崔 龍洙

<title>Abstract</title><sec> <title>Purpose</title> We aimed to investigate whether low-intensity continuous and pulsed wave ultrasound (US) irradiation can inhibit the formation of <italic>Staphylococcus epidermidis</italic> biofilms, for potential application in the treatment of catheter-related bloodstream infections (CRBSI). </sec><sec> <title>Methods</title> <italic>S. epidermidis</italic> biofilms that formed on the bottom surfaces of 6-well plates were irradiated on the bottom surface using the sound cell incubator system for different intervals of time. </sec><sec> <title>Results</title> US irradiation with continuous waves for 24 h notably inhibited biofilm formation (<italic>p</italic> &lt; 0.01), but the same US irradiation for 12 h had no remarkable effect. Further, double US irradiation with pulsed waves for 20 min inhibited biofilm formation by 33.6%, nearly two-fold more than single US irradiation, which reduced it by 17.9%. </sec><sec> <title>Conclusion</title> US irradiation of a lower intensity (<italic>I</italic>_SATA = 6–29 mW/cm²) than used in a previous study and lower than recommended by the Food and Drug Administration shows potential for preventing CRBSI caused by bacterial biofilms. </sec>

The bacteriophage (or phage for short) has been used as an antibacterial agent for over a century but was abandoned in most countries after the discovery and broad use of antibiotics. The worldwide emergence and high prevalence of antimicrobial-resistant (AMR) bacteria have led to a revival of interest in the long-forgotten antibacterial therapy with phages (phage therapy) as an alternative approach to combatting AMR bacteria. The rapid progress recently made in molecular biology and genetic engineering has accelerated the generation of phage-related products with superior therapeutic potentials against bacterial infection. Nowadays, phage-based technology has been developed for many purposes, including those beyond the framework of antibacterial treatment, such as to suppress viruses by phages, gene therapy, vaccine development, etc. Here, we highlighted the current progress in phage engineering technology and its application in modern medicine.

We report the complete genome sequence of <named-content content-type="genus-species">Mycobacterium heckeshornense</named-content> strain JMUB5695, which was isolated from necrotizing granulomatous lesions in a lung cancer patient. The complete genome consists of a 4,865,109-bp chromosome with a GC content of 65.9% and contains no plasmids.

Influenza outbreaks at geriatric long-term care facilities (g-LTCFs) can be deadly and their prevention is important. However, the factors influencing disease transmission in g-LTCFs remain controversial. In this descriptive study, we tried to identify the potential risk factors influencing influenza outbreaks that occurred in different influenza seasons within a single g-LTCF with 100 residents in Gunma Prefecture. We reviewed the detailed facility records for all influenza cases in both residents and staff between January 2012 and June 2020. Facility preventive measures were also reviewed. We found that community meals may have been a potential source of transmission leading to the outbreaks. When influenza infection is noted, implementation of strict preventive measures and restriction of meal provision to resident rooms may help to prevent disease transmission and the development of an outbreak. Such measures may also be useful to prevent the transmission of other serious droplet-borne diseases within g-LTCFs.

Differences in the gut microbial content of Lutzomyia (Lu.) ayacuchensis, a primary vector of Andean-type cutaneous leishmaniasis in Ecuador and Peru, may influence the susceptibility of these sand flies to infection by Leishmania. As a first step toward addressing this hypothesis, a comparative analysis of bacterial and fungal compositions from Lu. ayacuchensis populations with differential susceptibilities to Leishmania was performed. Bacterial 16S rRNA gene amplification and Illumina MiSeq sequencing approaches were used to characterize the bacterial composition in wild-caught populations from the Andean areas of Ecuador and southern Peru at which the sand fly species transmit Leishmania (Leishmania) mexicana and Leishmania (Viannia) peruviana, respectively, and a population from the northern Peruvian Andes at which the transmission of Leishmania by Lu. ayacuchensis has not been reported. In the present study, 59 genera were identified, 21 of which were widely identified and comprised more than 95% of all bacteria. Of the 21 dominant bacterial genera identified in the sand flies collected, 10 genera had never been detected in field sand flies. The Ecuador and southern Peru populations each comprised individuals of particular genera, while overlap was clearly observed between microbes isolated from different sites, such as the number of soil organisms. Similarly, Corynebacterium and Micrococcus were slightly more dominant bacterial genera in the southern Peru population, while Ochrobactrum was the most frequently isolated from other populations. On the other hand, fungi were only found in the southern Peru population and dominated by the Papiliotrema genus. These results suggest that variation in the insect gut microbiota may be elucidated by the ecological diversity of sand flies in Peru and Ecuador, which may influence susceptibility to Leishmania infection. The present study provides key insights for understanding the role of the microbiota during the course of L. (L.) mexicana and L. (V.) peruviana infections in this important vector.

The emergence of antimicrobial-resistant bacteria is an increasingly serious threat to global health, necessitating the development of innovative antimicrobials. Here we report the development of a series of CRISPR-Cas13a-based antibacterial nucleocapsids, termed CapsidCas13a(s), capable of sequence-specific killing of carbapenem-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus by recognizing corresponding antimicrobial resistance genes. CapsidCas13a constructs are generated by packaging programmed CRISPR-Cas13a into a bacteriophage capsid to target antimicrobial resistance genes. Contrary to Cas9-based antimicrobials that lack bacterial killing capacity when the target genes are located on a plasmid, the CapsidCas13a(s) exhibit strong bacterial killing activities upon recognizing target genes regardless of their location. Moreover, we also demonstrate that the CapsidCas13a(s) can be applied to detect bacterial genes through gene-specific depletion of bacteria without employing nucleic acid manipulation and optical visualization devices. Our data underscore the potential of CapsidCas13a(s) as both therapeutic agents against antimicrobial-resistant bacteria and nonchemical agents for detection of bacterial genes.

The association of Panton-Valentine leukocidin (PVL) toxin with necrotizing soft tissue infection (NSTI) caused by <named-content content-type="genus-species">Staphylococcus aureus</named-content> remains controversial. Here, we report the complete genome sequence of the PVL-negative <named-content content-type="genus-species">S. aureus</named-content> strain JMUB1273, isolated from a patient with pervasive NSTI.

[This corrects the article DOI: 10.14252/foodsafetyfscj.2018003.].

Severe community-acquired pneumonia (CAP) caused by methicillin-resistant Staphylococcus aureus (MRSA) is relatively rare and is usually associated with rapid progression to death. Here, we report the complete genome sequence of the MRSA strain JMUB3031, which was isolated from a patient with fatal CAP.

BACKGROUND: Staphylococcus caprae is an animal-associated bacterium regarded as part of goats' microflora. Recently, S. caprae has been reported to cause human nosocomial infections such as bacteremia and bone and joint infections. However, the mechanisms responsible for the development of nosocomial infections remain largely unknown. Moreover, the complete genome sequence of S. caprae has not been determined. RESULTS: We determined the complete genome sequences of three methicillin-resistant S. caprae strains isolated from humans and compared these sequences with the genomes of S. epidermidis and S. capitis, both of which are closely related to S. caprae and are inhabitants of human skin capable of causing opportunistic infections. The genomes showed that S. caprae JMUB145, JMUB590, and JMUB898 strains contained circular chromosomes of 2,618,380, 2,629,173, and 2,598,513 bp, respectively. JMUB145 carried type V SCCmec, while JMUB590 and JMUB898 had type IVa SCCmec. A genome-wide phylogenetic SNP tree constructed using 83 complete genome sequences of 24 Staphylococcus species and 2 S. caprae draft genome sequences confirmed that S. caprae is most closely related to S. epidermidis and S. capitis. Comparative complete genome analysis of eight S. epidermidis, three S. capitis and three S. caprae strains revealed that they shared similar virulence factors represented by biofilm formation genes. These factors include wall teichoic acid synthesis genes, poly-gamma-DL-glutamic acid capsule synthesis genes, and other genes encoding nonproteinaceous adhesins. The 17 proteinases/adhesins and extracellular proteins known to be associated with biofilm formation in S. epidermidis were also conserved in these three species, and their biofilm formation could be detected in vitro. Moreover, two virulence-associated gene clusters, the type VII secretion system and capsular polysaccharide biosynthesis gene clusters, identified in S. aureus were present in S. caprae but not in S. epidermidis and S. capitis genomes. CONCLUSION: The complete genome sequences of three methicillin-resistant S. caprae isolates from humans were determined for the first time. Comparative genome analysis revealed that S. caprae is closely related to S. epidermidis and S. capitis at the species level, especially in the ability to form biofilms, which may lead to increased virulence during the development of S. caprae infections.

Electroporation is a common technique necessary for genomic manipulation of Staphylococci. However, because this technique has too low efficiency to be applied to some Staphylococcal species and strains, especially to coagulase-negative Staphylococcus (CNS) isolates, basic researches on these clinically important Staphylococci are limited. Here we report on the optimization of electroporation parameters and conditions as well as on the generation of a universal protocol that can be efficiently applicable to both CNS and Coagulase-positive Staphylococci (CPS). This protocol could generate transformants of clinical Staphylococcus epidermidis isolate, with an efficiency of up to 1400 CFU/μg of plasmid DNA. Transformants of 12 other clinically important Staphylococcal species, including CNS and CPS, were also generated with this protocol. To our knowledge, this is the first report on successful electroporation in nine these Staphylococcal species.

BACKGROUND: Increasing evidence has indicated that Staphylococcus aureus pneumonia complicated with influenza virus infection is often fatal. In these cases, disease severity is typically determined by susceptibility to antimicrobial agents and the presence of high-virulence factors that are produced by Staphylococcus aureus, such as Panton-Valentine leukocidin (PVL). CASE REPORT: We describe a rare case of fatal community-acquired pneumonia caused by methicillin-sensitive Staphylococcus aureus (MSSA), which did not secrete major high-virulence factors and coexisted with influenza type B infection. The 32-year-old previously healthy male patient presented with dyspnea, high fever, and cough. His roommate had been diagnosed with influenza B virus infection 3 days earlier. Gram-positive clusters of cocci were detected in the patient's sputum; therefore, he was diagnosed with severe pneumonia and septic shock, and was admitted to the intensive care unit. Despite intensive antibiotic and antiviral treatment, he died of multiple organ failure 5 days after admission. His blood culture from the admission was positive for MSSA, and further analysis revealed that the strain was negative for major high-virulence factors, including PVL and enterotoxins, although influenza B virus RNA was detected by PCR. CONCLUSIONS: Physicians should pay special attention to patients with pneumonia following influenza and Staphylococcus aureus infection, as it may be fatal, even if the Staphylococcus aureus strain is PVL-negative and sensitive to antimicrobial agents.

2008年に, われわれは黄色ブドウ球菌 (S. aureus) におけるvancomycin (VAN) 耐性を検討する過程でVANとlinezolid (LZD) の感受性の逆相関関係を見出した (Watanabe Y, et al: Antimicorb Agents Chemother, 2008; 52: 4207-4208). 本研究ではその遺伝学的メカニズムの解明を目指し, 以下の実験を行った. まず, 世界各国で分離されたvancomycin-intermediate S. aureus (VISA) 株を, VAN耐性に影響することが知られている遺伝子の変異タイプ別にrpoB, vraSR, graRS, clpP, およびwalRK変異グループに分け, LZDとVCMの感受性を検討した. これら40株中, rpoB, vraSR, graRS, clpPおよびwalRKの変異株数はそれぞれ29 (72.5%), 9 (22.5%), 4 (10%), 3 (7.5%) および23 (57.5%) であった. そのうちrpoB変異グループがLZDに最も高感受性であった. また, hVISA Mu3株およびそのgraRとrpoB変異株を用いて行った感受性のpopulation解析では, rpoB変異株におけるLZDの顕著な高感受性化がみられた. 一方, graR変異株ではLZDの高感受性化より, VANの低感受性化が顕著であった. 次に臨床分離MRSA7株からrifampicin (RIF) およびVANで選択したVAN低感受性変異株それぞれ41株 (MRSA-RIF) と46株 (MRSA-VAN) を用い, LZDおよびVCMのMinimum inhibitory concentration (MIC) を測定した. MRSA-RIFとMRSA-VANは親株に比べLZDに対して高感受性化し, MICはそれぞれ0.45±0.25mg/lおよび0.24±0.28mg/l減少した. 一方で, MRSA-RIFおよびMRSA-VANは親株に比べVANに対して低感受性化し, MICはそれぞれ0.40±0.37mg/lと1.21±0.74mg/l上昇した. さらに, rpoB変異によるLZDとVCMの感受性への影響を明らかにする目的で, VANに感受性のMRSA株N315ΔIPをRIF 1mg/lで選択して得られたrpoB変異株の, VANおよびLZDの感受性を検討した. その結果, LZDにおいては全株で高感受性化が認められたが, VANでの低感受性化は1株を除いて認められなかった. 以上の結果から, 黄色ブドウ球菌におけるLZDの高感受性化には, rpoB変異が最も強く関連していると考えられた. また, RIF耐性黄色ブドウ球菌感染症の治療に, LZDが有効である可能性も示唆された.