Low-level colonization of methicillin-resistant Staphylococcus aureus in pigs is maintained by slowly evolving, closely related strains in Finnish pig farms

Abstract Background Over the past two decades, livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) has become widely prevalent in pig production in Europe. The carriage status of LA-MRSA is known to vary among individual pigs, but bacterial load in pigs has rarely been studied...

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Main Authors: Marie Verkola, Milla Takala, Suvi Nykäsenoja, Satu Olkkola, Paula Kurittu, Saija Kiljunen, Henni Tuomala, Asko Järvinen, Annamari Heikinheimo
Format: Article
Language:English
Published: BMC 2022-12-01
Series:Acta Veterinaria Scandinavica
Subjects:
Online Access:https://doi.org/10.1186/s13028-022-00653-y
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author Marie Verkola
Milla Takala
Suvi Nykäsenoja
Satu Olkkola
Paula Kurittu
Saija Kiljunen
Henni Tuomala
Asko Järvinen
Annamari Heikinheimo
author_facet Marie Verkola
Milla Takala
Suvi Nykäsenoja
Satu Olkkola
Paula Kurittu
Saija Kiljunen
Henni Tuomala
Asko Järvinen
Annamari Heikinheimo
author_sort Marie Verkola
collection DOAJ
description Abstract Background Over the past two decades, livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) has become widely prevalent in pig production in Europe. The carriage status of LA-MRSA is known to vary among individual pigs, but bacterial load in pigs has rarely been studied. We assessed the quantity of LA-MRSA in nasal and skin samples of pigs and investigated the genetic diversity of the strains together with sequenced strains from national surveillance and pathology samples from the Finnish Food Authority. On two farms with assumed MRSA-positive status, farm 1 and farm 2, 10 healthy pigs were sampled three times during 2 weeks from the nares and skin (study A). On farm 1, 54 additional pigs were sampled and from confirmed MRSA-positive animals, 10 were randomly selected and transported to a clean, controlled environment for further sampling (study B). From the samples taken on farms 1 and 2 and in the controlled environment, MRSA was isolated both by direct plating and enrichment on selective media. spa types, multilocus sequence types, staphylococcal cassette chromosome mec types, resistance and virulence genes were determined. Core genome multilocus sequence typing (cgMLST) analysis was performed, including the sequences deriving from the surveillance/pathology samples from the Finnish Food Authority. Results All pigs on farm 1 carried LA-MRSA in the nares at all three time points and five pigs on farm 2 at one time point. Nasal quantity varied between 10 and 103 CFU/swab and quantity on the skin between 10 and 102 CFU/swab. In the controlled environment, MRSA was detected in at least one of the nasal samples from each animal. spa type t034 was predominant. cgMLST showed one cluster with minimum allele differences between 0 and 11. Conclusions The study shows predominantly low-level carriage (< 103 CFU/swab) of LA-MRSA on farms. In the controlled environment we observed a decline in nasal carriage but constant skin carriage. cgMLST showed that strains of spa type t034 are closely related at the national level.
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spelling doaj.art-e40b54ae757c4af3bf11bf39a74e57b22022-12-22T02:48:39ZengBMCActa Veterinaria Scandinavica1751-01472022-12-0164111610.1186/s13028-022-00653-yLow-level colonization of methicillin-resistant Staphylococcus aureus in pigs is maintained by slowly evolving, closely related strains in Finnish pig farmsMarie Verkola0Milla Takala1Suvi Nykäsenoja2Satu Olkkola3Paula Kurittu4Saija Kiljunen5Henni Tuomala6Asko Järvinen7Annamari Heikinheimo8Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of HelsinkiDepartment of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of HelsinkiLaboratory and Research Division, Microbiology Unit, Finnish Food AuthorityLaboratory and Research Division, Microbiology Unit, Finnish Food AuthorityDepartment of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of HelsinkiHuman Microbiome Research Program, Faculty of Medicine, Helsinki University Central Hospital, University of HelsinkiHuman Microbiome Research Program, Faculty of Medicine, Helsinki University Central Hospital, University of HelsinkiDepartment of Infectious Diseases, Inflammation Center, Helsinki University Central Hospital, University of HelsinkiDepartment of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of HelsinkiAbstract Background Over the past two decades, livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) has become widely prevalent in pig production in Europe. The carriage status of LA-MRSA is known to vary among individual pigs, but bacterial load in pigs has rarely been studied. We assessed the quantity of LA-MRSA in nasal and skin samples of pigs and investigated the genetic diversity of the strains together with sequenced strains from national surveillance and pathology samples from the Finnish Food Authority. On two farms with assumed MRSA-positive status, farm 1 and farm 2, 10 healthy pigs were sampled three times during 2 weeks from the nares and skin (study A). On farm 1, 54 additional pigs were sampled and from confirmed MRSA-positive animals, 10 were randomly selected and transported to a clean, controlled environment for further sampling (study B). From the samples taken on farms 1 and 2 and in the controlled environment, MRSA was isolated both by direct plating and enrichment on selective media. spa types, multilocus sequence types, staphylococcal cassette chromosome mec types, resistance and virulence genes were determined. Core genome multilocus sequence typing (cgMLST) analysis was performed, including the sequences deriving from the surveillance/pathology samples from the Finnish Food Authority. Results All pigs on farm 1 carried LA-MRSA in the nares at all three time points and five pigs on farm 2 at one time point. Nasal quantity varied between 10 and 103 CFU/swab and quantity on the skin between 10 and 102 CFU/swab. In the controlled environment, MRSA was detected in at least one of the nasal samples from each animal. spa type t034 was predominant. cgMLST showed one cluster with minimum allele differences between 0 and 11. Conclusions The study shows predominantly low-level carriage (< 103 CFU/swab) of LA-MRSA on farms. In the controlled environment we observed a decline in nasal carriage but constant skin carriage. cgMLST showed that strains of spa type t034 are closely related at the national level.https://doi.org/10.1186/s13028-022-00653-yAntimicrobial resistancecgMLSTLA-MRSALivestock-associated methicillin-resistant Staphylococcus aureus
spellingShingle Marie Verkola
Milla Takala
Suvi Nykäsenoja
Satu Olkkola
Paula Kurittu
Saija Kiljunen
Henni Tuomala
Asko Järvinen
Annamari Heikinheimo
Low-level colonization of methicillin-resistant Staphylococcus aureus in pigs is maintained by slowly evolving, closely related strains in Finnish pig farms
Acta Veterinaria Scandinavica
Antimicrobial resistance
cgMLST
LA-MRSA
Livestock-associated methicillin-resistant Staphylococcus aureus
title Low-level colonization of methicillin-resistant Staphylococcus aureus in pigs is maintained by slowly evolving, closely related strains in Finnish pig farms
title_full Low-level colonization of methicillin-resistant Staphylococcus aureus in pigs is maintained by slowly evolving, closely related strains in Finnish pig farms
title_fullStr Low-level colonization of methicillin-resistant Staphylococcus aureus in pigs is maintained by slowly evolving, closely related strains in Finnish pig farms
title_full_unstemmed Low-level colonization of methicillin-resistant Staphylococcus aureus in pigs is maintained by slowly evolving, closely related strains in Finnish pig farms
title_short Low-level colonization of methicillin-resistant Staphylococcus aureus in pigs is maintained by slowly evolving, closely related strains in Finnish pig farms
title_sort low level colonization of methicillin resistant staphylococcus aureus in pigs is maintained by slowly evolving closely related strains in finnish pig farms
topic Antimicrobial resistance
cgMLST
LA-MRSA
Livestock-associated methicillin-resistant Staphylococcus aureus
url https://doi.org/10.1186/s13028-022-00653-y
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