Transcript Brucella, Francisella, Bordetella, Fastidious Gram-Negative

Brucella,
Francisella,
Bordetella,
Fastidious Gram-Negative
Rods
Genera of Uncertain Affliation
• Gram(-), small, coccobacilli
• Strict aerobe,
nonfermenter
• Most nonmotile
• Fastidious, enriched media
for culture
• Slow culture growth,
prolong incubation
• Brucella - brucellosis
• Francisella - tularemia
• Bordetella – pertussis,
important pediatric disease
Brucella: Zoonotic Pathogen
• Worldwide - >500,000 cases/year
• USA - <100 cases/year, control disease in
animals
• Usually mild, AS disease in natural animal
host
• Infect animal tissue rich in erythritol;
localize infection of breast, uterus,
placenta, fetus, epididymus
• Intracellular parasite of macrophage
• Cause of sterility, abortion, AS carriage of
infected animals
Brucella: Genera
• Four species infect humans – wide disease
spectrum:
– B. melitensis (goats, sheep) - most common
cause of brucellosis, causes severe disease
– B. suis (swine) – destructive lesions, prolonged
disease
– B. abortus (cattle) – mild disease
– B. canis (dog) – mild disease
• DNA studies show one species – B.
melitensis, others are biovars
Brucella: Lab Culture
• Brucella Blood agar - fastidious, requires
enriched media, CBA containing meat
infusion or tryptone
• Growth on CBA or chocolate agar, slow and
may take 72 hours
• Colonies start as tiny pinpoint, translucent
colonies, become gray with age
• Most clinical isolates obtained from blood
culture
Brucella: Lab ID
• Collect patient blood specimen, inoculate
directly into blood culture bottle
• Serum serology for Brucella antibodies to
test for infection
• Extreme care required for safe handling
of specimen and culture in lab
• Biosafety Level-3 pathogen - transmitted
by respiratory route, produce serious
disease; handle in biological safety cabinet
Brucella melitensis: Brucellosis
(Undulant Fever)
• “Malta (Island of Melita) Fever”
• In humans, ingestion of unpasteurized milk
or cheese from goats, cows; also acquire
MO via direct contact with infected
animals, inhalation
• At risk are veterinarians, slaughterhouse
workers, farmers, lab microbiologists
• CDC category B Select Biological Agent
– Easy to disseminate
– Moderate morbidity, low mortality
Brucellosis (Undulant Fever)
• Localized abcesses at site on inoculation;
bacteremia, MO phagocytized; localized in RES
tissues (spleen, liver, bone marrow, lymph nodes,
kidneys)
• Infection ranges from:
– Asymptomatic, subclinical
– Subacute - malaise, chills, sweats, fatigue, myalgia,
weight loss, nonproductive cough
– Acute infection – fever, chills, endotoxic disease
• Fever in all patients and intermittant:
– Typically spikes each evening
– Coincides with release of MO from phagocytes
– “Undulant” fever
Brucella: Treatment and
Prevention
• Chemotherapy difficult, intracellular
survival of MO in macrophages
• Combination doxycycline + rifampin
• Tetracycline toxic for pregnant moms and
young kids (<8 yr.) - SXT drug of choice
• Control by ID (serology) infected animals:
– Eliminate infected herds
– Animal vaccine to prevent infection
• Pasteurization of dairy products kills MO
• Biohazard safety precautions in the lab
Francisella tularensis: Zoonotic
Pathogen
• Tulare county – infected rodent transmit
to humans by tick bite
• Tularemia – glandular fever, rabbit fever,
tick fever, deerfly fever
• Worldwide; USA - low incidence ~100
cases/year
• Intracellular parasite – survive prolonged
periods in macrophage of RES (lymph
nodes, bone marrow, spleen, liver, kidneys)
F. tularensis: Lab Culture
• Fastidious, require enriched media
• Chocolate, MTM + antimicrobials
• BCYE (buffered charcoal-yeast
extract) – selective media for
Legionella
• Colonies may grow in 24 hours, or
5-7 days
• Specimen – ulcer scrape, lymph
node biopsy, sputum
• Collection and processing specimen
extremely hazardous:
– MO highly contagious (<100 MO)
– Penetrate skin and mucous
membranes
– Inhale aerosols
F. tularensis: Lab ID
• Best done by serology:
– No previous infection - antibody titer
≥1:160
– Patient with previous antibody - 4x
increase in paired serum (acute,
convalescent)
• Culture done under biological safety
cabinet (Biosafety Level-3 pathogen)
• Laboratory infection common
Tularemia: Transmission
• MO in wild animals, domestic animals,
birds, fish, ticks, water
• Acquired by:
– Direct contact infected animals
– Ingestion contaminated meat or water
– Inhalation
• Infectious dose low ~10
• A disease mostly in rabbits, rodents
• Most often transmitted to human by ticks
or deer flies fed on infected rodents, or
pet catching infected rabbit
Tularemia: Disease (Mode of Entry)
• 1) Ulceroglandular – through
skin abrasions:
– After ~48 hours, lesion occurs
at inoculated site, forms ulcer
– Headache, pain, fever, adjacent
lymph nodes enlarged
– If not contained - progress to
septicemia, pneumonia,
abscesses throughout body
– MO survives long periods of
time inside phagocytic cells
Tularemia: Disease
• 2) Typhoidal – ingestion
– Focus of infection in
mouth, throat, GI tract
– Systemic signs of fever,
toxemia in liver, spleen
• 3) Pneumonic – inhalation
– Most severe form of
disease
– Pneumonia with high
mortality rate (30%) if
untreated
F. tularensis:
Bioterrorism Agent
• CDC category A Select Biological Agent
• Risk to national security
• Spread person-to-person, or easily
disseminated
• Result in high mortality
• Lead to great public health impact and
public panic
F. tularensis: Treatment
and Prevention
• Streptomycin drug of choice, however not
readily available, high toxcity
• Gentamycin good alternative
• Attenuated, live vaccine protects against
inhalation form of disease; for at risk
(farmer, hunter, veterinarian, lab
microbiologist)
• Avoid reservoirs and vectors of infection
• Wear protective clothing, use insect
repellant (DEET) to reduce risk of tick, fly
bite
Case Study 5 - Francisella
• A 27-year-old man was mowing his field
when he ran over two young rabbits.
• When he stopped his mower, he realized
that two other rabbits were dead in the
unmowed part of the lawn.
• He removed all the rabbits and buried
them.
• Three days later he developed a fever,
muscle aches, and a dry, nonproductive
cough.
• Over the next 12 hours he got
progressively sicker and was transported
by his wife to the area hospital.
Case Study 5 - Francisella
• Results of a chest x-ray showed infiltrates
in both lung fields.
• Blood cultures and respiratory secretions
were collected, and antibiotics were
initiated.
• Blood cultures became positive with small
gram-negative rods after 3 days of
incubation, and the same organism grew
from the respiratory specimen that was
incubated onto BCYE agar.
Case Study - Questions
• 1. What test should be performed to
confirm the tentative diagnosis of
Francisella tularensis?
• 2. This infection was presumably acquired
by inhalation of aerosolized contaminated
blood. What are the most common sources
of F. tularensis infections and the most
common routes of exposure?
• 3. What are the different clinical
manifestations of F. tularensis?
Bordetella: Pertussis
• Endemic disease worldwide - >60 million
cases annually, >200,000 deaths
• Incidence reduced with Diphtheria,
Pertussis, Tetanus vaccine (DPT)
• Pertussis in USA:
– Inadequately immunized children (5 doses)
– Child not vaccinated due to parental fear of
vaccine-related neurologic toxcity
– Increase infections in adolescents and adults
(reservoir) due to waning immunity, no booster
vaccination
– Recent resurgence and outbreaks estimated ~3
million
Bordetella: Genera
• Three medically important species:
– B. pertussis – “severe cough”, pertussis
(whooping cough) in humans
– B. parapertussis – “resembling”, milder
pertussis in humans
– B. bronchoseptica – “trachea, septic”,
respiratory disease in animals;
occasional respiratory or wound
infection in humans
Bordetella pertussis: Lab
Culture
• No growth on common lab media:
– Additional nutrients needed
– Use of adsorbents to remove media substances
(fatty acids, sulfides) toxic to B. pertussis
• Bordet-Gengou media – glycerol, potato
infusion, albumin (binds fatty acids), up to
50% sheep RBCs
• Charcoal agar supplemented with 10%
horse blood, with or without cephalexin
• Usually 3-7 days for growth, 370 C
B. pertussis: Virulence Factors Toxins
• Pertussis toxin (PT):
– Increase in cAMP; increase respiratory
secrections, mucus leads to coughing stage of
disease
• Adenylate cyclase/hemolysin toxin:
– Increase in cAMP; inhibits phagocytes
– Protect MO during infection, early stages of
disease
• Tracheal cytotoxin:
– Due to bacterial peptidoglycan
– Killing, sloughing of ciliated cells
– Interferes with cell DNA synthesis, repair,
regeneration
– Disrupts normal clearance in RT
– Damage leads to “whooping” cough
B. pertussis: Virulence
Factors (Cell Surface)
• Filamentous hemagglutinin (FHA) –
attaches to host cell cilia, antibody made
against it protective (used for acellular
vaccine)
• Pertactin – adhesion, antibody made
against it protective (used for acellular
vaccine)
• Lipooligosaccharide - surface of the
bacteria, potent endotoxin activity
B. pertussis: Whooping Cough
• Infection by inhalation of infected droplets
or direct contact with secretions
• Highly infectious, 2º attack rate = 80%
• MO attaches to RT ciliated cells
• Incubation 1-2 weeks, MO multiplies
liberates toxins
Whooping Cough: Three Stages
• 1) Catarrhal stage:
– Resembles cold, mild cough and sneezing
– Large number MO spread through respiratory
secretions
– Last ~2 weeks
• 2) Paroxysmal stage:
– Rapid, consecutive coughs, rapid intake of air
(whooping sound)
– 40-50 daily paroxysms; vomiting, exhaustion
– Last 3-4 weeks
• 3) Convalescent stage:
– Symptoms gradually subside
– Last 3-4 weeks
– Complete recovery may need months
Whooping Cough
• B. pertussis rarely spreads to other sites,
but lot of cell damage may occur:
– Local tissue of RT
– Systemic damage by spread of exotoxin
• Secondary complications may occur
– Pneumonia
– Otitis media
– CNS dysfunction - seizures, encephalopathy
occurs ~10% cases; unknown cause
B. pertussis: Treatment and
Prevention
• Primarily supportive care
• Convalescence correlated with
regeneration of ciliated epithelium
• Erythromycin:
– Effective early stage of disease before toxins
– Reduces infectivity of patient
• DTaP vaccine – subunit acellular pertussis:
– PT toxoid, FHA hemagglutinnin, Pertactin
– Lower incidence of side-effects
– Children: five doses – 2, 4, 6, 18 months;
booster at 4-6 years
– Adolescents, adults: boosters – 12 years; 19-65
years
Class Assignment
• Textbook Reading:
• Chapter 18 Haemophilus and Other
Fastdious Gram-Negative Rods - Brucella,
Francisella
• Chapter 40 Zoonotic Diseases –
Tularemia, Brucellosis (pgs. 941-943)
• Chapter 32 Upper and Lower RTI –
Pertussis (pgs. 782-783)
• Key Terms
• Learning Assessment Questions
Case Study 6 - Bacillus
• A 56-year-old female postal worker sought
medical care for fever, diarrhea, and
vomiting.
• She was offered symptomatic treatment
and discharged from the community
hospital emergency department.
• Five days later she returned to the
hospital with complaints of chills, dry
cough, and pleuritic chest pain.
• A chest radiograph showed a small right
infiltrate and bilateral effusions but no
evidence of a widened mediastinum.
Case Study 6 - Bacillus
• She was admitted to the hospital, and the
next day her respiratory status and
pleural effusions worsened.
• A computerized tomographic (CT) scan of
her chest revealed enlarged mediastinial
and cervical lymph nodes.
• Pleural fluid and blood was collected for
culture and was positive within 10 hours
for gram-positive rods in long chains.
Case Study - Questions
• 1. The clinical impression is that this
woman has inhalation anthrax. What tests
should be performed to confirm the
identification of the isolate?
• 2. What are the three primary virulence
factors found in B. anthracis?
• 3. Describe the mechanisms of action of
the toxins produced by B. anthracis.
• 4. Describe the two forms of B. cereus
food poisoning. What toxin is responsible
for each form? Why is the clinical
presentation of these two diseases
different?