surgical site infections

Surgical Site Infection

Dr. Hany Lotfy MDAssistant professor of medical microbiology and Immunology

Sulaiman Al Rajhi Colleges

2015

Surgical Site Infections (SSI)

Second most common nosocomial infection (17%). Most common nosocomial infection among surgical

patients (38%).2/3 incisional.1/3 organs or spaces accessed during surgery.

About 300,000 SSIs occur each year. Prolong hospital stay by 7.4 days.

Definition

A surgical site infection (SSI) is an infection that

occurs after surgery in the part of the body

where the surgery took place.

Colonization vs Contamination.. Definitions

Colonization: Bacteria present in a wound with no signs or symptoms of

systemic inflammation. Usually less than 105 cfu/mL.

Contamination: Transient exposure of a wound to bacteria. Varying concentrations of bacteria possible. Time of exposure suggested to be < 6 hours. SSI prophylaxis best strategy.

SSI – Definitions

Infection: Systemic and local signs of inflammation. Bacterial counts ≥ 105 CFU/mL.

1. Superficial Incisional SSI

Infection occurs within 30 days after the operation and involves only skin or subcutaneous tissue of the incision.

Subcutaneous tissue

SkinSuperficial incisional SSI

2. Deep Incisional SSI

Infection occurs within 30 days after the operation if no implant is left in place or within 1 year if implant is in place.

The infection appears to be related to the operation and the infection involves the deep soft tissue (e.g., fascia and muscle layers).

Deep soft tissue (fascia & muscle)

Deep incisional SSI

Superficial incisional SSI

3. Organ/Space SSI

Infection occurs within 30 days after the operation if no implant is left in place or within 1 year if implant is in place and the infection appears to be related to the operation.

Infection involves any part other than the incision, which was opened or manipulated during the operation

Deep incisional SSI

Superficial incisional SSI

Organ/space SSIOrgan/space

Sources of SSI Pathogens

1. Endogenous flora of the patient.

2. Operating theater environment.

3. Hospital personnel.

4. Seeding of the operative site from distant focus of infection (prosthetic device, implants).

Classification and Rates of SSIClass Type Description %

I Clean An uninfected operative wound without inflammation.

No intrinsic bacterial flora

8 %

II Clean / contaminated

Operative wounds in which the respiratory, alimentary, genital, or urinary tracts are entered under controlled conditions and without unusual contamination.

Operations involving the biliary tract, appendix, vagina, and oropharynx

22%

III Contaminated Open, fresh, accidental wounds. Involves spillage of viscus content.

30%

IV Dirty Old traumatic wounds with retained devitalized tissue and those that involve existing clinical infection or perforated viscera.

40%

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”Etiology of SSI

Most Common Pathogens Associated With Nosocomial Infections

Pathogen All Sites BSI Pneumonia SSIn=235,758 n=50,091 n=64,056 n=22,043

Coag-neg Staph 14.3 39.3 2.5 13.5S aureus 11.4 10.7 16.8 12.6Enterococci spp. 8.1 10.3 1.9 14.5P. aeruginosa 9.9 3.0 16.1 9.2Enterobacter spp. 7.3 4.2 10.7 8.8E. coli 7.0 2.9 4.4 7.1C. albicans 6.6 4.9 4.0 4.8K. pneumoniae 4.7 2.9 6.5 3.5Others 30.7 21.8 37.1 26.0

Relative Percentage by Site of Infection

BSI=bloodstream infection; SSI=surgical site infection.Fridkin SK et al. Clin Chest Med. 1999;20:303-316.

“

”SSI – Risk Factors

A. Operation Factors

Duration of surgical scrub. Skin antisepsis. Preoperative shaving. Duration of operation. Antimicrobial prophylaxis. Operating room ventilation Inadequate sterilization of

instruments.

Foreign material at surgical site.

Surgical drains. Surgical technique:

Poor hemostasis. Failure to obliterate dead space. Tissue trauma.

B. Patient Factors

Age Increasing age. Diabetes. Smoking: delays primary

wound healing. Steroids. Malnutrition. Obesity. Prolonged preoperative stay.

Preoperative colonization with S. aureus.

Perioperative transfusion. Coexistent infections at a

remote body site. Altered immune response.

Bacterial dose Virulence

Impairedhost resistance

Risk of Infection

Bacterial dose Virulence

Impairedhost resistance

Risk of Infection

Bacterial dose Virulence

Impairedhost resistance

Virulence

Impairedhost resistance

Risk of InfectionRisk of Surgical Infection

Bacterial dose

“

”Diagnosis of SSI

1. Clinical picture

The typical features of wound infections: Increased exudate. Increased swelling. Increased erythema. Increased pain. Increased local temperature. Peri-wound cellulitis, change in appearance of granulation tissue

(discoloration, prone to bleed, highly friable). The failure of the wound to heal and progressive deterioration of

the wound.

Clinical picture

2. Laboratory

ESR…… ↑ Complete blood picture:

WBC…… ↑ CRP. Microbiological.

Sample:

Pus or exudates from infected wounds is usually sampled by swabbing deep in the wound, which must be soaked well in the exudates.

A specimen of the pus itself is always preferred and can be obtained by using a syringe and transfer to a sterile tube or screw capped bottles.

Pieces of tissues removed at operation are sent to the laboratory for bacterial examination, these tissues are homogenized in a tissue grinder with a little broth.

Specimen Collection:

The gold standard collection method is to do a

tissue biopsy or needle aspirate of the leading

edge of the wound after debridement.

If a tissue biopsy is not possible????

Cleanse the wound with sterile saline Vigorously swab the base of the lesion Surface wounds place the swab in a sterile

container for transport. Deep wounds place the swab in a sterile anaerobic

container for transport.

SAMPLING

Laboratory

Transfer swab

Bedside culture

Transport media

In the laboratory

1. Culture on suitable media.

2. Incubation:

Aerobic.

Anaerobic.

3. Identification of the organism.

4. Antibiotic sensitivity test.

“

”Prevention of SSI

Pre-operative

Avoid antibiotics. Minimize hospitalisation. Treat any remote infection. Avoid shaving. Chlorhexidine bath. Resolve obesity/malnutrition. Control smoking. Control diabetes.

Intra-operative

Skin preparation. Aseptic technique. Filtered air in operation room (OR). Antibiotic wound irrigation. Isolate clean / dirty surgical fields. Minimize drains. Minimize dead space haematomas and devitalised

tissue.

Post-operative

Proper dressing. Minimize catheters & IV lines.

Maintain oxygenation. Maintain hydration & nutrition. Antibiotic.

“

”TREATMRNT of SSI

Treatment

1. PREVENTIVE.2. Remove foreign bodies.3. Remove necrotic tissues.4. Antiseptics.5. Antibiotic sensitivity test……