Performance Evaluation of the BACTEC MGIT 960 System for Rifampin Drug-Susceptibility Testing of Mycobacterium tuberculosis Using the Current WHO Critical Concentration.

The World Health Organization recently lowered the rifampin (RIF) critical concentration (CC) for drug-susceptibility testing (DST) of Mycobacterium tuberculosis complex (MTBC) using the mycobacterial growth indicator tube (MGIT) 960 system. Here, we evaluated the diagnostic performance of the MGIT system with the revised CC for determining MTBC RIF resistance with 303 clinical MTBC isolates, including 122 isolates with rpoB mutations, of which 32 had single borderline-resistance mutations, and 181 wild-type rpoB isolates. The phenotypic RIF resistance was determined via the absolute concentration method (AC) and via MGIT using both previous (1 mg/L) and revised (0.5 mg/L) CCs for the latter method. The diagnostic accuracy of each phenotypic DST (pDST) was assessed based on rpoB genotyping as the reference standard. The overall sensitivity of the AC was 95.1% (95% confidence interval [CI], 89.6 to 98.2%), while the MGIT results with previous and revised CCs were 82.0% (95% CI 74.0 to 88.3%) and 83.6% (95% CI 75.8 to 89.7%), respectively. The 32 MTBC isolates with single borderline-resistance mutations showed a wide range of MICs, and sensitivity was not significantly increased by reducing the MGIT CC. All 181 wild-type rpoB isolates were RIF-susceptible in the AC and with MGIT using the previous CC, whereas 1 isolate was misclassified as RIF-resistant with the revised CC. Our results demonstrate that the overall diagnostic performances of the MGIT DST with the revised RIF CC and previous CC were comparable. A further large-scale study is required to demonstrate the optimal RIF CC for MGIT.

Mutations in DNA Gyrase and Topoisomerase IV in Ciprofloxacin-Nonsusceptible Extended-Spectrum -Lactamase-Producing Escherichia coli and Klebsiella pneumoniae.

BACKGROUND: We investigated mutations in the quinolone resistance-determining region (QRDR) of ciprofloxacinnonsusceptible extended-spectrum -lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae by a statistical analysis. METHODS: We collected 97 clinical isolates of ciprofloxacin-nonsusceptible ESBL-producing E. coli (55 strains) and K. pneumoniae (42 strains) from a tertiary-care university hospital in Seoul, Republic of Korea, between 2006 and 2008. The QRDR of the gyrA, gyrB, parC, and parE genes were amplified by PCR and sequenced. RESULTS: Most E. coli isolates (53/55; 96.4%) with a minimum inhibitory concentration of ≥ 64 mg/L against ciprofloxacin had double mutations in gyrA (Ser-83Leu and Asp-87Asn) and at least one mutation in parC (Ser-80 Ile or Glu-84Val), with or without one in parE. Fifty E. coli (90.9%) isolates had a mutation in parE, of which Ile-529Leu (70.9%) was the most frequent. However, we could not find statistically significant variables in increasing ciprofloxacin resistance in E. coli isolates. Thirty-six K. pneumoniae isolates (36/42; 85.7%) had at least one mutation in gyrA, gyrB, or parC, and the mutation in gyrA might have been associated with plasmid-mediated quinolone-resistance (PMQR). Ser-80Ile in parC and aac(6')-Ib-cr in the K. pneumoniae isolates were significantly associated with an increased MIC of ciprofloxacin by ordinal logistic regression analysis. CONCLUSIONS: The Ser-80Ile in parC and aac(6')-Ib-cr in K. pneumoniae are supposed to play an important role in increased ciprofloxacin resistance, but statistically significant variables could not be found in E. coli isolates in the present study.

Prevalence of ST131 and ST1193 Among Bloodstream Isolates of Escherichia coli not Susceptible to Ciprofloxacin in a Tertiary Care University Hospital in Korea, 2013 - 2014.

We investigated the ST distribution of bloodstream isolates of E. coli that were not susceptible to ciprofloxacin (CIP-NS isolates), collected from 2013 to 2014 in a tertiary care hospital. Fifty-nine CIP-NS isolates were collected. ST131 was the most frequent ST (37.3%) isolate, followed by ST1193 (23.7%). ST131 and ST1193 showed significant differences in ESBL production and lactose fermentation. Further study should be continued on the monitoring of resistant strains.

A bloodstream infection by Ruminococcus gnavus in a patient with a gall bladder perforation.

Ruminococcus gnavus is frequently found among human gut microbiome. However, human bloodstream infections by R. gnavus have been reported only three times. Clinical details were lacking for one case; the other two cases with concurrent bacteremia in patients with diverticulitis. We report a case of R. gnavus bloodstream infection in a patient with a gall bladder perforation suggesting its association with damage to the gastrointestinal tract. R. gnavus was misidentified using biochemical test but 16S rRNA sequencing and Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry were useful for correct identification. With the advancement of identification method in clinical laboratory, more frequent identification of R. gnavus from clinical specimens is expected.

Prevalence of Clostridium perfringens toxin in patients suspected of having antibiotic-associated diarrhea.

BACKGROUND: Although Clostridium perfringens has been reported as a cause of antibiotic-associated diarrhea (AAD), it is uncommon to detect this pathogen in clinical microbiology laboratories in Korea. The aim of this study was to investigate the prevalence of C. perfringens toxin in patients suspected of having AAD. METHODS: A total of 135 stool specimens submitted to a clinical microbiology laboratory for C. difficile toxin assay were tested. We tried to detect both C. difficile and C. perfringens toxins using the Seeplex Diarrhea ACE Detection kit (Seegene, Seoul, Korea). We evaluated the prevalence of 10 bacteria and 5 viruses. RESULTS: A total of 40 Clostridium spp. were detected in 34 specimens (29.6%). The C. perfringens toxin was detected in 14 of 135 specimens (10.4%), while C. difficile toxin was detected in 26 specimens (19.3%). Other bacteria and viruses, including 8 Aeromonas spp., were detected in 15 specimens. All tests were negative in 92 of the 135 specimens (68.1%). CONCLUSION: Clostridium perfringens toxin is relatively common, and we should consider the possibility of its presence in patients suspected of having AAD, especially if C. difficile tests are negative.

Validation of a liquid chromatography-triple quadrupole mass spectrometric method for the determination of 5-nitro-5'-hydroxy-indirubin-3'-oxime (AGM-130) in human plasma and its application to microdose clinical trial.

A liquid chromatography-triple quadrupole mass spectrometric (LC-MS/MS) method was developed and validated for the determination of 5-nitro-5'-hydroxy-indirubin-3'-oxime (AGM-130) in human plasma to support a microdose clinical trial. The method consisted of a liquid-liquid extraction for sample preparation and LC-MS/MS analysis in the positive ion mode using TurboIonSpray(TM) for analysis. d3 -AGM-130 was used as the internal standard. A linear regression (weighted 1/concentration) was used to fit calibration curves over the concentration range of 10-2000 pg/mL for AGM-130. There were no endogenous interference components in the blank human plasma tested. The accuracy at the lower limit of quantitation was 96.6% with a precision (coefficient of variation, CV) of 4.4%. For quality control samples at 30, 160 and 1600 pg/mL, the between run CV was ≤5.0 %. Between-run accuracy ranged from 98.1 to 101.0%. AGM-130 was stable in 50% acetonitrile for 168 h at 4°C and 6 h at room temperature. AGM-130 was also stable in human plasma at room temperature for 6 h and through three freeze-thaw cycles. The variability of selected samples for the incurred sample reanalysis was ≤12.7% when compared with the original sample concentrations. This validated LC-MS/MS method for determination of AGM-130 was used to support a phase 0 microdose clinical trial.

Invasive Fungal Sinusitis by Lasiodiplodia theobromae in an Patient with Aplastic Anemia: An Extremely Rare Case Report and Literature Review.

Human Lasiodiplodia theobromae infection has not been reported frequently. We report the first case of invasive L. theobromae nasal and neck infection. A 66-year-old male visited our hospital with anemia and general weakness. He showed pancytopenia, and his bone marrow examination revealed markedly decreased hematopoietic cells. The patient was presumed to have iatrogenic aplastic anemia due to mushroom toxicity. He began treatment for multiple organ infections with broad-spectrum antibiotics and antifungal agents. During hospitalization, he complained of nasal obstruction and left neck lymph node enlargement. A mass-like lesion was observed, and a nasal mass biopsy was performed. The mass was identified as a fungal ball. He underwent surgical excision for the nasal mass and the neck lymph node. The pathologic examination indicated an invasive fungal infection, and the lymph node revealed chronic granulomatous inflammation with fungal infection. 18s rRNA sequencing revealed that the sequence shared 99 % identity with L. theobromae. The nasal mass fungus was identified by internal transcribed spacer region sequencing from pathologic paraffin sections. The obtained sequence corresponded to Lasiodiplodia or Macrophoma. The sequence corresponded to the neck discharge sequence results. Hence, the patient was diagnosed with invasive fungal sinusitis with neck lymph node involvement caused by L. theobromae. To our knowledge, this is the first report of L. theobromae infection in Korea and the first report of invasive L. theobromae fungal sinusitis in the literature. We should include more precise evaluations of additional novel fungal species as possible candidates.

A case of bacteremia caused by Dialister pneumosintes and Slackia exigua in a patient with periapical abscess.

Dialister pneumosintes and Slackia exigua are both obligatory anaerobe and known to be associated with periodontal diseases and other oral infection. We report a case of blood stream infection caused by D. pneumosintes and S. exigua. This occurred in a 78-year-old female patient that presented with general weakness and fever. We revealed that she had a periapical abscess. The blood culture was positive for D. pneumosintes and S. exigua; however, identifying them was challenging. Ultimately, 16S rRNA sequencing was used to identify the organisms. The patient recovered after being treated with ceftriaxone and clindamycin. To the best of our knowledge, this is the first report of bacteremia caused by mixed infection of D. pneumosintes and S. exigua.

MALDI-TOF MS is more accurate than VITEK II ANC card and API Rapid ID 32 A system for the identification of Clostridium species.

All 50 Clostridium difficile strains were definitely identified by Vitek2 system, Rapid ID 32A system, and MALDI-TOF. For 18 non-difficile Clostridium strains, the identification results were correct in 2, 0, and 17 strains by Vitek2, Rapid ID 32A, and MALDI-TOF, respectively [corrected].

Mean platelet volume in patients with increased γ-glutamyl transferase.

Mean platelet volume (MPV) is the commonly measured platelet index for platelet size and surrogate marker of platelet activation. Changes of MPV in hepatic disease have been evaluated in inflammatory conditions, fibrosis and malignancy. We also had reported previous studies to analyze clinical meaning of MPV in patients with hepatocellular carcinoma and chronic hepatitis B. However, data about investigation of MPV in cholestatic conditions are not sufficient so far. Recently, it has been reported that MPV was increased in intrahepatic cholestasis of pregnancy. In this study, we planned to investigate the relationship between MPV and glutamyltransferase which is well-established laboratory marker for cholestasis, in various disease conditions.

Mean platelet volume and mean platelet volume/platelet count ratio in infective endocarditis.

Infective endocarditis (IE), an infection of the endocardial surface, frequently leads to life-threatening complications, such as thromboembolism due to platelet activation. We investigated the mean platelet volume (MPV) in Korean patients with IE and the serial changes thereof, in comparison with other laboratory parameters. We analyzed 248 MPV results from 22 patients diagnosed with IE in our hospital between January 2011 and April 2012. MPV was measured with an Advia 2120 (Siemens Healthcare Diagnostics, Tarrytown, NY) using EDTA-containing tubes. The mean MPV differed significantly between the patient and control groups, 8.74 vs. 7.96 fl, respectively. In addition, the platelet count and MPV/platelet count ratio were significantly decreased in the patient group. The total platelet mass and platelet size in IE might be increased. Further studies should examine more patients to verify the changes in the MPV and MPV/platelet count ratio in IE and assess in greater detail the relationship between MPV and thrombotic complications caused by platelet activation.

Masked monoclonal gammopathy in capillary electrophoresis.

BACKGROUND: Although the method of choice to detect M-protein is electrophoresis on an agarose gel, such gel electrophoresis (GE) is labor-intensive, time-consuming, and not standardized. In contrast to GE, capillary electrophoresis (CE) has some merits because it is automated, fast, and highly reproducible. However, CE results occasionally make the interpretation difficult and require additional confirmatory tests like GE. METHODS: In order to assist a correct reporting of CE results and compatible interpretations between two different electrophoresis methods, we report here two unusual cases of monoclonal gammopathy by a pattern of polyclonal gammopathy upon CE interpretation in patients with end stage renal disease and multiple myeloma. RESULTS: In these cases, serum CE showed the broad bumpy peak in the gamma region. This bumpy peak does not drop completely flat after the reaction with anti-FLC. CONCLUSIONS: Because the plasma cell is a B-cell lineage and plays an important role in adaptive immunity, MG accompanying with PG is not rarely found in plasma cell dyscrasia. If the broad bumpy peak is observed in CE, careful examinations must be done to rule out the hidden M-peak. In our cases, a parallel use of gel-based methods was very helpful as it revealed monoclonal bands.

Free light chain levels in pediatric patients with inflammatory conditions.

BACKGROUND: Because free light chain assays measure polyclonal as well as monoclonal free light chain components, some previous studies focused on the potential utility of the free light chain assay for detecting chronic immune stimulation, which occurs in autoimmune diseases and allergies. However, most of these trials have been limited to adult patients. In this study, we evaluated the paired serum and urinary free light chain levels of pediatric patients with various inflammatory conditions to investigate the clinical significance of free light chain measurement in pediatrics. METHODS: The study included 227 paired serum and urine specimens from 134 pediatric patients at our hospital between January and February of 2012. Serum and urinary FLC levels were measured using a Freelight Kit (The Binding Site, Ltd., Birmingham, UK). RESULTS: The serum lambda and urine kappa and lambda components were significantly increased only in the renal impairment group, not in the mild inflammatory group. FLC ratios were not significantly different among these groups. CONCLUSIONS: In serum, only the L components were significantly increased. This result may indicate the presence of a dimeric L structure, in contrast with monomeric K. FLC levels might also be influenced by renal conditions other than mild inflammation. Therefore, as shown in previous studies of adult patients, renal reference ranges might be needed to interpret FLC results, especially for dimeric L components.

Prevalence of plasmid-mediated quinolone resistance genes among ciprofloxacin-nonsusceptible Escherichia coli and Klebsiella pneumoniae isolated from blood cultures in Korea.

OBJECTIVES: To analyze the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants in ciprofloxacin-nonsusceptible Escherichia coli and Klebsiella pneumoniae isolated from patients at a tertiary care hospital in Korea. METHODS: A total of 102 nonduplicate isolates of ciprofloxacin-intermediate or ciprofloxacin-resistant E coli (n=80) and K pneumoniae (n=22) from blood cultures were obtained. The qnr (qnrA, qnrB, qnrS), aac(6')-Ib-cr, qepA and oqxAB genes were detected using polymerase chain reaction (PCR) and confirmed using direct sequencing. To determine whether the PMQR-positive plasmid was horizontally transferable, conjugation experiments were performed. RESULTS: Of the 102 isolates, 81 (79.4%) had one or more PMQR genes; these consisted of 59 (73.8%) E coli and 22 (100%) K pneumoniae isolates. The qnr genes were present in 15 isolates (14.7%): qnrB4 was detected in 10.8% and qnrS1 was detected in 3.9%. The aac(6')-Ib-cr, qepA and oqxAB genes were detected in 77.5%, 3.9% and 10.8%, respectively. In conjugation experiments, PMQR genes were successfully transferred from seven (8.6%) isolates. The range of minimum inhibitory concentrations of ciprofloxacin for these seven transconjugants increased to 0.5 mg/L to 1 mg/L, which was 16- to 33-fold that of the recipient E coli J53 bacteria. CONCLUSIONS: PMQR genes were highly prevalent among ciprofloxacin-nonsusceptible E coli and K pneumoniae from blood cultures in the authors' hospital. Therefore, it is necessary to monitor for the spread of PMQR genes of clinical isolates and to ensure careful antibiotic use in a hospital setting.

OBJECTIFS: Analyser la prévalence des déterminants de la résistance à la quinolone à médiation plasmidique (RQMP) en cas d'Escherichia coli et de Klebsiella pneumoniae non susceptibles à la ciprofloxacine, isolés chez des patients d'un hôpital de soins tertiaires de la Corée. MÉTHODOLOGIE: Au total, les chercheurs ont obtenu 102 isolats non dupliqués d'E coli (n=80) et de K pneumoniae (n=22) moyennement résistants ou résistants à la ciprofloxacine dans les hémocultures. Ils ont décelé les gènes qnr (qnrA, qnrB, qnrS), aac(6')-Ib-cr, qepA et oqxAB au moyen de la réaction en chaîne de la polymérase (PCR) et les ont confirmés par séquençage direct. Pour déterminer si les plasmides ayant une RQMP pouvaient opérer un transfert horizontal, les chercheurs ont effectué des expériences de conjugaison. RÉSULTATS: Sur les 102 isolats, 81 (79,4 %) avaient au moins un gène de RQMP. De ce nombre, 59 (73,8 %) étaient des isolats d'E coli et 22 (100 %), de K pneumoniae. Les gènes qnr étaient présents dans 15 isolats (14,7 %), soit 10,8 % de gène qnrB4 et 3,9 % de gène qnrS1. Les gènes aac(6')-Ib-cr, qepA et oqxAB ont été décelés dans 77,5 %, 3,9 % et 10,8 % des isolats, respectivement. Dans les expériences de conjugaison, sept isolats (8,6 %) ont entraîné un transfert des gènes de RQMP. La plage de concentrations inhibitrices minimales de la ciprofloxacine de ces sept produits de transconjugaison est passée de 0,5 mg/L à 1 mg/L, soit 16 fois à 33 fois plus que celles des bactéries d'E coli J53 des receveurs. CONCLUSIONS: Les gènes de RQMP étaient hautement prévalents dans les hémocultures d'E coli et de K pneumoniae non susceptibles à la ciprofloxacine à l'hôpital des auteurs. Par conséquent, il faut surveiller la propagation des gènes de RQMP dans les isolats cliniques et vérifier attentivement l'utilisation des antibiotiques en milieu hospitalier.

Trend of nontuberculous mycobacteria species and minimal inhibitory concentration in a referral laboratory in Korea from 2013 to 2019.

BACKGROUND: This study investigated the trends of nontuberculous mycobacterial (NTM) isolates and the minimal inhibitory concentrations (MIC) of antimicrobial agents in Korea. METHODS: Data from 2013 to 2019 were collected from 69 medical institutions through 12 branches of the Korean Institute of Tuberculosis. NTM identification was conducted using the Advansure Mycobacteria Genoblot assay. The MIC of antibiotics against NTM species were measured using the broth microdilution method according to the Clinical and Laboratory Standards Institute guidelines. RESULTS: Over seven years, 86,194 NTM identifications were requested, with an annual increase from 8034 in 2013-17,229 in 2019. The most frequently identified NTM species were M. intracellulare (33,467; 47.3%) and M. avium (19,818; 27.2%), followed by M. abscessus (6858; 9.4%) and M. massiliense (3156; 4.3%). Regarding the antimicrobial agents, imipenem exhibited the greatest difference in MIC between M. intracellulare and M. avium, whereas clarithromycin showed the most significant difference between M. abscessus and M. massiliense. No notable changes were observed in the annual MIC distribution of most antibacterial agents, except for clarithromycin in M. abscessus. CONCLUSIONS: The prevalence of NTM in Korea is gradually increasing, and follow-up studies on NTM isolates identified as the causative agents of infection are needed.

Impact of reduced vancomycin MIC on clinical outcomes of methicillin-resistant Staphylococcus aureus bacteremia.

Vancomycin has been a key antibiotic agent for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. However, little is known about the relationship between vancomycin MIC values at the higher end of the susceptibility range and clinical outcomes. The aim of this study was to determine the impact of MRSA bacteremia on clinical outcomes in patients with a vancomycin MIC near the upper limit of the susceptible range. Patients with MRSA bacteremia were divided into a high-vancomycin-MIC group (2 µg/ml) and a low-vancomycin-MIC group (≤1.0 µg/ml). We examined the relationship between MIC, genotype, primary source of bacteremia, and mortality. Ninety-four patients with MRSA bacteremia, including 31 with a high vancomycin MIC and 63 with a low MIC were analyzed. There was no significant difference between the presence of agr dysfunction and SCCmec type between the two groups. A higher vancomycin MIC was not found to be associated with mortality. In contrast, high-risk bloodstream infection sources (hazard ratio [HR], 4.63; 95% confidence interval [CI] = 1.24 to 17.33) and bacterial eradication after treatment (HR, 0.06; 95% CI = 0.02 to 0.17), irrespective of vancomycin MIC, were predictors of all-cause 30-day mortality. Our study suggests that a high-risk source of bacteremia is likely to be associated with unfavorable clinical outcomes, but a high vancomycin MIC in a susceptible range, as well as genotype characteristics, are not associated with mortality.

Mean platelet volume/platelet count ratio in hepatocellular carcinoma.

Mean platelet volume (MPV) has been actively investigated in liver disease such as steatosis, cirrhosis and hepatitis. Recently, MPV/platelet count (PC) ratio has been proposed as a predictor of long-term mortality after myocardial infarction. As PC is known to be decreased in various liver diseases such as cirrhosis, hepatosplenomegaly and malignancy, we planned to evaluate MPV/PC ratio in patients with hepatocellular carcinoma (HCC) in this study. Mean of MPV levels showed significant difference, which were 8.69 fl (range 6.7-12.2 fl) in patients group and 8.02 fl in control group (range 6.7-11.0 fl). In receiver operating characteristic (ROC) curve analysis, the MPV/PC ratio (fl/(10(9)/l)) presented 74.5% of sensitivity and 96.5% of specificity at the criterion > 0.0491 (area under the curve (AUC) = 0.884), while MPV alone showed 57.4% of sensitivity and 81.4% of specificity at the criterion > 8.4 fl. Further studies should evaluate underlying pathogenic mechanisms of MPV/PC ratio difference and various possibilities of this ratio as an indicator of presence of a tumor in HCC.

Clinical significance of abnormal serum free light chain ratio: diagnostic confusion or underlying monoclonality?

BACKGROUND: The spectrum of laboratory tests used to detect monoclonal components (M-components) include serum and urine protein electrophoresis (PEP), immunofixation electrophoresis, and immunonephelometric methods such as free light chain assay (sFLC). METHODS: In this study, we retrospectively analyzed 78 patients who were to be tested with FLC without previous evidence of MG in order to investigate the clinical meaning of K/L screening. Abnormal K/L in sFLC was found in 25 samples from 21 patients (21/78, 26.92%). RESULTS: Among them, serum electrophoresis was requested for 16 patients where 5 were diagnosed as either normal or polyclonal gammopathy, 5 as plasma cell myeloma, 5 as monoclonal gammopathy of undetermined significance and I as amyloidosis. In total, 11 patients were revealed to have MG related diseases (11/25, 44.0 %). CONCLUSIONS: The clinical function of sFLC as a MG screening tool turned out to be effective based on the result where 16 out of 21 patients who were subject to further study led to diagnoses of MG related diseases in 11 patients. To provide an accurate evaluation for the performance of sFLC as a screening tool for MG, further studies should include additional confirmation of PEP results for patient groups that showed normal K/L ratios.

Laboratory tools for oligo-secretory myeloma diagnosis: capillary electrophoresis versus free light chain assay.

BACKGROUND: To investigate how capillary electrophoresis (CE) works in oligo-secretory myeloma (OSM), we report a case here of OSM using multiple diagnostic methods including gel electrophoresis (GE), CE, and free light chain assay (sFLC). Also, we provide a brief review of laboratory methods to compare their diagnostic utilities in OSM. METHODS: A 72 year-old Korean male suffering from low back pain during the past 6 months was transferred to the department of neurosurgery in order to evaluate abnormal findings in an imaging study, suggesting plasma cell myeloma (PCM) with multiple bone metastasis. CE showed no suspicious M-component; however, it showed increased Kappa components and skewing Kappa/Lambda ratio (K/L). Bone marrow examination revealed plasma cells observed up to 70%, which were compatible with sFLC results. RESULTS: Based on these results, the diagnosis turned out to be OSM with multiple bone metastases. Thereafter, the patient started the first cycle of chemotherapy accompanied by palliative radiation therapy. CONCLUSIONS: In our case, sFLC showed abnormal Kappa and K/L results from both serum and urine specimen. Therefore, it seems to be more sensitive and appropriate than both GE and CE to diagnose OSM.

A Study on the Factors Influencing Smoking in Multicultural Youths in Korea.

Based on the ecological integration model, this study examined the factors affecting smoking in adolescents from multicultural families by dividing them into two levels: microsystem and social network factors. The data were from the Korea Youth Risk Behavior Web-Based Survey (KYRBS) from 2016 to 2020. It included 4577 respondents whose fathers, mothers, or both, were not born in Korea. The factors affecting smoking among multicultural teenagers were determined by a composite-sample multiple logistic regression analysis. Male smoking rates among multicultural adolescents were 2.49 times higher than female rates in the microsystem. When the father was "Korean" rather than a "Foreigner", smoking was 0.55 times lower in family factors in terms of social network. In social factors of social networks, multicultural adolescents' smoking was 12.02 times greater when they were drinking than when they were not, and 3.62 times higher when the answer to the question of whether they had experienced violence was "yes" than "no." Based on the ecological model in this study, social factors such as drinking, and violence were highly related to smoking. Since multicultural adolescents were closely influenced by the surrounding environment, such as family, school, and social relationship, it was necessary to let parents and schoolteachers be involved in the intervention of smoking of multicultural adolescents so that they can help multicultural adolescents adjust better to school and perform better academically while decreasing risky behaviors for their health, such as drinking and, ultimately, smoking.