Serotyping reanalysis of unserotypable Actinobacillus pleuropneumoniae isolates by agar gel diffusion test.

We observed increasing unserotypable (UT) Actinobacillus pleuropneumoniae isolates using agar gel diffusion (AGD) test. To reanalyze their serovar, we performed rapid slide agglutination (RSA) test and multiplex PCR for 47 UT isolates. Of these, 25 were serovar 1 (UT-serovar 1), 20 were serovar 2 (UT-serovar 2) and 2 were serovar 15 (UT-serovar 15). We examined serotyping antigen extraction temperature to determine heat influence. UT-serovar 1 and 15 were influenced by heat, because their precipitation lines were observed in the case of low antigen extraction temperature. To investigate the relationship between antigenicity and genotype, we performed pulsed-field gel electrophoresis (PFGE) analysis using UT-serovar 2 and 15. The predominant PFGE pattern of UT-serovar 2 was identical to that of serovar 2.

National monitoring for antimicrobial resistance among indicator bacteria isolated from food-producing animals in Japan.

The antimicrobial susceptibilities of 2,205 isolates of Escherichia coli and 1,181 isolates of Enterococcus faecalis (n=610) and E. faecium (n=571) from apparently healthy cattle, pigs and broiler and layer chickens collected from 2000 to 2003 were examined using an agar dilution method. Overall, the isolates from cattle and layer chickens showed a lower incidence of resistance to almost all antimicrobials studied compared with those from pigs and broiler chickens. Fluoroquinolone resistance was found at a low level in isolates of E. coli from four animal species and in E. faecalis from pigs and broiler and layer chickens. Resistance to cephalosporin was identified in isolates of E. coli from broiler chickens in 2000-2002 and from four animal species in 2003. Incidence of antimicrobial resistance in the bacteria did not vary from year to year during the investigation period.

National surveillance of Salmonella enterica in food-producing animals in Japan.

A total of 518 fecal samples collected from 183 apparently healthy cattle, 180 pigs and 155 broilers throughout Japan in 1999 were examined to determine the prevalence and antimicrobial susceptibility of Salmonella. The isolation rates were 36.1% in broilers, 2.8% in pigs and 0.5% in cattle. S. enterica Infantis was the most frequent isolate, found in 22.6% of broiler fecal samples. Higher resistance rates were observed against oxytetracycline (82.0%), dihydrostreptomycin (77.9%), kanamycin (41.0%) and trimethoprim (35.2%). Resistance rates to ampicillin, ceftiofur, bicozamycin, chloramphenicol and nalidixic acid were <10%. CTX-M-2 beta-lactamase producing S. enterica Senftenberg was found in the isolates obtained from one broiler fecal sample. This is the first report of cephalosporin-resistant Salmonella directly isolated from food animal in Japan.

Recent trends in antimicrobial susceptibility and the presence of the tetracycline resistance gene in Actinobacillus pleuropneumoniae isolates in Japan.

A total of 101 Actinobacillus pleuropneumoniae isolates from diseased pigs taken from across Japan during 2002 to 2005 were examined for antimicrobial susceptibility. All isolates were susceptible to ceftiofur, erythromycin, florfenicol and enrofloxacin. Antimicrobial-resistant isolates to oxytetracycline (OTC) (27.7%), dihydrostreptomycin (10.9%), thiamphenicol (10.9%), kanamycin (5.9%), trimethoprim (4.0%) and ampicillin (2.0%) were recognized. OTC-resistant isolates taken from 1986 to 2005 were examined for the tetracycline resistance gene. In OTC-resistant isolates, tetB has been the most frequently isolated gene in Japan. It is likely that the dissemination of tetB has contributed to the increased OTC resistance of A. pleuropneumoniae in Japan.

[Present situation of national surveillance of antimicrobial resistance in bacteria isolated from farm animals in Japan and correspondence to the issue].

The Japanese Veterinary Antimicrobial Resistance Monitoring System (JVARM) was formed in 1999 in response to international concerns about the impact of antimicrobial resistance on public health. The aim of the present investigation was to provide insight into the occurrence of antimicrobial resistance among bacterial strains isolated from cattle, swine and poultry on farms across Japan. In this paper, we summarize a nationwide investigation (1999-2003) on antimicrobial susceptibility of the targeted bacterial species for the JVARM, namely Salmonella, Campylobacter, Enterococcus and Escherichia coli, isolated from the feces of healthy domestic animals. Minimum inhibitory concentrations (MICs) of 10-18 antimicrobial agents including the major generic groups were determined using an agar dilution method according to the international NCCLS guideline in principle. The outline of present results is as follows: (1) A total of 307 Salmonella, 3,225 Escherichia coli, 2,822 Enterococcus and 1,122 Campylobacter were isolated from healthy domestic animals and examined for antimicrobial susceptibility. (2) The isolates of all targeted bacterial species represent high rates of antimicrobial resistance to both oxytetracycline (OTC) and dihydrostreptomycin (DSM). (3) Among the isolates of Campylobacter and E. coli, the frequency of isolation of resistance to fluoroquinolones ranged from 14 to 24% and 2 to 3%, respectively. (4) Resistance to fluoroquinolones was not observed among the isolates of Salmonella or Enterococcus. Continious investigation at the nation level of antimicrobial resistance among the isolates from healthy domestic animals remains a high priority for the JVARM program. Furthermore, appropriate and prudent use of antimicrobials for diseased animals should be considered essential.

In vitro activity of 24 antimicrobial agents against Staphylococcus and Streptococcus isolated from diseased animals in Japan.

A total of 88 Staphylococcus and 61 Streptococcus isolates from diseased animals throughout Japan were examined in 2000 for the minimum inhibitory concentrations of 24 different antimicrobials by the agar dilution method standardized by the Japanese Society of Chemotherapy. The resistance rates to aminobenzylpenicillin (36.4%) and benzylpenicillin (35.2%) were high in Staphylococcus isolates, and those to oxytetracycline (45.9%) and kanamycin (21.3%) were high in Streptococcus isolates. Two isolates resistant to oxacillin harbored the mecA gene. One was Staphylococcus epidermidis derived from a pig with arthritis, and the other Staphylococcus cohnii from a head of cattle with mastitis.

Antimicrobial susceptibility of Mannheimia haemolytica isolates from cattle in Japan from 2001 to 2002.

A total of 27 clinical isolates of Mannheimia haemolytica from cattle in Japan from 2001 to 2002 were examined for antimicrobial susceptibility to 25 antimicrobial agents. The minimum inhibitory concentrations of 25 different antimicrobials were determined by an agar dilution method according to the guidelines of the National Committee for Clinical Laboratory Standards. Of the 27 isolates, seven isolates (26.9%) were resistant to at least one of the 25 drugs and resistance rates ranged from 3.7 to 18.5%. Resistance rates to dihydrostreptomycin (18.5%), oxytetracycline (11.1%), and doxycycline (11.1%) were relatively high and those to the remaining drugs were less than 10%.

Antimicrobial susceptibilities of Campylobacter isolated from food-producing animals on farms (1999-2001): results from the Japanese Veterinary Antimicrobial Resistance Monitoring Program.

Nationwide monitoring of antimicrobial resistance in Campylobacter isolated from food-producing animals on farms was performed in Japan. A total of 468 Campylobacter isolates were obtained during the period from June 1999 to March 2001. Campylobacter species showed high frequencies of resistance to oxytetracycline and dihydrostreptomycin. The frequencies of resistance in Campylobacter coli to aminoglycosides, macrolides, tetracycline and quinolones were higher than those in Campylobacter jejuni to the same drugs. All of the C. jejuni isolates were susceptible to macrolide antibiotics, whereas 48.4% of the C. coli isolates were resistant to macrolides. Resistance to fluoroquinolones was observed in C. jejuni isolates from broilers (12%) and layers (2.6%), indicating that the level of fluoroquinolone resistance in Japan could be ranked as low.

Epidemiological characterization of Salmonella Typhimurium DT104 prevalent among food-producing animals in the Japanese veterinary antimicrobial resistance monitoring program (1999-2001).

In the course of nationwide investigation on epidemiological characteristics in Salmonella Typhimurium isolates from food-producing animals in Japan between 1999 and 2001, fifty-seven isolates of S. Typhimurium DT104 and 104B obtained from cattle and swine at farm level in Japan between 1999 and 2001 were classified with pulsotype and antimicrobial resistance type. Most of the isolates were resistant to five or more antimicrobials and were genotyped into four groups. The present nationwide investigation shows that at least 11 types of S. Typhimurium related to DT104 are prevalent among food-producing animals across the country.

Antimicrobial susceptibility of Salmonella isolated from cattle, swine and poultry (2001-2002): report from the Japanese Veterinary Antimicrobial Resistance Monitoring Program.

OBJECTIVES: The Japanese Veterinary Antimicrobial Resistance Monitoring (JVARM) Program was established in 1999 to examine the susceptibility of bacteria from food-producing animals to antimicrobial agents. This study tested the susceptibility of Salmonella isolates collected during 2001-2002 to 20 antimicrobials. MATERIALS AND METHODS: MICs of antimicrobial agents were determined using the NCCLS agar dilution method, and interpreted according to breakpoints obtained from the bimodal MIC distributions. RESULTS: A total of 82 Salmonella were isolated from food-producing animals and tested for antimicrobial susceptibility. Isolates resistant to ampicillin, dihydrostreptomycin, kanamycin, oxytetracycline, chloramphenicol, bicozamycin, nalidixic acid, oxolinic acid and trimethoprim were obtained from healthy animals and diagnostic sample submissions. Salmonella Dublin was isolated only from cattle and showed resistance to older quinolones. Resistance to ampicillin, dihydrostreptomycin, kanamycin and oxytetracycline was common across all serotypes. Fluoroquinolone-resistant Salmonella Choleraesuis was isolated from swine and was the first Japanese report on this type of resistance in Salmonella from an animal origin. Most Salmonella Typhimurium isolates showed resistance to ampicillin, chloramphenicol, dihydrostreptomycin and oxytetracycline. S. Typhimurium DT104 accounted for 40.7% of S. Typhimurium isolates and was more often multi-drug resistant. Most Salmonella Infantis isolates from poultry showed resistance to dihydrostreptomycin, oxytetracycline, trimethoprim or kanamycin. In Salmonella Enteritidis, the major serotype isolated from food-poisoning in Japan, only resistance to dihydrostreptomycin was observed. CONCLUSIONS: This is the first JVARM report of Salmonella isolates, and continuous investigations at the national level on antimicrobial resistance in Salmonella isolated from food-producing animals will be important in the JVARM Program.

A national surveillance of antimicrobial resistance in Escherichia coli isolated from food-producing animals in Japan.

A nationwide investigation of antimicrobial susceptibility in Escherichia coli isolated from food-producing animals was performed in Japan. MICs of 18 antimicrobial agents were determined for a total of 1018 isolates. Higher resistance rates were observed against sulfadimethoxine, oxytetracycline and dihydrostreptomycin, followed by ampicillin and kanamycin. Resistance was more frequently observed among broiler isolates, followed by isolates from pigs. Almost 10% of broiler isolates were resistant to fluoroquinolones and extremely high MICs (100 mg/L) were observed. In general, antimicrobial resistance rates in E. coli have declined in recent years, with the exception of resistance to fluoroquinolones among broiler isolates, which has increased.