EMERGING
INFECTIOUS DISEASES
Bartonella, Erlichia, and Helicobacter
Email: tinzana@vt.edu
Bartonella
Classification
Gram-negative bacteria
Alpha-2 subgroup of Proteobacteria
Most closely related to Brucella
abortus
Former genus name Rochalimaea
Can be cultured, but with difficulty; slightly curved,
pleomorphic rods, 0.5-0.6 um X 1.0-2.0 um, and motile by polar flagella
B.
bacilliformis - Oroyo fever or Carrions disease
B. quintana - Trench
fever
B. henselae -
bacillary angiomatosis (BA), Parinauds oculoglandular syndrome, and cat
scratch disease (CSD)
B.
clarridgeiae- rare cause of CSD; fairly common in blood of cats
B.
elizabethae- rare cause of bacteremia and endocarditis
Transmission
B.
bacilliformis (Bartonellosis)
Found only in the river valleys of Peru, Eucador, and
Columbia on both slopes of the Andes between 800 and 2500 m
Vector is the nocturnal phlebotomine sandfly
Incubation period is between 7 and 100 days
Clinical
disease and pathology
B.
bacilliformis (Bartonellosis)
Acute phase of infection - Oroyo fever
Fever,
chills, myalgia, and hemolysis
Bacteria
invade erythrocytes resulting in erythrocytic anemia (mild to severe)
Fatality
rate is 40-90%, but most patients die of salmonellosis, malaria, or other
infections
Many
infections are asymptomatic
Continued
One to several months after acute phase subsides, verruga
peruana (VP) develops
VP is
characterized by subcutaneous nodules that enlarge rapidly and bleed easily
This phase
may last 4-6 months and may be recurrent
Lesions may
be small in crops or large, painful, and subcutaneous
In fatal cases of Oroyo fever patients have jaundice,
hepatosplenomegaly, and hyperplasia of the bone marrow
Infected erythrocytes and reticuloendothelial cells are
packed with bacteria
There is significant necrosis of liver and spleen
Thrombosis and infarction are common
Verruga peruana is a granulomatous reaction with vascular
proliferation
Edema and necrosis of lesions is common
In deeper parts of lesions neutrophils and endothelial cells
predominate, but mast cells, macrophages, and plasma cells are also present.
Bacteria are seen in stroma of lesion and neutrophils, but
not in macrophages or endothelial cells
Transmission:
B. quintana (Trench fever)
Acute febrile illness, similar to typhus
Transmitted by lice, primarily during World Wars I and II
Outbreaks have occurred in Mexico and Africa
Usually associated with epidemics
Febrile illnesses presumptively due to B. quintana have been documented in homeless persons in the U.S.
and France
Clinical
disease and pathology: B. quintana
(Trench fever)
Acute febrile illness
Incubation period of 4 to 35 days
Acute onset of fever and chills, myalgia, malaise, eye pain,
conjunctivitis, arthralgia, and bone pain (usually in shins)
Symptoms last 4-6 days, but may recur multiple times over
weeks or years
Brief maculopapular rash may be present
B. quintana can be
isolated from blood of patients
Bartonella spp. (B. quintana, B. henselae, and B. elizabethae) have all caused
bacteremia, particularly in homeless men
Bacteremia usually results in endocarditis and valve
replacement
Transmission
(CSD and BA)
Majority of cases of CSD and BA are transmitted through cat
exposure (usually a scratch, but also a bite or lick of broken skin); 1/3 of
BA patients report no exposure to cats!
Cats associated with CSD and BA are usually less than 1 year
old, and there is an association with the presence of fleas.
Peak incidence of CSD is September through January
CSD occurs throughout the U.S., Europe, and Japan
Antibodies to Bartonella
spp. are present in cats associated with CSD and BA
Children are most commonly affected with CSD, but symptoms
are more severe in adults
Clinical disease and pathology
CSD
Incubation period 7-50 days (2 weeks ave)
By 10 days after inoculation 3-5 mm macule forms at site; may
become papular
Systemic symptoms occur in majority of patients, consisting
of mild malaise, myalgia, fatigue, and anorexia; only 1/3 have any fever
Patients present with lymphadenopathy of one or a group of
nodes, usually axillary, but also cervical, groin, and periauricular.
Symptoms spontaneously improve over 2-4 months
2-4% of patients may have severe symptoms of fever lasting
> 2 weeks, weight loss, prolonged fatigue, neuroretinitis, encephalopathy,
hepatosplenomegaly, hemolytic anemia, thrombocytopenic purpura, erythema
nodosa, oculoglandular parotitis, and pneumonia
Severe CSD more likely in those >21, and course lasts
longer (1-2 years)
Bacteria proliferate in walls of capillaries and macrophages
of adjacent lymphatics
Bacteria disseminate and macrophages and neutrophils cause
necrosis and abscess formation
Vasculitis and granulomas form with central areas of
necrosis; this lesion results in the enlarged lymph node(s)
Clinical diagnosis must match 3 of 4 criteria:
1)
unexplained regional lymphadenopathy
2) history
of cat exposure; papule formation strength
3) histopathology
of lymph node consistent with CSD
4) positive
CSD skin test
Currently,
IFA for Bartonella-specific antibody
is sensitive and specific for CSD(~95%)
Diagnosis in tissues can be made by Warthin-Starry silver
impregnation stain
Look for branching, black-silvered bacteria in or around
macrophages from areas of necrosis or vascular proliferation
Clinical disease and pathology
BA
First reported in 1983; both B. henselae and B. quintana
can cause BA
Primarily occurs in patients with AIDS, but also other
immunosuppressed patients; rare in immunocompetent patients
Infections are systemic, and manifested by single or multiple
skin lesions that may be dome shaped or acuminate, red, purple, or skin colored
Skin lesions must be differentiated from Kaposis sarcoma,
hepangioma, and pyogenic granuloma
Fever, chills, headache, and anorexia common
Lesions often present in cardiac, respiratory,
gastrointestinal, musculoskeletal, endothelial, and central nervous systems
Lymph nodes can be enlarged and be similar to CSD
After entering skin or mucosal surface, bacteria enter lymph
node and disseminate to internal organs
Satellite colonies travel to skin or mucosa establishing
clinical lesions
No or
poorly developed granulomas form
Lesions are related to integrity of the immune system
There is vascular proliferation, suggesting an angiogenic
factor is produced by the bacteria
Immune response in these patients may be poor, so
histopathology of lesions is preferred method of diagnosis
Bacteria appear as granular clusters or tangled masses in
silver impregnation stains:
Brown-Hopps
(red), Giemsa (blue), Warthin-Starry and Wenger-Angritt (black), H&E
(blue-grey)
Diagnosis of all Bartonella
infections can also be done by culture, PCR, and presence of eubacterial 16S
rRNA in tissue
Susceptibility testing not standardized
Appear to be susceptible to 3rd generation cephalosporins,
tetracycline, macrolides, and rifampin; some may be susceptible to
trimethoprim-sulfamethoxazole and aminoglycosides
The efficacy of antibiotics in CSD is unclear
Often
antibiotics fail or have mixed results
Treatment of BA or bacteremia is more successful
Erythromycin
is drug of choice; doxycycline for those who cannot take erythromycin
Recurrences
are common and patients with AIDS may require lifelong therapy
Erlichiosis
Erlichia pathogens
of humans
E. sennetsu: sennetsu fever
lymphadenopathy, fever, and lethargy
Occurs only
in Japan, not North America
E. chaffeensis: human erlichiosis
Very
similar to Rocky Mountain Spotted Fever (RMSF), but without rash in most cases
HGE: human
granulocytic erlichiosis
Also
similar to RMSF
Genus Erlichia
named in honor of Paul Erlich
Members of family Rickettsiaceae
E.
chaffeensis is most similar to E.
canis and E. ewingii
HGE is closely related or identical to E. phagocytophila and E. equi
E.
chaffeensis has been reported in >400 patients; HGE in only 15
Thought to be transmitted by ticks; infections are most
common between May and October
Amblyomma and Dermacentor ticks have been found to be
positive for E. chaffeensis by
indirect FA and PCR of 16S rRNA
Ticks associated with 92% of patients with HE, and most were
identified as Ixodes scapularis or D. variabilis
Most patients are >60 yrs. old and men; median age is 44
Symptoms include sudden onset of fever, headache, malaise,
and other flu-like symptoms
Lab findings include thrombocytopenia, leukopenia, elevated
liver enzymes, and anemia
Fatalities may occur, with lesions throughout internal
organs, and multiple organ failure
Erlichia sp. Appear
as round, dark purple dots or clusters of dots (morulae) in the cytoplasm of
leukocytes (usually macrophages) in blood smears stained by Romanowsky-type
techniques (Giemsa, Wright, or Diff-Quick)
Such smears are most useful during the acute, febrile stage
Bone marrow can also reveal organisms within histiocytes and
lymphocytes
HGE has been found only in neutrophils, but may require
examination of 800 PMNs/ smear
HGE has been identified in spleen and neutrophils using
equine anti-E. equi serum or bovine
anti-E. phagocytophila
HGE has recently been grown in cell culture
Diagnosis can be done by PCR using primers to 16S rRNA
sensitivity can be enhanced using nested PCR
Specificity
is dependent on inside primers
Serologic diagnosis is done by indirect FA using antigen from
cells grown in a macrophage cell line
Testing for
HGE antibodies is based on use of E. equi
or E. phagocytophila antigen
Eliminating tick exposure is most effective means of
prevention
Infections are best treated with tetracycline
Chloramphenicol
may be a suitable alternative
Gastric ulcers were originally thought to be caused by excess
acid in the stomach
In 1983 spiral-shaped bacteria were found associated with
gastroduodenal inflammation
The theory that these bacteria were the cause of peptic
ulceration was dismissed by most for many years, but is now well accepted
Gastroduodental inflammation can be classified as primary or
secondary.
In most cases primary peptic ulceration is due to H. pylori colonization of gastric mucosa
Secondary peptic ulceration is usually systemic in nature
(i.e. anti-inflammatory agents, systemic illness, Chrons disease, etc.
Evidence of gram-negative organisms in the stomach has been
known since the late 1800s, but dismissed as incidental
1975: Steer and Colin-Jones identify gram-negative bacteria in stomachs of people with mucosal inflammation
1983: Marshall and Warren make association between colonization with gram-negative, spiral bacteria and gastroduodenal inflammation; culture of the agent is finally accomplished
Initially these bacteria were classified in the genus Campylobacter
1989: molecular (16S rRNA) and biochemical (cellular fatty
acids) analysis of these bacteria is done, and a new genus is created to
classify it: Helicobacter
H. pylori may appear
in a bacillary form (spiral or curved) or coccoid
Highly motile with unipolar flagella
Urease, catalase, and oxidase +
Urease is used to metabolize urea and create a neutral
environment in the gastric mucosa
Currently there are 11 spp. of Helicobacter
H.
fennelliae and H. cinadedi
reside in lower GI tract and cause diarrhea in immunocompromised patients (HIV
+)
Most other Helicobacter
spp. are animal pathogens
H. felis, a pathogen of cats, has been used
as an animal model to develop vaccines
H. hepaticusis a pathogen of mice and is being
studied because it causes hepatocellular carcinoma in mice
Gastrospirillum
hominis or Helicobacter
heilmannii have also been observed in gastric biopsies, but have not yet
been cultured. Their clinical relevance
is uncertain
H.
heilmannii has been identified in gastric mucosa of cats, and G. hominis or a related agent in dogs
H. mustelae causes
gastric pathology in ferrets similar to
that caused by H. pylori
Gastritis,
gastric ulcers, and gastric carcinoma after long-term infection
True incidence of H.
pylori infection is unknown
Most infected individuals are asymptomatic or have been
carrying the organism for years unknown
Most infections are established in childhood
The incidence of infection in industrialized countries is
estimated at 0.5%/year
In developing countries, it is 3-10%.year
Incidence in children is higher than in adults
Risk if
being infected increases with decreasing socio-economic status, overcrowding,
etc.
Route of transmission thought to be fecal-oral
H. pylori DNA has
been found in dental plaque
Chronic gastritis
Primary duodenal ulcers
Gastric ulcers less common
Associated with gastric cancer, particularly if the agent is
acquired early in life
Thought to play a role in low-grade B-cell lymphoma of
mucosa-associated lymphoid tissue (MALT)
Thickened gastric folds are the result of inflammation;
usually with H. pylori, but also due
to neoplasm
There is degeneration of surface epithelium
Lymphoid hyperplasia of the stomach with lymphoid follicles
Gastric ulcers
Atrophy with decreasing inflammation and bacteria with age of
chronically infected patients
Invasive or noninvasive
Gold Standard is endoscopy and esophagas-troduodenoscopy
with gastric biopsy for pathology and histology
Culture is not sensitive and few labs offer it
A silver stain is the best method for identifying the
bacteria in tissue sections
Biopsy samples can also be tested for urease
PCR sensitive, but may have high false + rate
Noninvasive methods
Most
promising tests for urease in breath following administration of a 13C-
or 14C-labeled meal
This test
is also useful for determining treatment success
Serology
for H. pylori antigens (many ELISA
kits)
Serology
will not differentiate current from past infection
All patients with ulcers who are infected with H. pylori are recommended to receive
antimicrobial therapy
Successful therapy requires 2 or more drugs
Treatment is not 100% successful with all patients, and
resistance can develop
Treatment Recommendations for adults:
A bismuth
compound (524 mg 4 times daily)
Tetracycline
(500 mg 4 times daily)
Metronidazole
1-1.5 g/day)
Similar recommendation for children except tetracycline is
replaced with amoxicillin
Average duration of therapy is 2 weeks
Vaccines are being investigated for prevention
One candidate is a recombinant oral urease protein given with
the E. coli heat-labile toxin as
adjuvant
H. felis serves as
a model in these studies
Urease
Motility (flagella help it move through the mucosa to gastric
epithelial cells where it adheres and colonizes)
Vacuolating cytotoxin (produces vacuoles in epithelial cells
in vitro)
CagA protein (105 -140 kDa) correlated with vacuolating cytotoxin activity
A strong local and systemic immune response is made to H. pylori following colonization
The gastric mucosa is infiltrated with monocytes,
macrophages, PMNs, and plasma cells; not T cells
Elevated levels of cytokines (IL-1, IL-2, IL-6, IL-8, and
TNF) are present in gastric mucosa
A strong systemic IgG response is made
Despite the strong immune response, the bacteria are not
cleared, and following antibiotics reinfection can occur
Lecture 6 Sample Questions
1.
Which factors are associated with either cat scratch disease or bacillary
angiomatosis, but not both, in adults?
A. Manifestation of systemic symptoms.
B. Association with exposure to cats.
C. Only one of these diseases can be effectively diagnosed in most cases by
serology.
2.Erythomycin is effective in the treatment of
A. Helicobacter pylori gastritis
B. Erlichiosis
C. Bacillary angiomatosis
3. Which of the following is NOT true of Erlichia
infections:
A. They are most likely transmitted by mosquitoes.
B. There are thought to be two agents that cause infections in humans.
C. Symptoms are primarily systemic, and present as a flu-like illness.
4. H. pylori is NOT associated with which disease:
A. Diarrhea
B. Gastritis
C. Gastrointestinal ulcers