[Evaluation of the Clinical Validity of the Clostridioides difficile Nucleic Acid Detection Kit "Smart Gene® CD ToxinB"].

Clostridioides difficile is the most common anaerobic bacterium that causes healthcare-associated infections, and prompt diagnosis and infection control are important because it causes C. difficile infection (CDI). In this evaluation, the C. difficile nucleic acid detection reagent, Smart Gene CD Toxin B (Mizuho Medy Co., Ltd., hereinafter referred to as the "evaluation reagent") was evaluated for its clinical performance in comparison with real-time PCR and toxigenic culture (TC). Measurement of evaluation reagents and real-time PCR were performed on 157 residual stool specimens from suspected CDI patients. For TC, stool culture was performed, and colonies in which C. difficile was identified by a mass spectrometer (MALDI Biotyper) were checked for toxin production using a rapid antigen diagnostic kit. The results of the evaluation reagents showed a high concordance rate; 100% sensitivity (81/81) and 100% specificity (76/76) with real-time PCR, 89.8% sensitivity (79/88), and 97.1% specificity (67/69) with TC. The evaluation reagent enables a simple nucleic acid amplification test (NAAT) in a short time and is thought to be useful in CDI treatment, which requires rapid diagnosis and infection control.

Machine learning-based typing of Salmonella enterica O-serogroups by the Fourier-Transform Infrared (FTIR) Spectroscopy-based IR Biotyper system.

BACKGROUND: Salmonella enterica is among the major burdens for public health at global level. Typing of salmonellae below the species level is fundamental for different purposes, but traditional methods are expensive, technically demanding, and time-consuming, and therefore limited to reference centers. Fourier transform infrared (FTIR) spectroscopy is an alternative method for bacterial typing, successfully applied for classification at different infra-species levels. AIM: This study aimed to address the challenge of subtyping Salmonella enterica at O-serogroup level by using FTIR spectroscopy. We applied machine learning to develop a novel approach for S. enterica typing, using the FTIR-based IR Biotyper® system (IRBT; Bruker Daltonics GmbH & Co. KG, Germany). We investigated a multicentric collection of isolates, and we compared the novel approach with classical serotyping-based and molecular methods. METHODS: A total of 958 well characterized Salmonella isolates (25 serogroups, 138 serovars), collected in 11 different centers (in Europe and Japan), from clinical, environmental and food samples were included in this study and analyzed by IRBT. Infrared absorption spectra were acquired from water-ethanol bacterial suspensions, from culture isolates grown on seven different agar media. In the first part of the study, the discriminatory potential of the IRBT system was evaluated by comparison with reference typing method/s. In the second part of the study, the artificial intelligence capabilities of the IRBT software were applied to develop a classifier for Salmonella isolates at serogroup level. Different machine learning algorithms were investigated (artificial neural networks and support vector machine). A subset of 88 pre-characterized isolates (corresponding to 25 serogroups and 53 serovars) were included in the training set. The remaining 870 samples were used as validation set. The classifiers were evaluated in terms of accuracy, error rate and failed classification rate. RESULTS: The classifier that provided the highest accuracy in the cross-validation was selected to be tested with four external testing sets. Considering all the testing sites, accuracy ranged from 97.0% to 99.2% for non-selective media, and from 94.7% to 96.4% for selective media. CONCLUSIONS: The IRBT system proved to be a very promising, user-friendly, and cost-effective tool for Salmonella typing at serogroup level. The application of machine learning algorithms proved to enable a novel approach for typing, which relies on automated analysis and result interpretation, and it is therefore free of potential human biases. The system demonstrated a high robustness and adaptability to routine workflows, without the need of highly trained personnel, and proving to be suitable to be applied with isolates grown on different agar media, both selective and unselective. Further tests with currently circulating clinical, food and environmental isolates would be necessary before implementing it as a potentially stand-alone standard method for routine use.

Efficiency of the novel quenching-probe PCR method to detect 23S rRNA mutations in children with Mycoplasma pneumoniae infection.

An automated rapid molecular diagnostic kit (Smart Gene Myco) was recently developed for individual detection of Mycoplasma pneumoniae (MP) genes. This new testing approach requires no special equipment and skills and can be completed within 50 min. We prospectively evaluated this diagnostic kit, along with other conventional tests, for pneumonia diagnosis in children. Samples from 98 children (50 boys and 48 girls; aged 1-14 years; mean: 4.7 ± 2.1 years; median: 4 years) clinically diagnosed with pneumonia were tested for MP using real-time polymerase chain reaction (RT-PCR) as a reference method. Results from three molecular diagnostic tests, serum anti-MP antibodies, and MP culture were compared to RT-PCR data. Among the 98 children, 38 were positive for MP. All molecular diagnostic results showed complete concordance with the RT-PCR data. The sensitivity of the culture was 64%, whereas the sensitivities of the ImmunoCard Mycoplasma and SERODIA Myco II kits were lower (39% and 29%, respectively). Furthermore, a significant positive correlation was found between MP copy numbers and the culture test sensitivity (r = 0.95, p = 0.048). Macrolide-resistance mutations in the 23S ribosomal RNA gene were detected in 24 of 38 children using Smart Gene Myco based on quenching-probe PCR, which was confirmed by direct sequencing, revealing all mutations as A2063G. This is the first study to evaluate the clinical utility of the Smart Gene Myco kit, demonstrating that it is a fast and reliable method to support timely therapeutic decisions in children with MP pneumonia.

[A Case of Fungalemia that Detected the Mucor circinelloides by Versa TREK].

Man in his 80s. In March 20XX, the level of consciousness decreased at the admission facility, and he was transported as an emergency case. He was diagnosed as aspiration pneumonia, septic shock due to cholecystitis, and DIC, and was hospitalized for medical treatment. During the course of hospitalization, aspiration pneumonia continued to improve and worsen, but in January 20XX＋3, a fever of 38.7°C occurred, and Mucor circinelloides was detected in the blood culture collected at this time. In sputum 7 days before the blood culture was submitted, an image of suspicious zygomycosis was confirmed by Gram stain, so the patient was diagnosed with Mucor disease and started administration of amphotericin B. After that, the condition was temporarily stable, but due to recurrence of aspiration pneumonia and renal damage, he died 19 days after the start of amphotericin B administration. It is difficult to detect Mucor spp. in blood culture, however in this case, it was detected by the blood culture device; Versa TREK (Thermo Fisher Scientific K.K. Tokyo, Japan).

[Evaluation of Screening Performance and Detection Time of Carbapenemase-Producing Enterobacterales Using RAISUS S4 in a Antimicrobial Sensitivity Test].

Rapid detection of carbapenemase-producing Enterobacterales (CPE) is important in infection control, since it transmits plasmids carrying resistance genes. Here, we evaluated the rapid detection of CPE using the fully automated antimicrobial susceptability testing system "RAISUS S4". Sixty-two CPE strains including carbapenem-resistant Enterobacterales and 100 carbapenemase-non-producing Enterobacterales strains were used. RAISUS S4 was performed using both 18 hr and rapid methods. The sensitivity of CPE detection and decision time were evaluated using Meropenem results. The results showed that the sensitivity for CPE detection was 100% for both methods, with specificity of 97% for the 18 hr method and 95% for the rapid method. The mean CPE detection time for the 18 hr method was 7.2 hrs and 8.8 hrs for the rapid method. The mean MIC determination time of the 18 hr method for all 162 strains was 17.2 hrs and 8.8 hrs for the rapid method. In addition, we analyzed the absorbance values of the 18 hr method. Checking the growth curve at a drug concentration of 0.125 µg/ml and determining it to be positive when its absorbance reached 0.8 Abs, CPE could be detected in an average of 5.8 hrs with in sensitivity of 100% and specificity of 92%. The 18 hr method of RAISUS S4 allowed rapid detection of CPE, and the rapid method allowed earlier MIC determination, including sensitive isolates. These results suggest that RAISUS S4 can detect CPE rapidly without missing CPE by routine test even in Japan where the frequency of CPE isolation is low.

Correlation of Strain Classification with IR Biotyper and Molecular Epidemiological Method of Pseudomonas aeruginosa.

INTRODUCTION: From 2018, IR Biotyper (IRBT; Bruker Daltonik GmbH, Germany) based on the Fourier transform infrared spectrophotometer has begun to be introduced as a new strain classification method in the field of clinical microbiological examination. We compared it with molecular epidemiology method to evaluate the usefulness of strain classification by IRBT. METHOD: Homology of strain classification with molecular epidemiology method (Multilocus Sequencing Typing; MLST and PCR-based ORF Typing; POT) for 48 strains of Pseudomonas aeruginosa with different detection times from multiple institutions to evaluate the accuracy of IRBT was compared. RESULTS: IRBT used "KBM" SCD agar medium for preculture and was classified into 12 types when classified by Cut-off value 0.181, 8 types by MLST, and 13 types by POT. In the Adjusted Wallace between IRBT and molecular epidemiology method, MLST was 0.458 (95% CI; 0.295 to 0.620) and POT was 0.330 (95% CI; 0.135 to 0.525), indicating a discrepancy in strain classification. CONCLUSION: No correlation was found between IRBT and the classification results by the molecular epidemiology method. In the molecular epidemiology method, strains are classified by matching only specific gene regions, but IRBT irradiates a sample with an infrared laser and classifies the strains according to the difference in absorption spectrum according to the molecular structure, so the measurement principle is different. When classifying strains by IRBT, it is desirable to grasp the clinical information of the detected strains and to target multiple strains isolated at the same facility at the same time.

Rapid detection method of carbapenemase-producing Enterobacteriaceae by MALDI-TOF MS with imipenem/cilastatin (KB) disc and zinc sulfate solution.

INTRODUCTION: Carbapenemase-producing Enterobacteriaceae (CPE) is a major global health threat, and development of rapid detection methods is desired. Here, we established a cost-effective and relatively rapid CPE detection method using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). METHODS: We examined 134 CPE strains (IMP-type, NDM-type, VIM-type, KPC-type, OXA-48-like-type, and GES-type) and 107 non-CPE strains, previously confirmed by genetic tests. The proposed MALDI-TOF MS method involves mixing of a carbapenem drug [here, the commercially available imipenem (IPM) KB disc] and the bacterial strains to be tested, and the consequent drug hydrolysis owing to bacterial carbapenemase activity is confirmed by a waveform spectrum before and after 2 h of the mixing. As metallo-beta-lactamases require zinc in their active site, the false-negatives obtained from our method were cultured in presence of zinc sulfate solution and tested again. RESULTS: Based on the presence or absence of the IPM (+cyano-4-hydroxy-cinnamic acid)-specific waveform peak near 489.45 m/z (±500 ppm), the detection sensitivity and specificity of our method for CPE were determined to be 94.8% and 91.6%, respectively. Seven false-negatives of IMP-type (4), VIM-type (2), and GES-type (1) were found, of which the IMP- and VIM-types tested positive as CPE after culture with zinc sulfate solution. Thus, the overall detection sensitivity improved to 99.3%. CONCLUSION: Our study proposes a new approach for CPE detection using MALDI-TOF MS. Moreover, we propose cultivation of test strains with zinc sulfate solution for efficient detection of IMP-type CPE, not only for MALDI-TOF MS, but also for other detection methods.

[Comparative Verification of DNA Extraction Methods for Bacterial Nucleic Acid Amplification Test].

Genetic testing is widely used as a rapid diagnostic method to identify microorganisms and detect antibiotic resistance genes. The nucleic acid to be analyzed is located inside the cell wall, the cell membrane or nuclear envelope. Therefore, it is essential to disassemble them in nucleic acid extraction operation. It is also necessary to remove or inactivate interfering substances by exposing cytoplasmic components accompanying cell disruption. Nucleic acid extraction is an indispensable task, but depending on the selected method, it may have a significant effect on the genetic test results. However, the DNA extraction method that is actually selected tends to emphasize work efficiency, and the appropriate evaluation of the extraction operation is neglected. In this study, we focused on the purity of the extracted DNA, and examined six existing extraction methods and original extraction methods using Gram-negative bacilli as a simple model. As a result, there was a large difference in DNA purity depending on the extraction method. When used in a qualitative gene amplification test, there was a difference in the shading of the bands. However, the detection of resistance genes all gave similar results. Furthermore, as a result of using the original extraction method, the extraction method using sodium decylbenzenesulfonate (SDBS) was the most excellent extraction method from the viewpoint of recovered DNA and operability.

[Development and Evaluation of Screening Culture Medium for Detection of Drug-Resistant Gram Negative Rods Containing Stealth Type CPE].

There is a report that an infection by medicine resistant bacteria will be the number one cause of death in 2050 according to the recommendation of WHO, and the CPE (carbapenem-producing Enterobacteriaceae) infection is regarded as a problem in particular. When detecting CPE, it is important how to detect stealth type CPE sensitive to carbapenem series medicines. So we used the 2 types of screening culture medium, "KBM" CRE-JU culture medium (CRE-JU culture medium) and the FRPM culture medium, and tried to detect drug-resistant gram-negative bacilli such as CPE, stealth type CPE, ESBL-producing bacteria, and excess AmpC-producing bacteria (AmpC-producing bacteria), etc. in combination of this culture mediums. As a result, CRE-JU culture medium showed a difference in the growth of CPE depending on the amount of inoculated bacteria while ß-lactamase non-producing strain and other strains except for high concentration ESBL-producing bacteria and AmpC-producing bacteria were un-growing. Most of the CRE, stealth type CPE, ESBL-producing bacteria and AmpC-producing bacteria grew in the FRPM culture medium while most of the ß-lactamase non-producing strains with a MIC value of meropenem (MEPM) of 2 µg/mL or less were un-growing. From these results, it was suggested that when a strain grown on CRE-JU and FRPM culture mediums, it could be distinguished as CPE, and when strains grown on FRPM culture medium which were un-grown on CRE-JU culture medium, it could be distinguished as drug-resistant bacteria such as stealth type CPE, ESBL-producing bacteria, and AmpC-producing bacteria. When strains not grown on CRE-JU and FRPM culture mediums, it could be distinguished as sensitive.

Correlations between Resistance Classifications Based on Penicillin-Binding Protein Genotypes and Antimicrobial Susceptibility Test Results of Haemophilus influenzae.

There are several problems associated with antimicrobial susceptibility testing (AST) of Haemophilus influenzae. ß-Lactamase-negative ampicillin-resistant H. influenzae (BLNAR) isolates with minimum inhibitory concentration (MIC) of ampicillin (ABPC) <4 mg/l will be classified as susceptible according to the MIC breakpoint of the CLSI M100 criteria, in spite of harboring penicillin-binding protein (PBP) mutations that cause ABPC resistance. A total of 103 isolates were collected from clinical materials for analysis. The genotypes of the PBP mutations were analyzed by polymerase chain reaction. The WalkAway 96 Plus (WALKAWAY), dry plate Eiken (DP-EIKEN), and RAISUS S4 systems (RAISUS) were used for AST. HTM broth was used as the culture medium for WALKAWAY, Mueller‒Hinton broth with 5% lysed horse blood for DP-EIKEN, and HTM with 5% horse serum for RAISUS. The MIC concordance rates of ABPC for g-BLNAR, for RAISUS vs. DP-EIKEN, RAISUS vs. WALKAWAY, and DP-EIKEN vs. WALKAWAY were 96.1, 86.4, and 85.4%, respectively. WALKAWAY had a low correlation with the other two systems. Moreover, concordance rates of ABPC MIC ≥4 mg/l, which is considered as resistant, of 69 g-BLNAR isolates for the RAISUS, DP-EIKEN, and WALKAWAY systems were 68.1, 58.0, and 37.7%, respectively. Therefore, in Japan, where the BLNAR strain is isolated at a high frequency, it is necessary to understand the characteristics of the measuring systems to appropriately interpret the test results.

[Construction of System to Making Antibiograms Based was used by Japan Nosocomial Infections Surveillance (JANIS) Data].

Making the antibiogram necessary for infectious disease treatment is an important operation of the microbiology laboratory. Antibiogram is required to be up-to-date and to keep up with the annual updates of the Clinical & Laboratory Standards Institute (CLSI). However, these operation and managements require a lot of effort. In addition, even in the surveillance and analysis comparison of multiple facilities, the difference in CLSI base year becomes a barrier, making unified analysis difficult. On the other hand the antibiogram by Japan Nosocomial Infections Surveillance (JANIS) has restrictions on the bacterial species, antibacterial agents, and date range. Accordingly we focused on the fact that the data transmitted to JANIS is in a common format, and attempt construction a system to making the antibiogram based on this. This system uses data transmitted to JANIS, is convenient, can use not only the latest but also past base year CLSI category, has no restrictions on bacterial species, antibacterial agents, date range, works on Microsoft Windows environment, pursuit of compliance with the guidelines, and automatically making the antibiogram.

[Investigation of Skin Adherent Bacterial Flora in Dogs by MALDI-TOF MS and 16S rRNA Gene Analysis].

Due to the increase in the number of companion animal breeders in Japan, there are more opportunities for companion animals to come into contact with humans than before. Therefore, we investigated the bacterial flora adhering to the skin of dogs and the bacterial flora was analyzed for the presence of zoonotic bacteria that infect humans from companion animals. With the cooperation of students enrolled in the Department of Medical Technology and Science, Faculty of Fukuoka Health Care, International University of Health and Welfare. 39 samples were collected from the abdomen, back and paws of 13 healthy dogs using sterile swabs by the scraping method. The isolation culture was carried out only for facultative anaerobic bacteria to obligate aerobic bacteria and Bacterial identification was determined by MALDI-TOF MS and 16S rRNA gene analysis. Among the identified strains were Pasteurella canis, Staphylococcus pseudintermedius, Staphylococcus intermedius, which were difficult to detect in humans. The overall ratio of detected bacteria was 35% for coagulasenegative staphylococci, 14% for coagulase-positive staphylococci, 5% for Enterobacteriaceae, and 45% for natural environment. In the future, it is expected that extended-spectrum ß-lactamase producing bacteria and drug-resistant bacteria such as Carbapenem-resistant enterobacterales will also be transmitted to humans through contact with companion animals.

[Reliability of the Identification Result of Score Value ≧2.000 with the MALDI Biotyper: What Kind of Polymicrobial Species Are Included].

Identification of bacteria by using MALDI Biotyper is relevant at the species category if Score Value (SV) is not less than 2.000. However, in practical examination, the analysis by MALDI Biotyper frequently produces the multiple candidate bacterial species with SV ≥2.000. In this study, we analyzed the ratio of multiple results among 10,081 specimens and identified the species of bacteria with high frequency of multiple results. Our analysis indicated that 8,129 strains out of 10,081 strains examined from July 2015 to July 2017, showed multiple identification results with MALDI Biotyper, and that multiple result was obtained in 4.9% of gram positive cocci analysis, 5.8% of gram positive rods, 25.4% of gram negative cocci, 16% of gram negative rod, none of fungus. In particular, MALDI Biotyper analysis of Enterobacter spp. (E. cloacae, E. asburiae, E. kobei, etc.), Acinetobacter spp. (A. baumannii, A. nosocomialis, A. pittii etc.), Neisseria spp. (N. flavescens, N. perflava etc.) had high ratios of multiple results. Our data suggests that genetic homology among bacteria results in multiple results of bacteria identification. The mass spectrometer method is the rapid test for bacteria identification. However, for obtaining higher specificity, it is required to combine with other methods. Furthermore, systematic annotation of bacteria is highly recommended.

[On the identification accuracy of MALDI-TOF MS influence of pretreatment methods, types of medium, coating skills, and preservation methods].

In bacterial identification by MALDI-TOF MS, there are many reports of usefulness concerning direct identification from blood culture and identification of bacteria which cannot be identified with automatic analysis equipment. On the other hand, there are very few studies that investigate how various conditions influence on identification accuracy, such as the type of medium used for bacterial isolation and pure culture, the pretreatment methods, the difference in coating technique, and preservation methods. Therefore, we examined 10 strains of 2 drug-resistant bacteria species and 9 strains of 1 unnormal bacterium species. As a result, no significant differences were found in accuracy of identifying all strains of the target bacteria incubated for 24 hours and changing the types of medium, the pretreatment methods, and the coating techniques. In particular, methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum ß-lactamase (ESBL) producing Escherichia coli showed little change in the score value and the mass spectrum that assayed every 24 hours during the preservation period in all of the medium. In the case of Vibrio vulnificus, however, identification accuracy was decreased by the specific medium and storage conditions. It is suggested as this factor that the growth state of bacteria may have influenced the identification accuracy.

[On the performance evaluation of VersaTREK introduced in blood culture].

We evaluated performance of Versa TREK, blood culture system used in our hospital. Compared with BacT/ALERT 3D, the detection time of bacteria in the VersaTREK was shorter in most of strains. Compared with BacT/ALERT Virtuo, there was little difference in the detection time of bacteria. In addition, VersaTREK was able to detect Helicobacter cinaedi which could not be detected by other equipment, and H. cinaedi was detected in clinical specimens within 2 days. There were 147 bottles judged to be false positives at our facility, of which 7,290 were 2,0% of the total. Ninety one points eight percentage of the cause was due to the change in the temperature inside the device, 3.4% was due to incorrect procedure. So, it is considered that false positives are further decreased by appropriate management of the installation and sample collection.

[A trial of simple and rapid carbapenemase big five gene analysis using LAMP method].

Reliable detection and typing of carbapenemase is important in the treatment of infectious diseases. In this study we newly designed LAMP primer based on the latest information, and established a detection method for Carbapenemase Big five gene. For DNA extraction from strains, alkaline boiling method and commercial kit were used. The reaction temperatures of the LAMP method was VIM: 65°C, NDM: 63°C, KPC: 65°C, OXA-48-like: 65°C, IMP: 61°C. And simultaneous LAMP method was at 63°C, for 60 min. It was possible to detect up to 103 copies/ml. The reactivity of LAMP using 36 strains verified by Multiplex-PCR was VIM (4/4: number of LAMP method positive strains/number of strains evaluated), NDM (2/2), KPC (4/4), OXA-48-like (4/4), IMP (17/17). The type of carbapenemase determined by the LAMP method were all consistent with multiplex PCR. All strains were detected within 30 min. In VIM, both VIM-1-like and VIM-2-like were able to detect. In this study, although the number and variation of the strains evaluated was limited, LAMP method was clinically useful as a simple and rapid carbapenemase detection method.

[Evaluation of novel nucleic acid detection kit for Mycoplasma pneumoniae].

For diagnosis of Mycoplasma pneumoniae infection, highly sensitive and rapid diagnosis is important. Because antibiotics are limited for the treatment of M. pneumoniae infection. In this study, we evaluated new rapid nucleic acid detection kit for M. pneumoniae. This kit does not require excessive pretreatment of specimens and molecular diagnosis of M. pneumoniae is possible within 40 min. Using 120 nasopharyngeal specimens, we compared this kit with a commercially available molecular diagnostic reagent (LAMP). 51 of 120 cases were M. pneumoniae positive, and the results of both assays were all consistent. In addition, sequencing of 23S rRNA gene was performed on 51 cases positive for M. pneumoniae. As a result, macrolide resistance mutation (2063A>G) was observed in 19 cases (37.3%). The gene mutations estimated by this kit coincided completely with the sequencing. In conclusion, new rapid nucleic acid detection kit could detect M. pneumoniae with the same sensitivity as other molecular diagnostics, in a simple process.

[Development and Evaluation of a New Selective Culture Medium, KBM Anaero RS-GNR, for Detection of Anaerobic Gram Negative Rods].

The laboratory culture methods for isolating drug-resistant pathogens has been the gold standard in medical microbiology, and play pivotal roles in the overall management of infectious diseases. Recently, several reports have emphasized the development of antibiotics-resistance among anaerobic gram-negative rods, especially Genus Bacteroides and Prevotella. Therefore, a selective culture method to detect these pathogens is needed. We developed here the new selective culture medium, termed "KBM Anaero RS-GNR," for detecting anaerobic Gram-negative rods. Growth capability and selectivity of the agar medium were assessed by using the pure culture suspensions of more than 100 bacterial strains as well as the 13 samples experimentally contaminated with these bacterial strains. This new medium, "KBM Anaero RS-GNR," successfully showed the selective isolation of anaerobic Gram-negative rods. Compared with commercially available medium, "PV Brucella HK Agar, " which is also designed to detect anaerobic Gram-negative rods, there was no significant difference of the overall detection efficiency between two media. However, "KBM Anaero RS-GNR" showed superior to selectivity for anaerobic Gram-negative rods, especially from the samples contaminated with Candida species. Thus, the culture method using KBM Anaero RS-GNR is relevant for isolation of anaerobic Gram-negative rods especially from clinical specimens.

[Utility of the Rapid Staining with the Use of Microwave for Detection of Genus Mycobacterium].

Recently, many laboratories use fluorescence microscopy for rapid screening of clinical specimens for detection of Genus Mycobacterium. The success of the stain depends on the staining temperature at which the fluorescent dye could uniformly penetrate the cell wall through waxy lipid barrier of the mycobacterial organism. Therefore, this process requires a precise heating control. In this study, to control the temperature during fluorescent auramine- rhodamine staining, we explored the potential use of microwave. The efficiency of microwave irradiation during the staining process was evaluated by using a Mycobacterium avium-containing sputum of which the smear slide was irradiated with several different conditions in combination of time and wattage. As a result, 1) the liquid temperature of the stain correlated well with wattage of microwave irradiation. 2) The tubercle bacilli were easily visualized as brilliant fluorescent bacilli in an orange color when it was set at the best condition of 600 W and 10 sec irradiation. 3) The sensitivity of microscopy with this staining method (MW method) was higher than those of conventional staining methods such as Ziehl-Neelsen staining and standard auramine-rhodamine staining, demonstrating that MW method can be applicable to the sputum slides which contained a few bacilli. Thus, we established the new staining method that is rapid and easy to perform in clinical laboratories. Since the MW method has not yet been utilized in order to conduct fluorescence microscopy for sputum smears, advancement on this method will make a vast change in testing of acid fast bacilli.