Genetic testing is classified into three categories as nucleic acids testing of infectious diseases, somatic and germline genes testing. From the experiences of genomic testing on COVID-19, the importance of accuracy and standardization of PCR testing were re-recognized. The third-party accreditation of laboratory medicine is beneficial for the improvement of the analytic validity of the genomic and precision medicine such as comprehensive cancer gene panel tests（CGP tests）. The genetic testing of incurable diseases and reproductive technics will be shortly supported by public health insurance. The necessity of the proficiency testing（PT）and external quality assessments（EQA）for tumor genetic testing using clinical samples as well as standard reference materials is important. The clinical data sharing system based on the companion diagnostics（CDx）is indispensable for the precision medicine. Further, the bringing up by the on-the-job training of the staffs including surgeons in the hospital are necessary to promote the genomic and precision medicine in Japan. To establish the system of PT/EQA for laboratory developed tests（LDTs）is essential for genomic and precision medicine via the experience of SARS-CoV-2 detection in Japan. This review described the minimal essence and concept of genetic testing that is necessary for surgeons in Japan.

The pitfalls of nucleic acid amplification test for microorganisms in infectious diseases were reviewed. In real-life clinical practice, the principal pitfalls were false-negative results with the detection of gene in non-viable organisms post-treatment, the impact of sampling error, false-positive results due to contamination, false-negative results due to the target genetic mutation of nucleic acid amplification test, misinterpretation between assay time and turn around time. The understanding and attention to these pitfalls in genetic detection test will lead to get the trick well.

Genetic testing can provide comprehensive information of a causative pathogen of infectious disease including its virulence and drug resistance, allowing for tailored interventions and improvement of health outcome in patient. Despite its benefits for the diagnosis and treatment of infectious disease, the introduction of genetic testing lacked widespread use beyond general medical facilities because of technical and cost consideration. However, as the outbreak of COVID-19 forced many clinical facilities to introduce various gene-testing equipment, the knowledge and techniques acquired for the identification of SARS-CoV-2 genetic testing might be utilized for the diagnosis of various infectious diseases even after the epidemic is over. Since 2016, our hospital has accepted requests for the genetic testing of various pathogenic microorganisms from medical institutions in the Kinki region to support the treatment of infectious diseases in community medicine. In this article, we report the usefulness of genetic testing and our efforts to provide rapid and accurate test results to help the treatment of infectious diseases. We also introduce examples of the clinical cases including surgical site infection that were diagnosed by genetic testing.

The Nucleic Acid Amplification Test (NAAT) is now covered by insurance as a test for Clostridioides difficile infection (CDI). However, it has not been established whether culture and toxigenic culture (TC) test should be performed in conjunction with NAAT, and we investigated the necessity of these tests. The subjects were 336 diarrhea samples submitted for detection of Clostridioides difficile antigen (GDH) and toxin: The number of GDH-positive/toxin-positive cases were 10, GDH-positive/toxin-negative cases were 32, and GDH-negative/toxin-negative cases were 294．Of the 13 GDH-positive/toxin-negative and NAAT-negative cases, the 7 culture-positive cases were all TC test negative. This suggested that there was little necessity for additional TC testing in the case of GDH-positive/toxin-negative and NAAT-negative. Among 294 GDH-negative/toxin-negative cases, NAAT-positive cases were 1.7% (5/294) and TC test-positive cases were 4.1% (12/294). Although the likelihood of positive NAAT or TC tests in GDH-negative/toxin-negative cases is low, CDI may be present, and TC test or NAAT may be considered, especially if CDI is strongly suspected.

Staphylococcus aureus bacteremia cases have a poor prognosis, and if MRSA is detected, the mortality rate is even higher. In addition to S. aureus, coagulase-negative staphylococci (CNS) are also frequently detected as causative organisms in surgical infections. In the present study, we investigated the usefulness of the mecA gene in 29 cases of surgical infections (21 MSSA, 3 MRSA, and 5 CNS) in which Staphylococcus spp. were detected from blood cultures. In all cases, initial therapeutic drugs were considered based on the mecA gene test results, and antimicrobial agents were optimized before susceptibility testing was performed.

Objective: In this study, we evaluated Verigene^® BC-GN（VBG）in the point of clinical performance and the effect for promoting the proper use of antimicrobial agents, against the Gram-negative rods（GNR）bacteremia. Methods: We evaluated the VBG performance of the method by comparison with conventional microbiology method for the blood-culture detected GNR. Additionally, we investigated the history of antimicrobial administration. Results: Eighty-one sets of positive blood-culture were tested by VGB. The concordance rates between VBG and conventional microbiology method was 97.7％. The sensitivity and specificity of VBG antimicrobial-resistant gene detection were 72.7％ and 98.6％, respectively. For the history of antimicrobial administration, in the case of antimicrobial resistant-gene detected by VGB, most of cases became targeted therapy. In the case of antimicrobial resistant-gene not detected by VBG, only 37.5％ of cases were de-escalated from carbapenems. And, there were three antimicrobials resistant GNR that harbored the nontarget resistant-gene of VBG. Conclusions: VBG may contribute to rapid targeted therapy in the case of antimicrobial resistant-gene detected. By contrast, in the case of antimicrobial resistant-gene not detected, select of the antimicrobial required careful consideration for de-escalation.

In microbiological testing, morphological tests such as smear specimens and biochemical identification after isolation and culture have been the mainstay. Recently, however, mass spectrometry and genetic testing are expected to become new testing instruments. Genetic testing is highly versatile and can detect drug resistance genes and pathogenic genes in addition to detecting microorganisms. The use of genetic testing has been limited due to the need for special techniques and equipment, but with the development of fully automated equipment, its use is expected to increase. It is also useful in the diagnosis of bloodstream infections and postoperative pneumonia, which are important surgical infections. Since genetic testing does not completely replace smear and culture tests, it must be used separately from conventional testing methods. We would like to understand the advantages and disadvantages of genetic testing so that it can be used in the treatment of surgical infections.

Bacterial translocation (BT) has several causes; however, in most cases BT depends on bowel obstruction, such as an ileus. Herein we present a case involving a patient who developed septicemia due to BT after surgery for colon cancer. An 88-year-old woman underwent bypass surgery between the small bowel and colon for an inoperative tumor. After surgery, her general condition was stable and her diet was restarted on postoperative day 4．On postoperative day 7, she suddenly developed a high fever ＞ 40℃ with blood pressure reductions. Septic shock was diagnosed, and Klebsiella oxytoca and Enterobacter cloacae were confirmed in peripheral blood specimens. Because there was no evidence of leakage peritonitis or other causes, BT was the most likely cause of the septic shock. After systemic therapy with antibiotics and vasopressor, her symptoms improved. There were no complications thereafter and she was discharged from the hospital in stable condition.