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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_182_библиотеки_им_акад_М_И_Перельмана.pdf
GRAM-NEGATIVE ENTERIC ORGANISMS AND THEIR INFECTIONS
Symptoms of enterocolitis are nonspecific and
include nausea, vomiting, fever, abdominal pain,
and diarrhea (may contain blood and mucus)
Symptoms of mesenteric adenitis are similar to
appendicitis and include fever and right lower
quadrant pain
Reactive arthritis may develop
Virulence factors of Yersinia include an array of
adhesions to facilitate adherence to cells and tissues
and a type III secretion system for injection of effector
proteins to modulate host immune system
Campylobacter
Clinically relevant species: Campylobacter jejuni and
Campylobacter fetus
Both species have diverse animal reservoirs and
infection usually occurs through ingestion of
contaminated food and water
Undercooked poultry is a particularly significant
route of infection
C. jejuni infection usually presents as acute enteritis,
characterized by abdominal pain, diarrhea (watery
or bloody), malaise, and fever
C. fetus can cause a systemic disease that can
manifest as bacteremia, meningitis, vascular
infection, or abscess
More likely to be isolated from bloodstream than
from feces
Virulence factors are not extensively characterized
for these organisms, though processes of motility,
Bacterial Infections: Bacterial Infections Requiring Culture/Ancillary Confirmation
adhesion, invasion, and toxin production are all
important for organism to establish disease
Vibrio
While Vibrio cholerae is most notorious species of this
group, Vibrio parahaemolyticus and Vibrio vulnificus can
also cause serious human disease
Humans are the only host for V. cholerae, though it
is able to propagate in environment
Disease is described in context of 7 known
pandemics since 1800 (7th still ongoing), most of
which have arisen on Indian subcontinent
Spread is via contaminated water and food
V. parahaemolyticus and V. vulnificus are also able to
propagate in coastal waters and are part of normal
microbiome of shellfish
Consumption of raw or undercooked shellfish is
main source of human disease by these pathogens
Infection by V. cholerae presents as an acute and very
profuse (up to 1 L per hour) watery diarrhea ("rice
water stool")
Associated signs and symptoms are related to
extreme dehydration
V. parahaemolyticus has a similar though less severe
presentation
V. vulnificus is distinct in that it is less likely to
produce diarrheal illness and more likely to cause
sepsis and cutaneous lesions
Disease begins with fever, chills, and hypotension
II
followed by development of cutaneous lesions
Lesions will rapidly progress from vesicular or
bullous lesions to necrotic ulcers
2
Virulence factors
V. cholerae is not an invasive pathogen
Virulence factors include toxin-coregulated pili
(TCP), which allow organism to colonize small
intestine, and cholera toxin (CT), which causes
increased cAMP in intestinal epithelial cells and
chloride secretion
Diarrhea results from subsequent water loss
V. parahaemolyticus virulence is mainly mediated
by 2 enterotoxic hemolysins: Thermostable direct
hemolysin (TDH) and TDH-related hemolysin (TRH)
Virulence factors have been less well characterized
in V. vulnificus, but include polysaccharide capsule
CLINICAL IMPLICATIONS
Laboratory Tests
Gram stain and culture
Detection of Shiga toxin from primary samples (PCR,
immunoassay)
Molecular detection directly from primary samples
(i.e., FilmArray)
Treatment
Surgical approaches
Certain cases of GI tract-origin gram-negative
infections require surgical interventions, such as
infective endocarditis (valve replacement) and V.
vulnificus cellulitis (debridement)
Drugs
Treatment is based on isolate susceptibility
Prognosis
Varies widely with host status and organism
MICROBIOLOGY
Morphologic and Biochemical
Characteristics
Gram negative
Rod-shaped, with exceptions of Vibrio (curved rod)
and Campylobacter (comma shaped)
Culture
Most grow on sheep’s blood agar
MacConkey agar commonly used to select for gramnegative organisms and differentiates by lactose
production
Microbiologic Identification
Several tests for biochemical reactions are available
as rapid, bench-top assays that make most routine
identifications, e.g., oxidase and indole production
A number of API strips (Biomrieux) are available for
identification of gram-negative organisms
Vitek 2 gram-negative card is also routinely used in
many clinical laboratories to make identifications
based on a large array of biochemical reactions
Several assays are available for specific detection of
Shiga toxin (PCR, immunoassay, etc.)
30
GRAM-NEGATIVE ENTERIC ORGANISMS AND THEIR INFECTIONS
Bacterial Infections: Bacterial Infections Requiring Culture/Ancillary Confirmation
BY ORGAN SYSTEM
Central Nervous System
Meningitis
Organisms
Gram-negative meningitis is associated with sepsis,
trauma, neurosurgical procedures, and disseminated
strongyloidiasis in hyperinfection syndrome
Cytospin preparations demonstrate sheets of
neutrophils in the cerebrospinal fluid
Gram-negative bacilli likely present on Gram stain
(extracellular and within phagocytic cells)
Meninges may demonstrate reactive features in
meningothelial cells
Brain abscess
Organisms: Any organism causing gram-negative
sepsis, especially in setting of thrombosis
Associated with neurosurgical procedures
Citrobacter has a propensity to form abscess as a
complication of meningitis in neonates
Pulmonic
Aspiration pneumonia
Organisms: All members of Enterobacteriaceae
(pneumonia caused by K. pneumoniae can be
particularly severe and sometimes chronic)
Patchy distribution of acute inflammation with
admixed macrophages alternating with areas of
nodular, fibroblastic foci (organizing)
Often associated with hemorrhage and abscess
formation
Clusters of gram-negative rods often visible
Cardiac
Endocarditis
Organisms: E. coli and Salmonella are the most
common causes of gram-negative endocarditis (2%
of all endocarditis)
Salmonella has a proclivity for damaged heart valves
(particularly on left side)
Acute inflammatory infiltrates, atrial thrombus, and
valve perforation or destruction may be seen
Organisms often visible with Gram or silver stains
Infected aortic aneurysm
Organisms: E. coli and Salmonella
Acute inflammation is commonly, but not always,
superimposed on atherosclerosis
Gram stain often does not reveal organisms
and culture or other methods are required for
identification
Hepatic
Abscess
Organisms: E. coli and K. pneumoniae are the most
common GI-source bacteria associated with liver
abscess, though other Enterobacteriaceae may also
be seen
Often a necrotic center, neutrophilic infiltrates
Cytospin preparations of aspirated material may
show abundant neutrophils
Reticuloendothelial
Splenic abscess
Organisms: Any of Enterobacteriaceae,
predominantly E. coli and Klebsiella
Diagnosis is by imaging
Gastrointestinal
Hemorrhagic diarrheal diseases
Organisms: E. coli (STEC or EHEC, EAEC, EIEC),
Shigella, Salmonella, Campylobacter, Y. enterocolitica
Nontyphoidal Salmonella and Campylobacter tend
to produce an acute, self-limited colitis picture with
a polymorphonuclear infiltrate in lamina propria,
cryptitis, and occasional crypt abscess
In general, crypt architecture is preserved (except
in severe disease)
Neutrophils may be less prominent in Salmonella
infection than other pathogens
Shigella may also produce an acute, self-limited
picture but can also cause pseudomembrane and
ulcer formation
Crypt architecture may be markedly distorted
with a heavy neutrophilic infiltrate in lamina
propria
Generally affects left colon and can be very
difficult to distinguish from inflammatory bowel
disease
EHEC may present similarly to Shigella with
addition of bowel edema (can be very prominent),
necrosis, crypt withering, and microthrombi in
small vessels
Preferentially affects right colon
Enteritis caused by Yersinia infection can be
differentiated from that caused by other pathogens
by its propensity to promote granulomatous
inflammation with lymphoid cuffing, though the
pattern can be mixed with a diffuse neutrophilic
infiltrate
Other features include lymphoid hyperplasia,
transmural lymphoid aggregates, giant cells, and
ulceration
Nonhemorrhagic diarrheal diseases
Organisms: E. coli (ETEC, EPEC and others),
Salmonella (generally nontyphoidal), Vibrio
Minimal or no inflammatory change
Genitourinary
Hemolytic uremic syndrome/renal microangiopathy
Organisms: E. coli
Schistocytes in peripheral blood
Microangiopathic changes with fibrin thrombi in
kidneys (glomeruli) and other organs (systemic)
Cortical necrosis may be present
Pyelonephritis
Organisms: Any uropathogen (e.g., E. coli, P.
mirabilis, Klebsiella, and Enterobacter)
Neutrophilic infiltrates may be observed in tubules
and collecting ducts
Abscesses may be present, though if they are
small and concentrated in cortex, it may indicate
hematogenous spread rather than an ascending
infection from lower urinary tract
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31
GRAM-NEGATIVE ENTERIC ORGANISMS AND THEIR INFECTIONS
Glomeruli are generally spared except in severe cases
Emphysematous pyelonephritis may be a
complication when gas collects in necrotic areas,
usually in an organ with preexisting diabetic
glomerulosclerosis
Usually caused by E. coli or K. pneumoniae
Cystitis
Organisms: Any uropathogen (e.g., E. coli, P.
mirabilis, Klebsiella, and Enterobacter)
May display acute or chronic inflammation
Emphysematous cystitis may arise in a background
of chronic urinary tract infection, neurogenic
bladder, trauma, urinary stasis, or instrumentation
Characterized by empty cavities in lamina propria
Foreign body giant cells may be present
Prostatitis/epididymitis
Uropathogens are typical cause of prostatitis and
epididymitis, with E. coli being most frequently
isolated
Granuloma inguinale (donovanosis)
Organisms: K. granulomatis
An ulcerating disease of genital areas
PAP smear or ulcer biopsy may demonstrate nonnecrotizing granulomatous inflammation with
epithelioid histiocytes, giant cells, and lymphocytes
Intracellular organisms may be seen within
histiocytes (Donovan bodies)
Ulcerations can be quite severe and engulf entire
genital region if left untreated
Bone
Bacterial Infections: Bacterial Infections Requiring Culture/Ancillary Confirmation
Osteomyelitis
Hematogenous spread
Organisms: Generally monomicrobial
Commonly isolated gram-negatives include
Salmonella (especially in Sickle cell disease), E. coli,
and Klebsiella
Gram-negative organisms are most common in
children or adults with some pathology (IV drug
abuse, diabetes, sickle cell disease, etc.)
Typically manifests as a suppurative lesion with
edema, hemorrhage, and necrosis
Salmonella may produce granulomatous
inflammation
Bacteria may be visible on Gram or silver stain
Contiguous spread or direct inoculation
Organisms: Generally polymicrobial as a
consequence of spread from an open, infected
ulcer or wound (e.g., periodontal abscess,
decubitus ulcer, or open fracture); E. coli, Proteus
and Klebsiella are all commonly isolated
In addition to features of osteomyelitis by
hematogenous spread, disease by contiguous
spread may demonstrate chronic inflammation
(especially in the case of spread from an ulcer)
Skin
Cellulitis
Enterobacteriaceae are uncommon causes of
II
cellulitis except in diabetic patients, particularly as a
complication of decubitus ulcers
Necrotizing fasciitis
2
V. vulnificus can cause a severe necrotizing fasciitis
characterized by involvement of dermis, subcutis,
and particularly fascia and deep soft tissues
Hemorrhage, necrosis, thrombosis, vasculitis
Soft Tissue
Myositis
Very rarely caused by Enterobacteriaceae
Rhinoscleroma
Organisms: K. pneumoniae subsp rhinoscleromatis
Disease occurs in 3 phases: Rhinitic, proliferative
(granulomatous), and cicatricial (sclerotic)
Proliferative stage is best characterized and features
epithelial hyperplasia with a mixed inflammatory
infiltrate in underlying stroma
Plasma cells, foamy histiocytes [Mikulicz cells]),
lymphocytes, and neutrophils
Usually arranged in sheets, though microabscesses
may also be present
Sclerotic stage is defined by fibrosis and scant
cellularity (mostly lymphocytes and plasma cells)
Organisms can often by seen with H&E or silver
stain
DIFFERENTIAL DIAGNOSIS
DDx of Gram-Negative Pneumonia
Pneumococcal infection and other gram-positive
pneumonias
Less acute and progressive than pneumonia caused
by gram-negative pathogens
Culture to differentiate
DDx of Granuloma Inguinale
Syphilis (painless), chancroid (usually painful)
Presence of Donovan bodies are specific to
granuloma inguinale
Culture, special stains, immunohistochemistry to
differentiate
DDx of Rhinoscleroma
Infectious
Tuberculosis
Leprosy
Leishmaniasis
Sarcoidosis
Noninfectious
Lymphoma
Nasopharyngeal carcinoma
Basal cell carcinoma
Differentiate by culture, presence of Mikulicz cells
SELECTED REFERENCES
1. Donnenberg MS: Enterobacteriaceae. In Bennett JE et al:
Mandell, Douglas, and Bennett’s Principles and Practice
of Infectious Diseases. 8th Edition. Philadelphia: Elsevier/
Saunders. 2503-17, 2015
2. Lichtenberg, F: Pathology of Infectious Diseases. New York:
Raven Press, 1991
32
GRAM-NEGATIVE ENTERIC ORGANISMS AND THEIR INFECTIONS
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g
x
p
p
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Gross and Microscopic Features
Bacterial Infections: Bacterial Infections Requiring Culture/Ancillary Confirmation
(Left) This gross photograph
showing a lung after
bronchopneumonia caused
by gram-negative enteric
organisms demonstrates
residual fibrosis .
(Courtesy Franz von
Lichtenberg Collection of
Infectious Disease Pathology,
BWH.) (Right) Lung tissue
demonstrates E. coli and E.
cloacae bronchopneumonia
with necrosis of alveolar
walls apparent (in
contrast to pneumococcal
neumonia). (Courtesy
Franz von Lichtenberg
Collection of Infectious
Disease Pathology, BWH.)
(Left) Friedlander disease
(Klebsiella pneumoniae)
is an acute necrotizing
neumonia. The alveoli
are filled with neutrophils
, and necrosis
is present. (Right) This
ross photograph depicts
anthogranulomatous
yelonephritis with an
expanding local mass
mimicking tumor . P.
mirabilis and E. coli are most
frequently isolated from this
lesion. (Courtesy Franz von
Lichtenberg Collection of
Infectious Disease Pathology,
BWH.)
(Left) Renal typhoid is an
acute nephritis with marked
coagulative necrosis. This
high-power image shows
coagulative necrosis of the
roximal tubules , and
clouds of bacteria in the
center . (Right) In renal
typhoid, hemorrhage into
Bowman space can result in
rofound hemoglobinuria
and the formation of
erythrocyte casts . Again,
note the abundant bacterial
forms visible on H&E.
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33
GRAM-NEGATIVE ENTERIC ORGANISMS AND THEIR INFECTIONS
p
Gross and Microscopic Features
(Left) Low-power image
shows intestinal typhoid
with transmural coagulative
necrosis (between ), loss
of epithelium (between ),
edema, and inflammation.
(Right) In a case of bacillary
dysentery, this medium-power
image shows an earlier phase
of acute necrosis with loss of
the surface epithelium and
replacement by a tenacious
clot of fibrin with admixed
necroinflammatory debris.
(Left) Yersinia infection
may cause deep colonic
ulcers , particularly in
the proximal colon. This
case shows diffuse mucosal
erythema and an indurated
wall reflecting increased
lymphoid tissue and fibrosis.
Bacterial Infections: Bacterial Infections Requiring Culture/Ancillary Confirmation
(From DP: Endoscopy.)
(Right) Some cases of bacterial
enterocolitis show mucosal
hemorrhage that can mimic
the features of ischemic colitis.
Campylobacter infection
shows fresh lamina propria
hemorrhage , but the crypts
are not mucin depleted. (From
DP: Gastrointestinal.)
(Left) Gross photograph of a
liver from a patient who died
of metastatic carcinoid tumor
shows a drained abscess
, which grew Klebsiella
neumoniae, Enterococcus
faecium, and Enterobacter
cloacae. (Right) The histology
of a hepatic abscess shows
necrotic tissue and
abundant acute inflammation
. As this is an early acute
lesion, there is no reactive
capsule. The abscess cavity
is filled with necrotic debris
mixed with bile. Cultures grew
Klebsiella species.
II
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GRAM-NEGATIVE ENTERIC ORGANISMS AND THEIR INFECTIONS
p
g
Microscopic Features
Bacterial Infections: Bacterial Infections Requiring Culture/Ancillary Confirmation
(Left) This patient underwent
right colectomy for severe
bleeding due to Salmonella
infection. Scattered, sharply
demarcated ulcers
extend into the submucosa
and are associated with
dense inflammation with
fibrosis . (From DP:
Endoscopy.) (Right) This
H&E section demonstrates
the pseudoepitheliomatous
roliferation in
ranuloma inguinale
(donovanosis). (Courtesy
Franz von Lichtenberg
Collection of Infectious
Disease Pathology, BWH.)
(Left) High-power view
of granuloma inguinale
demonstrates weakly
basophilic corpuscles in
cytoplasmic vacuoles:
Leishman-Donovan bodies
. (Courtesy Franz von
Lichtenberg Collection of
Infectious Disease Pathology,
BWH.) (Right) Silver stain
reveals that LeishmanDonovan bodies contain
short rods , corresponding
to Klebsiella pneumoniae
subsp granulomatis.
(Courtesy Franz von
Lichtenberg Collection of
Infectious Disease Pathology,
BWH.)
(Left) This specimen of
Rhinoscleroma demonstrates
numerous foamy histiocytes
(Mikulicz cells) . (Right)
This silver-stained specimen
of rhinoscleroma highlights
several short, stubby
rods corresponding
to K. pneumoniae subsp
rhinoscleromatis.
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35
GRAM-NEGATIVE ZOONOTIC PATHOGEN INFECTIONS
Bilateral psoas abscesses (with calcification) and
narrowed canal would be typical of TB. Patient
worked in a meat-packing plant and titers were positive
for brucellosis. (From DI: MSK Non-Trauma.)
ETIOLOGY/PATHOGENESIS
Environmental Exposure
Brucella
Developed countries: Associated with meat-packing,
dairy, and other occupations with exposure to
Bacterial Infections: Bacterial Infections Requiring Culture/Ancillary Confirmation
animals
Developing countries: Food-borne, and acquired
through unpasteurized milk products (cows or goats)
Considered a potential agent of bioterrorism
Francisella
Few cases in United States (concentrated in
Arkansas, Missouri, Kansas, South Dakota,
California, Oklahoma, and Massachusetts)
Generally transmitted to humans via an arthropod
vector, usually a tick or biting fly
Infection occurs by bloodstream inoculation
via insect bite as well as airborne exposure to
contaminated dusts and aerosols, ingestion of
contaminated food and water, and cutaneous
exposure to infected animals
Considered a potential agent of bioterrorism
Yersinia pestis
Associated with exposure to rodents and their fleas
In United States, most prevalent in West
Infectious Agents
Brucella
Clinically relevant species: Brucella melitensis,
Brucella suis, and Brucella abortus
Francisella
Most clinically relevant species is Francisella
tularensis (divided into 4 subspecies)
F. tularensis subspecies tularensis is the most
virulent and common cause of infections in North
America
II
Yersinia
Most clinically relevant zoonotic species is Y. pestis
Exposure can be cutaneous or inhalational
2
Lung section shows focal necrotizing pneumonia
caused by Francisella tularensis, adjacent to relatively
normal lung with emphysematous change . Special
stains for organisms may be negative.
CLINICAL ISSUES
Presentation
Brucella (brucellosis)
Most common presentation is fever, followed
by osteoarticular involvement, sweating, and
constitutional symptoms
Diarrhea may be present in 3-6%
Exam findings often include hepatosplenomegaly
(30%) and lymphadenopathy (10%)
Osteoarticular involvement (50%): Sacroiliitis,
spondylitis, arthritis, osteomyelitis
Hepatobiliary manifestations: Reactive hepatitis
with granulomas, liver abscess
Genitourinary findings (10%): Orchiepididymitis,
glomerulonephritis, renal abscess
Neurological manifestations (6-7%): Peripheral
neuropathy, chorea, meningoencephalitis, cranial
nerve damage (usually CN6 and CN8), and
psychiatric disturbances
Pulmonary features (1%): Pleural effusions,
pneumonia, granulomas, abscesses
Skin involvement: Erythematous papular lesions,
purpura, dermal cysts, Stevens-Johnson syndrome
Hematological: Leukocytosis, leukopenia,
thrombocytopenia, anemia
Cardiac
Endocarditis (1%): Most likely cause of death in
brucellosis (aortic valve most common)
Myocarditis, pericarditis, endarteritis,
thrombophlebitis, and mycotic aneurysms have
also been reported
Ocular lesions: Anterior uveitis, chorioretinitis, optic
neuritis, papilledema, keratitis
Pregnancy: Intrauterine infection, fetal death,
spontaneous abortion, prematurity, low birth weight
Francisella
Incubation period: 1-20 days
36
GRAM-NEGATIVE ZOONOTIC PATHOGEN INFECTIONS
Bacterial Infections: Bacterial Infections Requiring Culture/Ancillary Confirmation
Etiology
Brucella
Developed countries: Associated with meatpacking, dairy, and other occupations with
exposure to animals
Nonspecific symptoms (fever, osteoarticular,
constitutional) affecting all organs
Histopathology: Granulomas and mixed
inflammatory infiltrate (commonly liver, but can
affect any site)
Francisella
Within United States, concentrated in Arkansas,
Missouri, Kansas, South Dakota, California,
Oklahoma, and Massachusetts
Generally transmitted to humans via an arthropod
vector, usually a tick or biting fly
Presenting symptoms: Fever, chills, headache,
malaise, fatigue, cough, vomiting, sore throat,
abdominal pain, and diarrhea
6 classic forms of tularemia: Ulceroglandular,
pneumonic, glandular, oculoglandular, pharyngeal,
and typhoidal, with the first 2 being most common
Ulceroglandular tularemia often presents with
painful, isolated lymphadenopathy
A skin lesion may be present, either before or after
lymphadenopathy occurs
Lesion evolves from red, painful papules,
sometimes with vesicles, to a necrotic lesion, and
finally to a painful ulcer with a raised border that
may take weeks to resolve
Pneumonic tularemia can be either primary
or secondary, developing from inhalation or
hematogenous seeding of lung, respectively
Symptoms include fever, cough, minimal sputum
production, pleuritic chest pain
Adult respiratory distress syndrome may be a
complication
Pleural fluid is generally exudative, with a
lymphocytic predominance
Yersinia
Causative agent of plague
Can develop as 3 distinct forms: Primary bubonic
plague (majority of cases), septicemic plague, and
pneumonic plague
Primary bubonic plague presents with headache,
chills, high fever, and buboes (swollen lymph
nodes) developing in neck, groin, or axilla
Septicemic plague is a rapidly progressive disease
leading to organ failure; buboes are not apparent
Pneumonic plague (primary from inhalation,
or secondary via hematogenous spread) is also
rapidly progressive, moving from fever, malaise,
headache, and cough to hypoxia, hemoptysis,
chest pain, and dyspnea within 1-2 days
Laboratory Tests
Brucella
Key Facts
Yersinia pestis
Top Differential Diagnoses
Granulomatous Inflammation
Necrotizing pneumonia (Francisella and Yersinia)
Skin lesions and lymphadenopathy
Francisella
Yersinia
Treatment
Drugs
MICROBIOLOGY
Morphologic and Biochemical
Characteristics
Brucella
Ulceroglandular and pneumonic forms
Histopathology: Necrosis, abscess, and granuloma
in lymph nodes as well as necrotizing pneumonia
Associated with exposure to rodents and their fleas,
most commonly in western USA
Causative agent of plague
Mycobacteria, Bartonella, Burkholderia pseudomallei,
Nocardia, Listeria, Actinomycetes
Anthrax
Pasteurellosis, plague, anthrax, mycobacteriosis,
bartonellosis
Blood culture is gold standard for diagnosis (70-90%
sensitive with lysis centrifugation method)
Gram stains of tissues and fluids are generally
negative
Cultures are generally negative unless plated on
supportive (cysteine-containing) media
Biosafety issues (select agent) due to highly
infectious organism
Serologic studies are extremely important for
diagnosis, though they generally only detect
antibodies to subspecies tularensis and holoarctica
IgM and IgG appear together within 2 weeks of
infection and peak at 4-5 weeks
Diagnosis requires multiple tests demonstrating an
acute rise in titre, as both IgM and IgG can remain
at high titers for up to a decade post infection
Cultures &/or direct examination of blood, bubo
aspirates, sputum, tracheobronchial washes, swabs
of skin lesions, and CSF
Brucella
Treatment regimens for brucellosis involve multiple
drugs for extended periods of time
Francisella
Streptomycin and gentamicin are drugs of choice
for all forms of tularemia except meningitis,
which may require additional drugs with superior
penetration into CSF
Yersinia
Streptomycin is drug of choice
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37
GRAM-NEGATIVE ZOONOTIC PATHOGEN INFECTIONS
Small, aerobic, non-spore-forming, gram-negative
rods or coccobacilli
Francisella
Small, aerobic, non-spore-forming, gram-negative
coccobacilli
Yersinia
Aerobic, gram-negative bacillus that displays bipolar
staining with Giesma or Wright stain
Culture
Brucella
Growth on blood and Meller-Hinton agars
Francisella
Common media that can support growth include
chocolate agar, buffered charcoal-yeast extract agar,
and Thayer-Martin agar
Growth is slow, and colonies may take 48 hours to
appear
Yersinia
Cefsulodin-irgasan-novobiocin (CIN) agar is used for
selection and differentiation of Yersinia species
Microbiological Identification
Brucella and Francisella
Further testing is generally done in a reference
laboratory within Laboratory Response Network
(LRN)
Yersinia
Automated typing systems are notoriously poor
Bacterial Infections: Bacterial Infections Requiring Culture/Ancillary Confirmation
at indentifying Yersinia species (API20E is most
accurate)
MICROSCOPIC PATHOLOGY
Histologic Features
Brucella
Liver: Granulomas, mixed inflammatory cell
infiltrate in sinusoids, focal and centrilobular
necrosis, abscess
Brucelloma: Liver mass with central calcification,
manifestation of chronic or reactivated
granulomatous disease
Examination of heart valves may reveal vegetations
(most commonly) on aortic and mitral valves
Granulomatous lesions of myocardium have also
been reported
Spleen: Giant cells and increased numbers of
macrophages may be observed, along with
granulomas
Testes and epididymides: Widespread inflammation,
by some reports predominantly lymphocytic
Francisella
Lymph nodes: Mixed cellular inflammatory
infiltrate and necrosis (focal [outer cortex]
or widespread), occasional granulomas, and
inflammation extending beyond lymph node
capsule
Fine-needle aspirations of affected lymph
II
nodes may demonstrate suppuration, necrosis,
granulomas, and abscess formation
Macrophages are often present, and phagocytosed
bacteria may rarely be observed
Lung: Necrotizing pneumonia with abundant fibrin
and neutrophils within alveolar walls and spaces,
edema, and widespread necrosis
Liver and spleen: Microabscesses
Other: Suppurative leptomeningitis and ulcerations
of small and large bowels
Yersinia pestis
Pulmonary
Suppurative, hemorrhagic, necrotizing pneumonia
Primary pneumonic plague may demonstrate
organisms in intraalveolar space while secondary
pneumonic plague from hematogenous spread
may be more likely to demonstrate organisms in
interstitium
Lymph nodes
Primary bubonic plague in draining lymph
nodes can demonstrate edema, hemorrhage, and
necrosis
Masses of organisms may be seen
DIFFERENTIAL DIAGNOSIS
Granulomatous Inflammation
Brucellosis must be differentiated from other
infections that commonly cause granulomas
Bacteria: Mycobacteria, Bartonella, Burkholderia
pseudomallei, Nocardia, Listeria, Actinomycetes, etc.
Fungi: Histoplasma, Sporothrix, Candida, Cryptococcus,
Aspergillus, etc.
Parasites: Schistosoma, Leishmania, Toxoplasma, etc.
Differentiate by morphology if organisms are
visualized in tissue sections, or culture, molecular
and serological testing
Noninfectious causes of granulomas (e.g., sarcoidosis
and Crohn disease)
Differentiate by chronicity and lack of infectious
agent
Necrotizing Pneumonia (Francisella and
Yersinia)
Other pathogens may cause a similar abrupt-onset,
fulminant pneumonia (e.g., anthrax)
Differentiate by clinical findings, serology, and culture
Skin Lesions and Lymphadenopathy
Pasteurellosis, plague, anthrax, mycobacteriosis,
bartonellosis
Differentiate by clinical findings, culture and serology
SELECTED REFERENCES
1. Guarner J et al: Histopathology and
immunohistochemistry in the diagnosis of bioterrorism
agents. J Histochem Cytochem. 54(1):3-11, 2006
2. Hunt AC et al: Histological findings in human brucellosis. J
Clin Pathol. 20(3):267-72, 1967
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38
GRAM-NEGATIVE ZOONOTIC PATHOGEN INFECTIONS
p
g
p
p
l
p
p
p
Microscopic Features
Bacterial Infections: Bacterial Infections Requiring Culture/Ancillary Confirmation
(Left) A liver biopsy from
a patient with brucellosis
demonstrates granulomata
in the liver parenchyma,
which are loosely organized
and not restricted to the
ortal triads. (Right) A liver
biopsy from a patient with
brucellosis demonstrates
ranulomata in the liver
arenchyma with hepatocyte
necrosis. Clinically, patients
resent with elevated
transaminases due to
multifocal granulomatous
diseases.
(Left) Lung section shows
focal necrotizing pneumonia
caused by Francisella
tularensis adjacent to areas
of active cellular pneumonia
with congestion and foca
hemorrhage . (Right) Lung
section shows pneumonia
filling alveolar spaces caused
by Francisella tularensis with
roteinaceous debris and
thickened alveolar septa .
(Left) This H&E section of an
inguinal lymph node from a
bubonic plague victim shows
widespread hemorrhagic
necrosis causing swelling
and effacement of normal
architecture. (Courtesy
Franz von Lichtenberg
Collection of Infectious
Disease Pathology, BWH.)
(Right) This Gram stain of
a Y. pestis infected inguinal
lymph node shows massive
roliferation of organisms,
articularly at the sinus
margins . (Courtesy
Franz von Lichtenberg
Collection of Infectious
Disease Pathology, BWH.)
II
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