Performance of MALDI-TOF Mass Spectrometry (VITEK MS) in the Identification of Salmonella Species.

Salmonella is a major pathogen causing foodborne infections in humans. Salmonella isolates are identified using biochemical and serological tests, including automated systems such as the VITEK2 system. However, there are few reports on Salmonella identification using VITEK MS. Therefore, we aimed to evaluate the usefulness of MALDI-TOF VITEK MS for Salmonella identification. A total of 1389 Salmonella isolates were identified using VITEK MS ver3.0 or ver3.2. All Salmonella isolates were confirmed by serotyping using the Kauffmann-White scheme, and the results were compared with the VITEK MS results. A total of 1389 Salmonella isolates, including 66 serotypes, were correctly identified at the genus level by VITEK MS. However, these systems failed to correctly identify typhoidal Salmonella. Among the five Salmonella enterica ssp. diarizonae isolates, only one was correctly identified, whereas one and three isolates were partially identified and misidentified, respectively. On the other hand, the VITEK2 system successfully identified all typhoidal Salmonella (Typhi and Paratyphi A) and Salmonella enterica ssp. diarizonae isolates. VITEK MS was useful for identifying Salmonella species isolated from clinical specimens; however, additional biochemical tests, such as the VITEK2 System, should be considered to accurately identify Salmonella ser. Typhi, and Salmonella ser. Paratyphi A.

Serotype Distribution and Antimicrobial Resistance of Salmonella Isolates in Korea between 2016 and 2017.

Salmonella is one of the major causes of food-borne infections. We investigated the serotype distribution and antimicrobial resistance of Salmonella isolates collected in Korea between January 2016 and December 2017. In total, 669 Salmonella isolates were collected from clinical specimens at 19 university hospitals. Serotyping was performed according to the Kauffmann-White scheme, and antimicrobial susceptibility was tested using Sensititre EUVSEC plates or disk diffusion. Among the strains, C (39.8%) and B (36.6%) were the most prevalent serogroups. In total, 51 serotypes were identified, and common serotypes were S. enterica serovar I 4,[5],12:i:- (16.7%), S. Enteritidis (16.1%), S. Bareilly (14.6%), S. Typhimurium (9.9%), and S. Infantis (6.9%). The resistance rates to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole were 32.6%, 12.1%, and 8.4%, respectively. The resistance rates to cefotaxime and ciprofloxacin were 8.1% and 3.0%, respectively, while 5.4% were multidrug-resistant. S. enterica serovar I 4,[5],12:i:- and S. Enteritidis were highly prevalent, and there was an increase in rare serotypes. Multidrug resistance and ciprofloxacin resistance were highly prevalent. Periodic investigations of Salmonella serotypes and antimicrobial resistance are needed.

Effects of CYP2C19 Genetic Polymorphisms on PK/PD Responses of Omeprazole in Korean Healthy Volunteers.

The aim of this study was to examine the effects of CYP2C19*2 and *3 genetic polymorphisms on omeprazole pharmacokinetic (PK) and pharmacodynamic (PD) responses. Twenty-four healthy Korean volunteers were enrolled and given 20 mg omeprazole orally once daily for 8 days. The genotypes of CYP2C19 single nucleotide polymorphisms (SNPs) (*2, *3, and *17) were screened. The plasma concentrations of omeprazole, omeprazole sulfone, and 5-hydroxy (5-OH) omeprazole were determined by liquid chromatography with tandem mass spectrometry (LC-MS/MS). The noncompartmental method was used for the determination of PK parameters. Change of mean pH and proportion (%) of time of gastric pH above 4.0 were estimated. The poor metabolizer (PM) group had the lowest metabolic ratio and exhibited the highest area under the curve (AUC) for omeprazole among the CYP2C19 phenotype groups. The PM group showed the greatest change of mean pH and the highest % time of gastric pH above 4.0. The relationship between AUC of omeprazole and % time of gastric pH above 4.0 was confirmed. The study demonstrates that CYP2C19*2 and *3 influence the PKs and PDs of omeprazole in Korean healthy volunteers.

DISTRIBUTION OF LEGIONELLA PNEUMOPHILA SEROGROUPS ISOLATED FROM WATER SYSTEMS OF PUBLIC FACILITIES IN BUSAN, SOUTH KOREA.

Legionella pneumophila is the major causes of legionellosis worldwide. The distribution of L. pneumophila was investigated in water systems of public facilities in Busan, South Korea during 2007 and 2013-2014. L. pneumophila was isolated from 8.3% of 3,055 samples, of which the highest isolation rate (49%) was from ships and the lowest 4% from fountains. Serogroups of L. pneumophila isolated in 2007 were distributed among serogroups (sgs) 1-7 with the exception of sg 4, while those of isolates during 2013 and 2014 included also 11 sgs ( 1, 2, 3, 4, 5, 6, 7, 8, 12, 13, 15). L. pneumophila sg 1 was predominated among isolates from fountains (75%), hotels (60%), buildings (44%), hospitals (38%), and public baths (37%), whereas sg 3 and sg 7 was the most prevalent from ships (46%) and factories (40%), respectively. The predominated serogroup of L. pneumophila isolates from hot and cooling tower water was sg 1 (35% and 46%, respectively), while from cold water was sg 3 (29%). These results should be useful for epidemiological surveys to identify sources of outbreaks of legionellosis in Busan, South Korea.

Mycobacterium avium paratuberculosis in wild boars in Korea.

Mycobacterium avium subsp. paratuberculosis (MAP) causes chronic infectious enteritis in various domestic and wild mammals and is widely distributed globally. Interspecies transmission has been frequently reported. We investigated the presence of MAP from December 2010 to March 2011 in blood and feces collected from 222 hunter-killed wild boars. We collected 197 serum and 180 fecal samples and examined them by culture, PCR, and enzyme-linked immunosorbent assay. We investigated the status of MAP infection and the MAP genotypes in the wild boar population of Korea by using IS900 PCR and IS1311-restriction endonuclease analysis typing. Of the 180 fecal samples cultured, MAP colonies were recovered from two. By PCR, 18 animals were positive for MAP and one serum sample had a strong humoral response to MAP. The PCR-positive DNA samples from the colonies and the feces samples were genotyped as "cattle type" and "bison type," which are major MAP genotypes infecting domestic species in Korea. Our study provides new information on mycobacterial infection among wild boars, and suggests that a more effective program should be developed to monitor mycobacterial infections in wild animal populations in Korea.

In vitro activities of antimicrobials against Brucella abortus isolates from cattle in Korea during 1998-2006.

In vitro activities of 13 antibiotics were assessed against 85 Brucella abortus isolates from naturally infected cattle in the Republic of Korea during 1998-2006, using broth microdilution test. Tetracyclines showed the most excellent activity against B. abortus, displaying MIC values of 0.5 µg/ml or below. In particular, minocycline showed the lowest MIC50/90 values (0.125/0.125 µg/ml) in this study. Among four fluoroquinolones tested, ciprofloxacin (MIC50/90, 0.5/1 µg/ml) and norfloxacin (MIC50/90, 8/8 µg/ml) had the most and the least activities, respectively. Gentamicin (MIC50/90, 1/1 µg/ml) was more effective than streptomycin, erythromycin, rifampin, and chloramphenicol (MIC50/90, 2/2 µg/ml).

Occurrence of virulence determinants in fecal Enterococcus faecalis isolated from pigs and chickens in Korea.

Forty-one Enterococcus faecalis (E. faecalis) isolates from feces of pigs and chickens in Korea were screened for the presence of virulence factors. Gelatinase activity (85.4%, 35/41) was the more commonly observed phenotype of virulence in E. faecalis, compared with hemolytic activity (12.2%, 5/41). Thirty-one of 35 (88.6%) gelatinase-positive E. faecalis isolates harbored the gelE and fsrABC genes. A gene encoding for the enterococcal surface protein (Esp) was detected in 24.4% (10/41) of the isolates. All betahemolysin- producing isolates harbored the esp gene.

The development of a selective medium for the Brucella abortus strains and its comparison with the currently recommended and used medium.

The Brucella spp. are fastidious and relatively slow-growing organisms. The isolation of such strains in a variety of specimens often requires the use of a selective medium to reduce or eliminate the growth of unexpected microorganisms. The modified Brucella selective (MBS) medium, which contains improved antibiotic mixtures, erythritol as the only carbon source, and neutral red as a pH indicator, showed good selectivity for the Brucella abortus strains, including the RB51 vaccine strain. Erythritol in the MBS medium was able to promote and/or recover the delayed growth of the B. abortus strains through the antibiotic mixtures. The Brucella colonies, which assumed a pinkish color at their central part, were easily differentiated from other organisms. The MBS medium also allows the isolation of the Brucella strains even in contaminated specimens and/or in specimens containing small numbers of viable organisms. Moreover, this medium can be applied to environmental samples for the isolation of the Brucella strains, and it can thus offer epidemiologic traceback sources for the dissemination or transfer of diseases. Therefore, the MBS medium can be applied as a useful tool of important control measures in the eradication programs.

A genetic comparison of Brucella abortus isolates from animals and humans by using an MLVA assay.

The MLVA assay is known to have a high ability to identify and discriminate Brucella species, so that it can be used as an epidemiological tool to discriminate Brucella isolates originating from restricted geographic sources. In this study, the genetic profiles of 38 B. abortus isolates from humans were analyzed and compared with genotypes from animal isolates in South Korea. As a result, it was found that they did not show high genetic diversity and were compacted. They were clustered together with animal isolates, showing a significant correlation to regional distributions. With its ability to prove a significant genetic correlation among B. abortus isolates from animals and humans in South Korea, the MLVA assay could be utilized as part of a program to control and eradicate brucellosis, one of the major zoonoses. This study represents the first data of genetic correlation of B. abortus isolates from humans and animals in South Korea.

Species distribution and resistance patterns to growth-promoting antimicrobials of enterococci isolated from pigs and chickens in Korea.

A total of 147 Enterococcus faecium and 165 Enterococcus faecalis isolates from fecal samples of chickens and pigs at slaughterhouses in Korea were tested for their resistance to 8 growth-promoting antimicrobials commonly used in animals and quinupristin and dalfopristin. Resistance to most antimicrobials was very common among both E. faecalis and E. faecium. In particular, E. faecalis showed almost no susceptibility to all the antimicrobials tested except penicillin and flavomycin, to which 1.4% and less than 24% showed resistance, respectively. Although the prevalence of resistance was lower than in E. faecalis, E. faecium showed relatively uniform resistance to all the agents tested. Among the antimicrobials tested, virginiamycin and penicillin were the most effective against E. faecium isolates: less than 31% and 41% showed resistance to those 2 antimicrobials, respectively. Penicillin was the only agent that showed relatively strong activity against both E. faecalis and E. faecium. Resistance observed in E. faecalis and E. faecium against most antimicrobials used for growth promotion was more prevalent in Korea than in European countries. The current study is the first report of resistance against feed additive antimicrobials in enterococcal isolates from livestock in Korea.

Application and evaluation of the MLVA typing assay for the Brucella abortus strains isolated in Korea.

BACKGROUND: A Brucella eradication program has been executed in Korea. To effectively prevent and control brucellosis, a molecular method for genetic identification and epidemiological trace-back must be established. As part of that, the MLVA typing assay was evaluated and applied to B. abortus isolates for analyzing the characteristics of the regional distribution and relationships of foreign isolates. RESULTS: A total of 177 isolates originating from 105 cattle farms for the period 1996 to 2008 were selected as representatives for the nine provinces of South Korea. A dendrogram of strain relatedness was constructed in accordance with the number of tandem repeat units for 17 loci so that it was possible to trace back in the restricted areas. Even in a farm contaminated by one source, however, the Brucella isolates showed an increase or decrease in one TRs copy number at some loci with high DI values. Moreover, those 17 loci was confirmed in stability via in-vitro and in-vivo passage, and found to be sufficiently stable markers that can readily identify the inoculated strain even if minor changes were detected. In the parsimony analysis with foreign Brucella isolates, domestic isolates were clustered distinctively, and located near the Central and Southern American isolates. CONCLUSION: The MLVA assay has enough discrimination power in the Brucella species level and can be utilized as a tool for the epidemiological trace-back of the B. abortus isolates. But it is important to consider that Brucella isolates may be capable of undergoing minor changes at some loci in the course of infection or in accordance with the changes of the host.

Use of rMPB70 protein and ESAT-6 peptide as antigens for comparison of the enzyme-linked immunosorbent, immunochromatographic, and latex bead agglutination assays for serodiagnosis of bovine tuberculosis.

Current assays used to detect Mycobacterium bovis infection lack accuracy, especially for recently infected animals, or are impractical for rapid field diagnostic applications. To overcome these limitations with serological assays, a synthetic peptide derived from early secretory antigenic target 6 (ESAT6-p) and a recombinant major secreted immunogenic protein (rMPB70) of M. bovis were used in an enzyme-linked immunosorbent assay (EIA), an immunochromatographic assay (ICGA), and a latex bead agglutination assay (LBAA). Sera from noninfected, M. bovis-infected, or M. avium subsp. paratuberculosis-infected (by natural and experimental routes) animals were evaluated. Receiver operating characteristic analysis comparing optical density values from the EIA with results of bacterial culture or skin test, the reference test, established suitable cutoff values for assessing sensitivity and specificity. The EIA and LBAA, respectively, had sensitivities of 98.6 and 94.8%, specificities of 98.5 and 92.6%, and kappa values of 0.97 and 0.88 with ESAT6-p. The EIA, ICGA, and LBAA, respectively, had sensitivities of 96.8, 83.0, and 86.7%, specificities of 90.1, 99.4, and 97.8%, and kappa values of 0.87, 0.85, and 0.83 with rMPB70. Examination of serial samples of sera collected from experimentally M. bovis-infected cattle and deer revealed that ESAT6-p-specific responses developed early after infection whereas responses to rMPB70 developed later in the course of disease. The advantage of the LBAA and ICGA as initial tests for multiple species is a rapid reaction obtained in 2 to 3 h by LBAA or 20 min by ICGA without species-specific secondary antibodies under field conditions, thus allowing immediate segregation of suspect animals for further testing before culling.