Longitudinal study of Staphylococcus aureus colonization and infection in a cohort of swine veterinarians in the United States

In this study conducted by Dr. Sun during her PhD under the direction of Dr. Peter Davies, 66 swine veterinarians were sampled via nasal swabs every month for 18 months. Swabs were first cultured to detect Staphylococcus aureus and to determine the strains susceptibility (or resistance) to methicillin, and then were characterized by spa typing and MultiLocus Sequence typing (MLST). Click on the banner below to read the publication in open-access.

Sun longitudinal study Saureus in swine veterinarians 2017

S. aureus monthly prevalence ranged from 58% to 82% and MRSA ranged between 6% and 15%. Those results were higher than the ones for the US population. 52% of the swine veterinarians were classified as persistent carriers, meaning that their samples came back positive for S.aureus at least 80% of the time, 47% were intermittent carriers. 21% of the veterinarians were true persistent carriers meaning that the same spa type of S.aureus was recovered each time the sample was positive.

Staphylococcus aureus positive samples repartition
Number of veterinarians based on the carrier index (number of samples positive for S.aureus divided by number of samples taken per veterinarian)

Whole genome sequencing showed that strains isolated at the beginning and at the end of the study were similar genetically. Comparing spa types, 83% of all isolates belonged to a type also present in swine.

Abstract

BACKGROUND:

People working with pigs are at elevated risk of harboring methicillin resistant S. aureus (MRSA) in their nose, which is attributable to occupational exposure to animals harboring livestock adapted S. aureus. To obtain insight into the biological nature of occupationally related nasal culture positivity, we conducted a longitudinal study of 66 swine veterinarians in the USA.

METHODS:

The study cohort resided in 15 US states and worked predominantly with swine. Monthly for 18 months, participants self-collected nasal swabs and completed a survey to report recent exposure to pigs and other animals; the occurrence of work related injuries; and any relevant health events such as skin and soft tissue infections or confirmed staphylococcal infections. Nasal swabs were cultured using selective methods to determine the presence of MRSA and methicillin susceptible S. aureus (MSSA), and isolates were characterized by spa typing and MLST.

RESULTS:

Prevalences of S. aureus (64%, monthly range from 58 to 82%) and MRSA (9.5%; monthly range from 6 to15%) were higher than reported for the US population (30% and 1.5% respectively). Predominant spa types were t034 (ST398, 37%), t002 (ST5, 17%) and t337 (ST9/ST398 13%), a distribution similar to that found in a concurrent study in pigs in the USA. Veterinarians were classified into three groups: Persistent carriers (PC, 52%), Intermittent carriers (IC, 47%) and Non-carriers (NC, 1%). Persistent carriage of a single spa type was observed in 14 (21%) of participants, and paired (first and last) isolates from PC subjects had minor genetic differences. Swabs from PC veterinarians carried higher numbers of S. aureus. Among IC veterinarians, culture positivity was significantly associated with recent contact with pigs.

CONCLUSIONS:

Exposure to pigs did not lead to prolonged colonization in most subjects, and the higher numbers of S. aureus in PC subjects suggests that unknown host factors may determine the likelihood of prolonged colonization by S. aureus of livestock origin. Exposure to S. aureus and persistent colonization of swine veterinarians was common but rarely associated with S. aureus disease.

Dr. Morrison’s wife, Jeanie no longer in life threatening condition

We are trying to give you a daily update on the situation regarding the auto accident that happened in Prague on Tuesday and lead to Dr. Morrison’s passing.

As of today, Jeanie Morrison, Dr. Morrison’s wife, is no longer in a life-threatening condition said the doctors in charge of her recovery. We do not have any further information but the Morrison family is in the process of creating a online information page to provide updates on Jeanie’s situation. We will add the link here when it is available.

Thank you everyone for your support.

Edit: The Caring Bridge web page is here.

Mycoplasma hyorhinis prevalence varies based on pigs’ age

Summary

  • Mycoplasma hyorhinis can cause polyserositis and arthritis in post-weaning pigs.
  • To study M.hyorhinis‘ prevalence based on age, nasal swabs were taken from pigs at 1, 7, 14, 21, 28, 35, 42, 49, 56, 63, 70 and 77 days as well as from sows, in 3 different Minnesotan herds (A, B, and C).
  • 8.8% of the sows were positive for M.hyorhinis in herds A and B whereas 3.3% of the sows were positive in herd C.
  • The percentage of positive piglets (<21 days of age) was low: between 0 and 10% depending on the herds.
  • At 28 days of age, the prevalence of M.hyorhinis in pigs increased dramatically to around 50% in herd A and 100% in herd B. After 42 days of age, the prevalence in those herds stayed above 95%.
  • The prevalence in herd C stayed close to 0% until the pigs reached the age of 77 days, time at which the prevalence increased to 100%.

Did you see our Science page on Mycoplasma hyorhinis and swine conjunctivitis?

Mhyorhinis prevalence baed on age Rovira 2017

Abstract

Mycoplasma hyorhinis is one of the causative agents of polyserositis and arthritis in postweaning pigs. Knowledge regarding colonization frequency and age distribution in modern pig production is lacking. The objective of this study was to estimate the prevalence of M hyorhinis colonization in different age groups across three commercial pig populations. Nasal swabs were collected from sows, piglets and nursery pigs of different ages. Oral fluids were collected from nursery pigs. Necropsies were performed to assess the presence of M hyorhinis-associated disease. M hyorhinis was detected in 5/60 sows in herd A, 3/60 in herd B and none in herd C. In herd A and B, the prevalence was low in preweaning piglets (∼8 per cent) and high in postweaning pigs (∼98 per cent). A total of 7/8 oral fluids tested PCR positive in herds A and B, while 1/8 tested positive in herd C. In herd C, the preweaning and postweaning prevalence was low. In herds A and B, necropsied pigs had polyserositis lesions where M hyorhinis was detected by PCR. This study showed that prevalence of M hyorhinis colonization varies with pig age and across farms. Information generated will aid in the design and implementation of control and prevention strategies.

Link to the full paper

Sample and diagnostic types for early detection of Mycoplasma hyopneumoniae

Summary:

Mycoplasma hyopneumoniae is the causative agent enzootic pneumonia, an economically significant disease in pigs. In this study published by Drs. Pieters and Rovira from the University of Minnesota, pigs experimentally inoculated with M.hyopneumoniae were sampled 0, 2, 5, 9, 14, 21, and 28 post-inoculation.

Different sample types were compared:

  • Nasal swabs
  • Laryngeal swabs
  • Tracheobronchal lavages
  • Oral fluids
  • Serum samples

Using different diagnostic tests:

  • PCR
  • ELISA IgG anti M.hyopneumoniae
  • ELISA Ig M anti M.hyopneumoniae
  • ELISA C-reactive protein

Laryngeal swab samples tested by PCR were highly sensitive for detection of Mycoplasma hyopneumoniae in live pigs.
Various commercial ELISA kits for detection of Mycoplasma hyopneumoniae antibodies showed similar sensitivity.
Oral fluids showed a low sensitivity for detection of Mycoplasma hyopneumoniae in experimentally infected pigs.

Pieters Mhyopneumoniae early detection test sample 2017

Abstract

Detection of Mycoplasma hyopneumoniae in live pigs during the early stages of infection is critical for timely implementation of control measures, but is technically challenging. This study compared the sensitivity of various sample types and diagnostic methods for detection of M. hyopneumoniae during the first 28 days after experimental exposure. Twenty-one 8-week old pigs were intra-tracheally inoculated on day 0 with M. hyopneumoniae strain 232. Two age matched pigs were mock inoculated and maintained as negative controls. On post-inoculation days 0, 2, 5, 9, 14, 21 and 28, nasal swabs, laryngeal swabs, tracheobronchial lavage fluid, and blood samples were obtained from each pig and oral fluid samples were obtained from each room in which pigs were housed. Serum samples were assayed by ELISA for IgM and IgG M. hyopneumoniae antibodies and C-reactive protein. All other samples were tested for M. hyopneumoniae DNA by species-specific real-time PCR. Serum antibodies (IgG) to M. hyopneumoniae were detected in challenge-inoculated pigs on days 21 and 28. M. hyopneumoniae DNA was detected in samples from experimentally inoculated pigs beginning at 5 days post-inoculation. Laryngeal swabs at all samplings beginning on day 5 showed the highest sensitivity for M. hyopneumoniae DNA Detection, while oral fluids showed the lowest sensitivity. Although laryngeal swabs are not considered the typical M. hyopneumoniae diagnostic sample, under the conditions of this study laryngeal swabs tested by PCR proved to be a practical and reliable diagnostic sample for M. hyopneumoniae detection in vivo during early-stage infection.

Link to the full-article

Air samples successful in detecting on-farm PRRSV, PEDV, and high-path avian influenza virus

NEW: Read the Swine Health Monitoring Project – Science Page here, every Friday

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The Swine Health Monitoring Project (SHMP) is a National program coordinated by Dr. Bob Morrison from the University of Minnesota, College of Veterinary Medicine. The goal of this initiative is to monitor the incidence and prevalence of relevant swine diseases in the US such as Porcine reproductive and respiratory syndrome (PRRS) or Porcine Epidemic Diarrhea (PED) for example. Participants are voluntarily sharing the health status of their farms in order to better understand, and in the future, control these illnesses. Each week participants receive a report including a one-page summary of a scientific fact of interest. From now on, the Science Page will be published on the blog here, every Friday.

This week’s edition

All of the previous Science Pages are compiled here.
If you want to know more about the Swine Health Monitoring Project, an article from the National Hog Farmer and one  from the Swine Health Information Center will give you an overview of the program and its goals.

 

Gary Louis, PhD confirmed as keynote speaker at the 2017 Allen D. Leman swine conference

The Allen D. Leman swine conference is only six months away! Our team is preparing an  exciting conference program for you this year and we will update you regularly on the speakers and topics that will be covered during this great event bringing science-driven solutions to the complex challenges facing the swine industry. We already shared with you that the recipient of this year’s Science in Practice award is Dr. Bob Thompson.

We are glad to announce that our first key note speaker for the conference will be Gary Louis, Executive Vice President of Seaboard Foods LLC where he is in charge of the live operations. We are delighted that he has accepted our invitation to share his tremendous experience and his vision of the swine production.

More information about the Allen D. Leman swine conference can be found here.