The fluoroquinolones: How long will their utility last?

Novel Fluoroquinolones with Possible Antibacterial Activity in Gram-Negative Resistant Pathogens: In Silico Drug Discovery

Antibiotic resistance is a global threat to public health, and the search for new antibacterial therapies is a current research priority. The aim of this in silico study was to test nine new fluoroquinolones previously designed with potential leishmanicidal activity against Campylobacter jejuni, Escherichia coli, Neisseria gonorrhoeae, Pseudomonas aeruginosa, and Salmonella typhi, all of which are considered by the World Health Organization to resistant pathogens of global concern, through molecular docking and molecular dynamics (MD) simulations using wild-type (WT) and mutant-type (MT) DNA gyrases as biological targets. Our results showed that compound 9FQ had the best binding energy with the active site of E. coli in both molecular docking and molecular dynamics simulations. Compound 9FQ interacted with residues of quinolone resistance-determining region (QRDR) in GyrA and GyrB chains, which are important to enzyme activity and through which it could block DNA replication. In addition to compound 9FQ, compound 1FQ also showed a good affinity for DNA gyrase. Thus, these newly designed molecules could have antibacterial activity against Gram-negative microorganisms. These findings represent a promising starting point for further investigation through in vitro assays, which can validate the hypothesis and potentially facilitate the development of novel antibiotic drugs.

Prevalence of coagulase-positive methicillin-resistant Staphylococcus aureus and Staphylococcus pseudintermedius in dogs in Bangladesh

Background

The emergence of methicillin‐resistant Staphylococcus aureus (MRSA) and methicillin‐resistant Staphylococcus pseudintermedius (MRSP) have a significant health impact on people with direct or supportive occupations in veterinary medicine including veterinarians, animal handlers, laboratory personnel and pet owners.

Objectives

This cross‐sectional survey was conducted to determine the prevalence of and risk factors for S. aureus, S. pseudintermedius, MRSA and MRSP in dogs in Bangladesh.

Methods

A total of 358 swab samples were collected from different body sites of 150 dogs attending a university teaching veterinary hospital between January and June 2018. Standard bacteriological procedures were followed to isolate Staphylococcus, and identification was confirmed to the species level by PCR to detect the nuc gene. MRSA and MRSP were confirmed by the presence of the mecA gene.

Results

The prevalence of coagulase‐positive S. aureus and S. pseudintermedius in dogs were 16% and 45.3%, respectively. S. aureus and S. pseudintermedius isolates displayed the highest resistance against nalidixic acid (95.2% and 91%, respectively) and erythromycin (89.3% and 84.7%, respectively). Notably, all the staphylococcal isolates showed resistance to ≥3 antimicrobial classes. The prevalence of MRSA and MRSP in dogs was 8.7% and 6%, respectively. Multivariable logistic regression analysis identified the following variables as risk factors for MRSA colonisation in dogs: dogs with dermatitis (odds ratio [OR], 12.24, 95% CI: 3.12–57.33; p < 0.001) and history of antibiotic use (OR 8.73, 95% CI: 2.23–43.10; p < 0.001). Presence of otitis (OR 14.22; 95% CI: 1.64–103.58; p = 0.008) and oral lesions (OR 9.48, 95% CI: 1.14–64.82; p = 0.002) were identified as the significant risk factors for the carriage of MRSP.

Conclusions

The circulation of multidrug‐resistant S. aureus and S. pseudintermedius is a serious concern to dogs and humans. To our knowledge, this is the first report of S. pseudintermedius and MRSP affecting dogs in Bangladesh.

Inclusion of surgical antibiotic regimens in pediatric urology publications: A systematic review

BACKGROUND

Perioperative antibiotics prevent infections after surgery. Guidelines for antibiotic use allow the surgeon to balance the risks of adverse events and drug resistance with the benefit of reduced infection rates. However, due to a lack of evidence-based guidelines within pediatric urology, antibiotic practices vary widely. We performed a systematic literature review to investigate when and how authors report their antibiotic usage and infectious outcomes. Our aim was to analyze the available data on perioperative antibiotics and infection rates within pediatric urology.

METHODS

This systematic review was conducted in line with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. A search strategy was devised to identify reports of pediatric urology surgery and use of antibiotics or infectious outcomes. Embase and Medline were queried with no year restrictions with subject heading terms to identify publications on common pediatric urology surgeries. The procedures studied were hypospadias repair, pyeloplasty, orchidopexy, ureteral reimplant, and circumcision. Two independent reviewers screened all titles and abstracts, followed by relevant full texts, for eligibility. Articles were included if the procedure was performed on the majority of study patients, the procedure was performed by urologic surgeons, and the population studied was a pediatric population defined as 0-18 years of age. Case reports, meta-analyses, and editorials were excluded. Data was extracted by one independent reviewer into a preformatted database. Collected data included journal type, date of publication, patient demographics, preoperative and postoperative antibiotic details including regimens, and infection outcomes. The primary outcome was reporting of antibiotic use preoperatively or postoperatively. Secondary outcomes included: reporting of infection, antibiotic class and dosage. Since all studies were diverse, only qualitative analysis was conducted.

RESULTS

We identified 1483 publications with 297 meeting inclusion criteria. Of these, 9% reported their use of preoperative antibiotics, and 34% reported their use of postoperative antibiotics. Only 6% of studies reported the specific antibiotic class, 15% reported duration, and 1% reported dosage and frequency. Infection outcomes were reported in 58% of studies. Only 57% of studies that reported on infection outcomes described their antibiotics practices.

CONCLUSIONS

Surgical antibiotic regimens and infection outcomes are infrequently included in pediatric urology studies, limiting the data available for development of evidence-based guidelines. Routine incorporation of antibiotic regimens, infection outcomes and adverse events in the pediatric urology literature will increase our ability to identify indications for antibiotics. Reporting of perioperative antibiotic outcomes in pediatric urology procedures will allow the eventual development of strong evidence-based guidelines.

Influences of tolfenamic acid and flunixin meglumine on the disposition kinetics of levofloxacin in sheep

The pharmacokinetics of levofloxacin (4 mg/kg), administered both alone and in combination with tolfenamic acid (2 mg/kg) and flunixin meglumine (2.2 mg/kg), was established after intravenous administration in sheep. Plasma levofloxacin concentrations were assayed by high-performance liquid chromatography and analysed according to the two-compartment open model. Following the administration of levofloxacin alone, the mean distribution half-life, elimination half-life, total clearance, volume of distribution at steady state and area under the plasma concentration-time curve were 0.20 h, 1.82 h, 0.39 L/h/kg, 0.96 L/kg and 10.40 h × µg/mL, respectively. Tolfenamic acid and flunixin meglumine caused a slow elimination and increased plasma concentrations of levofloxacin in combination administration. Levofloxacin, with an alteration in the dosage regimen, can be used effectively with tolfenamic acid and flunixin meglumine for the therapy of infections and inflammatory conditions in sheep.

Antimicrobial agents for preventing urinary tract infections in adults undergoing cystoscopy

BACKGROUND

Cystoscopy is commonly performed for diagnostic purposes to inspect the interior lining of the bladder. One disadvantage of cystoscopy is the risk of symptomatic urinary tract infection (UTI) due to pre-existing colonization or by introduction of bacteria at the time of the procedure. However, the incidence of symptomatic UTI following cystoscopy is low. Currently, there is no consensus on whether antimicrobial agents should be used to prevent symptomatic UTI for cystoscopy.

OBJECTIVES

To assess the effects of antimicrobial agents compared with placebo or no treatment for prevention of UTI in adults undergoing cystoscopy.

SEARCH METHODS

We comprehensively searched electronic databases of the Cochrane Library, PubMed, Embase, LILACS, and CINAHL. We searched the WHO ICTRP and ClinicalTrials.gov for ongoing trials. We used no language or date restrictions in the electronic searches. We searched the reference lists of identified articles and contacted authors for related information. The last search of the electronic databases was 4 February 2019.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) or quasi-RCTs that compared any prophylactic antibiotic versus placebo, no treatment, or other non-antibiotic prophylaxis in adults undergoing cystoscopy. There was no restriction on the dose, frequency, formulation, duration, or mode of administration of the antibiotics.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Our primary outcomes were systemic UTI, symptomatic UTI (composite of systemic and/or localized UTI), and serious adverse events. Secondary outcomes were minor adverse events, localized UTI, asymptomatic bacteriuria, and bacterial resistance. We assessed the quality of evidence using GRADE.

MAIN RESULTS

We included 20 RCTs and two quasi-RCTs with 7711 participants, all of which compared antibiotic prophylaxis with placebo or no treatment control. We found no studies comparing antibiotic prophylaxis with non-antibiotic prophylaxis.Primary outcomesSystemic UTI: antibiotic prophylaxis may have little or no effect on the risk of systemic UTI compared with placebo or no treatment (risk ratio (RR) 1.12, 95% confidence interval (CI) 0.38 to 3.32; 5 RCTs; 504 participants; low-quality evidence); this corresponds to two more people (95% CI 12 fewer to 46 more) per 1000 people developing a systemic UTI. We downgraded the quality of the evidence for study limitations and imprecision.Symptomatic UTI: antibiotic prophylaxis may reduce the risk of symptomatic UTI (RR 0.49, 95% CI 0.28 to 0.86; 11 RCTs; 5441 participants; low-quality evidence); this corresponds to 30 fewer people (95% CI 42 fewer to 8 fewer) per 1000 people developing a symptomatic UTI when provided with antibiotic prophylaxis. We downgraded the quality of the evidence for study limitations and potential publication bias.Serious adverse events: the studies reported no serious adverse events in either the intervention group or control group and no effect size could be calculated. Antibiotic prophylaxis may have little or no effect on serious adverse events (4 RCTs, 630 participants; very low-quality evidence), but we are very uncertain of this finding. We downgraded the quality of the evidence for study limitations and very serious imprecision.Secondary outcomesMinor adverse events: prophylactic antibiotics may have little or no effect on minor adverse events when compared with placebo or no treatment (RR 2.82, 95% CI 0.54 to 14.80; 4 RCTs; 630 participants; low-quality evidence). We downgraded the quality of the evidence for study limitations and imprecision.Localized UTI: prophylactic antibiotics may have little or no effect on the risk of localized UTI (RR 1.0, 95% CI 0.06 to 15.77; 1 RCT; 200 participants; very low-quality evidence), but we were very uncertain of this finding. We downgraded the quality of the evidence for study limitations and very serious imprecision.Bacterial resistance: prophylactic antibiotics may increase bacterial resistance (RR 1.73, 95% CI 1.04 to 2.87; 38 participants; 2 RCTs; very low-quality evidence), but we were uncertain of this finding. We downgraded the quality of the evidence for study limitations, indirectness, and imprecision.We were able to perform few secondary analyses; these did not suggest any subgroup effects.

AUTHORS' CONCLUSIONS

Antibiotic prophylaxis may reduce the risk of symptomatic UTI but not systemic UTIs. Serious and minor adverse events may not be increased with the use of antibiotic prophylaxis. The findings are informed by low- and very low-quality evidence ratings for all outcomes.

Post-surgical infections and perioperative antibiotics usage in pediatric genitourinary procedures

BACKGROUND

Post-surgical infections (PSIs) are a source of preventable perioperative morbidity. No guidelines exist for the use of perioperative antibiotics in pediatric urologic procedures.

OBJECTIVE

This study reports the rate of PSIs in non-endoscopic pediatric genitourinary procedures at our institution. Secondary aims evaluate the association of PSI with other perioperative variables, including wound class (WC) and perioperative antibiotic administration.

STUDY DESIGN

Data from consecutive non-endoscopic pediatric urologic procedures performed between August 2011 and April 2014 were examined retrospectively. The primary outcome was the rate of PSIs. PSIs were classified as superficial skin (SS) and deep/organ site (D/OS) according to Centers for Disease Control and Prevention guidelines, and urinary tract infection (UTI). PSIs were further stratified by WC1 and WC2 and perioperative antibiotic usage. A relative risk and chi-square analysis compared PSI rates between WC1 and WC2 procedures.

RESULTS

A total of 1185 unique patients with 1384 surgical sites were reviewed; 1192 surgical sites had follow-up for inclusion into the study. Ten total PSIs were identified, for an overall infection rate of 0.83%. Of these, six were SS, one was D/OS, and three were UTIs. The PSI rate for WC1 (885 sites) and WC2 (307 sites) procedures was 0.34% and 2.28%, respectively, p < 0.01. Relative risk of infection in WC2 procedures was 6.7 (CI 1.75-25.85, p = 0.0055). The rate of infections in WC1 procedures was similar between those receiving and not receiving perioperative antibiotics (0.35% vs. 0.33%). All WC2 procedures received antibiotics.

DISCUSSION

Post-surgical infections are associated with significant perioperative morbidity. In some studies, PSI can double hospital costs, and contribute to hospital length of stay, admission to intensive care units, and impact patient mortality. Our study demonstrates that the rate of PSI in WC1 operations is low, irrespective of whether the patient received perioperative antibiotics (0.35%) or no antibiotics (0.33%). WC2 operations were the larger source of morbidity with an infection rate of 2.28% and a 6.7 fold higher increase in relative risk.

CONCLUSIONS

WC1 procedures have a rate of infection around 0.3%, which is independent of the use of perioperative antibiotics. WC2 procedures have a higher rate of infection, with a relative risk of 6.7 for the development of PSI, and should be the target of guidelines for periprocedural prophylaxis.

Antibiotic prophylaxis for urinary tract infections after removal of urinary catheter: meta-analysis

OBJECTIVE

To determine whether antibiotic prophylaxis at the time of removal of a urinary catheter reduces the risk of subsequent symptomatic urinary tract infection.:

DESIGN

Systematic review and meta-analysis of studies published before November 2012 identified through PubMed, Embase, Scopus, and the Cochrane Library; conference abstracts for 2006-12 were also reviewed.

INCLUSION CRITERIA

Studies were included if they examined antibiotic prophylaxis administered to prevent symptomatic urinary tract infection after removal of a short term (≤ 14 days) urinary catheter.

RESULTS

Seven controlled studies had symptomatic urinary tract infection after catheter removal as an endpoint; six were randomized controlled trials (five published; one in abstract form) and one was a non-randomized controlled intervention study. Five of these seven studies were in surgical patients. Studies were heterogeneous in the type and duration of antimicrobial prophylaxis and the period of observation. Overall, antibiotic prophylaxis was associated with benefit to the patient, with an absolute reduction in risk of urinary tract infection of 5.8% between intervention and control groups. The risk ratio was 0.45 (95% confidence interval 0.28 to 0.72). The number needed to treat to prevent one urinary tract infection was 17 (12 to 30).

CONCLUSIONS

Patients admitted to hospital who undergo short term urinary catheterization might benefit from antimicrobial prophylaxis when the catheter is removed as they experience fewer subsequent urinary tract infections. Potential disadvantages of more widespread antimicrobial prophylaxis (side effects and cost of antibiotics, development of antimicrobial resistance) might be mitigated by the identification of which patients are most likely to benefit from this approach.

Plasmid-mediated quinolone resistance--current knowledge and future perspectives

Quinolones are a group of antimicrobial agents that were serendipitously discovered as byproducts of the synthesis of chloroquine. Chemical modifications, such as the addition of fluorine or piperazine, resulted in the synthesis of third- and fourth-generation fluoroquinolones, with broad-spectrum antimicrobial actions against aerobic or anaerobic, Gram-positive or Gram-negative bacteria. The efficacy and consequent widespread use of quinolones and fluoroquinolones has led to a steady global increase in resistance, mediated via gene mutations, alterations in efflux or cell membranes and plasmid-conferred resistance. The first plasmid-mediated quinolone resistance gene, qnrA1, was detected in 1998. Since then, many other genes have been identified and the underlying mechanisms of resistance have been elucidated. This review provides an overview of quinolone resistance, with particular emphasis on plasmid-mediated resistance.

A 5-kg time-resolved luminescence photometer with multiple excitation sources

A luminescence photometer was developed based on lanthanide-sensitized luminescence to detect environmental pollutants and residues in foods including, in particular, two classes of antibiotics: tetracyclines and fluoroquinolones. Multiple excitation sources, a xenon flashlamp and ultraviolet light-emitting diodes (UV LEDs), were used to their advantages. A photomultiplier tube module, gated to reject time-domain interferences, was used as a photodetector. Using danofloxacin as a model analyte, luminescence signal was linear in more than three decades (0.5-2000 ng/mL) with R(2) > 0.998 in each decade. This photometer achieved a limit of detection of 2.0 ng/mL with 1.3% average relative standard deviation. It is field deployable at 4.6 kg and 15 W power consumption.

The management of acute uncomplicated cystitis in adult women by family physicians in Canada

INTRODUCTION

There are few Canadian studies that have assessed prescribing patterns and antibiotic preferences of physicians for acute uncomplicated cystitis. A cross-Canada study of adult women with symptoms of acute cystitis seen by primary care physicians was conducted to determine current management practices and first-line antibiotic choices.

METHODS

A random sample of 2000 members of The College of Family Physicians of Canada were contacted in April 2002, and were asked to assess two women presenting with new urinary tract symptoms. Physicians completed a standardized checklist of symptoms and signs, indicated their diagnosis and antibiotics prescribed. A urine sample for culture was obtained.

RESULTS

Of the 418 responding physicians, 246 (58.6%) completed the study and assessed 446 women between April 2002 and March 2003. Most women (412 of 420, for whom clinical information about antibiotic prescriptions was available) reported either frequency, urgency or painful urination. Physicians would have usually ordered a urine culture for 77.0% of the women (95% CI 72.7 to 80.8) and prescribed an antibiotic for 86.9% of the women (95% CI 83.3 to 90.0). The urine culture was negative for 32.8% of these prescriptions. The most commonly prescribed antibiotic was trimethoprim/sulfamethoxazole (40.8%; 95% CI 35.7 to 46.1), followed by fluoroquinolones (27.4%; 95% CI 22.9 to 32.3) and nitrofurantoin (26.6%; 95% CI 22.1 to 31.4).

CONCLUSION

Empirical antibiotic prescribing is standard practice in the community, but is associated with high levels of unnecessary antibiotic use. While trimethoprim/sulfamethoxazole is the first-line empirical antibiotic choice, fluoroquinolone antibiotics have become the second most commonly prescribed empirical antibiotic for acute cystitis. The effect of current prescribing patterns on community levels of quinolone-resistant Escherichia coli may need to be monitored.

Community-acquired antibiotic resistance in urinary isolates from adult women in Canada

BACKGROUND

There are currently limited data regarding the prevalence of antimicrobial-resistant organisms causing community-acquired urinary tract infections among adult women in Canada. Trimethoprim-sulfamethoxazole (TMP-SMX) is the recommended first-line empirical antibiotic treatment, unless resistance of Escherichia coli to TMP-SMX exceeds 20%.

OBJECTIVE

To assess current levels of TMP-SMX-resistant E coli in community-acquired cases of urinary tract infection in adult women.

METHOD

Assessment of urine culture reports obtained from 21 laboratories across Canada, submitted by family physicians for women aged 16 years and older.

RESULTS

In 2199 adult women with a positive urine culture, 1079 (49.1%) of pathogens isolated were resistant to at least one antibiotic and 660 (30.0%) were multidrug-resistant (resistant to two or more antibiotics). TMP-SMX resistance was seen in 245 of 1613 (15.2%) E coli isolates (95% CI 13.5 to 17.0). This proportion was higher in women 50 years of age and older (155 of 863 isolates [18.0%]; P=0.001), in British Columbia (70 of 342 isolates [20.5%]) and in Ontario (62 of 370 isolates [16.8%]) when compared with eastern provinces (65 of 572 isolates [11.4%]; P=0.001). Fluoroquinolone-resistant E coli occurred in 107 of 1557 (6.9%) isolates (95% CI 5.7 to 8.2), with the highest level found in British Columbia (54 of 341 isolates [15.8%]; P=0.001).

CONCLUSION

TMP-SMX continues to be appropriate as first-line empirical treatment of acute cystitis in adult women in Canada, as resistance remains below 20%. However, TMP-SMX resistance is higher in older women and in some provinces. The level of fluoroquinolone-resistant E coli is highest in British Columbia.

Surgical antibiotic practices among pediatric urologists in the United States

PURPOSE

We hypothesized that there are practice variations in the use of surgical antibiotics by pediatric urologists in the United States.

MATERIALS AND METHODS

A 31-question online survey was distributed to members of the Society of Pediatric Urology. The questionnaire examined physician preferences for surgical antibiotic use, including indications, antibiotic selection, timing of administration, and duration.

RESULTS

189 pediatric urologists responded to the survey. >85% of responders give antibiotics before open pyeloplasty, after hypospadias repair (when a urethral catheter is left in place), or perioperative or postoperative antibiotics for open neoureterocystostomy or bladder reconstructive surgery. >90% of responders do not give postoperative antibiotics to children who have undergone circumcisions, simple chordee repairs, herniorrhapies, or hydrocelectomies. For all other open, laparoscopic, and endoscopic operations, use of antibiotics varied significantly. Diverse opinions exist regarding antibiotic use, including the importance of costs, potential adverse reactions, reduction in infection risk, and antibiotic resistance. There are major differences in gentamicin dosing and timing of administration of perioperative antibiotics.

CONCLUSIONS

Perioperative and postoperative antibiotics are widely used by pediatric urologists. However, there is significant practice variation in surgical antibiotic administration with regards to most areas of pediatric urology, in particular laparoscopic, endoscopic and hypospadias surgery.

[Regional audit on fluoroquinolones usage in the hospital and the community: are these antibiotics over-used?]

AIM OF THE STUDY

The ecological impact of an over-use or a mis-use of fluoroquinolones (FQs) appears of great importance according to published data. With the objective to set up a regional antibiotic stewardship program, we conducted a regional audit on FQs usage.

MATERIAL AND METHODS

[corrected] Ninety general practionners and 15 health care facilities participated to this prospective study. Overall, 511 prescriptions were evaluated (276 from hospital physicians and 235 [46%] from general practionners). The compliance of FQs prescription with national recommendations and with a regional referential was assessed. This regional referential was established in order to preserve FQs.

RESULTS

Only 14,3% of the prescriptions complied with the regional referential, even if the choice of FQs were in accordance with national recommendations in 56,8% of the prescriptions. Urinary tract infections (mostly non-complicated) were the most common indication for FQs prescription.

CONCLUSION

Analysis of FQs prescriptions shows that there is a significant potential for FQs preservation in Franche-Comté.

Fluoroquinolone prescriptions in a teaching hospital: A prospective audit

The aim of this study was to identify prospectively the prevalence of unnecessary or inappropriate fluoroquinolone prescriptions in our teaching hospital and to identify the contributing factors. 55% of the 110 prescriptions evaluated were unnecessary or inappropriate. Ward and combination therapies were significantly associated with misuse.

Disposition kinetics and dosage regimen of levofloxacin on concomitant administration with paracetamol in crossbred calves

The disposition kinetics of levofloxacin was investigated in six male crossbred calves following single intravenous administration, at a dose of 4 mg/kg body weight, into the jugular vein subsequent to a single intramuscular injection of paracetamol (50 mg/kg). At 1 min after the injection of levofloxacin, the concentration of levofloxacin in plasma was 17.2 ± 0.36 µg/ml, which rapidly declined to 6.39 ± 0.16 µg/ml at 10 min. The drug level above the MIC₉₀ in plasma, was detected for up to 10 h. Levofloxacin was rapidly distributed from blood to the tissue compartment as evidenced by the high values of the distribution coefficient, α (17.3 ± 1.65 /h) and the ratio of K₁₂/K₂₁ (1.83 ± 0.12). The values of AUC and Vd_area were 12.7 ± 0.12 µg.h/ml and 0.63 ± 0.01 l/kg. The high ratio of the AUC/MIC (126.9 ± 1.18) obtained in this study indicated the excellent antibacterial activity of levofloxacin in calves. The elimination half-life, MRT and total body clearance were 1.38 ± 0.01 h, 1.88 ± 0.01 h and 0.32 ± 0.003 l/kg/h, respectively. Based on the pharmacokinetic parameters, an appropriate intravenous dosage regimen for levofloxacin would be 5 mg/kg repeated at 24 h intervals when prescribed with paracetamol in calves.

Disposition kinetics and urinary excretion of levofloxacin on concomitant administration with meloxicam in cross-bred calves

The disposition kinetics and urinary excretion study of levofloxacin was conducted in 5 male cross-bred calves following its single intravenous administration (4mgkg(-1)) concurrently with meloxicam (0.5mgkg(-1)). Levofloxacin was estimated by microbiological assay. The drug levels above MIC(90) in plasma, were detected up to 10h. Disposition kinetic parameters were calculated by two-compartment open model. Rapid distribution of levofloxacin was evidenced by a small distribution half-life (0.13±0.01h) and high K(12)/K(21) ratio (2.21±0.15). High ratio of AUC/MIC (90.2±3.41) indicated good antibacterial activity of levofloxacin. The AUC, Vd(area), elimination half-life, MRT and total body clearance were 9.02±0.34μgml(-1)h, 1.38±0.05lkg(-)1, 2.16±0.08h, 2.58±0.11h and 0.45±0.02lkg(-1)h(-1), respectively. About 38.4% of the administered dose of levofloxacin was excreted in urine within 24h. A suitable intravenous dosage regimen for levofloxacin would be 1.8mgkg(-1) repeated at 8h intervals when prescribed with meloxicam in calves.

Nonclinical pharmacodynamics, pharmacokinetics, and safety of BOL-303224-A, a novel fluoroquinolone antimicrobial agent for topical ophthalmic use

BOL-303224-A is a novel fluoroquinolone that has never been used systemically and that possesses structural modifications intended to improve its potency compared to other fluoroquinolones. This investigation was conducted to evaluate the nonclinical pharmacokinetics, safety, and pharmacodynamics of BOL-303224-A. BOL-303224-A displayed activity in in vitro antimicrobial efficacy studies and also demonstrated efficacy in an in vivo murine infection model. BOL-303224-A demonstrated excellent ocular pharmacokinetics in rabbits, with ocular mean residence times >7 h, and conjunctival concentrations in excess of the MIC(90) for nonresistant ophthalmic isolates for >12 h following a single dose. Pharmacokinetic modeling from these data indicated that BOL-303224-A has the potential to demonstrate efficacy against ophthalmologic pathogens with a TID dosing regimen. BOL-303224-A also demonstrated reasonably low plasma protein binding in rat and human models, as well as good metabolic stability across species. In studies designed to explore the nonclinical safety profile of BOL-303224-A, the compound showed excellent topical ocular tolerance in rabbits and dogs, as well as a favorable genotoxicity and phototoxicity profile. In summary, BOL-303224-A exhibits an encouraging nonclinical pharmacodynamic, pharmacokinetic, and safety profile that supports clinical development as a topical agent for the potential treatment of ophthalmic infections.

The synthesis and biological evaluation of novel series of nitrile-containing fluoroquinolones as antibacterial agents

Several novel series of nitrile-containing fluoroquinolones with weakly basic amines are reported which have reduced potential for hERG (human ether-a-go-go gene) channel inhibition as measured by the dofetilide assay. The new fluoroquinolones are potent against both Gram-positive and fastidious Gram-negative strains, including Methicillin resistant Staphylococcus aureus and fluoroquinolone-resistant Streptococcus pneumoniae. Several analogs also showed low potential for human genotoxicity as measured by the clonogenicity test. Compounds 22 and 37 (designated PF-00951966 and PF-02298732, respectively), which had good in vitro activity and in vitro safety profiles, also showed good pharmacokinetic properties in rats.

Plasma Concentrations, Pharmacokinetics and Urinary Excretion of Gatifloxacin after Single Intravenous Injection in Buffalo Calves

The pharmacokinetics and urinary excretion of gatifloxacin were investigated after a single intravenous injection of 4 mg/kg body weight in buffalo calves. The therapeutic plasma drug concentration was maintained for up to 12 h. Gatifloxacin rapidly distributed from blood to tissue compartments, which was evident from the high values of the distribution rate constant, alpha1 (11.1 +/- 1.06 h(-1)) and the rate constant of transfer of drug from central to peripheral compartment, k12 (6.29 +/- 0.46 h(-1)). The area under the plasma drug concentration-time curve and apparent volume of distribution were 17.1 +/- 0.63 (microg.h)/ml and 3.56 +/- 0.95 L/kg, respectively. The elimination half-life (t (1/2 beta)), total body clearance (ClB) and the ratio of drug present in tissues and plasma (T/P) were 10.4 +/- 2.47 h, 235.1 +/- 8.47 ml/(kg.h) and 10.1 +/- 2.25, respectively. About 19.7% of the administered drug was excreted in urine within 24 h. A satisfactory intravenous dosage regimen for gatifloxacin in buffalo calves would be 5.3 mg/kg at 24 h intervals.

Pharmacokinetics, urinary excretion and dosage regimen of levofloxacin following a single intramuscular administration in cross bred calves

The pharmacokinetics and urinary excretion following single intramuscular administration of levofloxacin at a dose of 4 mg/kg was investigated in seven male cross bred calves. Appreciable plasma concentration of levofloxacin (0.38+/-0.06 microgram/ml) was detected at 1 min after injection and the peak plasma level of 3.07+/-0.08 microgram/ml was observed at 1 h. The drug level above MIC90 in plasma was detected up to 12 h after administration. Rapid absorption of the drug was also evident by the high value of the absorption rate constant (2.14+/-0.24 /h). The overall systemic bioavailability of levofloxacin, after intramuscular administration, was 56.6+/-12.4%. The high value of AUC (7.66+/-0.72 mg.h/ml) reflected the vast area of body covered by drug concentration. Extensive distribution of the drug into various body fluids and tissues was noted by the high value of Vd(area) (1.02+/-0.05 l/kg). The high ratio of AUC/MIC (76.6+/-7.25) obtained in this study indicated excellent clinical and bacteriological efficacy of levofloxacin in calves. The elimination half-life and MRT were 3.67+/-0.4 h and 5.57+/-0.51 h, respectively. The total body clearance (Cl(B)) was 204.9+/-22.6 ml/kg/h. On the basis of the pharmacokinetic parameters, a suitable intramuscular dosage regimen for levofloxacin in calves would be 1.5 mg/kg repeated at 12 h intervals.

Heavy use of prophylactic antibiotics in aquaculture: a growing problem for human and animal health and for the environment

The accelerated growth of finfish aquaculture has resulted in a series of developments detrimental to the environment and human health. The latter is illustrated by the widespread and unrestricted use of prophylactic antibiotics in this industry, especially in developing countries, to forestall bacterial infections resulting from sanitary shortcomings in fish rearing. The use of a wide variety of antibiotics in large amounts, including non-biodegradable antibiotics useful in human medicine, ensures that they remain in the aquatic environment, exerting their selective pressure for long periods of time. This process has resulted in the emergence of antibiotic-resistant bacteria in aquaculture environments, in the increase of antibiotic resistance in fish pathogens, in the transfer of these resistance determinants to bacteria of land animals and to human pathogens, and in alterations of the bacterial flora both in sediments and in the water column. The use of large amounts of antibiotics that have to be mixed with fish food also creates problems for industrial health and increases the opportunities for the presence of residual antibiotics in fish meat and fish products. Thus, it appears that global efforts are needed to promote more judicious use of prophylactic antibiotics in aquaculture as accumulating evidence indicates that unrestricted use is detrimental to fish, terrestrial animals, and human health and the environment.

Investigation of antimicrobial use and the impact of antimicrobial use guidelines in a small animal veterinary teaching hospital: 1995-2004

OBJECTIVE

To evaluate patterns of antimicrobial use and the impact of antimicrobial use guidelines at a small animal veterinary teaching hospital.

DESIGN

Retrospective study.

SAMPLE POPULATION

All antimicrobial prescriptions for dogs and cats admitted to the hospital in 1995 through 2004.

PROCEDURE

Pharmacy records were reviewed, and antimicrobial prescriptions for all dogs and cats admitted during the study period were recorded. Amounts of individual drugs dispensed directly to the intensive care and surgical units were determined. Changes in antimicrobial use during the study period were assessed; changes in antimicrobial use patterns in 2000 through 2004 were evaluated to assess the impact of implementation of antimicrobial use guidelines in 2001.

RESULTS

There was a significant decrease in prescriptions/1,000 admissions during the study period. From 1995 to 2004, the use of first-generation cephalosporins, fluoroquinolones, penicillins, and trimethoprim-sulfonamides decreased, whereas the use of metronidazole increased. The use of first-generation cephalosporins, fluoroquinolones, and penicillins decreased from 2000 to 2004. First-line drugs accounted for 90.7% of prescriptions during the study period. The use of third-line drugs decreased from 2000 to 2004.

CONCLUSIONS AND CLINICAL RELEVANCE

Characterization of antimicrobial use is an important step in defining and evaluating the prudent use of antimicrobials. Whereas the true effect of antimicrobial use guidelines is unclear, these results suggest that the guidelines may have had an effect on antimicrobial prescription patterns in this small animal veterinary teaching hospital. Analysis of objective data regarding antimicrobial use and changes in antimicrobial use patterns over time is important in veterinary practices.

Quinolones in 2005: an update

Quinolones are one of the largest classes of antimicrobial agents used worldwide. This review considers the quinolones that are available currently and used widely in Europe (norfoxacin, ciprofloxacin, ofloxacin, levofloxacin and moxifloxacin) within their historical perspective, while trying to position them in the context of recent and possible future advances based on an understanding of: (1) their chemical structures and how these impact on activity and toxicity; (2) resistance mechanisms (mutations in target genes, efflux pumps); (3) their pharmacodynamic properties (AUC/MIC and Cmax/MIC ratios; mutant prevention concentration and mutant selection window); and (4) epidemiological considerations (risk of emergence of resistance, clonal spread). Their main indications are examined in relation to their advantages and drawbacks. Overall, it is concluded that these important agents should be used in an educated fashion, based on a careful balance between their ease of use and efficacy vs. the risk of emerging resistance and toxicity. However, there is now substantial evidence to support use of the most potent drug at the appropriate dose whenever this is required.