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PubMed1996

Quinolone resistance mutations in the gyrA gene of clinical isolates of Salmonella.

S. typhimurium AlhR, S. enteritidis OulR, and S. hadar GueR resistant to fluoroquinolones (QR), ciprofloxacin MICs, 0.25 to 1 microgram/ml; norfloxacin MICs, 0.5 to 4 micrograms/ml; nalidixic acid MIC, 256 micrograms/ml were isolated from urinary tract infections (AlhR and OulR) during FQ therapy in immunocompromised patients infected by the parent FQ-susceptible strains (AlhS and OulS) (ciprofloxacin MICs, 0.032-0.063; norfloxacin MICs, 0.125-0.25; nalidixic acid MICs, 4-8) or from intestinal infection (GueR). Transformation of AlhR, OulR, and GueR by plasmid pJSW101 carrying the wild-type gyrA gene of Escherichia coli resulted in complementation (nalidixic acid MICs, 4 to 8), proving that these strains had a gyrA mutation. A 800-bp fragment of gyrA from the five strains was amplified by PCR. Direct DNA sequencing of 252-bp region of this fragment identified a single point mutation leading to a substitution Ser-83 to Tyr in AlhR and to a substitution Ser-83 to Phe in OulR and in GueR. These results emphasize the potential risk of selection of FQ-resistant Salmonella during FQ therapy in immunocompromised patients and suggest that these strains differ from the parent strains at least by one mutation in the gyrA gene. They also confirm the role of substitutions in position 83 of gyrA in FQ-resistant clinical isolates of Salmonella.

Anti-Infective Agents↗
PubMed1996

Quinolone effects in the SOS chromotest and the synthesis of biomacromolecules.

The genotoxicity of quinolone antibiotics (ciprofloxacin, enoxacin, nalidixic acid, norfloxacin, ofloxacin, pefloxacin) was studied on the selected mutant E. coli strain PQ 37 (SOS chromotest). The genotoxicity was expressed by SOS-inducing potential (SOSIP) values. The highest SOSIP values were found with ciprofloxacin (SOSIP = 1967 delta IF/nmol), the lowest value was observed with nalidixic acid (SOSIP = 0.3 delta IF/nmol). Similar results were also found with the biosynthesis of nucleic acids, as indicated by incorporation of 14C-adenine into TCA-insoluble fractions of S. typhimurium cells (ciprofloxacin IC50 = 0.39, nalidixic acid IC50 = 400). DNA-damaging effects were tested in the absence of an exogenous metabolizing system.

4-Quinolones↗
PubMed2002

In vitro activity of clinafloxacin in comparison with other quinolones against Stenotrophomonas maltophilia clinical isolates in the presence and absence of reserpine.

A total of 33 Stenotrophomonas maltophilia clinical isolates were tested for their susceptibility to clinafloxacin in comparison with ciprofloxacin, levofloxacin, moxifloxacin, nalidixic acid, norfloxacin, sparfloxacin and trovafloxacin. The MIC(50) and MIC(90) were as follows: ciprofloxacin 4 and 64 microg/mL; clinafoxacin 0.5 and 4 microg/mL; levofloxacin 2 and 32 microg/mL; moxifloxacin 1 and 8 microg/mL; nalidixic acid 8 and 128 microg/mL; norfloxacin 64 and 256 microg/mL; sparfloxacin 1 and 16 microg/mL; and trovafloxacin 1 and 8 microg/mL. Clinafloxacin was the most active quinolone, with only a 15.1% of strains showing resistance. When the MICs were determined in the presence of 25 microg/ml of reserpine, the MIC(90) of trovafloxacin and moxifloxacin did not change, whereas decreased 2-fold for clinafloxacin, levofloxacin, sparfloxacin and nalidixic acid, and 4- and 8-fold for ciprofloxacin and norfloxacin respectively. No clinafloxacin-resistant strains were observed when the MIC was performed in the presence of reserpine. Therefore, clinafloxacin shows the better "in vitro"activity against these 33 strains of S.maltophilia.

Anti-Infective Agents↗
PubMed2001

Comparison of minimum inhibitory concentration values for fluoroquinolones against Escherichia coli causing urinary tract infection in both hospitalized patients and outpatients.

OBJECTIVE: To determine the resistance among Escherichia coli isolates causing urinary tract infections in hospitalized patients and outpatients. METHODS: This study was carried out in the Department of Microbiology, Dokuz Eylul University, Medical Faculty Hospital, Inciralti, Ismir, Turkey, from February 1997 through to June 1998. A total of 300 Escherichia coli strains were isolated from urine specimens of 111 hospitalized and 189 elderly outpatients (more than 20 years of age). We determined the minimum inhibitory concentrations of the test drugs nalidixic acid, pefloxacin, ofloxacin, norfloxacin and ciprofloxacin by the microdilution method, recommended by the National Committee for Clinical Laboratory Standards. RESULTS: Minimum inhibitory concentrations(50) and minimum inhibitory concentrations(90) values of strains tested against fluoroquinolones, pefloxacin and nalidixic acid were the same for strains isolated from hospitalized and outpatients (0.125 microg/ml outpatients (0.03 microg/ml). Twenty-six (9%) of 300 Escherichia coli strains were resistant to all drugs used. Twenty (77%) of these 26 strains were isolated from hospitalized patients. We found that the resistance to nalidixic acid is much higher than other fluoroquinolones. At the same time, the resistance in the strains that were isolated from hospitalized patients is again higher than outpatient strains (46%). CONCLUSION: Resistance among Escherichia coli isolates from patients to quinolones used in the treatment of urinary tract infections was rare during this period. Our study, like many other reports showed the increased resistance to fluoroquinolones for clinical isolates. However the appearance of multi resistant clones and the elevated prevalence of quinolones resistance in the hospital studied are warning signals for an increase in resistant strains as seen in many other countries. Therefore, it is important for physicians to use fluoroquinolones carefully so as to prevent, or delay, the emergence of resistant strains.

Ambulatory Care↗
PubMed2001

Antibiotic resistance and sero-groups of shigella among paediatric out-patients in southwest Ethiopia.

OBJECTIVE: To determine the prevalence of Shigella sero-groups and resistance pattern of isolates to commonly used antibiotics in Jimma. DESIGN: Cross-sectional survey. SETTING: The study was conducted in Jimma, southwest Ethiopia. SUBJECTS: A total of 384 paediatric out-patients with diarrhoea aged 14 years and below were studied. METHODS: Stool specimens were collected from children presenting with diarrhoea using Cary-Blair transport medium and buffer treated swabs from Jimma hospital and Jimma health centre. Isolation, biochemical characterisation, sero-grouping and antibiotic sensitivity testing were performed according to standard methodology in the Microbiology laboratory of Jimma University. RESULTS: Out of the 77 Shigella strains isolated, sero-group A comprised 29.9%, B 40.3%, C 19.5% and D 10.4%. Among all Shigella sero-groups, highest resistance was encountered to tetracycline (63.6%), ampicillin (70.1%), cephalothin (57.1%), trimethoprim-sulphamethoxazole (32.5%) and chloramphenicol (40.3%) whileleast resistance was observed to gentamicin (1.3%), polymyxin B (3.9%) and nalidixic acid (6.5%). CONCLUSION: Gentamicin, polymyxin B and nalidixic acid were found to be the drugs of choice for cases related with shigellosis.

Adolescent↗
PubMedDate not supplied

[Optimization of the growth of Paenibacillus larvae in semi-selective media].

The sensitivity of media MYPGP, MYPGP(NALPIA) A (6 microg/ml nalidixic acid and 10 microg/ml pipemidic acid) and MYPGP(NALPIA) B (9 microg/ml nalidixic acid and 20 microg/ml pipemidic acid) for the recovery of viable spores of Paenibacillus larvae from honey, was evaluated by using different incubation times and different spore concentrations. No significant differences between incubation times, spore concentration or culture media were found. In the case of the recovery of vegetative cells from PBS at different incubation times and different dilutions no significant differences were found between the incubation times or the dilutions tested, while significant differences were found in the three media when compared with one another, MYPGP(NALPIA)B providing the lowest recovery of vegetative cells. Considering these results, we propose the use of MYPGP(NALPIA)B to recover spores of P. larvae from honey, specially for honeys with heterogeneous populations of bacterial spores; when culturing vegetative cells, MYPGP or MYPGP(NALPIA)A must be used to obtain good growth.

Culture Media↗
PubMed1989

In vitro antimicrobial activity and susceptibility testing of ofloxacin. Current status.

The fluoroquinolone, ofloxacin, exhibits a broad antibacterial spectrum. Based on our data and a review of the literature, ofloxacin inhibited essentially 100 percent of staphylococci, including oxacillin-resistant strains, Haemophilus influenzae, Neisseria spp. and Branhamella catarrhalis. Ninety-five percent of Enterobacteriaceae were susceptible to ofloxacin. Pseudomonas aeruginosa and enterococci were less susceptible: 79 and 63 percent, respectively, were susceptible (minimal inhibitory concentration [MIC], less than or equal to 2.0 micrograms/ml); 15 and 25 percent, respectively, were intermediate (MIC, 4 micrograms/ml); 3 and 6 percent, respectively, were resistant (MIC, more than or equal to 4 micrograms/ml). Clostridium spp., including Clostridium difficile, were resistant to ofloxacin, but other anaerobic species, including the Bacteroides fragilis group (over 90 percent) were either susceptible or intermediate to ofloxacin. Ofloxacin is bactericidal; minimal bactericidal concentrations of ofloxacin rarely exceed the MICs by one doubling concentration. A modest inoculum effect has been observed with ofloxacin: MICs with inocula of 10(7) colony-forming units/ml are often two- to fourfold higher than those with inocula of 5 x 10(5) colony-forming units/ml. Susceptible organisms exposed serially to increasing concentrations of nalidixic acid developed increasing resistance to not only nalidixic acid, but also to all other quinolones, including ofloxacin. Correlations of disk diffusion inhibitory zone diameters using the 5-micrograms ofloxacin disk with ofloxacin MICs have been performed, and the disk diffusion zone diameter breakpoints recommended are: susceptible, greater than or equal to 16 mm; intermediate, 13 to 15 mm; resistant, less than or equal to 12 mm. Quality control parameters also are summarized.

Bacteria↗
PubMed2002

Antimicrobial resistance of Salmonella serotypes isolated from slaughter-age pigs and environmental samples.

The aim of this study was to determine the antimicrobial resistance patterns of Salmonella strains isolated from slaughter-age pigs and environmental samples collected at modern swine raising facilities in Brazil. Seventeen isolates of six serotypes of Salmonella enterica subsp. enterica were isolated out of 1,026 collected samples: Salmonella Typhimurium (1), Salmonella Agona (5), Salmonella Sandiego (5), Salmonella Rissen (1), Salmonella Senftenberg (4), and Salmonella Javiana (1). Resistance patterns were determined to extended-spectrum penicillin (ampicillin), broad-spectrum cephalosporins (cefotaxime and ceftriaxone), aminoglycosides (streptomycin, neomycin, gentamicin, amikacin, and tobramycin), narrow-spectrum quinolone (nalidixic acid), broad-spectrum quinolone (ciprofloxacin and norfloxacin), tetracycline, trimethoprim, and chloramphenicol. Antimicrobial resistance patterns varied among serotypes, but isolates from a single serotype consistently showed the same resistance profile. All isolates were resistant to tetracycline, streptomycin, and nalidixic acid. One isolate, Salmonella Rissen, was also resistant to cefotaxime and tobramycin. All serotypes were susceptible to ceftriaxone, norfloxacin, ciprofloxacin, ampicillin, gentamicin, and chloramphenicol. The high resistance to tetracycline and streptomycin may be linked to their common use as therapeutic drugs on the tested farms. No relation was seen between nalidixic acid and fluoroquinolone resistance.

Animal Feed↗
PubMed1990

Mechanisms of resistance to the 4-quinolone antibacterial agents.

Because of the close structural relationship of the fluorinated 4-quinolones to the parent compound nalidixic acid the mechanism of resistance is often perceived to be the same. However, it is clear that whilst the mechanism of resistance to fluorinated 4-quinolones is essentially the same, strains that are selected as resistant to nalidixic acid generally retain sensitivity to the newer agents. A number of mutations in the chromosome of Escherichia coli have been identified and these are described. These mutations affect the interaction of quinolones with their presumed targets (DNA gyrases) and the transport of quinolones through the cell membrane. A small number of other mutations giving rise to low-level resistance to nalidixic acid, which affect neither gyrase nor membrane function, are also recognized. Despite the recognition of these mutations, the practical application of this information is hampered by lack of knowledge of the normal uptake mechanisms, the processes involved in selection and maintenance of resistance, the relationship of resistance to pathogenicity and the frequency of occurrence of these mutations.

4-Quinolones↗
PubMed1987

[Effect of subinhibitory concentrations of antibiotics on the growth level of bacteria].

The effect of subinhibitory concentrations of 5 antibiotics on the growth rate of 2 bacteria (Staphylococcus aureus and Escherichia coli) has been studied. Chloramphenicol, dibekacin, netilmicin and nalidixic acid have a direct effect on the growth rate. Apparently, aminoglycosides and nalidixic acid have an accompanying effect on the affinity for the energizing substrate. Amoxicillin does not seem to be concerned by this 2 mechanisms. The interest of the estimation of the growth rate by an adaptative algorithm has been pointed out.

Anti-Bacterial Agents↗
PubMed1976

Linkages between deoxyribonucleic acid synthesis and cell division in Myxococcus xanthus.

Addition of chloramphenicol or 0.5 M glycerol to growing Myxococcus xanthus resulted in an immediate cessation of cell division and 40% net increase in deoxyribonucleic acid (DNA). Although the chloramphenicol-treated cells divided in the presence of nalidixic acid after chloramphenicol was removed, glycerol-induced myxospores required DNA synthesis for subsequent cell division. Myxospores prepared from chloramphenicol-treated cells lost this potential to divide in the presence of nalidixic acid. The "critical period" of DNA synthesis necessary for cell division after germination overlapped in time (3 to 5 h) with initiation of net DNA synthesis. The length of the critical period of DNA synthesis was estimated at 12 min, or 5% of the M. xanthus chromosome. The requirement for cell division during germination also involved ribonucleic acid and protein synthesis after DNA synthesis. The data suggest that replication at or near the origin of the chromosome triggers the formation of a protein product that is necessary but not sufficient for subsequent cell division; DNA termination is also required. During myxospore formation, the postulated protein is destroyed, thereby reestablishing and making apparent this linkage between early DNA synthesis and cell division.

Cell Division↗
PubMed1999

Harmonization of antibiotic susceptibility testing for Salmonella: results of a study by 18 national reference laboratories within the European Union-funded Enter-net group.

For the effective surveillance of antimicrobial drug resistance within Salmonella organisms from humans, harmonization of methods used for sensitivity testing by laboratories responsible for the typing of such organisms is essential. A study of resistance or sensitivity to a panel of 11 antimicrobials by the Enter-net international surveillance network was therefore undertaken. There are 18 national Salmonella reference laboratories within this European Union-funded network. Forty-eight strains of Salmonella enterica were distributed to each laboratory for testing for resistance or sensitivity to ampicillin, cefotaxime, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfonamides, tetracyclines, trimethoprim, nalidixic acid, and ciprofloxacin. Over 8,500 tests were assessed involving disk diffusion (DD), agar breakpoint (BP), or full minimum inhibitory concentration (MIC). Results indicated that whichever method was used, there was a high degree of concordance for the detection of resistance to most antimicrobials; only for decreased sensitivity to ciprofloxacin was there substantial nonconcordance. Because all isolates with decreased sensitivity to ciprofloxacin were resistant to nalidixic acid, it is suggested that, if required, MICs to ciprofloxacin could be determined for isolates resistant to nalidixic acid. For the detection of sensitivity, the main area of nonconcordance was in the detection of sensitivity to streptomycin. With the exception of decreased sensitivity to ciprofloxacin, we are confident that a database of antimicrobial susceptibilities can now be established and harmonized antibiogram data for Salmonella can now be exchanged for national Salmonella reference laboratories within the European Union.

Drug Resistance, Microbial↗
PubMed1986

In vivo transfer of antibiotic resistance to a strain of Salmonella arizonae.

Two trials were conducted to determine the transferability of antibiotic resistance in vivo between two strains of enteric bacteria. Newly hatched turkey poults were inoculated per os with a strain of Escherichia coli resistant to kanamycin, tetracycline, and ampicillin, a strain of Salmonella arizonae resistant to nalidixic acid and streptomycin, or both strains. Kanamycin was added to the drinking water of some poults. To test for S. arizonae cells which had received transferable resistance determinants in vivo from the E. coli strain, samples were collected by swabbing the recta of the poults and by removing segments of the intestines and livers after the birds were sacrificed. Nalidixic acid was added to the isolation media to prevent in vitro transfer from occurring after the samples were collected. Salmonella arizonae resistant to nalidixic acid, streptomycin, kanamycin, tetracycline, and ampicillin were isolated from 20% of the rectal samples taken from poults that had received both bacterial strains. S. arizonae cells which had received resistance determinants in vivo were also isolated from 73% of the intestinal samples and 8% of the liver samples taken from birds inoculated with both donor E. coli and recipient S. arizonae. Salmonella arizonae demonstrating resistance to all five antibiotics were recovered from all intestinal samples taken from birds given kanamycin in their drinking water immediately after the last S. arizonae inoculation but from only 43% of such samples taken from birds given no kanamycin.

Animals↗
PubMed1994

Susceptibilities to 10 antimicrobial agents of 1,220 Campylobacter strains isolated from 1987 to 1993 from feces of pediatric patients.

We report the in vitro antibiotic susceptibility of 1,220 strains belonging to the thermotolerant Campylobacter species, isolated from the feces of pediatric patients with diarrhea in the period from 1987 to 1993. The strains were identified as 1,148 C. jejuni isolates and 72 C. coli isolates. The overall results show that the strains showed drug resistance as follows: 51.8% to ampicillin, 4.4% to clindamycin, 2.6% to chloramphenicol, 21.2% to tetracycline, and 1% to gentamicin. Twenty-one strains (1.7%) displayed resistance to the combination of amoxicillin-clavulanic acid, and 3.2% of the strains were resistant to erythromycin (MIC of > or = 4 micrograms/ml), with a notable difference according to the species under consideration. While C. jejuni remained stable at 0.9 to 4% resistance to erythromycin, for C. coli the percentages detected ranged from 0 to 33%, with overall rates of 2.5 and 15.2% for the two species, respectively. Resistance to nalidixic acid (MIC of > or = 32 micrograms/ml) was found in 27.2% of the strains (27.8% for C. jejuni and 18% for C. coli), and resistance to ciprofloxacin (MIC of > or = 4 micrograms/ml) was found in 24.2% of the strains for C. jejuni and 15.2% for C. coli). Cross-resistance between nalidixic acid and ciprofloxacin was found in 89.1% of the strains (type 1 mutants), while 10.9% were resistant to nalidixic acid but susceptible to ciprofloxacin (type 2 mutants).

Anti-Bacterial Agents↗
PubMed2003

[Formation of virulent antigen-modified mutants (Fra-, Fra-Tox-) of plague bacteria resistant to rifampicin and quinolones].

Experiments were performed with two strains of plague bacteria--231 (isolated from marmot) and 358 (isolated from human) and their isogenic variants with Fra- and Fra-Tox- phenotype. Mutants resistant to rifampicin (Rifr) and nalidixic acid (Nalr) appeared independently of pathogen phenotype and genotype with frequency n.10(-8)-n.10(-9), subsequently. Rifr mutation influenced on virulence manifestation at albino mice and antigendeficient variants with Fra- and Fra-Tox- phenotype. In every group of strains highly virulent subcultures were registered. Resistance to nalidixic acid mainly was not associated with virulence loss. Nalr mutants of parent and antigenmodified mutants were cross resistant to fluoroqinolones (ciprofloxacin, ofloxacin, pefloxacin, lomefloxacin). LD50 for untreated albino mice did not differ from LD50, for mice treated with rifampicin (when mice were infected with strain resistant to rifampicin) or with nalidixic acid and fluoroquinolones (when animals were infected with Nalr mutants). Antigenmodified strains of plague bacteria and their Rifr, Nalr mutants were able to overcome specific immune reaction. The drugs should be used in synergic combinations (with aminoglycosides or cephalosporines of III generation) to prevent appearance of virulent strains resistant to rifampicin and fluroquinolones.

4-Quinolones↗