Treatment of canine pyoderma with ibafloxacin and marbofloxacin - fluoroquinolones with different pharmacokinetic profiles

Investigation of In Vitro Susceptibility and Resistance Mechanisms in Skin Pathogens: Perspectives for Fluoroquinolone Therapy in Canine Pyoderma

Fluoroquinolones (FQ) are commonly used in dogs with bacterial skin infections. Their use as first choice, along with the increased incidence of FQ-resistance, represents a risk to animal and public health. Our study determined minimum inhibitory (MIC) and bactericidal (MBC) concentrations of five FQs in Staphylococcus aureus, Staphylococcus pseudintermedius, and Escherichia coli, together with FQ-resistance mechanisms. MICs, efflux pump (EP) overexpression and MBCs were measured in 249 skin infection isolates following CLSI guidelines (CLSI VET01-A4, CLSI M26-A). Chromosomal and plasmid-mediated resistance genes were investigated after DNA extraction and sequencing. FQ-resistance was detected in 10% of methicillin-susceptible (MS), 90% of methicillin-resistant (MR) staphylococci and in 36% of E. coli. Bactericidal effect was observed except in 50% of MRSA/P for ciprofloxacin and in 20% of MRSPs for enrofloxacin. Highest MICs were associated with double mutation in gyrA (Ser83Leu + Asp87Asn), efflux pumps and three PMQR genes in E. coli, and grlA (Ser80Phe + Glu84Lys) in S. aureus. EP overexpression was high among E. coli (96%), low in S. aureus (1%) and absent in S. pseudintermedius. Pradofloxacin and moxifloxacin showed low MICs with bactericidal effect. Since in vitro FQ resistance was associated with MR, FQ use should be prudently guided by susceptibility testing.

Oral Plus Topical Administration of Enrofloxacin-Hydrochloride-Dihydrate for the Treatment of Unresponsive Canine Pyoderma. A Clinical Trial

An outpatient clinical trial on unresponsive deep-bacterial canine pyoderma (UDCP), without a control group, is presented. The chosen treatment was implemented with a new crystal-solvate of enrofloxacin (enrofloxacin HCl-2H2O or enro-C), in a dual scheme, i.e., 10 mg/kg/day PO, plus its topical administration, prepared as 0.5% in an alginate gel, thrice per day. Fifty-five cases that were unsuccessfully treated previously with another antibacterial drug, were selected and then classified as severe or very severe, according to a clinical score tailored for this trial. Aerobic bacteriological cultures of skin lesions and antibacterial sensitivity tests, were performed. Hematological status, liver, and kidney functions were determined before and after treatment. A complete success was obtained in 32 severe and 23 very severe, cases. The main bacterial isolates were: Staphylococcus intermedius (19/99), Staphylococcus pseudintermedius (16/99), Staphylococcus epidermidis (15/99), Staphylococcus pyogenes (14/99), Staphylococcus saprophyticus, Streptococcus sp., and others including Pseudomonas aeruginosa (6/99). The average duration of treatment was 8.03 days ± 2.1 SD and 12.0 ± 2.4 days, for dogs with severe or very severe UDCP, respectively. The adverse effects caused by enro-C were inconsequential and the hematological tests showed no deviations from normality. The use of enro-C administered dually to treat UDCP, is considered safe and highly effective.

Suggested guidelines for using systemic antimicrobials in bacterial skin infections: part 2-- antimicrobial choice, treatment regimens and compliance

Systemic antimicrobials are critically important in veterinary healthcare, and resistance is a major concern. Antimicrobial stewardship will be important in maintaining clinical efficacy by reducing the development and spread of antimicrobial resistance. Bacterial skin infections are one of the most common reasons for using systemic antimicrobials in dogs and cats. Appropriate management of these infections is, therefore, crucial in any policy for responsible antimicrobial use. The goals of therapy are to confirm that an infection is present, identify the causative bacteria, select the most appropriate antimicrobial, ensure that the infection is treated correctly, and to identify and manage any underlying conditions. This is the second of two articles that provide evidence-led guidelines to help practitioners address these issues. Part 1 discussed the use of clinical signs, cytology and culture in diagnosis. This article will cover the rationale for topical and systemic antimicrobial therapy, including choice of first-, second- and third-line drugs, the dose, duration of therapy, compliance and identification of underlying predisposing conditions. In addition, there is guidance on cases of therapeutic failure and environmental hygiene. These guidelines will help veterinarians avoid the development and propagation of antimicrobial-resistant bacterial strains.

The effectiveness of systemic antimicrobial treatment in canine superficial and deep pyoderma: a systematic review

AIM

To identify and evaluate existing evidence for the effectiveness of systemic antimicrobial treatments for naturally occurring superficial and deep canine pyoderma.

METHOD

Electronic searches of PubMed, MEDLINE and CAB Direct were carried out (25 May 2011) without date or language restrictions. Proceedings of ESVD/ECVD, AAVD/ACVD, NAVDF and WCVD annual congresses were searched. Unpublished studies were sought via the Veterinary Dermatology discussion list and Veterinary Information Network.

RESULTS

Seventeen full-length, peer-reviewed controlled trials reporting clinical outcomes of systemic antimicrobial treatment for canine pyoderma were identified. Outcomes specific to superficial or deep pyoderma were reported in nine and five studies, respectively. Five studies reported outcomes only for nondifferentiated pyoderma depth. Heterogeneity of study designs and outcome measures made meta-analysis inappropriate. A good level of evidence was identified supporting the high efficacy of subcutaneously injected cefovecin in superficial pyoderma and for oral amoxicillin-clavulanic acid in deep pyoderma. A fair level of evidence was identified for moderate to high efficacy of oral amoxicillin-clavulanic acid, clindamycin, cefadroxil, trimethoprim-sulphamethoxazole and sulfadimethoxine-ormetoprim in superficial pyoderma and oral pradofloxacin, oral cefadroxil and subcutaneously injected cefovecin in deep pyoderma. Eleven trials reported observations of adverse effects in treated pyoderma cases by intervention group; four dogs were withdrawn owing to the severity of adverse effects.

CONCLUSIONS

There is a need for greater numbers of adequately sized, blinded, randomized controlled trials evaluating systemic antimicrobial interventions for canine pyoderma. Improved differentiation between superficial and deep pyoderma in outcome reporting, outcome measure standardization and association of outcomes with causative bacterial species and their resistance patterns are required.

Antimicrobial susceptibility and mechanism of resistance to fluoroquinolones in Staphylococcus intermedius and Staphylococcus schleiferi

The objective of the present study was to determine the antimicrobial susceptibility of 136 canine isolates of Staphylococcus intermedius and 10 canine isolates of S. schleiferi subspecies coagulans to 16 fluoroquinolones (FQs), and to investigate the mechanisms of resistance in the nonsusceptible isolates. Of the 136 of S. intermedius tested 98.5% were susceptible to all 16 FQs whereas only 40% of the 10 isolates of S. schleiferi subspecies coagulans were susceptible. Two isolates of S. intermedius and six isolates of S. schleiferi, were found to be resistant to 13 out of 16 FQs, while they retained their susceptibility to fourth generation FQs such as gatifloxacin, moxifloxacin and trovafloxacin. Sequencing of the quinolone-resistance determining regions of gyrA and grlA genes showed that in S. intermedius, dichotomous resistance to FQs was associated with the occurrence of one alteration in GyrA-84 and one in GrlA-80, while in S. schleiferi the same pattern of resistance was observed in isolates showing these changes only in gyrA. This study is the first to screen FQs of the second, third and fourth generation for antimicrobial resistance in clinical isolates of S. intermedius and S. schleiferi of canine origin, and to describe mutations in gyrA and grlA associated with FQ resistance in these bacterial species.

Pradofloxacin in the treatment of canine deep pyoderma: a multicentred, blinded, randomized parallel trial

A multicentre, randomized, blinded study compared the efficacy of pradofloxacin with that of a combination of amoxycillin/clavulanic acid in the treatment of deep pyoderma in dogs. Dogs with clinical lesions of deep pyoderma and a positive bacterial culture were included in the study. At each visit, they were evaluated with lesion, pruritus and general condition scores. Dogs were treated either with pradofloxacin at 3 mg kg-1 once daily or with amoxycillin at 10 mg kg-1 and clavulanic acid at 2.5 mg kg-1 twice daily and evaluated weekly for 3 weeks and every 2 weeks thereafter until 2 weeks past clinical remission. Maximal treatment duration was 9 weeks, and maximal evaluation period was 11 weeks. Of the 56 dogs treated with pradofloxacin (group 1), 48 dogs (86%) achieved clinical remission, four dogs improved, four dogs did not respond and a recurrence of clinical signs was not seen in any patient after 11 weeks. Of the 51 dogs treated with amoxycillin/clavulanic acid (group 2), 37 dogs achieved clinical remission (73%), three dogs showed improvement, five dogs showed no response and in six dogs, clinical signs recurred within 2 weeks of cessation of therapy. These results indicate that pradofloxacin is an efficacious therapy comparable to amoxycillin/clavulanic acid for deep bacterial pyoderma in dogs.

Pharmacokinetics of marbofloxacin in blue and gold macaws (Ara ararauna)

OBJECTIVE

To determine the pharmacokinetics of marbofloxacin after single IV and orally administered doses in blue and gold macaws.

ANIMALS

10 healthy blue and gold macaws.

PROCEDURES

In a crossover study, marbofloxacin (2.5 mg/kg) was administered orally (via crop gavage) to 5 birds and IV to 5 birds. Blood samples were obtained at 0, 0.5, 1, 3, 6, 12, 24, 48, 72, and 96 hours after marbofloxacin administration. After a 4-week washout period, the study was repeated, with the first 5 birds receiving the dose IV and the second 5 birds receiving the dose orally. Serum marbofloxacin concentrations were quantitated by use of a validated liquid chromatography-mass spectrometry assay.

RESULTS

After oral administration, mean +/- SD area under the curve was 7.94 +/- 2.08 microg.h/mL, maximum plasma concentration was 1.08 +/- 0.316 microg/mL, and bioavailability was 90.0 +/- 31%. After IV administration of marbofloxacin, the apparent volume of distribution was 1.3 +/- 0.32 L/kg, plasma clearance was 0.29 +/- 0.078 L/h/kg, area under the curve was 9.41 +/- 2.84 microg.h/mL, and the harmonic mean terminal half-life was 4.3 hours.

CONCLUSIONS AND CLINICAL RELEVANCE

Single IV and orally administered doses of marbofloxacin were well tolerated by blue and gold macaws. The orally administered dose was well absorbed. Administration of marbofloxacin at a dosage of 2.5 mg/kg, PO, every 24 hours may be appropriate to control bacterial infections susceptible to marbofloxacin in this species.

Pharmacokinetics of ibafloxacin in healthy cats

The pharmacokinetics of ibafloxacin following single and repeated administration of an oral gel formulation and the effect of food intake were investigated in cats. Ibafloxacin is a chiral fluoroquinolone available for clinical use as a racemic mixture of the R- and S-enantiomers. Plasma concentrations of ibafloxacin and its metabolites were determined using microbiological, LC-MS-MS and enantioselective capillary zone electrophoresis assays. Ibafloxacin was absorbed rapidly [time of maximum concentration (tmax) 2-3 h], reaching a mean maximum concentration (Cmax) of approximately 2.1 and 1.6 microg/mL for R- and S-ibafloxacin, respectively, following a single oral administration of the racemate at 15 mg/kg. Once absorbed, ibafloxacin was metabolized to 7-hydroxy-ibafloxacin and mainly to 8-hydroxy-ibafloxacin. Following repeated oral administration, significant increases in Cmax and AUC of ibafloxacin and its less active metabolites (racemic or enantiomers) were observed between the first and the tenth day of treatment. This twofold exposure increase in concentrations of ibafloxacin and its metabolites may contribute additionally to the efficacy of this drug in the treatment of feline bacterial infections. Single and repeated doses of ibafloxacin were well tolerated by cats. Food promoted the absorption of ibafloxacin, doubling Cmax and increasing AUC and slightly delaying tmax. High concentrations of the metabolites, mainly 8-hydroxy- and 7-hydroxy-ibafloxacin were excreted in urine, either unchanged or as glucurono-conjugates.