Test yourself: Health care-associated infections
From the April ACP Hospitalist, copyright © 2008 by the American College of Physicians
The following cases and commentary, which address health care-associated infections, are excerpted from ACP’s Medical Knowledge Self-Assessment Program (MKSAP14).
Case 1: Management of ventilator-associated pneumonia
A 36-year-old woman admitted to the intensive care unit with Guillain-Barré syndrome develops ventilator-associated pneumonia on day 11 of her hospitalization. An endobronchial aspirate is obtained, and therapy with vancomycin, piperacillin and amikacin is started. The culture results of her endobronchial aspirate reveal methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa. Both pathogens are susceptible to the antibiotics that were started. On the eighth day of antibiotic therapy, she is afebrile, the chest radiograph shows a diminishing infiltrate, her tracheobronchial secretions are scanty and her oxygenation status on 40% oxygen is adequate.
Which of the following decisions concerning her antibiotic therapy is appropriate at this time?
A. Stop all three antibiotics
B. Stop vancomycin only
C. Stop piperacillin and amikacin
D. Continue all antibiotics until two weeks of therapy is completed
E. Obtain additional cultures and base decision on culture results
Case 2: Prophylaxis of health care workers for meningococcus
A 24-year-old woman is brought to the emergency department because of fever, photophobia and a stiff neck. On physical examination, the patient is irritable. Temperature is 40°C (104°F). There is nuchal rigidity, and a purpuric rash is seen on dependent areas of the body. While in the emergency department, the patient develops respiratory distress and requires intubation. She is subsequently admitted to the intensive care unit (ICU).
During transfer, the patient is isolated with droplet precautions, and all health care workers wear masks and use the appropriate barriers. Lumbar puncture is done in the ICU, and cerebrospinal fluid examination shows gram-negative diplococci, consistent with meningitis.
Which of the following health care workers require antibiotic prophylaxis?
A. All staff who were present in the emergency department and ICU when the patient was in these areas
B. All staff who examined the patient in the emergency department and ICU
C. The resident who intubated the patient in the emergency department
D. Prophylaxis is not required for any staff
Case 3: Catheter-related bloodstream infections
An excessive number of central line catheter-related bloodstream infections are occurring in an intensive care unit. The infections develop within one week of catheter placement.
A colleague is observed placing a central venous catheter. She washes her hands with alcohol gel, selects the subclavian site for insertion, and cleanses the site with povidone-iodine. The patient is covered in a large sterile drape, and the colleague wears a mask, sterile gown and gloves.
Which of the observed practices is most likely to have contributed to the increased rate of bloodstream infections?
A. Hand washing before the procedure
B. Selection of the subclavian site for catheter insertion
C. Cleansing of the catheter insertion site
D. Draping of the patient
E. Protective garb (mask, gown, gloves) of the colleague
Case 4: Surgical site infection
A 68-year-old man requires preoperative assessment for potential surgical risks before undergoing coronary artery bypass graft surgery. The patient has congestive heart failure, type 1 diabetes mellitus and chronic obstructive pulmonary disease. The cardiac surgeon expects the procedure to last approximately 5 hours. Because the patient is at high risk for a surgical site infection, cefazolin will be used for perioperative prophylaxis.
Which of the following cefazolin regimens is most appropriate?
A. Begin cefazolin 30 minutes to one hour preoperatively; repeat the dose after three and a half to four hours intraoperatively; then repeat the dose every eight hours for 24 hours postoperatively
B. Begin cefazolin before surgery; repeat the dose after three and a half to four hours intraoperatively; then repeat the dose every eight hours until the surgical drains are removed
C. Begin cefazolin eight hours before surgery; then repeat the dose every eight hours for 24 hours postoperatively
D. Begin cefazolin 24 hours before surgery; then repeat the dose every eight hours for 48 hours postoperatively
Case 5: Needlestick injury
A 30-year-old female medical resident draws a sample for an arterial blood gas determination from a patient who is seropositive for HIV and hepatitis C antibodies. The patient’s hepatitis B status is not known. The resident sustains a needlestick resulting in a deep injury on her left hand.
The resident is seen immediately, and the wound is washed. She is not pregnant and is taking an oral contraceptive. Results of the source patient’s CD4 cell count, plasma HIV RNA viral load and hepatitis C viral load are pending.
In addition to counseling, which of the following is most appropriate for the resident?
A. No additional measures are required
B. Begin zidovudine within two hours of the needlestick injury
C. Begin two or three antiretroviral agents within two hours of the needlestick injury
D. Begin two or three antiretroviral agents plus interferon-alfa within two hours of the needlestick injury
Case 6: Suspected TB
A 39-year-old migrant worker from Central America comes to the emergency department because of a two-month history of cough, occasional fever, night sweats, a 4.5-kg (10-lb) weight loss and one episode of hemoptysis. The patient does not smoke or use alcohol or illicit drugs. Family members and friends are well, and he is unaware of exposure to anyone with tuberculosis. He has never received bacille Calmette-Guérin vaccine. The patient is in a monogamous sexual relationship and has never been tested for HIV.
Which of the following precautions is needed before evaluating this patient?
A. A mask for the patient
B. Droplet precautions for health care workers
C. Airborne isolation of the patient and personal respirators for health care workers
D. No special precautions are required
Case 7: Prevention of ventilator-associated pneumonia
A 25-year-old man is admitted to the intensive care unit after sustaining a closed head injury and a pneumothorax in a motor vehicle accident. He scores 5/15 on the Glasgow Coma Scale. A ventriculostomy tube and chest tube are placed, and intubation and mechanical ventilation are required to reduce elevated intracranial pressure. Enteral feedings are resumed on the second hospital day, but mechanical ventilation is needed for one week.
Which of the following may reduce the risk of ventilator-associated pneumonia in this patient?
A. Begin H2-receptor antagonists
B. Begin prophylactic intravenous antibiotics
C. Keep the patient in a semi-recumbent (45-degree angle) position
D. Change the ventilator tubing every 3 days
E. Avoid subglottic suctioning through the endotracheal tube
Answers and commentary
Case 1
.Correct answer: A. Stop all three antibiotics
Until recently, the accepted duration of therapy for ventilator-associated pneumonia was 15 days or even up to three weeks. Studies have shown, however, that this prolonged duration of antibiotics may not be necessary. Duration of antibiotic therapy should be based on clinical resolution of symptoms and signs of infection, radiologic improvement and requirement for less ventilatory support with improving oxygenation. Patients with ventilator-associated pneumonia who respond adequately to the antibiotics, whose pathogens are susceptible to the initial antibiotic regimen and who are immunocompetent are candidates for short-term antibiotic therapy. The patient in this question meets all of these criteria for discontinuing antibiotics. Another reason to discontinue antibiotics early is when an alternative diagnosis, especially atelectasis, is found that explains the infiltrate and clinical manifestations suspicious of ventilator-associated pneumonia.
Although a subgroup analysis of one study showed Pseudomonas infections to be associated with more frequent relapse if treated with eight days of antibiotics versus 15 days, there was no difference in mortality. In this young patient without comorbidities and with good clinical response, it would be reasonable to discontinue the antibiotics and follow closely. Repeat endobronchial aspirate cultures should not be used to determine the discontinuation of antibiotics. In fact, it has been shown that bacterial colonization, especially with nonfermenting bacilli such as Pseudomonas, persists in spite of resolution of signs and symptoms of pneumonia.
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Case 2
.Correct answer: C. The resident who intubated the patient in the emergency department.
The patient presents with the classic manifestations of meningococcal infection. Transmission is from person to person, primarily by the respiratory route, but requires very close contact such as kissing. Household contacts should receive prophylaxis. However, only health care workers who have contact with respiratory secretions require prophylaxis. In general, infection is spread by large droplets and requires contact of less than three feet for transmission. Intubation and suctioning are considered activities that increase the risk of transmission, whereas examination of the patient does not generally constitute an exposure. Persons who are wearing masks are not considered exposed. Therefore, the only person who needs prophylaxis is the resident who was in contact with secretions when he intubated the patient.
Administering prophylaxis to all staff in the emergency department and intensive care unit is not needed and would result in unnecessary use of antibiotics for many persons who did not have significant exposure to the patient. Transmission of Neisseria meningitidis has never been documented to be a risk when droplet precautions are instituted and health care workers are masked and use appropriate hand hygiene. Examining a patient, unless the examiner is coughed upon, does not result in sufficient exposure to put a health care worker at risk of secondary acquisition.
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Case 3
.Correct answer: C. Cleansing of the catheter insertion site.
Catheter-associated bloodstream infections are preventable. Although extensive guidelines to prevent these infections have been published, several simple steps can significantly reduce a patient’s risk of developing an infection. In the insertion procedure described here, chlorhexidine would have been more effective than povidone-iodine for cleansing the patient’s skin. Chlorhexidine is a superior skin cleanser and has residual activity for at least 30 minutes after it is applied. A meta-analysis showed that use of chlorhexidine reduced catheter-associated colonization and bloodstream infections by 50% when compared with use of povidone-iodine.
Hand washing before any procedure is critical. Either washing with soap and water for at least 15 seconds or using alcohol-based gels is appropriate. Use of a subclavian site is also appropriate. A subclavian site is associated with a lower risk of colonization and infection than other intravascular sites. In addition, a subclavian site is easier to keep dressed. Draping the patient and use of protective garb are also correct because maximal barrier precautions (large sterile drape to cover the patient and sterile gown, gloves and mask for the operator) reduce intravascular line infections three- to six-fold.
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Case 4
.Correct answer: A. Begin cefazolin 30 minutes to one hour preoperatively; repeat the dose after three and a half to four hours intraoperatively; then repeat the dose every eight hours for 24 hours postoperatively.
Surgical site infections are a common complication of operations, especially coronary artery bypass graft surgery. Several simple interventions are extremely effective for reducing the risk of such infections. One of the most important interventions is the appropriate dose, timing and duration of perioperative antibiotics. These ideally should be administered 30 to 60 minutes before the incision is made. For “clean procedures,” an antibiotic such as cefazolin provides appropriate coverage for skin flora. The antibiotic dose should be repeated intraoperatively when the surgery lasts longer than three and a half to four hours and should be given for no more than 24 hours postoperatively.
There are no data to suggest that prolonged use of antibiotics postoperatively prevents surgical site infections, and experts recommend stopping the drug no later than 24 hours after surgery.
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Case 5
.Correct answer: C. Begin two or three antiretroviral agents within two hours of the needlestick injury.
The primary pathogens associated with bloodborne exposures in health care workers are HIV, hepatitis B and hepatitis C. Recommendations for postexposure prophylaxis for HIV are updated periodically and are based on the type of exposure, the depth of the wound or potential for penetration of the substance and the indications and contraindications for prophylaxis in the health care worker. The U.S. Public Health Service guidelines for HIV postexposure prophylaxis have recently been revised, and two or three antiretroviral agents are now recommended for a deep, penetrating injury when the source patient is HIV seropositive. All wounds or splashes should be washed, and baseline serologic studies should be obtained after the type, depth of the exposure and the infectious status of the blood are ascertained. All persons evaluated should have current tetanus/diphtheria immunizations. If acute hepatitis C infection is detected following an occupational exposure (i.e., hepatitis C viremia or seroconversion), hepatitis C therapy, such as interferon-alfa, should be considered, but this is not started immediately after the injury is received.
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Case 6
.Correct answer: C. Airborne isolation of the patient and personal respirators for health care workers.
This patient’s symptoms are highly suggestive of tuberculosis. Perhaps the greatest risk of transmission of mycobacteria to health care workers is due to a delay in diagnosis because of a patient’s atypical presentation or apparent lack of risk factors for tuberculosis. Most mycobacterial infections are transmitted from person to person by airborne particles. Preventing these particles from contacting nonimmune hosts interrupts transmission.
This patient must be placed in airborne isolation to protect health care workers and other patients. Droplet precautions are not sufficient. In addition, health care workers must wear approved respirators with increased filtration capacity, such as an N95 mask or a powered-air purifying respirator (PAPR). The patient should wear a surgical mask when being transported.
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Case 7
.Correct answer: C. Keep the patient in a semi-recumbent (45-degree angle) position.
This patient is at high risk for ventilator-associated pneumonia (VAP) because of chest trauma, a Glasgow Coma Scale score of less than 9, the need for mechanical ventilation and the early resumption of enteral feedings. To prevent nosocomial pneumonia, the CDC recommends interventions to decrease aspiration, such as raising the head of the bed to a 45-degree angle, maintaining gastric acidity, maximizing nutrition, preventing colonization or cross-contamination by the hands of health care workers and manipulating respiratory-tract equipment in a sterile fashion and disinfecting the equipment appropriately.
Maintaining patients in a semi-recumbent position has been shown to decrease VAP and the time to developing pneumonia. One study demonstrated that nosocomial pneumonia developed in 8% of mechanically ventilated patients kept semi-recumbent and 43% of those kept supine.
H2-receptor blockers are a risk factor for development of VAP because they reduce gastric acidity. There are no data to confirm that use of prophylactic intravenous antibiotics prevents pneumonia, and antibiotics may increase the risk of colonization with resistant organisms. Changing tubing every three days is not necessary. Several clinical trials have shown that changing circuit tubing only every two weeks in adult patients does not increase the risk of infection. Endotracheal tubes that do not allow suctioning of subglottic secretions increase, rather than decrease, the risk of pneumonia in patients who are intubated for long periods.
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The information included herein should never be used as a substitute for clinical judgment and does not represent an official position of ACP. Click here for more information on MKSAP.
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