264. Polymicrobial Soft Tissue Infection (P-STI) in the Lower Extremities, Perineal, Sacral or Gluteal Locations: Is Empirical Coverage for Staphylococcus Aureus (SA) Necessary.
Session: Poster Abstract Session: Clinical: Skin and Soft Tissue
Thursday, October 5, 2017
Room: Poster Hall CD
Posters
  • Tanveer IDSA 2017 FINAL (1).pdf (1.0 MB)
  • Background: S. aureus is a common cause of STI, usually monobacterial (M-STI). The frequency of S. aureus (SA) in P-STI is unsubstantiated. 

    Methods: A retrospective review of positive microbiology culture results (1/1/2015-6/30-2016), selection of soft tissue samples (ST-S) from sacrum/gluteal/perineal (SGP) and lower extremity (LE) sources and review of their records. Each patient was included once and the first episode of infection was selected. Cases with and without SA were compared. The differences in categorical and continuous variables were assessed by Chi-square and Student t tests for, respectively. The predictors of S. aureus were identified by logistic regression (using SPSS) and a p value <0.05 was considered significant.

    Results: We reviewed 2419 cultures, 834 were ST-S; 276 met our selection criteria including 210 LE and 66 SGP. 212 (76.8%) of selected cases were P-STI. SA was encountered in 83 (39.2%) P-STI and 39 (60.9%) M-STI (p=0.002); MRSA accounted for 65.2% of SA isolates. Characteristics of patients with P-STI were stratified according to SA status (table). SA was less frequent in SGP sources (p=0.01), Predictors of SA were the presence of drainage (OR=2.0; 95%CI: 1.11, 3.46) and LE site (OR=2.11; CI: 1.10, 4.38). In LE cases, SA was uncommon in cases with necrosis/gangrene (OR=0.44; CI: 0.23, 0.86).

    Conclusion: Most SA STIs are monomicrobial. It is less common in SGP sites, cases with gangrene/necrosis and in cases without drainage. Such patients may not need empirical anti-staphylococcal therapy.

     

    Table: Characteristics of polymicrobial soft tissue infection in the lower extremities and sacrum/gluteal/perineal sites, stratified according to S. aureus status

     

     

    S. aureus status (n)

     

    Characteristic: n (%)

    Non S. aureus (129)

    S. aureus (83)

    p

    Age: means ±SD (y)

    56.9 ±16.3

    55.8 ±16.0

    0.6

    Male gender

    78 (60.5)

    59 (71.1)

    0.1

    Diabetes

    73 (56.6)

    45 (54.2)

    0.4

    Kidney disease

    35 (27.1)

    23 (27.7)

    0.5

    Paraplegia

    16 (12.4)

    12 (14.5)

    0.4

    Peripheral arterial disease

    36 (20.0)

    24 (21.8)

    0.7

    Intravenous drug user

    1 (0.8)

    3 (3.6)

    0.2

    Site

          Lower extremities

    87 (58.3)

    69 (77.3)

    0.006

          Sacrum/gluteal/ perineal

    42 (20.7)

    8 (9.9)

    <0.001

    Necrosis

    61 (47.3)

    30 (36.1)

    0.07

    Erythema

    106 (58.9)

    72 (65.5)

    0.3

    Swelling

    110 (61.1)

    76 (69.1)

    0.2

    Abscess

    32 (24.8)

    14 (16.9)

    0.2

    Drainage

    51 (39.5)

    48 (57.8)

    0.01

    Fever

    35 (27.1)

    25 (30.1)

    0.6

    Leukocytosis

    70 (54.3)

    35 (42.2)

    0.09

     

    Farah Tanveer, MD, Ashish Bhargava, MD, Kathleen Riederer, MT, Leonard Johnson, MD and Riad Khatib, MD, Infectious Diseases, Saint John Hospital and Medical Center; Ascension, Grosse Pointe Woods, MI

    Disclosures:

    F. Tanveer, None

    A. Bhargava, None

    K. Riederer, None

    L. Johnson, None

    R. Khatib, None

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