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Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus
Published on: September 5, 2013
Epidemic MRSA clone ST22-IV is more resistant to multiple host- and environment-related stresses compared with
Rossella Baldan1, Paola Maria Vittoria Rancoita2, Clelia Di Serio2
1Emerging Bacterial Pathogens Unit, Division of Immunology, Transplantation and Infectious Diseases, IRCCS San Raffaele Scientific Institute, Milan, Italy.
Background:
ST22-IV is a successful hospital-associated MRSA clone. Due to its known ability to replace other MRSA clones in hospitals, it became a dominant clone in Europe and beyond. So far, there are no studies investigating the relationship between the epidemiological success of MRSA clones and their capacity to withstand commonly encountered stresses.
Methods:
We investigated the fitness of ST22-IV in comparison with the replaced clone ST228-I, evaluating its resistance to oxidative stress, autolytic activity, growth at high osmolarity and in acid and alkaline environments and survival under desiccation and heat shock. We also compared their phenotypic characteristics and examined the impact of antibiotic consumption on epidemiological success.
Results:
Here we demonstrate that the dominance of ST22-IV is linked neither to changes in antibiotic consumption nor to acquisition of additional resistances over time. Strong α-haemolysin activity, the production of β-haemolysin and the presence of an active agr could partly explain the virulence of ST22-IV previously observed in a murine model of pneumonia. Most importantly, we show that ST22-IV compared with ST228-I, besides retaining susceptibility to most antibiotics over time, has a superior capacity to survive under all stress conditions tested, which bacteria commonly face during their life cycle.
Conclusions:
Our results support our hypothesis that ST22-IV has a fitness advantage over ST228-I. This fitness advantage could have allowed ST22-IV to displace ST228-I without acquiring additional resistances and could help explain its epidemic success in hospital settings and its spread in Europe and beyond.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) clone ST22-IV dominates hospitals due to superior stress resistance, not antibiotic resistance. This fitness advantage explains its epidemiological success and spread.
Area of Science:
- Microbiology
- Epidemiology
- Infectious Diseases
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) clone ST22-IV is a dominant hospital-associated pathogen in Europe.
- ST22-IV has demonstrated the ability to replace other MRSA clones within healthcare settings.
- The relationship between MRSA clone success and environmental stress resistance remains understudied.
Purpose of the Study:
- To investigate the fitness of MRSA clone ST22-IV compared to the replaced clone ST228-I.
- To evaluate ST22-IV's resistance to various environmental and host-associated stresses.
- To determine if enhanced stress survival contributes to the epidemiological success of ST22-IV.
Main Methods:
- Comparative analysis of ST22-IV and ST228-I fitness.
- Assessment of resistance to oxidative stress, high osmolarity, acidic/alkaline environments, desiccation, and heat shock.
- Evaluation of autolytic activity, phenotypic characteristics, and the impact of antibiotic consumption.
Main Results:
- ST22-IV dominance is not linked to increased antibiotic consumption or acquired resistances.
- Virulence factors like α-haemolysin, β-haemolysin, and an active agr contribute to ST22-IV's pathogenicity.
- ST22-IV exhibits significantly superior survival under all tested stress conditions compared to ST228-I.
Conclusions:
- ST22-IV possesses a fitness advantage over ST228-I, facilitating its displacement.
- This enhanced stress survival, rather than additional antibiotic resistance, explains ST22-IV's epidemic success.
- The findings highlight the importance of environmental resilience in the spread of successful MRSA clones.
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