Multidrug-Resistant ESBL/AmpC-Producing Klebsiella pneumoniae Isolated from Healthy Thoroughbred Racehorses in Japan

Review of Pseudomonas aeruginosa and Klebsiella pneumoniae as venereal pathogens in horses

Three bacteria extensively acknowledged as venereal pathogens with the potential to induce endometritis include Taylorella equigenitalis, the causative agent of contagious equine metritis (CEM), specific strains of Pseudomonas aeruginosa, and certain capsule types of Klebsiella pneumoniae. The United Kingdom's Horserace Betting Levy Board recommends pre-breeding screening for these bacteria in their International Codes of Practice and >20 000 samples are tested per annum in the United Kingdom alone. While the pathogenesis and regulatory importance of CEM are well established, an evaluation of the literature pertaining to venereal transmission of P. aeruginosa and K. pneumoniae was lacking. The aim of this review was to evaluate published literature and determine the significance of P. aeruginosa and K. pneumoniae as venereal pathogens in horses. Literature definitively demonstrating venereal transmission was not available. Instead, application of molecular typing methods suggested that common environmental sources of contamination, such as water, or fomites be considered as modes of transmission. The presence of organisms with pathogenic potential on a horse's external genitalia did not predict venereal transmission with resultant endometritis and reduced fertility. These findings may prompt further investigation using molecular technologies to confirm or exclude venereal spread and investigation of alternative mechanisms of transmission are indicated.

Antimicrobial Resistance in Equines: A Growing Threat to Horse Health and Beyond-A Comprehensive Review

The equine industry holds substantial economic importance not only in the USA but worldwide. The occurrence of various infectious bacterial diseases in horses can lead to severe health issues, economic losses, and restrictions on horse movement and trade. Effective management and control of these diseases are therefore crucial for the growth and sustainability of the equine industry. While antibiotics constitute the primary treatment strategy for any bacterial infections in horses, developing resistance to clinically important antibiotics poses significant challenges to equine health and welfare. The adverse effects of antimicrobial overuse and the escalating threat of resistance underscore the critical importance of antimicrobial stewardship within the equine industry. There is limited information on the epidemiology of antimicrobial-resistant bacterial infections in horses. In this comprehensive review, we focus on the history and types of antimicrobials used in horses and provide recommendations for combating drug-resistant bacterial infections in horses. This review also highlights the epidemiology of antimicrobial resistance (AMR) in horses, emphasizing the public health significance and transmission dynamics between horses and other animals within a One Health framework. By fostering responsible practices and innovative control measures, we can better help the equine industry combat the pressing threat of AMR and thus safeguard equine as well as public health.

Epidemiological, Virulence, and Antibiotic Resistance Analysis of Klebsiella pneumoniae, a Major Source of Threat to Livestock and Poultry in Some Regions of Xinjiang, China

Klebsiella pneumoniae (K. pneumoniae) is recognized as a zoonotic pathogen with an increasing threat to livestock and poultry. However, research on K. pneumoniae of animal origin remains limited. To address the gap, a comprehensive investigation was carried out by collecting a total of 311 samples from the farms of four animal species (dairy cow, chicken, sheep, and pig) in selected areas of Xinjiang, China. Isolates were identified by khe gene amplification and 16S rRNA gene sequencing. Genotyping of K. pneumonia isolates was performed using wzi typing and multilocus sequence typing (MLST). PCR was employed to identify virulence and resistance genes. An antibiotic susceptibility test was conducted using the Kirby-Bauer method. The findings revealed an isolation of 62 K. pneumoniae strains, with an average isolation rate of 19.94%, with the highest proportion originating from cattle sources (33.33%). Over 85.00% of these isolates harbored six virulence genes (wabG, uge, fimH, markD, entB, and ureA); while more than 75.00% of isolates possessed four resistance genes (blaTEM, blaSHV, oqxA, and gyrA). All isolates exhibited complete resistance to ampicillin and demonstrated substantial resistance to sulfisoxazole, amoxicillin/clavulanic acid, and enrofloxacin, with an antibiotic resistance rate of more than 50%. Furthermore, 48.39% (30/62) of isolates were classified as multidrug-resistant (MDR) strains, with a significantly higher isolation rate observed in the swine farms (66.67%) compared to other farms. Genetic characterization revealed the classification of the 62 isolates into 30 distinct wzi allele types or 35 different sequence types (STs). Notably, we identified K. pneumoniae strains of dairy and swine origin belonging to the same ST42 and wzi33-KL64 types, as well as strains of dairy and chicken origin belonging to the same wzi31-KL31-K31 type. These findings emphasize the widespread occurrence of drug-resistant K. pneumoniae across diverse animal sources in Xinjiang, underscoring the high prevalence of multidrug resistance. Additionally, our results suggest the potential for animal-to-animal transmission of K. pneumoniae and there was a correlation between virulence genes and antibiotic resistance genes. Moreover, the current study provides valuable data on the prevalence, antibiotic resistance, and genetic diversity of K. pneumoniae originating from diverse animal sources in Xinjiang, China.

Antimicrobial Resistance and Extended-Spectrum Beta-Lactamase Genes in Enterobacterales, Pseudomonas and Acinetobacter Isolates from the Uterus of Healthy Mares

Antibiotic-resistant bacteria are a growing concern for human and animal health. The objective of this study was to determine the antimicrobial resistance and extended-spectrum beta-lactamase genes in Enterobacterales, Pseudomonas spp. and Acinetobacter spp. isolates from the uterus of healthy mares. For this purpose, 21 mares were swabbed for samples, which were later seeded on blood agar and MacConkey agar. The isolates were identified using MALDI-TOF and the antimicrobial susceptibility test was performed using the Kirby-Bauer technique. To characterize the resistance genes, a polymerase chain reaction (PCR) scheme was performed. Of the isolates identified as Gram-negative, 68.8% were Enterobacterales, represented by E. coli, Enterobacter cloacae, Citrobacter spp., and Klebsiella pneumoniae; 28.1% belonged to the genus Acinetobacter spp.; and 3.1% to Pseudomonas aeruginosa. A 9.3% of the isolates were multidrug-resistant (MDR), presenting resistance to antibiotics from three different classes, while 18.8% presented resistance to two or more classes of different antibiotics. The diversity of three genes that code for ESBL (blaTEM, blaCTX-M and blaSHV) was detected in 12.5% of the strains. The most frequent was blaSHV, while blaTEM and blaCTX-M were present in Citrobacter spp. and Klebsiella pneumoniae. These results are an alarm call for veterinarians and their environment and suggest taking measures to prevent the spread of these microorganisms.

Equine Gram-Negative Oral Microbiota: An Antimicrobial Resistances Watcher?

Horses are considered as reservoirs of multidrug resistant bacteria that can be spread through the environment and possibly to humans. The aim of this study was to characterize the oral Gram-negative microbiota of healthy horses and evaluate their antimicrobial susceptibility profile in a One Health approach. For this purpose, samples were collected from the gingival margin of healthy horses, free of antimicrobial therapy, cultured in selective mediums, identified, and tested for antimicrobial susceptibility. Fifty-five Gram-negative isolates were identified, with 89.5% being zoonotic and 62% affecting humans, which were also found commonly in the environment. Forty-eight isolates (96%) were MDR. The phenotypic resistance presented as higher to macrolides (81.8%), β-lactams (55.4%), and quinolones (50%), and lower to sulfonamides (27.3%), tetracyclines, and amphenicols (both with 30.9%). In total, 51.5% of the isolates presented resistance to carbapenems. In addition to being the first report on the commensal oral microbiota of horses and respective susceptibility profile, this study highlights the horse as a valuable sentinel that can control the evolution and transmission of multidrug-resistant bacteria between the "One Health triad" since it is in contact with humans, other animals, and the environment, in different geographic locations.

Phenotypic and molecular characterization of extended-spectrum β-lactamase/AmpC- and carbapenemase-producing Klebsiella pneumoniae in Iran

BACKGROUND

The objective of the current study is to evaluate the phenotypic and molecular characterization of ESBL/AmpC- and carbapenemase-producing K. pneumoniae isolates in Iran.

METHODS

From October 2018 until the end of April 2020, different clinical samples were collected and K. pneumoniae isolates were identified using conventional biochemical tests and PCR assay. Antibiotic susceptibility pattern was determined using the Kirby-Bauer disk diffusion method. Modified Hedge Test (MHT) was applied to the identification of carbapenemase-producing K. pneumoniae. ESBL and AmpC-producing K. pneumoniae were detected using Double Disc Test (DDT) and Disc Potentiation Test (DPT), respectively. The presence of carbapenemase, ESBL, and AmpC encoding genes was screened by Polymerase Chain Reaction (PCR) assay.

RESULTS

A total of 100 K. pneumoniae isolates were collected. K. pneumoniae isolates had the highest resistance rate to cefazolin (66%) and cefotaxime (66%). Meropenem and amikacin with sensitivity rates of 76% and 69% were the most effective antimicrobial agents on K. pneumoniae isolates. It was found that 12 (12%), 27 (27%), and 9 (9%) K. pneumoniae isolates were positive in MHT, DDT, and DPT tests, respectively. Among the carbapenemase-encoding genes, bla_OXA-48 (24%) and bla_IMP (13%) genes had the highest frequency, while bla_KPC and bla_GIM genes were not detected among K. pneumoniae isolates. bla_TEM (48%) and bla_CMY (8%) genes had the highest frequency among ESBL and AmpC β-lactamase-encoding genes, respectively.

CONCLUSIONS

It is vital to adopt effective control strategies for K. pneumoniae infections and ensure rapid identification of antibiotic resistance profile.

The Public Health Burden of Virulent Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae Strains Isolated from Diseased Horses

Background: Klebsiella pneumoniae has been associated with both nosocomial and community-acquired infections with mounting public health concern throughout the world. The purpose of this study was to investigate the burden of virulent extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae among diarrheic horses or those with respiratory illness to underscore the public health implication of such strains. Materials and Methods: Rectal and nasal swabs were gathered from 100 diseased horses (50 diarrheic and 50 with respiratory illness). The collected swabs were processed for isolation of ESBL-producing K. pneumoniae using a selective medium followed by phenotypic and molecular identification of the isolates. All ESBL-producing K. pneumoniae strains were investigated for six virulence genes (type 3 fimbrial adhesin [mrkD], enterobactin [entB], regulator of mucoid phenotype A [rmpA], Klebsiella ferric iron uptake [kfu], mucoviscosity-associated gene A [magA], and type 2 capsular polysaccharide [K2]). Results: Of the 100 examined animals, ESBL-producing K. pneumoniae was recovered from 13 (13%), with isolation rates in horses suffering from diarrhea and respiratory illness being 20% and 6%, respectively. Among the obtained isolates, bla TEM and bla SHV were found in all strains (100%) followed by bla CTX-M in 92.3%, while none of the isolates had bla OXA. In addition, 13 ESBL-producing K. pneumoniae strains exhibited a multidrug resistance (MDR) pattern. Regarding the occurrence of virulence genes among the isolates, mrkD (100%) and entB (100%) were the most predominant virulence genes followed by rmpA (76.9%) and kfu (46.2%). On the contrary, magA and K2 were negative in all ESBL-producing strains. Furthermore, this work provides four K. pneumoniae mrkD partial sequences that displayed high genetic relatedness with those obtained from human to clarify the public health burden of such isolates. Conclusion: The occurrence of virulent ESBL-producing K. pneumoniae among diseased horses highlights the potential role of this animal in the epidemiology of such virulent and antimicrobial-resistant strains, which may have great public health threat.

Determination of extended-spectrum β-lactamase-producing Klebsiella pneumoniae isolated from horses with respiratory manifestation

Background and Aim:

The World Health Organization considers multidrug-resistant (MDR) Klebsiella pneumoniae a major global threat. Horses harbor commensal isolates of this bacterial species and potentially serve as reservoirs for human MDR bacteria. This study investigated antimicrobial resistance in horses caused by extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae.

Materials and Methods:

One hundred fifty-nine nasal swab samples were collected from horses with respiratory distress not treated with cefotaxime and erythromycin. Biochemical and serological identification was performed on all samples. Polymerase chain reaction (PCR) was used to detect 16S-23S ITS, mucoviscosity-associated gene (magA), uridine diphosphate galacturonate 4-epimerase gene (uge), and iron uptake system gene (kfu), bla_TEM, bla_SHV, and bla_CTX genes. Sequence analysis and phylogenetic relatedness of randomly selected K. pneumoniae isolates carrying the bla_TEM gene were performed.

Results:

Ten isolates of Klebsiella spp. were obtained from 159 samples, with an incidence of 6.28% (10 of 159). Based on biochemical and serological identification, K. pneumoniae was detected in 4.4% (7 of 159) of the samples. Using PCR, all tested K. pneumoniae isolates (n=7) carried the 16S-23S ITS gene. By contrast, no isolates carried magA, uge, and kfu genes. The bla_TEM gene was detected in all test isolates. Moreover, all isolates did not harbor the bla_SHV or bla_CTX gene. Sequence analysis and phylogenetic relatedness reported that the maximum likelihood unrooted tree generated indicated the clustering of the test isolate with the other Gram-negative isolate bla_TEM. Finally, the sequence distance of the bla_TEM gene of the test isolate (generated by Lasergene) showed an identity range of 98.4-100% with the bla_TEM gene of the different test isolates.

Conclusion:

The misuse of antimicrobials and insufficient veterinary services might help generate a population of ESBL-producing K. pneumoniae in equines and humans, representing a public health risk.

Duplication of blaCTX-M-1 and a class 1 integron on the chromosome enhances antimicrobial resistance in Escherichia coli isolated from racehorses in Japan

OBJECTIVES

Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae have become a cause for great concern. Although some studies have reported the prevalence of ESBL-producing bacteria and ESBL-encoding genes in horses worldwide, the genetic structure surrounding the ESBL gene has not been analysed in detail. In the present study, we isolated two ESBL-producing Escherichia coli strains from diseased racehorses in Japan and demonstrated the mechanisms underlying the acquisition of their antimicrobial resistance (AMR) genes.

METHODS

Two ESBL-producing E. coli strains (E148 and E189) were isolated from the heart and liver of horses with endocarditis and sepsis in 2014 and 2016, respectively, in Japan. Complete genomic sequences of the two strains were analysed using a PacBio RSII sequencer. Antimicrobial susceptibility testing was performed by the agar dilution method.

RESULTS

The two isolates possessed a chromosomal AMR gene cluster containing bla_CTX-M-1 that was similar to the pEQ1 plasmid found in E. coli isolated from a racehorse in the Czech Republic. In one of the two strains, tandem duplication of the 16-kb region containing bla_CTX-M-1 and a class 1 integron, which occurred via IS26-mediated recombination, increased minimum inhibitory concentrations (MICs) associated with the duplicated AMR genes.

CONCLUSION

Chromosomal bla_CTX-M-1 possibly derived from the pEQ1 or pEQ1-like plasmid was found in Japanese equine E. coli isolates. In Japanese strains, many AMR genes containing bla_CTX-M-1 and the class 1 integron are highly accumulated in one region on the chromosome, and the AMR of E. coli was enhanced via the IS26-mediated duplication of the AMR gene cluster.

Antimicrobial resistance profiles and phylogenetic groups of Escherichia coli isolated from healthy Thoroughbred racehorses in Japan

In this study, we investigated the occurrence of antimicrobial resistance in commensal Escherichia coli isolated from healthy Thoroughbred (TB) racehorses in Japan. A total of 212 fecal samples were individually collected from TB racehorses from March 2017 to August 2018 at Japan Racing Association training centers. E. coli was isolated by using selective agar media, deoxycholate-hydrogen sulfide-lactose (DHL) and eosin methylene blue (EMB). A total of 417 E. coli isolates were examined against 10 antimicrobial agents by using the broth microdilution method. The 417 E. coli isolates were phylogenetically grouped using a multiplex polymerase chain reaction. The highest proportion of resistance was observed for streptomycin (30.9%, 129/417) followed by ampicillin (19.4%, 81/417), trimethoprim (15.8%, 66/417), tetracycline (8.4%, 35/417), chloramphenicol (2.6%, 11/417), kanamycin (1.2%, 5/417), nalidixic acid (0.5%, 2/417), cefazolin (0.2%, 1/417), colistin (0.2%, 1/417), and gentamycin (0%). Multidrug-resistant (MDR) E. coli was detected in 7.9% (33/417) of isolates. The proportions of resistance against ampicillin, streptomycin, kanamycin, and chloramphenicol and of multidrug-resistant phenotypes in E. coli belonging to phylogenetic group B2 were significantly higher than those of other groups. This study clarified the distribution of antimicrobial-resistant (AMR) E. coli in Japanese racehorses. A continuous monitoring program for antimicrobial resistance is required to control the spread of AMR bacteria in racehorses.

Antimicrobial-Resistant Enterococcus faecium and Enterococcus faecalis Isolated From Healthy Thoroughbred Racehorses in Japan

In this study, the occurrence of antimicrobial-resistant (AMR) enterococci was evaluated in Thoroughbred (TB) racehorses in Japan. Fecal samples were collected from 212 healthy TB racehorses at the Miho and Ritto Training Centers of the Japan Racing Association from March 2017 to August 2018. Isolation and identification were performed by enterococcus selective medium and confirmed to the species using MALDI-TOF MS. Enterococcus faecium and E. faecalis isolates were subjected to antimicrobial susceptibility test against 11 antimicrobials by minimum inhibitory concentration based on recommendation from Clinical and Laboratory Standards Institute guidelines. Among 583 enterococcus isolates, E. faecium and E. faecalis were identified for 48.2% (281/583) and 7.4% (43/583), respectively. One isolate that was representing E. faecium (153 isolates) and E. faecalis (31 isolates) from each sample was selected for antimicrobial susceptibility test. The highest rate of resistance for E. faecium isolates was observed against enrofloxacin (57.5%; 88/153), followed by streptomycin (32.0%; 49/153), kanamycin (18.3%; 28/153), gentamycin (5.9%; 9/153), erythromycin (5.9%; 9/153), and oxytetracycline (4.6%; 7/153). For E. faecium isolates, the highest resistance was observed against streptomycin (90.3%; 28/31), followed by kanamycin (41.9%; 13/31), gentamycin (29.0%; 9/31), lincomycin (9.7%; 3/31), oxytetracycline (6.5%; 2/31), erythromycin (6.5%; 2/31), tylosin (6.5%; 2/31), enrofloxacin (6.5%; 2/31), and chloramphenicol (3.2%; 1/31). The results indicated that enrofloxacin and aminoglycosides were highly resistant among tested antimicrobials. Continuous monitoring studies are useful to increase the awareness of the potential for AMR bacteria to arise from imprudent use of antimicrobials in TB racehorses in Japan.