surgical infections rush Flashcards
On the eighth day after an exploratory laparotomy and bowel
resection complicated by intraabdominal hypertension, a
65-year-old female who remains intubated in the intensive
care unit (ICU) develops a fever of 102°F. An infectious
workup reveals a new right lower lobe consolidation. When
initiating antibiotic therapy for presumed ventilator-associated pneumonia (VAP), which of the following does not treat
Pseudomonas aeruginosa?
A. Cefepime
B. Unasyn (ampicillin/sulbactam)
C. Ticarcillin
D. Aztreonam
E. Ciprofloxacin
ANSWER: B
COMMENTS: P. aeruginosa is a gram-negative bacillus commonly
implicated in VAP. Antipseudomonal antibiotics should be initiated
empirically in any patient with VAP prior to isolation of the organism
on culture due to the high mortality associated with pseudomonal
infection. Antipseudomonal penicillins include ticarcillin and piperacillin. Third- and fourth-generation cephalosporins, such as ceftazidime and cefepime, are effective against P. aeruginosa and have a
relatively narrow range of activity, making them preferred agents in
susceptible isolates. Monobactams (like aztreonam) and carbapenems (meropenem, imipenem) are effective, but have a very broad
spectrum of activity, and should be deescalated once susceptibilities
are available. Fluoroquinolones are also effective. The polymyxin
colistin is also effective, but has an extensive toxicity profile, and
should be used cautiously with multiresistant organisms
A 67-year-old male remains in the hospital 1 week after
undergoing a pancreaticoduodenectomy. He has two intraabdominal closed-suction drains in place, as well as a left internal
jugular triple lumen catheter; his Foley catheter was removed on
the third postoperative day. On the seventh postoperative day, he
becomes febrile to 101.5°F, and a fever workup reveals a growth
of Enterococcus in two of two peripheral blood cultures. Which
of the following is true regarding the diagnosis of a central
line–associated bloodstream infection (CLABSI)?
A. It is preferential to begin empiric antimicrobial therapy
prior to obtaining cultures.
B. Catheter-site exudate, if present, should not be cultured
when there is concern for a line-related bloodstream
infection.
C. The subcutaneous portion of the central venous catheter
should be cultured, rather than the tip.
D. Paired blood samples (one from the catheter and one
from a peripheral vein, or alternatively from greater than
two lumens of the same central venous catheter) growing
the same organism at levels that meet catheter-related
bloodstream infection criteria are required to diagnose a
CLABSI.
E. Growth of greater than 10 colony-forming units (cfu) by
semiquantitative (roll-plate) culture confirms catheter
colonization.
ANSWER: D
COMMENTS: See Question 3.
Ref.: See Question 3
3. Which of the following is true regarding the treatment of
catheter-related bloodstream infections?
A. All catheters in cases of confirmed CLABSI should be
removed; it is never appropriate to attempt to salvage the
infected catheter.
B. Empiric coverage of Candida should be initiated in bone
marrow or solid organ transplant patients with presumed
CLABSI.
C. Empiric antibiotic therapy should include methicillinresistant Staphylococcus aureus (MRSA) coverage as
well as gram-negative rod (GNR) coverage, regardless of
the severity of illness.
D. Duration of antibiotic therapy in CLABSIs is timed from
the day when empiric antibiotics were initiated.
E. The location of a temporary central venous catheter
(subclavian versus internal jugular versus femoral) has no
influence on the empiric antibiotic agents that should be
used
ANSWER: B
COMMENTS: Central venous catheters are commonly used in
many settings in modern health care, but their use is associated with
the risk of bloodstream infections, known as CLABSIs. These
infections are known to increase morbidity, mortality, and health
care costs.
To diagnose a CLABSI, growth of greater than 15 cfu by
semiquantitative (roll-plate) culture from at least two samples is
required; these two samples may be obtained from the catheter and
a peripheral vein or, alternatively, from at least two lumens from
the same central venous catheter. The diagnosis of CLABSI is best
defined by a colony count threefold greater than that obtained from
a peripheral vein. Skin and catheter hubs should be prepared with
alcohol, tincture of iodine, or alcohol-based chlorhexidine (>0.5%)
with adequate drying time, prior to obtaining cultures; cultures
should be obtained by trained phlebotomists if possible.
Management of CLABSI varies based on the organism cultured and the severity of illness, but for all CLABSIs, the duration
of antimicrobial therapy is determined on the first day of obtaining
negative blood cultures. Preferably, adequate cultures are obtained
prior to the initiation of antibiotic therapy. Empiric therapy in
uncomplicated cases [i.e., cases without evidence of severe sepsis,
endocarditis or osteomyelitis (OM), or without evidence of infection of the catheter tunnel or adjacent abscess] should begin with
antibiotics that cover gram-positive cocci. Vancomycin or daptomycin for empiric therapy should be reserved for areas with a high
prevalence of MRSA. Empiric GNR coverage should be added in
cases of severe sepsis, neutropenia, in patients with known colonization with a GNR organism, or in patients with femoral catheters.
Empiric coverage for Candida, either with an echinocandin or a
fluconazole, should be initiated in patients with severe sepsis plus
prolonged broad-spectrum antibiotic use, total parenteral nutrition,
hematologic malignancy or receipt of solid organ or bone marrow
transplants, or known Candida colonization. In most circumstances,
the infected catheter should be removed; however, there are certain
instances in which salvage of the catheter may be attempted. Antibiotic locks (antibiotic solutions that are instilled into the catheter
itself) can be used in conjunction with systemic antimicrobial
therapy, particularly in patients in whom catheters are difficult to
remove or replace (i.e., tunneled hemodialysis catheters or ports for
parenteral nutrition in short gut syndrome). If patients have persistent positive blood cultures after salvage attempt, the catheter
should be removed
A 78-year-old man with a history of urinary retention and a
chronic indwelling urinary catheter is admitted to the hospital
from his nursing home with a new-onset altered mental status,
and a catheter-associated urinary tract infection (CAUTI) is
suspected. Which of the following is true regarding CAUTIs?
A. A 7-day antibiotic treatment is adequate for patients
whose symptoms respond promptly to treatment.
B. A CAUTI can be sufficiently diagnosed by the presence
of greater than 105 cfu/mL of at least one bacterial
species in a urine specimen.
C. Urine specimens being sent for culture can be obtained
from the catheter bag.
D. Pyuria is a specific indicator for urinary tract infections
(UTIs).
E. Proteus mirabilis is the most common organism cultured
in CAUTIs.
ANSWER: A
COMMENTS: CAUTIs are the most common health care–associated infection worldwide, and the most important factor leading to
nosocomial UTIs is urinary catheterization. The best prevention for
CAUTIs is avoiding catheterization. There are a limited number of
circumstances in which catheterization is appropriate, such as when
monitoring urine output in critically ill patients, in patients with
acute urinary retention or obstruction, in certain surgical procedures, or to facilitate healing of wounds or pressure ulcers in some
patients with urinary incontinence. A CAUTI is diagnosed by the
presence of greater than 103 cfu/mL of at least one bacterial species
in a catheter urine specimen or a midstream-voided urine specimen
in addition to clinical signs and symptoms suggestive of infection.
Signs and symptoms of a UTI include new-onset fever, rigors,
altered mental status, lethargy, malaise, flank pain, costovertebral
angle tenderness, hematuria, suprapubic or pelvic discomfort,
dysuria, urinary frequency, and urinary urgency. For these symptoms to be attributed to a catheter, the patient must have a current
indwelling urinary catheter or have had one within the 48 h preceding his or her symptoms. Without these symptoms, an infection
cannot be diagnosed. Catheter-associated asymptomatic bacteriuria
is more likely, and this is diagnosed by the presence of greater than
105 cfu/mL of at least one bacterial species in a urine specimen.
Catheters predispose to bacteriuria and UTIs in a variety of ways,
but formation of a biofilm along the catheter itself is the most
important predisposing factor. Pyuria is not specific for UTIs; it
can be seen in a variety of other renal pathologies and should not
be used as a diagnostic criterion for UTI. Urine culture specimens
are best collected by removing the catheter, if possible, to obtain a
voided midstream specimen, from the tubing or catheter itself in a
catheter that has been in place for less than 2 weeks, or by removing
any catheter that has been in place for greater than 2 weeks and
obtaining a specimen from the new catheter. The duration of antibiotic therapy should be 7 days for patients whose symptoms
respond promptly to antibiotics and 10 to 14 days for those whose
symptoms respond slowly. Escherichia coli is the most common
causative organism in CAUTIs, although Proteus is commonly
cultured in patients with chronic indwelling catheters.
A 57-year-old Asian American female presents to her
hepatologist’s office for monitoring of her known chronic
hepatitis B infection. Which of the following sets of test
results is consistent with chronic active hepatitis B infection?
A. Hepatitis B surface antigen (HBsAg)+ less than 6
months, hepatitis B surface antibody (HBsAb)−,
immunoglobulin M (IgM) anti-HBc+, elevated aspartate
transaminase (AST), and alanine transaminase (ALT)
B. HBsAg+ greater than 6 months, HBsAb−, HBcAb+,
hepatitis B virus (HBV) DNA > 20,000 IU/mL, mildly
elevated AST and ALT
C. HBsAg+ greater than 6 months, hepatitis B e antigen
(HBeAg)−, HBV DNA < 2000 IU/mL, normal AST and
ALT
D. HBsAg−, HBsAb+, HBcAb+, normal AST and ALT
E. HBsAg−, HBsAb+, HBcAb−, normal AST and ALT
ANSWER: B
COMMENTS: Answer A is acute hepatitis B infection; chronic
infection requires HBsAg positivity for at least 6 months. A patient 58 SECTION I / Surgical Fundamentals
with chronic active infection (answer B) exhibits normal to mildly
elevated liver enzymes and HBsAg positivity but negative HBsAb
since the infection has not been cleared; HBcAb will be positive
with chronic infection, and HBeAg may be positive as well if there
is a continued high level of viral replication; this is usually accompanied by a high level of HBV DNA. This is different from an
inactive carrier state (answer C); these patients have persistent
HBV infection of the liver without significant hepatic necrosis or
inflammation, so their liver enzymes are not significantly elevated;
there is a low level of viral replication, which correlates with negative HBeAg. Patients who have cleared HBV infection have evidence of HBsAb and HBcAb positivity (answer D). Answer E
reflects successful vaccination, with only HBsAb positivity on
serologic testing
Match the antibiotic and its classical toxicity profile. A. Vancomycin a. Tendinopathy B. Aminoglycosides b. Red man syndrome C. Isoniazid (INH) c. Phototoxicity D. Fluoroquinolones d. Hepatitis E. Tetracycline e. Ototoxicity
ANSWER: A- b , B- e , C- d , D- a ,
E - c
COMMENTS: Vancomycin is known to cause red man syndrome,
a syndrome composed of flushing of the face, neck, and chest. It is
better described as a hypersensitivity reaction, rather than a true
allergy, because the effect is partly mediated by the speed with
which it is transfused. Aminoglycosides can cause ototoxicity
(cochlear and vestibular), which is dose dependent. The effects may
begin to be seen even after cessation of the drug; aminoglycoside
ototoxicity may be irreversible. INH can cause severe, sometimes
fulminant, hepatitis that is largely indistinguishable from acute viral
hepatitis. The mechanism of toxicity is not clear, but is thought to
be related to direct toxicity of the drug or its metabolites, and is
more likely to occur when other hepatitis risk factors are present,
such as concurrent alcohol consumption, use of other drugs that
utilize the cytochrome P450 system for metabolism, previous INH
intolerance, or prior or concurrent liver disease. Fluoroquinoloneinduced tendinopathy is rare, but it has been documented with
almost all drugs in this class. Tetracyclines cause cutaneous phototoxicity, so patients taking tetracyclines are cautioned to avoid sun
exposure
Which of the following is not a Surgical Care Improvement
Project (SCIP) measure for infection prevention in surgical
patients?
A. The optimal timing for administration of prophylactic
antibiotics is within 1 h of surgical incision.
B. Prophylactic antibiotics should be discontinued within
24 h of the end of surgery; in cardiac surgery, this is
lengthened to 48 h.
C. Clippers are preferred to razors for preoperative hair
removal, if necessary.
D. Goal blood glucose in the first 48 h following surgery is
less than 160 mg/dL.
E. Patients should remain normothermic within the first hour
following surgery
ANSWER: D
COMMENTS: The SCIP summarizes specific tactics aimed at
prevention of surgical site infections (SSIs). Of the answer choices
listed above, only D is inaccurate; optimal blood glucose within the
first 48 h of surgery is less than 200 mg/dL. Hyperglycemia impairs
the host immune function and is known to increase the risk of
infection in both diabetic and nondiabetic patients. Moderate hyperglycemia (i.e., blood glucose > 200 mg/dL) in the first 24 h following surgery increases the risk of SSIs by a factor of four. Tight
blood glucose control has been a matter of debate in recent years,
with some arguing that very strict blood glucose control (i.e., less
than 110 mg/dL) results in significantly decreased rates of infection. However, postoperative hypoglycemia is associated with
increased mortality, so glycemic goals have been relaxed.
The remaining answer choices are correct. Prophylactic antibiotics should be given within 1 h of incision, though 2 h is appropriate
for fluoroquinolones and vancomycin, due to the prolonged infusion
times for these drugs. They should be discontinued within 24 h of
the end of surgery in all cases aside from the cardiac surgery, where
48 h of prophylactic antibiotic therapy is appropriate. Razors should
never be used to remove hair prior to procedures due to the increased
risk for small breaks in the skin, which might introduce infection;
clippers should be used preoperatively. Normothermia, defined as
any temperature between 96.8°F and 100.4°F, should be maintained
intraoperatively and for at least the first hour following surgery
Match the surgical procedure with the most appropriate
preoperative prophylactic antibiotic.
A. Elective laparoscopic cholecystectomy a. Ertapenem
B. Femoral to popliteal arterial bypass with graft b. Clindamycin
C. Cystoscopy with ureteral stent placement c. None
D. Right hemicolectomy d. Cefazolin
E. Parotidectomy e. Ciprofloxacin
ANSWER: A- c , B- d , C- e , D- a ,
E - b
COMMENTS: Prophylactic antibiotics administered preoperatively
should be targeted to the organisms most likely to be encountered in
the operative field. Broad-spectrum antibiotics do not have greater
efficacy at preventing SSIs than more narrow-spectrum, targeted
choices. The choice of prophylactic antibiotic therapy for intraabdominal surgeries varies widely depending on the exact location within the
gastrointestinal tract that is being manipulated. Low-risk biliary tract
procedures (e.g., elective laparoscopic cholecystectomy) do not require
surgical site infection prophylaxis; however, patients undergoing open
or complicated procedures involving the biliary tract should receive
antibiotics covering enteric GNRs, Enterococcus, and Clostridia.
Comparatively, colorectal surgery requires broad coverage of enteric
GNRs, anaerobes, and Enterococcus, which may be accomplished
with ertapenem, a carbapenem antibiotic. Cystoscopy with manipulation, such as the placement of ureteral stents, necessitates coverage of
enteric GNRs and Enterococcus; compared with colorectal surgery,
anaerobic coverage is not necessary. Vascular SSIs are most commonly
caused by skin flora, such as Staphylococcus and Streptococcus
species, so a first-generation cephalosporin, such as cefazolin, is adequate. In clean-contaminated head and neck cases (i.e., any surgical
procedure involving the oropharyngeal mucosa), prophylactic antibiotics should cover both aerobic and anaerobic oral flora (such as Streptococcus, Bacteroides, and Peptostreptococcus).
A 68-year-old female has been admitted to the emergency
room with recurrent Clostridium difficile colitis. Her first
episode of C. difficile colitis was 3 months prior after
receiving clindamycin for a mild episode of cellulitis. Two
months ago, she had a second episode, treated again with full
symptom resolution. On examination, her vital signs are
normal and her abdomen is benign, with only mildly tender
to deep palpation in the right lower quadrant. Laboratory
results are notable for a leukocytosis of 13.4,000 cells per
MCL with 86% neutrophils, mild hypokalemia, and positive
C. difficile stool antigen. An abdominal film shows a colon of
normal caliber. What is the most appropriate treatment for
this patient?
A. Oral metronidazole 500 mg every 8 h for 10 to 14 days
B. Intravenous (IV) metronidazole 500 mg every 8 h for 10
to 14 days
C. Oral vancomycin 125 mg every 6 h for 10 to 14 days
D. Oral vancomycin, in a tapered and pulsed fashion over
approximately 5 to 7 weeks
E. IV vancomycin 125 mg every 6 h for 10 to 14 days
ANSWER: D
COMMENTS: See Question 11.
Ref.: See Question 11
10. The patient in the question above is admitted and started on
antibiotics, but her condition continues to deteriorate
clinically over the next 2 days despite appropriate antibiotic
therapy, probiotics, and supportive treatment. Her white
blood cell (WBC) count continues to rise to 17.8 and
creatinine increases to 1.5 from baseline of 0.8. She has a
low-grade fever and marginal urine output, and her abdomen
becomes distended, tympanic, and tender. An abdominal
obstructive series shows dilation of the entire colon to 10 cm
in diameter without evidence of pneumoperitoneum. Which
of the following is not an acceptable course of action in
treating severe C. difficile colitis?
A. Transitioning from pulsed to standard scheduled oral
vancomycin 125 mg every 6 h with the addition of IV
metronidazole 500 mg every 8 h
B. Transitioning from pulsed to standard scheduled oral
vancomycin 125 mg every 6 h with the addition of oral
fidaxomicin 200 mg every 12 h
C. Subtotal colectomy
D. Diverting loop ileostomy with colonic lavage
E. Metronidazole enemas
ANSWER: E
COMMENTS: See Question 11.
Ref.: See Question 11
11. Which of the following is true regarding the pathophysiology
of C. difficile infection?
A. Antimicrobial agents with activity against C. difficile are
equally as likely to result in C. difficile colitis as those
without activity against C. difficile.
B. A patient’s inability to produce antibody to toxin A is a
significant predictor of recurrent C. difficile infection.
C. Advanced age is not considered a risk factor for development of clinical C. difficile infection.
D. Studies have suggested that gastric acid suppression [i.e.,
use of proton pump inhibitors (PPIs) or H2 blockers] may
be protective against the development of C. difficile
infection.
E. Alcohol-based hand sanitizers are effective in removing
C. difficile spores after contact with an infected patient.
ANSWER: B
Recurrent C. difficile colitis is a
growing health problem in the United States. Treatment of an initial
episode can be accomplished with oral or IV metronidazole (500 mg
every 8 h for 10 to 14 days) or oral vancomycin (125 mg every 6 h
for 10 to 14 days). IV vancomycin is never acceptable as a treatment
for C. difficile colitis. More severe initial infections should be treated
with vancomycin rather than metronidazole. For a patient’s first
relapse, if there is no evidence of systemic toxicity, treatment with
the initial antibiotic regimen may be appropriate. Second relapses
and beyond, however, require oral vancomycin in a tapered and
pulsed fashion (see the following chart). Alternatively, fidaxomicin,
a macrolytic antibiotic that is bactericidal against C. difficile, can be
used. With both drugs, probiotics may be added, though their efficacy
is still unclear. Fecal microbiota transplant has also been shown to
be a cost-effective solution for recurrent C. difficile colitis.
For patients developing evidence of systemic toxicity from C.
difficile colitis, more aggressive therapy is required. Depending on
the patient’s clinical stability, multiple avenues of treatment are
available. Scheduled oral vancomycin or fidaxomicin can be given,
with or without IV metronidazole; IV metronidazole may have
enhanced efficacy in patients with evidence of bowel dysmotility.
The duration of antibiotics in severe C. difficile colitis is generally
at least 17 to 24 days (1 week beyond standard treatment). Intracolonic vancomycin administration (i.e., vancomycin enema) is
also an acceptable treatment method; metronidazole enema is not
an accepted treatment, which makes answer E incorrect. Vancomycin enemas are particularly useful in patients who have conditions
preventing oral vancomycin from reaching the colon (i.e., end
ileostomies, severe ileus, colonic dysmotility, etc.). Patients who
are severely ill with toxic megacolon, perforation, uncontrolled
sepsis, or multiorgan failure should be considered operative candidates. The two most accepted surgical procedures are subtotal colectomy and diverting loop ileostomy with colonic lavage followed
by antegrade vancomycin enemas.
The pathogenesis of C. difficile infection rests largely on the
disruption of normal colonic flora by other antibiotics. Those with
inherent activity against C. difficile (i.e., those who have a robust
antibody response to toxin A) are less likely to become clinically
infected. One study reported that patients who did not develop antibodies to toxin A during their initial infection were 48 times as likely
to develop a recurrent infection. Advanced age (>65 years) is predictive of both initial and recurrent infection. Additional patient-specific
risk factors for infection include gastric acid suppression (either via
PPIs or H2 blockers), recent gastrointestinal surgery, chemotherapy,
stem cell transplant, and obesity. The three classes of antibiotics cited
most frequently as causative agents are clindamycin, cephalosporins,
and fluoroquinolones, and these agents are generally administered
weeks to several months prior to the development of C. difficile
infection. Concomitant use of multiple antibiotics and prolonged
courses of antibiotics have also been found to be risk factors for
infection; however, not all patients who are exposed to C. difficile
and receive antibiotics develop an infection.
Infection control policies are paramount to controlling the
nosocomial spread of C. difficile infection; patients with active
infections should be placed on contact precautions, and all health 60 SECTION I / Surgical Fundamentals
care workers (HCWs) who encounter the patient should wash their
hands with soap and water since C. difficile spores are resistant to
alcohol-based hand sanitizers
Which of the following is true regarding postoperative fever?
A. Urinalysis, urine culture, and chest x-ray must be
obtained as part of a complete fever workup in postoperative patients within 72 h of operation.
B. In a febrile postoperative patient, wound cultures should
be obtained regardless of the appearance of the wound.
C. Wound infections in the first 24 to 48 h are uncommon
but, if present, are worrisome for group A streptococcal
or clostridial infection.
D. Fevers persisting for greater than 96 h postoperatively are
expected in cases of diffuse intraabdominal infection,
such as feculent peritonitis from diverticulitis, even with
appropriate surgical management.
E. All of the above.
ANSWER: C
COMMENTS: Fever is a common postsurgical finding, but not all
fevers require evaluation. In the first 72 h after surgery, fever is
more likely related to postoperative inflammatory responses in the
host, rather than infection, when the patient is otherwise asymptomatic or without an indwelling urinary catheter. While fever is
expected in postoperative patients with evidence of diffuse infection preoperatively (such as large abscesses, purulent or feculent
peritonitis, or necrotizing soft tissue infection), fevers that are persistent for greater than 96 h after appropriate surgical management,
or recurrent fevers after 96 h, are concerning for recurrent or incompletely cleared infection. Fevers presenting greater than 96 h postoperatively are more likely to be due to infection. Surgical wounds
should only be cultured if there are signs or symptoms suggestive
of wound infection (i.e., purulence, tenderness, and erythema). SSIs
are most commonly due to the native flora of the organ that was
operated upon, but within the first 24 to 48 h of surgery, wound
infections are more likely to be due to group A Streptococcus
(GAS) or Clostridia, which are significantly more virulent organisms. Deep venous thrombosis, pulmonary embolism, and superficial thrombophlebitis are other possible etiologies that should be
considered in the evaluation of a febrile postoperative patient.
A 25-year-old male remains nasotracheally intubated in the ICU
while undergoing repeated debridements for Ludwig’s angina.
His infection appears to be adequately drained, although he still
has persistent facial swelling. Sinusitis is expected. Which of the
following is true regarding sinusitis in critically ill patients?
A. The most important risk factor for sinusitis in critically ill
patients is a history of MRSA of the nares.
B. Few sinus infections are polymicrobial; often, only one
organism is isolated in culture.
C. The most commonly isolated organism in sinusitis
cultures is coagulase-negative S. aureus.
D. Computed tomography (CT) scan of the sinuses is the
most sensitive diagnostic imaging modality for sinusitis.
E. Incidence of acute sinusitis in nasotracheally intubated
patients is approximately 75% after 1 week.
ANSWER:
COMMENTS: Sinusitis is an infrequent but potentially life-threatening cause of fever in critically ill patients. When the ostia of the
sinuses become obstructed (e.g., from nasotracheal intubation,
nasogastric tube placement, or maxillofacial trauma), bacterial
overgrowth can occur, and when drainage is impaired, infection
results; approximately one-third of patients who are nasotracheally
intubated develop sinusitis within 1 week. The diagnosis is suggested by clinical findings, including cough, purulent nasal discharge, tooth pain, fever, wheezing, or throat or tooth pain. Normal
nasopharyngeal organisms are the most common causes, and infections are often polymicrobial. GNRs are present in approximately
two-third of cases of acute sinusitis in critically ill patients; grampositive rods are isolated in approximately one-third of cases, and
fungi are found in 5%–10%. A CT scan of the sinuses is the most
sensitive imaging modality for diagnosing sinusitis, although plain
films can be obtained as well. Plain films are less sensitive than CT
scan, but the accuracy of plain films in diagnosis can be augmented
if combined with the findings of nasal endoscopy, when performed
by a skilled endoscopist. Needle aspiration of the sinuses to obtain
fluid for cultures provides a definitive diagnosis, but a biopsy may
be required to rule out invasive fungal sinusitis in immunocompromised patients.
A 24-year-old male presents to the emergency department
after sustaining a puncture wound to his left foot 60 min
prior to presentation. On examination, he has a small metal
nail protruding from the plantar aspect of his left foot, with
moderate surrounding erythema and a small amount of
bleeding, but no significant purulence. He is unsure of his
tetanus vaccination status. How should the issue of potential
tetanus infection be addressed in this patient?
A. Local wound care only
B. Local wound care, IV metronidazole or penicillin for 7 to
10 days
C. Local wound care, IV metronidazole or penicillin for 7 to
10 days, tetanus toxoid
D. Local wound care, IV metronidazole or penicillin for 7 to
10 days, tetanus toxoid, tetanus immunoglobulin
E. No treatment
ANSWER: D
COMMENTS: See Question 15.
Ref.: See Question 15
15. Which of the following is true regarding tetanus infection?
A. Tetanus is caused by tetanus toxin, which is produced by
C. tetani, an aerobic gram-positive bacillus.
B. Tetanus infection has purely motor neuron effects.
C. Tetanus-prone wounds include contaminated wounds (i.e.,
soil, saliva, and stool), crush wounds, or burn wounds.CHAPTER 5 / Surgical Infection and Transmissible Diseases and Surgeons 61
D. Tetanus immunoglobulin is indicated in any patient with
an unknown tetanus vaccination history.
E. None of the above
ANSWER: C
COMMENTS: Tetanus toxin, produced by C. tetani, an anaerobic gram-positive bacillus, causes disinhibition of lower motor
neurons; it is taken up via lower motor neurons and transported
proximally to the spinal cord and brainstem and then into inhibitory neurons, causing a functional denervation of motor neurons.
This can result in lockjaw; muscle rigidity; and spasm of respiratory, laryngeal, and abdominal muscles, causing respiratory
failure. Autonomic dysfunction can also be seen with tetanus,
manifesting as labile blood pressure and heart rate. Tetanusprone wounds include contaminated wounds (i.e., soil, saliva,
and stool), crush wounds, or burn wounds. Treatment of tetanusprone wounds includes local wound care (i.e., debridement and
irrigation) and antibiotic therapy targeted against C. tetani.
Depending on the completeness of a patient’s tetanus vaccination, additional therapy is required, based on the following
tables:
Tetanus-Prone Wounds
Previous Tetanus
Toxoid
Administration Tetanus Toxoid
Tetanus
Immunoglobulin
Less than three doses Yes Yes
Three or more doses No; yes, if the last
dose was prior to
more than 5 years
No
Clean Wounds
Previous Tetanus
Toxoid
Administration Tetanus Toxoid
Tetanus
Immunoglobulin
Less than three doses Yes No
Three or more doses No; yes, if the last
dose was prior to
more than 10 years
No
Tetanus immunoglobulin serves to bind tetanus toxin in the
bloodstream to minimize absorption into motor neurons. Muscle
spasm and rigidity should be treated if present
A 62-year-old man with a history of chronic pancreatitis from
alcohol abuse presents to the emergency department with
complaints of fevers and abdominal pain. On examination, he
is febrile to 100.8°F. He is jaundiced and has right upper
quadrant tenderness. His liver enzymes are elevated with a
new leukocytosis. A CT scan of the abdomen demonstrates
cirrhotic liver morphology, calcifications along the pancreas,
and a rim-enhancing hypoechoic liver lesion. Which of the
following is true regarding the diagnosis of a pyogenic liver
abscess (PLA)?
A. Most PLAs are found in the left hepatic lobe.
B. The most common etiology of PLAs is seeding from
another intraabdominal infection via the portal vein.
C. Most PLAs are polymicrobial, and in the United States,
E. coli is the most commonly isolated organism.
D. Percutaneous drainage is recommended for all PLAs if
the drainage is technically feasible.
E. The classic triad of fever, right upper quadrant pain, and
malaise is present in many patients with PLAs.
ANSWER: C
COMMENTS: PLAs are relatively uncommon and have vague
presenting symptoms. The classic triad of fever, right upper quadrant pain, and malaise is present in only about one-third of patients.
PLAs have multiple causes including biliary tract disease causing
obstruction, seeding from another intraabdominal infection via the
portal vein, hepatic artery seeding or bacteremia, direct extension
from an adjacent infection (such as cholecystitis and perinephric
abscess), or trauma; a small percentage of cases are cryptogenic.
Biliary tract disease is now the most common etiology of PLAs and
includes cases of choledocholithiasis, biliary stricture, congenital
anomalies of the biliary tree such as choledochal cysts, and obstructing tumors like cholangiocarcinoma or pancreatic adenocarcinoma.
Most infections are polymicrobial, and E. coli is the most frequently isolated organism in the United States, followed by Klebsiella pneumoniae. PLAs occur most frequently in the right lobe of
the liver, given its greater portal venous flow. Treatment involves
broad-spectrum antibiotics (though particularly targeted against
enteric GNRs and anaerobes) with percutaneous drainage for
patients who do not improve with 2 to 3 days of appropriate antimicrobial therapy, abscesses greater than 5 cm in diameter, or
abscesses at risk of rupture. Surgical intervention is generally
reserved for ruptured abscesses, failed response to percutaneous
drainage, uncorrected primary pathology (e.g., biliary stricture), or
multiloculated abscesses not amenable to percutaneous drainage.
A 47-year-old man has been admitted to the burn ICU for 4
days after sustaining a 30% total body surface area (TBSA)
burn, involving the neck, chest, bilateral upper extremities,
and lower extremities, when he begins to clinically decompensate. Which of the following is suggestive or diagnostic
of a burn wound sepsis?
A. Conversion of a partial-thickness burn to a full-thickness
burn
B. Fevers greater than 100.4°F
C. Burn wound culture swab growing greater than 105
organisms per gram of tissue swabbed
D. Inability to tolerate enteral tube feeds for greater than
24 h
E. Failure to improve with broad-spectrum antibiotic
administration
ANSWER: A
COMMENTS: Burn wound infections remain a major cause of
morbidity and mortality in burn patients, especially in those with
greater than 20% TBSA burns. Burn wounds have a greater propensity for infection than the healthy tissue since the wound lacks
a barrier to environmental organisms, and devascularized burn
tissue provides a protein-rich medium in which bacteria can thrive;
in addition, burns cause significant systemic responses that inhibit
a patient’s normal host defense and healing mechanisms. Most
burns are colonized with bacteria early after injury but do not cause
systemic symptoms. Topical antimicrobials help to reduce the rate
of conversion into invasive wound infections; however, invasive 62 SECTION I / Surgical Fundamentals
infections do result in systemic symptoms and must be treated.
Diagnosis of a burn wound infection requires positive histopathology: the burn must be biopsied, with the growth of >105 organisms
per gram of burn wound tissue. Burn wound infections often manifest with physical changes in the appearance of the burn, such as
conversion to a greater degree of burn and surrounding cellulitis.
Because most burn patients exhibit the signs of a systemic inflammatory response syndrome (SIRS), the American Burn Association
has developed criteria for specifically diagnosing burn wound
sepsis:
• At least one of the following:
• Culture-positive infection (i.e., blood, urine, wound)
• Pathologic tissue source identified (>105 bacteria per gram
of tissue on quantitative biopsy)
• Clinical improvement with antimicrobial therapy
• At least three of the following:
• Temperature greater than 102.2°F or less than 97.7°F
• Progressive tachycardia
• Progressive tachypnea
• Thrombocytopenia that occurs greater than 3 days after
initial resuscitation
• Refractory hypotension
• Leukocytosis > 12,000 or <4000 WBCs/cells MCL
• Hyperglycemia
• Inability to tolerate enteral feedings for >24 h
. Which of the following is not a classical clinical manifestation of GAS infection? A. Necrotizing soft tissue infection B. Acute rheumatic fever C. Toxic shock syndrome D. Pharyngitis E. Meningitis
ANSWER: E
COMMENTS: GAS, or group A S. pyogenes, is an aerobic
gram-positive coccus that is responsible for a wide range of clinical illnesses, accounting for greater than 600 million infections
globally each year. The infections caused by GAS vary in clinical
severity, from mild cellulitis to life-threatening toxic shock syndrome, as demonstrated by the answer choices above. GAS is
also responsible for a variety of postinfectious immune-mediated
diseases, such as acute rheumatic fever or poststreptococcal glomerulonephritis. All the answer choices above can be classically
attributed to GAS infection except for meningitis, which is more
commonly caused by group B Streptococcus, particularly in
newborns.
GAS, which colonizes epithelial surfaces, is almost universally sensitive to penicillin. Its main virulence factor is the M
protein, which is a surface antigen and virulence factor encoded by
the emm gene, of which there are over 200 types. Different emm
types are associated with different types of infection; some are
known to cause cutaneous infection, while others cause invasive
infection. The prevalence of different emm types is also socioeconomically distinct, with certain emm types being seen in more
industrialized areas compared with other types being prevalent in
more rural communities. Geography plays a role as well, with variability in the prevalence of emm types based on region.
A 45-year-old man who underwent a splenectomy for
immune thrombocytopenic purpura develops a fever. Which
of the following is true regarding postsplenectomy sepsis?
A. A fever without other localizing symptoms of infection
(such as cough and diarrhea) is usually not worrisome in
postsplenectomy patients.
B. Postsplenectomy sepsis is almost never seen in patients
who complete the appropriate vaccinations.
C. The most common organism implicated in postsplenectomy sepsis is Haemophilus influenzae.
D. Initiation of empiric antibiotics should be delayed until
cultures are obtained.
E. Ceftriaxone and vancomycin are an appropriate empiric
antibiotic regimen in an asplenic patient with fever.
- Which of the following statements regarding the risk for
postsplenectomy sepsis is true?
A. The indication for splenectomy has no bearing on a
patient’s risk for developing postsplenectomy sepsis.
B. Adult splenectomy patients have a greater likelihood of
developing postsplenectomy sepsis than do children or
newborns who require a splenectomy.
C. The risk for postsplenectomy sepsis is highest in the first
year after splenectomy, but asplenic patients’ increased
risk for developing sepsis persists for approximately 10
years following splenectomy.
D. The risk of sepsis is increased in splenectomy patients
due to impaired cellular immunity.
E. None of the above.
ANSWER: E
ANSWER: C
COMMENTS: Asplenic patients (those who have either undergone splenectomy or are functionally asplenic, such as in sickle cell
disease) are at an increased risk for a fulminant and potentially
rapidly fatal overwhelming bloodstream infection caused by encapsulated organisms. This is due to impaired bacterial clearance,
especially of encapsulated organisms (i.e., S. pneumoniae, Neisseria meningitidis, and H. influenzae), and impaired humoral (not
cellular) immunity. The risk of developing postsplenectomy sepsis
varies based on the indications for splenectomy, the age at which
the patient underwent splenectomy (or became functionally
asplenic), and the time interval since splenectomy (or functional
asplenia). In terms of indication for splenectomy, patients who have
undergone splenectomy for trauma are at the lowest risk; those who
have undergone splenectomy for hereditary spherocytosis or
immune thrombocytopenic purpura are at intermediate risk; and the
greatest risk patients are those who are functionally asplenic due
to α-thalassemia, sickle cell disease, or portal hypertension. Children (especially those under the age of 5 years) are at a greater risk
for developing sepsis than are adults, but this may also be confounded by the indications for splenectomy or functional asplenia
in this age group. Overall, the risk for postsplenectomy sepsis is
greatest in the first year following splenectomy, but patients who
have undergone splenectomy are at an increased risk for sepsis for
approximately 10 years following surgery.CHAPTER 5 / Surgical Infection and Transmissible Diseases and Surgeons 63
Since the year 2000, when universal vaccination with the
heptavalent pneumococcal conjugate vaccine (PCV7) in children
began, the rates of invasive pneumococcal infection have dropped
significantly, and the rates have continued to fall with the development of the 13-valent vaccine (PCV13) in 2010. Patients who
undergo splenectomy or are functionally asplenic should receive
vaccinations for the encapsulated organisms prior to splenectomy
if it is elective or prior to discharge if performed urgently.
Treatment of postsplenectomy sepsis should be rapid. A fever
in any postsplenectomy patient should prompt initiation of antimicrobial therapy as it may be the only sign of an impending fulminant infection. Postsplenectomy patients, even those who have
undergone vaccination for S. pneumoniae, N. meningitidis, and H.
influenzae, should be counseled to seek medical attention with any
febrile episode. The most common causative organism is S. pneumoniae, so ceftriaxone, which is also active against H. influenzae
and N. meningitidis, is appropriate. Vancomycin should be administered as well due to concerns for penicillin-resistant pneumococcus and β-lactamase–producing H. influenzae. Antibiotics should
be administered immediately and should not be delayed to obtain
cultures
