Efficacy of antimicrobials in preventing resistance in solid organ transplant recipients:A systematic review of clinical trials

BACKGROUND In the absence of effective antimicrobials,transplant surgery is not viable,and antirejection immunosuppressants cannot be administered,as resistant infections compromise the life-saving goal of organ transplantation.AIM To evaluate the efficacy of antimicrobials in preventing resistance in solid organ transplant recipients.METHODS A systematic review was conducted using a search methodology consistent with the preferred reporting items for systematic reviews and meta-analyses.This review included randomized clinical trials that evaluated the efficacy of antimicrobial agents(prophylactic or therapeutic)aimed at preventing antimicrobial resistance.The search strategy involved analyzing multiple databases,including PubMed/MEDLINE,Web of Science,Embase,Scopus,and SciELO,as well as examining gray literature sources on Google Scholar.A comprehensive electronic database search was conducted from the databases’inception until May 2024,with no language restrictions.RESULTS After the final phase of the eligibility assessment,this systematic review ultimate-ly included 7 articles.A total of 2318 patients were studied.The most studied microorganisms were cytomegalovirus,although vancomycinresistant enterococci,Clostridioides difficile,and multidrug-resistant Enterobacterales were also analyzed.The antimicrobials used in the interventions were mainly maribavir,valganciclovir,gancic-lovir,and colistin-neomycin.Of concern,all clinical trials showed significant proportions of resistant microorga-nisms after the interventions,with no statistically significant differences between the groups(mean resistance 13.47%vs 14.39%),except for two studies that demonstrated greater efficacy of maribavir and valganciclovir(mean resistance 22.2%vs 41.1%in the control group;P<0.05).The total reported deaths in three clinical trials were 75,and there were 24 graft rejections in two studies.CONCLUSION All clinical trials reported significant proportions of antimicrobial-resistant microorganisms following interventions.More high-quality randomized clinical trials are needed to corroborate these results.

Core and variable antimicrobial resistance genes in the gut microbiomes of Chinese and European pigs

Monitoring the prevalence of antimicrobial resistance genes(ARGs)is vital for addressing the global crisis of antibiotic-resistant bacterial infections.Despite its importance,the characterization of ARGs and microbiome structures,as well as the identification of indicators for routine ARG monitoring in pig farms,are still lacking,particularly concerning variations in antimicrobial exposure in different countries or regions.Here,metagenomics and random forest machine learning were used to elucidate the ARG profiles,microbiome structures,and ARG contamination indicators in pig manure under different antimicrobial pressures between China and Europe.Results showed that Chinese pigs exposed to high-level antimicrobials exhibited higher total and plasmid-mediated ARG abundances compared to those in European pigs(P<0.05).ANT(6)-Ib,APH(3')-IIIa,and tet(40)were identified as shared core ARGs between the two pig populations.Furthermore,the core ARGs identified in pig populations were correlated with those found in human populations within the same geographical regions.Lactobacillus and Prevotella were identified as the dominant genera in the core microbiomes of Chinese and European pigs,respectively.Forty ARG markers and 43 biomarkers were able to differentiate between the Chinese and European pig manure samples with accuracies of 100%and 98.7%,respectively.Indicators for assessing ARG contamination in Chinese and European pigs also achieved high accuracy(r=0.72-0.88).Escherichia flexneri in both Chinese and European pig populations carried between 21 and 37 ARGs.The results of this study emphasize the importance of global collaboration in reducing antimicrobial resistance risk and provide validated indicators for evaluating the risk of ARG contamination in pig farms.

Genetic characterization of antimicrobial resistance in Staphylococcus aureus isolated from bovine mastitis cases in Northwest China

Staphylococcus aureus is the most common etiological pathogen of bovine mastitis. The resistant strains make the disease difficult to cure. The aim of this study was to characterize the genetic nature of the antimicrobial resistance in S. aureus cultured from bovine mastitis in Northwest China in 2014. A total of 44 S. aureus were isolated for antimicrobial resistance and resistance-related genes. Antimicrobial resistance was determined by disc diffusion and the corresponding resistance genes were detected by PCR. Phenotype indicated that S. aureus isolates were resistant to penicillin （84.09%）, erythromycin （20.45%）, tetracycline （15.91%）, gentamicin （9.09%）, tobramycin （6.82%）, kanamycin （6.82%） and methicillin （2.27%）. 9.09% of the S. aureus isolates were classified as multidrug resistant. In addition, genotypes showed that the isolates were resistant to rifampicin （100%, rpoB）, penicillin （95.45%, blaZ）, tetracycline （22.73%, tetK, tetM, alone or in combination）, erythromycin （22.73%, ermB or ermC）, gentamicin/tobramycin/kanamycin （2.27%, aacA-aphD）, methicillin （2.27%, mecA） and vancomycin （2.27%, vanA）. Resistance to tetracycline was attributed to the genes tetK and tetM （r=0.558, P〈0.001）. This study noted high-level geno- and phenotypic antimicrobial resistance in S. aureus isolates from bovine mastitis cases in Northwest China.

Genetic Diversity, Antimicrobial Resistance, and Virulence Genes of Aeromonas Isolates from Clinical Patients, Tap Water Systems, and Food

Objective This study aimed to evaluate the genetic diversity,virulence,and antimicrobial resistance of Aeromonas isolates from clinical patients,tap water systems,and food.Methods Ninety Aeromonas isolates were obtained from Ma’anshan,Anhui province,China,and subjected to multi-locus sequence typing(MLST)with six housekeeping genes.Their taxonomy was investigated using concatenated gyr B-cpn60 sequences,while their resistance to 12 antibiotics was evaluated.Ten putative virulence factors and several resistance genes were identified by PCR and sequencing.Results The 90 Aeromonas isolates were divided into 84 sequence types,80 of which were novel,indicating high genetic diversity.The Aeromonas isolates were classified into eight different species.PCR assays identified virulence genes in the isolates,with the enterotoxin and hemolysin genes act,aer A,alt,and ast found in 47(52.2%),13(14.4%),22(24.4%),and 12(13.3%)of the isolates,respectively.The majority of the isolates(≥90%)were susceptible to aztreonam,imipenem,cefepime,chloramphenicol,gentamicin,tetracycline,and ciprofloxacin.However,several resistance genes were detected in the isolates,as well as a new mcr-3 variant.Conclusions Sequence type,virulence properties,and antibiotic resistance vary in Aeromonas isolates from clinical patients,tap water systems,and food.

Detection of antimicrobial resistance and virulence-related genes in Streptococcus uberis and Streptococcus parauberis isolated from clinical bovine mastitis cases in northwestern China

The objectives of this study were to investigate antimicrobial resistance of Streptococcus uberis and Streptococcus parauberis isolated from cows with bovine clinical mastitis in China and to examine the distribution of resistance-and virulence-related gene patterns.Antimicrobial susceptibility was determined by the E-test.Genes encoding antimicrobial resistance and invasiveness factors were examined by PCR.A total of 27 strains were obtained from 326 mastitis milk samples.Streptococcus parauberis isolates(n=11)showed high resistance to erythromycin(90.9%),followed by tetracycline(45.5%),chloramphenicol(36.4%)and clindamycin(27.3%).Streptococcus uberis isolates(n=16)were highly resistant to tetracycline(81.3%)and clindamycin(62.5%).Both species were susceptible to ampicillin.The most prevalent resistance gene in S.uberis was tetM(80.0%),followed by blaZ(62.5%)and ermB(62.5%).However,tetM,blaZ,and ermB genes were only found in 27.3,45.5,and 27.3%,respectively,of S.parauberis.In addition,all of the isolates carried at least one selected virulence-related gene.The most prevalent virulence-associated gene pattern in the current study was sua+pauA/skc+gapC+hasC detected in 22.2%of the strains.One S.uberis strain carried 7 virulence-associated genes and belonged to the sua+pauA/skc+gapC+cfu+hasA+hasB+hasC pattern.More than 59.3%of analysed strains carried 4 to 7 virulence-related genes.Our findings demonstrated that S.parauberis and S.uberis isolated from clinical bovine mastitis cases in China exhibited diverse molecular ecology,and that the strains were highly resistant to antibiotics commonly used in the dairy cow industry.The data obtained in the current study contribute to a better understanding of the pathogenesis of bacteria in mastitis caused by these pathogens,and the findings are relevant to the development of multivalent vaccines and targeted prevention procedures.

Towards a better understanding of antimicrobial resistance dissemination:what can be learnt from studying model conjugative plasmids?

Bacteria can evolve rapidly by acquiring new traits such as virulence,metabolic properties,and most importantly,antimicrobial resistance,through horizontal gene transfer(HGT).Multidrug resistance in bacteria,especially in Gram-negative organisms,has become a global public health threat often through the spread of mobile genetic elements.Conjugation represents a major form of HGT and involves the transfer of DNA from a donor bacterium to a recipient by direct contact.Conjugative plasmids,a major vehicle for the dissemination of antimicrobial resistance,are selfish elements capable of mediating their own transmission through conjugation.To spread to and survive in a new bacterial host,conjugative plasmids have evolved mechanisms to circumvent both host defense systems and compete with co-resident plasmids.Such mechanisms have mostly been studied in model plasmids such as the F plasmid,rather than in conjugative plasmids that confer antimicrobial resistance(AMR)in important human pathogens.A better understanding of these mechanisms is crucial for predicting the flow of antimicrobial resistance-conferring conjugative plasmids among bacterial populations and guiding the rational design of strategies to halt the spread of antimicrobial resistance.Here,we review mechanisms employed by conjugative plasmids that promote their transmission and establishment in Gram-negative bacteria,by following the life cycle of conjugative plasmids.

Seafood as a Reservoir of Gram-negative Bacteria Carrying Integrons and Antimicrobial Resistance Genes in Japan

PCR and DNA sequencing were used to screen and characterize integrons and resistance genes in Gram-negative bacteria isolated from seafood products in Japan.A total of 215 Gram-negative bacteria were isolated from local and imported seafood samples collected from retail markets in Hiroshima Prefecture.Class 1 integrons containing gene cassettes encoding resistance to trimethoprim

Analysis on Antimicrobial Resistance of Clinical Bacteria Isolated from County Hospitals and a Teaching Hospital

The distinction of antimicrobial resistance of clinical bacteria isolated from county hospitals and a teaching hospital was investigated. Disc diffusion test was used to study the antimicrobial resistance of isolates collected from county hospitals and a teaching hospital. The data was analyzed by WHONET5 and SPSS statistic software. A total of 655 strains and 1682 strains were collected from county hospitals and a teaching hospital, respectively, in the year of 2003. The top ten pathogens were Coagulase negative staphylococci （CNS）, E. coil, Klebsiella spp. , S. areus, P. aeruginosa, Enterococcus spp. , Enterobacter spp. , otherwise Salmonella spp. , Proteus spp. , Shigella spp. in county hospitals and Streptococcus spp. , Acinetobacter spp. , X. maltophilia in the teaching hospital. The prevalence of multi-drug resistant bacteria was 5 % （4/86） of methicillin-resistant S. areus （MRSA）, 12 % （16/133） and 15.8 % （9/57） of extended-spectrum β-lactamases producing strains of E. coil and Klebsiella spp. , respectively, in county hospitals. All of the three rates were lower than that in the teaching hospital and the difference was statistically significant （P〈0. 01）. However, the incidence of methicillin-resistant CNS （MRCNS） reached to 70 % （109/156） in the two classes of hospitals. Generally, the antimicrobial resistant rates in the county hospitals were lower than those in the teaching hospital, except the resistant rates of ciprofloxacin, erythromycin, clindamycin, SMZco which were similar in the two classes of hospitals. There were differences between county hospitals and the teaching hospital in the distribution of clinical isolates and prevalence of antimicrobial resistance. It was the basis of rational use of antimicrobial agents to monitor antimicrobial resistance by each hospital.

Antimicrobial Resistance,Virulence Profile,and Molecular Characterization of Listeria monocytogenes Isolated from Ready-to-eat Food in China,2013-2014

We aimed to investigate the potential pathogenic profile and antibiotic resistance of Listeria monocytogenes isolated from ready-to-eat food in China.Antimicrobial resistance was determined by broth microdilution following the Clinical and Laboratory Standards Institute protocol Molecular serotyping,virulence,and resistance genes were identified using PCR.Multi-locus

Comparative Study of the Genetic Diversity, Antimicrobial Resistance, and Pathogenicity of Aeromonas Isolates from Clinical Patients and Healthy Individuals

Objective This study was performed to compare the genetic diversity,virulence,and antimicrobial resistance of Aeromonas strains isolated from patients and healthy individuals.Methods A total of 38 clinical strains and 19 strains from healthy individuals were isolated from the samples collected in Ma’anshan City,Anhui Province.Their taxonomy was investigated using concatenated gyrB-cpn60 sequences,and their resistance to 12 antibiotics was evaluated.The pathogenicity of these strains was examined through beta-hemolysis,protease activity,and virulence gene assays.Results The 57 Aeromonas strains were divided into 55 sequence types.Of these types,21 were novel,suggesting that their genetic diversity was high.These Aeromonas isolates could be divided into 7 species,and the positive rates of beta-hemolysis and protease activity were 49.1%and 73.7%,respectively.The detection rate of clinical patients in terms of beta-hemolysis and protease activity was higher than that of healthy individuals.Among the four most common Aeromonas strains,A.dhakensis had the highest detection rate of virulence genes.The multidrug resistance rate of the clinical isolates was much higher than that of the strains isolated from healthy individuals.Conclusions The taxonomy,virulence properties,and antibiotic resistance of Aeromonas isolates from patients differ from those of the isolates from healthy individuals.

Antimicrobial resistance and underlying mechanisms in Staphylococcus aureus isolates

Objective: To investigate the antimicrobial susceptibility of 97 clinical Staphylococcus aureus(S. aureus) strains against 14 antimicrobials and corresponding resistance mechanisms.Methods: The antimicrobial susceptibility of the isolates was determined using a disk diffusion method and antimicrobial resistance genes were screened by polymerase chain reaction. Mutations responsible for ciprofloxacin and rifampicin resistance were investigated by polymerase chain reaction and DNA sequencing.Results: All isolates were found to be susceptible to vancomycin. Various rates of resistance to penicillin(83.5%), ampicillin(77.3%), erythromycin(63.9%), tetracycline(16.5%), amoxicillin/clavulanic acid(16.5%), ciprofloxacin(15.5%), trimethoprim/sulfamethoxazole(15.5%), oxacillin(13.4%), fusidic acid(12.4%), rifampin(6.2%), clindamycin(6.2%), gentamicin(6.2%) and mupirocin(5.2%) were determined. In addition,different combinations of resistance genes were identified among resistant isolates.Ciprofloxacin resistant isolates had mutations in codon 84(Ser84 Leu) and 106(Gly106 Asp) in the gyr A gene. Mutations in grl A were mostly related to Ser80 Phe substitution. Leu466 Ser mutation in the rpo B gene was detected in all rifampin resistant isolates. All methicillin resistant S. aureus isolates were SCCmec type V.Conclusions: In conclusion, it was determined that the isolates were resistant to different classes of antimicrobials at varying rates and resistance was mediated by different genetic mechanisms. Therefore, continuous monitoring of resistance in S. aureus strains is necessary to control their resistance for clinically important antimicrobials.

Impact of Antimicrobial Stewardship Programs on Antibiotic Use and Drug Resistance:Analysis of Data from Maternal and Child Health Care Hospitals in Hubei Province,China

ObjectiveTo evaluate the impact of Antimicrobial Stewardship Programs(ASPs)on antibiotic use and drug resistance.MethodsThis was a retrospective,multicenter,management intervention study.The data from 85 maternity hospitals(maternal and child health care hospitals)in Hubei province from 2012 to 2019 were collected.The indicators related to antimicrobial drug use included the utilization rate of different grades of antimicrobial drugs,the intensity of antimicrobial agent use,the rational use of prophylactic antimicrobial agents before class I surgical incision,and pathogenic detection and consultation rates before antimicrobial drug use.ResultsSince the implementation,the purchase of antimicrobial agents in hospitals has been maintained within the prescribed range,and the defined daily dose system(DDDs)of antimicrobial agents has been reduced,prophylactic use and accurate treatment of antimicrobial agents related to class I surgical incision have been more reasonable.With the implementation of ASPs,the detection rate of imipenem-resistant Acinetobacter baumannii,cefotaxime-resistant Escherichia coli,and methicillin-resistant Staphylococcus aureus has been decreased in China from national bacterial resistance surveillance data.ConclusionASPs have positive effects on antibiotic use and drug resistance in 85 maternity hospitals(maternal and child health care hospitals).

A New High-throughput Real-time PCR Assay for the Screening of Multiple Antimicrobial Resistance Genes in Broiler Fecal Samples from China

Objective Antimicrobial resistance(AMR)has become a global concern and is especially severe in China.To effectively and reliably provide AMR data,we developed a new high-throughput real-time PCR assay based on microfluidic dynamic technology,and screened multiple AMR genes in broiler fecal samples.Methods A high-throughput real-time PCR system with an new designed integrated fluidic circuit assay were performed AMR gene detection.A total of 273 broiler fecal samples collected from two geographically separated farms were screened AMR genes.Results The new assay with limits of detection ranging from 40.9 to 8,000 copies/reaction.The sensitivity rate,specificity rate,positive predictive value,negative predictive value and correct indices were 99.30%,98.08%,95.31%,99.79%,and 0.9755,respectively.Utilizing this assay,we demonstrate that AMR genes are widely spread,with positive detection rates ranging from 0 to 97.07%in 273 broiler fecal samples.bla CTX-M,bla TEM,mcr-1,fex A,cfr,optr A,and int I1 showed over 80%prevalence.The dissemination of AMR genes was distinct between the two farms.Conclusions We successfully established a new high-throughput real-time PCR assay applicable to AMR gene surveillance from fecal samples.The widespread existence of AMR genes detected in broiler farms highlights the current and severe problem of AMR.

Prevalence and antimicrobial resistance of non-typhoid Solmonella in military personnel,1988-2013

Objective:To describe the spanning 25 years data for the occurrence,magnitude,and trends regarding antimicrobial resistance of non-typhoidal Salmonella(NTS)isolated from non-immune travelers to Thailand participating in joint military operations.Methods:A total of 355 NTS isolates,obtained from 2052 fecal samples from US soldiers deployed for military maneuvers in Thailand during 1988-2013,were examined for NTS serogroup/serotypes and tested for antimicrobial susceptibility by disk diffusion to these 10 antibiotics:ampicillin,azithromycin(AZM),ciprofloxacin,colistin,gentamicin,kanamycin,nalidixic acid,streptomycin(STR),tetracycline(TET),and trimethoprim/sulfamethoxazole.Identified AZM-resistant NTS isolates were further evaluated for their minimal inhibitory concentration by the E-test method.Results:NTS infections accounted for 17.3%(355/2052),including11 serogroups and 50 different serotypes.The most prevalent serogroup was Salmonella group C2-C3(35.8%,127/355)followed by groups B(21.1%,75/355)and C1(18.6%,66/355).Identified serotypes included Salmonella hadar(n=60),Salmonella rissen(n=45),and Salmonella blockley(n=34).Among the predominate serogroups,antimicrobial resistance was consistently high against TET(76.9%,273/355)followed by STR(40.8%,145/355).One Salmonella senftenberg isolate demonstrated decreased ciprofloxacin susceptibility.Most isolates(94.6%)were resistant to one or more antimicrobials,and the most common multidrug resistance was TET-STR-nalidixic acid(11.5%,41/355).Conclusions:The prevalence of NTS serotypes and the growing magnitude of antibiotic resistant bacteria isolated from deployed US military in Thailand are documented from 1988-2013.This study demonstrates the antibiotic resistance profiles,highlighting the effectiveness of AZM that is a first-line treatment for travelers to Southeast Asia.AZM-resistant NTS isolates are periodically observed over a 25-year period.Hence,the ongoing surveillance and prevalence efforts are required to monitor NTS resistant strains causing further treatment failure.

Disease burden,antimicrobial resistance and molecular characterization of invasive group B Streptococcus among non-pregnant adults in Malaysia:A protocol study

and pili genes are also investigated.Methods:This multicentre,prospective,observational study is conducted in seven major tertiary hospitals in Malaysia among non-pregnant adults.Simultaneously,a retrospective study is conducted in the selected hospitals with similar approaches.GBS isolates are subjected to phenotyping,serotyping by multiplex PCR,antimicrobial susceptibility testing and PCR-detection of GBS virulence and pilus genes.Seven housekeeping genes are amplified and sequenced for multi-locus sequence typing.Discussion:Findings from the study may contribute to the management of clinical practice to diagnose and prevent GBS related diseases in a timely manner.Prudent use of antibiotics is encouraged by monitoring antimicrobial resistance.

Association between the Phenotypes and Genotypes of Antimicrobial Resistance in Haemophilus parasuis Isolates from Swine in Quang Binh and Thua Thien Hue Provinces, Vietnam

Haemophilus parasuis (H. parasuis) is one of the bacterial pathogens of great concern as it causes huge economic losses to the swine industry worldwide. One of the reasons why the control of H. parasuis has failed is the increase in antimicrobial resistance (AMR). The country of Vietnam has the second-largest pig production in Asia. However, there is still a lack of data about the AMR prevalence of H. parasuis in Vietnam.The purpose of this study is to investigate the prevalence of AMR and analyze the association between AMR and AMR genes (ARGs). The H. parasuis strains used in this research were isolated from swine in the Quang Binh and Thua Thien Hue Provinces, Central Vietnam, as reported in our previous study. All of the strains were tested for AMR against 25 antibacterial agents using the broth microdilution method and for the presence of ARGs using the polymerase chain reaction (PCR) method. The tested strains were shown to have a high frequency of resistance to trimethoprim/sulfamethoxazole (94.6%), followed by resistance to colistin, chloramphenicol, gentamicin, penicillin, lincomycin, and amoxicillin. The most prevalent ARGs in these strains were blaTEM-1 (94.6%), int (76.8%), gyrA (58.9%), and rmtD (50.0%). Cefuroxime, chloramphenicol, and tobramycin resistances were strongly correlated with the presence of the ARGs blaROB-1 (odds ratio (OR) = 26.3, 95% confidence interval (CI) 2.7–255.7, p = 0.002), catl (OR = 25.1, 95% CI 2.4–258.9, p = 0.004), and strB (OR = 23.5, 95% CI 2.6–212.6, p = 0.001), respectively.This study reveals for the first time the current situation of H. parasuis AMR in Central Vietnam, which is helpful for the clinical control of this disease, as well as for the development of policies and clinical practice guidelines to reduce AMR in swine production in Central Vietnam.

Response to Comment on "The role of wildlife (wild birds) in the global transmission of antimicrobial resistance genes"

DEAR EDITOR,Since our first identification of plasmid-mediated colistin resistance gene mcr-1 in 2015 （Liu et al., 2016）, it has been described in human clinics, domestic animals, foods, and the environment worldwide （Schwarz ＆ Johnson, 2016）. Although it is still rare, the emergence of mcr-I in wild animals is of great concern. We summarized two previous reports on mcr-1 in wild birds from Lithuania and Argentina to describe its emergence and characteristics in wildlife and highlight the potentially important role of wild animals, particularly birds, in its global transmission （Wang et al., 2017）. The first detection of mcr-1 in wildlife in Asia was identified in an extended-spectrum β- lactamase-producing Escherichia coil strain isolated from Eurasian coot （Fulica atra）,

Mobile phones in the orthopedic operating room: Microbial colonization and antimicrobial resistance

BACKGROUND Surgical site infections are a major cause of morbidity and mortality following orthopedic surgery.Recent efforts to identify sources of contamination in the operating rooms have implicated mobile phones.AIM To investigate microbial colonization on the mobile phones of health care professionals in the orthopedic operating room.METHODS We conducted a cross-sectional study involving culture and sensitivity analysis of swabs taken from the mobile phones of orthopedic and anesthesia attendings,residents,technicians and nurses working in the orthopedic operating rooms over a period of two months.Demographic and cell phone related factors were recorded using a questionnaire and the factors associated with contamination were analyzed.RESULTS Ninety-three of 100 mobile phones were contaminated.Species isolated were Coagulase-negative Staphylococcus(62%),Micrococcus(41%)and Bacillus(26%).The risk of contamination was increased with mobile covers and cracked screens and decreased by cell phone cleaning.CONCLUSION Mobile phones belonging to health care workers are frequently contaminated with pathogenic bacteria with the potential of transferring drug resistance to nosocomial pathogens.Studies investigating the relationship to surgical site infections need to be conducted.The concept of"mobile hygiene"involving the change of mobile covers,replacement of cracked screens or even wiping the phone with an alcohol swab could yield the cost-effective balance that contaminated cell phones deserve until they are established as a direct cause of surgical site infections.

Antimicrobial usage and resistance in beef production

Antimicrobials are critical to contemporary high-intensity beef production. Many different antimicrobials are approved for beef cattle, and are used judiciously for animal welfare, and controversially, to promote growth and feed efficiency. Antimicrobial administration provides a powerful selective pressure that acts on the microbial community, selecting for resistance gene determinants and antimicrobial-resistant bacteria resident in the bovine flora. The bovine microbiota includes many harmless bacteria, but also opportunistic pathogens that may acquire and propagate resistance genes within the microbial community via horizontal gene transfer. Antimicrobial-resistant bovine pathogens can also complicate the prevention and treatment of infectious diseases in beef feedlots,threatening the efficiency of the beef production system. Likewise, the transmission of antimicrobial resistance genes to bovine-associated human pathogens is a potential public health concern. This review outlines current antimicrobial use practices pertaining to beef production, and explores the frequency of antimicrobial resistance in major bovine pathogens. The effect of antimicrobials on the composition of the bovine microbiota is examined, as are the effects on the beef production resistome. Antimicrobial resistance is further explored within the context of the wider beef production continuum, with emphasis on antimicrobial resistance genes in the food chain, and risk to the human population.

Knowledge, Attitudes, and Practices of Antimicrobial Use and Resistance among Livestock Producers in Cambodia

The development of antimicrobial resistance (AMR) due to over or misuse of antibiotics/antimicrobials is a globally increasing public health concern. This study was conducted to assess the current knowledge, attitudes, and practices (KAP) of swine and poultry producers on antimicrobial use (AMU) and antimicrobial resistance (AMR). A total of 254 swine and poultry producers of 5 provinces in Cambodia were purposively surveyed using validated KAP questionnaires, a useful tool for promoting the rational use of antimicrobials in livestock. Collectively, this study found out that livestock producers in Cambodia have a low level of knowledge, neutral rather than positive attitudes, and employed poor practices on the AMU and AMR. Thus, there is a need to promote among producers the rational and responsible use of antimicrobials. Furthermore, public awareness of the AMR implications on public health can contribute to the prevention or reduction of AMU and AMR in Cambodia.