A qualitative study on the adoption of the new duty hour regulations among medical residents and faculty in Korea.

Duty hour regulations (DHRs) were enforced in 2017 in Korea to prevent the detrimental effects of excessively prolonged working hours among medical residents. We investigated the adoption of and implications of the new DHRs among medical residents and faculty members. Semi-structured interviews were conducted with 15 medical residents and 9 faculty members across general surgery, internal medicine, obstetrics-gynecology, and pediatrics departments at Chonnam National University Hospital. Based on the constructivist grounded theory, we developed themes from the data by concurrent coding and analysis with theoretical sampling until data saturation. In addition, respondent validation was used to ensure accuracy, and all authors remained reflexive throughout the study to improve validity. The methods of DHRs adoption among residents and faculty members included the following 4 themes: DHRs improved work schedule, residents have more time to learn on their own, clinical departments have come to distribute work, organization members have strived to improve patient safety. Residents have undertaken initial steps towards creating a balance between personal life and work. Teamwork and shift within the same team are the transitions that minimize discontinuity of patient care considering patient safety. Teaching hospitals, including faculty members, should ensure that residents' work and education are balanced with appropriate clinical experience and competency-based training.

The application of flipped learning to a gross anatomy dissection course.

We implemented flipped learning for a gross anatomy dissection course and compared its effects on students' motivation and academic achievement with those of traditional dissection methods. We invited 142 first-year medical students at Chonnam National University Medical School to participate in this study. All participants engaged in traditional dissection methods in the first part of the study and flipped learning in the latter part. Medical students' motivation to learn anatomy by cadaveric dissection was measured using the ARCS (Attention, Relevance, Confidence, and Satisfaction) model. Thereafter, all students completed a written examination consisting of 96 multiple-choice questions. The students' mean motivational score regarding attention was significantly higher in association with flipped learning than with traditional learning. However, the students' mean motivational scores regarding relevance, confidence, and satisfaction were not significantly different between the methods. Additionally, the mean anatomy practice test score was significantly higher in association with flipped learning than with traditional learning. The students' motivational scores and anatomy practice test scores associated with flipped learning positively correlated with the extent of learning material completion. The students' responses indicated that flipped learning helped enhance the learning process, improve time management, reduce confusion during practice, and promote independent practice. The application of flipped learning to a cadaveric dissection course increased individual learning motivation, which improved learning activities both in and out of class, as well as academic achievement.

Factors associated with academic performance among medical students at a medical school in South Korea: A retrospective cohort study.

Longitudinal research has provided systematic empirical data on the short- and long-term outcomes of admissions policies, curricular innovations, and complex decisions on students' academic progress. This study aimed to investigate the academic performance of medical students and related factors using cohort database collected from a medical school. The study participants included 134 medical students who graduated from Chonnam National University Medical School in 2022. The medical school's cohort database was used to collect data on demographics, admission, academic performance, extracurricular activities, and performance on the National Korean Medical Licensing Examination (KMLE). Participating in club activities had a significant association with medical students' academic advancement delay or leave of absence during the entire course of medical school (P = 0.007). Logistic regression analysis indicated that the nationwide clinical knowledge mock examination during the fourth year of medical school was significantly associated with passing the KMLE (adjusted odds ratio 1.12, 95% confidence interval 1.02-1.22; P = 0.014). Extracurricular school activities (a non-cognitive student attribute) and a wide range of cognitive student attributes captured from the cohort database were associated with medical students' academic performance. In conclusion, this study can reinforce a strong emphasis on the inclusion of cognitive and non-cognitive information in medical school curricula and assessments in order to improve medical education programs and future postgraduate performance.

Latent profile analysis on the effectiveness of tutor performance: Influence on medical students' engagement in blended problem-based learning.

Tutor performance is a critical factor for the success of a problem-based learning (PBL) curriculum. This study investigated medical students' perceptions of the effectiveness of tutor performance and the relationships with learning engagement (behavioral, emotional, and cognitive engagement) in the blended PBL approach. This study employed a cross-sectional survey and data were collected from 238 first-year and second-year medical students. Latent profile analysis (LPA) was used to investigate how individual students' perceptions of tutor performance can be clustered. Follow-up multiple one-way analyses of covariance (ANCOVA) were performed to examine the relationships with students' learning engagement in PBL activities. The effectiveness of tutor performance perceived by students was classified into lowly, moderately, and highly effective tutors. These clustering profiles were significantly related to the different types of learning engagement in the blended PBL process. Hence, this study highlights that the tutor is one of the key aspects of assessing the implementation of blended PBL since student performance is positively associated with the perception of tutor effectiveness.

The perception of medical residents and faculty members on resident duty hour regulation.

PURPOSE: This study investigated the perceptions of medical residents and faculty members before the implementation of the duty hour regulation in December 2017. METHODS: A survey was administered to 263 residents and 358 faculty members in the Chonnam National University Hospital. The subjects were given a self-administered structured questionnaire designed to measure their perspectives on duty hour regulation. They were also asked to answer an open-ended question regarding their expectations or concerns regarding duty hour regulation. The response rates were 50.2% for residents and 24.0% for faculty members. RESULTS: Residents and faculty members regarded the improvement of junior residents' well-being favorably, but had conflicting views regarding senior residents. Residents expressed difficulty in completing unchanged workloads within the limited time, while faculty members were more concerned about worsening patient safety due to the discontinuity of care and insufficient resident education. CONCLUSION: Medical residents and faculty members had differing concerns regarding duty hour regulation. Further studies and the development of future policies should be considered to improve resident education and patient safety within the limited duty hour regulation.

Medical education trends for future physicians in the era of advanced technology and artificial intelligence: an integrative review.

BACKGROUND: Medical education must adapt to different health care contexts, including digitalized health care systems and a digital generation of students in a hyper-connected world. The aims of this study are to identify and synthesize the values that medical educators need to implement in the curricula and to introduce representative educational programs. METHODS: An integrative review was conducted to combine data from various research designs. We searched for articles on PubMed, Scopus, Web of Science, and EBSCO ERIC between 2011 and 2017. Key search terms were "undergraduate medical education," "future," "twenty-first century," "millennium," "curriculum," "teaching," "learning," and "assessment." We screened and extracted them according to inclusion and exclusion criteria from titles and abstracts. All authors read the full texts and discussed them to reach a consensus about the themes and subthemes. Data appraisal was performed using a modified Hawker 's evaluation form. RESULTS: Among the 7616 abstracts initially identified, 28 full-text articles were selected to reflect medical education trends and suggest suitable educational programs. The integrative themes and subthemes of future medical education are as follows: 1) a humanistic approach to patient safety that involves encouraging humanistic doctors and facilitating collaboration; 2) early experience and longitudinal integration by early exposure to patient-oriented integration and longitudinal integrated clerkships; 3) going beyond hospitals toward society by responding to changing community needs and showing respect for diversity; and 4) student-driven learning with advanced technology through active learning with individualization, social interaction, and resource accessibility. CONCLUSIONS: This review integrated the trends in undergraduate medical education in readiness for the anticipated changes in medical environments. The detailed programs introduced in this study could be useful for medical educators in the development of curricula. Further research is required to integrate the educational trends into graduate and continuing medical education, and to investigate the status or effects of innovative educational programs in each medical school or environment.

The relationship between medical students' epistemological beliefs and achievement on a clinical performance examination.

PURPOSE: This study was to explore the relationship between clinical performance examination (CPX) achievement and epistemological beliefs to investigate the potentials of epistemological beliefs in ill-structured medical problem solving tasks. METHODS: We administered the epistemological beliefs questionnaire (EBQ) to fourth-year medical students and correlated the results with their CPX scores. The EBQ comprised 61 items reflecting five belief systems: certainty of knowledge, source of knowledge, rigidity of learning, ability to learn, and speed of knowledge acquisition. The CPX included scores for history taking, physical examination, and patient-physician interaction. RESULTS: The higher epistemological beliefs group obtained significantly higher scores on the CPX with regard to history taking and patient-physician interaction. The epistemological beliefs scores on certainty of knowledge and source of knowledge were significantly positively correlated with patient-physician interaction. The epistemological beliefs scores for ability to learn were significantly positively correlated with those for history taking, physical examination, and patient-physician interaction. CONCLUSION: Students with more sophisticated and advanced epistemological beliefs stances used more comprehensive and varied approaches in the patient-physician interaction. Therefore, educational efforts that encourage discussions pertaining to epistemological views should be considered to improve clinical reasoning and problem-solving competence in the clinic setting.

Does medical students' clinical performance affect their actual performance during medical internship?

INTRODUCTION: This study examines the relationship between the clinical performance of medical students and their performance as doctors during their internships. METHODS: This retrospective study involved 63 applicants to a residency programme conducted at the Chonnam National University Hospital, South Korea, in November 2012. We compared the performance of the applicants during their internship with the clinical performance of the applicants during their fourth year of medical school. The performance of the applicants as interns was periodically evaluated by the faculty of each department, while the clinical performance of the applicants as fourth year medical students was assessed using the Clinical Performance Examination (CPX) and the Objective Structured Clinical Examination (OSCE). RESULTS: The performance of the applicants as interns was positively correlated with their clinical performance as fourth year medical students, as measured by CPX and OSCE. The performance of the applicants as interns was moderately correlated with the patient-physician interactions items addressing communication and interpersonal skills in the CPX. CONCLUSION: The clinical performance of medical students during their fourth year in medical school was related to their performance as medical interns. Medical students should be trained to develop good clinical skills, through actual encounters with patients or simulated encounters using manikins, so that they are able to become competent doctors.

Peer-Assisted Learning in a Gross Anatomy Dissection Course.

Peer-assisted learning encourages students to participate more actively in the dissection process and promotes thoughtful dissection. We implemented peer-assisted dissection in 2012 and compared its effects on students' self-assessments of learning and their academic achievement with those of faculty-led dissection. All subjects performed dissections after a lecture about upper-limb gross anatomy. Experimental group (n = 134) dissected a cadaver while guided by peer tutors who had prepared for the dissection in advance, and control group (n = 71) dissected a cadaver after the introduction by a faculty via prosection. Self-assessment scores regarding the learning objectives related to upper limbs were significantly higher in experimental group than in control group. Additionally, experimental group received significantly higher academic scores than did control group. The students in peer-assisted learning perceived themselves as having a better understanding of course content and achieved better academic results compared with those who participated in faculty-led dissection. Peer-assisted dissection contributed to self-perception and to the ability to retain and explain anatomical knowledge.

[The relationship between problem-based learning and clinical performance evaluations].

PURPOSE: To explore the relationship between problem-based learning (PBL) evaluations and clinical performance. METHODS: The study included 117 third-year medical students at Chonnam National University Medical School. The students' first-, second-, and third-year PBL evaluations were compared with their clinical performance examination (CPX) scores in third year. The PBL evaluations were composed of three subscales: tutors' evaluation (students' professional behavior, contribution to group process, and contribution to group content), a report, and a written examination. The CPX assessed four performance categories: history taking, physical examination, information sharing, and patient-physician interaction. RESULTS: No significant correlation was found between the first-year PBL evaluations and CPX scores; however, the second-year PBL evaluations were significantly correlated with history taking (r=0.186, p=0.044) and patient-physician interaction (r=0.213, p=0.021) of CPX. The third-year PBL evaluations were significantly correlated with physical examination (r=0.248, p=0.007), and patient-physician interaction (r=0.283, p=0.002) of CPX. Several significant correlations between the PBL evaluations subscales and CPX scores were revealed. The PBL tutors' evaluation (r=0.343, p=0.000) and report scores (r=0.210, p=0.023) were significantly correlated with patient-physician interaction of CPX. The contribution to group process of tutors' evaluation was significantly correlated with patient-physician interaction (r=0.186, p=0.045), and the contribution to group content of tutors' evaluation was significantly correlated with physical examination (r=0.187, p=0.044). CONCLUSION: We found a significant association between PBL evaluations and CPX scores.

Mentoring experience and its effects on medical interns.

INTRODUCTION: Effective mentoring helps interns in the early stages of their medical career to reach personal and professional goals. This study investigated the mentoring experience of Korean interns during medical internship and evaluated mentoring effects to facilitate the development of future mentoring programmes. METHODS: Participants were interns being trained at Chonnam National University Hospital, South Korea, in 2011. Interns were asked to complete a questionnaire about their mentoring experiences and job satisfaction. RESULTS: A total of 61 medical interns participated in the study, giving a response rate of 70.1%. Among these interns, 26 (42.6%) had mentoring experiences, with an average of 2.3 ± 1.9 mentors per mentee. Mentees usually discussed career planning and concerns regarding their personal and social lives with their mentors. Perceived quality of the mentor was significantly more important for male mentees than for female mentees. Female interns without a mentor made significantly less effort to seek a mentor than their male counterparts. Having and not having a mentor resulted in significant differences in the interns' job satisfaction. CONCLUSION: Fewer than half of the medical interns had mentoring experiences. Results suggest that the mentoring relationship may be less satisfying and more challenging for female interns. Effective mentoring may not only help interns plan their medical career, but also increase job satisfaction. Mentoring programmes during medical internship should be expanded and supported, as it is the initial step in a medical career.

Medical residents' job satisfaction and their related factors.

PURPOSE: This study was conducted to investigate medical residents' job satisfaction and their related factors to improve the quality of residency program. METHODS: The study subjects were 159 medical residents being trained at Chonnam National University Hospital, South Korea, in 2011. The participants were asked to complete a short form Minnesota satisfaction questionnaire (MSQ). RESULTS: The mean score for 20 items on the short form MSQ varied between 2.91 and 3.64 on a 5-point Likert scale. The assessment of related factors with job satisfaction revealed that medical residents had higher levels for job satisfaction, particularly those who were women (beta=0.200, p=0.022), and those who had mentorship experience (beta=0.219, p=0.008). CONCLUSION: This study results indicate that we should expand and support the mentorship program during medical residency to promote job satisfaction.

Advance organizers in a gross anatomy dissection course and their effects on academic achievement.

We presented two kinds of advance organizers (AOs), video clips and prosection, for a gross anatomy dissection course and compared their effects on academic achievement and student perception of the learning experience. In total, 141 students at Chonnam National University Medical School were randomly assigned to two groups: Group 1 (n = 70) was provided with video clips AO, whereas Group 2 (n = 71) was provided with prosection AO, the use of cadaveric specimens dissected by the course instructor. Student self-assessment scores regarding the learning objectives of upper limb anatomy improved significantly in both groups. Academic achievement scores in Group 2 were significantly higher than those in Group 1, although the self-assessment scores were not significantly different between the groups. Additionally, students in Group 2 responded significantly more positively to the statements about perception of the learning experience such as helping them understand the course content and concepts, decreasing anxiety about the dissection course, and participating actively in the dissection. It would seem that the application of prosection as an AO improved academic achievement and increased student engagement and satisfaction. This study will contribute to designing effective AOs and developing a teaching and learning strategy for a gross anatomy dissection course.

Seasonal factors influencing exercise-induced asthma.

PURPOSE: Exercise-induced bronchoconstriction (EIB) in patients with asthma occurs more frequently in winter than in summer. The concentration of house dust mite (HDM) allergens in beds also shows seasonal variation. This study examined the relationship between seasonal differences in the prevalence of EIB and sensitization to HDMs in patients with asthma. METHODS: The medical records of 74 young adult male patients with asthma-like symptoms who underwent bronchial challenge with methacholine, 4.5% saline and exercise, and allergen skin prick tests, were reviewed. The subjects were divided into summer (n=27), spring/fall (n=26) and winter (n=21) groups according to the season during which they underwent testing. RESULTS: The positive responses to exercise differed according to season (48.1% in summer, 73.1% in spring/fall, and 90.5% in winter; P<0.01). In addition, the prevalence of positive responses to HDM (70.4%, 88.5%, and 95.2%, respectively; P<0.05) and pollen skin tests (37.0%, 19.2%, and 0%, respectively; P<0.01) also showed significant seasonal differences. Severe responses to 4.5% saline showed a similar trend, although it was not statistically significant (44.4%, 50.0%, and 71.4%, respectively; P=0.07). Skin test reactivity to HDMs was significantly related to maximal fall in forced expiratory volume in one second (FEV1) following exercise (r=0.302, P<0.01) and the index of airway hyperresponsiveness (AHR) to 4.5% saline (r=-0.232, P<0.05), but not methacholine (r=-0.125, P>0.05). CONCLUSIONS: Positive skin test reactions to HDMs and EIB occurred in winter, spring/fall, and summer in decreasing order of frequency. Seasonal variation in the prevalence of EIB may be related to seasonal variation in sensitization to HDMs, accompanied by differences in indirect, but not direct, AHR.

Therapeutic effects of mycobacterial secretory proteins against established asthma in BALB/c mice.

PURPOSE: Live/killed mycobacteria and culture supernatants can suppress asthmatic reactions. This study investigated whether mycobacterial secretory proteins have therapeutic effects on asthma. METHODS: Mycobacterium bovis bacille Calmette-Guérin (BCG; 2×10(5) CFUs) and mycobacterial secretory proteins (Ag85 complex, 38-kDa protein or MPB70; 4 or 20 µg) were administered intraperitoneally to female BALB/c mice with established airway hyperresponsiveness. One week after treatment, the mice underwent a methacholine challenge test, and then inflammatory cell numbers in bronchoalveolar lavage fluid (BAL) and around bronchi (<500 µm), and cytokine levels in splenocyte supernatants, were assessed. RESULTS: BCG and all of the tested secretory proteins significantly improved airway sensitivity compared to baseline values (P<0.05). The secretory protein Ag85 complex significantly suppressed airway reactivity also (P<0.05), while 38-kDa protein significantly suppressed reactivity and maximal narrowing (P<0.05). The number of eosinophils in BAL and around bronchi, and the goblet cell proportion, were also significantly reduced in mice in both the BCG and secretory protein groups compared to the asthma control group. IFN-γ/IL-5 ratios were significantly higher in mice treated with BCG, 4 µg MPB70 or 4 µg 38-kDa protein than in asthma control mice (P<0.05), and were negatively associated with airway hyperresponsiveness, peribronchial eosinophil numbers and goblet cell proportion (all P<0.05). IL-17A was positively correlated with IL-5 (r=0.379, P<0.001), maximal airway narrowing, peribronchial eosinophil numbers and goblet cell proportion (all P<0.05). CONCLUSIONS: Secretory proteins from BCG and M. tuberculosis and live BCG were effective against established asthma, their effects being accompanied by increased IFN-γ/IL-5 ratios. Thus, allergic asthma could be effectively treated with mycobacterial secretory proteins.

Medical students' failure experiences and their related factors.

PURPOSE: A considerable number of medical students drop out due to low academic achievement, and these students have a high probability of repeated failure experiences. This study investigated the personal and academic problems of these students to help develop student support systems. METHODS: First-year (n=146) and second-year (n=119) medical students were asked to complete questionnaires. The questionnaires consisted of personality traits and the students' management of/satisfaction with school life. RESULTS: Students who had already dropped out accounted for 17.4% of the study subjects. The most common reason for dropping out was low academic achievement, and the most difficult part of taking a leave of absence from school was psychological anxiety. The group who dropped out had significantly lower levels of emotional stability, sociability, responsibility, dominance, masculinity, and superiority and more vulnerable mental states compared with those who did not drop out. They also expressed less motivation with regard to medical science and less satisfaction with school life than did the group that did not drop out. Those who dropped out tended not to prepare for exams, and they managed their time ineffectively. They also tried to resolve their difficulties alone and rarely sought help from teachers. CONCLUSION: More intimate student-teacher relationships should be established, and teachers should be encouraged to meet and interact with their students on a regular basis. Additionally, personality inventories should be used to assist in efforts to understand students, especially to identify hidden social and emotional problems.

Personal Factors Affecting Therapeutic Responses to BCG Vaccination in Asthmatics.

PURPOSE: Bacille Calmette-Guérin (BCG) vaccination has been reported to be an effective treatment for asthma in several animal models. This study investigated whether the response to BCG treatment in asthma depends on subject clinical characteristics. METHODS: Stable asthma patients were vaccinated with BCG. One month later, alterations in pulmonary function after vaccination and their relationships with subject clinical characteristics were determined. RESULTS: Of 149 patients with asthma, 54 (36.2%) showed a good or fair response to BCG. The ΔFEV1 after vaccination was significantly related to age (r=-0.348, P<0.001), peripheral blood eosinophil counts (r=0.315, P<0.001) and baseline FEV1, expressed as % personal best value (r=-0.474, P<0.001), but not to FEV1 % predicted value (r=-0.066, P>0.05). A good/fair response was highly prevalent in atopic females compared with atopic males, especially among those aged ≤50 years (90.9% vs. 40.0%, P=0.024). Age (P<0.001, odds ratios (OR)=0.92, confidence interval (CI)=0.88-0.96) and atopy (P<0.01, OR=4.95, CI=1.70-14.44) were significant predictors for a good/fair response in females. However, blood eosinophil counts (P<0.05, OR=1.18, CI=1.01-1.39) and FEV1 % best (P<0.001, OR=0.86, CI=0.79-0.94), but not age or atopy, were significant predictors in males. Approximately three-quarters of the males were smokers. CONCLUSIONS: The therapeutic effect of BCG in asthma may differ according to patient clinical characteristics. The greatest benefit occurred in young atopic females. Asthma activity indices, such as eosinophilia and FEV1 % best, were more predictive of a good/fair response in males; this may have been related to cigarette smoking.

Airway responsiveness to inhaled aspirin is influenced by airway hyperresponsiveness in asthmatic patients.

BACKGROUND/AIMS: Many patients with aspirin-induced asthma have severe methacholine airway hyperresponsiveness (AHR), suggesting a relationship between aspirin and methacholine in airway response. This study was performed to determine whether methacholine AHR affects the response of asthmatics to inhaled aspirin. METHODS: The clinical records of 207 asthmatic patients who underwent inhalation challenges with both aspirin and methacholine were reviewed retrospectively. An oral aspirin challenge was performed in patients with a negative inhalation response. The bronchial reactivity index (BRindex) was calculated from the percent decrease in lung function divided by the last dose of the stimulus. RESULTS: Forty-one (20.9%) and 14 (7.1%) patients showed a positive response to aspirin following an inhalation and oral challenge, respectively. Only 24.3 and 14.3% of the responders had a history of aspirin intolerance, respectively. The methacholine BRindex was significantly higher in the inhalation responders (1.46 ± 0.02) than in the oral responders (1.36 ± 0.03, p < 0.01) and in non-responders (n = 141, 1.37 ± 0.01, p < 0.001). The aspirin BRindex was significantly correlated with the methacholine BRindex (r = 0.270, p < 0.001). Three of four patients who received the oral challenge, despite a positive inhalation test, showed negative responses to the oral challenge. Two of these patients had severe AHR. CONCLUSIONS: A considerable number of asthmatic patients with no history of aspirin intolerance responded to the inhalation aspirin challenge. The airway response to aspirin was significantly correlated with methacholine-AHR, and a false-positive response to aspirin inhalation test seemed to occur primarily in patients with severe AHR.

Beta-lactam antibiotic sensitization and its relationship to allergic diseases in tertiary hospital nurses.

PURPOSE: Skin allergies through type 1 and 4 hypersensitivity reactions are the most frequent manifestations of drug allergies. We had previously experienced a case of a nurse with cefotiam-induced contact urticaria syndrome. To aid in preventing the progression of drug-induced allergic disease in nurses, we conducted a survey of tertiary hospital nurses who were likely to have been exposed professionally to antibiotics. METHODS: All 539 staff nurses at a tertiary hospital were asked to respond to a questionnaire regarding antibiotic exposure. Of the 457 nurses (84.8%) who responded, 427 (79.2%) received a physical examination of the hands and 318 (59.0%) received skin prick tests with the beta-lactam antibiotics cefotiam, cefoperazone, ceftizoxime, flomoxef, piperacillin and penicillin G. RESULTS: A positive response to at least one of the antibiotics occurred in 8 (2.6%) of the 311 subjects included in the analysis and stages 1 and 2 contact urticaria syndrome were observed in 38 (8.9%) and 3 (0.7%) of 427 nurses, respectively. The frequencies of a positive antibiotic skin test (6.9 versus 1.3%, chi(2)=7.15, P=0.018), stage 1 contact urticaria syndrome (14.4 versus 7.4%, chi(2)=4.33, P=0.038) and drug allergy (15.3 versus 3.6%, chi(2)=18.28, P=0.000) were higher in subjects with a positive skin allergy history than in those without. Allergic rhinitis (P=0.02, OR=3.86, CI=1.23-12.06), night cough (P=0.04, OR=3.12, CI=1.03-9.41) and food allergy (P=0.00, OR=9.90, CI=3.38-29.98) were significant risk factors for drug allergy. CONCLUSIONS: Antibiotic sensitization and drug allergy occurred more frequently in nurses with a positive skin allergy history. Atopy may be an important risk factor for drug allergy.

Preventive effects of mycobacteria and their culture supernatants against asthma development in BALB/c mice.

PURPOSE: Live Mycobacterium bovis Bacille Calmette-Guérin (BCG) has a suppressive effect on asthma, but its use in clinical practice may be limited due to adverse reactions. To develop a product that is effective for suppressing asthma with minimal adverse reactions, we investigated whether the heat-killed body or culture supernatants of mycobacteria could also prevent asthma development. METHODS: Female BALB/c mice were treated with live BCG, the heat-killed body, or culture supernatants of BCG or Mycobacterium tuberculosis intraperitoneally, while sensitizing and provoking with ovalbumin. Then they underwent a methacholine bronchoprovocation test, and the peribronchial inflammatory cell numbers and cytokine levels in splenocyte culture supernatants were assessed. RESULTS: The airway sensitivity to methacholine decreased significantly after treatment with not only live BCG (30.8 versus 10.0 mg/mL, P<0.001) but also with the culture supernatant (BCG, 23.0 mg/mL, P<0.05; M. tuberculosis, 20.5 mg/mL, P<0.05). In contrast, heat-killed mycobacteria did not effectively decrease airway sensitivity. The peribronchial eosinophil counts and the goblet cell proportions in total epithelial cells decreased significantly in most of the groups. The interferon-gamma/interleukin-5 ratios increased significantly in most of the treatment groups except for the heat-killed groups, and were significantly related to airway sensitivity (r=0.312, P<0.01) and peribronchial eosinophil counts (r=-0.416, P<0.001). Interleukin-17A level was inversely related to airway sensitivity (r=-0.212, P<0.05) and was significantly lower in the live BCG group than in the control (137+/-20 versus 308+/-57 pg/mL, P<0.05). CONCLUSIONS: BCG and mycobacteria culture supernatants may effectively prevent the development of asthma associated with altered Th1/Th2 cytokines and interleukin-17A levels.