Illegal use of nitrofurans in food animals: Contribution to human salmonellosis?

Recent observations in Portugal of a remarkable incidence (65%) of Salmonella isolates from several sources (predominantly human and poultry) with decreased susceptibility to nitrofurantoin (MIC > or =64 mg/L), mostly comprising serogroup D isolates of Salmonella Enteritidis belonging to different phage types, suggest that illegal use of nitrofurans, especially in the poultry industry, might have contributed to the selection and prevalence of S. Enteritidis in food animals, and consequently to human salmonellosis in Portugal. Indiscriminate use of nitrofurans might also be implicated in the emergence of two multiresistant Salmonella Typhimurium clones disseminated throughout the country.

A TLC bioautographic assay for the detection of nitrofurantoin resistance reversal compound

A simple TLC bioautographic method was developed for detection of antibiotic resistance reversal agents. In this study, the retention factor values of the components of some essential oils not previously shown to have any antibacterial activity were evaluated on nitrofurantoin supplemented agar media. The active component of Artemisia annua, Artemisia dracunculus and Eucalyptus globulus essential oils was piperitone which increased the antibacterial activity of nitrofurantoin against Enterobacter cloacae. Piperitone was not detected in the essential oil of Humulus lupulus and we could not observe any clear areas in this bioautographic method.

Resistance in clinical isolates of Enterococcusfaecalis encountered at the University Hospital of the West Indies, Jamaica

Enterococcus faecalis isolates were examined by an automated identification and susceptibility system. Almost all of the 97 isolates were ampicillin susceptible (n = 86) and tetracycline resistant (n = 89). All were nitrofurantoin susceptible. About a third of isolates showed high level resistance to the aminoglycosides streptomicin and gentamicin and this was usually associated with ciprofloxacin resistance (n = 34). Seven isolates were vancomycin resistant, including one that was ampicillin resistant. Most forms of resistance described elsewhere were found

Antibiotic resistance of urinary tract pathogens and evaluation of empirical treatment in Turkish children with urinary tract infections

The changing pattern of antimicrobial resistance in the causative microorganisms of urinary tract infection (UTI) in childhood is a growing problem. The aims of this study were to assess the resistance patterns of urinary isolates to commonly used antimicrobials and to evaluate the options for empirical treatment of UTI. A prospective cross-sectional analysis of bacteria isolated from children with UTI was performed between January 2003 and January 2004. Resistance to antibiotics was analysed in three age groups: Group I, < or =12 months; Group II, 13-60 months; and Group III, >60 months. A total of 165 urinary pathogens were isolated from 131 patients. Mean patient age was 63.7+/-49.8 months. The most common causative agent was Escherichia coli (87% of cases) followed by Klebsiella pneumoniae (10%). Resistance to ampicillin (74.2%) and co-trimoxazole (61.3%) was significant in all isolates. Nitrofurantoin was the most active agent against E. coli (2.2% resistant isolates), followed by amikacin (4.9%), ceftriaxone (7.5%) and ciprofloxacin (12%). None of the isolates from Group I patients were resistant to ciprofloxacin and a low resistance rate (7.1%) was noted for amikacin. In Group II patients, none of the isolates were resistant to amikacin, and ceftriaxone was the second most suitable antibiotic (resistance rate 2.2%). In Group III patients, the lowest resistance rate was against nitrofurantoin (2.7%). In conclusion, we observed that the use of ampicillin and co-trimoxazole as a single agent for empirical treatment of a suspected UTI would not cover the majority of urinary pathogens in our region. Whilst amikacin, with a negligible resistance rate, was suitable in all age groups, gentamicin might still be useful as an empirical treatment of UTI in children aged >1 year. Nitrofurantoin could be included as a reasonable alternative in the empirical treatment of lower UTI in older children.

Identification of a respiratory-type nitrate reductase and its role for survival of Mycobacterium smegmatis in Wayne model

Nitrate reductase (NR) is found to be expressed in certain mycobacterium sp. whose link with the development of persistence is yet to be resolved. The present study demonstrates the action of selective inhibitors on NR as well as in the survival of Mycobacterium smegmatis using Wayne's model. During gradual shift down to anaerobic stage in Wayne's model, conversion of nitrate to nitrite became apparent in M. smegmatis. More than 97 percent inhibition was observed for the conversion of nitrate to nitrite by azide (0.05 mM) and thiocyanate (20 mM) in both whole-cell as well as its cell-free lysate, respectively. Under identical condition, chlorate (20 mM) inhibited nitrate reduction by 67 and 10 percent, respectively. At these concentrations, neither of azide, thiocyanate nor chlorate had any significant effect on cell growth under aerobic condition. In Wayne's culture model, thiocyanate and chlorate inhibited the growth of M. smegmatis by almost 2 logs at the same concentrations whereas azide inhibited by almost 1.75 log when added at the time of inoculation. Exposure of same culture at 96 h after inoculation in Wayne's model to these inhibitors showed 1.74, 1.95 and 2.37 log inhibition of viable cells with respect to azide, thiocyanate and chlorate. These findings further indicated that NR inhibitors kill the bacilli at anaerobic stage under the experimental condition mentioned. Metronidazole (MTZ) (2 mM) and Nitrofurantoin (NIT) (0.3 mM) reduced the cell number at both stages by <0.7 log. They did not have any effect on NR. Altogether, the results clearly indicate that NR-specific inhibitors could become more promising in killing the bacilli at anaerobic stage than the available conventional drugs.

Pharmacokinetic and pharmacodynamic aspects of antimicrobial agents for the treatment of uncomplicated urinary tract infections

Uncomplicated urinary tract infections (UTI) are treated with beta-lactams, co-trimoxazole, quinolones and fosfomycin tromethamine. Due to increasing resistance of causative pathogens, antibiotics should be used by considering their pharmacodynamic and pharmacokinetic characteristics. beta-lactams have time-dependent activity and should not be used once-daily. Co-trimoxazole should be restricted due to increasing chemoresistance. Fluoroquinolones play a primary role in the treatment of serious and complicated infections. Fosfomycin tromethamine is active against most urinary tract pathogens. In vitro time-kill kinetics of fosfomycin against Escherichia coli and Proteus mirabilis showed primarily concentration-dependent activity, with a prolonged post-antibiotic effect (3.4 to 4.7h). Based on these results a single 3g dose of fosfomycin guarantees optimal efficacy against common uropathogens with an AUC(urine)/MIC ratio of 500.

Salmonellae isolated from captive animals in Ibadan, Western State of Nigeria

Six serotypes of salmonellae, Salmonella offa, S. glostrup, S. wimborne, S. dublin, S. saint-paul and S. webridge were isolated from captive wild animals in Ibadan, Western State of Nigeria. S. wimborne and S. glostrup are reported for the first time in Nigeria. All strains were sensitive to nitrofurantoin (200 mcg) and chloramphenical (10 mcg) but there wasmarked resistance to sulphafurazole (100 mcg) and penicillin (1.5 units).

Uncomplicated urinary tract infection in women. Current practice and the effect of antibiotic resistance on empiric treatment

OBJECTIVE

To review treatment recommendations for empiric therapy of uncomplicated urinary tract infection (uUTI) in light of evolving antibiotic resistance and to consider use of guidelines to promote optimal practice.

QUALITY OF EVIDENCE

PubMed was searched and additional relevant references were identified by reviewing articles found in the search. Guidelines were identified through discussion with family practitioners. Level of evidence was assessed for recommendations.

MAIN MESSAGE

Many women have uUTIs. The treatment approach is usually empiric antimicrobial therapy without obtaining pretherapy cultures. Trimethoprim-sulfamethoxazole is standard first-line empiric treatment. While resistance to this drug is increasing, it remains only about 10% in community-acquired Escherichia coli in Canada. Concerns about increased resistance have contributed to greater use of fluoroquinolones, but widespread empiric use of this class of medications might promote resistance to fluoroquinolones. Hence, fluoroquinolones should not be considered first-line therapy. While guidelines for treatment of uUTIs have been developed, their usefulness is compromised by their conflicting recommendations.

CONCLUSION

Trimethoprim-sulfamethoxazole and nitrofurantoin remain first-choice empiric therapy for uUTIs. Development of guidelines relevant to family physicians and community education programs that incorporate local susceptibility patterns are important strategies for promoting optimal practice.

[In vitro activity of furazolidone and nitrofurantoin in Helicobacter pylori clinical isolates and study of mutation rate]

Clarithromycin, amoxicillin, tetracycline and metronidazole are the most frequently used antimicrobials for Helicobacter pylori infection treatment. While tetracycline and amoxicillin resistance are rare, clarithromycin and metronidazole resistance vary in different populations and are considered factors for treatment failure. The aim of this study was to determine the in vitro activity of furazolidone and nitrofurantoin in 164 H. pylori clinical isolates by agar dilution and to determine the spontaneous mutation rate. Metronidazole and clarithromycin resistance were 23.77% (CI95%: 18.96-29.14) and 16.78% (CI95%: 12.64-21.62), respectively; moreover, 1.4% (CI95%: 0.38-3.54) were intermediate to clarithromycin. All the isolates were susceptible to amoxicillin and tetracycline. Furazolidone and nitrofurantoin resistance rates were 1.82% (CI95%: 0.37-5.25) and 0.6% (CI95%: 0-3.35), respectively. The three furazolidone-resistant strains were nitrofurantoine-susceptible (MIC 4 mg/l for furazolidone and 2 mg/l for nitrofurantoin) and the nitrofurantoin-resistant strains were furazolidone-susceptible (MIC 4 mg/l for nitrofurantoin and 1 mg/l for furazolidone). These four strains were metronidazole-resistant (MIC 16 mg/l). Furazolidone or nitrofurantoin spontaneous mutants were not detected in the eight H. pylori strains tested. However, mutants with resistance to metronidazole were found with all the strains with a mutation rate of 7.4 x 10(-10) to 9.4 x 10(-10). Furazolidone and nitrofurantoin showed an excellent in vitro activity against the H. pylori clinical isolates included herein, supporting the usefulness of furazolidone as second-line antimicrobial after treatment failure or as first-line therapy in populations with low economical resources.

Antibiogram pattern of isolates from UTI cases in Eastern part of Nepal

The present study was conducted to study antibiogram pattern of isolates from urinary tract infection (UTI) cases at a referral hospital in Eastern Nepal. Of the total 2,799 of urine samples studied, 720 (25.7%) were positive for some kinds of bacterial agents. Escherichia coli was most predominant organism (59.0%) followed by Klebsiella sp. (12.6%), Pseudomonas aeruginosa (6.9%), Acinetobacter sp. (5.9%), Enterococcus sp. (4.2%) and others (2.6%). Antimicrobial susceptibility testing was done by Kirby-Bauer's disc diffusion method following National Committee for Clinical Laboratory Services (NCCLS) guidelines. Most strains of Esch. coli and Klebsiella sp. were resistant to Ampicillin and Ciprofloxacin. Ps. aeruginosa and Acinetobacter sp. showed relatively higher resistance to Aminoglycosides. These organisms were often multidrug resistant. Ps. aeruginosa showed 68.0% resistance to even Ceftazidime. For Enterococcus sp. Nitrofurantion and Gentamicin were the drugs of choice. Of the all antimicrobial agents tested, Ciprofloxacin showed most disappointing result.

Biochemical characterization of trinitrotoluene transforming oxygen-insensitive nitroreductases from Clostridium acetobutylicum ATCC 824

The genes that encode oxygen-insensitive nitroreductases from Clostridium acetobutylicum possessing 2,4,6-Trinitrotoluene (TNT) transformation activity were cloned, sequenced and characterized. The gene products NitA (MW 31 kDa) and NitB (MW 23 kDa) were purified to homogeneity. The NitA and NitB are oxygen-insensitive nitroreductases comprised of a single nitroreductase domain. NitA and NitB enzymes show spectral characteristics similar to flavoproteins. The biochemical characteristics of NitA and NitB are highly similar to those of NfsA, the major nitroreductase from E. coli. NitA exhibited broad specificity similar to that of E. coli NfsA and displayed no flavin reductase activity. NitB showed broad substrate specificity toward nitrocompounds in a pattern similar to NfsA and NfsB of Escherichia coli. NitB has high sequence similarity to NAD(P)H nitroreductase from Archaeoglobus fulgidus. NitA could utilize only NADH as an electron donor, whereas NitB utilized both NADH and NADPH as electron donors with a preference for NADH. The activity of both nitroreductases was high toward 2,4-Dinitrotoluene (2,4-DNT) as a substrate. Both the nitroreductases were inhibited by dicoumarol and salicyl hydroxamate. The nitroreductases showed higher relative expression on induction with TNT, nitrofurazone and nitrofurantoin compared to the uninduced control.

Differential response of iron metabolism to oxidative stress generated by antimycin A and nitrofurantoin

The close interrelationship of oxidative stress and iron is evident by the influence of intracellular reactive oxygen species on iron metabolism. Oxygen radicals can lead to release of iron from iron-sulfur proteins and ferritin, and can damage iron-containing enzymes such as mitochondrial aconitase. Treatment of HepG2 human hepatoma cells with antimycin A has two effects relating to iron depending on the concentrations of antimycin A: increase of the labile iron pool and stimulation of non-transferrin-bound iron uptake. Whereas the first could also be generated with nitrofurantoin, the stimulation of non-transferrin-bound iron uptake was only seen with antimycin A and needed considerably higher concentrations. Pretreatment of the cells with ebselen, which scavenges peroxides, reverted only the effect of nitrofurantoin on the labile iron pool. Depletion with iron chelators before or after treatment with antimycin A diminished the stimulation of non-transferrin-bound iron uptake. We conclude that the generation of oxygen radicals in the mitochondria leads to the liberation of iron from mitochondrial enzymes, which enters the labile iron pool. But high concentrations of antimycin A leading to the stimulation of non-transferrin-bound iron uptake is possibly not related to the inhibition of the respiratory chain.

Some virulence characteristics of uropathogenic Escherichia coli in different patient groups

BACKGROUND & OBJECTIVE

Uropathogenic Escherichia coli have virulence properties, that are absent in non pathogenic E. coli. The distribution of these markers can vary according to patient populations. Hence, a study was undertaken to describe the presence of virulence factors like Pfimbriae, type 1 fimbriae and haemolysin in E.coli causing urinary infections in three groups of patients. Antibiogram was also recorded to determine differences, if any, between the groups.

METHODS

E. coli isolated from three groups of subjects, in counts of >10(5) CFU/ml and in pure growth were tested for mannose resistant haemagglutination (MRHA) to indicate P fimbriae and mannose sensitive haemagglutination (MSHA) to indicate type 1 fimbriae. Haemolysin production and antimicrobial susceptibility patterns were also recorded.

RESULTS

Significantly more isolates from antenatal and postnatal women possessed P fimbriae compared to groups with urologic abnormalities (P=0.05). Haemolysin production was also significantly higher (P<0.001) in this group. Greater proportions of isolates from pregnant women were susceptible to commonly used antimicrobials. However, resistance to third generation cephalosporins was present even in these isolates from community infections.

INTERPRETATION & CONCLUSION

In patients with urological abnormality, E. coli with lower virulence can cause infections. Isolates from these patients exhibited greater drug resistance. In pregnant women and in community acquired infections, simple antimicrobial drugs like nitrofurantoin might still be useful. However, urgent and stringent policies for antimicrobial use and infection control in hospitals are required in India.

Bacillus subtilis paraquat resistance is directed by sigmaM, an extracytoplasmic function sigma factor, and is conferred by YqjL and BcrC

A Bacillus subtilis sigM null mutant, lacking the extracytoplasmic function sigma(M) protein, was sensitive to paraquat (PQ), a superoxide-generating reagent, but not to the redox stress-inducing compounds hydrogen peroxide, cumene hydroperoxide, t-butyl hydroperoxide, or diamide. Surprisingly, a sigM mutant was only sensitive to superoxide-generating compounds with a dipyridyl ring such as PQ, ethyl viologen, benzyl viologen, and diquat but not to menadione, plumbagin, pyrogallol, or nitrofurantoin. Mutational analysis of candidate sigma(M)-regulated genes revealed that both YqjL, a putative hydrolase, and BcrC, a bacitracin resistance protein, were involved in PQ resistance. Expression of yqjL, but not bcrC, from a xylose-inducible promoter restored PQ resistance to the sigM mutant.

Sex-dependent expression and activity of the ATP-binding cassette transporter breast cancer resistance protein (BCRP/ABCG2) in liver

The breast cancer resistance protein (BCRP/ABCG2) is an ATP-binding cassette drug efflux transporter present in the liver and other tissues that affects the pharmacological behavior of many compounds. To assess the possible role of BCRP in sex-dependent pharmacokinetics, we studied the in vivo disposition of several murine Bcrp1 substrates in male and female wild-type and Bcrp1 knockout mice. After oral administration of the antibiotic nitrofurantoin, the area under the plasma concentration-time curve in wild-type female mice was approximately 2-fold higher than in wild-type male mice. Moreover, after i.v. administration of nitrofurantoin, the antiulcerative cimetidine, the anticancer drug topotecan, and the carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), the plasma levels in wild-type female mice were all significantly higher than those in wild-type male mice. Analysis of the expression of murine Bcrp1 in several pharmacokinetically important tissues showed that only the hepatic Bcrp1 expression was higher in male mice compared with female mice. In line with this difference, the hepatobiliary excretion for nitrofurantoin and PhIP was, respectively, 9-fold higher and approximately 2-fold higher in male compared with female wild-type mice. No significant sex differences were observed in plasma levels or hepatobiliary excretion for any of the tested compounds in Bcrp1-/- mice, indicating that Bcrp1 was the main cause of the sex difference in wild-type mice. Analysis of hepatic expression of human BCRP also indicated a higher expression in men compared with women. In conclusion, sex-dependent expression of BCRP/Bcrp1 in the liver may be a cause of sex-specific variability in the pharmacokinetics of BCRP substrates, with potential impact on the clinical-therapeutic applications and toxicity risks of drugs.

In-vitro activity of nitrofurantoin in enterococcus urinary tract infection

OBJECTIVE

To compare in-vitro antimicrobial susceptibility of nitrofurantoin against commonly used antimicrobials for the treatment of urinary tract infection caused by enterococci.

METHODS

A total of 144 enterococci (Enterococcus faecalis, n=130, Enterococcus faecium, n=14) isolated and confirmed by biochemical tests at the department of Microbiology, Armed Forces Institute of Pathology, Rawalpindi, for a period of three years were included in the study. The antimicrobial susceptibility tests of isolated organisms were performed by standard disc diffusion method as recommended by NCCLS. In addition to nitrofurantoin (NIT), doxycycline (DOX), co-trimoxazole (COT), ampicillin (AMP), imipenem (IPM) and vancomycin (VAN) were used for antimicrobial susceptibility testing.

RESULTS

One hundred and twenty seven (88%) isolates of Enterococci were susceptible to NIT while 72% (n = 103) to AMP, 13% to COT, 11% to DOX, 91% to IPM and 99% to VAN. Among the strains resistant to AMP, COT, DOX, IPM and VAN, 50-88% were susceptible to NIT.

CONCLUSION

Nitrofurantoin is an effective antimicrobial in vitro and can be used for treatment of Enterococcus urinary tract infections.

In vitro activity of nitrofuran derivatives on growth and morphology of Salmonella enterica serotype Enteritidis

AIMS

To evaluate the effect of nitrofuran derivatives furazolidone (Fz) and nitrofurantoin (Nf) on Salmonella enterica serovar Enteritidis PT4 in vitro, with regard to cell growth, morphology and ultrastructure.

METHODS AND RESULTS

The effects of Fz on the growth rates of Fz resistant (FzR) and sensitive (FzS) strains were assessed by viable counts. Over 24 h incubation, concentrations of <1 microg ml(-1) of Fz were bacteriostatic to the FzS strain. The FzR strain tolerated concentrations up to 16 microg ml(-1) before cell numbers diminished over the same time period. The effect on the growth rate of the FzS strain after 1 h exposure to supra-inhibitory concentrations of Fz, gave a maximum response at 32X minimum inhibitory concentration (MIC) of 4.5 h. Effects on the ultrastructure of bacterial cells by scanning electron and transmission microscopy, and DNA-specific staining with DAPI of the FzS strain exposed to nitrofurans were studied. Abnormalities such as extensive filamentation with sparse, sporadic nucleotide distribution and evidence of extrusions in the cell envelope in the form of blebs were evident.

CONCLUSIONS

Nitrofurans exert their bactericidal effect on Salmonella by inducing extensive structural alteration after exposure at sub- or suprainhibitory concentrations, involving inhibition of cell division because of the activated drug causing an intercalating type of binding in DNA.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results demonstrate the in vitro activity of the nitrofuran derivatives, furazolidone and nitrofurantoin on Salmonella, defining the pharmacodynamics and physical nature of their action as therapeutic agents.

Urinary tract infections in South Croatia: aetiology and antimicrobial resistance

The aim of this study was to determine the distribution of uropathogens isolated from outpatients living in South Croatia and the in vitro susceptibility of these organisms to antimicrobial agents. Of 5080 enrolled uropathogen isolates, 82.28% isolates were Gram-negative, the most frequent isolates being Escherichia coli (62.62%), enterococci (10.18%), Proteus mirabilis (5.31%), Streptococcus agalactiae (3.84%), Staphylococcus spp. (3.70%), Pseudomonas spp. (3.46%), Klebsiella spp. (2.38%). The E. coli resistance rate was 42.17% to amoxycillin, 20.59% to trimethoprim-sulphamethoxazole and 6.09% to norfloxacin. Almost all Klebsiella spp. isolates were resistant to amoxycillin and the resistance rate to trimethoprim-sulphamethoxazole was over 20%, and 14.15% to the fluoroquinolones. A high methicillin-resistance rate was found among S. aureus (61.22%) and coagulase negative staphylococci (41.48).

Antitumor activity of common antibiotics against superficial bladder cancer

OBJECTIVES

The recurrence rate for superficial bladder tumors treated with complete resection averages 88%. Intravesical chemotherapy decreases the recurrence rate by only 14%; thus, new chemotherapeutic agents are needed. Antibiotics are often used to prevent infections after transurethral resection of bladder tumors. Oral intake of antibiotics results in significantly greater concentrations in the urine than in the serum. Our objective was to evaluate four commonly used urinary antibiotics for their cytotoxic activity against bladder cancer cells at clinically relevant concentrations.

METHODS

Three human transitional cell carcinoma lines--HTB9 (grade 2), T24 (grade 3), and TccSup (grade 4)--were exposed to ciprofloxacin, trimethoprim-sulfamethoxazole, cefazolin, or nitrofurantoin at concentrations from 0 (control) to 1000, 1000, 5000, and 2000 microg/mL, respectively, for 96 hours. Cytotoxicity was evaluated using the MTT colorimetric assay. Six replicates were used for each data point, and the results are reported as the mean +/- standard deviation.

RESULTS

Significant cytotoxicity (P <0.001) was seen, starting at 12.5 microg/mL (HTB9, TccSup) and 50 microg/mL (T24) for ciprofloxacin, 31.25 microg/mL (HTB9, TccSup) and 62.5 microg/mL (T24) for trimethoprim-sulfamethoxazole, 19.5 microg/mL (HTB9) and 156.3 microg/mL (T24, TccSup) for cefazolin, and 7.8 microg/mL (HTB9, T24, TccSup) for nitrofurantoin. Cytotoxicity was dose dependent for all four antibiotics, and the maximal effect did not differ among antibiotics.

CONCLUSIONS

Commonly used antibiotics exhibit significant dose-dependent cytotoxicity against bladder cancer cells at concentrations achievable in the urine after oral administration. The administration of antibiotics after transurethral resection of bladder tumors might prevent seeding of cancer cells and thereby decrease the recurrence rate. Preclinical data such as these must be considered in the design of clinical trials addressing recurrence after transurethral resection of bladder tumors.

Piperitone fromMentha longifolia var.chorodictya Rech F. reduces the nitrofurantoin resistance of strains of enterobacteriaceae

The diluted essential oil of Mentha longifolia (L.) var. chlorodictya Rech F. foliage enhanced the bactericidal activity of nitrofurantoin decreasing the minimum inhibitory concentration (MIC) of nitrofurantoin for nitrofurantoin-resistant strains of Enterobacteriaceae. Thin-layer chromatography (TLC) analysis of the essential oil detected a fraction (R(f) = 0.35, UV lambda(max) of 232.5), which was the most effective in enhancement of nitrofurantoin activity. Using gas liquid chromatography and known standards, the active fraction was identified as piperitone. 1 microl of the piperitone fraction decreased the MIC of nitrofurantoin 3-20 fold for the different strains of Enterobacteriaceae tested.

[Antibiotic susceptibility analysis of Enterococcus spp. isolated from urine]

Recently increase of enterococcal infections has been observed. These bacteria, mainly Enterococcus faecalis and Enterococcus faecium are members of the normal flora of gastrointestinal tract but also are typical opportunistic pathogens. Enterococci are characterized by natural resistance to numerous antibiotics (among them cephalosporins), and also by easy acquired resistance to antibiotics. Infections caused by multiresistant strains are difficult in treatment, chronic, recurrent and sometimes fatal are described. Enterococcal infections are caused often by E. faecalis, rarely by E. faecium. In the last years other species of enterococci have been isolated from different clinical materials (E. casseliflavus, E. avium, E. durans, E. gallinarum). The aim of this study was to analyze the antibiotics susceptibility of Enterococcus spp. isolated from urine of children with urinary tract infection (UTI), hospitalized in the Upper Silesian Health Center of Child and Mother or treated ambulatory. Susceptibility of the 130 strains of E. faecalis and 41 E. faecium to: penicillin, tetracycline, high level of aminoglycoside (gentamycin 120 microg and streptomycin 300 microg), glycopeptides (vancomycin and teicoplanin), ciprofloxacin and nitrofurantoin was estimated. All isolated strains of E. faecalis (100%) were sensitive to glycopeptides (vancomycin and teicoplanin) and to nitrofurantoin, 96% strains were sensitive to penicillin, 43% to ciprofloxacin and 28% to tetracycline. All strains of E. faecium were sensitive to glycopeptides (vancomycin and teicoplanin), 32% strains were sensitive to penicillin, 19% to tetracycline 14% to ciprofloxacin and 50% to nitrofurantoin. Twenty two strains of E. faecalis (17%) and twelve strains of E. faecium (29%) were demonstrated high level resistance to aminoglycosides (HLAR). Among HLAR strains of enterococci, were observed strains of high level resistance only to streptomycin, high level resistance only to gentamycin and high level resistance to both aminoglycosides. The HLAR strains of E. faecalis and E. faecium were also resistant to other antibiotics: penicillin, tetracycline and ciprofloxacin. The most frequent cause of child urinary tract infection was E. faecalis, with high sensitivity to penicillins, glycopeptides and nitrofurantoin. The increased role of E. faecium and other strains of enterococci also has been shown. These species demonstrated sensitivity to glycopeptides, but resistance to other antibiotics, routinely used for treatment of UTI as well as to nitrofurantoin.

In vitro evaluation of a new treatment for urinary tract infections caused by nitrate-reducing bacteria

Dietary and endogenous nitrates are excreted in urine, and during infection with nitrate-reducing bacteria they are reduced to nitrite. At a low pH nitrite is converted to a variety of nitrogen oxides that are toxic to bacteria. We hypothesized that acidification of nitrite-rich infected urine would result in the killing of the nitrate-reducing bacteria. An Escherichia coli control strain and a mutant lacking nitrate reductase activity were preincubated in urine supplemented with sodium nitrate (0 to 10 mM) at pH 7.0. Then, the nitrite-containing bacterial culture was transferred (and diluted 1/10) to slightly acidic urine (pH 5 and 5.5) containing ascorbic acid (10 mM) and growth was monitored. The control strain produced nitrite in amounts related to the amount of nitrate added. This strain was killed when the culture was transferred to acidic urine. In contrast, the mutant that did not produce nitrite retained full viability. When control bacteria were grown in acidic urine with nitrate and ascorbic acid present from the start of the experiment, no inhibition of growth was noted. The MICs and minimal bactericidal concentrations of sodium nitrite-ascorbic acid in acidic urine were comparable to those of conventional antibiotics. Preincubation of nitrate-reducing E. coli in nitrate-rich urine leads to the accumulation of nitrite. Subsequent acidification of the urine results in generation of nitrogen oxides that are bactericidal. Killing, however, requires a sequential procedure in which the bacteria are first allowed to grow in a nitrate-rich neutral environment, later followed by acidification. We speculate that ingestion of nitrate followed some hours later by acidification of urine could be a new therapeutic strategy for the treatment of urinary tract infections.

Fluoroquinolones and resistance in the treatment of uncomplicated urinary tract infection

Acute uncomplicated cystitis is one of the most common problems for which young women seek medical attention. Most of these infections are caused by Escherichia coli which are susceptible to many oral antimicrobials, although resistance is increasing to some of the commonly used agents, especially trimethoprim/sulphamethoxazole (TMP/SMX). In women with risk factors for infection with resistant bacteria, or in the setting of a high prevalence of TMP/SMX resistance, a fluoroquinolone or nitrofurantoin should be considered for empirical treatment. Use of nitrofurantoin does not share cross-resistance with more commonly prescribed antimicrobials and its more widespread use is justified from a public health perspective as a fluoroquinolone-sparing agent. beta-lactams and fosfomycin should be considered second-line agents for empirical treatment of cystitis. For acute uncomplicated pyelonephritis, fluoroquinolones are superior to TMP/SMX for empirical therapy due to the relatively high prevalence of TMP/SMX resistance among uropathogens causing pyelonephritis. TMP/SMX, effective for patients with mild to moderate disease, is an appropriate drug if the uropathogen is known to be susceptible. It is reasonable to use a 7-10 day oral fluoroquinolone regimen for outpatient management of mild to moderate pyelonephritis in the setting of a susceptible causative pathogen and rapid clinical response to therapy. Most women with acute uncomplicated pyelonephritis are now managed safely and effectively as outpatients.

Increasing prevalence of antibiotic resistance and multi drug resistance among uropathogens

A study was conducted to examine the prevalence of antibiotic resistance in the strains of bacteria isolated from patients with suspected urinary tract infection. A total of 348 bacterial isolates were grown from semi quantitative urine culture and were of significant bacteriuria. The antibiotic susceptibility testing was performed on Muller-Hinton agar by disc diffusion method according to the standard criteria of the National Committee for Clinical Laboratory Standards, Antibiotic susceptibility testing revealed a high prevalence of resistance to ampicillin (55.4%) followed by nitrofurantoin (45.4%), gentamicin (45.1%), amikacin (41.4%) and co-trimoxazole (30.5%). E. coli and Klebsiella pneumonia showed 78.8 % and 75.3 % resistance to three or more drugs respectively. Cefotaxime (87.1%) appeared to be the most active antibiotic against the majority of isolates, followed by Norfloxacin (83.3%).