• Korean Journal of Veterinary Research
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• v.48 no.2
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• pp.139-143
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• 2008

We report here two cases of Rhodococcus (R.) equi-causing pneumonia of Throughbred foals in Gyeonggi-do in 2006. R. equi was isolated from the lung lesions of the dead foals, and from the feces and soils on the farms where the clinical cases of R. equi infection occurred. The isolates were characterized by biochemical properties, polymerase chain reaction for vapA gene and antimicrobial susceptibility. In drug susceptibility test, erythromycin, gentamycin, vancomycin, and rifampin were found to be the most susceptible for all isolates. These results suggest that R. equi pneumonia may be endemic in the horse-breeding farms in inland Korea and the farm environment may be widely contaminated with virulent R. equi.

• Korean Journal of Veterinary Service
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• v.43 no.1
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• pp.31-37
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• 2020

Clostridial bacteria are zoonotic agents, which cause severe necrotizing enteritis, pseudo-membrane colitis, enterotoxemia to both humans and animals. The objective of this study was to monitor the antibiotic resistance of Clostridium isolates on clinical specimens from wild animals in Seoul zoo for 5 years. Clostridium isolates were verified by using Vitek2 compact machine. Antibiotic susceptibility was assessed by antibiotic disc diffusion test, which was followed by Kirby-Bauer disc diffusion test method. The frequency of Antimicrobial resistance of Clostridium isolate was the greatest in gentamicin (87%), then in order of amikacin (80%). There were 55.6% of Clostridium isolates showed multiple drug resistance (MDR). These results showed that a lot of Clostridial bacteria from wild animals in Seoul zoo were acquired antibiotic resistance. Because of the wild animal's aggressive manner, it has been hard to collect clinical samples from wild animals in a zoo to exam antibiotic susceptibility. For these reasons, empirical use of antibiotics has been performed in frequently. It may cause to increase the emergence of antibiotic resistance bacteria. In addition, the antibiotic resistance bacteria from zoo animals can be spread to other wild animals which inhabit around the zoo. Therefore, regular monitoring of antibiotic resistance Clostridial bacteria is important to protect animals and humans from Clostridial diseases.

• Korean Journal of Veterinary Research
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• v.41 no.2
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• pp.173-176
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• 2001

The present study was conducted to examine the drug susceptibility of 57 strains of Microsporum canis isolated from dogs with dermatitis in Taegu, 1999. Antifungal susceptibility test was performed by the microdilution method, using 7 antifungal drugs as follows: itraconazole(I), terbinafine(T), ketoconazole(K), griseofulvin(G), amphotericin B(A), flucytosine(5-Fc)(F), tolnaftate(To). All tester strains of M canis were highly susceptible to T, I, K and To(geometric mean $MICs{\leq}0.007{\sim}0.155{\mu}g/ml$), while those were lowly susceptible to G, A and F(geometric mean MICs $0.285{\sim}26.430{\mu}g/ml$).

• Tuberculosis and Respiratory Diseases
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• v.84 no.3
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• pp.237-244
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• 2021

Background: The emergence of drug-resistant tuberculosis (TB), is a major menace to cast off TB worldwide. Line probe assay (LPA; GenoType MTBDRplus ver. 2) and Xpert MTB/RIF assays are two rapid molecular TB detection/diagnostic tests. To compare the performance of LPA and Xpert MTB/RIF assay for early diagnosis of rifampicin-resistant (RR) TB in acid-fast bacillus (AFB) smear-positive and negative sputum samples. Methods: A total 576 presumptive AFB patients were selected and subjected to AFB microscopy, Xpert MTB/RIF assay and recent version of LPA (GenoType MTBDRplus assay version 2) tests directly on sputum samples. Results were compared with phenotypic culture and drug susceptibility testing (DST). DNA sequencing was performed with rpoB gene for samples with discordant rifampicin susceptibility results. Results: Among culture-positive samples, Xpert MTB/RIF assay detected Mycobacterium tuberculosis (Mtb) in 97.3% (364/374) of AFB smear-positive samples and 76.5% (13/17) among smear-negative samples, and the corresponding values for LPA test (valid results with Mtb control band) were 97.9% (366/374) and 58.8% (10/17), respectively. For detection of RR among Mtb positive molecular results, the sensitivity of Xpert MTB/RIF assay and LPA (after resolving discordant phenotypic DST results with DNA sequencing) were found to be 96% and 99%, respectively. Whereas, specificity of both test for detecting RR were found to be 99%. Conclusion: We conclude that although Xpert MTB/RIF assay is comparatively superior to LPA in detecting Mtb among AFB smear-negative pulmonary TB. However, both tests are equally efficient in early diagnosis of AFB smear-positive presumptive RR-TB patients.

• Korean Journal of Veterinary Research
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• v.39 no.2
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• pp.376-382
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• 1999

A methicillin-resistant Staphylococcus aureus (MRSA) isolate was recovered from a 9-month-old female Shih-Tzu dog with canine distemper virus infection. We performed in vitro antimicrobial susceptibility test to determine the most effective antimicrobial drug against the isolate and thus, to emphasize its potential clinical importance in animal practices. Isolate was confirmed MRSA by oxacillin agar screening test. The isolate was fully resistant to all $\beta$-lactam antibiotics and was susceptible to glycopeptides. Of the other antibiotics, mupirocin, TMP/SMZ (trimethoprim-sulfamethoxazole), and chloramphenicol showed inhibitory effect at the concentration of 4x MIC. The MICs ranged 0.25->$128{\mu}g/ml$, and MBCs ranged 0.5->$128{\mu}g/ml$. The combined TMP/SMZ with cefamandole or novobiocin showed synergistic effect, whereas the combination of novobiocin plus cefamandole or teicoplanin resulted in antagonistic effects. Although MRSA in animals so far has been reported in the geographically limited countries, at least theoretically, it could be occurred in the future more frequently through either human or animal origin. The use of this combination may be of value in this situation. As with all antimicrobial agents, inappropriate or unnecessarily prolonged therapy may contribute to the emergence of resistance strains and loss of efficacy.

• Korean Journal of Clinical Laboratory Science
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• v.54 no.2
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• pp.125-132
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• 2022

The prevalence of multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) are increasing. We analyzed the patterns of drug resistance and tracking period days of acquiring anti-mycobacterial resistance. From January 2010 to December 2019, drug susceptibility tests (DST) were performed by the absolute concentration method using the Löwenstein-Jensen solid medium and pyrazinamidase activity test (to assess pyrazinamide resistance) in samples from patients who were referred to the Green Cross Laboratories in Yongin. Among the cases that showed resistance to one or more anti-tuberculosis drugs, 55 patients (33.1%) were resistant to isoniazid (INH) at the time of initial referral, and the rates for the development of resistant anti-tuberculosis drugs were ethambutol (EMB) (26.6%), rifampicin (RFP) (21.9%), quinolones (QUI) (21.9%) and pyrazinamide (PZA) (10.9%), in that order. In the cases sensitive to all 10 anti-tuberculosis drugs initially, the development of resistance to INH was the most frequent, seen in 43 patients (7.2%). The average follow-up period was 435.6 days, and the resistance development was observed in the order of INH (7.2%), RFP (3.9%), SM (1.9%), QUI (0.7%), amikacin (AMK) (0.5%), and EMB (0.5%). The conversion of susceptible strains to resistant strains is an important warning sign for the patient, especially in cases of conversion to MDR or XDR. This information would be helpful for improving patient care during TB treatment.

• Tuberculosis and Respiratory Diseases
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• v.59 no.3
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• pp.266-271
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• 2005

Background : Ethambutol(EMB) is one of the first-line drugs included in short-course anti-tuberculosis therapy. The point mutations in embB gene have been speculated to be associated EMB resistance. However, detection of embB mutations at these positions have been observed in both EMB-susceptible isolates; thus, it remains controversial whether these mutations are associated with EMB resistance Methods : The 36 M. tuberculosis isolates were selected from clinical isolates which tested susceptible to EMB and resistant to at least one drug. DNA extracted from the isolates was analyzed by amplifying embB gene. The PCR products were purified and directly sequenced. We reviewed the history of past drug susceptibility test results. Results : Out of 36 EMB-susceptible strains, 3 strains (8.3%) had a mutation in codon 306 or 406 of the embB gene. These three strains had at least isoniazid resistance. They grew at 1.0 mcg/ml of EMB in Lowenstein-Jensen media. The patients of the strains were continuously smear-positive for over 3 years despite taking TB therapy. One strain had been EMB-resistant in past drug susceptibility tests. Conclusion : EMB-susceptible strains containing embB mutation may be caused by decreased viability in vitro test not by itself.

• Tuberculosis and Respiratory Diseases
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• v.86 no.1
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• pp.47-56
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• 2023

Background: There is a global increase in isolation of nontuberculous mycobacteria (NTM). The aim of the study was to analyze longitudinal trends of NTM identification and pattern of antimicrobial susceptibility testing. Methods: NTM recovery rates, distribution of NTM species identification, and antimicrobial susceptibility pattern of NTM at Pusan National University Yangsan Hospital between January 2016 and December 2020 were retrospectively analyzed. Results: A total of 52,456 specimens from 21,264 patients were submitted for mycobacterial culture, of which 2,521 from 1,410 patients were NTM positive over five years (January 2016 to December 2020). NTM isolation showed an increasing trend from 2016 to 2020 (p<0.001, test for trend) mainly caused by Mycobacterium avium complex. The vast majority of M. avium complex were susceptible to key agents clarithromycin and amikacin. For Mycobacterium kansasii, resistance to rifampin and clarithromycin is rare. Amikacin was the most effective drug against Mycobacterium abscessus subspecies abscessus and Mycobacterium subspecies massiliense. Most of M. subspecies massiliense were susceptible to clarithromycin, while the majority of M. abscessus subspecies abscessus were resistant to clarithromycin (p<0.001). Conclusion: There was an increasing trend of NTM isolation in our hospital. Resistance to key drugs was uncommon for most NTM species except for M. abscessus subspecies abscessus against clarithromycin.

• The Journal of the Korean Society for Microbiology
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• v.13 no.1
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• pp.43-48
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• 1978

The difference in antimicrobial susceptibility of multiply drug-resistant Salmonella typhi by the methods of test was tested against chloramphenicol(Cm), tetracycline(Tc), ampicillin(Ap), kanamycin(Km), and rifampicin(Rif), and the results were compared by the minimum inhibitory concentration(MIC). No appreciable difference was noted between MICs of Cm, Tc, and Rif measured by agar plate dilution(plate) method and broth dilution(broth) method. However, MICs of Km to about a half of test strains were 4 to 8-fold higher by broth method than plate method, and MICs of Ap by broth method were also a little higher than plate method in some strains. Cm and Rif were bacteriostatic rather than bactericidal to the most of test strains in high concentrations. Tc, Ap and Km were exclusively bactericidal to the test strains.

• Korean Journal of Veterinary Service
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• v.21 no.4
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• pp.451-465
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• 1998

The present study was carried out to investigate the prevalence of brucellosis in Kyungbuk area for the 3 years from 1966 to 1998. Collective milk samples were routinely screened to detect positive farms by using the milk ring test(MRT), and serum agglutination test was performed to detect sero-positive individuals in the MRT positive farms. Attempt were made to isolate the causative organismas from slaughtered sero-positive reactors and some biochemical and polymerase chain reation characters of the isolates were also made to identify the organisms. Seroprevalence to brucellosis in peoples who are close contact with infected dairy herds was also investigated. Brucellosis of dairy cattle was rare before 1997, but has been broken more frequently since early 1998. By the MRT for dairy herds, positive rate was gradually increased every year : 0.6% in 1996, 1.5% in 1997, 3.9% in 1998. Among 262 MRT-positive herds, only 21 herds(8.0%) showed positive brucellosis in serological test. The isolation rates of Brucella sp from tested materials were 51.2% in supramammary glands, 39.5% in milks, and 50.0% in pulmonary Iymphnode, respectively. Isolated strain and biotype were Brucella(B) arbortus biotype 1 in 26 heads, and were B suis biotype 1 in 2 heads. Isolated strain and vaccine strain were very similar in their colony morphology and staining. In drug susceptibility, isolated stains(B abortus) and vaccine strain(B abortus RB-51) were sensitive to ampicillin, gentamycin, kanamycin, neomycin, penicillin, streptomycin, and to tetracycline, but resistant to erythromycin. In the PCR, field strains reacted to BA and IS711 primers, and vaccine strain reacted to BA, IS711, and RB5l primers. In the plate agglutination test of 96 sera of human contacted with animals, serum antibody titer detected 1 : 100 in one person, 1 : 200 in one, and below 1 : 25 in the others.