +/- 0.0004 at 8 a.m. and 2 p. m., respectively, p <0.05). In contrast, in children older than 4 years the specific gravity was higher in the afternoon and evening hours (1.019 +/- 0.003 versus 1.007 +/- 0.003 at 2 p.m. and 8 a.m., respectively, p <0.05). The percentage of patients who demonstrated growth inhibition in all 3 samples of the test day was 7%, 6%, 69% and 44% for nalidixic acid, cephalexin, cotrimoxazole and cefixime, respectively (p <0.001 for cotrimoxazole and cefixime versus nalidixic acid and cephalexin. Divided into morning, noon and evening, the percentage of samples that demonstrated growth inhibition was 85.7%, 21.4% and 7.1% for nalidixic acid, 37.5%, 12. 5% and 6.3% for cephalexin, 100%, 92.3% and 76.9% for cotrimoxazole and 100%, 77.7% and 55.5% for cefixime, respectively. A direct correlation was found between specific gravity and growth inhibition (r = 0.55, p <0.001). CONCLUSIONS: Urine concentration during the day is dependent on age with older children having more concentrated urine in the latter part of the day. Growth inhibition is enhanced by concentrated urine. Compared to nalidixic acid and cephalexin, cotrimoxazole and cefixime produce a sustained bactericidal effect for about 60% of a 24-hour day due to the longer half-life.

Nalidixic acid induced pseudotumour cerebri in children.

Nalidixic acid, the quinolone frequently used in the treatment of acute dysentery, is now emerging as an important cause of pseudotumour cerebri in infants and young children. A study of 20 such cases showed that all the patients had received a higher than recommended dose of nalidixic acid and that 85% of them were given the drug unnecessarily (i.e., for acute watery diarrhoea). A high concentration of the drug in the commercial preparations as well as the lack of awareness about this among doctors, especially the general practitioners, is the possible contributory factor leading to this situation. A simple measure of bringing down the concentration of nalidixic acid in the available preparations and sticking to oral rehydration solution alone in the treatment of acute watery diarrhoea, can bring down the incidence of this condition.