Casessss

[leviathan]

Any interesting infectious disease cases (real or fictitious) you can throw my way, Cole? We've covered all bacteriology and virology now, except for mycobacterium which is going to be covered at the end with parasites and fungi.

[Cole]

Hi Lev...great, ID rules.

1. 5 year old kid develops a week's worth history of fevers, malaise, coryza and fatigue. He goes to his family doctor who performs a nasopharyngeal swab which is positive for H1N1...he is started on oseltamavir. He slowly starts to get better over the next 48 hours, but on the third day he develops more fevers, shortness of breath and a productive cough. A chest x-ray shows a dense right lower lobe consolidation consistent with a bacterial lobar pneumonia.
a. What is the most likely pathogen causing this?
b. What put him at risk for getting this pneumonia?
c. Why didn't he get better more quickly with the oseltamavir?

2. A 50 year old Somali woman immigrated to Canada 3 years ago. She comes to the doctor complaining of a 5 month history of fevers, night sweats and a 30lb weight loss. Further history also reveals she has been having a cough for the past 2 months. A chest x-ray shows a left upper lobe infiltrate and fibronodular disease throughout his lung. A TB skin test is done and is negative.
a. What is the most likely diagnosis?
b. What puts her at risk for this diagnosis?
c. Since this diagnosis has been made, which other infectious disease must be tested for?

3. A 35 year old truck driver is a heavy smoker. He has had tooth pain in his bottom jaw for the past 3 months but hasn't done much about it. Over the last 3 weeks he's had problems with some R sided neck pain which seems to be getting worse and which is not comfortable in any position. He's been having fevers and night sweats. This continues on for the next 2 weeks until he finally seeks medical attention. Seeing the patient is febrile, the interne does blood cultures which return back for Fusobacterium necrophorum. A chest x-ray shows focal infiltrates resembling metastatic foci all over his chest.
a. What is the name of the syndrome he has?
b. Which other imaging investigation do you want to do?
c. Where did the Fusobacterial infection come from?

4. A 21 year old university student is noticed by his roommate to be acting funny. A normally intelligent, rational guy, he's all of a sudden disoriented, forgets who he is and is very verbally aggressive. 911 is called and the guy is taken to the emergency. The physical exam is negative, but he is febrile. He is sent for a CT head which is normal and then an MRI which shows bilateral temporal lobe inflammation. A lumbar puncture is done which shows about 10 white blood cells but >1000 red blood cells (which is the same in tube 1 and 4).
a. What is the most likely pathogen?
b. What other infection can cause bilateral temporal lobe cerebritis?
c. How do we treat said pathogen?

[leviathan]

Hi Lev...great, ID rules.

1. 5 year old kid develops a week's worth history of fevers, malaise, coryza and fatigue. He goes to his family doctor who performs a nasopharyngeal swab which is positive for H1N1...he is started on oseltamavir. He slowly starts to get better over the next 48 hours, but on the third day he develops more fevers, shortness of breath and a productive cough. A chest x-ray shows a dense right lower lobe consolidation consistent with a bacterial lobar pneumonia.
a. What is the most likely pathogen causing this?
b. What put him at risk for getting this pneumonia?
c. Why didn't he get better more quickly with the oseltamavir?

a. The most common cause of bacterial pneumonia after influenza is staphylococcus aureus. I think MRSA is actually starting to get pretty common too!
b. The influenza basically kills all the cilia in your upper airways, so you become more susceptible to other infections.
c. Tamiflu blocks neuraminidase and prevents secondary spread of an initial viral infection, so I guess if you've already got a widespread infection and your immune system is kicking in, then you're already on a course of convalescence anyway and it won't significantly alter the course.

2. A 50 year old Somali woman immigrated to Canada 3 years ago. She comes to the doctor complaining of a 5 month history of fevers, night sweats and a 30lb weight loss. Further history also reveals she has been having a cough for the past 2 months. A chest x-ray shows a left upper lobe infiltrate and fibronodular disease throughout his lung. A TB skin test is done and is negative.
a. What is the most likely diagnosis?
b. What puts her at risk for this diagnosis?
c. Since this diagnosis has been made, which other infectious disease must be tested for?

a. I might be way off here, but I'm thinking of either the mycobacterium avium complex or pnemocystis jiroveci. I'm not sure what the fibronodular disease is characteristic of, but the constitutional signs are making me think HIV.
b. An HIV infection that has progressed to AIDS due to a low CD4 count.
c. HIV???? I think I might be way off with this case.

3. A 35 year old truck driver is a heavy smoker. He has had tooth pain in his bottom jaw for the past 3 months but hasn't done much about it. Over the last 3 weeks he's had problems with some R sided neck pain which seems to be getting worse and which is not comfortable in any position. He's been having fevers and night sweats. This continues on for the next 2 weeks until he finally seeks medical attention. Seeing the patient is febrile, the interne does blood cultures which return back for Fusobacterium necrophorum. A chest x-ray shows focal infiltrates resembling metastatic foci all over his chest.
a. What is the name of the syndrome he has?
b. Which other imaging investigation do you want to do?
c. Where did the Fusobacterial infection come from?

a. Lemierre's?
b. Take a look at his internal jugular?
c. They are anaerobes that probably were seeding from a dental infection, like periodontitis.

4. A 21 year old university student is noticed by his roommate to be acting funny. A normally intelligent, rational guy, he's all of a sudden disoriented, forgets who he is and is very verbally aggressive. 911 is called and the guy is taken to the emergency. The physical exam is negative, but he is febrile. He is sent for a CT head which is normal and then an MRI which shows bilateral temporal lobe inflammation. A lumbar puncture is done which shows about 10 white blood cells but >1000 red blood cells (which is the same in tube 1 and 4).
a. What is the most likely pathogen?
b. What other infection can cause bilateral temporal lobe cerebritis?
c. How do we treat said pathogen?

Wow, you stumped me with this one. We learned about infectious diseases that caused encephalitis, but nothing specific as to which parts of the brain they affected or specific presentations. Without knowing any more about the case, I'd just go with what is common and guess that this could be a herpes simplex encephalitis, unless I knew about some sort of exposure to arboviruses. Treatment for HSE is acyclovir, ganclicovir, foscarnet, etc.

[leviathan]

did i at least get 1 of em right? hahaha

[Cole]

a. The most common cause of bacterial pneumonia after influenza is staphylococcus aureus. I think MRSA is actually starting to get pretty common too!
*****With seasonal flu, yes Staph aureus was a common cause of bacterial superinfection. Good answer! With the H1N1, we're seeing actually a lot of pneumococcal pneumonia actually.

b. The influenza basically kills all the cilia in your upper airways, so you become more susceptible to other infections.
********Yes, and also you get pneumonitis which puts one at higher risk of infection.

c. Tamiflu blocks neuraminidase and prevents secondary spread of an initial viral infection, so I guess if you've already got a widespread infection and your immune system is kicking in, then you're already on a course of convalescence anyway and it won't significantly alter the course.
*******Nice!


2. A 50 year old Somali woman immigrated to Canada 3 years ago. She comes to the doctor complaining of a 5 month history of fevers, night sweats and a 30lb weight loss. Further history also reveals she has been having a cough for the past 2 months. A chest x-ray shows a left upper lobe infiltrate and fibronodular disease throughout his lung. A TB skin test is done and is negative.
a. What is the most likely diagnosis?
b. What puts her at risk for this diagnosis?
c. Since this diagnosis has been made, which other infectious disease must be tested for?

a. I might be way off here, but I'm thinking of either the mycobacterium avium complex or pnemocystis jiroveci. I'm not sure what the fibronodular disease is characteristic of, but the constitutional signs are making me think HIV.
*****You're right with mycobacterium, but not avium complex!

b. An HIV infection that has progressed to AIDS due to a low CD4 count.
******She very well could have HIV as it is often associated with the infection this woman has. Have you guessed what the infection is yet?

c. HIV???? I think I might be way off with this case.
****Yes! Very good. Now what is the initial infection?



a. Lemierre's?
b. Take a look at his internal jugular?
c. They are anaerobes that probably were seeding from a dental infection, like periodontitis.
******Yes, yes and yes!! Very good.


Wow, you stumped me with this one. We learned about infectious diseases that caused encephalitis, but nothing specific as to which parts of the brain they affected or specific presentations. Without knowing any more about the case, I'd just go with what is common and guess that this could be a herpes simplex encephalitis, unless I knew about some sort of exposure to arboviruses. Treatment for HSE is acyclovir, ganclicovir, foscarnet, etc.
******Yes! This is herpes encephalitis. A relatively subacute course with personality change, a bloody CSF and temporal lobe inflammation is classic for this infection and yes you can use acyclovir to treat it.

[leviathan]

*****With seasonal flu, yes Staph aureus was a common cause of bacterial superinfection. Good answer! With the H1N1, we're seeing actually a lot of pneumococcal pneumonia actually.

Interesting! So are people coming into the ER with flu AND pneumonia presentation, or is it only ever the latter? Do you treat post-influenza pneumonia any differently than a garden variety pneumonia? For that matter, how do you normally treat someone that comes in with a pneumonia? Do you culture it or just treat it with generic antibiotics for what's the most likely agent? These are all the things we haven't learned yet, but I'm assuming it's either coming up in the last 2 semesters here or once I'm in clerkship.

******She very well could have HIV as it is often associated with the infection this woman has. Have you guessed what the infection is yet?

We covered mycobacterium tuberculosis yesterday, so now I figure that's what it is. Her skin test was negative probably due to a suppressed cellular immune response from AIDS.

*Yes! This is herpes encephalitis. A relatively subacute course with personality change, a bloody CSF and temporal lobe inflammation is classic for this infection and yes you can use acyclovir to treat it.

Interesting...that was a total shot in the dark, I didn't know it caused bilateral temporal lobe inflammation. How do you generally differentiate from all the different encephalitis-causing viruses that exist? We learned probably 15-20 of them but then really didn't cover how they differ from one another beyond epidemiology and what the viral family was.

[Cole]

Interesting! So are people coming into the ER with flu AND pneumonia presentation, or is it only ever the latter? Do you treat post-influenza pneumonia any differently than a garden variety pneumonia? For that matter, how do you normally treat someone that comes in with a pneumonia? Do you culture it or just treat it with generic antibiotics for what's the most likely agent? These are all the things we haven't learned yet, but I'm assuming it's either coming up in the last 2 semesters here or once I'm in clerkship.
****The only difference in the way you treat post-influenza pneumonia is that much of the time they require admission to hospital. When you treat pneumonia outside of the ICU especially it is generally treated empirically to cover the most likely pathogens. Sputum cultures are sometimes taken in non-intubated hospitalized patients and the coverage can be optimized for the sputum result. In the ICU, you have the liberty of getting a bronchoscopy with an alveolar lavage which allows you to get a bug and identify it. The trouble in the ICU is that many times peoples' endotracheal tubes get colonized with bacteria but they are NOT infected. In these cases, you have to look at other markers of infection (such as new x-ray infiltrate, fever, worsening respiratory status, increased sputum production etc.).

We covered mycobacterium tuberculosis yesterday, so now I figure that's what it is. Her skin test was negative probably due to a suppressed cellular immune response from AIDS.
*******So yes! MTB is the correct answer. Do you know which two organisms make up up the MTB complex? The skin test is probably negative secondary to AIDS, but remember something else: most TB we see in adults is reactivation TB. In other words, the person had a T-cell response which was keeping the TB in check, but which has now weakened so the TB is allowed to proliferate. A skin test is measuring T-cell response to TB-like antigens, so the very thing which is reduced in reactivation TB will result in a negative skin test as well.

Interesting...that was a total shot in the dark, I didn't know it caused bilateral temporal lobe inflammation. How do you generally differentiate from all the different encephalitis-causing viruses that exist? We learned probably 15-20 of them but then really didn't cover how they differ from one another beyond epidemiology and what the viral family was.
******It was an educated guess! Encephalitis is a very frustrating diagnosis because when people present with it and it's NOT herpes, you're not in an endemic region for certain arboviruses and you're not in a certain viral season, you often don't find a cause. Most of these patients will get an MRI as well as repeated CSF examinations. Herpes PCR is always sent off, but what they'll also do is send of tons of other tests to see if they can find a cause. Herpes and Bartonella can cause temporal lobe inflammation, and there may be some systemic signs associated with the other encephalitic viruses, but they are all non-specific. So in other words, most of these present the exact same way and they are microbiologic diagnoses, which can't always be made.

[leviathan]

We covered mycobacterium tuberculosis yesterday, so now I figure that's what it is. Her skin test was negative probably due to a suppressed cellular immune response from AIDS.
*******So yes! MTB is the correct answer. Do you know which two organisms make up up the MTB complex? The skin test is probably negative secondary to AIDS, but remember something else: most TB we see in adults is reactivation TB. In other words, the person had a T-cell response which was keeping the TB in check, but which has now weakened so the TB is allowed to proliferate. A skin test is measuring T-cell response to TB-like antigens, so the very thing which is reduced in reactivation TB will result in a negative skin test as well.

Ahh good point. No I'm not sure which two make up the MTB complex. We learned about 10 different types of mycobacterium so I'm not sure what you're referring to.

Herpes and Bartonella can cause temporal lobe inflammation, and there may be some systemic signs associated with the other encephalitic viruses, but they are all non-specific. So in other words, most of these present the exact same way and they are microbiologic diagnoses, which can't always be made.

Ahh bartonella too eh? I totally forgot about that. I've got to go back and start reviewing all of the bacteriology before our shelf exam.

[Cole]

Ahh good point. No I'm not sure which two make up the MTB complex. We learned about 10 different types of mycobacterium so I'm not sure what you're referring to.
*****Mycobacterium tuberculosis complex is made up of Mycobacterium tuberculosis and Mycobacterium bovis the latter which is often found because it is intrinsically resistant to pyrazinamide which is one of the first line therapies for TB.

[leviathan]

Ahh good point. No I'm not sure which two make up the MTB complex. We learned about 10 different types of mycobacterium so I'm not sure what you're referring to.
*****Mycobacterium tuberculosis complex is made up of Mycobacterium tuberculosis and Mycobacterium bovis the latter which is often found because it is intrinsically resistant to pyrazinamide which is one of the first line therapies for TB.

Ahh, all right. We learned about other Mycobacteria that cause pneumonia like M. kansasii. Is there any reason why only those two are considered part of a TB complex?