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In recent years, antimicrobial-resistant Pseudomonas aeruginosa strains have increased in the veterinary field. Therefore, phage therapy has received significant attention as an approach for overcoming antimicrobial resistance. In this context, we isolated and characterized four Pseudomonas bacteriophages. Phylogenetic analysis showed that the isolated phages are novel Myoviridae Pbunavirus PB1-like phages with OR12 belonging to a different clade compared with the other three. These phages had distinct lytic activity against 22 P. aeruginosa veterinary isolates. The phage cocktail composed from the PB1-like phages clearly inhibited the occurrence of the phage-resistant variant, suggesting that these phages could be useful in phage therapy.

Clostridioides difficile infections (CDIs) are predominantly a healthcare-associated illness in developed countries, with the majority of cases being elderly and hospitalize patients who used antibiotic therapy. Recently, the incidence of community-associated CDIs (CA-CDIs) in younger patients without a previous history of hospitalization or antibiotic treatment has been increasing globally. C. difficile is sometimes found in the intestine of many animals, such as pigs, calves, and dogs. Food products such as retail meat products and vegetables sometimes contain C. difficile. C. difficile has also been isolated from several environments such as compost manure, rivers, and soils. Yet, direct transmission of C. difficile from animals, food products, and environments to humans has not been proven, although these strains have similar molecular characteristics. Therefore, it has been suggested that there is a relationship between CA-CDIs and C. difficile from animals, food products, and the environment. To clarify the importance of the presence of C. difficile in several sources, characterization of C. difficile in these sources is required. However, the epidemiology of C. difficile in animals, food products, and the environment is not well studied in Japan. This review summarizes recent trends of CDIs and compares the molecular characteristics of C. difficile in Japanese animals, food products, and the environment. The prevalence trends of C. difficile in Japan are similar to those in the rest of the world. Therefore, I recommend using a One Health approach to CDI surveillance, monitoring, and control.

Manure compost has been thought of as a potential important route of transmission of antimicrobial-resistant bacteria (ARB) and antimicrobial resistance genes (ARGs) from livestock to humans. To clarify the abundance of ARB and ARGs, ARB and ARGs were quantitatively determined in tetracycline-resistant Escherichia coli (harboring the tetA gene)-spiked feces in simulated composts. In the simulated composts, the concentration of spiked E. coli decreased below the detection limit at day 7. The tetA gene remained in manure compost for 20 days, although the levels of the gene decreased. Next, to clarify the field conditions of manure compost in Japan, the quantities of tetracycline-resistant bacteria, tetracycline resistance genes, and residual tetracyclines were determined using field-manure-matured composts in livestock farms. Tetracycline-resistant bacteria were detected in 54.5% of tested matured compost (6/11 farms). The copy number of the tetA gene and the concentrations of residual tetracyclines in field manure compost were significantly correlated. These results suggest that the use of antimicrobials in livestock constitutes a selective pressure, not only in livestock feces but also in manure compost. The appropriate use of antimicrobials in livestock and treatment of manure compost are important for avoiding the spread of ARB and ARGs.

Flavophospholipol (FPL) is an antimicrobial feed additive that has been approved for use in livestock animals and has the potential to decrease horizontal dissemination of antimicrobial resistance genes. Since previous studies showed that FPL has an inhibitory effect on plasmid transfer, in vitro experiments have proven the efficacy of FPL in reducing the conjugative transfer of plasmids encoding the extended-spectrum β-lactamase (ESBL) and vanA genes. These are among the most important antimicrobial resistance loci known. ESBL-producing Escherichia coli and vancomycin-resistant Enterococcus faecalis (VRE) were exposed to several concentrations of FPL, and transfer frequency and plasmid curing activity were determined. FPL inhibited the conjugative transfer of plasmids harboring ESBL and vanA genes in a concentration-dependent manner in all strains. Further transfer experiments revealed that FPL could decrease or increase transfer frequency depending on plasmid type when transfer frequency was at low levels. The plasmid curing activity of FPL was also observed in ESBL-producing E. coli in a concentration-dependent manner, suggesting that they partially contribute to the inhibition of conjugative transfer. These results suggest that the use of FPL as a feed additive might decrease the dissemination of ESBL and vanA genes among livestock animals.

We investigated the prevalence of virulence factors and antimicrobial resistance among 67 Acinetobacter spp. isolates, consisting of 21 Acinetobacter baumannii and 46 non-baumannii Acinetobacter from companion animals. The PCR analysis showed that the most prevalent virulence gene was afa/draBC (29.9%), followed by papC (22.4%) and cvaC (20.9%). Antimicrobial susceptibility testing revealed that resistance to gentamicin (14.9%) and ciprofloxacin (11.9%) was relatively prevalent. Five gentamicin- and/or ciprofloxacin-resistant A. baumannii strains were assigned to ST25, ST149, ST164, ST203, and ST1198. All ciprofloxacin-resistant isolates harbored point mutations in gyrA and/or parC. This is the first preliminary monitoring of animal-origin Acinetobacter spp. in Japan.

The aim of the present study was to determine and compare the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and their molecular characteristics among veterinary staff in Sapporo in 2008 and 2016. We isolated MRSA from veterinarians (Vet; n = 91), veterinary technicians (VT; n = 113), and other staff members (n = 24) from 45 small animal hospitals (animal hospitals), as well as from surface swabs (n = 123) obtained from 37 animal hospitals, in 2016. MRSA was observed in 14 Vets (15%), 7 VTs (6%), 2 other staff members (8%), and 6 environmental samples (5%). The prevalence of MRSA among veterinary staff tended to decrease, in comparison to 2008. All the MRSA isolates were classified as CC5/SCCmecII, which is commonly observed in medical settings in Japan. Upon performing pulse-field gel electrophoresis, with SmaI and EagI, and clfB sequence typing, it was observed that 16 of the MRSA isolates from 2016 were highly similar to those obtained in 2008. This suggests that some MRSA isolates persisted throughout 8 years, although their origins remain unclear. The continuation of education and monitoring of MRSA is necessary for the prevention and control of infection in these settings.

Fluoroquinolone is widely used for the treatment of bacterial diseases, and the emergence of quinolone resistance has become a serious concern in recent years, owing to an increase and inappropriate use of antimicrobials. Here, we attempted to understand the differences in the emergence frequency of quinolone-resistant bacterial variants in three Salmonella serotypes S. Infantis, S. Schwarzengrund, and S. Manhattan-which are mainly found in broiler industries in Japan. Emergence frequency tests for quinolone-resistant variants using enrofloxacin-containing agar plates and sequence analysis in the quinolone resistance-determining region (QRDR) of gyrA in DNA gyrase were performed. The results showed no significant difference in the emergence frequency among the three serotypes, and most of the resistant variants had mutations in the QRDR region. These findings suggest that differences in the serotypes tested are not associated with the emergence frequency of quinolone-resistant variants.

Pseudomonas aeruginosa, which causes chronic infections, has demonstrated rapid acquisition of antimicrobial resistance (AMR). Therefore, bacteriophages have received significant attention as promising antimicrobial agents; however, previous trials have reported the occurrence of phage-resistant variants. P. aeruginosa has lost large chromosomal fragments via evolutionary selection by MutL. Mutants lacking galU and hmgA, located in close proximity, exhibit phage resistance and brown color phenotype since hmgA encodes a homogentisic acid metabolic enzyme and deletion of galU results in a lack of O-antigen polysaccharide and absence of the phage receptor. In the present study, we evaluated this mechanism for controlling phage resistance in P. aeruginosa veterinary isolate Pa12. Phage-resistant Pa12 brown mutants (brmts) with galU and hmgA deletions were isolated. Whole-genome sequencing of the brmts revealed that regions 148-27 kbp upstream and 261-110 kbp downstream of galU were largely deleted from the Pa12 parental chromosome. Furthermore, all of these fluctuating deleted sequences in Pa12 brmts, tentatively designated bacteriophage-induced galU deficiency (BigD) regions, harbor multi-drug efflux system genes (mexXY). Minimum inhibitory concentration (MIC) assays demonstrated that brmts altered sensitivity to antibiotics and exhibited increased levofloxacin sensitivity compared with the Pa12 parent. Orbifloxacin and enrofloxacin also effectively suppressed growth of the Pa12 brmts, suggesting that MexXY, which mediates quinolone efflux and is located in the BigD region, might be associated with restoration of fluoroquinolone sensitivity. Our findings indicate that AMR-related genes in the BigD region could produce trade-off effects between phages and drug sensitivity and thereby contribute to a potential strategy to control and prevent phage-resistant variants in phage therapy.

Transmission of tigecycline-nonsusceptible pathogenic Enterobacteriaceae from companion animals to human should be a concern because tigecycline is a last-line drug for treating multidrug-resistant Enterobacteriaceae in human medicine. However, tigecycline susceptibility of Enterobacteriaceae isolated from companion animals has not been investigated. In this study, we investigated the tigecycline susceptibility of Klebsiella pneumoniae complex and Escherichia coli isolates from dogs and cats, and evaluated their human pathogenicity potential. Tigecycline susceptibility of K. pneumoniae, including Klebsiella quasipneumoniae (n = 86) and E. coli (n = 100) strains isolated from dogs and cats was investigated. The antimicrobial susceptibility, capsular serotype, multilocus sequence type, ompK36 group, presence of virulence genes, and serum resistance of tigecycline-nonsusceptible isolates were evaluated. All E. coli isolates were susceptible to tigecycline. Two K. pneumoniae (minimum inhibitory concentration [MIC], 4 mg/L) and one K. quasipneumoniae (MIC, 8 mg/L) isolates were tigecycline resistant. Sixteen K. pneumoniae and one K. quasipneumoniae isolates were tigecycline intermediate (2 mg/L). All tigecycline-nonsusceptible isolates (n = 20) were also ciprofloxacin nonsusceptible. These isolates harbored five to nine virulence genes; 16 isolates were resistant to the human serum. In addition, STs of 13 K. pneumoniae isolates were reported to be found in strains isolated from human; isolates considered high-risk clones in human (ST11, ST15, and ST147) were also identified. In conclusion, the isolation of tigecycline-nonsusceptible K. pneumoniae from companion animals is an impact from the viewpoint of One Health approach to antimicrobial resistance that companion animals are a reservoir of human pathogenic lineages.

We report the complete genome sequence of the mcr-9 -possessing strain Enterobacter asburiae En30, isolated from a cat in Japan. The genome sequence was obtained by using long- and short-read sequencing.

The complete genome sequence of mcr-10 -possessing Enterobacter roggenkampii En37, isolated from a dog in Japan was determined. mcr-10 was located on a 70,277-bp IncFIB plasmid without any additional antimicrobial resistance genes.

A rapid method for the simultaneous detection of fluoroquinolone- and macrolide-resistant Campylobacter jejuni/coli in food products is long-awaited. In this study, we developed a DNA microarray-based method with primer extension, named CAMpylobacter Express Resistance Array (CAMERA). A series of oligonucleotide probes corresponding to each mutation in gyrA and rrl for fluoroquinolone and macrolide resistance, respectively, were selected and fixed on a membrane as capture probes for identifying C. jejuni/coli and detecting mutations conferring fluoroquinolone- and macrolide-resistance. The specificity was confirmed using 152 strains from livestock feces. Spiking of chicken meat samples revealed that CAMERA can detect 1–9 CFU/g C. jejuni/coli. Seventeen Campylobacter strains (16 C. jejuni and 1 C. coli) were isolated from 100 retail chicken meat samples via microbial culture. Using CAMERA, 16 of these 17 samples were positive for C. jejuni/coli, and the susceptibility to fluoroquinolone/macrolide could be determined (94% sensitivity and 100% specificity). The culture method requires more than 5–6 days for isolating C. jejuni/coli and determining antimicrobial susceptibility. In contrast, CAMERA requires

Stenotrophomonas maltophilia is capable of surviving in a wide variety of environments and is considered to be among the antimicrobial-resistant bacteria of greatest public health concern in hospital settings. To clarify the role of houseflies (Musca domestica) in disseminating this bacterium, we collected 99 individuals from 15 locations (9 farms and 6 urban areas) in Thailand. S. maltophilia was isolated from 39 % (39/99) of these houseflies, with the isolation rates being similar in farms and urban areas. Multiple-antimicrobial resistance was evident among the S. maltophilia isolates obtained. Of note, the rate of resistance to trimethoprim/sulfamethoxazole (TMP/SMX), the recommended first-line antimicrobial for S. maltophilia infection, was relatively high (30 %). Almost all of the isolates had a different PFGE pattern. These results suggest that houseflies ingest and host S. maltophilia from several different environmental sources. In conclusion, houseflies may facilitate the spread of antimicrobial-resistant (including TMP/SMX-resistant) S. maltophilia from environmental sources to humans.

In this research, we analyzed the main sequence types (ST) and ST complexes of human- and chicken-derived isolates of Campylobacter jejuni in Japan by using multilocus sequence typing (MLST). We also analyzed lipooligosaccharide biosynthesis locus classes (LOS locus classes) and the numbers of isolates carrying genes coding resistance factors against various antibiotics, and observed their relationships. ST-21 complex was the main ST complex in isolates from humans (n = 38) and chickens (n = 25). None of the isolates showed resistance to imipenem, chloramphenicol, or erythromycin. Few isolates were resistant to ampicillin and streptomycin (1.3%-15%), whereas many showed resistance to tetracycline, ciprofloxacin, and nalidixic acid (38%-48%). Among the ST-21 complex isolates, ST4526 was detected at a very high rate. Those isolates showed resistance to tetracycline and ciprofloxacin, and were susceptible to ampicillin. Among the chicken-derived isolates, 37 of the 38 isolates that showed resistance to ciprofloxacin and nalidixic acid had threonine to isoleucine amino acid substitution in GyrA at codon 86 (T86I). Among the human-derived isolates, 17 of the 47 isolates that showed resistance to ciprofloxacin and 16 of the 48 isolates that showed resistance to nalidixic acid did not have T86I amino acid mutations in GyrA. The human-derived ST-21 complex isolates were classified into LOS locus classes A, B, C, D, and E. The chicken-derived ST-21 complex isolates, with the exception of one isolate, were all classified into LOS locus classes C and D. Among chicken-derived isolates, the most prevalent was ST51 (ST-443 complex) (10 isolates) and all of those were LOS locus class E.

Pigs, particularly piglets, have been identified as reservoir hosts of Clostridium difficile. To examine the survival ability of this pathogen in pig feces-based manure compost, C. difficile spores, which were prepared to contain as few vegetative cells as possible, were artificially inoculated into pig feces and incubated at different temperatures. While C. difficile survived in the feces incubated at temperatures below 37 °C for over 30 days, cell numbers gradually decreased at thermophilic temperatures (over 55 °C; p

International audience; Formation of bacterial biofilms is a major health threat due to their high levels of tolerance to multiple antibiotics and the presence of persisters responsible for infection relapses. We previously showed that combination of starvation and induction of SOS response in biofilm lead to increase levels of persisters and biofilm tolerance to fluoroquinolones. In this study, we hypothesized that inhibition of the SOS response may be an effective strategy to target biofilms and fluoroquinolone persister cells. We tested the survival of Escherichia coli biofilms to different classes of antibiotics in starved and non-starved conditions and in presence of zinc acetate, a SOS response inhibitor. We showed that zinc acetate potentiates, albeit moderately, the activity of fluoroquinolones against E. coli persisters in starved biofilms. The efficacy of zinc acetate to increase fluoroquinolone activity, particularly tosufloxacin, suggests that such a combination may be a potential strategy for treating biofilm-related bacterial infections.

Following the emergence of antibiotic resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus pseudintermedius (MRSP), phage therapy has attracted significant attention as an alternative to antibiotic treatment. Bacteriophages belonging to kayvirus (previously known as Twort-like phages) have broad host range and are strictly lytic in Staphylococcus spp. Previous work revealed that kayvirus ɸSA039 has a host-recognition mechanism distinct from those of other known kayviruses: most of kayviruses use the backbone of wall teichoic acid (WTA) as their receptor; by contrast, ɸSA039 uses the β-N-acetylglucosamine (β-GlcNAc) residue in WTA. In this study, we found that ɸSA039 could switch its receptor to be able to infect S. aureus lacking the β-GlcNAc residue by acquiring a spontaneous mutation in open reading frame (ORF) 100 and ORF102. Moreover, ɸSA039 could infect S. pseudintermedius, which has a different WTA structure than S. aureus. By comparison with newly isolated S. pseudintermedius–specific phage (SP phages), we determined that glycosylation in WTA of S. pseudintermedius is essential for adsorption of SP phages, but not ɸSA039. Finally, we describe a novel strategy of S. aureus which protects the bacteria from infection of SP phages. Notably, glycosylation of ribitol phosphate (RboP) WTA by TarM or/and TarS prevents infection of S. aureus by SP phages. These findings could help to establish a new strategy for treatment of S. aureus and S. pseudintermedius infection, as well as provide valuable insights into the biology of phage–host interactions.

The aim of this study was to characterize the phenotypes and genotypes of Staphylococcus aureus isolated from raw bovine milk in Hokkaido, Japan. S. aureus isolates were identified in 135 of 436 milk samples from cows with and without signs of mastitis from three farms in Hokkaido. These clinical isolates were characterized for antimicrobial susceptibility patterns, molecular typing using phage-open-reading frame typing (POT), coagulase gene type, virulence genes, and biofilm-associated genes and were evaluated for biofilm-forming ability. Most isolates were susceptible to the antimicrobial agents tested. The highest rate of resistance was to ampicillin. Molecular typing of all S. aureus isolates indicated a predominance of coagulase type VI and 0-17-34 POT type, and virulence genes were highly prevalent in the isolates from all farms. Moreover, a high percentage of the 0-17-34 POT type isolates showed extensive formation of biofilm. These findings will help veterinarians and farmers to understand the epidemiology of S. aureus so that they can monitor the transmission and spread of this pathogen and control it more effectively.

Flies play a key role as vectors in transmitting various bacteria and pose bacterial contamination risk to food. To evaluate the time- and concentration-related bacterial contamination of food by houseflies based on their attraction to the food, we determined the number of fed antimicrobial-resistant Escherichia coli transferred from houseflies to foods, sugar and milk mixture, apple, and castella (such as sponge cake). Houseflies contaminated the foods with the fed E. coli within 5 min, and the bacteria were present in high numbers on apple and castella (3.3 × 103 and 3.5 × 104 CFU/g of food, respectively). Furthermore, the number of fed E. coli on the foods increased with time, rising to 3.6 × 104–1.7 × 105 CFU/g. We show that the food contamination level caused by houseflies depends on the concentration of bacteria that the houseflies carry, the contact time with the food, and the attraction of the flies to the food.

Objectives Escherichia coli (E. coli) is an indicator of antimicrobial resistance, and some strains of E. coli cause infectious diseases. E. coli sequence type 131 (ST131) – a global antimicrobial-resistant pandemic E. coli clone – is frequently detected in clinical specimens. Antimicrobial-resistant bacteria are monitored via national surveillance in clinical settings; however, monitoring information in non-clinical settings is limited. This study elucidated antimicrobial resistance trends of E. coli and dissemination of ST131 among healthy people in non-clinical settings. Methods This study collected 517 E. coli isolates from healthy people in Osaka, Japan, between 2013 and 2019. It analysed antimicrobial susceptibility of the isolates and detected the bla and mcr genes in ampicillin-resistant and colistin-resistant isolates, respectively, and the ST131 clone. Results Antimicrobial resistance rates of the bacteria isolated from healthy people in non-clinical settings were lower than for those in clinical settings. The resistance of the isolates to cefotaxime (4.4%) and ciprofloxacin (13.5%) gradually increased during the study period. In 23 cefotaxime-resistant isolates, the most frequent bla genes belonged to the blaCTX-M-9 group, followed by blaCTX-M-1 goup, blaTEM and blaCMY-2. One mcr-1-harbouring colistin-resistant isolate was detected in 2016. The incidence of the E. coli O25b-ST131 clone was approximately 5% until 2015 and 10% after 2016. Conclusion Both ciprofloxacin resistance and O25b-ST131 clone frequency increased during the study period. Antimicrobial-resistant bacteria gradually spread in healthy people in non-clinical settings; one reason behind this spread was dissemination of global antimicrobial-resistant pandemic clones.

The emergence of antibiotic-resistant bacteria in food, mainly contaminated meat and its products, and their transfer to humans is of great concern. To evaluate the potential risk of such contamination in Egypt, we isolated Escherichia coli from 78% (51/65) of raw beef and 53% (24/45) of ready-to-eat beef products. Of the 210 E. coli isolates detected, 8 (3.8%) harboured mcr-1 gene and were resistant to colistin, whereas 5 (2.4%) were positive for the blaCTX-M-28 gene and were resistant to cefotaxime. Among the colistin-resistant isolates, three had both mcr-1 and extended-spectrum beta-lactamase (ESBL) genes, constituting a great public health concern. The sequence types of all these mcr and/or ESBL-positive isolates were variable, suggesting that colistin and/or cephalosporin resistance spread through the mediation of plasmids harbouring mcr-1 or ESBL genes in Egyptian beef. In addition, various extraintestinal virulence genes were observed in some isolates. Colistin and cephalosporins are frequently used for livestock in Egypt; hence the present results suggest colistin and cephalosporin-resistant pathogenic E. coli are transferred from food animals to humans via meat and meat-derived products. Therefore, the rational use of antimicrobials and the appropriate safety measures in food production are needed in Egypt as well as in other developing countries.

We report the complete genome sequence of Escherichia coli strain HUE1, isolated from the urinary catheter of a female patient, showing fluoroquinolone resistance without quinolone resistance-determining region mutations. To facilitate the exploration of the molecular characteristics of HUE1, the whole genome was sequenced using long- and short-read platforms.

Houseflies are a mechanical vector for various types of bacteria, including antimicrobial-resistant bacteria (ARB). If the intestine of houseflies is a suitable site for the transfer of antimicrobial resistance genes (ARGs), houseflies could also serve as a biological vector for ARB. To clarify whether cephalosporin resistance genes are transferred efficiently in the housefly intestine, we compared with conjugation experiments in vivo (in the intestine) and in vitro by using Escherichia coli with eight combinations of four donor and two recipient strains harboring plasmid-mediated cephalosporin resistance genes and chromosomal-encoded rifampicin resistance genes, respectively. In the in vivo conjugation experiment, houseflies ingested donor strains for 6 hr and then recipient strains for 3 hr, and 24 hr later, the houseflies were surface sterilized and analyzed. In vitro conjugation experiments were conducted using the broth-mating method. In 3/8 combinations, the in vitro transfer frequency (Transconjugants/Donor) was ≥1.3 × 10(-4); the in vivo transfer rates of cephalosporin resistance genes ranged from 2.0 × 10(-4) to 5.7 × 10(-5). Moreover, cephalosporin resistance genes were transferred to other species of enteric bacteria of houseflies such as Achromobacter sp. and Pseudomonas fluorescens. These results suggest that houseflies are not only a mechanical vector for ARB but also a biological vector for the occurrence of new ARB through the horizontal transfer of ARGs in their intestine.

Stresses induced by welding are analyzed from the viewpoint of material deformation behavior. Strain gages are used to measure the residual stresses, and electronic speckle-pattern interferometry is used to analyze the response of the welded work to external force. A tensile load is applied to a butt-welded, thin-plate steel specimen, and the resultant strain field is analyzed with the electronic speckle-pattern interferometry. Comparison is made with the case of a nonwelded specimen of the same material and dimension. The analysis indicates that the residual stress due to welding makes the normal strain due to the external tensile load asymmetric. The asymmetry enhances shear and rotational modes of deformation, generating stress concentration at a point away from the weld where the residual stress is substantially negligible. The observed features are discussed based on physical mesomechanics. Analysis reveals plastic deformation like behavior in the response of the welded specimen to the external force.

We collected 200 Pseudomonas aeruginosa isolates from dogs and cats in primary veterinary hospitals in Japan to investigate their antimicrobial resistance. Resistance rates against ciprofloxacin, cefotaxime, gentamicin, amikacin, and fosfomycin were 9%, 12.5%, 4.5%, 2.5%, and 35.5%, respectively. One strain displayed resistance (0.5%) to ceftazidime. We did not detect any imipenem-resistant or multidrug-resistant P. aeruginosa strains as defined by the Japanese Ministry of Health, Labour, and Welfare Law Concerning the Prevention of Infections and Medical Care for Patients with Infections. In addition, we did not find any P. aeruginosa isolates that produced metallo-β-lactamase, the aminoglycoside 6'-N-acetyltransferase AAC(6')-Iae, or the aminoglycoside acetyltransferase AAC(6')-Ib.

The present study aimed to elucidate the prevalence of Clostridioides difficile in Japanese retail food products. For this purpose, retail food samples (242 fresh vegetables and 266 retail meat samples: 89 chicken meat; 28 chicken liver; 200 pork meat; 24 pig liver; 127 beef meat) were collected from 14 supermarkets between 2015 and 2019. C. difficile was isolated from eight (3.3%) fresh vegetable, six (6.7%) chicken meat, one (3.6%) chicken liver, one (0.5%) pork meat, and two (1.6%) beef meat samples; it was not isolated from pig liver. Of these isolates, 35% were toxigenic. All isolates were typable by PCR ribotyping and were resolved into 12 PCR ribotypes. Among these isolates, ribotype 014, which is distributed worldwide including in Japanese clinical cases, was detected among vegetable isolates. Therefore, although the C. difficile contamination rate in Japanese retail foods was low, these sources can be contaminated and could transmit these bacteria to humans.

Colistin is a last-line drug for multidrug-resistant Gram-negative bacteria. We previously reported four plasmid-mediated colistin resistance (mcr) gene-negative colistin-resistant Escherichia coli clinical isolates, including the major pathogenic and fluoroquinolone-resistant strains O25b:H4-ST131-H30Rx (isolates SRE34 and SRE44; MIC for colistin = 16 mg/liter), non-x (SME296; MIC = 8 mg/liter), and O18-ST416 (SME222; MIC = 4 mg/liter). In this study, we investigated the colistin resistance mechanism and identified novel amino acid substitutions or deletions in the PmrAB two-component system that activates eptA (encoding a phosphoethanolamine transferase) and arnT (encoding an undecaprenyl phosphate-alpha-4-amino-4-deoxy-l-arabinose arabinosyl transferase) in all colistin-resistant isolates. SRE34 possessed deletion Δ27-45 (LISVFWLWHESTEQIQLFE) in PmrB, SRE44 possessed substitution L105P in PmrA, and both SME222 and SME296 included substitution G206D in PmrB. Matrix-assisted laser desorption ionization-time of flight mass spectrometry revealed that lipid A is modified with phosphoethanolamine in all four isolates. Deletion of pmrAB decreased colistin MICs to 0.5 mg/liter and lowered eptA and arnT expression. Chromosomal replacement of mutated pmrA or pmrB in colistin-susceptible O25b:H4-ST131 strain SME98 (colistin MIC = 0.5 mg/liter) increased the colistin MIC to that of the respective parent colistin-resistant isolate. In addition, SME98 mutants in which pmrAB was replaced with mutated pmrAB showed no significant differences in bacterial growth and competition culture from the parent strain, except for the mutant with L105P in PmrA, whose growth was significantly suppressed in the presence of the parent strain. In conclusion, some O25b:H4-ST131 strains appear to acquire colistin resistance via phosphoethanolamine modification of lipid A through amino acid changes in PmrAB, and the amino acid changes in PmrB do not influence bacterial growth.

Colistin is a last-line drug for multidrug-resistant Gram-negative bacteria. We previously reported four plasmid-mediated colistin resistance (mcr) gene-negative colistin-resistant Escherichia coli clinical isolates, including the major pathogenic and fluoroquinolone-resistant strains O25b:H4-ST131-H30Rx (isolates SRE34 and SRE44; MIC for colistin = 16 mg/liter), non-x (SME296; MIC = 8 mg/liter), and O18-ST416 (SME222; MIC = 4 mg/liter). In this study, we investigated the colistin resistance mechanism and identified novel amino acid substitutions or deletions in the PmrAB two-component system that activates eptA (encoding a phosphoethanolamine transferase) and arnT (encoding an undecaprenyl phosphate-alpha-4-amino-4-deoxy-l-arabinose arabinosyl transferase) in all colistin-resistant isolates. SRE34 possessed deletion Δ27–45 (LISVFWLWHESTEQIQLFE) in PmrB, SRE44 possessed substitution L105P in PmrA, and both SME222 and SME296 included substitution G206D in PmrB. Matrix-assisted laser desorption ionization–time of flight mass spectrometry revealed that lipid A is modified with phosphoethanolamine in all four isolates. Deletion of pmrAB decreased colistin MICs to 0.5 mg/liter and lowered eptA and arnT expression. Chromosomal replacement of mutated pmrA or pmrB in colistin-susceptible O25b:H4-ST131 strain SME98 (colistin MIC = 0.5 mg/liter) increased the colistin MIC to that of the respective parent colistin-resistant isolate. In addition, SME98 mutants in which pmrAB was replaced with mutated pmrAB showed no significant differences in bacterial growth and competition culture from the parent strain, except for the mutant with L105P in PmrA, whose growth was significantly suppressed in the presence of the parent strain. In conclusion, some O25b:H4-ST131 strains appear to acquire colistin resistance via phosphoethanolamine modification of lipid A through amino acid changes in PmrAB, and the amino acid changes in PmrB do not influence bacterial growth.

The spreading of antimicrobial-resistant Enterobacteriaceae, especially those co-harboring plasmid-mediated cephalosporin (bla) and colistin (mcr) resistance genes, is becoming increasingly problematic. As a vector, flies carry antimicrobial-resistant bacteria (ARB) into human and livestock habitats. To investigate ARB in flies, we collected 235 flies from 27 sites (18 urban areas, five pig farms and four chicken farms) in Thailand during 2013-2015. Cefotaxime-resistant Enterobacteriaceae (CtxRE) and bla-positive CtxRE were isolated from 70 (29.8%) and 48 (20.4%) flies, respectively. In 93 bla-positive CtxRE isolates that included Escherichia coli, Enterobacter spp., and Klebsiella pneumoniae from 48 flies, the most frequent bla gene was TEM (n = 62), followed by CTX-M-55 (n = 31), CTX-M-14 (n = 26), CMY-2 (n = 24) and SHV (n = 10), and 58 isolates harbored multiple types of these genes. In addition, we detected the mcr-1 (n = 1) and mcr-3 (n = 19) genes in bla-positive CtxRE isolates from 16 flies. In conjugation experiments, 10 mcr-3- and bla-positive isolates exhibited co-transfer of mcr-3 and blaTEM-1 genes. These results suggest that a relatively high proportion of flies in Thailand carries cephalosporin-resistant Enterobacteriaceae harboring co-transmissible cephalosporin and colistin resistance genes.

Antibiotic-resistant bacteria (ARB) have spread widely and rapidly, with their increased occurrence corresponding with the increased use of antibiotics. Infections caused by Staphylococcus aureus have a considerable negative impact on human and livestock health. Bacteriophages and their peptidoglycan hydrolytic enzymes (endolysins) have received significant attention as novel approaches against ARB, including S. aureus. In the present study, we purified an endolysin, Lys-phiSA012, which harbors a cysteine/histidine-dependent amidohydrolase/peptidase (CHAP) domain, an amidase domain, and a SH3b cell wall binding domain, derived from a polyvalent S. aureus bacteriophage which we reported previously. We demonstrate that Lys-phiSA012 exhibits high lytic activity towards staphylococcal strains, including methicillin-resistant S. aureus (MRSA). Analysis of deletion mutants showed that only mutants possessing the CHAP and SH3b domains could lyse S. aureus, indicating that lytic activity of the CHAP domain depended on the SH3b domain. The presence of at least 1 mM Ca2+ and 100 µM Zn2+ enhanced the lytic activity of Lys-phiSA012 in a turbidity reduction assay. Furthermore, a minimum inhibitory concentration (MIC) assay showed that the addition of Lys-phiSA012 decreased the MIC of oxacillin. Our results suggest that endolysins are a promising approach for replacing current antimicrobial agents and may contribute to the proper use of antibiotics, leading to the reduction of ARB.

Dissemination of antimicrobial resistance is a major global public health concern. To clarify the role of flies in disseminating antimicrobial resistance between farms, we isolated and characterized tetracycline-resistant Escherichia coli strains isolated from flies and feces of livestock from four locations housing swine (abattoir, three farms) and three cattle farms. The percentages of isolates from flies resistant to tetracycline, dihydrostreptomycin, ampicillin, and chloramphenicol (80.8%, 61.5%, 53.8%, and 50.0%, respectively) and those from animal feces (80.5%, 78.0%, 41.5%, and 46.3%, respectively) in locations housing swine were significantly higher than those from cattle farms (p0.05). The rates of resistance in E. coli derived from flies reflected those derived from livestock feces at the same locations, suggesting that antimicrobial resistance spreads between livestock and flies on the farms. The results of pulsed-field gel electrophoresis (PFGE) analysis showed that, with a few exceptions, all E. coli isolates differed. Two pairs of tetracycline-resistant strains harbored similar plasmids with the same tetracycline-resistance genes, although the origin (fly or feces), site of isolation, and PFGE patterns of these strains differed. Therefore, flies may disseminate the plasmids between farms. Our results suggest that flies may be involved not only in spreading clones of antimicrobial-resistant bacteria within a farm but also in the widespread dissemination of plasmids with antimicrobial resistance genes between farms.

Quinolones have long been used as the first-line treatment for Campylobacter infections. However, an increased resistance to quinolones has raised public health concerns. The development of new quinolone-based antibiotics with high activity is critical for effective, as DNA gyrase, the target of quinolones, is an essential enzyme for bacterial growth in several mechanisms. The evaluation of antibiotic activity against Campylobacter jejuni largely relies on drug susceptibility tests, which require at least 2 days to produce results. Thus, an in vitro method for studying the activity of quinolones against the C. jejuni DNA gyrase is preferred. To identify potent quinolones, we investigated the interaction of C. jejuni DNA gyrase with a number of quinolones using recombinant subunits. The combination of purified subunits exhibited DNA supercoiling activity in an ATP dependent manner. Drug concentrations that inhibit DNA supercoiling by 50% (IC50s) of 10 different quinolones were estimated to range from 0.4 (sitafloxacin) to >100 µg/mL (nalidixic acid). Sitafloxacin showed the highest inhibitory activity, and the analysis of the quinolone structure-activity relationship demonstrated that a fluorine atom at R-6 might play the important role in the inhibitory activity against C. jejuni gyrase. Measured quinolone IC50s correlated well with minimum inhibitory concentrations (R = 0.9943). These suggest that the in vitro supercoiling inhibition assay on purified recombinant C. jejuni DNA gyrase is a useful and predictive technique to monitor the antibacterial potency of quinolones. And furthermore, these data suggested that sitafloxacin might be a good candidate for clinical trials on campylobacteriosis.

The persistence of the multi-drug resistance plasmids pAQU1 and IncFIB was examined in bacterial populations under very low selective pressure. We herein demonstrated that these plasmids stably remained not only in the original host, but also in a transconjugant, even after being in a non-culturable state. In seawater microcosms containing Photobacterium damselae 04Ya311 possessing pAQU1, no significant loss of pAQU1 was observed during a 30-d starvation period. The copy numbers of pAQU1 and IncFIB in E. coli were constant. The results of the present study suggest that these plasmids have the ability to remain among various bacteria under oligotrophic conditions with low antibiotic selection pressure.

We collected 200 Pseudomonas aeruginosa isolates from dogs and cats in primary veterinary hospitals in Japan to investigate their antimicrobial resistance. Resistance rates against ciprofloxacin, cefotaxime, gentamicin, amikacin, and fosfomycin were 9%, 12.5%, 4.5%, 2.5%, and 35.5%, respectively. One strain displayed resistance (0.5%) to ceftazidime. We did not detect any imipenem-resistant or multidrug-resistant P. aeruginosa strains as defined by the Japanese Ministry of Health, Labour, and Welfare Law Concerning the Prevention of Infections and Medical Care for Patients with Infections. In addition, we did not find any P. aeruginosa isolates that produced metallo-β-lactamase, the aminoglycoside 6'-N-acetyltransferase AAC(6')-Iae, or the aminoglycoside acetyltransferase AAC(6')-Ib.

Antibiotic resistance within food animal production systems is a very important public health concern. It is clear that antibiotics used in human and veterinary chemotherapy act as an important selective pressure for the emergence and persistence of antibiotic resistance. Salmonella and Campylobacter remain the most important foodborne pathogens that are known to serve as reservoirs of antibiotic resistance. Antibiotic-resistant bacteria and antibiotic-resistance genes have been reported in aquatic environments and associated wild and domestic animals and insects, which are acting as reservoirs of resistant organisms and genetic determinants. Bacteria can develop resistance to antimicrobials through different mechanisms, including mutation, acquisition of resistance genes, and efflux pumps. Once acquired, these phenotypes can spread to others via horizontal transfer mechanisms (i.e., transformation, transduction, and conjugation). Several approaches have been used in recent years as alternatives to traditional antibiotics with the goal of controlling resistance. Some of the approaches include chlorate- and nitro-based compounds; probiotics, prebiotics, and synbiotics; and plant alkaloid based herbal products. While each has its advantages and disadvantages, none has so far been proved to be an effective replacement for antibiotics.

There are concerns that the use of fluoroquinolones (FQs) and group housing of food animals may contribute to the development of bacterial FQ resistance. Here, we studied the effects of administering FQ to pigs on the selection of FQ-resistant Campylobacter. Fifteen pigs were randomly allocated to either a group treated with FQs (enrofloxacin or norfloxacin), or an untreated control group. The number of FQ-resistant Campylobacter in feces was determined using appropriate selective agar containing enrofloxacin. FQ-resistant Campylobacter from samples of both groups were observed on days 3 and 4. These bacteria persisted for up to 21 days after treatment was discontinued. To evaluate the effect of group housing on the transmission of FQ-resistant Campylobacter, five pigs infected with FQ-sensitive Campylobacter pigs and one pig infected with FQ-resistant Campylobacter were housed together. On day 3, FQ-resistant Campylobacter were isolated from all six pigs. Moreover, FQ-resistant Campylobacter were isolated from environmental samples from the pen. These results indicate that the treatment of pigs with FQs selects for and spreads FQ-resistant Campylobacter among the pen. Therefore, responsible and prudent use of FQs at pig farms is required to prevent the emergence and transmission of FQ-resistant Campylobacter.

This study aimed to investigate the genetic association between fluoroquinolone (FQ) and/or cephalosporin (CEP) resistance in Escherichia coli isolates from dogs, and the risk to human health. We characterized E. coli clinical isolates, derived from faecal samples of dogs attending veterinary hospitals, using phylogenetic grouping, determination of virulence factor (VF) prevalence, multilocus sequence typing (MLST) and O serotyping. The D group was the dominant phylogenetic group among strains resistant to FQ and/or CEP. In contrast, the dominant group among susceptible strains was group B2. Group D strains showed a significantly higher prevalence of VFs than strains belonging to groups A and B1, and were resistant to significantly more antimicrobials than group B2 strains. The phylogenetic distribution of FQ–CEP-resistant E. coli groups (FQ–CEPRECs) and FQ-resistant groups was significantly correlated (r = 0.98), but FQ–CEPRECs and CEP-resistant E. coli groups were not correlated (r = 0.58). Data from PFGE, O serotype and MLST analyses indicated that the majority of FQ-resistant strains derived from a particular lineage of phylogenetic group D: serotype O1 and sequence type (ST) 648. Some D-O1-ST648 strains carried bla CMY-2, showed multidrug resistance and possessed a higher prevalence of the VFs kspMT, ompT and PAI compared with other group D strains. Our data indicate that the emergence of FQ-CEP-resistant E. coli is based primarily on FQ-resistant E. coli. Moreover, as strains of the D-O1-ST648 lineage have been found in clinical isolates derived from humans at a relatively high frequency, our findings indicate that the spreading of D-O1-ST648 strains may cause serious difficulties in both veterinary and human clinical fields in the future.

Understanding the prevalence of antimicrobial-resistance and the relationship between emergence of resistant bacteria and clinical treatment can facilitate design of effective treatment strategies. We here examined antimicrobial susceptibilities of Escherichia coli isolated from dogs admitted to a university hospital (University hospital) and companion animal clinics (Community clinics) in the same city and investigated underlying multidrug-resistance mechanisms. The prevalence of E. coli with intermediate and resistant interpretations to ampicillin (AMP), enrofloxacin (ENR) and chloramphenicol (CHL) was higher in the University hospital than in the Community clinics cases. Use of antimicrobials, including fluoroquinolone, was also significantly higher in the University hospital than in the Community clinics cases. Upon isolation using ENR-supplemented agar plates, all ENR-resistant isolates had 3-4 nucleotide mutations that accompanied by amino acid substitutions in the quinolone-resistance-determining regions of gyrA, parC and parE, and 94.7% of all isolates derived from the University hospital showed AMP and/or CHL resistance and possessed blaTEM and/or catA1. The average mRNA expression levels of acrA, acrB and tolC and the prevalence of organic solvent tolerance, in isolates derived from ENR-supplemented agar plates were significantly higher in the University hospital than in the Community clinics isolates. Thus, E. coli derived from the University hospital cases more often showed concomitant decreased susceptibilities to aminopenicillins, fluoroquinolones and CHL than did those derived from the Community clinics; this was related to an active AcrAB-TolC efflux pump, in addition to acquisition of specific resistance genes and genetic mutations.

To determine the prevalence of indicator bacteria resistant to antimicrobials among poultry in three Southeast Asian countries (Vietnam, Indonesia and Thailand), we examined the antimicrobial susceptibilities of commensal bacteria isolated from chickens. In total, 125, 117 and 180 isolates of Escherichia coli, Enterococcus faecalis and Enterococcus faecium, respectively, were used to test for antimicrobial susceptibility. Bacterial resistance to antimicrobial treatment was most frequently observed with oxytetracycline with a prevalence of 73.6% (E. coli), 69.2% (E. faecalis) and 92.2% (E. faecium). Resistance to fluoroquinolones, which are critically important medicines, was also frequently observed in E. coli (48.8%), E. faecalis (17.9%) and E. faecium (82.8%). The prevalence of indicator bacteria resistant to most of the antimicrobials tested in these countries was higher than those for developed countries. The factors underlying antimicrobial resistance may include inappropriate and/or excessive use of antimicrobials. These results highlight the need for monitoring the emergence and prevalence of antimicrobial resistance in developing countries.

In this study, susceptibilities of Pasteurella multocida, Mannheimia haemolytica and Actinobacillus pleuropneumoniae to enrofloxacin and orbifloxacin were tested using an agar diffusion method with the commercial disks and a broth microdilution method. Good correlation between the 2 methods for enrofloxacin and orbifloxacin was observed for P. multocida (r = −0.743 and −0.818, respectively), M. haemolytica (r = −0.739 and −0.800, respectively) and A. pleuropneumoniae (r = −0.785 and −0.809, respectively). Based on the Clinical and Laboratory Standards Institute interpretive criteria for enrofloxacin, high-level categorical agreement between the 2 methods was found for P. multocida (97.9%), M. haemolytica (93.8%) and A. pleuropneumoniae (92.0%). Our findings indicate that the tested commercial disks can be applied for susceptibility testing of veterinary respiratory pathogens.

We conduct a series of tensile analyses on metal-plate specimens to investigate the relation between the fatigue level and the material’s response to external loads. We use Electronic Speckle-Pattern Interferometery (ESPI) to measures the in-plane displacement, and an acoustic transducer to assess the elastic modulus of the specimen via acoustic velocity measurement at various stress levels. We apply a tensile load at a constant pulling rate up to a certain stress level substantially lower than the yield stress, and analyze the strain field obtained with the ESPI setup at each time step. At the same time, we measure the acoustic velocity at various tensile stress levels. We have found repeatedly in the experiment on an aluminum-alloy specimen that (a) the strain field changes over several seconds after the tensile machine stops pulling, and (b) the acoustic velocity at the same point of the specimen considerably varies from measurement to measurement at the same stress level. These observations indicate that the specimen is deformed even if the crosshead of the tensile machine is stationary. This mysterious phenomenon is consistent with the observation made by Pappalettera et al. in their fatigue analysis that the acoustic emissions, which normally stops when the fatigue reaches a certain level, resumes if the specimen is dismounted from the test machine and remounted for continuation of the test.

The emergence of antimicrobial resistance in Klebsiella spp., including resistance to extended-spectrum cephalosporins (ESC) and fluoroquinolones, is of great concern in both human and veterinary medicine. In this study, we investigated the prevalence of antimicrobial resistance in a total of 103 Klebsiella spp. isolates, consisting of K. pneumoniae complex (KP, n=89) and K. oxytoca (KO, n=14) from clinical specimens of dogs and cats in Japan. Furthermore, we characterized the resistance mechanisms, including extended-spectrum β-lactamase (ESBL), plasmid-mediated AmpC β-lactamase (PABL), and plasmid-mediated quinolone resistance (PMQR); and assessed genetic relatedness of ESC-resistant Klebsiella spp. strains by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). Antimicrobial susceptibility testing demonstrated that resistance rates to ampicillin, cephalothin, enrofloxacin, ciprofloxacin, trimethoprim/sulfamethoxazole, cefotaxime, gentamicin, tetracycline, chloramphenicol, amoxicillin-clavulanic acid, and cefmetazole were 98.1 %, 37.9 %, 37.9 %, 35.9 %, 35.0 %, 34.0 %, 31.1 %, 30.1 %, 28.2 %, 14.6 %, and 6.8 %, respectively. Phenotypic testing detected ESBLs and/or AmpC β-lactamases in 31 of 89 (34.8 %) KP isolates, but not in KO isolates. Resistances to five of the twelve antimicrobials tested, as well as the three PMQRs (qnrB, qnrS, and aac(6′)-Ib-cr), were detected significantly more frequently in ESBL-producing KP, than in non-ESBL-producing KP and KO. The most frequent ESBL was CTX-M-15 (n=13), followed by CTX-M-14 (n=7), CTX-M-55 (n=6), SHV-2 (n=5), CTX-M-2 (n=2), and CTX-M-3 (n=2). Based on the rpoB phylogeny, all ESBL-producing strains were identified as K. pneumoniae, except for one CTX-M-14-producing strain, which was identified as K. quasipneumoniae. All of AmpC β-lactamase positive isolates (n=6) harbored DHA-1, one of the PABLs. Based on MLST and PFGE analysis, ST15 KP clones producing CTX-M-2, CTX-M-15, CTX-M-55, and/or SHV-2, as well as KP clones of ST1844-CTX-M-55, ST655-CTX-M-14, and ST307-CTX-M-15, were detected in one or several hospitals. Surprisingly, specific clones were detected in different patients at an interval of many months. These results suggest that multidrug-resistant ESBL-producing KP were clonally disseminated among companion animals via not only direct but also indirect transmission. This is the first report on large-scale monitoring of antimicrobial-resistant Klebsiella spp. isolates from companion animals in Japan.

Pseudomonas aeruginosa is an important cause of racehorse keratitis. Bacteriophage therapy has the potential to aid in the prevention and treatment of diseases caused by P. aeruginosa . We present here the complete genome sequences of two phages, ΦR18 and ΦS12-1, which exhibit infectivity for a broad range of P. aeruginosa isolates.

Antimicrobials are widely used, not only for treating human infections, but also for treatment of livestock and in fish farms. Human habitats in Southeastern Asian countries are located in close proximity to aquatic environments. As such, the human populations within these regions are at risk of exposure to antimicrobial resistant bacteria (ARB), and thereby disseminating antimicrobial resistance genes (ARGs). In this study, we collected water samples from 15 sites (5 sites in Chao Phraya River, 2 sites at the mouth of Chao Phraya River, 3 sites in Ta Chin River, and 5 sites at city canals) and 12 sites (6 sites at city canals, 2 sites at chicken farms, 2 sites at pig farms, and 2 samples from sites at pig farms that were subsequently treated at a biogas plant) in Thailand in 2013 and 2014, respectively. In total, 117 Aeromonas spp. were isolated from the water samples, and these organisms exhibited various antimicrobial susceptibility profiles. Moreover, there was a significant correlation between the environmental concentration of tetracyclines and the rates of tetracycline resistance in the isolated Aeromonas spp. Notably, however, the concentration and resistance rates of tetracycline in samples derived from pig farms were higher than those of samples harvested from other aquatic environments. These findings suggest that the high concentrations of antimicrobials observed in these aquatic environments likely select for ARGs. Furthermore, they indicate that Aeromonas spp. comprise an effective marker for monitoring antimicrobial resistance in aquatic environments.

Pseudomonas aeruginosa is a pathogen frequently identified as the cause of diverse infections or chronic disease. This microbe has natural resistance to several kinds of antibiotics, because of the species’ outer membrane, efflux pumps and growth as a biofilm. This bacterium can acquire increased resistance with specific point mutations. Bacteriophage (phage), however, can lyse these bacteria. Therefore, in the present study, we assessed the host range of phages isolates and their ability to lyse antibiotic-resistant P. aeruginosa. Present phages could lyse many strains of P. aeruginosa (28/39), including strains with high resistance to fluoroquinolones (4/6). In conclusion, application of phages for antibiotic-resistant bacteria is greatly effective. To avoid pervasive antibiotic-resistant bacteria, further development of phage usage for disease treatment is required.

Co-application of acoustoelasticity and optical interferometry to residual stress analysis is discussed. The underlying idea is to combine the advantages of both methods. Acoustoelasticity is capable of evaluating a residual stress absolutely but it is a single point measurement. Optical interferometry is able to measure deformation yielding two-dimensional, full-field data, but it is not suitable for absolute evaluation of residual stresses. By theoretically relating the deformation data to residual stresses, and calibrating it with absolute residual stress evaluated at a reference point, it is possible to measure residual stresses quantitatively, nondestructively and two-dimensionally. The feasibility of the idea has been tested with a butt-jointed dissimilar plate specimen. A steel plate 18.5 mm wide, 50 mm long and 3.37 mm thick is braze-jointed to a cemented carbide plate of the same dimension along the 18.5 mm-side. Acoustoelasticity evaluates the elastic modulus at reference points via acoustic velocity measurement. A tensile load is applied to the specimen at a constant pulling rate in a stress range substantially lower than the yield stress. Optical interferometry measures the resulting acceleration field. Based on the theory of harmonic oscillation, the acceleration field is correlated to compressive and tensile residual stresses qualitatively. The acoustic and optical results show reasonable agreement in the compressive and tensile residual stresses, indicating the feasibility of the idea.