Mycobacteria etc Flashcards
What are the growth conditions for Mycobacterium sp?
Fastidious (have complex growth requirements)
Slow growing
Difficult to treat - hearty
What are the characteristics of Mycobacterium sp?
Acid fast (thick cell wall containing mycolic acid) - many branched lipids
Aerobic
Non-motile
Rod shaped
What are the human Mycobacterium pathogens?
Mycobacterium tuberculosis
Mycobacterium leprae
What are the characteristics of Mycobacterium tuberculosis (Mtb)?
Highly aerobic
Facultatively intracellular
Appear as white colony on Lowenstein-Jensen or Middlebrook’s medium
What are some characteristics of pulmonary tuberculosis?
Less than 10% develop TB disease upon infection
Some people are latent carriers - tuberculin positive in absence of disease
What is the tuberculin skin test?
It measures the immune reaction to Mtb as a measure of exposure to the bacterium
Protein isolate from Mtb are injected in the skin and the size of reaction measured
Positive is greater than a certain threshold
What are the risk factors associated with TB?
Immune status Alcoholism IV drug use Close contact with infected individuals Poor nutrition HIV status - TB is the leading cause of death for HIV infected individuals world wide
What does the primary infection of TB look like?
Inhale via respiratory droplets
Colonization of lung and uptake by phagocytosis into macrophages
Bacterial cell wall inhibits phagosome-lysosome fusion and virulence factors prevent phagosome acidification
Macrophages remain unactivated, bacteria may replicate uncontrollably inside without antigen presentation
Following macrophage burst, activation of lymphocytes leads to granuloma formation
What is a TB granuloma?
infected cells surrounded by macrophages and lymphocytes
Caseous necrosis a characteristic feature of TB granuloma
What does a latent TB infection look like?
Occurs after initial infection and dissemination
Absence of clinical symptoms and no shedding, non-transmissible
May last for long period time before reactivation (if ever)
What happens following a reactivation of a latent TB infection?
Granulomatous infection leads to necrosis, cavitation, release of bacteria into respiratory droplets
What are the clinical features primary or post primary pulmonary TB?
Fever, nausea, productive coughing Lymphadenopathy Pleural effusion Chest pain, dyspnea CXR: consolidation of lung (often upper), for patients with HIV/immunosuppressed consolidation may be mild/absent
What are the clinical features of primary progressive pulmonary TB?
Progressive nausea, loss of appetite, fatigue
Weight loss, muscle wasting
Productive cough with bloody sputum, dyspnea
What are some characteristics of extrapulmonary TB?
15-20% active cases and 50% of HIV cases
Spread to various organs, granulomas, multiple organ failure
CNS - tuberculosis meningitis
Bones and joints - Potts disease of the spine, osteomyelitis
Miliary TB - widespread
What are the prevention strategies for TB?
BCG vaccine
Novel immunotherapies in development: New ag, new platform, booster
What are some characteristics of M. leprae?
Granulomatous disease of URT, peripheral nerves
Progressive disease leads to characteristic lesions of the skin and deformation
Similar characteristics and morphology of Mtb
How is M. leprae transmitted?
person to person contact
respiratory droplets
ultimately unknown - maybe vector borne?
Armadillo only known non human reservoir
What does the initial infection of M. leprae look like?
Mild, often asymptomatic
Slow growing (5 year incubation period) symptoms may occur 20 years after infection
Hypopigmentation of the skin may be present
what is tuberculoid leprosy?
aka paucibacillary leprosy
milder form of the disease
large asymmetrical skin lesions - rash like, sensitive to touch
May progress to pain, muscle weakness, skin stiffness, dryness
Loss of nerve function = loss of skin sensation
What is borderline leprosy?
intermediate form of the disease (most common)
numerous lesions, may affect entire limbs leading to loss of function
This stage is unstable, may progress milder or more severe
What is lepromatous leprosy?
Most severe
begins with small symmetrical, diffuse lesions
progress with larger extensive lesions
Deformity of skin and limbs, loss of innervation and function
Eye involvement: glaucoma, photophobia, blindness
“saddle nose”
What are characteristics of mycoplasma sp. and ureaplasma sp?
Lack cell walls - resistant to many antibiotics
smallest known cell
parasites and commensals of vertebrate hosts
mycoplasma are common contaminants in laboratories
What are the human pathogens of mycoplasma sp and ureaplasma sp?
Mycoplasma pneumonia - atypical walking
Mycoplasma genitalium - PID, bacterial vaginosis
Mycoplasma homonis - PID
Ureaplasma urealyticum - non specific urethritis, perinatal complications
What are symptoms of Mycoplasma pneumonia?
Atypical walking pneumonia
Also caused by C. pneumonia, L. pneumophile
Typically mild illness: cough, fever, chills, chest pain, fatigue, muscle soreness
More severe symptoms: eye pain, ear pain, sore throat, rash, lymphadenopathy
Complications involve: CNS invasion (meningitis) haemolytic anemia (very rare)
What are characteristics of M. genitalium, M. homonis?
Thought to be normal flora of genital tract
Associated with PID, bacterial vaginosis
Probably sequelae of other disease and or antibiotic use
What are characteristics of ureaplasma urealytica?
Normal flora of urogenital tract
Associated with non-specific urethritis
Associated with complications during pregnancy: sterility, stillbirth, preterm labour, meningitis, pneumonia in pregnant women
What are characteristics of filamentous bacteria? What is an example?
Segmented filamentous bacteria
Gram (+), spore forming, rod shaped (filamentous) clostridia like
non culturable cells adhere to intestinal epithelium
Pro-inflammatory in animal models of infection
lead to inhibition of growth in pathogenic organisms
lead to increase incidence of autoimmune or inflammatory diseases
Candidatus arthromitus
What are characteristics of spirochaetes?
Spiral shaped, double membrane
anaerobic, or microaerophilic
Flagella run internally causing corkscrew motion
Gram (-) type cell wall but not classified by gram stain
What are human spirochaetes pathogens?
trepemona pallidum - syphilis
Borrelia burgdorferi - Lyme disease
leptospira sp- leptospirosis
What are some characteristics of trepomona pallidum?
small genome, simple metabolic requirements
anaerobic/microaerophilic
What are different subspecies of trepomona pallidum and what are the diseases they cause?
T. pallidum pallidum - syphilis
T. pallidum endemicum - bejel/endemic syphilis
T. pallidum carateum - pinta
T. pallidum pertenue - yaws
What is the clinical presentation of primary stage Trepomona pallidum?
Single painless chancre at site of infection
penile, cervical, oral, anal, vaginal: some difficult to detect
progress to ulcerative lesion
What is the secondary stage of Trepomona pallidum?
Diffuse non itchy rash typically palms and soles
May appear as wart like structures/condyloma
fever, headache, malaise
4-10 weeks following primary
What is the clinical presentation of latent stage Tremomona pallidum?
few to no symptoms
2-15 years (variable)
What is the clinical presentation of tertiary Trepomona pallidum?
Granuloma - soft noncancerous collection of bacteria, infected cells, macrophages
Neurological complications - seizure, dementia, meningitis
Cardiac complications - aortitis, aortic aneurysm leading to rupture and hemorrhage
How is treponema pallidum transmitted?
sexual, mucosal, fetal, contaminated blood products
What are other diseases caused by Treponema pallidum?
Bejel/endemic syphilis: infection of skin and tissue
Pinta: skin lesions hyperkeratotic
Yaws: ulcerative skin lesions, may progress to soft tissue destruction (esp bone/cartilage of the nose)
May all be resolved completely without antibiotic treatment
What is the common name of T. pallidum endemicum?
Bejel/endemic syphilis
What is the common name of T. pallidum carateum?
Pinta
What is the common name of T. pallidum pertenue?
Yaws
What is the most common etiology of Borrelia sp?
B. burgdorferi
What are the clinical features and complications of Borrelia sp?
Characteristic “bullseye” rash (erythema migrans)
Flu like symptoms
Bell’s palsy
Disseminated disease includes CNS invasion, arthritic symptoms, heart palpitations, extreme weakness
How is Borrelia sp. transmitted?
Deer ticks and black leg ticks, typically in late spring early summer
What disease is caused by Borrelia sp?
Lyme disease
What are the characteristics of post treatment Lyme disease syndrome?
Recurrent arthritis, arthralgia, neuralgia
Pathology unknown
Long term antibiotics not useful
10-20% experience PTLD
How is Leptospira sp. (Leptospirosis) transmitted?
Animal vector - contact with water, soil, food containing infected animal’s urine
“Mud fever” “swamp fever”
What are the clinical features of Leptospira sp (Leptospirosis)?
Phase 1: myalgia, fever, chills, headache
Phase 2: (Weil’s disease), meningitis, jaundice, renal failure
What are some morphological characteristics of Campylobacter sp?
Spiral shaped, Gram (-)
Oxidase (+)
Microaerophilic
What are the human pathogens of Campylobacter sp?
Campylobacter jejuni: gastroenteritis
Campylobacter coli: gastroenteritis
Campylobacter fetus: neonatal sepsis, meningitis
How are C. jejuni and C. coli transmitted?
contaminated poultry, unpasteurized milk. Most common food borne illness world wide.
Produces Cholera like entero-toxin
Grows well in avian bodies because max growth at 42C (avian body temp)
What are the clinical features of C. jejuni and C. coli?
Gastroenteritis lasting 24hours to 1 week (distinguishing feature that lasts more than 1 day)
Fever, abdominal pain, diarrhea, frequently bloody stool
May develop inflammation of the colon similar to C. diff infection (rare cause of pseudomembranous colitis)
Low risk of dissemination, reactive arthritis, low incidence of Guillian-Barre syndrome
What are clinical features of C. fetus?
Opportunistic pathogen in newborns
Causes spontaneous abortion in cattle/sheep
Only member of genus to cause septicaemia
May lead to infectious cardiopathy, invasion of respiratory tract, CNS (meningitis), septic thrombophlebitis, septic arthritis,
How is C. fetus transmitted?
Contaminated food, poultry, water
What are some morphological characteristics of Helicobacter pylori?
Gram (-), microaerophilic, acid-stable
A member of the normal flora of the stomach
What are the typical symptoms of a chronic infection of H. pylori?
typically asymptomatic
What are gastric/peptic ulcers and what are they associated?
Ulcers in the stomach/duodenum Associated with NSAID usage (1-4%) Dull sharp abdominal pain bleeding perforation of GIT MALT lymphoma, gastric cancer important complications
