Proteomic approach to understanding antibiotic action

We have used proteomic technology to elucidate the complex cellular responses of Bacillus subtilis to antimicrobial compounds belonging to classical and emerging antibiotic classes. We established on two-dimensional gels a comprehensive database of cytoplasmic proteins with pIs covering a range of 4 to 7 that were synthesized during treatment with antibiotics or agents known to cause generalized cell damage. Although each antibiotic showed an individual protein expression profile, overlaps in the expression of marker proteins reflected similarities in molecular drug mechanisms, suggesting that novel compounds with unknown mechanisms of action may be classified. Indeed, one such substance, a structurally novel protein synthesis inhibitor (BAY 50-2369), could be classified as a peptidyltransferase inhibitor. These results suggest that this technique gives new insights into the bacterial response toward classical antibiotics and hints at modes of action of novel compounds. Such a method should prove useful in the process of antibiotic drug discovery.

Susceptibility of antimicrobial-resistant urinary Escherichia coli isolates to fluoroquinolones and nitrofurantoin

In vitro surveillance data from across the United States indicate that approximately 10%-20% of urinary Escherichia coli isolates from female outpatients are resistant to trimethoprim-sulfamethoxazole (TMP-SMX). Alternative therapies for uncomplicated urinary tract infections in women include fluoroquinolones and nitrofurantoin, but the activities of these agents against TMP-SMX-resistant isolates are rarely reported. Among TMP-SMX-resistant urinary E. coli isolates tested in US laboratories from 1998 through 2001, 9.5% (5767 of 60,414) were resistant to ciprofloxacin and 1.9% (1214 of 63,817) were resistant to nitrofurantoin; 10.4% of ciprofloxacin-resistant isolates (683 of 6560) were resistant to nitrofurantoin. An association between resistance to fluoroquinolones and nitrofurantoin in E. coli has not been previously reported and warrants further study.

Prooxidant effects of nitrofurantoin

We studied the possibility of using prooxidant effects of nitrofurantoin (furadonin) for stimulation of the natural antioxidant systems for preventing myocardial damage after coronary occlusion. A pronounced cardioprotective effect of the drug was observed.

Trends in antimicrobial resistance among urinary tract infection isolates of Escherichia coli from female outpatients in the United States

The Infectious Diseases Society of America advocates trimethoprim-sulfamethoxazole (SXT) as initial therapy for females with acute uncomplicated bacterial cystitis in settings where the prevalence of SXT resistance does not exceed 10 to 20%. To determine trends in the activities of SXT, ampicillin, ciprofloxacin, and nitrofurantoin among urine isolates of Escherichia coli from female outpatients, susceptibility testing data from The Surveillance Network (TSN) Database-USA (n = 286,187) from 1995 to 2001 were analyzed. Resistance rates among E. coli isolates to ampicillin (range, 36.0 to 37.4% per year), SXT (range, 14.8 to 17.0%), ciprofloxacin (range, 0.7 to 2.5%), and nitrofurantoin (range, 0.4 to 0.8%) varied only slightly over this 7-year period. Ciprofloxacin was the only agent studied that demonstrated a consistent stepwise increase in resistance from 1995 (0.7%) to 2001 (2.5%). In 2001, SXT resistance among E. coli isolates was >10% in all nine U.S. Bureau of the Census regions. At institutions testing > or =100 urinary isolates of E. coli (n = 126) in 2001, ampicillin (range, 27.3 to 98.8%) and SXT (range, 7.5 to 47.1%) resistance rates varied widely while ciprofloxacin (range, 0 to 12.9%) and nitrofurantoin (range, 0 to 2.8%) resistance rates were more consistent. In 2001, the most frequent coresistant phenotypes were resistance to ampicillin and SXT (12.0% of all isolates; 82.3% of coresistant isolates) and resistance to ampicillin, ciprofloxacin, and SXT (1.4% of all isolates; 9.9% of coresistant isolates). Coresistance less frequently included resistance to nitrofurantoin (3.5% of coresistant isolates) than resistance to ciprofloxacin (15.8%), SXT (95.7%), and ampicillin (98.1%). In conclusion, among urinary isolates of E. coli from female outpatients in the United States, national resistance rates to SXT were relatively consistent (14.8 to 17.0%) from 1995 to 2001 but demonstrated considerable regional and institutional variation in 2001. Therapies other than SXT may need to be considered in some locations.

Lysosomal oxidative stress cytotoxicity induced by nitrofurantoin redox cycling in hepatocytes

1. The enzymes responsible for the reductive activation of NFT are not known. We have now shown that under aerobic conditions, inhibitors of cytochrome P450 or P450 reductase but not DT diaphorase prevented NFT induced cytotoxicity and reactive oxygen species ("ROS") formation. This suggests that NFT was reductively activated by reduced cytochrome P450 and/or P450 reductase. 2. The subcellular organelle oxidative stress effects leading to cytotoxicity are not known. Hepatocyte mitochondrial membrane potential was only slightly decreased by NFT before cytotoxicity ensued. However NFT induced lysosomal damage and hepatocyte protease activation. Endocytosis inhibitors, lysosomotropic agents or lysosomal protease inhibitors also prevented NFT induced cytotoxicity. 3. Lipid peroxidation also preceded cytotoxicity. Furthermore desferoxamine (a ferric chelator), antioxidants or ROS scavengers (catalase, mannitol, TEMPOL or dimethylsulfoxide) prevented NFT cytotoxicity. 4. It is concluded that H2O2 reacts with lysosomal Fe(+2) to form "ROS" which causes lysosomal lipid peroxidation, membrane disruption, protease release and cell death.

Antimicrobial susceptibility of Gram-negative uropathogens isolated from obstetric patients

OBJECTIVE

To evaluate the antimicrobial susceptibility of Gram-negative uropathogens isolated from pregnant women.

METHODS

We performed a snapshot cohort study of women receiving care in the University of Florida prenatal clinics during March 2000. Subjects with asymptomatic bacteriuria or cystitis were identified and the antimicrobial susceptibility of each pathogen was recorded. Data were analyzed using chi-square, Fisher's exact test and ninety-five percent confidence intervals, as appropriate.

RESULTS

Ninety-five positive cultures were identified. Isolates were more often susceptible to trimethoprim-sulfamethoxazole (TMP-SMX) (87%) and nitrofurantoin (89%) than to ampicillin (72%) (p < 0.03). Escherichia coli accounted for 71 (75%) cases and was more often susceptible to nitrofurantoin (100%) than to TMP-SMX (87%) (p < 0.01). Proteus isolates were all susceptible to TMP-SMX and resistant to nitrofurantoin (p < 0.01).

CONCLUSIONS

Both TMP-SMX and nitrofurantoin are superior to ampicillin for empiric treatment of lower urinary tract infection in pregnant women. Nitrofurantoin is superior to TMP-SMX for treatment of infections caused by E. coli. For suspected or confirmed cases caused by Proteus organisms, TMP-SMX is the preferred agent.

Cytogenetic analysis of peripheral blood lymphocytes of children treated with nitrofurantoin for recurrent urinary tract infection

The objective of this study was to determine whether nitrofurantoin, used for long-term antimicrobial prophylaxis of urinary tract infection, may induce chromosome aberrations (CAs) and sister chromatid exchanges (SCEs) in lymphocytes of treated children. Ninety-nine blood samples were taken from 69 children aged from 0.2 to 13 years and suffering from urinary tract infection. The treatment consisted of oral administration of nitrofurantoin at doses of 5-8 mg/kg/day for the first 7 days and at doses of 1-2 mg/kg/day for the rest of the treatment period. Blood was sampled before the start of the nitrofurantoin therapy and after 1, 3, 6 and 12 months of the therapy. Analysis of variance showed no statistically significant increase in CA and SCE frequencies in lymphocytes of children treated with nitrofurantoin for 1-12 months. However, a significant increase in SCE rates was determined in lymphocytes of those patients whose blood samples were available both before and after treatment with nitrofurantoin (6.21 +/- 0.28 and 7.30 +/- 0.39 SCE/cell, respectively, P = 0.0315, Student's paired t-test). Moreover, there was a statistically significant correlation (r = 0.6603, P = 0.0270) between cumulative dose of nitrofurantoin and SCE frequency in lymphocytes of children after 1 month of the therapy. Also, in vitro experiments indicated that nitrofurantoin was able to induce both CAs and SCEs in human lymphocytes. Positive findings with chromosome aberrations and SCEs in vitro and suggestive results with SCEs in vivo indicate that further, much larger follow-up studies are needed to elucidate the genetic safety of the therapeutic use of nitrofurantoin.

An update on the role of nitrofurans in the management of urinary tract infections

There have been few recent reviews of the nitrofurans in the literature, and none include recently available data on the use of nitrofurazone (nitrofural) in the prevention of catheter-associated urinary tract infection (CAUTI). Nitrofurazone and nitrofurantoin are the only nitrofurans that have become established in clinical use in the 20th century. These 2 nitrofurans have remained clinically useful against a wide spectrum of gram-positive and gram-negative bacteria, including many strains of common urinary tract pathogens. Today, the primary use of nitrofurantoin is as an oral antibacterial treatment for genitourinary infections. Nitrofurazone is primarily used as a topical antibacterial agent in burns and skin grafts and recently was approved for the prophylaxis of CAUTI. The recent development of a nitrofurazone-impregnated catheter as a novel modality in the prevention of CAUTI reflects a renewed interest in the effectiveness of nitrofurans. In an era when concern about bacterial resistance to many anti-infective agents is growing, the nitrofurans have continued to be active against organisms that have developed resistance to antibacterials. The presence of multiple mechanisms of action for the nitrofurans might be expected to reduce the ability of bacteria to develop resistance. Considering that an emergence of resistance to the nitrofurans has not appreciably occurred after several decades of clinical use, the nitrofurans may be unique among common antibacterial agents in this regard.

[The Dutch College of General Practitioners' guideline on urinary tract infections: response from the viewpoint of internal medicine]

In 1999 the Dutch College of General Practitioners (NHG) and the Dutch Institute for Healthcare Improvement (CBO) published revisions of their guidelines on urinary tract infections. Contrary to previous editions, the revised guidelines agree on most points, but not all. To diagnose a urinary tract infection in non-pregnant women with dysuria, the NHG guideline advises a nitrite test and a dip-slide culture if the nitrite test is negative. Although the dip-slide improves the diagnostic accuracy, a considerable number of patients have to wait at least 24 hours before therapy is given. The diagnostic approach of the CBO guideline uses only rapidly available test results, with the consequence that some women are treated despite not having an infection. The NHG guideline advocates the use of amoxicillin or nitrofurantoin for pregnant women. Amoxicillin is a questionable choice given that about 30% of isolates are resistant to it. Nitrofurantoin is in theory a correct choice. However, it is not registered for the treatment of complicated urinary tract infections. In the CBO guideline amoxicillin-clavulanic acid is considered to be sufficiently safe for the treatment of pregnant women because most urinary tract infections occur after the first trimester.

The establishment of conditions to efficiently screen photosynthesis-deficient mutants of Synechocystis sp. PCC 6803 by nitrofurantoin treatment

A method based on the susceptibility of photosynthetic organisms to nitrofurantoin under illumination was established to screen mutants of Synechocystis sp. PCC 6803 deficient in the function of photosystem II, which were created by random PCR mutagenesis targeted to the psbAII gene coding for the D1 protein of the photosystem II reaction center. In this method, cyanobacterial colonies on a nitrocellulose membrane on a BG11 agar plate were treated with nitrofurantoin at 1.0 mM under white light at 40 microE x m(-2 ) x s(-1) for 2 h, and then kept under normal conditions without nitrofurantoin so that surviving cells could grow. This method was also shown to be useful for screening mutants deficient in the function of photosystem I.

Nitrofurantoin quadruple therapy for Helicobacter pylori infection: effect of metronidazole resistance

BACKGROUND

Antibiotic resistance has increasingly been recognized as the major cause of treatment failure for Helicobacter pylori infection. New therapies for patients with metronidazole- or clarithromycin-resistant H. pylori are needed.

AIM

To investigate the role of nitrofurantoin quadruple therapy for the treatment of H. pylori.

METHODS

Patients with confirmed H. pylori infection received nitrofurantoin (100 mg t.d.s.), omeprazole (20 mg b.d.), Pepto-Bismol (two tablets t.d.s.), and tetracycline (500 mg t.d.s.) for 14 days. Four or more weeks after the end of therapy, outcome was assessed by repeat endoscopy with histology and culture or urea breath testing.

RESULTS

Thirty patients were entered, including 25 men and five women; the mean age was 54.9 years. The most common diagnoses were duodenal ulcer (23%) and GERD (18%). The intention-to-treat cure rate was 70% (95% CI: 50.6-85%). Nitrofurantoin quadruple therapy was more effective with metronidazole-sensitive strains (88%; 15 out of 17) than with metronidazole-resistant strains (33%; three out of nine; P=0.008). Two of the treatment failures had pre-treatment isolates susceptible to metronidazole, which were resistant after therapy.

CONCLUSIONS

Because nitrofurantoin quadruple therapy performed inadequately in the presence of metronidazole resistance, we conclude that nitrofurantoin is unlikely to find clinical utility for the eradication of H. pylori.

Furazolidone- and nitrofurantoin-resistant Helicobacter pylori: prevalence and role of genes involved in metronidazole resistance

The prevalence of furazolidone, nitrofurantoin, and metronidazole resistance among Helicobacter pylori strains was assessed with 431 clinical isolates. Fifty-two percent were metronidazole resistant, compared to 2% (7 of 431) with resistance to furazolidone and nitrofurantoin. All seven furazolidone- and nitrofurantoin-resistant isolates were also metronidazole resistant. rdxA, frxA, and fdxB knockouts did not result in furazolidone or nitrofurantoin resistance. These data suggest that furazolidone and nitrofurantoin may be good alternatives to metronidazole for treating H. pylori infection.

Nitrofurantoin is active against vancomycin-resistant enterococci

The activity of nitrofurantoin was tested against 300 isolates of Enterococcus faecium, Enterococcus faecalis, and Enterococcus gallinarum. No isolates tested were resistant to nitrofurantoin (MIC, >/=128 microg/ml), including vancomycin-resistant E. faecium isolates with vanA- and vanB-positive genotypes and vancomycin-resistant E. gallinarum isolates. We conclude that nitrofurantoin may provide effective treatment of urinary tract infections caused by vancomycin-resistant enterococci.

Bactericidal activity of nitrofurans against growing and dormant Mycobacterium bovis BCG

Depletion of oxygen triggers the shift-down of Mycobacterium bovis BCG to a state of dormancy. Bacilli in their dormant state are resistant to standard anti-mycobacterials. The nitroimidazole metronidazole was the first compound identified to show bactericidal activity against dormant tubercle bacilli. In contrast to metronidazole's selective toxicity for dormant bacilli, we report here that the nitrofurans nitrofurantoin, furaltadone and nitrofurazone showed bactericidal activity against dormant and growing bacteria. Importantly, the bactericidal effect of nitrofurans on dormant bacilli was 35- to 250-fold higher compared with metronidazole.

Increasing resistance to fluoroquinolones in escherichia coli from urinary tract infections in the netherlands

In continuous surveillance of routine samples from five Dutch laboratories, we studied resistance to the antibiotics most commonly prescribed for urinary tract infections (UTI) in The Netherlands, namely norfloxacin, amoxycillin, trimethoprim and nitrofurantoin, from 1989 to 1998 in >90000 Escherichia coli isolates. Resistance to norfloxacin increased from 1.3% in 1989 to 5.8% in 1998. Multiresistance, defined as resistance to norfloxacin and at least two of the other three antibiotics, increased from 0.5% in 1989 to 4. 0% in 1998. Multivariate analysis of the norfloxacin resistance demonstrated that this yearly increase (the odds ratio was 1.0 in 1989, 1.6 in 1992, 2.9 in 1995 and 6.1 in 1998) was independent of other determinants of resistance to norfloxacin, such as age, gender and origin of the isolate. Analysis of strata, classified by year, age and gender, demonstrated an association between prescription of fluoroquinolones (defined daily doses per case of UTI) and resistance to norfloxacin in E. coli (P < 0.001). There was no significant association with the prescription of nitrofuran derivatives (nitrofurantoin) and trimethoprim with or without sulphamethoxazole. The yearly increase of resistance to fluoroquinolones in E. coli from UTI may stem from increased prescription of fluoroquinolones for UTI. Resistance of E. coli to these agents is likely to increase further as fluoroquinolone use increases in future.

[Nitrofurans: a modern treatment for uncomplicated urinary infections?]

From January 1995 to December 1998, 2,912 strains of enteric bacilli were isolated from the urinary tract. Increasing antibiotic resistance in Enterobacteriaceae as a cause of urinary tract infection (UTI) led us to reevaluate first- and second-line therapies. We studied antimicrobial susceptibilities of these strains to norfloxacin (NOR), nalidixic acid (NAL), trimethoprim sulfamethoxazole (TS) and nitrofurantoin (FT) using the disk diffusion method. These results show no significant superiority of the activity of nitrofurantoin against Enterobacteriaceae compared with the other antibiotics with sustained concentration in urine. However, if we consider only multiresistant Enterobacteriaceae (cefotaxime resistant), this molecule appears to be very active. These results show a significant superiority of nitrofurantoin in vitro against these multiresistant Enterobacteriaceae. Thus, this molecule could once again become a good choice for the treatment of uncomplicated UTI.

A novel NADPH:diamide oxidoreductase activity in arabidopsis thaliana P1 zeta-crystallin

The zeta-crystallin (ZCr) gene P1 of Arabidopsis thaliana, known to confer tolerance toward the oxidizing drug 1,1'-azobis(N, N-dimethylformamide) (diamide) to yeast [Babiychuk, E., Kushnir, S., Belles-Boix, E., Van Montagu, M. & Inzé, D. (1995) J. Biol. Chem. 270, 26224], was expressed in Escherichia coli to characterize biochemical properties of the P1-zeta-crystallin (P1-ZCr). Recombinant P1-ZCr, a noncovalent dimer, showed NADPH:quinone oxidoreductase activity with specificity to quinones similar to that of guinea-pig ZCr. P1-ZCr also catalyzed the divalent reduction of diamide to 1,2-bis(N,N-dimethylcarbamoyl)hydrazine, with a kcat comparable with that for quinones. Two other azodicarbonyl compounds also served as substrates of P1-ZCr. Guinea-pig ZCr, however, did not catalyze the azodicarbonyl reduction. Hence, plant ZCr is distinct from mammalian ZCr, and can be referred to as NADPH:azodicarbonyl/quinone reductase. The quinone-reducing reaction was accompanied by radical chain reactions to produce superoxide radicals, while the azodicarbonyl-reducing reaction was not. Specificity to NADPH, as judged by kcat/Km, was > 1000-fold higher than that to NADH both for quinones and diamide. N-Ethylmaleimide and p-chloromercuribenzoic acid inhibited both quinone-reducing and diamide-reducing activities. Both NADPH and NADP+ suppressed the inhibition, but NADH did not, suggesting that sulfhydryl groups reside in the binding site for the phosphate group on the adenosine moiety of NADPH. The diamide-reducing activity of P1-ZCr accounts for the tolerance of P1-overexpressing yeast to diamide. Other possible physiological functions of P1-ZCr in plants are discussed.

Statistical modeling and analyses of a base-specific Salmonella mutagenicity assay

Statistical features of a base-specific Salmonella mutagenicity assay are considered in detail, following up on a previous report comparing responses of base-specific Salmonella (Ames II) strains with those of traditional tester strains. In addition to using different Salmonella strains, the new procedure also differs in that it is performed as a microwell fluctuation test, as opposed to the standard plate or preincubation test. This report describes the statistical modeling of data obtained from the use of these new strains in the microwell test procedure. We emphasize how to assess any significant interactions between replicate cultures and exposure doses, and how to identify a significant increase in the mutagenic response to a series of concentrations of a test substance.

A Canadian national surveillance study of urinary tract isolates from outpatients: comparison of the activities of trimethoprim-sulfamethoxazole, ampicillin, mecillinam, nitrofurantoin, and ciprofloxacin. The Canadian Urinary Isolate Study Group

Ampicillin, trimethoprim-sulfamethoxazole, mecillinam, nitrofurantoin, and ciprofloxacin mean resistance rates for 2,000 urinary tract isolates collected from outpatients across Canada in 1998 were 41.1, 19.2, 14.7, 5.0, and 1.8%, respectively. For Escherichia coli isolates alone (n = 1,681) comparable rates were 41. 0, 18.9, 7.4, 0.1, and 1.2%, respectively. The majority of E. coli isolates resistant to ampicillin, trimethoprim-sulfamethoxazole, or ciprofloxacin were susceptible (MIC, <16 microg/ml) to mecillinam.

Antimicrobial resistance patterns in urinary isolates from nursing home residents. Fifteen years of data reviewed

The antibiotic resistance patterns of gram-negative bacteria isolated from nursing home patients between 1983 and 1997 were analysed. Escherichia coli was the most prevalent isolate (48%) followed by Proteus spp. (26%) and other Enterobacteriaceae (20%). During the study period, the susceptibility of E. coli decreased for co-trimoxazole (79% to 62%), increased for nitrofurantoin (79% to 91%) and remained unchanged for amoxycillin (41%). Susceptibility to norfloxacin, available from 1990, decreased from 87% to 71%. Similar trends were observed when the susceptibilities of all gram-negative urinary pathogens were combined. The changes in susceptibility can probably be attributed to the empirical prescribing practices in the nursing homes studied.

Mechanisms of resistance to ampicillin, chloramphenicol and quinolones in multiresistant Salmonella typhimurium strains isolated from fish

Mechanisms of antibiotic resistance and epidemiological relationships were investigated for five multiresistant strains of Salmonella typhimurium isolated from fish in India. Four strains showed resistance to nalidixic acid, chloramphenicol, tetracycline, co-trimoxazole, gentamicin and beta-lactam antibiotics. The remaining strain was susceptible to all beta-lactam antibiotics tested and to co-trimoxazole but resistant to the other antibiotics tested. Epidemiological analysis performed by REP-PCR showed that the five isolates belonged to the same clone. Resistance to nalidixic acid was related to a single mutation in the gyrA gene. Chloramphenicol resistance was related to the production of chloramphenicol acetyl-transferase. An OXA-1 beta-lactamase, located in an integron, was responsible for resistance to ampicillin. These results indicate the health hazard posed by the fact that S. typhimurium may acquire or develop several mechanisms of resistance to a variety of antibiotics, including quinolones, and can thus cause disease in humans which may be difficult to treat.

In-vitro evaluation of nitrofurantoin as an alternative agent for metronidazole in combination antimicrobial therapy against Helicobacter pylori

Increasing metronidazole resistance suggests the need for alternative antibiotics for combination therapy of Helicobacter pylori infections. We evaluated a metronidazole-resistant and a clarithromycin-resistant strain of H. pylori under stationary growth phase conditions that favoured physiological conditions in order to determine if nitrofurantoin might be a suitable alternative for metronidazole in combination therapy. The results demonstrated that the triple combination of bismuth, tetracycline and nitrofurantoin achieved greater bactericidal activity against these two strains than did the combination of bismuth, tetracycline and metronidazole. These results suggest that further evaluation is warranted.

Mecillinam activity compared to ampicillin, trimethoprim/sulfamethoxazole, ciprofloxacin and nitrofurantoin against urinary tract isolates of gram-negative bacilli

Recent Canadian, American and European studies have reported increased ampicillin and trimethoprim/sulfamethoxazole resistance among urinary tract isolates of Escherichia coli. This trend suggests that a reevaluation of first- and second-line therapies for the treatment of community-acquired urinary tract infections is necessary. Mecillinam, a beta-lactam with preferential activity against gram-negative penicillin binding protein 2 (unlike other beta-lactams which preferentially bind gram-negative penicillin binding proteins 1a, 1b or 3), may offer clinically significant activity against ampicillin-resistant and trimethoprim/sulfamethoxazole-resistant E. coli. To test this assertion, the activity of mecillinam was compared with ampicillin, trimethoprim/sulfamethoxazole, nitrofurantoin and ciprofloxacin against 258 consecutive gram-negative urinary tract isolates collected at a Canadian tertiary care hospital. Mecillinam demonstrated significantly better activity than ampicillin and trimethoprim/sulfamethoxazole and significantly less activity than ciprofloxacin and nitrofurantoin against the 258 isolates tested. Against E. coli isolates specifically, mecillinam was significantly more active than ampicillin and trimethoprim/sulfamethoxazole (p < 0. 001) and as active as ciprofloxacin and nitrofurantoin. Mecillinam was active against 91.9% of ampicillin-resistant E. coli and 95.9% of trimethoprim/sulfamethoxazole-resistant E. coli. We conclude that mecillinam should be reevaluated for potential use in the treatment of community-acquired urinary tract infections.