Rocky mountain spotted fever, Human monocytic ehrlichiosis, and Human granulocytic anaplasmosis are all carried by the tick.

Staphylococcus aureus, which secretes toxins that damage the heart, and also exhibits fibronectin-binding.  The fibronectin binding comes more into play in the infection of already damaged hearts.

The most common cause of intact heart infection is intravenous drug use!

Staphylococcus epidermis endocarditis is found most often in IV drug users or people on IVs

Because S. epidermis lacks many of the virulence factors present on S. aureus, it needs a helping hand with entry into the body.  This is why it really only causes endocarditis in patients with IVs, catheters, or IV drug abusers.

Staph. epidermis is coagulase negative and not hemolytic.  It is a normal flora of the skin.

Because S. epidermis lacks many of the virulence factors present on S. aureus, it needs a helping hand with entry into the body.  This is why it really only causes endocarditis in patients with IVs, catheters, or IV drug abusers.

Strep. pneumoniae is inhibited by optochin.  Strep. viridians is not.

Both are alpha hemolytic gram (+) streptococci.

Strep. viridians is a low virulence bacteria.  It only causes endocarditis on previously damaged hearts.  Staph. aureus can infect both damaged and normal hearts. 

Strep. viridians normally enters with trauma or dental work, which is why people with damaged heart valves are placed on prophylactic antibiotics before seeing the dentist.  (Kate and her injured valve)

The deer tick, ixodes scapularis, is the vector for Human Granulocytic Anaplasmosis, found in north eastern and north central US between spring and fall.

Recall that ixodes ticks can also coinfect with lyme disease and babesiosis!

HME is found most commonly in south-central US.  It often produces a rash.

HGA is found in North central/ north eastern US and does not normally produce a rash.  It also presents more commonly in immunosuppressed people.

Are the following diseases caused by (+)ssRNA or (-)ssRNA viruses?

Yellow Fever

Dengue

Ebola

Lassa Fever

Yellow fever and Dengue are both caused by members of flaviviridae.  Flaviviridae are the only hemorrhagic fever-causing viruses that are (+)ssRNA.  All others are (-)ssRNA.  Therefore, Ebola (filoviridae) and Lassa Fever (arenaviridae) are both (-)ssRNA.

if something has good flavor/tastes good, this is a positive thing! (flaviviridae)

Yellow fever actually has a vaccine.

Dengue does not.  The reason is that a vaccine would make it more likely for someone to acquire dengue hemorrhagic fever, a life threatening illness.  If someone is exposed to dengue and develops an antibody response, they are protected only against the strain(s) they were exposed to.  If they are infected with a different strain, the antibodies can still cross-react and bind the virus without neutralizing it.  This will 'opsonize' the virus and hasten the uptake of the virus into cells, but not prevent them from undergoing their life cycle.  It's basically giving the virus a helping hand!  It can lead to much more severe disease which includes hemorrhage and hypotensive shock!

the Aedes mosquito transmits Dengue and Yellow Fever.

The aedes mosquito also carries the bunyavirus responsible for "rift valley fever"

Recall: the Anophiles mosquito is the vector for malaria.

Lassa Fever, caused by the (-)ssRNA virus Arenaviridae

It is found in africa with the aforementioned symptoms upon infection.  It is highly invasive to fetuses! Tx is with ribavirin.

Other potential viral fevers from africa would include "rift valley fever", "crimean congo hemorrhagic fever" and "hemorrhagic fever with renal syndrome"

Staph epidermis

IV drug abusers are also more likely to have endocarditis of the tricuspid valve than non-IV drug users.

Streptococcus viridians!

give prophylactic antibiotics before dental visits.  Also remember that S. viridians is not inhibited by optochin, whereas S. pneumoniae is.

Enterococcus!

enterococcus is PYR test positive, catalase(-), and grows in bile salts

Staphylococcus epidermis

Candida albicans

bartonella!

Bartonella quintana is spread by body lice

Bartonella Henselae is the cause of "cat scratch disease"

Streptococcus pyogenes (group A strep) can promote an immune response with antibodies that are cross reactive with the heart endocardium/valves.  The most commonly affected valve is the mitral valve, leading to mitral stenosis.

Streptococcus pyogenes and Enterococci are PYR test positive.

A bit on the PYR test:
Organisms possessing the enzyme L-pyrrolidonyl arylamidase can hydrolyze the disk substrate L-pyrrolidonyl-b-naphthylamide to release L-pyrrolidone and b-naphthylamide. Visual detection can be achieved by the addition of PYR/LAP Reagent .the active ingredient, p-dimethylaminocinnamaldehyde, combines with the end-product beta-naphthylamide to form a red Schiff base. A positive reaction is a yellow to red color change.

PYR disks are mainly used for the presumptive identification of group A beta-hemolytic streptococci (i.e. Streptococcus pyogenes). Among the commonly encountered b-hemolytic streptococci only S. pyogenes produces a positive reaction. The accuracy and rapidity of the PYR test allows for quicker reporting of results for those cultures screened for group A streptococci and can result in better patient care and treatment.

PYR disks can also be used for the presumptive identification of Enterococcus species. The most accurate presumptive identification of a catalase-negative gram-positive coccus as an Enterococcus strain is by demonstrating that the unknown strain is PYR and LAP positive and grows in 6.5% NaCl, and at 45C.

Coxsackie virus.

It is a naked, (+)ssRNA virus spread most commonly by the fecal-oral route.  it enters myocytes and triggers WBCs to attack the heart tissue!

Another cause of myocarditis could be the parasite T. cruzi, which causes Chaga's disease.

This is just a card to remind you that Lyme Disease is carried by the ixodes tick: Ixodes pacificus in the west, ixodes scapularis in the east.  It also carries babesia and anaplasma. 

Erythema migrans / bullseye rash

treat with doxycycline

Answer bacteria or virus:
Which typically causes otitis media?

Which typically causes sinusitis?

Otitis media is most commonly caused by the bacteria S. pneumoniae, H. influenzae or M. catarrhalis

Sinusitis is commonly of viral origin "RICRAMP".  You must see fluid in an xray of the sinuses to label it as sinusitis...

rhinovirus

influenza virus

coronavirus

RSV

adenovirus

metapneumovirus

parainfluenza virus

AKA: you do not normally treat sinusitis with antibiotics!

S. pyogenes contains the M-Protein virulence factor.  This functions to prevent opsonization by the complement factor C3b.  However, it also stimualtes antibody production that can lead to Acute Rheumatic Fever.  The antibodies that target M-protein are also cross-reactive with the endocardial tissue and heart valves!

Recall: Tx with penicillin can prevent ARF

C. diphtheriae must be infected with a lysogenic phage encoding the diphtheria toxin.  This toxin ADP-ribosylates the EF-2 protein, inactivating protein synthesis.  Recall: the eEF-2 protein promotes translocation of the tRNA from the A site to the P site during protein synthesis.   If diphtheria reaches the hear tis causes myocarditis.

In the throat and other passageways, a gray "pseudomembrane" of dead tissue may be observed, and this can actually promote death by asphyxia if in the respiratory tract.

prevention with the DTaP vaccine!

This patient likely has whooping cough cased by bordatella pertussis.  The small hemorrhages are from the intense caughing against closed vocal chords that raise intrathoracic pressure. 

Pertussis toxin ADP ribosylates G protein leading to increased adenylyl cyclase activity.

Tx= erythromycin

Px = DTaP vaccine

Describe the following as enveloped/naked and their genome structure:

Rhinovirus

Coronavirus

Influenza virus

Adenovirus

Rhinovirus = naked, (+)ssRNA

Coronavirus = enveloped, (+)ssRNA

Influenza virus = enveloped, (-)ssRNA

Adenovirus = naked, dsDNA

All respiratory viruses, "RICRAMP", are (-)ssRNA and enveloped

EXCEPT:

rhinovirus, coronavirus, adenovirus

"the naked rhino wears a crown"

and ADeNovirus has DNA in its name...

Rhinovirus and coronavirus

Rhinovirus is responsible for approximately 50% of cases of the common cold!

RSV can cause bronchiolitis

Bronchiolitis involves lymphocytic infiltration of the peribronchiolar tissue and necrosis of the bronchiolar epithelium, which leads to sloughing off of the epithelial cells.  This in turn causes obstructions which may lead to air trapping and atelectasis!

Upper resp. symptoms 1-3 days followed by lower resp. symptoms.

Parainfluenzavirus is associated with croup.

In croup there is narrowing of the subglottic area, this produces an inspiratory stridor and can be observed on x-ray as the "steeple sign"

(Side note: protection from resp. viruses like parainfluenza is from IgA in respiratory secretions)

hemagglutinin promotes viral attachment to cell receptors.  Therefore, anti-HA antibodies protect against viral infection.

Neuraminidase aids in viral release by cleaving sialic acid.  Therefore, anti-NA antibodies cannot protect against infection by the virus, but can help prevent its spread etc...

Antigenic drift involves point mutations and does not produce new serotypes.  It produces a slightly different form of the virus, and therefore people are not fully immune to it.

Antigenic shift involves reassortment and expression of a completely different strand of RNA.  It produces new serotypes that people have not been exposed to and can therefore lead to pandemics!  This occurs when two subtypes infect the same individual.  ex: H1N1 and H2N2 infect and release H1N2

non-respiratory symptoms appear first (myalgias, fever) and then a few days later respiratory symptoms follow.

Describe the different infection patterns between the normal influanzas and pandemic strains

The normal flu infects young and elderly individuals and typically in the winter months.  (most deaths occur in the elderly, most infections in the young children)

In pandemic strains that have undergone antigenic shift, ALL ages can be affected, and there are actually more deaths in young adults than elderly.  Additionally, these pandemics can occur at any time of year, not specifically in the winter.

elderly are more likely to have COPD, heart failure, Alcoholism, Immunodeficiencies, all of which are predisposing factors to the development of pneumonia.

(this is different from viral infections, like influenza, which are more common in children because of their lack of acquired immunity)

Bronchitis presents with the same symptoms as pneumonia, but does not show consolidation on an xray. 

Recall that all cases of typical pneumonia will show consolidation on xray.  (atypical pneumonia won't have purulent sputum, but will show interstitial infiltrates on xray)

Direct= pneumococcal vaccine.

as a child= a 7-type conjugated vaccine

as an adult= a 23-type polysacch. vaccine

Indirect= influenza vaccine

Because influenza infection can predispose to super-imposed bacterial pneumonia

What is the presentation of an atypical pneumonia?

What are the three most common causative organisms?

Atypical pneumonias present most commonly with fever, dry cough, and an interstitial/fibronodular pattern on xray.

Mycoplasma, legionella, and chlamydophila are the common causes of atypical pneumonia.  In fact, Mycoplasma pneumoniae is the 2nd most common cause of pneumonia after Streptococcus pneumoniae.