Miscellaneous Bacteria Flashcards
Rickettsia rickettsii are [size, Gram stain, shape, location]
Small Gram-negative coccobacilli that are obligate intracellular
(Does not visualize well with gram stain; use Giesma stain)
What does Rickettsia rickettsii cause?
Where is this most common?
How is it acquired?
What is the clinical presentation?
Rocky Mountain spotted fever
Most common in central and mid-Atlantic states
Acquired through tick bites
Triad of fever, rash, and headache
Coxiella burnetii are [size, Gram stain, shape, location]
Small Gram-negative coccobacilli that are obligate intracellular
(Note: Does not take up gram stain well, can also be considered “gram indeterminant”)
What does Coxiella burnetii cause?
What is the clinical presentation?
Which animal is it found in?
How is it spread to humans?
Q fever
Presents as fever, pulmonary infiltrates, and NO rash
Harborbed by sheep, especially placenta and fetal membranes
Spread by aerosols during the birth of lambs or other animals and through ingestion of unpasteurized milk
Bartonella henselae are [size, Gram stain, shape, location]
Bartonella henselae are tiny Gram-negative bacilli that are NOT obligate intracellular
What does Bartonella henselae infection cause?
- Bacillary angiomatosis (immunocompromised individuals, especially with AIDS)
- Cat scratch disease (enlargement of one or more lymph nodes following a cat scratch or bit)
What is the life cycle of Chlamydia spp.?
Extracellular elementary body (EB) which is metabolically inactive
Intracellular reticular body (RB) which is metabolically active
What type of disease does Chlamydia trachomatis cause?
Sexually transmitted diseases
What do Chlamydia pneumoniae and Chlamydia psittaci cause?
Pneumonia
What is unique about Mycoplasma?
Smallest organisms that can be free-living in nature and self replicating but require a media supplemented with essential components
Mycoplasma plasma membranes contain sterols which are obtained from eukaryotic cells or growth media
No cell walls so do not Gram stain
What do Mycoplasma have in their plasma membranes that other bacteria lack?
Sterols (obtained from eukaryotic cells or growth media)
What disease does Mycoplasma pneumoniae cause?
How?
Community-acquired pneumonia (“Walking pneumonia”); Symptoms are often less severe than a chest x-ray might suggest
Tightly adheres to cilia and microvilli on the surface of the bronchial epithelium
Borrelia burgdorferi are [shape, transmission, disease caused]
Borrelia burgdorferi are spirochetes transmitted to humans through contact with ticks and cause Lyme disease
Which bacteria causes Lyme disease?
What is the classic presentation of Lyme disease?
Borrelia burgdorferi
Erythema migrans: annular rash with central clearance at site of tick bite
Occurs in three stages and may present with rash, fevers, arthralgias/arthritis, arrhythmias, or neurologic findings
Treponema pallidum are [shape, disease caused]
Treponema pallidum are spirochetes that cause syphilis
Which bacteria causes syphilis?
What are the stages of syphilis?
Treponema pallidum
- Primary syphilis: chancre (ulcerative lesion on genitalia)
- Secondary sphilis: rash usually on soles and palms
- Tertiary syphilis: may occur months to years later and has variety of manifestations
Leptospira interrogans is [metabolic, shape]
Leptospira interrogans is an aerobic spirochete
In which animal species does Leptospira interrogans causes infections?
How is Leptospira interrogans transmitted to humans?
Rats, cattle, dogs
Transmitted to humans after exposure to water contaminated with animal urine (through ingestion, cuts in skin, exposure of conjunctiva)
Symptomatically, how would you distinguish between a fever caused by Rickettsia rickettsii and one caused by Coxiella brunetti?
A fever caused by Rickettsia rickettsii is likely to have a rash
A fever caused by Coxiella burnettii will not have a rash
Which groups are more likely to contract a Leptospira interrogans infecton?
People who engage in water sports
The bacteria thrive in animal urine; swimming in water that is contaminated can cause disease
Are mycobacterium gram positive or gram negative?
Structurally, all mycobacteria are gram positive
However, their cell envelopes have high lipid content; this prevents them from taking up gram stain and makes them highly resistant to beta-lactam antibiotics
Mycobacterium tuberculosis are [gram stain, shape, location, metabolism, relevant morphology]
Mycobacterium tuberculosis:
- Gram (+) structure, but does not gram stain
- Use acid-fast method
- Bacillus
- Facultative intracellular
- Obligate aerobe
- Very slow growth
Where in the body does M. tuberculosis proliferate?
Within macrophages
Typically in the lungs
- Primary infection more often affects the right lobe
- Disease is associated with cavities in the apex of the lung
What is Pott’s disease?
Tuberculosis that has spread to the spine
- Arthritis of intervertebral joints
- Damage to soft tissue
Describe the clinical presentation of miliary tuberculosis
Classified as both pulmonary and extrapulmonary
- May follow primary infection or reactivation
- Very severe; the host is basically not responding at all to the pathogen, and it disseminates widely
- Systemic infection
- Fever, weight loss, night sweats
- Cough may or may not be present
- Commonly causes….
- Hepatomegaly
- Splenomegaly
- Lymphadenopathy
- Miliary reticulondular (snowstorm) pattern on chest x-ray
- May also cause…
- Bone involvement
- Pott’s disease (spine)
- CNS involvement
- Meningitis
- Tuberculoma (brain abscess)
- Bone involvement
Which groups have an increased risk of mortality from M. tuberculosis infection?
Groups without a long history of urbanization
Ex: Native americans, Eskimos
How is M. tuberculosis treated?
Latent infection
- 9 months of Isoniazid
Active disease: 6 month, multi-drug regimen
- 2 months of RIPE
- Rifampin
- Isoniazid
- Pyrazinamide
- Ethambutol
- Follow with 4 months of RI
- Rifampin
- Isoniazid
Mycobacterium leprae are [gram stain, shape, location, metabolism, relevant morphology]
- Gram (+)-like cell envelope
- But do not take up gram stain, and stain acid-fast
- Bacillus
- Obligate intracellular
- Within macrophages
- Facultative aerobe
- Grows very slowly
- Doubling time = 11-13 days
- Loves to grow in cooler places
- Well adapted to human host
- Lost ~1/3 of M. tuberculosis genes
Describe the clinical presentation of tuberculoid leprosy
- Triggers an intense, cell-mediated response
- Involves Th1 (a type of helper T-cell)
- Th1 stimulates antibody production, which eventually promotes phagocytosis by macrophages
- Very few bacterium are seen in tissues
- Instead, they live in macrophages
- Causes non-caseating granuloma
- Skin legions are well-defined
- Hyperpigmented, anesthetic, macular
- Raised edges, depressed center, hairless
- Enlargement of large peripheral nerves
- May become palpable
- Ulnar, peroneal, greater auricular
- Neuronal damage
- Muscle atrophy
- Contracture
- Loss of sensitivity
- Leads to more trauma, infection, and further damage
Describe the clinical presentation of lepromatous leprosy (“classic leprosy”)
- No cellular immune response
- Involves Th2 (a type of helper T-cell)
- Th2 helper T-cells do not release antibodies; they are more effective at clearing extracellular bacteria; they are basically useless against M. leprae, which is an intracellular pathogen
- Many bacteria are present in the tissue
- Not contained in macrophages (thanks a lot, Th2)
- Skin legions are poorly demarcated
- Can be in any shape
- Usually raised
- Usually form on cooler areas of the body
- Face, ears, wrists, elbows, butt, knees
- Leonine facies
- Thickened, folded skin of the forhead and face
- Saddle nose
- Septal perforation leading to nasal collapse
- Neuronal damage
- Decreased peripheral sensitivity
- Symmetrical in extremeties
- Leads to trauma that goes undiagnosed
- Secondary infection leads to loss of digits
How does M. leprae cause neuronal damage?
M. leprae kills Schwann cells directly
This leads to demyelination of peripheral neurons, which can cause nerve damage
How is leprosy treated?
- Tuberculoid: Dapsone + Rifampin
- Lepramatous: Dapsone + Rifampin + Clofazimine
A patient presents with an infected ulcer on his hand.
He says that he was bit by his tropical fish while he was cleaning the fish tank last weekend.
Which bacteria do you think is causing the infection?
Mycobacterium marinum
Infection typically occurs after contact with fish, fish tanks, or salt water
Causes an ulcer in soft tissue
A “snow storm pattern” on chest radiography is characteristic of which disease?
Tuberculosis, especially miliary tuberculosis
One of your elderly, alcoholic patients is very hill;
She has a severe cough, fever, and night sweats. Her chest X-ray is shown below
What is significant about her X-ray?
What is the most likely cause of your patient’s infection?
How would you treat the infection?
The X-ray exhibits a “snowstorm” pattern characteristic of miliary tuberculosis
She should be treated with 2 months of rifampin, isoniazid, pyrazinamide, and ethambutol, followed by 4 months of rifampin and isoniazid (the typical treatment for tuberculosis)
Is this a picture of tuberculoid leprosy or lepromatous leprosy?
How do you know?
Lepromatous; the pink marks are the acid-fast M. leprae taking up carbol fucshin
May bacteria are located in the tissues, a characterisitc of lepromatous leprosy
