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Molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization and infection isolates in a Veterans Affairs hospital.

Eko KE, Forshey BM, Carrel M, Schweizer ML, Perencevich EN, Smith TC - Antimicrob Resist Infect Control (2015)

Bottom Line: The most common spa types were t002 (and other CC5-associated strains; 65%) and t008 (and other CC8-associated strains; 20%).MRSA colonization was more common among patients with infections (71%) compared with the general screening population (7%).Our data demonstrate a direct link between antecedent nasal colonization and subsequent MRSA infection.

View Article: PubMed Central - PubMed

Affiliation: Department of Epidemiology, University of Iowa College of Public Health, Iowa City, IA 52246 USA.

ABSTRACT

Background: Nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) is associated with increased infection risk, yet colonization and infection isolates are rarely compared within the same study. The objectives of this study were to compare colonization and infection isolates from a Veterans Administration hospital in Iowa, and to determine the prevalence of livestock-associated MRSA (LA-MRSA) colonization and infection in a state with high livestock density.

Methods: All patients with available MRSA isolates collected through routine nasal screening (73%; n = 397) and from infections (27%; n = 148) between December 2010 and August 2012 were included and tested for spa type and presence of PVL and mecA genes. Clinical isolates were tested for antibiotic resistance patterns. Paired colonization and infection isolates were compared for genetic and phenotypic congruity.

Results: The most common spa types were t002 (and other CC5-associated strains; 65%) and t008 (and other CC8-associated strains; 20%). No classic LA-MRSA spa types were identified. CC5-associated strains were less likely to be associated with infections (22%; 77/353) compared with CC8-associated strains (49%; 53/109). MRSA colonization was more common among patients with infections (71%) compared with the general screening population (7%). In most cases (82%; 28/34), paired colonization and infection isolates were genetically and phenotypically indistinguishable.

Conclusions: Our data demonstrate a direct link between antecedent nasal colonization and subsequent MRSA infection. Further, our data indicate variability in colonization and infection efficiency among MRSA genotypes, which points to the need to define the molecular determinants underlying emergence of S. aureus strains in the community and nosocomial setting.

No MeSH data available.


Related in: MedlinePlus

Residential locations of patients with MRSA nasal isolates collected during admission screening at the ICVAHCS. (A). Urban areas of Cedar Rapids (B), Iowa City/Coralville (C), and the Quad Cities (D) are shown in greater detail.
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Fig1: Residential locations of patients with MRSA nasal isolates collected during admission screening at the ICVAHCS. (A). Urban areas of Cedar Rapids (B), Iowa City/Coralville (C), and the Quad Cities (D) are shown in greater detail.

Mentions: To determine the spatial heterogeneity of MRSA isolates, spa types of colonization isolates were mapped to patients’ home addresses (n = 115) (Figure 1A). Of these, 15 (13%) were t008, 70 (61%) were t002, and 30 (26%) were classified as “other”, consistent with the overall frequency of spa types among colonization isolates (13%, 54%, and 33% for t008, t002, and “other”, respectively). No duplicate samples (i.e. two from one patient) were included in the geocoded dataset. The overall spatial pattern reflects the typical service area of the ICVAHCS, drawing primarily from Eastern Iowa but also from patients located in other areas of Iowa and adjacent states. A cluster of t008 isolates is observed in the patients residing in the Cedar Rapids urban area, while t002 is more prevalent in Iowa City/Coralville and the Quad Cities (Figure 1B-D). The dates of isolation for the t008 samples in Cedar Rapids span over 9 months, so are not reflective of a single outbreak.Figure 1


Molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization and infection isolates in a Veterans Affairs hospital.

Eko KE, Forshey BM, Carrel M, Schweizer ML, Perencevich EN, Smith TC - Antimicrob Resist Infect Control (2015)

Residential locations of patients with MRSA nasal isolates collected during admission screening at the ICVAHCS. (A). Urban areas of Cedar Rapids (B), Iowa City/Coralville (C), and the Quad Cities (D) are shown in greater detail.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4383227&req=5

Fig1: Residential locations of patients with MRSA nasal isolates collected during admission screening at the ICVAHCS. (A). Urban areas of Cedar Rapids (B), Iowa City/Coralville (C), and the Quad Cities (D) are shown in greater detail.
Mentions: To determine the spatial heterogeneity of MRSA isolates, spa types of colonization isolates were mapped to patients’ home addresses (n = 115) (Figure 1A). Of these, 15 (13%) were t008, 70 (61%) were t002, and 30 (26%) were classified as “other”, consistent with the overall frequency of spa types among colonization isolates (13%, 54%, and 33% for t008, t002, and “other”, respectively). No duplicate samples (i.e. two from one patient) were included in the geocoded dataset. The overall spatial pattern reflects the typical service area of the ICVAHCS, drawing primarily from Eastern Iowa but also from patients located in other areas of Iowa and adjacent states. A cluster of t008 isolates is observed in the patients residing in the Cedar Rapids urban area, while t002 is more prevalent in Iowa City/Coralville and the Quad Cities (Figure 1B-D). The dates of isolation for the t008 samples in Cedar Rapids span over 9 months, so are not reflective of a single outbreak.Figure 1

Bottom Line: The most common spa types were t002 (and other CC5-associated strains; 65%) and t008 (and other CC8-associated strains; 20%).MRSA colonization was more common among patients with infections (71%) compared with the general screening population (7%).Our data demonstrate a direct link between antecedent nasal colonization and subsequent MRSA infection.

View Article: PubMed Central - PubMed

Affiliation: Department of Epidemiology, University of Iowa College of Public Health, Iowa City, IA 52246 USA.

ABSTRACT

Background: Nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) is associated with increased infection risk, yet colonization and infection isolates are rarely compared within the same study. The objectives of this study were to compare colonization and infection isolates from a Veterans Administration hospital in Iowa, and to determine the prevalence of livestock-associated MRSA (LA-MRSA) colonization and infection in a state with high livestock density.

Methods: All patients with available MRSA isolates collected through routine nasal screening (73%; n = 397) and from infections (27%; n = 148) between December 2010 and August 2012 were included and tested for spa type and presence of PVL and mecA genes. Clinical isolates were tested for antibiotic resistance patterns. Paired colonization and infection isolates were compared for genetic and phenotypic congruity.

Results: The most common spa types were t002 (and other CC5-associated strains; 65%) and t008 (and other CC8-associated strains; 20%). No classic LA-MRSA spa types were identified. CC5-associated strains were less likely to be associated with infections (22%; 77/353) compared with CC8-associated strains (49%; 53/109). MRSA colonization was more common among patients with infections (71%) compared with the general screening population (7%). In most cases (82%; 28/34), paired colonization and infection isolates were genetically and phenotypically indistinguishable.

Conclusions: Our data demonstrate a direct link between antecedent nasal colonization and subsequent MRSA infection. Further, our data indicate variability in colonization and infection efficiency among MRSA genotypes, which points to the need to define the molecular determinants underlying emergence of S. aureus strains in the community and nosocomial setting.

No MeSH data available.


Related in: MedlinePlus