Name: mrsa: host adaptation and transmission
Uploaded: 2026-03-12T13:36:05.000Z
Duration: 1 min 25 s
Channel: JoVE

抗生物質耐性とは、微生物が抗生物質の影響に耐えられる能力のことです。よく知られている病原体である 黄色ブドウ球菌はメチシリン耐性を発達させ、その結果、メチシリン耐性黄色 ブドウ球菌(MRSA)が発症しました。MRSAは人間の皮膚や軟部組織に深刻な感染症を引き起こし、世界中で毎年数百万件の入院や死亡を引き起こしています。高齢者や免疫抑制患者は、広域抗生物質の長期かつ広範な使用により最もリスクが高いです。MRSA対策の戦略には、植物化学物質、ファージ療法、ナノ粒子、プロバイオティクスの利用が含まれます。植物から抽出される二次代謝物である植物化学物質は、MRSAの増殖を抑制するために広く使われています。MRSA特異的ファージは細胞溶解を誘導することでMRSAの集団を減らすことができます。ナノ粒子は細胞内で重金属イオンを放出することで応力をかけます。膜の透過性を変化させ、重要な細胞機能を妨げます。最後に、一部のプロバイオティクス株はMRSAの増殖を抑制する抗菌化合物を分泌します。

抗生物質耐性の臨床的意義

Clinical Significance of Antibiotic Resistance

メチシリン耐性 黄色ブドウ 球菌(MRSA)は、ブドウ球菌カセット染色体メック(SCCmec)内で mecA 遺伝子を獲得しることで、βラクタム抗生物質に抵抗する能力から、重大な公衆衛生上の脅威を示しています。この遺伝子はペニシリン結合タンパク質2a(PBP2a)をコードしており、メチシリンや他のβ-ラクタムの結合効果を損なう。MRSAは人間と動物の両方に影響を与える独自のクローン系統へと進化し、ワンヘルスの枠組みにおけるその重要性を強化しています。MRSA株は、医療関連株(HA-MRSA)、地域関連株(CA-MRSA)、家畜関連株(LA-MRSA)に分類されます。これらの系統はクローン複合体(CC)変異と宿主特異性を示します。例えば、CC398は元々人為由来でしたが、特に豚などの家畜に適応し、逆人獣共患感染につながりました。CC1、CC5、CC8、CC97などの複数のCCが宿主種全体で同定されており、複雑な種間遺伝子流動や環境適応が関与していることを示唆しています。MRSAの世界的な有病率は大きく異なります。例えば、CA-MRSAは日本における分離株の79%を占める一方で、LA-MRSAはマレーシアの乳牛の最大38.6%で検出されています。動物におけるLA-MRSAの定着は、特に農家や獣医師のような密接接触者にとって人獣共通感染症のリスクをもたらします。報告によると、ペットと人間の間で感染が確認されており、統合監視の必要性が浮き彫りになっています。MRSAの病原性は、MSCRAMM、腸毒素、パントン・バレンタイン・ロイコシジン(PVL)などの病原性因子によって駆動されます。バイオフィルムの形成やフェノール可溶性モジュリンは、持続性と免疫回避をさらに促進します。SaPIbovのような病原性島や、 mecC を抱えるSCCmec type XIのような移動性遺伝要素は宿主適応において極めて重要です。さらに、牛に適応した品種で高発現する lukMF' 毒素は、乳牛の乳房炎の重症度を悪化させます。バンコマイシンやダプトマイシンなどの従来の抗生物質は依然として主要な治療法ですが、耐性は増加しています。テディゾリドやデラフロキサシンなどの新規抗菌薬に加え、植物化学物質、プロバイオティクス、ナノ粒子、バクテリオファージなどの非抗生物質療法も有望視されています。特に、グリーン合成の銀ナノ粒子およびラ クトバチルス および ビフィドバクテリウム のプロバイオティクス株は、MRSAに対してin vitroで有意な有効性を示しました

Methicillin-resistant Staphylococcus aureus (MRSA) presents a critical public health threat, arising from its capacity to resist &#946;-lactam antibiotics ...

https://cloudfront.jove.com/files/ftp_upload/40867/40867_article_thumb_40867.jpg

clinical-significance-of-antibiotic-resistance

Education

JoVE Core

Microbiology

微生物学

Unit

ユニット

Antimicrobial Agents

抗微生物剤

KEY TERMS AND CONCEPTS

主要な用語と概念

mrsa: host adaptation and transmission

MRSA, or methicillin-resistant Staphylococcus aureus, is a major public health threat. It resists beta-lactam antibiotics because it carries the mecA gene inside the staphylococcal cassette chromosome mec, or SCCmec. The mecA gene makes penicillin-binding protein 2a, which reduces how well methicillin and related beta-lactam drugs can bind.

MRSA has spread into separate clonal lineages that affect both humans and animals. These lineages fit the One Health idea, which links human, animal, and environmental health. MRSA is often grouped as healthcare-associated MRSA, community-associated MRSA, and livestock-associated MRSA. These groups also show different clonal complexes and host preferences.

One example is CC398. It began in humans, then adapted to livestock, especially pigs, and later spread back from animals to people. Other clonal complexes, including CC1, CC5, CC8, and CC97, have been found across host species. This pattern shows gene flow between species and adaptation to different environments.

MRSA prevalence also differs by region and host. Community-associated MRSA makes up 79% of isolates in Japan. Livestock-associated MRSA has been found in up to 38.6% of dairy cattle in Malaysia. Because LA-MRSA can colonize animals, it can also pose a zoonotic risk to people who work closely with them, such as farmers and veterinarians.

Transmission has also been reported between pets and humans. These findings show why integrated surveillance matters. MRSA pathogenicity is driven by virulence factors such as MSCRAMMs, enterotoxins, and Panton-Valentine leukocidin, or PVL. Biofilm formation and phenol-soluble modulins also help the bacteria persist and avoid immune attack.

Mobile genetic elements are important in host adaptation. SaPIbov and SCCmec type XI, which carries mecC, are examples. In bovine-adapted strains, the lukMF' toxin is strongly expressed and can worsen mastitis in dairy cattle. These features help explain how MRSA survives in different hosts and disease settings.

Treatment still relies on antibiotics such as vancomycin and daptomycin, but resistance is increasing. Newer drugs, including tedizolid and delafloxacin, may offer more options. Non-antibiotic strategies are also being studied, including phytochemicals, probiotics, nanoparticles, and bacteriophages. Green-synthesized silver nanoparticles and probiotic strains of Lactobacillus and Bifidobacterium have shown promising results against MRSA in laboratory studies.

MRSA: Host Adaptation and Transmission

inhibitors of gram-positive cell wall synthesis

inhibitors-of-gram-positive-cell-wall-synthesis

How Antibiotics Block Bacterial Cell Walls

Bacterial cell walls are rigid structures built mainly from peptidoglycan. This mesh-like polymer gives bacteria strength and helps maintain cell shape. Because peptidoglycan synthesis is essential for growth, it is a major target for antibiotics. Beta-lactam antibiotics, such as penicillin, stop peptidoglycan synthesis in actively growing cells. They have a four-membered beta-lactam ring that mimics the D-alanyl-D-alanine dipeptide, which is the natural substrate for transpeptidase, also...

inhibitors of bacterial protein synthesis

inhibitors-of-bacterial-protein-synthesis

Aminoglycosides: How They Stop Bacteria

Aminoglycosides are bactericidal antibiotics that stop bacteria by targeting the ribosome and disrupting protein synthesis. They are highly potent drugs made of amino-modified sugars linked by glycosidic bonds to an aminocyclitol core, such as 2-deoxystreptamine or streptamine. Their strong positive charge helps them bind tightly to the negatively charged phosphate backbone of ribosomal RNA, especially the 16S rRNA of the 30S subunit in the bacterial 70S ribosome. These antibiotics act at the...

inhibitors of bacterial dna synthesis

Fluoroquinolone Antibiotics and Bacterial DNA

Fluoroquinolone antibiotics target bacterial DNA replication by blocking two key type II topoisomerases: DNA gyrase and topoisomerase IV. These enzymes help bacteria manage DNA supercoiling and separate chromosomes during replication. When they are disrupted, bacterial pathogens cannot copy DNA efficiently and infection can spread less effectively. Fluoroquinolones are synthetic versions of quinolones. They work by stabilizing the short-lived DNA-enzyme cleavage complex, which stops strand...

inhibitors of viral protein synthesis

Interferons Block Viral Replication

Interferons block viral replication by shutting down protein synthesis and activating the cell’s antiviral defenses. Viruses need the host cell’s translational machinery to make proteins, because they do not have the machinery to do this on their own. When a virus is detected, infected cells release interferons, which are cytokines, or signaling proteins, that warn nearby uninfected cells. Interferons bind to receptors on nearby cells and activate the JAK-STAT signaling pathway. This turns on...

inhibitors of virion release

Neuraminidase Inhibitors and Flu Spread

Influenza viruses spread when new virions leave an infected cell and reach nearby cells. Influenza A and B are negative-sense, single-stranded RNA viruses with segmented genomes. They depend on two surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA), to infect cells, make new viral particles, and release them. HA starts infection by binding to sialic acid on the surface of host epithelial cells. This binding helps the virus enter the cell by receptor-mediated endocytosis. After...

antiviral nucleoside inhibitors

How Antiviral Drugs Stop Viral Replication

Antiviral nucleoside inhibitors stop viruses by blocking DNA or RNA synthesis. These drugs are structural analogs, which means they look like natural nucleosides, the building blocks cells use to make genetic material. Because they resemble host nucleosides, they can interfere with viral polymerases and disrupt viral genome replication. Acyclovir is a guanosine analog with a three-carbon acyclic side chain. It mainly targets herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2...

antifungal agents

Amphotericin B and Fungal Membranes

Amphotericin B targets fungal cell membranes by binding to ergosterol, a sterol found mainly in fungal plasma membranes. Its amphipathic structure helps this selective binding. It has a hydrophobic polyene-lactone ring and a hydrophilic region with mycosamine and carboxylic acid groups. Weak binding to cholesterol can also affect human cells and helps explain the drug’s toxicity. One way amphotericin B kills fungi is through pore formation. In this model, amphotericin B-ergosterol complexes...

mechanism of antibiotic resistance in mrsa

mechanism-of-antibiotic-resistance-in-mrsa

How Bacteria Outsmart Antibiotics

Antibiotic resistance in bacteria happens when microbes evolve the ability to survive drugs that once killed them or slowed their growth. Genetic change and antibiotic exposure drive this process. Over time, useful treatments can stop working. Bacteria can resist antibiotics in several ways. Some make drug-inactivating enzymes, such as beta-lactamases. Others use efflux pumps to push antibiotics out of the cell. Resistance can also come from mutations that change the drug target, from lower...

anthelminthic agents

Helminth Drugs and How They Work

Helminth drugs work by attacking the weak points of parasitic worms. These anthelmintic medicines are different from drugs used against protozoa, because they are usually aimed at mature helminths rather than fast-dividing cells. They target the worm’s movement, glucose use, and microtubule structure to stop survival, reproduction, and location inside the host. Benzimidazoles are broad-spectrum anthelmintics that block tubulin polymerization, which means they interfere with microtubules, the...

clinical significance of antibiotic resistance

MRSA, or methicillin-resistant Staphylococcus aureus, is a major public health threat. It resists beta-lactam antibiotics because it carries the mecA gene inside the staphylococcal cassette chromosome mec, or SCCmec. The mecA gene makes penicillin-binding protein 2a, which reduces how well methicillin and related beta-lactam drugs can bind. MRSA has spread into separate clonal lineages that affect both humans and animals. These lineages fit the One Health idea, which links human, animal, and...

inhibitors of virion maturation and assembly

inhibitors-of-virion-maturation-and-assembly

HIV Protease Inhibitors and Maturation

HIV protease inhibitors block a key step in virus maturation. In human immunodeficiency virus (HIV), infected cells make two long precursor proteins called polyproteins. These are Gag and Gag-Pol. Gag provides the virus structure. Gag-Pol carries important viral enzymes, including reverse transcriptase, integrase, and protease. After these polyproteins are made, they move to the host cell membrane. There, they help build an immature viral particle that buds from the cell surface. Budding...

antiprotozoal agents

Leishmaniasis and Trypanothione Reductase

Leishmaniasis is a parasitic disease caused by several Leishmania species. It affects millions of people each year and remains a major public health problem in endemic regions. Treatment often relies on pentavalent antimonials, including meglumine antimoniate and sodium stibogluconate. The way these drugs work has not been fully clear. One important target is trypanothione reductase, or TR, an enzyme that helps keep Leishmania in redox balance. TR is not found in mammalian hosts, so it is a...

key terms and concepts

Learn how MRSA spreads between humans and animals, why it resists beta-lactam antibiotics, and what treatments and new control methods are being studied.

MRSA: Host Adaptation and Transmission | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

MRSA: Host Adaptation and Transmission

Description

Transcript

Tags