Prevalence of Vibrio parahaemolyticus Causing Acute Hepatopancreatic Necrosis Disease of Shrimp in Shrimp, Molluscan Shellfish and Water Samples in the Mekong Delta, Vietnam.

A total of 481 samples, including 417 shrimp and molluscan shellfish samples from retail shops and farms and 64 water samples from shrimp and molluscan shellfish farms in the Mekong Delta located the southern part of Vietnam, were examined for the presence of Vibrio parahaemolyticus (VpAHPND) caused acute haepatopancreatic necrosic disease (AHPND) in shrimp. VpAHPND strains were isolated in two of 298 (0.7%) molluscan shellfish samples from retail shops, seven of 71 (9.9%) shrimp samples from shrimp ponds, and two of 42 (4.8%) water samples from shrimp ponds. VpAHPND strains were classified into two types of O antigen, including O1 and O3, in which O1 was the predominant. VpAHPND strains isolated showed high resistance rates to colistin (100%), ampicillin (93.8%), and streptomycin (87.5%). These results indicate that VpAHPND is widely prevalent in environment in the Mekong Delta, Vietnam.

Acquisition of mcr-1 and Cocarriage of Virulence Genes in Avian Pathogenic Escherichia coli Isolates from Municipal Wastewater Influents in Japan.

This study focused on the detection of the plasmid-mediated mcr colistin resistance gene in Escherichia coli isolates from wastewater treatment plants (WWTPs). Seven influent samples were collected from three WWTPs in Nagano Prefecture, Japan, during August and December 2018. Colistin-resistant E. coli isolates were selected on colistin-supplemented CHROMagar ECC plates. mcr-1-positive isolates were subjected to whole-genome sequencing (WGS) analysis. From six influent samples, seven mcr-1-positive but extended-spectrum ß-lactamase (ESBL)-negative isolates belonging to different genetic lineages, namely, B2-O25:H4-ST131-fimH22, B2-O2:H1-ST135-fimH2, B1-O8:H9-ST764-fimH32, B1-O23:H16-ST453-fimH31, A-O81:H27-ST10-fimH54, A-O16:H5-ST871-fimH25, and F-O11:H6-ST457-fimH145, were detected. The MICs of colistin for these isolates ranged from 4 to 16 mg/liter. The mcr-1 genes were located on plasmids belonging to IncX4 and IncI2 in five and two isolates, respectively. Four IncX4 plasmids with the same size (33,309 bp) showed high sequence similarity (4 single-nucleotide variations). The remaining one IncX4 plasmid, with a size of 33,858 bp, carried the mcr-1 gene with the single synonymous nucleic substitution T27C. Two IncI2 plasmids with sizes of 60,710 bp and 60,733 bp had high sequence similarity (99.9% identity; 100% query coverage). Two of five isolates carrying IncX4 plasmids and both of the isolates carrying IncI2 plasmids harbored ColV plasmids carrying virulence-associated genes of avian pathogenic E. coli (APEC). In addition, another isolate of the B2-O25:H4-ST131-fimH22 lineage had those APEC-associated virulence genes on its chromosome. In conclusion, mcr-1-positive E. coli environmental isolates were mostly characterized as positive for APEC-associated virulence genes. The copresence of those genes may suggest the existence of a common source in animals and/or their associated environments.IMPORTANCE Colistin is considered a last-line therapeutic option in severe infections due to multidrug-resistant Gram-negative bacteria, in particular carbapenemase-producing Enterobacteriaceae and multidrug-resistant Acinetobacter baumannii An increasing prevalence of mcr genes in diverse Enterobacteriaceae species, mainly Escherichia coli and Klebsiella pneumoniae from humans and food animals, has become a significant concern to public health all over the world. In Japan, mcr genes have so far been detected in food animals, raw meat, wastewater, and human clinical samples. This study reports the copresence of mcr-1 and avian pathogenic E. coli (APEC)-associated virulence genes in five of seven E. coli isolates recovered from aquatic environments in Japan. Our study highlights the importance and urgency of action to reduce environmental contamination by mcr genes that may likely occur due to exposure to untreated wastewater through combined sewer overflow by recent unusual weather.

MASTDISCS combi Carba plus, a simple method for discriminating carbapenemase-producing Enterobacteriaceae, including OXA-48-type producers.

Accurate and rapid detection of carbapenemases and identification of their types in Enterobacteriaceae are both still major challenges for clinical laboratories in attempting to prevent the intrusion and transmission of carbapenemase-producing Enterobacteriaceae. This study aimed to evaluate the performance of the MASTDISCS combi Carba plus disc system in identification of different carbapenemase types, including OXA-48-type carbapenemase, for which no specific enzyme inhibitors have so far been available. The simple disc system discriminates carbapenemases, including OXA-48-types exhibiting low carbapenem minimum inhibitory concentrations, by targeting Enterobacteriaceae isolates with a EUCAST meropenem screening cut-off of ≥0.25 mg/L.

Evaluation of Chromogenic Medium for Selective Isolation of Yersinia.

Cefsulodin-irgasan-novobiocin agar (CIN) has been used as a selective agar to detect Yersinia in food or human patients; however, its components can inhibit the growth of some strains of Yersinia enterocolitica serovar O3 and Y. pseudotuberculosis. Recently, a new Yersinia selective agar, CHROMagar Yersinia enterocolitica (CAYe), was developed and evaluated as a novel selective agar for pathogenic Y. enterocolitica. In this research, a total of 251Yersinia strains (176 pathogenic Y. enterocolitica, 59 Y. pseudotuberculosis, and 16 non-pathogenic Yersinia) were cultured on both CIN and CAYe for comparison. Except for 10 of 104 pathogenic Y. enterocolitica O3 strains and 59 Y. pseudotuberculosis strains, 198 Yersinia isolates grew on both media after 48 hr of incubation at 32℃. Of the 10 pathogenic Y. enterocolitica O3 which could not grow on CIN or CAYe, 9 strains could not grow on CIN with supplements and 1 strain could not grow CAYe with supplements. Of 9 strains which did not grow on CIN with supplements, 3 strains could not grow on CIN without supplements. However, 1 strain which did not grow on CAYe with supplements could grow on CAYe without supplements. All of the Y. pseudotuberculosis strains could grow on CIN with/without supplements and on CAYe without supplements. The results indicate that the inhibition of the growth of Y. enterocolitica O3 on CIN is related to the components of CIN; however, the inhibition on CAYe appears to be related to the supplements in CAYe. Therefore, CAYe may be a more useful selective medium than CIN for pathogenic Y. enterocolitica .

Factors for occurrence of extended-spectrum ß-lactamase-producing Escherichia coli in broilers.

To clarify the factors for occurrence of extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli in broilers, two flocks (1 day of age) fed a diet with or without antibiotics were kept in a broiler house sanitized with disinfectants. ESBL-producing E. coli, however, was detected at a concentration of over 10(6) CFU/g of feces at 9 days of age to 49 days of age in both broiler flocks. Therefore, this indicated that the antibiotics other than cephalosporins used in this study had no effect due to co-selection on the numbers of ESBL-producing E. coli in broiler feces during this period. When a flock was kept with diet containing antibiotics for 49 days in a laboratory animal room, no ESBL-producing E. coli was detected in the flock. These results suggest that the occurrence of ESBL-producing E. coli may not be related to feeding with antibiotics and that the contamination of broiler houses with ESBL-producing E. coli might be an important factor.

Substrate specificity of HMRZ-86 for beta-lactamases, including extended-spectrum beta-lactamases (ESBLs).

HMRZ-86 was designed as a new chromogenic cephalosporin to detect extended-spectrum beta-lactamases (ESBLs) and similar evolved beta-lactamases, such as metallo-beta-lactamases, derepressed AmpC, and extended oxacillinase. We report here our investigation of the kinetic parameters of several types of beta-lactamases to show the enzymatic characteristics of HMRZ-86. The Michaelis constant (Km values of HMRZ-86 for ESBLs were twice to three and half times as high as those of nitrocefin, and the maximum velocity (Vmax) was one-fifth that of nitrocefin. The Km and Vmax of HMRZ-86 for AmpC were both smaller than those of nitrocefin. The kinetic parameters of HMRZ-86 for metallo beta-lactamase (MBL) were very variable, depending on the type of buffer solution used and the concentration of zinc ions. For MBL, the Km values of HMRZ-86 were higher than those of nitrocefin, but the Vmax values were almost the same as those of nitrocefin. Although the chemical structure of HMRZ-86 is similar to that of nitrocefin, we think the enzymatic reactivities of the two entities for beta-lactamases are very different.

The synthesis of 7-substituted-3-dinitrostyryl cephalosporins and their ability for detecting extended spectrum beta-lactamases (ESBLs).

We synthesized 7-substituted-3-(2,4-dinitrostyryl)cephalosporin derivatives which were Nitrocefin analogs, for detecting extended spectrum beta-lactamase (ESBL) specifically. HMRZ-86 which has carboxypropyloxyimino group on 7-aminothiazolacetamide substituent were not hydrolyzed by class A, C and D beta-lactamases, but it was hydrolyzed by ESBL and metallo beta-lactamase (class B), then its color changed from yellow to red. The hydrolysis of metallo beta-lactamase was inhibited by adding sodium mercapto acetic acid (SMA). Therefore HMRZ-86 is a useful chromogenic agent to detect ESBL specifically.

Anatomical structure of the isthmus between the inferior vena cava and tricuspid annulus investigated with a three-dimensional electroanatomical mapping system.

We studied the anatomical structure of the isthmus between the inferior vena cava and tricuspid annulus in humans with a three-dimensional electroanatomical mapping system (CARTO, Biosense, Haifa, Israel). Fifteen patients with atrial flutter were studied. Thirteen patients had underlying heart disease. We investigated the anatomical structure of the isthmus with cross sections made from the three-dimensional right atrial map. The cross sections of the isthmus showed a concave shape in 7 patients (47%: group A), convex shape in 2 (13%: group B), and complex shape in 6 (40%: group C). The distance between the IVC and TA was 34+/-17 mm (group A), 25+/-2 mm (group B), 34+/-16 mm (group C), and 32+/-15 mm (Total), respectively. The distance between the top and bottom was 6+/-5 mm (group A), 3 mm (group B), 6+/-3 mm (group C), and 6+/-4 mm (total), respectively. Seven of 15 patients exhibited an uneven surface of more than 5 mm in depth and 4 of 15 patients had one of more than 10 mm. The anatomical structure of the isthmus varies. To carry out precise catheter ablation, these variations should be taken into consideration to ensure an effective procedure.

[Evaluation of a new chromogenic medium for isolation of MRSA].

Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for an increasing number of serious nosocomial and community-acquired infections, and accurate methods to detect such strains are needed. We tested the susceptibility of 3 kinds of MRSA isolation medium, MRSA Screen Agar, Oxacillin Resistance Screening Agar and CHROMagar MRSA. Both sensitivity and specificity of CHROMagar MRSA were 100%. The sensitivity and specificity of both MRSA Screen Agar and Oxacillin Resistance Screening Agar were 100% and 91.5%, respectively. It is suggested that CHROMagar MRSA is a useful medium to detect MRSA including mecA positive and oxacillin susceptible strains.