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

La resistenza agli antibiotici è la capacità di un microrganismo di resistere agli effetti degli antibiotici.Un patogeno comunemente noto, Staphylococcus aureus, ha sviluppato resistenza alla meticillina, dando origine a Staphylococcus aureus resistente alla meticilina, o MRSA.La MRSA causa gravi infezioni cutanee e dei tessuti molli negli esseri umani, portando a milioni di ricoveri e decessi in tutto il mondo ogni anno.Gli anziani e i pazienti immunodepressi sono i più a rischio a causa dell'uso prolungato ed esteso di antibiotici ad ampio spettro.Le strategie per combattere l'MRSA includono l'uso di fitochimici, terapia con fagi, nanoparticelle e probiotici.I fitochimici — metaboliti secondari estratti dalle piante — sono ampiamente utilizzati per inibire la crescita del MRSA.I fagi specifici per MRSA possono ridurre le popolazioni di MRSA inducendo la lisi cellulare.Le nanoparticelle esercitano stress rilasciando ioni metallici pesanti nelle cellule. Altera la permeabilità della membrana e interrompe funzioni cellulari essenziali.Infine, alcuni ceppi probiotici secernono composti antimicrobici che inibiscono la crescita dell'MRSA.

significato clinico della resistenza agli antibiotici

Clinical Significance of Antibiotic Resistance

Lo Staphylococcus aureus resistente alla meticillina (MRSA) rappresenta una minaccia critica per la salute pubblica, derivante dalla sua capacità di resistere agli antibiotici β-lattamici grazie all'acquisizione del gene mecA all'interno del cromosoma a cassetta stafilococica mec (SCCmec). Questo gene codifica per la proteina di legame della penicillina 2a (PBP2a), che compromette l'efficacia di legame della meticillina e di altri β-lattamici. L'MRSA si è evoluto in linee clonali distinte che influenzano sia gli esseri umani che gli animali, rafforzandone l'importanza all'interno del paradigma One Health.I ceppi di MRSA sono classificati in associati all'assistenza sanitaria (HA-MRSA), associati alla comunità (CA-MRSA) e associati al bestiame (LA-MRSA). Queste linee mostrano variazione del complesso clonale (CC) e specificità dell'ospite. Ad esempio, il CC398—inizialmente di origine umana—ha subito un adattamento nel bestiame, in particolare nei maiali, portando alla sua trasmissione zoonotica inversa. Sono stati identificati molteplici CC come CC1, CC5, CC8 e CC97 tra le specie ospiti, implicando un flusso genico interspecie complesso e un adattamento ambientale.La prevalenza globale della MRSA varia ampiamente. Ad esempio, il CA-MRSA rappresenta il 79% degli isolati in Giappone, mentre il LA-MRSA è stato rilevato in fino al 38,6% dei bovini da latte malesi. La colonizzazione LA-MRSA negli animali rappresenta un rischio zoonotico, specialmente per chi è in stretto contatto, come agricoltori e veterinari. I rapporti hanno confermato eventi di trasmissione tra animali domestici e esseri umani, sottolineando la necessità di una sorveglianza integrata.La patogenicità della MRSA è guidata da una serie di fattori di virulenza, tra cui MSCRAMM, enterotossine e leucocidina di Panton-Valentine (PVL). La formazione di biofilm e le moduline fenosolubili aumentano ulteriormente la persistenza e l'evasione immunitaria. Isole patogeniche come SaPIbov e elementi genetici mobili come SCCmec di tipo XI che ospitano mecC sono fondamentali per l'adattamento dell'ospite. Inoltre, la tossina lukMF' , fortemente espressa in ceppi adattati ai bovini, aggrava la gravità della mastite nei bovini da latte.Gli antibiotici tradizionali, tra cui vancomicina e daptomicina, rimangono trattamenti chiave, anche se la resistenza sta aumentando. Nuovi antimicrobici come tedizolid e delaflossicina, insieme ad approcci non antibiotici — fitochimici, probiotici, nanoparticelle e batteriofagi — mostrano potenzialità. In particolare, nanoparticelle d'argento sintetizzate dal verde e ceppi probiotici di Lactobacillus e Bifidobacterium hanno dimostrato una significativa efficacia in vitro contro MRSA

Significato clinico della resistenza agli antibiotici

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

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clinical-significance-of-antibiotic-resistance

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Microbiology

Microbiologia

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Antimicrobial Agents

Agenti antimicrobici

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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

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

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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...

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inhibitors-of-virion-maturation-and-assembly

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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

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