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J S Wolfson

Publications and source records attributed to J S Wolfson.

At least 19 recordsLinked to original sources
PubMed1993

Limitations of plasmid complementation test for determination of quinolone resistance due to changes in the gyrase A protein and identification of conditional quinolone resistance locus.

Plasmid pJSW101 derived from pUC19 and carrying the wild-type gyrA gene was found to be unstable in HM72, a quinolone-resistant (QR) clinical isolate of Escherichia coli, and resulted in no change in quinolone MICs. MICs determined in the presence of ampicillin to ensure plasmid presence, however, resulted in complementation. HM72 was proved to have a gyrA mutation based on the DNA sequence of a 418-bp fragment of gyrA. DNA sequencing identified a common mutation encoding Leu-83 as the cause of QR. To identify loci other than gyrA and nfxB contributing to QR in KF111b, zgh-3075::Tn10 (67 min) in CAG12152 was transduced into KF111b. Sixteen percent of the transductants had a fourfold decrease in norfloxacin MIC, indicating the presence of a locus, nfxD, which contributes to QR. Outcross of nfxD from DH151 (gyrA nfxB nfxD zgh-3075::Tn10) resulted in 8% of the KF130 gyrA, 2% of the EN226-3 gyrA, and none of the KL16 (wild-type) transductants, with a four- to eightfold increase in norfloxacin MIC. In the presence of ampicillin, the resistance of a gyrA nfxD double mutant, DH161 nfxD gyrA (from EN226-3), was fully complemented by gyrA+. Thus, gyrA+ plasmid complementation tests for QR may be falsely negative with plasmid instability, a difficulty which may be circumvented by maintenance of plasmid selection. In addition, if nfxD-like mutations occur in gyrA clinical isolates, a positive test may overestimate the level of resistance attributable to gyrA alone.

4-Quinolones↗
PubMed1992

Synergism of trimethoprim and ciprofloxacin in vitro against clinical bacterial isolates.

For the first time, the effects of combinations of trimethoprim and a fluoroquinolone (ciprofloxacin) against gram-positive and gram-negative bacterial isolates were evaluated in vitro. Synergism was found in 31% (fractional inhibitory concentration, FIC) and 33% (fractional bactericidal concentration, FBC) of 121 clinical isolates of various bacterial strains, most often in Escherichia coli, staphylococci, and enterococci. Antagonism occurred in 1% (FIC) and 3% (FBC). The combination of trimethoprim and ciprofloxacin merits further evaluation for potential usefulness as a clinical regimen.

Ciprofloxacin↗
PubMed1992

Genetics and regulation of outer membrane protein expression by quinolone resistance loci nfxB, nfxC, and cfxB.

Quinolone resistance mutations (cfxB1, marA1, and soxQ1) that reduce porin outer membrane protein OmpF map near 34 min on the Escherichia coli chromosome. Another such mutation, nfxC1, was found in strain KF131 (nfxB, 19 min). nfxC1 and cfxB1 mutants (selected with quinolones) differed slightly but reproducibly from marA1 (selected with tetracycline) and soxQ1 (selected with menadione) mutants in quinolone resistance and linkage to zdd2208::Tn10kan (33.7 min). For nfxB nfxC1 and cfxB1 mutants, as previously shown for marA mutants, resistance and reduced OmpF required the micF locus encoding an antisense RNA complementary to ompF mRNA and were associated with increased micF expression.

4-Quinolones↗
PubMed1991

Overview of fluoroquinolone safety.

The safety of the fluoroquinolone antimicrobial agents is reviewed, discussing documented and potential clinical and laboratory adverse effects and drug-drug interactions. In prospective, randomized, double-blind clinical trials comparing fluoroquinolones to nonquinolone drugs or placebo, the fluoroquinolones were not significantly different (22 studies) or were superior (5 studies) to comparison agents but were only rarely more toxic (2 studies). Adverse effects included mild gastrointestinal toxicities and less common but more problematic central nervous system toxicities. Clinically important interactions occurred with coadministration of antacids and all fluoroquinolones and with theophylline and enoxacin and to a lesser extent ciprofloxacin and pefloxacin but not other fluoroquinolones. Potential adverse effects such as cartilage damage, DNA damage, teratogenicity, and crystalluria, while of concern, have not as yet been shown to be of clinical importance. Therapy of bacterial infections in children and adolescents is relatively contraindicated, but growing clinical experience with treatment of these patients has not so far revealed serious bone or cartilage toxicity. The fluoroquinolones thus far have exhibited a favorable safety profile, but our clinical experience is still limited, and monitoring for as yet unappreciated toxicities is warranted.

4-Quinolones↗
PubMed1991

Mode of action of the new quinolones: new data.

New details of the molecular interactions of quinolones with their target DNA gyrase and DNA have come from the nucleotide sequences of the gyrA genes from resistant mutants of Escherichia coli and wild-type strains of other bacteria and studies of gyrase A tryptic fragments, all suggesting the importance of an amino-terminal domain in quinolone action. Alterations in DNA supertwisting were also associated with altered quinolone susceptibility, possibly by indirect effects on DNA gyrase expression. Specific binding of relevant concentrations of norfloxacin to a complex of DNA gyrase and DNA in the presence of ATP, the cooperativity of DNA binding, and the crystalline structure of nalidixic acid have led to a model in which quinolones bind cooperatively to a pocket of single-strand DNA created by DNA gyrase. Quinolones vary in their relative activity against DNA gyrase and its eukaryotic homolog topoisomerase II, and in some assays increased action against the eukaryotic enzyme was associated with genotoxicity. Inhibition of bacterial DNA synthesis by quinolones may correlate with MICs in some species, but comparisons of drug accumulation and inhibition of DNA synthesis in permeabilized cells among species have been difficult to interpret. The specific factors necessary for bacterial killing by quinolones in addition to interaction with DNA gyrase have remained elusive, but include oxygen and new protein synthesis. The coordinate expression of the SOS proteins appears not to be necessary for quinolone lethality. Two independent mutants with selective reduced killing by quinolones and beta-lactams indicate overlap in the pathways of bactericidal activity of these classes of agents with distinct targets.

4-Quinolones↗
PubMed1991

Pharmacokinetics of quinolones: newer aspects.

Differences in pharmacokinetic properties are emerging as important determinants in distinguishing among clinical uses of individual new quinolone antimicrobial agents. Selected data on pharmacokinetics, new pharmacokinetic studies, and pharmacodynamics are reviewed, with reference to norfloxacin, ciprofloxacin, ofloxacin, pefloxacin, enoxacin, fleroxacin, lomefloxacin, and other new quinolones. Considering pharmacokinetics, oral bioavailability is excellent (greater than 95%) for most quinolones. Differences in peak serum concentrations and beta-half-lives of elimination exist, however, and are reflected in up to ten-fold differences in values of the area under the curve of serum concentration versus time for administration of similar drug doses. As suggested by high apparent volumes of distribution and low binding to serum proteins, penetration into many body tissues and fluids is favorable. Considering new findings, orally administered ciprofloxacin has been found to be absorbed primarily in the duodenum and jejunum. Studies also suggest this drug to be cleared by transepithelial elimination into the bowel lumen as well as by the renal route. Oral bioavailability of quinolones has been demonstrated to be in general good in ill as well as healthy subjects but is reduced on co-administration with magnesium- and aluminum-containing acids, sucralfate (which contains aluminum), or ferrous sulfate. Pharmacodynamic parameters, such as the relationship of serum concentrations and drug potency in vitro to clinical response and suppression of bacterial resistance, have been little studied and merit further investigation.

4-Quinolones↗
PubMed1991

A novel locus conferring fluoroquinolone resistance in Staphylococcus aureus.

Fluoroquinolones such as ciprofloxacin and ofloxacin are potent antimicrobial agents that antagonize the A subunit of DNA gyrase. We selected and mapped a novel fluoroquinolone resistance gene on the Staphylococcus aureus chromosome. Resistant mutants were selected with ciprofloxacin or ofloxacin and were uniformly localized to the A fragment of chromosomal DNA digested with SmaI and arrayed by pulsed-field gel electrophoresis. Several mutants (cfxB, ofxC) were genetically mapped between the thr and trp loci in the A fragment. A majority of A fragment fluoroquinolone resistance mutations were associated with reduced susceptibility to novobiocin, an antagonist of the B subunit of DNA gyrase. Two genes previously associated with fluoroquinolone resistance, the gyrA gene of DNA gyrase and the norA gene (associated with decreased drug accumulation), were localized to the G and D fragments, respectively. Thus, the fluoroquinolone resistance mutations in the A fragment are distinct from previously identified fluoroquinolone resistance mutations in gyrA and norA. Whether mutations in the A fragment after a second topoisomerase or another gene controlling supercoiling or affect drug permeation is unknown.

Anti-Infective Agents↗
PubMed1990

Mutants of Escherichia coli K-12 exhibiting reduced killing by both quinolone and beta-lactam antimicrobial agents.

Norfloxacin, ofloxacin, and other new quinolones, which are antagonists of the enzyme DNA gyrase, rapidly kill bacteria by largely unknown mechanisms. Earlier, we isolated, after mutagenesis, Escherichia coli DS1, which exhibited reduced killing by quinolones. We evaluated the killing of DS1 and several other strains by quinolones and beta-lactams. In time-killing studies with norfloxacin, DS1 was killed 1 to 2 log10 units compared to 4 to 5 log10 units for the wild-type parent strain KL16, thus revealing that DS1 is a high-persistence (hip) mutant. DS1 exhibited a similar high-persistence pattern for the beta-lactam ampicillin and reduced killing by drugs that differed in their affinities for penicillin-binding proteins, including cefoxitin, cefsulodin, imipenem, mecillinam, and piperacillin. Conjugation and P1 transduction studies identified a novel mutant locus (termed hipQ) in the 2-min region of the DS1 chromosome necessary for reduced killing by norfloxacin and ampicillin. E. coli KL500, which was isolated for reduced killing by norfloxacin without mutagenesis, exhibited reduced killing by ampicillin. E. coli HM23, a hipA (34 min) mutant that was isolated earlier for reduced killing by ampicillin, also exhibited high persistence to norfloxacin. DS1 differed from HM23, however, in the map location of its hip mutation, lack of cold sensitivity, and reduced killing by coumermycin. Results of these studies with strains DS1, KL500, and HM23 demonstrate overlap in the pathways of killing of E. coli by quinolones and beta-lactams and identify hipQ, a new mutant locus that is involved in a high-persistence pattern of reduced killing by norfloxacin and ampicillin.

Anti-Bacterial Agents↗
PubMed1990

Blinded comparison of a direct immunofluorescent monoclonal antibody staining method and a Giemsa staining method for identification of Pneumocystis carinii in induced sputum and bronchoalveolar lavage specimens of patients infected with human immunodeficiency virus.

A new direct immunofluorescence monoclonal antibody (DFA) method (Genetic Systems, Inc., Seattle, Wash.) for identification of Pneumocystis carinii in induced sputum and bronchoalveolar lavage specimens was compared in a blinded study with an established Giemsa stain method. We evaluated 148 consecutive clinical specimens from 104 patients with the following results. For the 67 patients (64%) infected with the human immunodeficiency virus (HIV), 49 were initially negative by both the DFA and the Giemsa methods, none were negative by DFA and positive by Giemsa, 6 were positive by DFA and negative by Giemsa, and 12 were positive by both methods, for a sensitivity and a negative predictive value of greater than 99%. For the six patients positive by DFA and negative by Giemsa, all were positive by both methods on evaluation of subsequently obtained clinical specimens, suggesting a specificity of greater than 99% and a false-positive rate of less than 1%. For 37 patients whose HIV status was negative or unknown, 35 were negative by both methods and 2 were positive by DFA and negative by Giemsa. The DFA method was simple to perform and required less time for scoring of stained slides than the Giemsa method, but care had to be taken to avoid false-positive readings due to extraneous fluorescence. This study indicates that the DFA method represents an advance as a sensitive, simple, and rapid way to identify P. carinii in induced sputum and bronchoalveolar lavage specimens from HIV-infected patients and suggests greater sensitivity of the DFA than the Giemsa method in this patient population.

Antibodies, Monoclonal↗
PubMed1989

Bacterial resistance to the quinolone antimicrobial agents.

Bacterial resistance to the newer quinolones occurs less frequently than to the older analogue nalidixic acid. Single-step mutations conferring greater than eightfold increases in minimal inhibitory concentration occur at frequencies of less than 10(-10) for many bacterial species and at 10(-8) for Pseudomonas aeruginosa. Passage on increasing concentrations of quinolones, however, results in highly resistant strains of many species. Chromosomal mutations have been shown to produce two mechanisms of resistance, alterations in the A subunit of the target enzyme, DNA gyrase, and decreased drug accumulation associated with altered porin outer membrane proteins and pleiotropic resistance. For some mutants reduced accumulation appears to depend on active quinolone efflux across the inner membrane. Resistance developing during quinolone therapy of infections has been infrequent to date and reported most often with P. aeruginosa and Staphylococcus aureus, and at sites with poor quinolone penetration or foreign bodies. Resistance should be monitored, and the means for limiting its development studied.

4-Quinolones↗
PubMed1989

Comparative pharmacokinetics of ofloxacin and ciprofloxacin.

Review of publications in which the pharmacokinetics of ofloxacin and ciprofloxacin were compared directly indicates that although similar in many respects, these fluoroquinolones exhibit three differences that may be important clinically. First, ofloxacin is more completely absorbed, achieves higher peak serum concentrations, and has a longer terminal elimination half-life, which result in a fivefold greater area under the curve than that of ciprofloxacin when similar doses are orally administered. Ofloxacin's more favorable pharmacokinetic profile seems to compensate at least in part for the greater activity of ciprofloxacin against gram-negative bacilli in vitro. Second, ofloxacin is eliminated almost entirely via the kidneys, whereas ciprofloxacin is eliminated via both the kidneys and non-renal routes. This suggests that ciprofloxacin may be preferable for patients with variable renal function, whereas ofloxacin may be preferable for patients receiving dialysis because of the need for less frequent administration. Third, concomitant use of ciprofloxacin with either theophylline or caffeine decreases elimination and thereby results in elevated serum concentrations of these methylxanthine derivatives. Because ofloxacin does not cause clinically significant alterations in the pharmacokinetics of either theophylline or caffeine, it may be preferable for patients using these concomitantly.

Biological Availability↗
PubMed1989

Quinolone antimicrobial agents: adverse effects and bacterial resistance.

Adverse effects, drug-drug interactions and bacterial resistance to the new quinolone antimicrobial agents are reviewed. Clinical adverse effects are reported to occur in 5-10% of patients, and include primarily gastrointestinal disturbances, central nervous system toxicity and rash. Laboratory abnormalities are reported to occur in 5-12% of patients, and include mild reversible elevations of transaminases. Quinolones are not recommended in persons whose bone growth is incomplete or in pregnant or nursing women because cartilage toxicity has been observed in juvenile beagles. Drug-drug interactions may occur between quinolones and theophylline, caffeine, and magnesium- or aluminium-containing compounds such as antacids and sucralfate. Bacterial resistance occurs by chromosomal mutations which alter the target enzyme DNA gyrase or decrease drug accumulation. Emergence of resistance during therapy is uncommon to date but can be problematic in infections with Pseudomonas aeruginosa. Staphylococcus aureus and other bacteria for which the therapeutic index may be low. In summary, quinolones thus far have been well tolerated, but more experience is needed to determine the exact nature and extent of adverse effects and emergence of bacterial resistance.

4-Quinolones↗
PubMed1989

Mechanisms of quinolone resistance in Escherichia coli: characterization of nfxB and cfxB, two mutant resistance loci decreasing norfloxacin accumulation.

Two genetic loci selected for norfloxacin (nfxB) and ciprofloxacin (cfxB) resistance were characterized. Both mutations have previously been shown to confer pleiotropic resistance to quinolones, chloramphenicol, and tetracycline and to decrease expression of porin outer-membrane protein OmpF. nfxB was shown to map at about 19 min and thus to be genetically distinct from ompF (21 min), and cfxB was shown to be very closely linked to marA (34 min). cfxB was dominant over cfxB+ in merodiploids, in contrast to other quinolone resistance mutations. The two loci appear to interact functionally, because nfxB was not expressed in the presence of marA::Tn5. Both nfxB and cfxB decreased the expression of ompF up to 50-fold at the posttranscriptional level as determined in strains containing ompF-lacZ operon and protein fusions. Both mutations also decreased norfloxacin accumulation in intact cells. This decrease in accumulation was abolished by energy inhibitors and by removal of the outer membrane. These findings, in conjunction with those of Cohen et al. (S. P. Cohen, D. C. Hooper, J. S. Wolfson, K. S. Souza, L. M. McMurry, and S. B. Levy, Antimicrob. Agents Chemother. 32:1187-1191, 1988), suggest a model for quinolone resistance by decreased permeation in which decreased diffusion through porin channels in the outer membrane interacts with a saturable drug efflux system at the inner membrane.

Anti-Infective Agents↗