Tetracycline Resistance of Enterobacteriaceae Isolated From Feces of Synanthropic Birds

Tetracycline is a broad-spectrum antibiotic which is commonly used in humans and animals for treatment of bacterial infections. Therefore, tetracycline-resistant Enterobacteriaceae species found in the nature, humans, and animals are usually considered a serious health concern. The feces of birds that live with humans may be a source for of these antibiotic resistant bacteria. For this reason, presence of tetracycline-resistant Enterobacteriaceae in bird droppings collected from 18 different breeders and pet shops fed in Istanbul was investigated by cultural and molecular methods in terms of the presence of that a/b gene. In addition, susceptibilities of isolates to various antibiotics were also determined. The current study reported that Enterobacter cloacae, Citrobacter freundi, Escherichia coli, Edwardsiella spp., Enterobacter spp., Escherichia vulneris, Klebsiella pneumonia, Pantoea agglomerans, Proteus mirabilis, Pantoe spp., Pseudomonas spp., Serratia marcescens, Salmonella spp., Shigella spp. were isolated from the samples. Ninety-seven of the isolates (97/150) were resistant to tetracycline (65.2%). In addition, the isolates were resistant to other antibiotic medications and 114 of them (58%) evaluated as multi drug resistant. The tet (A) and tet (B) genes were found in bacteria isolated from synantrophic birds’ feces as 46.6% and 8%, respectively. Although working conditions are limited, the results obtained provide baseline information regarding antibiotic resistance to Enterocatericeae isolates obtained from captive birds’ feces. Thus, the results of the present study emphasize the necessity of genotypic resistance research in future studies to help maintain antibiotic treatment efficacy for Enterocatericeae infections.     

Bacterial isolates and antimicrobial susceptibilities in equine bacterial ulcerative keratitis (1993--2004)

REASONS FOR PERFORMING STUDY: Bacterial ulcerative keratitis is a common and often vision-threatening problem in horses. Emerging bacterial resistance to commonly used topical antibiotics has been demonstrated. Previous antibiotic use may alter the antimicrobial susceptibility of bacterial isolates. OBJECTIVES: To document aerobic bacterial isolates and associated bacterial susceptibilities from horses with ulcerative keratitis treated at the University of Tennessee between January 1993 and May 2004 and determine whether prior antibiotic therapy affected antimicrobial susceptibility of the isolates. METHODS: Medical records from horses with ulcerative keratitis and positive aerobic bacterial cultures and antimicrobial susceptibility were evaluated. Clinical history regarding antibiotic therapy prior to culture was documented. RESULTS: Fifty-one aerobic bacterial isolates from 43 horses were identified. Streptococcus equi subspecies zooepidemicus was the most commonly isolated organism, accounting for 33.3% of all isolates, followed by Pseudomonas aeruginosa (11.8%), Staphylococcus spp. (11.8%) and Gram-negative nonfermenting rods (7.8 %). No resistance was noted amongst S. equi ssp. zooepidemicus to cephalothin, chloramphenicol or ciprofloxacin. Only 64 % of S. equi ssp. zooepidemicus isolates were sensitive to bacitracin. No resistance was noted among P. aeruginosa to gentamicin, tobramycin or ciprofloxacin. Antibiotic therapy with neomycin-polymixin B-bacitracin prior to presentation and culture was documented in 11/17 horses in which S. equi ssp. zooepidemicus was isolated and in 4/6 horses in which P. aeruginosa was isolated. Three horses received topical corticosteroids prior to culture, of which 2 had polymicrobial infections. CONCLUSIONS: S. equi ssp. zooepidemicus and P. aeruginosa were the most frequently isolated bacterial organisms in equine ulcerative keratitis. No significant trends in aminoglycoside or fluoroquinolone resistance were noted among these organisms. However, the resistance of S. equi ssp. zooepidemicus to bacitracin with common use of this antibiotic suggests that previous antibiotic therapy probably affects antimicrobial resistance. POTENTIAL RELEVANCE: Therapy prior to culture may play an important role in antimicrobial susceptibility of corneal bacterial isolates. Corticosteroid use may increase the risk of polymicrobial infections of corneal ulcers, leading to a worse prognosis. Although significant fluoroquinolone resistance has not been documented in the veterinary literature, these antimicrobials should be reserved for known infected corneal ulcers and not used for prophylaxis. Empirical antibiotic therapy should not only be guided by clinical signs, but also take into consideration previous antimicrobial and corticosteroid therapy.     

Genomic Description of Antibiotic Resistance in Escherichia coli and Enterococci Isolates from Healthy Lusitano Horses

Antibiotic resistance is a global problem, and it is known that commensal bacteria can act as reservoir of antibiotic resistance genes of clinical importance. The aim of the present study was to determine the antibiotic resistance phenotype and mechanisms implicated in resistance of Escherichia coli and Enterococcus spp. isolates collected from fecal samples of 90 Lusitano horses from Portugal. Sixteen of the 71 E. coli isolates (22.5%) recovered showed resistance to at least one of the antibiotics tested. The number of E. coli isolates resistant to streptomycin, tetracycline, chloramphenicol, ampicillin, trimethoprim-sulfamethoxazole, and gentamicin was 9, 7, 6, 3, 2, and 1, respectively. The bla_TEM-1 and bla_OXA-1 genes were detected in ampicillin-resistant isolates and the sul2 and dfrA1 genes in trimethoprim-sulfamethoxazole-resistant, while the aac(3)-I, floR and tet(A) were found in the gentamicin, chloramphenicol and tetracycline-resistant isolates, respectively. Twenty-two of the 71 (31%) recovered enterococci showed antibiotic resistance for at least one of the tested antibiotics, and resistant isolates were identified as Enterococcus faecium (n = 14), E. faecalis (n = 3), E. hirae (n = 2), and Enterococcus spp. (n = 3). The erm(B) and erm(C) genes were identified in erythromycin-resistant enterococci and the tet(M) and/or tet(L) genes in tetracycline-resistant isolates. The slight prevalence of antibiotic resistance among commensal bacteria of healthy Lusitano horses can improve the treatment of upcoming infections in these horses because these microorganisms can be considered as antimicrobial indicator bacteria.     

Bacteria and antibiotic resistance detection in fractures of wild birds from wildlife rehabilitation centres in Spain

Anatomic adaptations make birds more prone to open fractures with exposed bone parts losing vascularization. As a result of this exposure, fractures are colonized by different microorganisms, including different types of bacteria, both aerobic and anaerobic, causing osteomyelitis in many cases. For this reason, antibiotic treatment is common. However, carrying out antibiotic treatment without carrying out a previous antibiogram may contribute to increased resistance against antibiotics, especially in migratory wild birds. In this paper, bacterial counts regarding fracture type, bacterial identification and antibiotic resistance have been analysed in wild birds from wildlife rehabilitation centres in Spain. The results obtained showed that open fractures had higher bacterial counts (CFU/mL) than closed ones. Bacteria in family Enterobacteriaceae, identified were Escherichia spp., Enterobacter spp., Shigella spp., Hafnia alvei, Proteus mirabilis, Leclercia adecarboxylata and Pantoea agglomerans. Other bacteria present in wild birds’ fractures were Aeromonas spp., Enterococcus spp. Bacillus wiedmannii and Staphylococcus sciuri. All species found presented resistance to at least one of the antibiotics used. Wild birds can be implicated in the introduction, maintenance and global spreading of antibiotic resistant bacteria and represent an emerging public health concern. Results obtained in this paper support the idea that it is necessary to take this fact into account before antibiotic administration to wild animals, since it could increase the number of bacteria resistant to antibiotics.     

ANTIMICROBIAL SUSCEPTIBILITY PATTERNS OF BIOFILM FORMING STAPHYLOCOCCUS AUREUS ISOLATED FROM PIGEON EXTERNAL OCULAR INFECTIONS

Pathogenic microorganisms are commonly associated with external ocular infections in birds. Pathogen virulence factors as well as reduced host defenses resulting from poor living conditions, nutrition, genetics, physiology, hygiene, fever, and age may increase host susceptibility. Staphylococcus species are bacteria known to serve as opportunistic pathogens in eye infections. The changing profile of microorganisms involved in ocular infections and the emergence of acquired microbial resistance dictate the need for investigative studies regarding bacterial profiles and antimicrobial susceptibility patterns for external ocular infections. The aim of this study was to determine the prevalence of Staphylococcus aureus ocular infections in pigeons and to evaluate their biofilm production ability and antibiotic resistance patterns. Twenty pigeons with confirmed eye infections were included in this project. Conjunctival specimens were collected with swabs presoaked in sterile normal saline. Bacterial growth was identified by standard laboratory procedures and susceptibility testing of the isolates was performed by the Kirby-Bauer method. The ability of the isolates to form a biofilm was also assessed using the microtiter plate method. Of the 20 specimens processed, 20% of the pigeons had staphylococcal eye infections. The resistance pattern of these isolates showed that Staphylococcus spp. from pigeon samples were resistant to tetracycline (100%), erythromycin (100%), azithromycin (100%), nalidixic acid (100%), and cefazolin (50%). All of the Staphylococcus spp. isolated from the pigeons were susceptible to gentamycin and furazolidone. The results of the biofilm detection test showed that 75% of the isolates were biofilm producers. In conclusion, biofilm forming S. aureus with multidrug resistance patterns were the most prevalent bacteria isolated from the pigeons examined in this research study.     

A retrospective study of 192 horses affected with septic arthritis/tenosynovitis.

The medical records of 192 horses with septic arthritis/tenosynovitis 1979-1989 were reviewed. Forty-three horses developed infection after an intra-articular injection, 46 following a penetrating wound, 25 following surgery, 66 were foals less than 6 months old, and 12 were adult horses without a known aetiology. Haematogenous infection of a joint occurs in adult horses and should be considered as a differential diagnosis in horses with an acute onset of severe lameness. The aetiology of the infection had a significant effect on the type of bacteria identified by culture. Staphylococcus was cultured from most of the horses that developed infection following a joint injection or surgery, 69% of the horses from which an organism was identified. Horses that developed infection secondary to a penetrating wound frequently provided cultures of more than one organism; Enterobacteriaceae and anaerobes were more frequently isolated in this group. The most common organisms isolated from foals were Enterobacteriaceae; E. coli was identified in more than 27% of the foals. The hock was the most frequently involved joint. Multiple treatments were used over the 10-year period of study. Survival rates were lowest in foals; only 45% survived to be released from the hospital. Survival was greater in adult horses; 85% of the horses that were treated were released from the hospital. Survival was significantly greater in horses with septic tenosynovitis; all 14 of the horses that were treated survived. Survival was not significantly affected by the joint involved or by the type of bacteria cultured from the synovial fluid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fecal carriage of multi-drug resistant and extended spectrum β-lactamases producing E. coli in household pigeons,Bangladesh

Antibiotic resistance and ESBL constitute a risk to human and animal health. Birds residing close to humans could mirror the spectrum of human associated antibiotic resistance. Household pigeons were screened in Bangladesh to shed light on human associated, as well as, environmental antibiotic resistance. Escherichia coli from pigeons (n = 150) were tested against 11 antibiotics. 89% E. coli isolates were resistant to one or more critically important human antibiotics like ampicillin, cefadroxil, mecillinam, ciprofloxacin, gentamicin and tigecycline. No carbapenamase-producers were detected and the lower ESBL prevalence (5%) in pigeons. ESBL-producing E. coli isolates had bla_CTX-M-15 genes. Pigeons shared some bacterial clones and had bird associated sequence types like E. coli ST1408. Fecal carriage of bacteria resistance of critically important human antibiotics, together with examples of shared genotypes among pigeons, indicate the human-birds and bird to bird transmissions are important in the epidemiology of antibiotic resistance.     

Infections caused by multidrug-resistant bacteria in an equine hospital (2012–2015)

Multidrug-resistant (MDR) bacteria are an emerging threat in human and veterinary medicine. There are few reports about infections caused by MDR isolates in horses. The aim of this study was to provide an overview of infections caused by MDR bacteria at the Equine Hospital Zurich between 2012 and 2015. Medical records were searched for horses with confirmed MDR bacterial infection. Multidrug resistance was defined according to human guidelines specific for each pathogen. MDR isolates were most commonly isolated from post-procedural infections (53/110, 48%), followed by musculoskeletal (16/110, 15%) and soft tissue infections (16/110, 15%). Escherichia coli (32/158, 20%) and Staphylococcus aureus (25/158, 16%) were the most common isolates. High resistance rates precluded therapy with commonly used antimicrobial drugs. The overall mortality rate was 20% (22/108) but depended on the localisation of the infection. Antimicrobial treatment prior to development of infection was reported for 89% (91/102) of horses. This study showed that MDR pathogens, mainly MDR E. coli and MRSA, cause a considerable number of infections in horses. A wide range of infections was seen, however, nosocomial infections predominated. These cases are typically hospitalised, pretreated with antibiotics, and suffering from comorbidities putting them at high-risk for acquiring infections caused by MDR isolates. The mortality of such infections was generally low but depended on site of infection.     

Efficacy of anti-staphylococcal protein P128 for the treatment of canine pyoderma: potential applications

In this study, we demonstrate the antibacterial activity of P128 on Staphylococcus isolates responsible for canine pyoderma. Eighty seven swabs were collected from dogs suffering from pyoderma and subjected to antibiotic sensitivity test and 46 Staphylococcus strains were isolated and characterized. In-vitro antimicrobial susceptibility testing with P128 was done by Minimum Inhibitory Concentration (MIC) method as per CLSI guidelines. All the Staphylococci isolated from the dogs with pyoderma, although showed resistance to various antibiotics tested, were lysed by P128. Clinical efficacy of P128 was examined in 17 dogs with pyoderma by application of the P128 hydrogel twice daily for 8 days and the results indicated complete healing of all the lesions of all the dogs under treatment. Under the conditions of this study, P128 was found to be a potent convenient proteinaceous drug for the treatment of staphylococcal pyoderma in dogs.     

Characterization of a Streptococcus equi ssp. equi Isolate From a Strangles Outbreak in Thailand

Strangles, which is caused by Streptococcus equi ssp. equi, is one of the major infectious respiratory diseases in horses. Knowledge of isolates from different areas of the world is important for investigating the different strains of the disease. In contrast to many other countries, currently little is known about S. equi ssp. equi isolates in Thailand. In 2014, a farm in Thailand imported 20 horses from Europe. Approximately 1 month after arrival, 50% of the horses had developed pyrexia, mucopurulent nasal discharge, and abscesses of the mandibular lymph nodes. Nasal swabs of mucopurulent discharge were sent to a diagnostic laboratory, and two isolates of S. equi ssp. equi were identified. One of the isolates was further characterized using seM gene polymerase chain reaction and sequence analysis. The seM sequence was then compared to the database of PubMLST-seM. It was found to contain SeM allele 48, an allele isolated from horses in the United Kingdom in 2006 and 2010. This result demonstrates the usefulness of SeM allele identification as a tool for investigating the source of related strains and for the epidemiologic study of strangles. To the best of the authors' knowledge, this is the first report of the identification of an SeM allele of the S. equi ssp. equi isolate in Thailand.     

Comparing the minimum inhibitory and mutant prevention concentrations of selected antibiotics against animal isolates of Pasteurella multocida and Salmonella typhimurium

Historically, the use of antibiotics was not well regulated in veterinary medicine. The emergence of antibiotic resistance (ABR) in pathogenic bacteria in human and veterinary medicine has driven the need for greater antibiotic stewardship. The preservation of certain antibiotic classes for use exclusively in humans, especially in cases of multidrug resistance, has highlighted the need for veterinarians to reduce its use and redefine dosage regimens of antibiotics to ensure efficacy and guard against the development of ABR pathogens. The minimum inhibitory concentration (MIC), the lowest concentration of an antibiotic drug that will prevent the growth of a bacterium, is recognised as a method to assist in antibiotic dosage determination. Minimum inhibitory concentrations sometimes fail to deal with first-step mutants in bacterial populations; therefore dosing regimens based solely on MIC can lead to the development of ABR. The mutant prevention concentration (MPC) is the minimum inhibitory antibiotic concentration of the most resistant first-step mutant. Mutant prevention concentration determination as a complementary and sometimes preferable alternative to MIC determination for veterinarians when managing bacterial pathogens. The results of this study focused on livestock pathogens and antibiotics used to treat them, which had a MIC value of 0.25 µg/mL for enrofloxacin against all 27 isolates of Salmonella typhimurium. The MPC values were 0.50 µg/mL, with the exception of five isolates that had MPC values of 4.00 µg/mL. The MPC test yielded 65.52% (18 isolates) Salmonella isolates with florfenicol MICs in the sensitive range, while 11 isolates were in the resistant range. Seventeen isolates (58.62%) of Pasteurella multocida had MIC values in the susceptible range and 41.38% (12 isolates) had an intermediate MIC value. Mutant prevention concentration determinations as done in this study is effective for the antibiotic treatment of bacterial infections and minimising the development of resistance. The MPC method can be used to better control to prevent the development of antibiotic drug resistance used in animals.     

Antibiotic resistance patterns in fecal bacteria isolated from Christmas shearwater (Puffinus nativitatis) and masked booby (Sula dactylatra) at remote Easter Island

Antibiotic use and its implications have been discussed extensively in the past decades. This situation has global consequences when antibiotic resistance becomes widespread in the intestinal bacterial flora of stationary and migratory birds. This study investigated the incidence of fecal bacteria and general antibiotic resistance, with special focus on extended spectrum beta-lactamase (ESBL) isolates, in two species of seabirds at remote Easter Island. We identified 11 species of bacteria from masked booby (Sula dactylatra) and Christmas shearwater (Puffinus nativitatis); five species of gram-negative bacilli, four species of Streptococcus (Enterococcus), and 2 species of Staphylococcus. In addition, 6 types of bacteria were determined barely to the genus level. General antibiotic susceptibility was measured in the 30 isolated Enterobacteriaceae to 11 antibiotics used in human and veterinary medicine. The 10 isolates that showed a phenotypic ESBL profile were verified by clavulanic acid inhibition in double mixture discs with cefpodoxime, and two ESBL strains were found, one strain in masked booby and one strain in Christmas shearwater. The two bacteria harboring the ESBL type were identified as Serratia odorifera biotype 1, which has zoonotic importance. Despite minimal human presence in the masked booby and Christmas shearwater habitats, and the extreme geographic isolation of Easter Island, we found several multiresistant bacteria and even two isolates with ESBL phenotypes. The finding of ESBLs has animal and public health significance and is of potential concern, especially because the investigation was limited in size and indicated that antibiotic-resistant bacteria now are distributed globally.     

Epidemiology of the colonization and acquisition of methicillin-resistant staphylococci and vancomycin-resistant enterococci in dogs hospitalized in a clinic veterinary hospital in Spain

Antibiotic resistance is one of the biggest threats to human and animal health. Methicillin-resistant Staphylococcus spp. (MRS) and vancomycin-resistant Enterococcus spp. (VRE) are of increasing importance in hospital and/or nosocomial infections and represent a potential risk of transmission to humans from infected or colonized companion animals. Studies on the risk factors associated with colonization by multiresistant bacteria in animals are scarce. The present study aimed to estimate the prevalence and incidence of MRS and VRE in canine patients hospitalized in a veterinary hospital and to identify the risk factors for its acquisition and persistence.Nasal and perianal swabs were obtained from 72 dogs. Antimicrobial susceptibility assays and molecular detection of mecA and van genes were performed.A prevalence of 13.9% and incidence of 26.5% was observed in dogs colonized by MRS at hospital admission and release, respectively, higher values than those described in most veterinary studies. Thirty-five Staphylococcus isolates had mecA gene and showed higher resistance levels to most of the antimicrobials evaluated. Previous and concomitant use of antibiotics and corticosteroids has been associated with an increase in MRS colonization. The use of antibiotics in other animals living with the canine patients has also been identified as an associated factor, suggesting cross transmission. The presence of van-resistant genes from Enterococcus spp. was not detected.Pets should be considered possible vehicles of transmission and reservoirs for MRS bacteria and veterinary hospitals should be considered high-risk environments for the occurrence and spread of nosocomial infections and resistant bacteria.     

Detection of methicillin‐resistant Staphylococcus aureus (MRSA) in the microbial flora from the conjunctiva of healthy donkeys from Sicily (Italy)

Objective To describe the bacterial flora present in the normal conjunctiva of donkeys from Sicily (Italy). Animals studied A total of 46 healthy donkeys housed in 3 locations within the territory of Palermo (Sicily, Italy) were studied. Donkeys ranged from 2 to 13 years of age, with a median age of 6 years. Procedures Forty‐six conjunctival swabs were obtained from both eyes of each animal, and specimens were cultured for aerobic bacteria. Furthermore, the antimicrobial activity of methicillin (1 μg) and oxacillin (5 μg) on Staphylococcus spp. isolates was evaluated, and a specific PCR assay, which allows the detection of mecA gene specific for methicillin‐resistant Staphylococcus aureus (MRSA) strains, was performed. Results Forty of 46 (86.9%) donkeys were positive for bacteria. Eighty bacterial isolates, representing 9 bacteria genera, were successfully cultured. The most frequently recovered bacterial genus was Staphylococcus (52/80 isolates; 65%). Several strains (20/80 isolates; 25%) belonging to the Enterobacteriaceae family were also isolated, among which the most frequently isolated genus was Enterobacter (eight isolates). Of the 52 Staphylococcus spp. isolates, 14 (26.9%) strains were oxacillin/methicillin resistant. The mecA gene was detected in 6/52 (11.5%) strains. Conclusions This study contributes to the knowledge about normal ocular flora and MRSA occurrence in donkey farms in Sicily.     

Antibiotic resistance and molecular characterization of ophthalmic Staphylococcus pseudintermedius isolates from dogs

The prevalence, virulence potential, and antibiotic resistance of ophthalmic Staphylococcus pseudintermedius (SP) isolated from dogs were examined. Sixty-seven Staphylococcus species were isolated from ophthalmic samples and surveyed for species-specific sequences in the Staphylococcus intermedius group (SIG) nuclease gene (SInuc), exfoliative toxin gene for SIG (siet), and antibiotic resistance genes (blaZ and mecA). PCR-restriction fragment length polymorphism analysis of the pta gene was also performed. Fifty isolates were identified as SIG strains, all of which were found to be SP. The blaZ gene was detected in 42 of the 50 SP strains and mecA gene was observed in 18 of the 50 SP strains. The 50 SP strains were most susceptible to amoxicillin/clavulanic acid (94%) and chlorampenicol (70%), and highly resistant to tetracycline (94%) and penicillin (92%). It was also found that 16 (88.9%) mecA-positive SP strains were resistant to oxacillin, tetracycline and penicillin. All mecA-positive SP were resistant to more than four of the eight tested antibiotics and therefore considered SP with multi-drug resistance (MDR). Our results indicate a high prevalence of antibiotic resistance genes in ophthalmic SP along with a close relationship between MDR SP strains and the mecA gene. Based on our findings, judicious administration of antibiotics to companion dogs is necessary.     

The first nosocomial outbreak of methicillin-resistant Staphylococcus aureus in horses in Sweden

Background

Methicillin-resistant Staphylococcus aureus (MRSA) in animals is a rare finding in Sweden. In horses, MRSA was first detected in a screening survey in 2007. In 2008, six clinical cases occurred in an equine hospital, indicating an outbreak.

Method

All MRSA isolates detected, 11 spa-type t011 and one t064 (n = 12), in infected horses (n = 10) and screening of horses (n = 2) in Sweden from December 2007 to March 2010 were retrospectively analysed with pulsed-field gel electrophoresis (PFGE) using Cfr9I and ApaI restriction enzymes, to study relationship between the isolates. Medical records of infected horses and outbreak investigation notes were scrutinised to monitor the clinical outcome and other aspects of the outbreak.

Results

Eight of the 10 infected horses were linked to one equine hospital and two to another hospital in the same region. The six horses infected with MRSA in 2008 underwent surgery during the period 22 May-7 July in one of the hospitals. Four more infections linked to the two hospitals were notified between 2009 and March 2010.Nine of the 11 spa-type t011 isolates had identical Cfr9I and ApaI PFGE pattern. All six infected horses from 2008 presented with this MRSA. Two t011 isolates differed in one and two bands, respectively, in PFGE.Nine horses suffered from surgical site infections (SSI). No antimicrobials were used following the MRSA diagnosis and the infections cleared. The time from surgery to MRSA diagnosis differed greatly between the horses (range 15-52 days).

Conclusions

Association in time and space of six horses infected with an identical MRSA strain of spa-type t011 confirmed an outbreak. Two isolates found in 2009 and 2010 in the outbreak hospital were closely related to the outbreak strain, indicating one circulating strain. Both spa-type t011 and t064 have been reported in horses in Europe prior to these findings. The observation that the infections cleared although antimicrobials were not used is encouraging for future prudent use of antimicrobials. The time from surgery to bacteriological diagnosis was not acceptable in most cases, as contagious spread was a risk. Sampling when symptoms of infection are noticed and accurate analysis are thus important.     

Methicillin-resistant coagulase-negative staphylococci isolated from healthy horses in Japan

OBJECTIVE: To determine patterns of methicillin-resistant staphylococci isolated from apparently healthy horses. SAMPLE POPULATION: 44 horses from 8 riding clubs in Japan. PROCEDURE: Methicill in-resistant staphylococci were isolated from the skin or nares, using a selective medium containing a beta-(symboric) lactam antibiotic, ceftizoxime. Clonality of isolates was determined by use of pulsed-field gel electrophoresis. Detection of mecA, mecl, and mecR1 genes was accomplished by use of polymerase chain reactions. RESULT: Of the 44 horses, 13 (29.5%) yielded 15 isolates of methicillin-resistant staphylococci. The 15 isolates were identified as 6 species (Staphylococcus epidermidis, S lentus, S saprophyticus, S xylosus, S sciuri, and S haemolyticus). However, methicillin-resistant S aureus was seldom isolated. Each isolate contained the mecA gene and had a high resistance to beta-lactam antibiotics. Some isolates also were resistant to other antibiotics such as erythromycin and kanamycin. CONCLUSIONS AND CLINICAL RELEVANCE: Methicillin-resistant coagulase-negative staphylococci that were highly resistant to various antibiotics were isolated from apparently healthy horses in Japan. These organisms must be considered a potential threat to horses and veterinarians who care for them.     

Microbial Safety of Chickens Raised Without Antibiotics

The purpose of the current study was to verify whether there was any validity to the claim that consumers could reduce their exposure to antibiotic-resistant bacteria by purchasing poultry products that were produced without antibiotics. Rinse samples were taken from whole carcasses from chickens grown in small flocks and marketed as antibiotic-free. Salmonella bacteria were isolated from 18.7% of all the carcasses sampled. Campylobacter bacteria were found on 96.0% of the carcasses tested. More than two-thirds (69.4%) of the Salmonella isolates were resistant to at least 1 antibiotic. The antibiotic to which the Salmonella isolates were most commonly resistant was trimethoprim-sulfa, with almost two-thirds (62.9%) of the isolates being resistant to it. Almost three-fourths (73.4%) of the Campylobacter isolates were resistant to at least 1 antibiotic. The most common antibiotic to which Campylobacter isolates were resistant was tetracycline, with almost three-fourths (72.7%) of all Campylobacter isolates being resistant to it.     

Antimicrobial Resistance in Some Gram‐Negative Bacteria Isolated from the Bovine Ejaculate

The bacterial load and degree of antibiotic resistance present in untreated and antibiotic‐treated semen samples were investigated in five bulls standing at a cattle‐breeding centre. Bacterial load was determined by colony counts from semen samples cultured on brain heart infusion and nutrient agar plates. Antibiotic resistance in these bacteria was assessed by measuring the diameter of bacterial growth inhibition zones around discs containing different concentrations of antibiotics. Representative antibiotic‐resistant bacterial isolates were selected for identification. Untreated semen contained few culturable bacteria, and all were completely sensitive to gentamycin, spectinomycin and lincomycin: six of the isolates showed some resistance to tylosin. In semen to which antibiotics had been added as part of the routine production process, two isolates were sensitive to all of the antibiotics tested, and the remainder were resistant to all. Resistant Gram‐negative isolates that were identified included Pseudomonas and Stenotrophomonas spp. both in the class Gammaproteobacteria and a Sphingomonas sp. which is in the class Alphaproteobacteria.     

The Bacteria Isolated from the Skin of 20 Horses at a Veterinary Teaching Hospital

The objective of this study was to isolate bacteria on the skin of the proximal to distal equine limb to guide the practitioner in the selection of prophylactic antimicrobial protocols. This prospective study involved 20 client-owned horses that were admitted to the Veterinary Teaching Hospital for routine elective surgery. Each horse spent between 12 and 36 hours at our hospital before sampling. Samples were collected from the skin of the left mid-thorax and the dorsal aspect of nine joints on the left side of each horse: front and hind coffin and fetlock joints, carpi, elbows, shoulders, hocks, and stifles. Samples were cultured aerobically and speciated when possible. When evaluating bacterial composition by location, a 40% difference was considered clinically significant. When comparing proximal sites above the fetlock to distal sites, the odds of isolating gram-positive bacteria were 1.23 times (P = .0124) higher at proximal sites; the odds of isolating coliform bacteria were 1.32 times (P = .023) higher at distal sites; and the odds of isolating a common septic arthritis pathogen were 1.16 times (P = .018) higher at distal sites. Coagulase-positive Staphylococcus was not isolated in this study. All comparisons between sites and between the proximal and distal limb were <40%, and thus were not considered clinically significant. No coagulase-positive Staphylococcus was isolated from any of the 200 sites in this study, suggesting that iatrogenic infections by that organism may not be because of preexisting flora. These data suggest that antibiotic prophylaxis targeting preexisting normal flora should be similar regardless of the area of interest on the limb.