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There has been renewed interest in combining traditional small-molecule antimicrobial agents with nontraditional therapies to potentiate antimicrobial effects. Apotransferrin, which decreases iron availability to microbes, is one such approach. We conducted a 48-h one-compartment infection model to explore the impact of apotransferrin on the bactericidal activity of ciprofloxacin. The challenge panel included four isolates with ciprofloxacin MIC values ranging from 0.08 to 32 mg/liter. Each challenge isolate was subjected to an ineffective ciprofloxacin monotherapy exposure (free-drug area under the concentration-time curve over 24 h divided by the MIC [AUC/MIC ratio] ranging from 0.19 to 96.6) with and without apotransferrin. As expected, the no-treatment and apotransferrin control arms showed unaltered prototypical logarithmic bacterial growth. We identified relationships between exposure and change in bacterial density for ciprofloxacin alone ( = 0.64) and ciprofloxacin in combination with apotransferrin ( = 0.84). Addition of apotransferrin to ciprofloxacin enabled a remarkable reduction in bacterial density across a wide range of ciprofloxacin exposures. For instance, at a ciprofloxacin AUC/MIC ratio of 20, ciprofloxacin monotherapy resulted in nearly 2 log CFU increase in bacterial density, while the combination of apotransferrin and ciprofloxacin resulted in 2 log CFU reduction in bacterial density. Furthermore, addition of apotransferrin significantly reduced the emergence of ciprofloxacin-resistant subpopulations compared to monotherapy. These data demonstrate that decreasing the rate of bacterial replication with apotransferrin in combination with antimicrobial therapy represents an opportunity to increase the magnitude of the bactericidal effect and to suppress the growth rate of drug-resistant subpopulations.
Copyright © 2019 American Society for Microbiology.
Fluoroquinolone exposure before tuberculosis (TB) diagnosis is common. We anticipated that exposure to older-generation fluoroquinolones is associated with greater fluoroquinolone MICs in Mycobacterium tuberculosis than exposure to newer agents. A nested case-control study was performed among newly diagnosed TB patients reported to the Tennessee Department of Health (January 2002-December 2009). Each fluoroquinolone-resistant case (n=25) was matched to two fluoroquinolone-susceptible controls (n=50). Ciprofloxacin and ofloxacin were classified as older-generation fluoroquinolones; levofloxacin, moxifloxacin and gatifloxacin were considered newer agents. There was no difference between median ofloxacin MIC for isolates from 9 patients exposed only to older fluoroquinolones, 25 exposed only to newer fluoroquinolones, 6 exposed to both and 35 fluoroquinolone-unexposed patients (Kruskal-Wallis, P=0.35). Using multivariate proportional odds logistic regression adjusting for age and sex, duration of exposure to newer fluoroquinolones was independently associated with higher MIC (OR=1.79, 95% CI 1.22-2.64), but duration of exposure to older fluoroquinolones was not (OR=0.94, 95% CI 0.50-1.78). Isolates from patients exposed only to newer fluoroquinolones tended to have mutations at gyrA codons 90, 91 or 94 more frequently than those exposed only to older fluoroquinolones (44% vs. 11%). We were surprised to find that duration of exposure to newer fluoroquinolones, but not older ones, was independently associated with higher ofloxacin MIC. This suggests that the mutant selection window lower boundary is likely to have clinical relevance; caution is warranted when newer fluoroquinolones are prescribed to patients with TB risk factors.
Copyright © 2013 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.
Although quinolones are the most commonly prescribed antibacterials, their use is threatened by an increasing prevalence of resistance. The most common causes of quinolone resistance are mutations of a specific serine or acidic residue in the A subunit of gyrase or topoisomerase IV. These amino acids are proposed to serve as a critical enzyme-quinolone interaction site by anchoring a water-metal ion bridge that coordinates drug binding. To probe the role of the proposed water-metal ion bridge, we characterized wild-type, GrlA(E85K), GrlA(S81F/E85K), GrlA(E85A), GrlA(S81F/E85A) and GrlA(S81F) Bacillus anthracis topoisomerase IV, their sensitivity to quinolones and related drugs and their use of metal ions. Mutations increased the Mg(2+) concentration required to produce maximal quinolone-induced DNA cleavage and restricted the divalent metal ions that could support quinolone activity. Individual mutation of Ser81 or Glu85 partially disrupted bridge function, whereas simultaneous mutation of both residues abrogated protein-quinolone interactions. Results provide functional evidence for the existence of the water-metal ion bridge, confirm that the serine and glutamic acid residues anchor the bridge, demonstrate that the bridge is the primary conduit for interactions between clinically relevant quinolones and topoisomerase IV and provide a likely mechanism for the most common causes of quinolone resistance.
BACKGROUND - In the last ten years, bioterrorism has become a serious threat and challenge to public health worldwide. Pulmonary anthrax caused by airborne Bacillus anthracis spores is a life-threatening disease often refractory to antimicrobial therapy. Inhaled spores germinate into vegetative forms that elaborate an anti-phagocytic capsule along with potent exotoxins which disrupt the signaling pathways governing the innate and adaptive immune responses and cause endothelial cell dysfunction leading to vascular injury in the lung, hypoxia, hemorrhage, and death.
METHODS/PRINCIPAL FINDINGS - Using a murine model of pulmonary anthrax disease, we showed that a nuclear transport modifier restored markers of the innate immune response in spore-infected animals. An 8-day protocol of single-dose ciprofloxacin had no significant effect on mortality (4% survival) of A/J mice lethally infected with B. anthracis Sterne. Strikingly, mice were much more likely to survive infection (52% survival) when treated with ciprofloxacin and a cell-penetrating peptide modifier of host nuclear transport, termed cSN50. In B. anthracis-infected animals treated with antibiotic alone, we detected a muted innate immune response manifested by cytokines, tumor necrosis factor alpha (TNFα), interleukin (IL)-6, and chemokine monocyte chemoattractant protein-1 (MCP-1), while the hypoxia biomarker, erythropoietin (EPO), was greatly elevated. In contrast, cSN50-treated mice receiving ciprofloxacin demonstrated a restored innate immune responsiveness and reduced EPO level. Consistent with this improvement of innate immunity response and suppression of hypoxia biomarker, surviving mice in the combination treatment group displayed minimal histopathologic signs of vascular injury and a marked reduction of anthrax bacilli in the lungs.
CONCLUSIONS - We demonstrate, for the first time, that regulating nuclear transport with a cell-penetrating modifier provides a cytoprotective effect, which enables the host's immune system to reduce its susceptibility to lethal B. anthracis infection. Thus, by combining a nuclear transport modifier with antimicrobial therapy we offer a novel adjunctive measure to control florid pulmonary anthrax disease.
OBJECTIVE - To determine whether a computerized decision support system could increase the proportion of oral quinolone antibiotic orders placed for hospitalized patients.
DESIGN - Prospective, interrupted time-series analysis.
SETTING - University hospital in the south-eastern United States.
SUBJECTS - Inpatient quinolone orders placed from 1 February 2001 to 31 January 2003.
INTERVENTION - A web-based intervention was deployed as part of an existing order entry system at a university hospital on 5 February 2002. Based on an automated query of active medication and diet orders, some users ordering intravenous quinolones were presented with a suggestion to consider choosing an oral formulation.
MAIN OUTCOME MEASURE - The proportion of inpatient quinolone orders placed for oral formulations before and after deployment of the intervention.
RESULTS - There were a total of 15 194 quinolone orders during the study period, of which 8962 (59%) were for oral forms. Orders for oral quinolones increased from 4202 (56%) before the intervention to 4760 (62%) after, without a change in total orders. In the time-series analysis, there was an overall 5.6% increase (95% CI 2.8-8.4%; P < 0.001) in weekly oral quinolone orders due to the intervention, with the greatest effect on nonintensive care medical units.
CONCLUSIONS - A web-based intervention was able to increase oral quinolone orders in hospitalized patients. This is one of the first studies to demonstrate a significant effect of a computerized intervention on dosing route within an antibiotic class. This model could be applied to other antibiotics or other drug classes with good oral bioavailability.
BACKGROUND - The empiric administration of anti-microbial therapy significantly reduces the morbidity and mortality associated with febrile neutropenic episodes in oncology patients. Outpatient empiric antibiotic therapy can be safely administered to a subset of febrile neutropenic patients at low risk for clinical complications.
PROCEDURE - Pediatric cancer patients presenting with febrile neutropenia after non-myeloablative chemotherapy and who met institutional criteria for early hospital discharge following a minimum of 48-hr inpatient empiric intravenous ceftazidime were eligible for the study. The feasibility and efficacy of an outpatient continuation therapy of oral ciprofloxacin (CPR) 25-30 mg/kg/day divided BID and amoxicillin (AMX) 30-50 mg/kg/day divided TID was assessed.
RESULTS - Thirty febrile neutropenic episodes in 26 patients were treated with outpatient oral CPR/AMX therapy. Oral CPR/AMX therapy was feasible in 28 (93%) and efficacious in 26 (87%) of treatment episodes. CPR/AMX was discontinued due to abdominal pain and diarrhea (n = 2), recurrent fever (n = 3), or gastrointestinal bleeding (n = 1). No patient developed new bacteremia or cardiopulmonary decompensation. Bone/joint pain or gastrointestinal symptoms occurred in 27% of treatment episodes. Duration of neutropenia, lower absolute neutrophil count (ANC) (< 100/mm(3)) at start of oral antibiotic therapy and active malignant disease were associated with failure of oral antibiotic therapy.
CONCLUSIONS - It is feasible to administer oral CPR/AMX as continuation antibiotic therapy for a selected subgroup of febrile neutropenic episodes defined after initial hospitalization and empiric antibiotic therapy. Prospectively randomized trials will be required to analyze adequately the efficacy of an oral CPR/AMX outpatient antibiotic regimen for treatment of febrile neutropenia in pediatric oncology patients.
Copyright 2003 Wiley-Liss, Inc.
Metronidazole is effective for the treatment of acute pouchitis after ileal pouch-anal anastomosis, but it has not been directly compared with other antibiotics. This randomized clinical trial was designed to compare the effectiveness and side effects of ciprofloxacin and metronidazole for treating acute pouchitis. Acute pouchitis was defined as a score of 7 or higher on the 18-point Pouchitis Disease Activity Index (PDAI) and symptom duration of 4 weeks or less. Sixteen patients were randomized to a 2-week course of ciprofloxacin 1,000 mg/d (n = 7) or metronidazole 20 mg/kg/d (n = 9). Clinical symptoms, endoscopic findings, and histologic features were assessed before and after therapy. Both ciprofloxacin and metronidazole produced a significant reduction in the total PDAI score as well as in the symptom, endoscopy, and histology subscores. Ciprofloxacin lowered the PDAI score from 10.1+/-2.3 to 3.3+/-1.7 (p = 0.0001), whereas metronidazole reduced the PDAI score from 9.7+/-2.3 to 5.8+/-1.7 (p = 0.0002). There was a significantly greater reduction in the ciprofloxacin group than in the metronidazole group in terms of the total PDAI (6.9+/-1.2 versus 3.8+/-1.7; p = 0.002), symptom score (2.4+/-0.9 versus 1.3+/-0.9; p = 0.03), and endoscopic score (3.6+/-1.3 versus 1.9+/-1.5; p = 0.03). None of patients in the ciprofloxacin group experienced adverse effects, whereas three patients in the metronidazole group (33%) developed vomiting, dysgeusia, or transient peripheral neuropathy. Both ciprofloxacin and metronidazole are effective in treating acute pouchitis with significant reduction of the PDAI scores. Ciprofloxacin produces a greater reduction in the PDAI and a greater improvement in symptom and endoscopy scores, and is better tolerated than metronidazole. Ciprofloxacin should be considered as one of the first-line therapies for acute pouchitis.
Topoisomerase IV is the primary cellular target for most quinolones in Gram-positive bacteria; however, its interaction with these agents is poorly understood. Therefore, the effects of four clinically relevant antibacterial quinolones (ciprofloxacin, and three new generation quinolones: trovafloxacin, levofloxacin, and sparfloxacin) on the DNA cleavage/religation reaction of Staphylococcus aureus topoisomerase IV were characterized. These quinolones stimulated enzyme-mediated DNA scission to a similar extent, but their potencies varied significantly. Drug order in the absence of ATP was trovafloxacin > ciprofloxacin > levofloxacin > sparfloxacin. Potency was enhanced by ATP, but to a different extent for each drug. Under all conditions examined, trovafloxacin was the most potent quinolone and sparfloxacin was the least. The enhanced potency of trovafloxacin correlated with several properties. Trovafloxacin induced topoisomerase IV-mediated DNA scission more rapidly than other quinolones and generated more cleavage at some sites. The most striking correlation, however, was between quinolone potency and inhibition of enzyme-mediated DNA religation: the greater the potency, the stronger the inhibition. Dose-response experiments with two topoisomerase IV mutants that confer clinical resistance to quinolones (GrlA(Ser80Phe) and GrlA(Glu84Lys)) indicate that resistance is caused by a decrease in both drug affinity and efficacy. Trovafloxacin is more active against these enzymes than ciprofloxacin because it partially overcomes the effect on affinity. Finally, comparative studies on DNA cleavage and decatenation suggest that the antibacterial properties of trovafloxacin result from increased S. aureus topoisomerase IV-mediated DNA cleavage rather than inhibition of enzyme catalysis.
Quinolones are the most active oral antibacterials in clinical use and act by increasing DNA cleavage mediated by prokaryotic type II topoisomerases. Although topoisomerase IV appears to be the primary cytotoxic target for most quinolones in Gram-positive bacteria, interactions between the enzyme and these drugs are poorly understood. Therefore, the effects of ciprofloxacin on the DNA cleavage and religation reactions of Staphylococcus aureus topoisomerase IV were characterized. Ciprofloxacin doubled DNA scission at 150 nM drug and increased cleavage approximately 9-fold at 5 microM. Furthermore, it dramatically inhibited rates of DNA religation mediated by S. aureus topoisomerase IV. This inhibition of religation is in marked contrast to the effects of antineoplastic quinolones on eukaryotic topoisomerase II, and suggests that the mechanistic basis for quinolone action against type II topoisomerases has not been maintained across evolutionary boundaries. The apparent change in quinolone mechanism was not caused by an overt difference in the drug interaction domain on topoisomerase IV. Therefore, we propose that the mechanistic basis for quinolone action is regulated by subtle changes in drug orientation within the enzyme.drug.DNA ternary complex rather than gross differences in the site of drug binding.