Transferrin plays a role in host defense by
A. Sequestering iron, which is necessary for microbial growth
B. Increasing the ability of fibrinogen to trap microbes
C. Direct injury to the bacterial cell membrane
D. Direct injury to the bacterial mitochondria
Once microbes enter a sterile body compartment (eg, pleural or peritoneal cavity) or tissue, additional host defenses act to limit and/or eliminate these pathogens. Initially, several primitive and relatively nonspecific host defenses act to contain the nidus of infection, which may include microbes as well as debris, devitalized tissue, and foreign bodies, depending on the nature of the injury. These defenses include the physical barrier of the tissue itself, as well as the capacity of proteins, such as lactoferrin and transferrin, to sequester the critical microbial growth factor iron, thereby limiting microbial growth. In addition, fibrinogen within the inflammatory fluid has the ability to trap large numbers of microbes during the process in which it polymerizes into fibrin. Within the peritoneal cavity, unique host defenses exist, including a diaphragmatic pumping mechanism whereby particles including microbes within peritoneal fluid are expunged from the abdominal cavity via specialized structures on the undersurface of the diaphragm. Concurrently, containment by the omentum, the so-called “gatekeeper” of the abdomen and intestinal ileus, serves to wall off infection. However, the latter processes and fibrin trapping have a high likelihood of contributing to the formation of an intra-abdominal abscess. (See Schwartz 10th ed., p. 138.)
Which is NOT a component of systemic inflammatory response syndrome (SIRS)?
B. White blood cell (WBC) count
Infection is defined by the presence of microorganisms in host tissue or the bloodstream. At the site of infection the classic findings of rubor, calor, and dolor in areas such as the skin or subcutaneous tissue are common. Most infections in normal individuals with intact host defenses are associated with these local manifestations, plus systemic manifestations such as elevated temperature, elevated white blood cell (WBC) count, tachycardia, or tachypnea. The systemic manifestations noted above comprise the systemic inflammatory response syndrome (SIRS). (See Schwartz 10th ed., p. 138.)
The best method for hair removal from an operative field is
A. Shaving the night before
B. Depilating the night before surgery
C. Shaving in the operating room
D. Using hair clippers in the operating room
Hair removal should take place using a clipper rather than a razor; the latter promotes overgrowth of skin microbes in small nicks and cuts. Dedicated use of these modalities clearly has been shown to diminish the quantity of skin microflora. (See Schwartz 10th ed., p. 141.)
A patient with necrotizing pancreatitis undergoes computed tomography (CT)-guided aspiration, which results in growth of Escherichia coli on culture. The most appropriate treatment is
A. Culture-appropriate antibiotic therapy
B. Endoscopic retrograde cholangiopancreatography with sphincterotomy
C. CT-guided placement of drain(s)
D. Exploratory laparotomy
The primary precept of surgical infectious disease therapy consists of drainage of all purulent material, debridement of all infected, devitalized tissue, and debris, and/or removal of foreign bodies at the site of infection, plus remediation of the underlying cause of infection. A discrete, walled-off purulent fluid collection (ie, an abscess) requires drainage via percutaneous drain insertion or an operative approach in which incision and drainage take place. An ongoing source of contamination (eg, bowel perforation) or the presence of an aggressive, rapidly spreading infection (eg, necrotizing soft tissue infection) invariably requires expedient, aggressive operative intervention, both to remove contaminated material and infected tissue (eg, radical debridement or amputation) and to remove the initial cause of infection (eg, bowel resection). (See Schwartz 10th ed., p. 141.)
Which factor does NOT influence the development of surgical site infections (SSIs)?
B. Degree of microbial contamination of the wound
Surgical site infections (SSIs) are infections of the tissues, organs, or spaces exposed by surgeons during performance of an invasive procedure. SSIs are classified into incisional and organ/space infections, and the former are further subclassified into superficial (limited to skin and subcutaneous tissue) and deep incisional categories. The development of SSIs is related to three factors: (1) the degree of microbial contamination of the wound during surgery, (2) the duration of the procedure, and (3) host factors such as diabetes, malnutrition, obesity, immune suppression, and a number of other underlying disease states. (See Schwartz 10th ed., p. 147.)
During a laparoscopic appendectomy, a large bowel injury was caused during trochar placement with spillage of bowel contents into the abdomen. What class of surgical wound is this?
B. Class II (clean/contaminated)
C. Class III (contaminated)
Surgical wounds are classified based on the presumed magnitude of the bacterial load at the time of surgery. Clean wounds (Class I) include those in which no infection is present; only skin microflora potentially contaminate the wound, and no hollow viscus that contains microbes is entered. Class ID wounds are similar except that a prosthetic device (eg, mesh or valve) is inserted. Clean/contaminated wounds (Class II) include those in which a hollow viscus, such as the respiratory, alimentary, or genitourinary tracts, with indigenous bacterial flora is opened under controlled circumstances without significant spillage of contents. Contaminated wounds (Class III) include open accidental wounds encountered early after injury, those with extensive introduction of bacteria into a normally sterile area of the body due to major breaks in sterile technique (eg, open cardiac massage), gross spillage of viscus contents such as from the intestine, or incision through inflamed, albeit nonpurulent, tissue. Dirty wounds (Class IV) include traumatic wounds in which a significant delay in treatment has occurred and in which necrotic tissue is present, those created in the presence of overt infection as evidenced by the presence of purulent material, and those created to access a perforated viscus accompanied by a high degree of contamination. (See Schwartz 10th ed., p. 147.)
The most appropriate treatment of a 4-cm hepatic abscess is
A. Antibiotic therapy alone
B. Aspiration for culture and antibiotic therapy
C. Percutaneous drainage and antibiotic therapy
D. Operative exploration, open drainage of the abscess, and antibiotic therapy
Hepatic abscesses are rare, currently accounting for approximately 15 per 100,000 hospital admissions in the United States. Pyogenic abscesses account for approximately 80% of cases, the remaining 20% being equally divided among parasitic and fungal forms. Formerly, pyogenic liver abscesses were caused by pylephlebitis due to neglected appendicitis or diverticulitis. Today, manipulation of the biliary tract to treat a variety of diseases has become a more common cause, although in nearly 50% of patients no cause is identified. The most common aerobic bacteria identified in recent series include E. coli, Klebsiella pneumoniae, and other enteric bacilli, enterococci, and Pseudomonas spp., while the most common anaerobic bacteria are Bacteroides spp., anaerobic streptococci, and Fusobacterium spp. Candida albicans and other similar yeasts cause the majority of fungal hepatic abscesses. Small (<1 cm), multiple abscesses should be sampled and treated with a 4- to 6-week course of antibiotics. Larger abscesses invariably are amenable to percutaneous drainage, with parameters for antibiotic therapy and drain removal similar to those mentioned above. Splenic abscesses are extremely rare and are treated in a similar fashion. Recurrent hepatic or splenic abscesses may require operative intervention—unroofing and marsupialization or splenectomy, respectively. (See Schwartz 10th ed., p. 150.)
Postoperative urinary tract infections (UTIs)
A. Are usually treated with a 7- to 10-day course of antibiotics.
B. Initial therapy should be directed by results of urine culture.
C. Are established by >104 CFU/mL of bacteria in urine culture in asymptomatic patients.
D. Can be reduced by irrigating indwelling Foley catheters daily.
The presence of a postoperative UTI should be considered based on urinalysis demonstrating WBCs or bacteria, a positive test for leukocyte esterase, or a combination of these elements. The diagnosis is established after >104 CFU/mL of microbes are identified by culture techniques in symptomatic patients, or >105 CFU/mL in asymptomatic individuals. Treatment for 3 to 5 days with a single antibiotic directed against the most common organisms (eg, E. Coli, K. pneumoniae) that achieves high levels in the urine is appropriate. Initial therapy is directed by Gram’s stain results and is refined as culture results become available. Postoperative surgical patients should have indwelling urinary catheters removed as quickly as possible, typically within 1 to 2 days, as long as they are mobile, to avoid the development of a UTI. (See Schwartz 10th ed., p. 152.)
The first step in the evaluation and treatment of a patient with an infected bug bite on the leg with cellulitis, bullae, thin grayish fluid draining from the wound, and pain out of proportion to the physical findings is
A. Obtain C-reactive protein
C. Magnetic resonance imaging (MRI) of the leg
The diagnosis of necrotizing infection is established solely upon a constellation of clinical findings, not all of which are present in every patient. Not surprisingly, patients often develop sepsis syndrome or septic shock without an obvious cause. The extremities, perineum, trunk, and torso are most commonly affected, in that order. Careful examination should be undertaken for an entry site such as a small break or sinus in the skin from which grayish, turbid semipurulent material (“dishwater pus”) can be expressed, as well as for the presence of skin changes (bronze hue or brawny induration), blebs, or crepitus. The patient often develops pain at the site of infection that appears to be out of proportion to any of the physical manifestations. Any of these findings mandates immediate surgical intervention, which should consist of exposure and direct visualization of potentially infected tissue (including deep soft tissue, fascia, and underlying muscle) and radical resection of affected areas. Radiologic studies should be undertaken only in patients in whom the diagnosis is not seriously considered, as they delay surgical intervention and frequently provide confusing information. Unfortunately, surgical extirpation of infected tissue frequently entails amputation and/or disfiguring procedures; however, incomplete procedures are associated with higher rates of morbidity and mortality. (See Schwartz 10th ed., p. 151.)
What is FALSE regarding intravascular catheter infections?
A. Selected low-virulence infections can be treated with a prolonged course of antibiotics.
B. In high-risk patients, prophylactic antibiotics infused through the catheter can reduce rate of catheter infections.
C. Bacteremia with gram-negative bacteria or fungi should prompt catheter removal.
D. Many patients with intravascular catheter infections are asymptomatic.
Many patients who develop intravascular catheter infections are asymptomatic, often exhibiting solely an elevation in the WBC count. Blood cultures obtained from a peripheral site and drawn through the catheter that reveal the presence of the same organism increase the index of suspicion for the presence of a catheter infection. Obvious purulence at the exit site of the skin tunnel, severe sepsis syndrome due to any type of organism when other potential causes have been excluded, or bacteremia due to gram-negative aerobes or fungi should lead to catheter removal. Selected catheter infections due to low-virulence microbes such as Staphylococcus epidermidis can be effectively treated in approximately 50 to 60% of patients with a 14- to 21-day course of an antibiotic, which should be considered when no other vascular access site exists. Use of systemic antibacterial or antifungal agents to prevent catheter infection is of no utility and is contraindicated. (See Schwartz 10th ed., p. 154.)
Patients with a penicillin allergy are LEAST likely to have a cross-reaction with
Allergy to antimicrobial agents must be considered prior to prescribing them. First, it is important to ascertain whether a patient has had any type of allergic reaction in association with administration of a particular antibiotic. However, one should take care to ensure that the purported reaction consists of true allergic symptoms and signs, such as urticaria, bronchospasm, or other similar manifestations, rather than indigestion or nausea. Penicillin allergy is quite common, the reported incidence ranging from 0.7 to 10%. Although avoiding the use of any beta-lactam drug is appropriate in patients who manifest significant allergic reactions to penicillins, the incidence of cross-reactivity appears low for all related agents, with 1% cross-reactivity for carbapenems, 5 to 7% cross-reactivity for cephalosporins, and extremely small or nonexistent cross-reactivity for monobactams. (See Schwartz 10th ed., p. 146.)
What is the estimated risk of transmission of human immunodeficiency virus (HIV) from a needlestick from a source with HIV-infected blood?
While alarming to contemplate, the risk of human immunodeficiency virus (HIV) transmission from patient to surgeon is low. As of May 2011, there had been six cases of surgeons with HIV seroconversion from a possible occupational exposure, with no new cases reported since 1999. Of the numbers of health care workers with likely occupationally acquired HIV infection (n = 200), surgeons were one of the lower risk groups (compared to nurses at 60 cases and nonsurgeon physicians at 19 cases). The estimated risk of transmission from a needlestick from a source with HIV-infected blood is estimated at 0.3%. (See Schwartz 10th ed., p. 156.)
Closure of an appendectomy wound in a patient with perforated appendicitis who is receiving appropriate antibiotics will result in a wound infection in what percentage of patients?
Surgical management of the wound is also a critical determinant of the propensity to develop an SSI. In healthy individuals, class I and II wounds may be closed primarily, while skin closure of class III and IV wounds is associated with high rates of incisional SSIs (~25–50%). The superficial aspects of these latter types of wounds should be packed open and allowed to heal by secondary intention, although selective use of delayed primary closure has been associated with a reduction in incisional SSI rates. It remains to be determined whether National Nosocomial Infections Surveillance (NNIS) system type stratification schemes can be employed prospectively in order to target specific subgroups of patients who will benefit from the use of prophylactic antibiotic and/or specific wound management techniques. One clear example based on cogent data from clinical trials is that class III wounds in healthy patients undergoing appendectomy for perforated or gangrenous appendicitis can be primarily closed as long as antibiotic therapy directed against aerobes and anaerobes is administered. This practice leads to SSI rates of approximately 3 to 4%. (See Schwartz 10th ed., p. 149.)
A chronic carrier state occurs with hepatitis C infection in what percentage of patients?
Hepatitis C virus (HCV), previously known as non-A, non-B hepatitis, is an RNA flavivirus first identified specifically in the late 1980s. This virus is confined to humans and chimpanzees. A chronic carrier state develops in 75 to 80% of patients with the infection, with chronic liver disease occurring in three-fourths of patients who develop chronic infection. The number of new infections per year has declined since the 1980s due to routine testing of blood donors for this virus. Fortunately, HCV is not transmitted efficiently through occupational exposures to blood, with the seroconversion rate after accidental needlestick approximately 1.8%. (See Schwartz 10th ed., p. 156.)
Possible exposure to anthrax should be initially treated with
Inhalational anthrax develops after a 1- to 6-day incubation period, with nonspecific symptoms including malaise, myalgia, and fever. Over a short period of time, these symptoms worsen, with development of respiratory distress, chest pain, and diaphoresis. Characteristic chest roentgenographic findings include a widened mediastinum and pleural effusions. A key aspect in establishing the diagnosis is eliciting an exposure history. Rapid antigen tests are currently under development for identification of this gram-positive rod. Postexposure prophylaxis consists of administration of either ciprofloxacin or doxycycline. If an isolate is demonstrated to be penicillin-sensitive, the patient should be switched to amoxicillin. Inhalational exposure followed by the development of symptoms is associated with a high mortality rate. Treatment options include combination therapy with ciprofloxacin, clindamycin, and rifampin; clindamycin added to blocks production of toxin, while rifampin penetrates into the central nervous system and intracellular locations. (See Schwartz 10th ed., p. 156.)
The most effective postexposure prophylaxis for a surgeon stuck with a needle while operating on an HIV-positive patient is
A. None (no effective treatment is known).
B. Two- or three-drug therapy started within hours of exposure.
C. Single drug therapy started within 24 hours of exposure.
D. Triple drug therapy started within 24 hours of exposure.
Postexposure prophylaxis for HIV has significantly decreased the risk of seroconversion for health care workers with occupational exposure to HIV. Steps to initiate postexposure prophylaxis should be initiated within hours rather than days for the most effective preventive therapy. Postexposure prophylaxis with a two- or three-drug regimen should be initiated for health care workers with significant exposure to patients with an HIV-positive status. If a patient’s HIV status is unknown, it may be advisable to begin postexposure prophylaxis while testing is carried out, particularly if the patient is at high risk for infection due to HIV (eg, intravenous narcotic use). Generally, postexposure prophylaxis is not warranted for exposure to sources with unknown status, such as deceased persons or needles from a sharps container. (See Schwartz 10th ed., p. 156.)
What is NOT an early goal in treatment of severe sepsis?
A. Mean arterial pressure >65 mm Hg
B. Central venous pressure 8 to 2 mm Hg
C. Urine output >0.5 cc/kg/h
D. Serum lactate <2 mmol/L
Patients presenting with severe sepsis should receive resuscitation fluids to achieve a central venous pressure target of 8 to 12 mm Hg, with a goal of mean arterial pressure of >65 mm Hg and urine output of >0.5 cc/kg/h. Delaying this resuscitative step for as little as 3 hours until arrival in the ICU has been shown to result in poor outcome. Typically this goal necessitates early placement of central venous catheter. (See Schwartz 10th ed., p. 154.)
A patient in the ICU has been on ventilator support for 3 weeks. He has new onset elevated WBC count, fever, and consolidation seen on chest X-ray. What is an appropriate next step?
A. Exchange endotracheal tube and change respiratory circuit.
B. Obtain bronchoalveolar lavage.
C. Start treatment with empiric penicillin G.
Prolonged mechanical ventilation is associated with nosocomial pneumonia. These patients present with more severe disease, are more likely to be infected with drug-resistant pathogens, and suffer increased mortality compared with patients who develop community-acquired pneumonia. The diagnosis of pneumonia is established by presence of a purulent sputum, elevated leukocyte count, fever, and new chest X-ray abnormalities such as consolidation. The presence of two of the clinical findings, plus chest X-ray findings, significantly increases the likelihood of pneumonia. Consideration should be given to performing bronchoalveolar lavage to obtain samples for Gram stain and culture. Some authors advocate quantitative cultures as a means to identify a threshold for diagnosis. Surgical patients should be weaned from mechanical ventilation as soon as feasible, based on oxygenation and inspiratory effort, as prolonged mechanical ventilation increases the risk of nosocomial pneumonia. (See Schwartz 10th ed., p. 153.)
Patients with severe, necrotizing pancreatitis should be treated with
A. No antibiotics unless CT-guided aspiration of the area yields positive cultures
B. Empiric cefoxitin or cefotetan
C. Empiric cefuroxime plus gentamicin
D. Empiric carbapenems or fluoroquinolones
Current care of patients with severe acute pancreatitis includes staging with dynamic, contrast-enhanced helical CT scan with 3-mm tomographs to determine the extent of pancreatic necrosis, coupled with the use of one of several prognostic scoring systems. Patients who exhibit significant pancreatic necrosis should be carefully monitored in the ICU and undergo follow-up CT examination. The weight of current evidence also favors administration of empiric antibiotic therapy to reduce the incidence and severity of secondary pancreatic infection, which typically occurs several weeks after the initial episode of pancreatitis. Several randomized, prospective trials have demonstrated a decrease in the rate of infection and mortality using agents such as carbapenems or fluoroquinolones that achieve high pancreatic tissue levels. (See Schwartz 10th ed., p. 150.)
A patient with a localized wound infection after surgery should be treated with
A. Antibiotics and warm soaks to the wound
C. Antibiotics and opening the wound
D. Incision and drainage alone
Effective therapy for incisional SSIs consists solely of incision and drainage without the addition of antibiotics. Antibiotic therapy is reserved for patients in whom evidence of severe cellulitis is present, or who manifest concurrent sepsis syndrome. The open wound often is allowed to heal by secondary intention, with dressings being changed twice a day. The use of topical antibiotics and antiseptics, to further wound healing, remains unproven, although anecdotal studies indicate their potential utility in complex wounds that do not heal with routine measures. (See Schwartz 10th ed., p. 149.)
Which areas likely do NOT contain resident microorganisms?
The urogenital, biliary, pancreatic ductal, and distal respiratory tracts do not possess resident microflora in healthy individuals, although microbes may be present if these barriers are affected by disease (eg, malignancy, inflammation, calculi, or foreign body), or if microorganisms are introduced from an external source (eg, urinary catheter or pulmonary aspiration). In contrast, significant numbers of microbes are encountered in many portions of the gastrointestinal tract, with vast numbers being found within the oropharynx and distal colorectum, although the specific organisms differ. (See Schwartz 10th ed., p. 137.)