Abstract
Pigs, cattle and poultry are colonized with MRSA and the zoonotic transmission of such MRSA to humans via direct animal contact, environmental contaminations or meat are a matter of concern. Livestock-associated (LA) MRSA are mostly belonging to clonal complex (CC) 398 as defined by multilocus sequence typing. However, MRSA of other clonal lineages including CC5, CC9 and CC97 have also been detected in livestock animals in Germany. Within the framework of a Dutch-German network project (EUREGIO), 14,036 MRSA isolated from clinical and screening specimens (January 2008 – June 2012) derived from human patients in hospitals as well as general or specialized practices in a German region characterized by a high density of livestock production, were subjected to S. aureus protein A (spa) sequence typing. The prevalence of putative LA-MRSA among the human MRSA isolates was determined by analyzing the detection of livestock-indicator (LI) spa types which had already been reported in German livestock. Overall, 578 spa types were detected among the MRSA isolates. LI spa types t011, t034, t108, t1451, t2011, t571, t1456, t1250, t1255, t1580, t2970, t2346, t1344, t2576, t2330 and t2510 (all of which are indicative for LA-MRSA CC398) accounted for 18.6% of all human isolates. The LI spa types t1430 (CC9), 13992 (CC97), t002 (CC5) and t007 (CC30) were found in 0.14%, 0.01%, 1.01% and 0.04% of all human MRSA isolates, respectively. LI spa types associated with CC398 represented 23% of all MRSA from screening samples and a varying proportion among isolates from clinical specimens ranging between 0% in cerebrospinal fluid, 8% in blood cultures and 14% in deep respiratory fluids. Our findings indicate that LA-MRSA are a major cause for human infection and stress the need for close surveillance. Although LA-MRSA CC398 predominates, the occurrence of putative LA-MRSA from other clonal lineages should be monitored.
Generated Summary
This research, published in PLOS ONE, investigates the prevalence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) as a cause of human infection and colonization in Germany. The study utilized a Dutch-German network project (EUREGIO) to analyze 14,036 MRSA isolates from clinical and screening specimens collected between January 2008 and June 2012. The primary methodology involved spa sequence typing to identify livestock-indicator (LI) spa types, which are indicative of LA-MRSA. The research aimed to determine the prevalence of LA-MRSA among human MRSA isolates, considering the high density of livestock production in the study region. The study also examined the distribution of LA-MRSA in different clinical and screening specimens to assess the risk of human infection and colonization. The findings emphasize the need for close surveillance of LA-MRSA, particularly CC398, and other clonal lineages.
Key Findings & Statistics
- Prevalence of LA-MRSA: 18.6% of all human isolates were identified as putative LA-MRSA based on the detection of livestock-indicator (LI) spa types.
- LI spa types associated with CC398: These accounted for 23% of all MRSA from screening samples.
- LI spa types associated with CC9, CC97, CC5, and CC30: These were found in 0.14%, 0.01%, 1.01%, and 0.04% of all human MRSA isolates, respectively.
- Distribution in Clinical Specimens: The proportion of LI spa types varied across clinical specimens, ranging from 0% in cerebrospinal fluid, 8% in blood cultures, and 14% in deep respiratory fluids.
- Number of MRSA Isolates: The network database contained spa typing results of 14,036 human MRSA isolates.
- Origin of Isolates: 81% (11,336) of the isolates were from hospitalized patients, and 19% (2,700) were from outpatients.
- Number of spa types: 578 spa types were detected among the MRSA isolates.
- Dominant spa types: t003 (29%), t032 (25%), and t011 (10%) were the most frequently detected spa types.
- LA-MRSA in Screening Samples: The proportion of MRSA CC398 in screening samples increased from 2008 to 2012 (p<0.001).
- LA-MRSA in Superficial Wounds: The proportion of MRSA CC398 in superficial wounds increased from 2008 to 2012 (p=0.04).
- MRSA in Blood Cultures: 8% of blood cultures showed MRSA CC398.
- MRSA in Deep Respiratory Secretions: 14% of deep respiratory secretions showed MRSA CC398.
- Contamination of Meat: Chicken and pig meat at retail was contaminated with MRSA in 42% and 16% of the samples, respectively.
Other Important Findings
- LA-MRSA, particularly those belonging to clonal complex (CC) 398, is a significant cause of human infection and colonization in Germany.
- The study highlights the need for continuous surveillance of LA-MRSA and other clonal lineages.
- LA-MRSA CC398 predominates, but the presence of LA-MRSA from other clonal lineages should be monitored.
- The study indicates that LA-MRSA can cause severe human infections in hospitals.
- The increase in LA-MRSA prevalence may be due to increased awareness or greater introduction of such isolates into hospitals.
- MRSA CC398 is able to cause severe human infections in hospitals.
- The study found a significant trend towards an increasing proportion of MRSA CC398 among specimens from screenings and superficial wounds between 2008 and 2012.
- Several spa types detected among the human MRSA isolates showed a spa repeat pattern closely related to known LI spa types.
- The study observed a significant trend towards an increasing proportion of MRSA CC398 among specimens from screenings (X² = 155.5; p<0.001) and superficial wounds (X² = 4.4; p = 0.04) between 2008 and 2012.
Limitations Noted in the Document
- The study acknowledges that it cannot provide comprehensive epidemiological data regarding risk factors for LA-MRSA carriage or the overall incidence of MRSA due to the limitations of the central network database, which contains anonymized datasets.
- Not all regional hospitals type every first MRSA isolate, preventing a full estimate of LA-MRSA’s impact.
- The study cannot determine the extent to which LA-MRSA has replaced classical healthcare-associated MRSA or added to the overall MRSA burden.
- The study is limited in its ability to fully assess the transmission dynamics of LA-MRSA, including the relative importance of livestock contact versus human-to-human spread.
- The study does not include data on risk factors associated with LA-MRSA carriage or overall MRSA incidence.
Conclusion
The study’s findings underscore the substantial role of LA-MRSA, particularly CC398, in human infections within Germany, emphasizing the need for comprehensive surveillance to monitor its spread. The detection of LA-MRSA in a variety of clinical specimens, including blood cultures and respiratory secretions, highlights its capacity to cause severe infections, thereby underscoring its clinical importance. The observed trend towards increasing LA-MRSA prevalence in screening and wound samples between 2008 and 2012 suggests a potential increase in prevalence. The fact that LA-MRSA CC398 accounts for a significant proportion of MRSA cases, along with the identification of other livestock-associated lineages, suggests the need for a broader approach to surveillance and control measures. Furthermore, the data indicates LA-MRSA may be spreading from human to human, not only through direct livestock exposure. The study’s conclusions stress the significance of ongoing surveillance efforts. The authors advocate for monitoring not only the predominant CC398 but also other clonal lineages that might be associated with livestock. This comprehensive approach is crucial for understanding and mitigating the impact of LA-MRSA on public health. The authors suggest further investigation to fully understand the transmission dynamics of LA-MRSA, including both zoonotic and human-to-human spread, as well as the role of meat contamination in the spread of the disease.