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Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
Published on: February 9, 2011
Methicillin-resistant Staphylococcus aureus ST398 contamination and transmission in pigs after a low dose inoculation
E Jouy1, A Le Roux, A Kéranflec'h
1Anses, Ploufragan-Plouzané Laboratory, Ploufragan, France. eric.jouy@anses.fr
Aims:
Methicillin-resistant Staphylococcus aureus (MRSA) ST398 has recently been described as a zoonotic agent. Its transmission between animals seems to be a pivotal factor in its emergence and dissemination. This experimental trial was performed to describe MRSA ST398 contamination and transmission in pigs after a low dose inoculation.
Methods And Results:
Twelve specific pathogen-free (SPF) pigs were randomly divided between two separate pens. Three pigs in each pen received a nasal inoculation of 2 × 10(4) colony-forming units per animal, and three naïve pigs were left in contact with them. Every 2 days and at necropsy, different samples were screened for MRSA. It was detected in nasal swabs from five inoculated and three naïve contact pigs, as early as 1 day after inoculation. MRSA was also found in environmental wipes but never in faecal samples. At necropsy, MRSA was detected in the lymph nodes of two contact pigs and in the tonsils and lymph nodes of three inoculated pigs. Twelve other SPF pigs were included as negative control in a separate room.
Conclusion:
This experiment showed that inoculation of a low dose of MRSA ST398 could lead to the horizontal transmission of the bacterium between pigs, the contamination of mandibular lymph nodes and the contamination of the environment without faecal carriage.
Significance And Impact Of The Study:
The minimal inoculated dose via nasal route to observe transmission of MRSA ST398 between pigs is equal or lower to 2 × 10(4) colony-forming units per animal, and faecal excretion seems not to be a necessary condition for horizontal transmission.
Insights
A low dose of Methicillin-resistant Staphylococcus aureus (MRSA) ST398 transmitted between pigs through nasal inoculation, contaminating lymph nodes and the environment. Faecal carriage was not necessary for this horizontal spread.
Area of Science:
- Veterinary Microbiology
- Zoonotic Diseases
- Bacterial Pathogenesis
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) ST398 is an emerging zoonotic agent.
- Animal-to-animal transmission is critical for MRSA ST398 emergence and spread.
- Understanding transmission dynamics in livestock is crucial for control.
Purpose of the Study:
- To investigate MRSA ST398 contamination and transmission in pigs following low-dose nasal inoculation.
- To determine the minimal infectious dose for MRSA ST398 transmission between pigs.
- To assess the role of environmental and faecal contamination in MRSA ST398 spread.
Main Methods:
- Experimental trial with specific pathogen-free (SPF) pigs.
- Nasal inoculation of pigs with a low dose (2 × 10(4) CFU) of MRSA ST398.
- Monitoring of inoculated and naïve contact pigs via nasal swabs and environmental samples.
- Necropsy to assess MRSA presence in tissues and lymph nodes.
Main Results:
- MRSA ST398 was detected in nasal swabs of inoculated and contact pigs within 1 day post-inoculation.
- The bacterium was found in environmental wipes but not in fecal samples.
- MRSA ST398 was present in tonsils and lymph nodes of inoculated pigs and lymph nodes of contact pigs.
Conclusions:
- Low-dose nasal inoculation of MRSA ST398 facilitates horizontal transmission between pigs.
- Environmental contamination occurs without the need for faecal carriage.
- The minimal dose for transmission is ≤ 2 × 10(4) CFU, highlighting efficient nasal route spread.
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