Outcome of High Dose Ampicillin-Sulbactam and Colistin Combination Therapy for Treating Ventilator-Associated Pneumonia Caused by Carbapenem-Resistant Acinetobacter baumannii: a Pilot Study

Purpose@#This pilot study aimed to evaluate the efficacy of high dose ampicillin-sulbactam and colistin combination therapy for ventilator-associated pneumonia (VAP) caused by carbapenem-resistant Acinetobacter baumannii (CRAB) in the pediatric intensive care unit of Pusan National University Children's Hospital. @*Methods@#We retrospectively reviewed 17 pediatric patients with VAP caused by CRAB from June 2017 to August 2018. Ten (58.8%) patients were treated with high dose ampicillin-sulbactam and colistin combination therapy (combination therapy group), whereas 7 were treated with colistin only or with various combinations with or without colistin (other antibiotics group). Clinical and bacteriological outcomes were compared between the groups. @*Results@#The mean duration of fever after antibiotic use was 1.30±1.70 days in the combination therapy group and 1.71±1.49 days in the other antibiotics group. The mean duration of days for negative conversion of endotracheal aspirate bacterial culture afterantibiotic therapy was 3.40±1.71 days in the combination therapy group and 11.80±8.86 days in the other antibiotics group. The mortality rate within 30 days of antibiotic therapy was 1/10 (10%) in the combination therapy group and 3/7 (42.9%) in the other antibiotics group. @*Conclusions@#High dose ampicillin-sulbactam and colistin combination therapy as early antibiotic treatment in VAP caused by CRAB in children could improve clinical outcomes.

Molecular Strain Typing of Mycobacterium tuberculosis: a Review of Frequently Used Methods

Tuberculosis, caused by the bacterium Mycobacterium tuberculosis, remains one of the most serious global health problems. Molecular typing of M. tuberculosis has been used for various epidemiologic purposes as well as for clinical management. Currently, many techniques are available to type M. tuberculosis. Choosing the most appropriate technique in accordance with the existing laboratory conditions and the specific features of the geographic region is important. Insertion sequence IS6110-based restriction fragment length polymorphism (RFLP) analysis is considered the gold standard for the molecular epidemiologic investigations of tuberculosis. However, other polymerase chain reaction-based methods such as spacer oligonucleotide typing (spoligotyping), which detects 43 spacer sequence-interspersing direct repeats (DRs) in the genomic DR region; mycobacterial interspersed repetitive units–variable number tandem repeats, (MIRU-VNTR), which determines the number and size of tandem repetitive DNA sequences; repetitive-sequence-based PCR (rep-PCR), which provides high-throughput genotypic fingerprinting of multiple Mycobacterium species; and the recently developed genome-based whole genome sequencing methods demonstrate similar discriminatory power and greater convenience. This review focuses on techniques frequently used for the molecular typing of M. tuberculosis and discusses their general aspects and applications.

Nontuberculous Mycobacterial Lung Disease Caused by Mycobacterium lentiflavum in a Patient with Bronchiectasis / 결핵및호흡기질환

We report a rare case of lung disease caused by Mycobacterium lentiflavum in a previously healthy woman. A 54-year-old woman was referred to our hospital due to chronic cough and sputum. A computed tomography scan of the chest revealed bilateral bronchiectasis with bronchiolitis in the right middle lobe and the lingular division of the left upper lobe. Nontuberculous mycobacteria were isolated twice from three expectorated sputum specimens. All isolates were identified as M. lentiflavum by multilocus sequence analysis based on rpoB, hsp65, and 16S rRNA fragments. To the best of our knowledge, this is the first documented case of M. lentiflavum lung disease in an immunocompetent adult in Korea.

Nontuberculous Mycobacterial Lung Disease Caused by Mycobacterium chelonae: A Case Report / 결핵및호흡기질환

Mycobacterium chelonae lung disease is very rare. We report a case of lung disease caused by M. chelonae in a previously healthy woman. A 69-year-old woman was referred to our hospital because of hemoptysis. A computed tomography (CT) scan of the chest revealed bronchiolitis associated with bronchiectasis in the lingular division of the left upper lobe. Nontuberculous mycobacteria were isolated three times from sputum specimens. All isolates were identified as M. chelonae by various molecular methods that characterized rpoB and hsp65 gene sequences. Although some new lesions including bronchiolitis in the superior segment of the left lower lobe developed on the chest CT scan 35 months after diagnosis, she has been followed up without antibiotic therapy because of her mild symptoms. To the best of our knowledge, this is the first case of M. chelonae lung disease in Korea in which the etiologic organisms were confirmed using molecular techniques.

Nontuberculous Mycobacterial Lung Disease Caused by Mycobacterium terrae in a Patient with Bronchiectasis / 결핵및호흡기질환

We report a rare case of lung disease caused by Mycobacterium terrae in a previously healthy woman. A 45-year-old woman was referred to our hospital due to a chronic cough with sputum. A computed tomography scan of the chest revealed bronchiolitis in conjuction with bronchiectasis in both lungs. Nontuberculous mycobacteria were identified and isolated from the bronchoalveolar lavage fluid collected from each lung. All isolates were identified as M. terrae by various molecular methods that characterized the rpoB and hsp65 gene sequences. Antibiotic therapy using clarithromycin, rifampin, and ethambutol improved the patient's condition and successfully resulted in sputum conversion.

Current Understanding of Mycobacterium abscessus Infection

Mycobacterium abscessus belongs to a group of rapidly growing mycobacteria (RGM) that cause a broad spectrum of infections in humans. In addition, the association of M. abscessus with the cause of community- and hospital-acquired infections has been recently reported. In fact, M. abscessus is known to be the most drug-resistant mycobacterium and naturally resistant to first-line anti-tuberculous drugs, resulting in the limited therapeutic options and a high failure rate of treatment response. Three closely related species; M. abscessus (sensu stricto), M. bolletii, and M. massiliense are currently identified however, consensus on the naming of M. abscessus-related species has not been made to date. We herein discuss the advanced understanding of the virulence potentials and pathophysiological features of M. abscessus to establish novel therapeutic strategies for M. abscessus infection.

Comparison of an Automated Repetitive Sequence-based PCR Microbial Typing System with IS6110-Restriction Fragment Length Polymorphism for Epidemiologic Investigation of Clinical Mycobacterium tuberculosis Isolates in Korea / 대한진단검사의학회지

Tuberculosis remains a severe public health problem worldwide. Presently, genotyping is used for conducting epidemiologic and clinical studies on tuberculosis cases. We evaluated the efficacy of the repetitive sequence-based PCR (rep-PCR)-based DiversiLab(TM) system (bioMerieux, France) over the IS6110-restriction fragment length polymorphism analysis for detecting Mycobacterium tuberculosis. In all, 89 clinical M. tuberculosis isolates collected nationwide from Korea were used. The DiversiLab system allocated the 89 isolates to 8 groups with 1 unique isolate when a similarity level of 95% was applied. Seventy-six isolates of the Beijing family and 13 isolates of non-Beijing family strains were irregularly distributed regardless of rep-PCR groups. The DiversiLab system generated a rapid, sensitive, and standardized result. It can be used to conduct molecular epidemiologic studies to identify clinical M. tuberculosis isolates in Korea.

Characteristics of Molecular Strain Typing of Mycobacterium tuberculosis Isolated from Korea / 대한임상미생물학회지

Molecular strain typing of Mycobacterium tuberculosis is important for the detection of outbreaks of tuberculosis and laboratory cross contamination, as well as the differentiation between re-infection and reactivation of tuberculosis. In the present review, the authors investigated the currently available typing methods for M. tuberculosis and the current status of strain distribution in Korea. IS6110-restriction fragment length polymorphism (RFLP), which is considered a standard method, is based on numbers and positions of the insertion sequence, IS6110. The method has an excellent discriminatory power with a considerable amount of worldwide data, although it is time-consuming and labor-intensive. Spoligotyping is based on the presence or absence of spacer sequences between direct repeat (DR) regions. PCR amplification allows for the possibility of application in the early suspicious stage. The data can be easily digitized; however, it shows identical profiles in Beijing family strains. Mycobacterial interspersed repetitive unit-variable number of tandem repeat (MIRU-VNTR) is another PCR-based genotyping method with a good discrimination power whose data can also be easily digitized. In Korea, the prevalence of Beijing family strains have been as high as 80 to 87%.

Application of Single-nucleotide Polymorphism and Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats Analyses to Clinical Mycobacterium tuberculosis Isolates from Korea / 대한진단검사의학회지

BACKGROUND: Single-nucleotide polymorphism (SNP) analysis is a powerful strategy for large-scale molecular population studies examining phylogenetic relationships among bacterial strains. Mycobacterial interspersed repetitive units-variable number of tandem repeats (MIRU-VNTR) can be easily digitized to share data among laboratories. This study applied SNP and MIRU-VNTR analyses for molecular strain typing of Mycobacterium tuberculosis isolates collected throughout Korea. METHODS: We studied 102 clinical M. tuberculosis isolates, including 6 paired strains, collected from 11 university hospitals in Korea in 2008 and 2009. SNPs were detected using hairpin primer assays, and then, MIRU-VNTR analysis was performed. RESULTS: Thirty-five SNPs contained polymorphisms that helped differentiate the 96 tested isolates. The isolates were classified into 15 clusters. The Beijing family strains were distributed within closely related clusters in the SNP dendrogram. For MIRU-VNTR analysis, the 96 isolates were divided into 12 groups. The discriminatory index in 8 of these groups (MIRU-10, -23, -26, and -31; ETR-A, -B, -C, and -F) was high (Hunter-Gaston diversity index > 0.6). Unlike the SNP method, MIRU-VNTR analysis did not identify any notable localizations of Beijing or non-Beijing family isolates in specific clusters. CONCLUSIONS: SNP and MIRU-VNTR analyses are surrogate molecular strain-typing methods for M. tuberculosis in Korea where Beijing family isolates are predominant.

IS6110-Restriction Fragment Length Polymorphism and Spoligotyping Analysis of Mycobacterium tuberculosis Clinical Isolates for Investigating Epidemiologic Distribution in Korea

The Beijing family of Mycobacterium tuberculosis has been emerging in the world. However, there are few nationwide data of genotypic distribution in Korea. This study aimed to identify the genotypic diversity of clinical isolates of M. tuberculosis and to demonstrate the population of Beijing family in Korea. We collected 96 clinical M. tuberculosis isolates from 11 university hospitals nationwide in Korea from 2008 to 2009. We observed 24 clusters in IS6110-RFLP analysis and 19 patterns in spoligotyping. Seventy-five isolates were confirmed to be Beijing family. Two isolates of the K strain and 12 isolates of the K family strain were also found. We found that drug resistance phenotypes were more strongly associated with Beijing family than non-Beijing family (P=0.003). This study gives an overview of the distribution of genotypes of M. tuberculosis in Korea. These findings indicate that we have to pay more attention to control of M. tuberculosis strains associated with the Beijing family.

ERRATUM / 대한진단검사의학회지

No abstract available.

Antimicrobial Susceptibility Patterns of Legionella isolates in the Environment and in Patients / 대한진단검사의학회지

BACKGROUND: Antimicrobial susceptibility of Legionella spp. has rarely been studied in Korea. Therefore, we aimed to determine the susceptibility of Legionella spp. to various antibiotics. METHODS: We assessed the antimicrobial susceptibility of 66 environmental and clinical Legionella isolates collected between January 2001 and December 2008 from Korea and Japan. The minimum inhibitory concentrations (MICs) of 6 antibiotics, namely, azithromycin, ciprofloxacin, clarithromycin, clindamycin, gatifloxacin, and gemifloxacin were determined by the broth microdilution method using buffered starch yeast extract broth. RESULTS: The MIC ranges of the 6 antibiotics used against the Legionella isolates were as follows: 0.004-0.062 microgram/mL (azithromycin), 0.002-0.5 microgram/mL (ciprofloxacin), 0.004-0.5 microgram/mL (clarithromycin), 0.12-4 microgram/mL (clindamycin), 0.002-0.12 microgram/mL (gatifloxacin), and 0.008-1 microgram/mL (gemifloxacin). CONCLUSIONS: Legionella spp. isolates from Korea and Japan were most susceptible to gatifloxacin. Azithromycin, clarithromycin, ciprofloxacin, and gemifloxacin were also effective for treating legionellosis.

Identification and Diagnostic Utility of Serologic Reactive Antigens from Mycobacterium tuberculosis Sonic Extracts

It is important to identify and to test serologically active antigens, so as to devise a cocktail of the best antigens or peptides. We searched for antigens that have serodiagnostic utility using two-dimensional fractionation of sonic extracts from Mycobacterium tuberculosis and probing with pools of sera from healthy subjects and patients with tuberculosis (TB). Reactive protein spots with patient sera were identified by tandem mass spectrometry. Three proteins, Rv0652, Rv2626c, and Rv3418c, which have not previously been described as serologic targets, were identified. Rv0652 protein among them was expressed in Escherichia coli and serum IgG antibodies against this antigen were measured in 150 patients with pulmonary TB and in 115 healthy subjects. The sensitivity and specificity were 39% and 92%, respectively. These results suggest that a newly identified protein, Rv0652 may be a valuable candidate to be included in a cocktail test kit for TB diagnosis.

Strain Typing of Mycobacterium tuberculosis Isolates from Korea by Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats / 대한진단검사의학회지

BACKGROUND: Mycobacterium tuberculosis is one of the most clinically significant infectious agents. Especially during mass outbreaks, accurate identification and monitoring are required. The proportion of Beijing family members is very high among infecting strains, and spoligotyping is not suitable for strain typing. Therefore, we studied the homogeneity of isolates using the mycobacterial interspersed repetitive units-variable number of tandem repeats (MIRU-VNTR) method and identified its utility for carrying out molecular epidemiologic analysis. METHODS: Eighty-one clinical M. tuberculosis isolates that had previously been analyzed by spoligotyping were used in this study. We used the 12 standard MIRU loci and further four exact tandem repeat (ETR) loci (ETR-A, -B, -C, and -F). Four strains each of randomly selected Beijing and Beijing-like families were subjected to IS6110- restriction fragment length polymorphism analysis. RESULTS: All 81 samples showed amplification products of all VNTR loci, and all of them showed differences in at least one locus. The calculation of the Hunter-Gaston diversity index (HGDI) for MIRU-VNTR gave the value of 0.965. Discriminatory index in the six loci (MIRU-10, -16, -26, -31, -39, and ETR-F) were found to be highly discriminated (HGDI >0.6). Beijing and Beijing-like family isolates were discriminated into different MIRU-VNTR types. CONCLUSIONS: MIRU-VNTR analysis by using well-selected loci can be useful in discriminating the clinical M. tuberculosis isolates in areas where the Beijing family is predominant.