• Korean Journal of Clinical Laboratory Science
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• v.45 no.1
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• pp.21-25
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• 2013

Acinetobacter baumannii is an aerobic, gram-negative and glucose-non-fermenting bacterium, which has emerged as a serious opportunistic pathogen. Many clinical microbiology laboratories use the Vitek 2 system for the routine antimicrobial susceptibility testing process, including testing on A. baumannii isolates. However, in case of amikacin, it is now recommended to perform additional antimicrobial susceptibility testing for A. baumannii strains due to the relatively lower minimum inhibitory concentration (MIC) in the Vitek 2 system compared to conventional reference methods. In our study, we assessed MIC for amikacin susceptibility testing of A. baumannii isolates in the Vitek 2 system, the agar dilution, Etest, and disk diffusion method. We collected 40 gentamicin-resistant, A. baumannii strains (amikacin MIC by Vitek 2:${\leq}2{\mu}g/mL$, 2 isolates; $4{\mu}g/mL$, 34 isolates; $8{\mu}g/mL$, 4 isolates) from a University hospital and compared the Vitek 2 system to other reference methods for testing susceptibility to amikacin. The Vitek 2 system showed major errors in all of the 40 isolates, yielding a low MIC. The results of our study strongly suggested that the Vitek 2 system was not a reliable method to test the MICs of gentamicin; ranging from ${\geq}16{\mu}g/mL$ for amikacin susceptibility. Other tests, such as agar dilution, Etest, or disk diffusion methods, should be paralleled to determine the MIC of amikacin in A. baumannii.

• Journal of Food Hygiene and Safety
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• v.30 no.3
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• pp.281-288
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• 2015

Vibrio is a genus of Gram-negative, curved, halophilic, and non-spore-forming bacteria. Some of the Vibrio species, such as V. cholerae and V. parahaemolyticus, often contaminate seafood products and occasionally cause human diseases when the seafood products are ingested. A total of 24 Vibrio strains were isolated from shrimp samples on Thiosulphate citrate bile salt sucrose (TCBS) media in this study. All of the 24 isolates were confirmed to belong to the genus Vibrio by using 16S rRNA gene sequence analyses. Vitek 2 system and species-specific polymerase chain reaction (PCR) methods were used to further identify a total of 29 Vibrio strains at the species level, including the 24 shrimp Vibrio isolates and five Vibrio reference strains. The specificities of the two methods to identify Vibrio strains at the species level were compared in this study. The species-specific PCR method was designed to detect five different Vibrio species, such as Vibrio cholerae, Vibrio parahaemolyticus, Vibrio vulnificus, Vibrio alginolyticus, and Vibrio mimicus. From the 24 Vibrio shrimp isolates, the Vitek 2 system method could identify 15 (62.5%) strains as Vibrio species and 7 (29.2%) strains as non-Vibrio species, but could not identify the rest 2 (8.3%) strains. But species-specific PCR method could identify 16 (66.7%) strains as Vibrio species and could not identify the rest 8 (33.3%) strains. Among the 24 Vibrio shrimp strains, these two methods could unanimously identify 7 (7/24, 29.2%) strains (2 V. parahaemolyticus, 4 V. alginolyticus, and 1 V. mimicus). Considering that such different identification results were obtained using the two different methods in this study, identification method for Vibrio species must be carefully chosen.

• Korean Journal of Clinical Laboratory Science
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• v.49 no.3
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• pp.279-284
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• 2017

The results of rapid antimicrobial susceptibility test (AST) in blood cultures were obtained by inoculating the bacteria directly into the VITEK MS and the VITEK 2 systems without subculturing in the blood culture positive medium. The obtained results were compared with the results using a standard method to evaluate their reliability and accuracy. The direct AST results in blood culture positive specimens were 97.9% (1,936/1,978), consistent with the standard AST results. Gram-positive bacteria showed a concordance rate of 97.2% (1,051/1,081), a very major error rate of 0.5% (5/1,081), a major error rate of 0.1% (1/1,081), and a minor error rate of 2.2% (24/1,081). Staphylococcus epidermidis was the main cause of discordance, and gentamicin (N=9) and fusidic acid (N=8) showed high errors. The overall concordance rate and minor error among the Gram-negative bacteria were 98.6% (885/897) and 1.4% (12/897), respectively. Escherichia coli and Pseudomonas aeruginosa were the major causative bacteria of Gram-negative bacteria. Among them, amoxicillin/clavulanic acid (N=3) showed high error. Direct AST met the CLSI criteria and shortened the reporting time by 24 hours; however, we found that there was a need to perform an addition test via disk diffusion for antimicrobials with very large errors. These results suggest that the method of direct AST in blood culture positive medium may be very useful in efficiently treating patients.

• Journal of Microbiology and Biotechnology
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• v.26 no.12
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• pp.2206-2213
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• 2016

Recently, several studies have revealed that commercial microbial identification systems do not accurately identify the uncommon causative species of candidiasis, including Candida famata, Meyerozyma guilliermondii, and C. auris. We investigated the accuracy of species-level identification in a collection of clinical isolates previously identified as C. famata (N = 38), C. lusitaniae (N = 1 2), and M. guilliermondii (N = 5) by the Vitek 2 system. All 55 isolates were re-analyzed by the Phoenix system (Becton Dickinson Diagnostics), two matrix-assisted laser desorption ionization-time of flight mass spectrometry analyzers (a Vitek MS and a Bruker Biotyper), and by sequencing of internal transcribed spacer (ITS) regions or 26S rRNA gene D1/D2 domains. Among 38 isolates previously identified as C. famata by the Vitek 2 system, the majority (27/38 isolates, 71.1%) were identified as C. tropicalis (20 isolates) or C. albicans (7 isolates) by ITS sequencing, and none was identified as C. famata. Among 20 isolates that were identified as C. tropicalis, 17 (85%) were isolated from urine. The two isolates that were identified as C. auris by ITS sequencing originated from ear discharge. The Phoenix system did not accurately identify C. lusitaniae, C. krusei, or C. auris. The correct identification rate for 55 isolates was 92.7% (51/55 isolates) for the Vitek MS and 94.6% (52/55 isolates) for the Bruker Biotyper, as compared with results from ITS sequencing. These results suggest that C. famata is very rare in Korea, and that the possibility of misidentification should be noted when an uncommon Candida species is identified.

• Korean Journal of Clinical Laboratory Science
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• v.49 no.4
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• pp.401-406
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• 2017

In this study, using the VITEK 2 system, 74 samples (22.6%) out of 327 specimens were identified by the growth of Enterococcosel media (EV6 agar) supplemented with $6{\mu}g/mL$ of vancomycin. Enterococcus faecium was identified as 55 strains (74.3%), Enterococcus casseliflavus as 2 strains (2.7%), Enterococcus avium as 1 strain (1.4%), and Enterococcus gallinarum as 16 strains (21.6%). Among the 55 phenotypes of Enterococcus faecium, 42 (76.4%), 9 (16.4%), and 4 strains (7.3%) showed the vanA, vanB, and vanC phenotype, respectively. The 16 strains of Enterococcus gallinarum and 2 strains of Enterococcus casseliflavus showed the vanC phenotype and the 1 strain of Enterococcus avium had the vanB phenotype. The one strain of Enterococcus faecium propagated only in EV4 and was susceptible to both vancomycin and teicoplanin according to the antimicrobial susceptibility test using the VITEK 2 system. The vancomycin resistance phenotype gene was not detected by PCR. A total of 327 specimens were cultured in Enterococcosel broth supplemented with $6{\mu}g/mL$ of vancomycin (EV6 broth), and 120 strains (36.7%) were isolated. These 120 strains were subjected to vancomycin resistant genotyping by a multiplex real-time polymerase chain reaction and 51 strains (42.5%) showed vanA; 5 strains (4.2%) showed vanA and vanC; and 18 strains (15%) showed vanC. Vancomycin resistance genotypes were not detected in the remaining 46 strains (38.3%).

• Journal of Microbiology
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• v.40 no.2
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• pp.170-172
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• 2002

To determine the occurrence of vancomycin-resistant Enterococci in a raw milk sample, raw milk samples were examined for a period of 6 months. Enterococci were isolated directly from Enterococcal selective agar plates supplemented with 2 mg of vancomycin per liter, Nineteen strains were selected and identified by applying the Vitek system. To determine resistance patterns, 19 isolates were tested with vancomycin and teicoplanin. Vancomycin-resistant Enterococci were genotyped by using a PCR analysis and 5 out of 19 isolates were of the VanC type.

• Safety and Health at Work
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• v.11 no.4
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• pp.517-525
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• 2020

Background: The study was planned to show the status of indoor microorganisms and the status of the reduction device in the military dog clinic. Methods: Airborne microbes were analyzed according to the number of daily patient canines. For identification of bacteria, sampled bacteria was identified using VITEK^®2 and molecular method. The status of indoor microorganisms according to the operation of the ventilation system was analyzed. Results: Airborne bacteria and fungi concentrations were 1000.6 ± 800.7 CFU/m³ and 324.7 ± 245.8 CFU/m³. In the analysis using automated identification system, based on fluorescence biochemical test, VITEK^®2, mainly human pathogenic bacteria were identified. The three most frequently isolated genera were Kocuria (26.6%), Staphylococcus (24.48%), and Granulicatella (12.7%). The results analyzed by molecular method were detected in the order of Kocuria (22.6%), followed by Macrococcus (18.1%), Glutamicibacter (11.1%), and so on. When the ventilation system was operated appropriately, the airborne bacteria and fungi level were significantly decreased. Conclusion: Airborne bacteria in the clinic tend to increase with the number of canines. Human pathogenic bacteria were mainly detected in VITEK^®2, and relatively various bacteria were detected in molecular analysis. A decrease in the level of bacteria and fungi was observed with proper operation of the ventilation system.

• Korean Journal of Clinical Laboratory Science
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• v.49 no.4
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• pp.413-419
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• 2017

Four imipenem-resistant bacteria were isolated from the clinical specimens of a patient with pneumonia. To identify the isolates, we used the GN card of Vitek II system and performed a phylogenetic analysis based on 16S rRNA gene sequence. The isolates were identified as P. aeruginosa (2 strains), P. monteilii (1 strain), and P. putida (1 strain), and were tested for antibiotic resistance after determining the MIC of imipenem to be $${\geq_-}8{\mu}g/mL$$ using the AST-N225 card of Vitek II system. The imipenem-resistant genotypes were determined using PCR products amplified using specific ${\beta}-Lactamase$ gene primers. The MBL gene was identified in all four isolates. One strain of P. aeruginosa exhibited the VIM and SHV-1 type genes, while the other strain exhibited both VIM and OXA group II genes. According to the antimicrobial susceptibility test, the bacteria were more susceptible to amikacin than other antibiotics. DNA fingerprint analysis using ERIC-PCR to analyze the epidemiological relationship between strains estimated that both the P. aeruginosa isolates were similar, but exhibited different DNA band types. It is uncommon to find four strains of imipenem-resistant bacteria with different DNA band types in a single patient.

• Korean Journal of Clinical Laboratory Science
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• v.49 no.4
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• pp.407-412
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• 2017

The aim of this study was to shorten the time required for subculture and bacterial identification and obtain a simple and rapid identification method for new test methods for bloodstream infections. The following results were obtained using a mass spectrometer. In Vitek 2, 208 (81.8%) cases were well-identified and 45 isolates were not identified in blood cultures. Among 208 cases, 146 (57.5%) were Gram positive bacteria and 108 (42.5%) were Gram negative bacteria. In total, 233 were identified to the species level and 21 were identified to the genus level. The identification error was found to be Propionibacterium acnes as Clostridium bifermentans. The accuracy of Enterobacteriaceae, glucose non-fermentative bacilli (GNFB), and staphylococci were 81/83 (97.6%), 12/15 (80.0%), and 72/85 (84.7%), respectively. The concordance rate of Vitek 2 and Vitek MS by the direct method was 81.8% and 45 isolates were not identified. Most of the unidentified bacteria were Gram positive bacteria (N=37). The Gram positive bacteria were streptococci (14), coagulase-negative staphylococci (CNS) (11), enterococci (3), Staphylococcus aureus (2), Micrococcus spp. (2), Bacillus spp. (2) and Actinomyces odontolyticus, Finegoldia magna, and Peptostreptococcus spp. The results reporting time was reduced to 24~72 hours compared to the conventional method. The rate of identification of the aerobic and anaerobic cultures was similar, but the use of an anaerobic culture did not require a dissolution process, which could shorten the sample preparation time. These results suggest that the method of direct identification in blood cultures is very useful for the treatment of patients. In further studies, it might be necessary to further improve the method for identifying streptococci and CNS, which were lacking in accuracy in this study.

• Journal of Animal Environmental Science
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• v.21 no.3
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• pp.83-92
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• 2015

An attempt to produce more pigs in limited spaces inevitably generalized concentrated feeding operation (CFO). As concentrated pig production practice expanded, concerns on environmental issues grow concurrently. Since odor is the concerned most among those, we attempted to develop means to tackle odor emission from livestock operations. Previously, we excavated few microorganisms from pig manure and, one of them, Bacillus licheniformis was particularly useful to handle odor problem. In this study, we conducted our investigation to further characterize Bacillus licheniformis. Strain identification was conducted using Vitek 2 compact, and the optimal temperature and pH conditions to growth B. licheniformis were searched for by analyzing turbidity on O.D 600 nm. Results of this study can be summarized as these, (1) it was re-verified that the bacterial strain that purified from pig manure was, in fact, Bacillus licheniformis, (2) the bacterial growth was highest when the temperature was kept at $30^{\circ}C$, also (3) growth rate was dependent on media pH as it was high at neutral (6, 7 and 8) but dropped when it was diverged from neutral (4, 5, 9 and 10), and (4) regarding ammonia removal efficiency, B. licheniformis recorded 64% effectiveness after 48 h incubation and reached its highest (80%) at 72 h.