Impact of environment on transmission of antibiotic-resistant superbugs in humans and strategies to lower dissemination of antibiotic resistance

Antibiotics are the most efficient type of therapy developed in the twentieth century. From the early 1960s to the present, the rate of discovery of new and therapeutically useful classes of antibiotics has significantly decreased. As a result of antibiotic use, novel strains emerge that limit the efficiency of therapies in patients, resulting in serious consequences such as morbidity or mortality, as well as clinical difficulties. Antibiotic resistance has created major concern and has a greater impact on global health. Horizontal and vertical gene transfers are two mechanisms involved in the spread of antibiotic resistance genes (ARGs) through environmental sources such as wastewater treatment plants, agriculture, soil, manure, and hospital-associated area discharges. Mobile genetic elements have an important part in microbe selection pressure and in spreading their genes into new microbial communities; additionally, it establishes a loop between the environment, animals, and humans. This review contains antibiotics and their resistance mechanisms, diffusion of ARGs, prevention of ARG transmission, tactics involved in microbiome identification, and therapies that aid to minimize infection, which are explored further below. The emergence of ARGs and antibiotic-resistant bacteria (ARB) is an unavoidable threat to global health. The discovery of novel antimicrobial agents derived from natural products shifts the focus from chemical modification of existing antibiotic chemical composition. In the future, metagenomic research could aid in the identification of antimicrobial resistance genes in the environment. Novel therapeutics may reduce infection and the transmission of ARGs.

Phytochemical Composition and Antibacterial Activity of Barleria albostellata C.B. Clarke Leaf and Stem Extracts

Barleria albostellata (Acanthaceae) is a shrub located in South Africa and is relatively understudied. However, plants within this genus are well known for their medicinal and ethnopharmacological properties. This study aimed to characterise the phytochemical compounds and antibacterial efficacies of B. albostellata. Phytochemical analysis, fluorescence microscopy and gas chromatography-mass spectrometry (GC-MS) analysis were performed to determine the composition of compounds that may be of medicinal importance. Crude leaf and stem extracts (hexane, chloroform and methanol) were subjected to an antibacterial analysis against several pathogenic microorganisms. The qualitative phytochemical screening of leaf and stem extracts revealed the presence various compounds. Fluorescence microscopy qualitatively assessed the leaf and stem powdered material, which displayed various colours under bright and UV light. GC-MS chromatograms represents 10-108 peaks of various compounds detected in the leaf and stem crude extracts. Major pharmacologically active compounds found in the extracts were alpha-amyrin, flavone, phenol, phytol, phytol acetate, squalene and stigmasterol. Crude extracts positively inhibited Gram-positive and Gram-negative bacteria. Significance was established at p < 0.05 for all concentrations and treatments. These results indicate that the leaves and stems of B. albostellata are rich in bioactive compounds, which could be a potential source of antibacterial agents for treating various diseases linked to the pathogenic bacteria studied. Future discoveries from this plant could advance the use of indigenous traditional medicine and provide novel drug leads.

Effect of topical medication on the nasomaxillary skin-fold microbiome in French bulldogs

BACKGROUND

Host-microbe interactions may influence dermatitis pathogenesis in the nasomaxillary folds of French bulldogs, which is often complicated by secondary bacterial and fungal infections.

OBJECTIVE

To assess the skin-fold microbiome in systemically healthy French bulldogs and to determine the influence of topical medications on this microbiome.

ANIMALS

Nineteen healthy French bulldogs.

METHODS AND MATERIALS

Next-generation DNA sequencing was applied to characterise the microbiome composition in the nasomaxillary folds of systemically healthy French bulldogs. Subsequently, the effect of two topical products on the fold microbiome was assessed. Seven dogs were treated with a protease product (Kalzyme; enzyme) that inhibits biofilm formation without biocidal activity, six dogs were treated with a 2% chlorhexidine diacetate solution (Nolvasan; CHX) with biocidal activity, and six dogs were untreated. Dogs were randomly assigned to each group, and the investigator was blinded.

RESULTS

The primary skin bacterial phyla inhabiting the folds at inclusion were Firmicutes, Actinobacteria and Proteobacteria. The primary skin fungal phyla were Ascomycota and Basidiomycota. Topical treatment increased the diversity of bacterial and fungal compositions over time (increase in microbial diversity score: enzyme 38%, chlorhexidine 11%, control <5%) and the relative abundance of pathogens reduced significantly (enzyme, P = 0.028; CHX, P = 0.048). A clear correlation (r²  = 0.83) was observed between the abundance of clinically relevant pathogens and microbial diversity.

CONCLUSIONS

The nasomaxillary skin-fold microbiome of healthy French bulldogs contained a high abundance of clinically relevant pathogens (mean 36.4%). Topical therapy with enzyme increased microbial diversity of skin folds and reduced the relative abundance of pathogens.

Antibacterial and Antifungal Activity of the Extracts of Different Parts of Avicennia marina (Forssk.) Vierh

Increased problems associated with side effects and bacterial resistance of chemical drugs has prompted the research focus on herbal medicines in the past few decades. In the present investigation, the antimicrobial activity of the various parts of Avicennia marina (AM), a mangrove plant, has been evaluated. The plants were collected from the Jazan area of the Kingdom of Saudi Arabia. Primary extracts of roots, stem, leaves, fruits, and seeds were made in ethanol and fractioned in ethanol, ethyl acetate, petroleum ether, chloroform, and water. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the extracts were determined against Bacillussubtilis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. It has been observed that the chloroform extract of roots of the AM exhibited inhibitory effects against both S. aureus (MIC = 1.5 ± 0.03 mg/mL) and E. coli (MIC = 1.7 ± 0.01 mg/mL). The ethanolic extract of the AM roots has shown antibacterial activity against Pseudomonas aeruginosa (MIC = 10.8 ± 0.78 mg/mL), Bacillussubtilis (MIC = 6.1 ± 0.27 mg/mL), Staphylococcus aureus (MIC = 2.3 ± 0.08 mg/mL), and Escherichia coli (MIC = 6.3 ± 0.28 mg/mL). The leaf extract of the AM in ethyl acetate showed antibacterial activity against S. aureus and E. coli. Antifungal activity of these extracts was also investigated against Aspergillus fumigatus and Candida albicans. Ethanolic extract of roots and seeds of the AM has shown antifungal activity against Aspergillus fumigatus when applied individually. Ethanolic extract of the AM fruits has shown an inhibitory effect on the growth of Aspergillus fumigatus and Candida albicans. It is suggested that the plant extracts of AM have tremendous antimicrobial activity against a group of microbes, and this effect depends on both the plant part and the solvent used for extraction. Therefore, this plant can be considered to treat various diseases caused by antibiotic-resistant bacteria.

Antimicrobial resistance, mechanisms and its clinical significance

Antimicrobial agents play a key role in controlling and curing infectious disease. Soon after the discovery of the first antibiotic, the challenge of antibiotic resistance commenced. Antimicrobial agents use different mechanisms against bacteria to prevent their pathogenesis and they can be classified as bactericidal or bacteriostatic. Antibiotics are one of the antimicrobial agents which has several classes, each with different targets. Consequently, bacteria are endlessly using methods to overcome the effectivity of the antibiotics by using distinct types of mechanisms. Comprehending the mechanisms of resistance is vital for better understanding and to continue use of current antibiotics. Which also helps to formulate synthetic antimicrobials to overcome the current mechanism of resistance. Also, encourage in prudent use and misuse of antimicrobial agents. Thus, decline in treatment costs and in the rate of morbidity and mortality. This review will be concentrating on the mechanism of actions of several antibiotics and how bacteria develop resistance to them, as well as the method of acquiring the resistance in several bacteria and how can a strain be resistant to several types of antibiotics. This review also analyzes the prevalence, major clinical implications, clinical causes of antibiotic resistance. Further, it evaluates the global burden of antimicrobial resistance, identifies various challenges and strategies in addressing the issue. Finally, put forward certain recommendations to prevent the spread and reduce the rate of resistance growth.

Mechanisms of Bacterial Resistance to Antimicrobial Agents

During the past decades resistance to virtually all antimicrobial agents has been observed in bacteria of animal origin. This chapter describes in detail the mechanisms so far encountered for the various classes of antimicrobial agents. The main mechanisms include enzymatic inactivation by either disintegration or chemical modification of antimicrobial agents, reduced intracellular accumulation by either decreased influx or increased efflux of antimicrobial agents, and modifications at the cellular target sites (i.e., mutational changes, chemical modification, protection, or even replacement of the target sites). Often several mechanisms interact to enhance bacterial resistance to antimicrobial agents. This is a completely revised version of the corresponding chapter in the book Antimicrobial Resistance in Bacteria of Animal Origin published in 2006. New sections have been added for oxazolidinones, polypeptides, mupirocin, ansamycins, fosfomycin, fusidic acid, and streptomycins, and the chapters for the remaining classes of antimicrobial agents have been completely updated to cover the advances in knowledge gained since 2006.

Bacterial resistance to antimicrobial agents and its impact on veterinary and human medicine

BACKGROUND

Antimicrobial resistance has become a major challenge in veterinary medicine, particularly in the context of bacterial pathogens that play a role in both humans and animals.

OBJECTIVES

This review serves as an update on acquired resistance mechanisms in bacterial pathogens of human and animal origin, including examples of transfer of resistant pathogens between hosts and of resistance genes between bacteria.

RESULTS

Acquired resistance is based on resistance-mediating mutations or on mobile resistance genes. Although mutations are transferred vertically, mobile resistance genes are also transferred horizontally (by transformation, transduction or conjugation/mobilization), contributing to the dissemination of resistance. Mobile genes specifying any of the three major resistance mechanisms - enzymatic inactivation, reduced intracellular accumulation or modification of the cellular target sites - have been found in a variety of bacteria that may be isolated from animals. Such resistance genes are associated with plasmids, transposons, gene cassettes, integrative and conjugative elements or other mobile elements. Bacteria, including zoonotic pathogens, can be exchanged between animals and humans mainly via direct contact, but also via dust, aerosols or foods. Proof of the direction of transfer of resistant bacteria can be difficult and depends on the location of resistance genes or mutations in the chromosomal DNA or on a mobile element.

CONCLUSION

The wide variety in resistance and resistance transfer mechanisms will continue to ensure the success of bacterial pathogens in the future. Our strategies to counteract resistance and preserve the efficacy of antimicrobial agents need to be equally diverse and resourceful.

Short communication: Streptococcus species isolated from mastitis milk samples in Germany and their resistance to antimicrobial agents

Mastitis is one of the most frequent infectious diseases in dairy cattle and is a reason for antimicrobial drug usage in dairy cows. The bacteria involved in bovine mastitis are mainly Streptococcus spp., Staphylococcus spp., and coliforms. The aim of this study was to determine antimicrobial resistance among Streptococcus spp. isolated from bovine mastitis milk. Antimicrobial resistance in Strep. uberis (n=227), Strep. dysgalactiae (n=49), and Strep. agalactiae (n=3) was determined for 9 antimicrobial agents using the broth microdilution method in accordance with Clinical and Laboratory Standards Institute recommendations. Of all Streptococcus spp., 13% were multidrug resistant. The rate of multidrug resistance was higher among Strep. uberis (15%) than among Strep. dysgalactiae (6%) and Strep. agalactiae (0%). Resistance to tetracycline was the most common, followed by resistance to erythromycin, pirlimycin, and gentamicin. Resistance rates were higher on farms with more than 80 cows compared with those with fewer than 20 cows. β-Lactams should remain the drugs of choice in the treatment of streptococcal mastitis. The slightly elevated minimum inhibitory concentrations determined for these antibiotics may indicate, however, the emergence of resistant streptococci. To identify such changes in susceptibility as early as possible, antimicrobial resistance in streptococci should be surveyed regularly.

Determination of penicillin V potassium in pharmaceuticals and spiked human urine by chemiluminescence

A simple and selective method for penicillin V potassium (PVK) determination by chemiluminescence (CL) was developed. Oxidation of PVK by alkaline hydrogen peroxide produces CL, which is greatly enhanced by N, N-dimethyl formamide (DMF) and N-cetyl-N,N,N-trimethylammonium bromide (CTMAB). Optimum conditions were established using luminometry. There is a linear relationship between the chemiluminescent peak height and the amount of PVK within the range 0.5–129.5 mg L−1, with a detection limit of 0.2 mg L−1. The coefficient of variation was 1.2% for 40 mg L−1 PVK solution (n = 7). The method is very simple, has high sensitivity and good selectivity, and is usable for process control. It was successfully utilized for the determination of PVK in pharmaceuticals and spiked human urine.

Effectiveness and safety of cefovecin sodium, an extended-spectrum injectable cephalosporin, in the treatment of cats with abscesses and infected wounds

OBJECTIVE

To evaluate the effectiveness and safety of cefovecin sodium in the treatment of cats with naturally occurring skin infections (abscesses and infected wounds).

DESIGN

Multicenter (26 sites), randomized, double-blind, controlled clinical trial.

ANIMALS

Client-owned cats of any breed with naturally occurring skin infections with associated clinical signs and confirmatory bacteriologic culture results.

PROCEDURES

Cats with clinical signs of skin and soft tissue infection were randomly allocated to receive a single dose of cefovecin (8 mg/kg [3.6 mg/lb], SC) followed by placebo drops administered orally once daily for 14 days or 1 SC placebo injection followed by cefadroxil (22 mg/kg [10 mg/lb], PO, once daily for 14 days). Only one 14-day treatment course was permitted.

RESULTS

Effectiveness of cefovecin in the treatment of cats with abscesses and infected wounds was similar to that of cefadroxil. At the final assessment on day 28, 97% (86/89) of cefovecin-treated cats and 91% (80/88) of cefadroxil-treated cats were considered treatment successes. There were no serious adverse events or deaths related to treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

1 SC injection of 8 mg of cefovecin/kg for the treatment of cats with naturally occurring skin infections (wounds and abscesses) was safe and as effective as cefadroxil administered orally at 22 mg/kg, once daily for 14 days.

First report of multiresistant, mecA-positive Staphylococcus intermedius in Europe: 12 cases from a veterinary dermatology referral clinic in Germany

Resistance to cephalosporins and/or fluoroquinolones by Staphylococcus intermedius has remained low in Europe, with effective drugs generally available for systemic therapy in pets. However, multiresistant, mecA-positive S. intermedius isolated from dogs and cats is now emerging in Europe. Twelve S. intermedius isolates, highly resistant to at least five antimicrobial classes, were isolated from skin and ear infections in 11 dogs and a cat. The 12 isolates represented 23% of all S. intermedius submissions from one veterinary dermatology referral clinic in northern Germany to veterinary diagnostic laboratories during an 18-month period and resistance included cefalexin, methicillin and enrofloxacin. The animals had been referred to the clinic with recurrent superficial pyoderma, deep pyoderma, pododermatitis or chronic otitis, all unresponsive to systemic beta-lactam-antibiotics or fluoroquinolones. Infection resolved in 10 dogs and the cat on a combination of antimicrobial treatment and correction of underlying causes. Four dogs and a cat required systemic and topical therapy; in six dogs topical antimicrobial therapy alone was successful. Phenotypic and genotypic characteristics of the S. intermedius isolates were determined; species identification was confirmed by polymerase chain detection of thermonuclease genes (nuc) and the presence and expression of the gene conferring resistance to all beta-lactam antibiotics (mecA) were demonstrated in all; based on pulsed-field gel electrophoresis, six were indistinguishable, the others closely or possibly related. The emergence of multiresistant, mecA-positive S. intermedius in Europe is alarming. Zoonotic implications, awareness among veterinary laboratories and strategies for the use of antimicrobials in small animal practice need to be considered.

The efficacy and safety of cefovecin in the treatment of feline abscesses and infected wounds

OBJECTIVES

To determine the efficacy and safety of cefovecin for the treatment of bacterial abscesses and wounds in cats at clinics in Germany, France, Spain and the UK.

METHOD

Cats with abscesses or wounds were enrolled. Cats (217) were randomised to treatment with either cefovecin administered by subcutaneous injection at 14 day intervals or amoxicillin/clavulanic acid as twice-daily oral tablets for 14 days. Treatment courses were repeated at 14 day intervals, when deemed necessary. Clinicians assessing lesions were masked to treatment allocation. Only animals with a confirmed pretreatment bacterial pathogen were included in the efficacy analysis. Cases were evaluated 28 days after initiation of the final course of treatment.

RESULTS

Cefovecin was as efficacious as amoxicillin/clavulanic acid, and efficacy was 100 per cent for both treatments.

CLINICAL SIGNIFICANCE

Cefovecin, administered as a single subcutaneous injection repeated at 14 day intervals as required, was shown to be as efficacious as oral amoxicillin/clavulanic acid in the treatment of abscesses/wounds in cats.

Clinical efficacy and safety of cefovecin in the treatment of canine pyoderma and wound infections

OBJECTIVES

To determine the efficacy and safety of cefovecin in the treatment of bacterial skin infections in dogs.

METHOD

Dogs with superficial or deep pyoderma or wounds/abscesses were enrolled in three separate studies. Dogs (354) were randomised to treatment and received either cefovecin administered by subcutaneous injection at 14 day intervals, as clinically necessary, or amoxicillin/clavulanic acid as oral tablets twice daily for 14 days. Courses of treatment were repeated at 14 day intervals up to a total of four courses. Clinicians responsible for assessing lesions were masked to treatment allocation. Only animals where the presence of a pretreatment bacterial pathogen was confirmed were included in the analysis of efficacy. Cases were evaluated for clinical efficacy at 28 days after initiation of the final course of treatment. Clinical efficacy was assessed by scoring the clinical signs typical of skin infections.

RESULTS

Cefovecin demonstrated statistical non-inferiority compared with amoxicillin/clavulanic acid for all three clinical diagnoses; for cefovecin, up to 96.9 per cent efficacy was observed versus 92.5 per cent for amoxicillin/clavulanic acid.

CLINICAL SIGNIFICANCE

Cefovecin was shown to be as effective as amoxicillin/clavulanic acid administered orally in the treatment of bacterial skin infections in dogs. Cefovecin offers the additional benefit of eliminating owner non-compliance.

Perfil de isolamento microbiano em cães com otite média e externa associadas

Comparou-se o perfil de isolamento microbiano de amostras coletadas de cães com otite média (OM) e externa (OE) associadas. Sessenta e quatro cães com otite média e externa foram avaliados durante 10 meses. Amostras dos condutos auditivos externos foram coletadas com auxílio de swabs estéreis e aquelas do ouvido médio pela técnica cirúrgica da osteotomia da bula timpânica. Os microrganismos foram cultivados e identificados de acordo com os métodos previamente descritos, e a susceptibilidade a antimicrobianos avaliada pelo método de difusão em ágar estabelecido pelo National Committee for Clinical Laboratory Standards. Bactérias anaeróbias estritas não foram isoladas em qualquer amostra. Todas as amostras de OE mostraram crescimento bacteriano e/ou fúngico. Na OM, a positividade nas culturas foi de 48%. Os microrganismos mais isolados na OE foram: Bacillus sp. (26,9%), M. pachydermatis (22,2%) e S. intermedius (21,7%); na OM foram: S. intermedius (32,5%), S. aureus subsp. aureus (22,5%) e bacilos Gram-negativos não fermentadores (10,0%). Observou-se alguma diferença no perfil de isolamento entre os quadros de OM e OE em 96,7% dos animais. Verificou-se elevada resistência de cepas de S. intermedius à penicilina G, ampicilina, eritromicina, tetraciclina e clindamicina.

Masked, controlled study to investigate the efficacy of a Staphylococcus intermedius autogenous bacterin for the control of canine idiopathic recurrent superficial pyoderma

A masked, controlled study was designed to investigate the clinical efficacy of a staphylococcal autogenous bacterin for the control of canine idiopathic recurrent pyoderma (IRP). Ten dogs with at least three prior episodes of recurrent superficial pyoderma were recruited. All were screened and found to be free of ectoparasitic and fungal disease and failed to respond favourably to a dietary trial. Those exhibiting signs of pruritus responded completely to antibacterial therapy. Haematological and biochemical parameters were generally unremarkable and all dogs were euthyroid. Staphylococcus intermedius cultures from lesions were used to produce an autogenous bacterin for each animal. A numerical 'lesion score' was allocated and dogs were randomly divided into two groups of five (groups 1 and 2). Both groups received a 4-week course of antibiotic; group 1 also received concurrent s/c injections of bacterin, which continued until week 10. Group 2 received no additional therapy. All dogs were re-examined and rescored at weeks 5 and 10 and repeat blood samples were submitted at week 10 to screen for adverse effects. Comparison of scores at week 0 and week 5 (Mann-Whitney U-test) revealed no significant differences between the groups. At week 10, group 2 (control group) individual lesion scores were significantly higher compared with the group receiving bacterin (P < 0.05) and there was a significantly greater increase in the sum of the individual lesion scores for group 2 compared with group 1, from week 5 to week 10 (P < 0.05). No adverse reactions to bacterin therapy were detected. These results suggest that autogenous bacterins may provide an alternative, safe, effective method for the control of canine IRP. Further studies using larger groups of dogs and for a longer follow-up period are now warranted.

Chemiluminescence flow-injection analysis ofβ-lactam antibiotics using the luminol–permanganate reaction

A new flow injection chemiluminescence (CL) method has been developed for the determination of six beta-lactam antibiotics, including amoxicillin, cefadroxil, cefoperazone sodium, cefazolin sodium, cefradine and ceftriaxone sodium. When the antibiotic was injected into a stream of KMnO4 with alkaline luminol, a strong CL signal was produced. The method allows the measurements of 0.1-50.0 mg/L amoxicillin, 0.1-80.0 mg/L cefadroxil, 1.0-30.0 mg/L cefoperazone sodium, 1.0-30.0 mg/L cefazolin sodium, 3.0-50.0 mg/L cefradine and 3.0-50.0 mg/L ceftriaxone sodium. The detection limits are 0.05 mg/L for amoxycillin, 0.05 mg/L for cefadroxil, 0.4 mg/L for cefoperazonum sodium, 0.4 mg/L for cefazolin sodium, 0.8 mg/L for cefradine and 0.8 mg/L for ceftriaxone sodium. The relative standard deviations in 11 repeated measurements are 0.6%, 0.8%, 1.5%, 1.2%, 0.4% and 0.3% for 3.0 mg/L amoxicillin, 1.0 mg/L cefadroxil, 10.0 mg/L cefoperazone sodium, 10.0 mg/L cefazolin sodium, 10.0 mg/L cefradine and 10.0 mg/L ceftriaxone sodium, respectively. The method was successfully applied to the determination of amoxicillin in pharmaceutical preparations. A possible CL reaction mechanism is also discussed.

Survey of condition-based prescribing of antimicrobial drugs for dogs at a veterinary teaching hospital

A database of the prescriptions of antimicrobial drugs for the treatment of common infectious diseases in dogs at the Finnish Veterinary Teaching Hospital was searched to determine to what extent national guidelines were being followed. Twenty-two per cent of 5918 dogs were treated orally with antimicrobial drugs. The most commonly used drugs were beta-lactams (49 per cent) of which cephalexin and amoxycillin-clavulanate were most widely prescribed. The usage of fluoroquinolones was only 2.8 per cent. The prescription of antimicrobials for pyoderma was contrary to Finnish guidelines, but the use of cephalexin or amoxycillin-clavulanate as first-line drugs instead of macrolides or lincosamides or trimethoprim-sulphonamides was acceptable because of the presence of resistance by canine staphylococci. The drug most commonly used to treat acute urinary tract infections was trimethoprim-sulphonamide, in agreement with the guidelines. Antimicrobial drugs were used excessively after surgical procedures, and for treating acute gastrointestinal disturbances and small wounds and traumas.

Antimicrobial resistance in staphylococci from canine pyoderma: a prospective study of first-time and recurrent cases in Sweden

In a prospective study involving eight veterinary clinics during 1995 and 1996, samples from first-time and recurrent cases of canine pyoderma were collected by a needle technique. Three hundred and ninety-four staphylococci were isolated and their susceptibility to various antimicrobial drugs was assessed by a microdilution technique. Resistance to macrolides, lincosamides, fusidic add, tetracycline and streptomycin was significantly more common in isolates from the recurrent cases than from the first-time cases; 20 per cent of the isolates from the first-time cases were resistant to three or more of the antimicrobials tested, compared with 45 per cent of those from the recurrent cases. Coresistance between macrolide-lincosamides, tetracyclines and streptomycin was common. No resistance to penicillinase-stable beta-lactams was observed. A comparison with earlier studies indicated that there had been a marked increase in resistance during the previous five years.

Identification and antimicrobial susceptibility of coagulase positive staphylococci isolated from healthy dogs and dogs suffering from otitis externa

A total of 67 strains of coagulase positive staphylococci isolated from healthy dogs and dogs suffering from otitis externa were studied. Twenty-two isolates were from healthy dogs (five from hound dogs and 17 from companion dogs) and 45 from dogs suffering otitis externa (14 from hound dogs and 31 from companion dogs). Presumptive identification was attempted using the following tests: production of acetoin, anaerobic utilization of mannitol, acid production from mannitol, presence of beta-galactosidase, and growth on P agar supplemented with different concentrations of acriflavine. Susceptibility of staphylococci to 16 antibiotics was determined. Most effective antibiotics were imipenem, amoxycillin/clavulanic acid, ciprofloxacin, tobramycin, gentamicin and marbofloxacin. Penicillin, ampicillin and polymyxin B showed the lowest activity. There were no significant differences in antimicrobial susceptibility among isolates from healthy dogs and dogs suffering from otitis externa.

Prevalence of and resistance to anti-microbial drugs in selected microbial species isolated from bulk milk samples

The prevalence of strains of Staphylococcus aureus, coagulase-negative (CN) staphylococci, Listeria monocytogenes, Escherichia coli, Enterococcus faecalis, E. faecium and Bacillus cereus, was investigated in 111 bulk milk samples. Staphylococcus aureus was isolated from 38 samples, CN staphylococci from 63 samples, E. coli from 49 samples, E. faecalis or E. faecium from 107 samples, and L. monocytogenes from two samples. Bacillus cereus was not found in any of the samples and three samples were free of any of the selected species. Sensitivity to the anti-microbial drugs amikacin, ampicillin, ampicillin + sulbactam, cephalothin (CLT), cephotaxime, clindamycin, chloramphenicol (CMP), co-trimoxazole, erythromycin (ERY), gentamicin, neomycin, norfloxacin, oxacillin, penicillin, streptomycin (STR), tetracycline (TTC) and vancomycin was tested using the standard dilution technique. Minimum inhibitory concentration (MIC) characteristics (MIC50, MIC90, MIC range) were determined for each microbial species. Resistance against one or more anti-microbial drugs was found in 93% of S. aureus, 40% of CN staphylococci, 73% of E. coli, 88% of E.faecalis, 55% of E.faecium, and one L. monocytogenes strain. Most of the strains, particularly enterococci, were resistant to STR, TTC, and ERY (MIC50 4 microg/ml). A high percentage of staphylococci were resistant to beta-lactam antibiotics. High resistance to CLT was found in 11 strains of E. coli (MIC 256 microg/ml) and strains resistant to CMP (MIC90 16 microg/ml) were detected. The highest numbers of resistance phenotypes were found in E. coil (16) and CN staphylococci (12). Eighteen identical resistance phenotypes were demonstrated in indicator bacteria (E. coli, E. faecalis, E. faecium) and pathogens (S. aureus, CN staphylococci) isolated from the same bulk milk sample. The obtained resistance data were matched against the herd owners' information on therapeutic use of the drugs. This confrontation could not explain the findings of strains resistant to ERY or CMP. Our findings are evidence of selection of resistant strains among not only pathogenic agents, but also among indicator bacteria which can become significant carriers of transmissible resistance genes.

Analysis of beta-lactam antibiotics in incurred raw milk by rapid test methods and liquid chromatography coupled with electrospray ionization tandem mass spectrometry

A recently developed confirmatory LC-MS method has been applied to the quantification of five major beta-lactam antibiotics in suspect raw bovine milk samples that gave a positive response with receptor-based (BetaStar) and rapid microbial inhibitory screen tests (Delvotest SP). In total, 18 presumptive positive raw milk samples were reanalyzed; 16 samples showed traces of antibiotic residues that could be identified and quantified by the LC-MS method, ranging from the limits of confirmation up to 38 microg/kg. Of the positive samples, only five (approximately 30%) were found to be violative of EU maximum residue limits. The most frequently detected antibiotic residues were cloxacillin and penicillin G, the former often in combination with amoxicillin or ampicillin. This study compares the results obtained by the three methods on identical samples and addresses how these relate to certain criteria such as sensitivity and selectivity. Furthermore, the limitations of the LC-MS method and the potential impact of the presence of frequently more than one residue in the same milk sample on the response of the rapid test methods are discussed.

Use of antimicrobial agents in veterinary medicine and food animal production

Antimicrobial resistance is a growing area of concern in both human and veterinary medicine. This review presents an overview of the use of antimicrobial agents in animals for therapeutic, metaphylactic, prophylactic and growth promotion purposes. In addition, factors favouring resistance development and transfer of resistance genes between different bacteria, as well as transfer of resistant bacteria between different hosts, are described with particular reference to the role of animals as a reservoir of resistance genes or resistant bacterial pathogens which may cause diseases in humans.

Simultaneous determination of five beta-lactam antibiotics in bovine milk using liquid chromatography coupled with electrospray ionization tandem mass spectrometry

A multiresidue method for the detection of five important beta-lactam antibiotics (amoxicillin, ampicillin, cloxacillin, oxacillin, penicillin G) in fresh milk is presented that allows quantitation of the analytes well below established legislative limits. The method avoids the use of acid during the extraction procedure and entails a cleanup step over a C18 cartridge. The analytes are separated and detected by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) using a stable isotope-labeled internal standard. Mass spectral acquisition is done in the positive ion mode by applying selected reaction monitoring of two or more fragmentation transitions per analyte to provide a high degree of sensitivity and specificity. The typical recoveries for all five beta-lactams in fresh milk ranged from 76 to 94% at a fortification level of 4 microg/kg. This study also addresses common problems encountered in the stability of penicillins during sample preparation as well as the employment of postcolumn infusion of a standard compound to verify potential matrix-induced signal suppression in ESI-MS.