Laboratory Studies
The simplest, and usually the quickest, staining method involves obtaining a Gram stain for infective organisms. Staining for fungal elements can be obtained at the same time.
Most laboratories routinely will culture for both aerobic and anaerobic organisms. Fungal cultures can be requested. Isolation of single colonies allows further growth and identification of the specific organism. Sensitivity testing then follows mainly for aerobic organisms.
Other techniques include the following:
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Tests for antigens from the organism through enzyme-linked immunoassay (ELISA) or radioimmunoassay
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Detection of antibody response to the organism in the host sera
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Detection of RNA or DNA sequences or protein from the infective organism by Northern, Southern, or Western blotting, respectively
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Polymerase chain reaction (PCR) to detect small amounts of microbial DNA
Ultrasonography
Ultrasonography can be applied to the infected wound area to assess whether there is a collection for which drainage is required.
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Wound infection due to disturbed coagulopathy. This patient has a pacemaker (visible below right clavicular space) and had previous cardiac surgery (median sternotomy wound visible) for a rheumatic mitral valve disorder, which was replaced. The patient was taking anticoagulants preoperatively. Despite converting to low-molecular weight subcutaneous heparin treatment and establishing normal coagulation studies, she developed a postoperative hematoma with subsequent wound infection. She had the hematoma evacuated and was administered antibiotic treatment as guided by microbiological results, and the wound was left to heal by secondary intention.
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Abscess secondary to a subclavian line.
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Definitions of surgical site infection (SSI).
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Factors that affect surgical wound healing.
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Large ulceration in a tattoo. A 33-year-old man presented with a superficial ulceration about 4 weeks after a red tattoo on his forearm. Microbial swabs remained negative. His medical history was uneventful and he was in good general health. No reason for this uncommon reaction could be identified. Image courtesy of the National Institutes of Health.
Tables
- Table 1. Pathogens Commonly Associated with Wound Infections and Frequency of Occurrence [8]
- Table 2: Surgical Wound Classification and Subsequent Risk of Infection (If No Antibiotics Used) [8, 10]
- Table 3. Recommendations for Prophylactic Antibiotics as Indicated by Probable Infective Microorganism Involved [8, 29]
- Table 4. Predictive Percentage of SSI Occurrence by Wound Type and Risk Index* [30]
- Table 5. American Society of Anesthesiologists (ASA) Classification of Physical Status [31]
- Table 6. Data Support Recommendations
Pathogen |
Frequency (%) |
Staphylococcus aureus |
20 |
Coagulase-negative staphylococci |
14 |
Enterococci |
12 |
Escherichia coli |
8 |
Pseudomonas aeruginosa |
8 |
Enterobacter species |
7 |
Proteus mirabilis |
3 |
Klebsiella pneumoniae |
3 |
Other streptococci |
3 |
Candida albicans |
3 |
Group D streptococci |
2 |
Other gram-positive aerobes |
2 |
Bacteroides fragilis |
2 |
Classification |
Description |
Infective Risk (%) |
Clean (Class I) |
Uninfected operative wound No acute inflammation Closed primarily Respiratory, gastrointestinal, biliary, and urinary tracts not entered No break in aseptic technique Closed drainage used if necessary |
< 2 |
Clean-contaminated (Class II) |
Elective entry into respiratory, biliary, gastrointestinal, urinary tracts and with minimal spillage No evidence of infection or major break in aseptic technique Example: appendectomy |
< 10 |
Contaminated (Class III) |
Nonpurulent inflammation present Gross spillage from gastrointestinal tract Penetrating traumatic wounds < 4 hours Major break in aseptic technique |
About 20 |
Dirty-infected (Class IV) |
Purulent inflammation present Preoperative perforation of viscera Penetrating traumatic wounds >4 hours |
About 40 |
Operation |
Expected Pathogens |
Recommended Antibiotic |
Orthopedic surgery (including prosthesis insertion), cardiac surgery, neurosurgery, breast surgery, noncardiac thoracic procedures |
S aureus, coagulase-negative staphylococci |
Cefazolin 1-2 g |
Appendectomy, biliary procedures |
Gram-negative bacilli and anaerobes |
Cefazolin 1-2 g |
Colorectal surgery |
Gram-negative bacilli and anaerobes |
Cefotetan 1-2 g or cefoxitin 1-2 g plus oral neomycin 1 g and oral erythromycin 1 g (start 19 h preoperatively for 3 doses) |
Gastroduodenal surgery |
Gram-negative bacilli and streptococci |
Cefazolin 1-2 g |
Vascular surgery |
S aureus, Staphylococcusepidermidis, gram-negative bacilli |
Cefazolin 1-2 g |
Head and neck surgery |
S aureus, streptococci, anaerobes and streptococci present in an oropharyngeal approach |
Cefazolin 1-2 g |
Obstetric and gynecological procedures |
Gram-negative bacilli, enterococci, anaerobes, group B streptococci |
Cefazolin 1-2 g |
Urology procedures |
Gram-negative bacilli |
Cefazolin 1-2 g |
At Risk Index |
Predictive Percentage of SSI |
0 |
1.5 |
1 |
2.9 |
2 |
6.8 |
3 |
13.0 |
*Hospital Infection Control Practices Advisory Committee (HICPAC) recommendations (partial) for the prevention of SSIs, April 1999 (non–drug based) |
|
ASA Score |
Characteristics |
1 |
Normal healthy patient |
2 |
Patient with mild systemic disease |
3 |
Patient with a severe systemic disease that limits activity but is not incapacitating |
4 |
Patient with an incapacitating systemic disease that is a constant threat to life |
5 |
Moribund patient not expected to survive 24 hours with or without operation |
Category |
Description |
Category IA |
Well designed, experimental, strong; recommended (Category I*) clinical or epidemiological best practice; should be studies; adapted by all practices |
Category IB |
Some experimental, fairly strong; recommended (Category II*) clinical or epidemiological best practice; should be studies and theoretical grounds; adapted by all practices |
Category II |
Fewer scientific supporting data; limited to specific nosocomial (Category III*) problems |
No recommendation |
Insufficient scientific personnel judgment for use (Category III*) supporting data |
*Previous nomenclature of 1992 CDC guidelines |
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