Related Experiment Video
Updated: Apr 15, 2026
Genotyping of Staphylococcus aureus by Ribosomal Spacer PCR RS-PCR
Published on: November 4, 2016
What Is the Origin of Livestock-Associated Methicillin-Resistant Staphylococcus aureus Clonal Complex 398 Isolates
W S N Lekkerkerk1, W J B van Wamel2, S V Snijders2
1Department of Medical Microbiology and Infectious Diseases, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands RIVM, National Institute for Public Health and the Environment, Bilthoven, The Netherlands w.lekkerkerk@erasmusmc.nl.
Abstract:
Fifteen percent of all methicillin-resistant Staphylococcus aureus (MRSA) clonal complex 398 (CC398) human carriers detected in The Netherlands had not been in direct contact with pigs or veal calves. To ensure low MRSA prevalence, it is important to investigate the likely origin of this MRSA of unknown origin (MUO). Recently, it was shown that CC398 strains originating from humans and animals differ in the presence of specific mobile genetic elements (MGEs). We hypothesized that determining these specific MGEs in MUO isolates and comparing them with a set of CC398 isolates of various known origin might provide clues to their origin. MUO CC398 isolates were compared to MRSA CC398 isolates obtained from humans with known risk factors, a MRSA CC398 outbreak isolate, livestock associated (LA) MRSA CC398 isolates from pigs, horses, chickens, and veal calves, and five methicillin-susceptible Staphylococcus aureus (MSSA) CC398 isolates of known human origin. All strains were spa typed, and the presence or absence of, scn, chp, φ3 int, φ6 int, φ7 int, rep7, rep27, and cadDX was determined by PCRs. The MRSA CC398 in humans, MUO, or MRSA of known origin (MKO) resembled MRSA CC398 as found in pigs and not MSSA CC398 as found in humans. The distinct human MSSA CC398 spa type, t571, was not present among our MRSA CC398 strains; MRSA CC398 was tetracycline resistant and carried no φ3 bacteriophage with scn and chp. We showed by simple PCR means that human MUO CC398 carriers carried MRSA from livestock origin, suggestive of indirect transmission. Although the exact transmission route remains unknown, direct human-to-human transmission remains a possibility as well.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) clonal complex 398 (CC398) in human carriers with unknown origins likely stems from livestock, suggesting indirect transmission. Further investigation into mobile genetic elements confirmed this livestock origin, though direct human transmission remains possible.
Area of Science:
- Veterinary Microbiology
- Infectious Diseases
- Genetics
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) clonal complex 398 (CC398) is increasingly found in humans.
- A significant proportion of human CC398 carriers lack direct livestock contact, necessitating origin investigation.
- Specific mobile genetic elements (MGEs) differentiate animal- and human-origin CC398 strains.
Purpose of the Study:
- To determine the origin of MRSA CC398 in human carriers with no known livestock contact (MRSA of unknown origin - MUO).
- To compare MGE profiles of MUO CC398 isolates with those from known human and animal sources.
- To assess the potential for indirect transmission of livestock-associated MRSA CC398 to humans.
Main Methods:
- Spa typing and PCR analysis for specific MGEs (scn, chp, φ3 int, φ6 int, φ7 int, rep7, rep27, cadDX) were performed on MRSA CC398 isolates from humans (MUO and known origin), livestock, and a human outbreak.
- Comparison of MGE profiles between MUO CC398 and reference CC398 strains from various sources.
- Analysis of antimicrobial resistance patterns, specifically tetracycline resistance.
Main Results:
- MRSA CC398 isolates from humans (MUO and known origin) shared genetic similarities with pig-origin MRSA CC398, distinct from human-origin methicillin-susceptible Staphylococcus aureus (MSSA) CC398.
- The specific human MSSA CC398 spa type (t571) was absent in all MRSA CC398 strains.
- MUO CC398 isolates consistently carried MGEs characteristic of livestock-associated MRSA CC398 and exhibited tetracycline resistance.
Conclusions:
- Human MUO CC398 carriers harbor MRSA CC398 strains of likely livestock origin.
- Indirect transmission is suggested as the primary route for CC398 acquisition in humans without direct contact.
- While indirect transmission is indicated, direct human-to-human transmission cannot be entirely excluded.
More Related Videos
09:03Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus
Published on: September 5, 2013
08:03Heuristic Mining of Hierarchical Genotypes and Accessory Genome Loci in Bacterial Populations
Published on: December 7, 2021
Related Concept Videos
01:25Clinical Significance of Antibiotic Resistance
01:29Staphylococcal Skin Infections
01:25Mechanism of Antibiotic Resistance in MRSA
01:26Healthcare Associated Infections I: Iatrogenic, Exogenic and Endogenic
HAIs significantly increase the cost of health care. Extended stays in healthcare institutions, increased disability, increased costs of medications, including specialized antibiotics, and prolonged recovery times add to the patient's expenses and the healthcare institution and funding bodies.