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Nosocomial Infections

J.B. Handler, M.D.Physician Assistant ProgramUniversity of New England

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Abbreviations NCI- nosocomial infection IV- intravenous ICU- intensive care unit CCU- coronary care unit E coli- Escherichia coli Abd- abdomen C difficile- clostridium difficile S aureas- Staph aureas S epidermidis- Staph epidermidis S pyogenes- Strep pyogenes DC- discontinue

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Nosocomial Infections (NCI) Infections acquired in the hospital or

other in-patient health care facility, often developing within 48-72 hours of admission; NCI also common with prolonged hospitalization (seriously ill).

Historical information: Florence Nightingale (19th century) studies of

mortality in military hospitals. Infections carried by healthcare workers to

patients could be prevented by washing hands between patient contacts (20th century).

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Nosocomial Infections (NCI) Incidence: 5% of all hospitalized

patients in the U.S.; 2-4 million NCI annually with significant morbidity and 100,000 annual deaths.Cost: Billions of excess health care dollars.

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Sources of Infection Endogenous: skin, GI or respiratory tract;

often from organisms indigenous to those areas.

Exogenous: transmitted to the patient from external sources.

Modes of transmission: contact (C- difficile, Shigella, S aureas, S epidermidis, S pyogenes, viruses) droplet, airborne, common vehicle transmission (contaminated multi-med vial).

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Elevated Temperature Infection: Etiology of 75% of fevers. Drug fever Post-op fever (atelectasis) Pancreatitis MI Large hematoma Thromboembolic disease

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NCI: Key Issues Many infections are a direct result of

use of invasive devices for monitoring/treatment: IV catheters, central venous lines, Foley catheters, surgical drains, dialysis catheters and shunts, and oral or nasotracheal tubes for ventilatory support.

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NCI: Key Issues Patients are often seriously ill (ICU/CCU)

with prolonged hospitalization and may have received one or more courses of broad spectrum antibiotics. NCI are often antibiotic resistant. This includes Nafcillin, Cephalosporin and new Vancomycin resistant strains (enterococcus, emerging S aureas).

“Hospital ecology”: organisms previously identified with antibiotic resistance; very difficult to eradicate.

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NCI: Key Issues Antibiotic use must be limited to the

treatment of documented infections. Empiric therapy is indicated only in the presence of life threatening infections, and should be adjusted or discontinued based on culture results. Colonization does not warrant treatment and often contributes to unnecessary antibiotic use. Example: Positive urine culture in patient

with indwelling catheter without clinical evidence of cystitis or pyelonephritis.

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NCI: Key Issues Need reliable specimens for culture:

No cultures from existing IV lines If sepsis suspected: Need 2 or more blood

cultures from identified sites, remote from wounds.

Contaminated culture sites often lead to misdiagnosis of bacteremia (“pseudo-bacteremia”); may result in increased hospital stays, costs, and morbidity.

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NCI: Key Issues Important to consider culture results

(colony counts) and clinical information: is the patient clinically infected-signs and symptoms?

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Pathogens of NCI Enterobacteriaciae: E coli,

Klebsiella, Enterobacter, Pseudomonas, Proteus, Citrobacter, Actinobacter, others.

S aureas: Common nosocomial pathogen in U.S.

Coagulase negative Staphylococcus (S epidermidis).

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Pathogens of NCI Enterococcus C difficile: alarming rise in U.S Fungi: Candida- 4th most common

cause of blood stream and urinary NCI’s; often seen in immunocompromised host, following use of broad spectrum antibiotics.

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Prevention of NCI Universal precautions: Treat all

patients as if they have a potential blood-born transmissible disease. All body secretions/blood must be handled with care: Body substance isolation- health care workers to wear gloves.

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Prevention of NCI Limit use of urinary catheters, IV lines,

central lines, hyperalimentation lines and DC at earliest possible time. Use of specially prepared urinary catheters (silver alloy) and IV catheters (antibiotic impregnated) is developing.

Hand Washing: easiest and most cost effective means of preventing NCI. Important to do even when wearing gloves. Topical hand antiseptic (alcohol based) is

also very effective.

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Prevention of NCI Needle precautions essential to avoid blood

borne infection. Transmission based precautions: during

care of patients with documented infection that is important (epidemiological standpoint), and can be spread by contact, droplet and airborne transmission: Includes patient isolation, all contacts to wear

gloves, gowns and masks when indicated. TB isolation requires negative pressure ventilation.

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Urinary Tract Infections Most common site of NCI in U.S

(35%). Very low mortality (<0.1%) Bacteremia with gram negative sepsis

increases morbidity and mortality. Occurs in 3% of patients with nosocomial UTI

Assess for signs/sx of infection Temp, lower abd discomfort, flank pain

Urinalysis, including microscopic

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Urinary Tract Infections 80% of urinary NCI’s associated with

indwelling urinary catheters. Risk of bacteremia increases 3.6%/day of catheterization. Bacteriuria without actual infection

(colonization) occurs in 30% of patients with indwelling catheters. Removal of the catheter without antibiotic treatment is adequate treatment.

Pathogens: E.coli, Pseudomonas, Klebsiella, Candida.

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Nosocomial UTI: Pathophys Normally, defense mechanisms help

prevent infections- urine acidity, bladder emptying and urinary flow.

Bacteria enter via the catheter-migrate in the lumen and exterior catheter surface.

Important to prevention: closed, sterile drainage system (eliminate intralumenal migration). The distal end of the catheter has a closed connection to a sterile collection receptacle. Silver impregnated Foley catheters reduce risk.

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NCI: Bloodstream Incidence 250,000/yr in the U.S.

Increases hospitalization by avg of 7 days with 62,500 deaths annually.

These are extremely dangerous infections that can lead to septic shock, endocarditis and osteomyelitis (if Staph aureas) that can require days to weeks of IV antibiotic therapy.

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NCI: Bloodstream “Secondary” Infections (30-40%):

originate from infections at other body sites (urinary, surgical site, skin, pulmonary and others) that “seed” the circulation.

“Primary” Infections: Blood stream infections that cannot be attributed to another body site. Intravascular devices (IV, central venous catheters, shunts) are most common source. Central line sepsis: incidence 2-3%.

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Pathogens and Pathogenesis

Pathogens: Staph epidermitis, S aureas, Enterococcus, Candida, E coli, Klebsiella.

Pathogenesis (primary infection): migration of organisms from skin insertion site into the cutaneous tract along the external surface of the catheter until the tip is colonized release into bloodstream.

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Pathogens and Pathophys. Clinical presentation: high fevers, shaking

chills, hypotension (gram negative sepsis), bacterial emboli. Septic shock carries a mortality of 40-80%.

Documentation: 2 or more (+) blood cultures from 2 different anatomic sites remote from any IV lines, and never from existing lines.

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Prevention Limit use of central lines. Peripheral veins carry much lower risk of

sepsis. Need to change every 3 days. Site of Central Lines: Subclavian vein

lowest infection rate compared to Internal Jugular vein or Femoral vein. Central lines can be left in place for 7+ days if maintained adequately.

Remove central line if it is a possible source of infection and culture tip.

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Prevention Catheters impregnated with antibiotics,

chlorhexadine or silver sulfadiazine reduce rate of “line sepsis” but cost.

Operators must wear masks, gowns and gloves surgical scrub (central lines) and site prep with antiseptics like betadine.

Insertion site should be cleansed daily with antiseptics (chlorhexadine, betadine, providine-iodine or alcohol).

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Sepsis “Work-up” Suspected clinically by high fevers, chills,

etc. with central line in place. R/O allergic reaction/drug reaction. Urine culture, sputum culture if

applicable, and blood cultures from at least two different sites. Culture any suspicious skin lesions and surgical wounds where applicable. Aggressive culture work-up essential if source not obvious.

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Sepsis Treatment Empiric therapy with broad spectrum

antibiotic(s) pending culture results. Subsequent antibiotics based on culture

results. If a secondary source is not obtained and

S aureas sepsis confirmed: parenteral antibiotics for 2 wks prevent endocarditis or osteomyelitis.