Young Kil Park

Clinical Significance of Differentiation of Mycobacterium massiliense from Mycobacterium abscessus

RATIONALE Mycobacterium massiliense has been recognized as a separate species from Mycobacterium abscessus; however, little is known regarding the clinical impact of this differentiation. OBJECTIVES To compare clinical features and treatment outcomes between patients with M. abscessus lung disease and those with M. massiliense lung disease. METHODS We performed molecular identification of stored clinical isolates of M. abscessus complex and compared clinical characteristics and treatment outcomes between 64 patients with M. abscessus lung disease and 81 patients with M. massiliense lung disease. MEASUREMENTS AND MAIN RESULTS The clinical and radiographic manifestations of disease caused by each species were similar. Standardized combination antibiotic therapy, including a clarithromycin-containing regimen in combination with an initial 4-week course of cefoxitin and amikacin, was given to 57 patients (24 with M. abscessus and 33 with M. massiliense) for more than 12 months. The proportion of patients with sputum conversion and maintenance of negative sputum cultures was higher in patients with M. massiliense infection (88%) than in those with M. abscessus infection (25%; P < 0.001). Inducible resistance to clarithromycin (minimal inhibitory concentrations ≥ 32 μg/ml) was found in all tested M. abscessus isolates (n = 19), but in none of the M. massiliense isolates (n = 28). CONCLUSIONS Treatment response rates to combination antibiotic therapy including clarithromycin were much higher in patients with M. massiliense lung disease than in those with M. abscessus lung disease. The inducible resistance to clarithromycin could explain the lack of efficacy of clarithromycin-containing antibiotic therapy against M. abscessus lung disease.

Antibiotic treatment of Mycobacterium abscessus lung disease: a retrospective analysis of 65 patients.

RATIONALE The optimal therapeutic regimen and duration of treatment for Mycobacterium abscessus lung disease is not well established. OBJECTIVES To assess the efficacy of a standardized combination antibiotic therapy for the treatment of M. abscessus lung disease. METHODS Sixty-five patients (11 males, 55 females, median age 55 yr) with M. abscessus lung disease were treated with clarithromycin, ciprofloxacin, and doxycycline, together with an initial regimen of amikacin and cefoxitin for the first 4 weeks of hospitalization. MEASUREMENTS AND MAIN RESULTS Treatment response rates were 83% for symptoms and 74% for high-resolution computed tomography. Sputum conversion and maintenance of negative sputum cultures for more than 12 months was achieved in 38 (58%) patients. These rates were significantly lower in patients whose isolates were resistant to clarithromycin (17%, 2/12) compared with those whose isolates were susceptible or intermediate to clarithromycin (64%, 21/33; P = 0.007). Neutropenia and thrombocytopenia associated with cefoxitin developed in 33 (51%) and 4 (6%) patients, respectively. Drug-induced hepatotoxicity occurred in 10 (15%) patients. Because of these adverse reactions, cefoxitin was discontinued in 39 (60%) patients after treatment for a median of 22 days. CONCLUSIONS Standardized combination antibiotic therapy was moderately effective in treating M. abscessus lung disease. However, frequent adverse reactions and the potential for long-duration hospitalization are important problems that remain to be solved.

Spread of nontuberculous mycobacteria from 1993 to 2006 in Koreans

In Korea, the prevalence of nontuberculous mycobacterial (NTM) pulmonary disease has risen, observed primarily in immunocompetent patients with or without preexisting lung disease. The purpose of this study was to determine the frequency of various species of NTM isolates from respiratory specimens in a single institution over a 14‐year period in Korea. All samples referred to our reference laboratory over a 14‐year period in Korea were analyzed. From 1993 to 2000 our laboratory used conventional NTM identification methods, and from 2001 we adapted PCR‐restrictionfragment length polymorphism analysis(PRA). A total of 17,915 isolates were collected from 1993 to 2006. The most frequently isolated organisms were M. avium complex (n=11,705, 65%), M. abscessus (n=2,076, 11.59%), M. fortuitum complex (n=1,279, 7.14%). M. chelonae complex (n=1,134, 6.33%), M. kansasii (n=762, 4.25%), M. szulgai (n=139, 0.78%), M. celatum (n=87, 0.49%), M. scrofulaceum (n=18, 0.10%) and M. marium (n=11, 0.06%). J. Clin. Lab. Anal. 22:415–420, 2008.

Characterization of mutations in multi- and extensive drug resistance among strains of Mycobacterium tuberculosis clinical isolates in Republic of Korea

In order to characterize molecular mechanisms of first- and second-line drug resistance in Mycobacterium tuberculosis and to evaluate the use of molecular markers of resistance, we analyzed 62 multidrug-resistant, 100 extensively drug-resistant, and 30 pan-susceptible isolates from Korean tuberculosis patients. Twelve genome regions associated with drug resistance, including katG, ahpC, and inhA promoter for isoniazid (INH); embB for ethambutol (EMB), rpoB for rifampin (RIF), pncA for pyrazinamide (PZA), gyrA for fluoroquinolones; rpsL, gidB, and rrs for streptomycin; rrs and eis for kanamycin (KM); rrs and tylA for capreomycin (CAP); and rrs for amikacin (AMK) were amplified simultaneously by polymerase chain reaction, and the DNA sequences were determined. We found mutations in 140 of 160 INH-resistant isolates (87.5%), 159 of 162 RIF-resistant isolates (98.15%), 127 of 143 EMB-resistant isolates (88.8%), 108 of 123 ofloxacin-resistant isolates (87.8%), and 107 of 122 PZA-resistant isolates (87.7%); 43 of 51 STM-resistant isolates (84.3%), 15 of 17 KM-resistant isolates (88.2%), and 14 of 15 (AMK and CAP)-resistant isolates (93.3%) had mutations related to specific drug resistance. In addition, the sequence analyses of the study revealed many novel mutations involving these loci. This result suggests that mutations in the rpoB531, katGSer315Thr, and C-15T in the inhA promoter region, and gyrA94, embB306, pncA159, rpsL43, and A1401G in the rrs gene could serve as useful markers for rapid detection of resistance profile in the clinical isolates of M. tuberculosis in Korea, with potentials for the new therapeutic benefits in actual clinical practice.

In Vitro Antimicrobial Susceptibility of Mycobacterium abscessus in Korea

Mycobacterium abscessus is the second most common etiology of pulmonary disease caused by nontuberculous mycobacteria in Korea. Although antimicrobial susceptibility tests are important for appropriate patient management in M. abscessus lung disease, the tests have never been investigated in Korea. Seventy-four isolates of M. abscessus recovered from patient respiratory samples were tested against eight antimicrobial agents following the guidelines set forth by the National Committee for Clinical Laboratory Standards. Of the parenteral antibiotics, amikacin (99%, 73/74) and cefoxitin (99%, 73/74) were active against most isolates. Imipenem (55%, 36/66) and tobramycin (36%, 27/74) had activity against moderate number of isolates. Of the oral antibiotics, clarithromycin (91%, 67/74) was active against the majority of isolates. Moxifloxacin (73%, 54/74) and ciprofloxacin (57%, 42/74) had activity against a moderate number of isolates. Doxycycline was the least active, inhibiting only 7% (5/74) of isolates. In conclusion, the variations in susceptibility within M. abscessus isolates to currently available antimicrobials suggest that the antimicrobial susceptibilities of any clinically significant M. abscessus isolate be needed individually.

Drug Resistance Rates of Mycobacterium tuberculosis at a Private Referral Center in Korea

The goals of this study were to identify first-line drug resistance in new and previously treated tuberculosis (TB) cases and to determine risk factors for multidrug-resistant TB (MDR-TB) at a private referral center in Korea. All patients with culture-confirmed pulmonary TB over a 2-yr period between July 2002 and June 2004 were prospectively included in this study. In total, 637 patients were included; 512 (80.4%) were new cases, and 125 (19.6%) were previously treated cases. Resistance to at least one first-line drug was identified in 11.7% of new cases and 41.6% of previously treated cases. MDR-TB was detected in 3.9% of new cases and 27.2% of previously treated cases. The proportion of extensively drug-resistant TB among MDR-TB patients was 16.7% (9/54). Factors associated with MDR-TB included age under 45 yr, previous TB treatment, and the presence of cavitation on chest radiography. Rates of first-line drug resistance are high, particularly in previously treated patients, in the private sector in Korea. This underscores the need for an improved control program, coupled with early diagnosis of MDR-TB, to reduce the spread and development of resistance.

Comparison of a Conventional Antimicrobial Susceptibility Assay to an Oligonucleotide Chip System for Detection of Drug Resistance in Mycobacterium tuberculosis Isolates

ABSTRACT An oligonucleotide chip (Combichip Mycobacteria chip) detecting specific mutations in the rpoB, katG, and inhA genes of Mycobacterium tuberculosis was compared with conventional antimicrobial susceptibility results. The probes detecting drug resistance were as follows: 7 wild-type and 13 mutant probes for rifampin and 2 wild-type and 3 mutant probes for isoniazid. Target DNA of M. tuberculosis was amplified by PCR, followed by hybridization and scanning. Direct sequencing was performed to verify the results of the oligonucleotide chip. One-hundred seven of 115 rifampin-resistant strains (93%) had mutations in the rpoB gene. Eighty-five of 119 isoniazid-resistant strains (71%) had mutations in the katG gene or inhA gene. The diagnostic oligonucleotide chip with mutation-specific probes is a reliable and useful tool for the rapid and accurate diagnosis of resistance against rifampin and isoniazid in M. tuberculosis isolates.

The Interval Between Initiation of Anti-tuberculosis Treatment in Patients with Culture-positive Pulmonary Tuberculosis and Receipt of Drug-susceptibility Test Results

Although mycobacterial culture and the subsequent drug-susceptibility test (DST) for anti-tuberculosis (TB) drugs take several months to complete using solid media, there are no reports on the turnaround times of these tests under clinical conditions. The aim of this study was to determine the interval between initiation of anti-TB treatment and receipt of DST requested at an outpatient clinic. We prospectively enrolled patients with culture-positive pulmonary TB at Seoul National University Hospital from September 2002 to December 2004. Patients were followed up monthly. Mycobacterial cultures were done using Ogawa media at Seoul National University Hospital. DST were performed at the Korean Institute of Tuberculosis. Of the 104 patients enrolled, 54 were male. The median age was 41 yr. The median interval from initiation of anti-TB treatment to receipt of mycobacterial culture results by clinicians was 37 days (range, 0-89 days). The median interval from initiation of treatment to confirmation of DST by requesting clinicians was 80.5 days (range, 28-145 days). Clinicians only received the results of DST more than two months after initiation of treatment when they followed up patients monthly and mycobacterial culture was performed using solid media.

The Drug Resistance Profile of Mycobacterium abscessus Group Strains from Korea

Background Bacteria of the Mycobacterium abscessus group are the second most common pathogens responsible for lung disease caused by nontuberculous mycobacteria in Korea. There is still a lack of studies investigating the genetic mechanisms involved in M. abscessus resistance to antibiotics other than clarithromycin. This study investigated the characteristics of drug resistance exhibited by M. abscessus clinical isolates from Korea. Methods We performed drug susceptibility testing for a total of 404 M. abscessus clinical strains. Subspecies were differentiated by molecular biological methods and examined for mutations in drug resistance-related genes. Results Of the 404 strains examined, 202 (50.00%), 199 (49.26%), and 3 (0.74%) strains were identified as M. abscessus, M. massiliense, and M. bolletii, respectively. Of the 152 clarithromycin-resistant strains, 6 possessed rrl mutations, while 4 of the 30 amikacin-resistant strains contained rrs mutations, and 5 of the 114 quinolone-resistant strains had gyr mutations. All mutant strains had high minimal inhibitory concentration values for the antibiotics. Conclusions Our results showed the distribution of the strains with mutations in drug resistance-related genes was low in the M. abscessus group. Furthermore, we performed drug susceptibility testing and sequence analyses to determine the characteristics of these genes in the M. abscessus group.

Increased Tuberculosis Burden Due to Demographic Transition in Korea from 2001 to 2010

Background Notified tuberculosis (TB) cases in Korea have not decreased over the last decade (2001-2010). Methods To clarify the reasons, we analyzed an annual report on notified tuberculosis patients and age-specific population drift in Korea. Results Compared to the age-specific notified TB cases between 2001 and 2010, distinctive features in notified TB cases and new cases increased markedly in people aged 45-54 years and in patients over 65 years old, whereas those between 15-34 years in 2010 decreased drastically. In particular, notified TB individuals over 65 years old occupied 29.6% of the cases in 2010, which was 1.5 times higher than that in 2001. The main reason not to decrease in notified TB patients for the last decade (2001-2010) was due to the increasing elderly population as well as the aging of baby boomers, which have a higher risk of TB development. Conclusion Korea needs to pay attention to the older population in order to successfully decrease the burden of TB in the future.