RHS23 - Respiratory Tract Infections 9 Flashcards
What infection does chlamydophila psittaci cause? What is the gram status of this bacteria? Describe this bacteria’s life cycle.
- Ornithosis (aka - Psittacosis or parrot fever)
- Gram Negative
- Same life cycle as C. pneumoniae except the elementary bodies exit cell by lysis
Describe the important structural components of chlamydophila psittaci
- Round with narrow periplasmic space
- No peptidoglycan in the cell wall, instead it contains:
- a weakly endotoxic form of lipopolysaccharide (LPS)
- Major Outer Membrane Protein (MOMP), a component unique to each species
- Outer membrane protein, common to all chlamydia
Describe the pathogenesis of Chlamydophila psittaci
- Transmitted via inhalation of excreta, urine, or respiratory droplets of birds
- First spreads to the mononuclear phagocyte system (MPS) of liver and kidneys, causing necrosis
- Then enters systemic circulation and seeds in the lungs causing lymphocytic inflammation, edema, macrophage infiltration, necrosis, and occasional hemorrhages
- Mucus can also plug the bronchioles causing cyanosis and anoxia
What are the clinical features of ornithosis?
- Headaches, high fever, chills, myalgia
- Nonproductive cough with lung consolidation
- CNS and GI involvement
- Hepatomegaly, splenomegaly, and follicular keratoconjunctivitis
Look for systemic involvement and bird exposure (even just meat handling)
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What family of virus causes Hantavirus Pulmonary Syndrome (HPS)? Describe their genome, shape, and sya whether or not their enveloped.
Bunyaviridae family
Spherical RNA virus with a lipid envelope consisting of 2 major glycoproteins
Which specific viruses (that we need to know) cause HPS? How is this disease transmitted and which populations are most effected?
Sin Nombre Virus in the western U.S. (particularly the 4 corners)
Transmission is primarily from inhalation of air contaminated with the virus from dehydrated rodent urine, excrement, and saliva.
Mostly found in rural areas, barns, outbuildings, and sheds.
When is HPS usually seen and why?
Mostly in the fall because that is when small rodents begin to inhabit human dwellings
What are the clinical features of HPS?
- Prodromal (3-5 days) - fever, headache, myalgia, vomiting, diarrhea. Often confused with viral gastroenteritis
- Cardiopulmonary (24-48hrs) - dyspnea, dry cough, pulm. edema, circulatory collapse
- Convalescent - significant diuresis, improvement in Sx
Describe the pathogenesis of HPS
- Virus enters vessel endothelial cells triggering an immune response
- Immune response damages the endothelium, increasing vascular permeability
- Clinical Sx are correlated with the development of specific antibodies to the virus
How is HPS diagnosed and treated? What is it’s prognosis?
- Easily mistaken for other illnesses. History of rodent exposure is crucial
- Lab diagnosis is done via RT-PCR for the viral RNA or ELISA fro IgM and IgG Abs against hantavirus and Sin Nombre Virus
There is no treatment for this infection and it has a 50% fatality rate. However, if the patient survives, chronic sequelae are minimal
