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PubMed1984

Cloning the gyrA gene of Bacillus subtilis.

We have isolated an eight kilobase fragment of Bacillus subtilis DNA by specific integration and excision of a plasmid containing a sequence adjacent to ribosomal operon rrn O. The genetic locus of the cloned fragment was verified by linkage of the integrated vector to nearby genetic markers using both transduction and transformation. Functional gyrA activity encoded by this fragment complements E. coli gyrA mutants. Recombination between the Bacillus sequences and the E. coli chromosome did not occur. The Bacillus wild type gyrA gene, which confers sensitivity to nalidixic acid, is dominant in E. coli as is the E. coli gene. The cloned DNA precisely defines the physical location of the gyrA mutation on the B. subtilis chromosome. Since an analogous fragment from a nalidixic acid resistant strain has also been isolated, and shown to transform B. subtilis to nalidixic acid resistance, both alleles have been cloned.

Bacillus subtilis↗
PubMed2000

Antimicrobial susceptibility pattern of Vibrio cholerae O1 strains during two cholera outbreaks in Dar es Salaam, Tanzania.

OBJECTIVE: To determine and compare the antimicrobial susceptibility patterns of Vibrio cholerae 01 strains, which were isolated in two cholera epidemics in 1997 and 1999 in Dar es Salaam. METHODS: V. cholerae 01 strains isolated from patients with cholera in Dar es Salaam city during 1997 (94 isolates) and 1999 (87 isolates) were stored on nutrient agar slants at room temperature and antimicrobial susceptibility pattern was determined, using Kirby Bauer method. SETTING: Department of Microbiology and Immunology, Muhimbili Medical Centre, Dar es Salaam, Tanzania. RESULTS: A total of 181 V. cholerae 01 strains were studied during two epidemic periods when tetracycline or erythromycin was used for treatment of patients with severe disease. Among the 94 V. cholerae 01 strains isolated in 1997; 98.6%, 93.6%, 83%, 81.9%, 36.2%, 35.5%, 3.2% were sensitive to ciprofloxacin, tetracycline, ampicillin, erythromycin, nalidixic acid, chloramphenicol and trimethoprim/sulphamethoxazole, respectively. Among the 87 V. cholerae 01 isolates collected in 1999, 100%, 58.6%, 46.0%, 46%, 47.1%, 19.5%, 3.4% were sensitive to ciprofloxacin, tetracycline, ampicillin, erythromycin, chloramphenicol, nalidixic acid and trimethoprim/sulphamethoxazole, respectively. Between 1997 and 1999, there was a significant increase in the proportion of V. cholerae 01 isolates resistant to tetracycline, ampicillin, nalidixic acid and to erythromycin but there was no change for susceptibility to ciprofloxacin and trimethoprim/sulphamethoxazole. CONCLUSION: Significant proportion of V. cholerae 01 strains in Dar es Salaam were resistant to commonly used antimicrobial agents during the two years of the study. Therefore, there is a great need to control the utilisation of antimicrobial agents in cholera control, in addition to continuing carrying out surveillance of antimicrobial resistance as a guide to choice of antimicrobial treatment. Rotational use of the available drugs with regular monitoring of susceptibility may contribute to continuing usefulness of such drugs.

Cholera↗
PubMed2002

Determination of oxolinic acid in the bryophyte Fontinalis antipyretica by liquid chromatography with fluorescence detection.

A large amount of oxolinic acid administered in freshwater fish farms reaches the environment. In order to allow environmental monitoring, an HPLC method to determine oxolinic acid in the bryophyte Fontinalis antipyretica was developed. Nalidixic acid was used as an internal standard. Oxolinic and nalidixic acids were extracted by cracking the bryophytes in liquid nitrogen with 0.1 M acid oxalic solution in ethyl acetate and a liquid-liquid clean up procedure was then performed. Mobile phase was a 0.02 M orthophosphoric acid aqueous solution-acetonitrile mixture (70:30, v/v). The stationary phase was 5 microm PuroSpher RP18e and quinolones were detected by fluorescence. The linearity, accuracy and precision of this method were demonstrated by a validation assay. The limits of detection and quantitation were 1 and 10 ng/g respectively. The linearity range was 10 to 500 ng/g. This method was applied to a 25 days experimental study performed with the bryophyte Fontinalis antipyretica.

Bryopsida↗
PubMed1986

Influence of oral intake of seven different antibiotics on faecal short-chain fatty acid excretion in healthy subjects.

Faecal excretion of short-chain fatty acids (SCFAs) has been measured by gas chromatography in groups of six or seven healthy subjects before, during, and after they received the antibiotics bacitracin, co-trimoxazol, doxycycline, erythromycin, nalidixic acid, ofloxazin, or vancomycin orally for 6 days. Intake of bacitracin and vancomycin had pronounced effects on faecal SCFAs excretion and reduced median total concentration of SCFAs from 105.4 mmol/kg to 21.8 mmol/kg and from 69.3 mmol/kg to 19.4 mmol/kg, respectively (p less than 0.05). Erythromycin had moderate effects on the faecal SCFAs excretion, whereas small or no changes were seen during intake of co-trimoxazol, doxycycline, nalidixic acid, and ofloxacin. 2-Methylbutyric acid, a SCFA not previously seen in human faeces, was found in the faeces of all subjects (median concentration before intake of antibiotic, 1.3 mmol/kg). Bacitracin, erythromycin, nalidixic acid, and vancomycin were detected in high concentrations in faeces during therapy, whereas trimethoprim, doxycycline, and ofloxacin were found in relatively low concentrations. In conclusion, some, but not all, peroral antimicrobials induce changes in faecal SCFAs, most likely reflecting changes in the colonic ecosystem.

Administration, Oral↗
PubMedDate not supplied

Antimicrobial drug resistance in nontyphoid human Salmonella in Belgium: trends for the period 2000-2002.

In order to assess antimicrobial resistance in nontyphoid human Salmonella in Belgium, the six most important serovars, representing together more than 90% of laboratory confirmed cases, were randomly sampled. From June 2000 until December 2002, a total of 1756 isolates were screened for their antimicrobial resistance profile by the disc diffusion method. S. Hadar strains showed the highest level of antimicrobial resistance. Simultaneous resistance to ampicillin, nalidixic acid, tetracycline and streptomycin was observed in 81.5, 58 and 76.1% of these isolates in 2000, 2001 and 2002, respectively. All S. Hadar isolates resistant to nalidixic acid also displayed decreased susceptibility to ciprofloxacin (MIC50 values of 0.25 microg/mL in 2000-2001 and 0.19 microg/mL in 2002). In 2000, 2001 and 2002, respectively 44.6, 46 and 36.5% of S. Typhimurium isolates were multiresistant (resistant to 4 or more antimicrobial agents). These multiresistant isolates were preferably associated with a few phage types, such as DT104. Complete resistance to ciprofloxacin was detected in three S. Typhimurium isolates and sequencing of the gyrA gene revealed for each isolate two mutations at codons corresponding to Ser-83 and Asp-87. Multiresistance was also common in S. Virchow (7.7%, 15.9% and 29.7%, in 2000, 2001 and 2002, respectively). Resistance to nalidixic acid in S. Virchow isolates increased from 46.2% in 2000 to 80.9% in 2002 and six S. Virchow isolates were detected as cefotaxime resistant. In contrast, the vast majority of S. Enteritidis, S. Brandenburg and S. Derby isolates remained sensitive to almost all antimicrobial agents tested.

Anti-Bacterial Agents↗
PubMed1993

[Compared antibacterial activity of a new fluoroquinolone, sparfloxacin (AT 4140, RP 64206) and four other fluoroquinolones against 332 strains of enteropathogen bacteria].

The in vitro bacteriostatic and bactericidal activity of five fluoroquinolones--sparfloxacin, ciprofloxacin, ofloxacin, lomefloxacin and pefloxacin--was tested against 332 strains of enteric pathogens belonging to the genera Salmonella, Shigella, Escherichia, Yersinia, Vibrio, Campylobacter and Helicobacter. Some of the strains were resistant to one or several antibiotics. Each fluoroquinolone showed identical bacteriostatic activity against susceptible and resistant strains except of those resistant to nalidixic acid. MIC 90% were always below 1 mg/l. The MIC were lowest with ciprofloxacin followed by sparfloxacin and highest with pefloxacin. The five compounds showed different activity against nalidixic acid resistant strains: MIC 90% increased from 0.06 to 4 mg/l for Salmonella, from 0.5 to 4 mg/l for C. jejuni strains, from 0.12 to 16 mg/l for H. pylori strains. All strains remained susceptible to ciprofloxacin and sparfloxacin, but some were intermediate or resistant to the three other compounds. The minimal bactericidal concentrations of the five agents against the nalidixic acid susceptible or resistant strains were one or two times the corresponding MIC.

Anti-Infective Agents↗
PubMed1994

Identification of DNA topoisomerases involved in immediate and transient DNA relaxation induced by heat shock in Escherichia coli.

The linking number of plasmid DNA in exponentially growing Escherichia coli increases immediately and transiently after heat shock. The purpose of this study was to search for DNA topoisomerases that catalyze this relaxation of DNA. Neither introduction of a topA deletion mutation nor treatment of cells with DNA gyrase inhibitors affected the DNA relaxation induced by heat shock. Thus, DNA topoisomerase I and DNA gyrase are apparently not involved in the process. However, the reaction was inhibited by nalidixic acid or by oxolinic acid in the topA mutant and the reaction was resistant to nalidixic acid in a topA mutant carrying, in addition, the nalA26 mutation. These results are interpreted as indicating that both DNA topoisomerase I and DNA gyrase are involved in the DNA relaxation induced by heat shock.

DNA Topoisomerases, Type I↗
PubMed1993

4-Quinolone bactericidal mechanisms.

The bactericidal activity of nalidixic acid against Escherichia coli strain KL16 in nutrient broth was abolished by the addition of rifampicin. Cells suspended in phosphate-buffered normal saline (PBS) were also not killed by nalidixic acid. Experiments with modern 4-quinolones showed their activities varied according to the conditions under which they were tested. Rifampicin did not affect the concentration at which ofloxacin became bactericidal in nutrient broth, but did limit the extent of ofloxacin-induced death. However, rifampicin produced a 10-fold increase in the concentration at which ciprofloxacin became bactericidal in nutrient broth, and completely abolished the bactericidal activity of norfloxacin. Unlike nalidixic acid all of the modern 4-quinolones killed cells suspended in PBS. Based on these results it was possible to differentiate 3 processes by which 4-quinolones induced death. Mechanism A was only active against dividing bacteria and required RNA and protein synthesis; it was therefore not active against bacteria suspended in PBS and was inhibited in nutrient broth by the addition of rifampicin. Mechanism B required neither RNA nor protein synthesis and was also active against non-dividing bacteria; it was therefore not inhibited by rifampicin nor by suspending bacteria in PBS. Mechanism C killed non-dividing bacteria, but required protein and RNA synthesis: it therefore functioned in PBS, but was inhibited by rifampicin.(ABSTRACT TRUNCATED AT 250 WORDS)

4-Quinolones↗
PubMed1983

Binding to faeces and influence on human anaerobes of antimicrobial agents used for selective decontamination.

The degree of binding of ampicillin, cephradine, co-trimoxazole, gentamicin, nalidixic acid, neomycin, polymyxin B and tobramycin by faecal substance as well as the influence of these antibiotics on human intestinal obligate anaerobes was investigated. In contrast to ampicillin, cephradine, co-trimoxazole and nalidixic acid, the nonabsorbable antibiotics polymyxin B and neomycin were bound to a considerable degree by human faeces. The binding of tobramycin and gentamicin to the solid part of faeces was less effective. The inhibitory effect of co-trimoxazole, gentamicin, nalidixic acid, neomycin, polymyxin B and tobramycin on the human obligate anaerobes was weak as compared with ampicillin and cephradine. Drugs which effectively eliminate Enterobacteriaceae from the gastrointestinal tract and which have a moderate effect on obligate anaerobes, like polymyxin B, are particularly suitable for selective decontamination of the gastrointestinal tract. The strong inactivating binding of aminoglycosides and polymyxin B to faeces accounts for the relatively high oral dose needed for a suitable faecal concentration.

Ampicillin↗
PubMed1975

Chromosome transfer in Proteus mirabilis mediated by hybrid plasmid.

A previously-described fused plasmid, P-lacRIdrd19, was found to mediate chromosomal transfer between cells of Proteus mirabilis strain PM5006; PM5006-(P-lacRIdrd19) was usually the donor and various auxotrophs of PM5006 resistant to nalidixic acid and/or streptomycin were recipients. The donor was usually counterselected with nalidixic acid and/or high concentrations of streptomycin. Recombination experiments with single markers indicated a 40-fold variation in recombination frequencies for different markers. Mapping double-auxotrophic markers by their gradient of transmission confirmed this variation and placed each of two independent isolates of eight markers in a linkage group his-ser-ura-pyrB-trp-cys-ade-ilv. Some donor markers did not register. Despite low recombination frequencies, interrupted mating experiments showed a polarity of early marker transfer. The segregation of unselected markers confirmed the order of some markers and showed that genetic material passed from the presumptive donor to the recipient. Recipients with two auxotrophic markers which could not be cotransduced by phage 5006M were converted to prototrophy by conjugation. The plasmid transferred to recipients at high frequency and all recombinants carried it. Recombinants could act as donors in further matings. Recombinants were fully susceptible to phage 5006M, unlike transductants of PM5006 by this phage. Direct involvement of the plasmid was indicated by drastically diminished recombination frequencies in crosses with recipients carrying P-lac as resident. P-lac had previously been shown to reduce the frequency of transfer of the hybrid plasmid to cells harbouring it. The histidine region was the first to register in recipients and recombined at the highest frequency of 5 times 10-6/donor cell. Some temporary association of plasmid and perhaps only the histidine region of the chromosome is favoured as the mechanism of chromosomal transfer. This could explain why not all donor markers could be mapped. Transduction and transformation were excluded as the cause of results.

Chromosome Mapping↗