First Aid Microbiology 3 Flashcards
Condylomas
The limited list of rashes that may appear on palms of hands and soles of feet
What is this finding on CT angiography? (It has a correlate on gross pathology)
Tree bark aorta
Named for its appearance. This is a characteristic of tertiary syphilis, and is a form of ascending thoracic aortic aneurysm.
The pathology is due to invasion of the vasa vasorum (vessels of the vessel) that supply the thick muscular walls of the aorta.
What is going on in this infant with the displayed findings?
Congenital syphilis
Characteristic findings: Tooth abnormalities, saddle nose, perioral fissures, congenital deafness, high arched palate, and joint separation in feet and sometimes arms.
Treating syphilis
Always treat w/ penicillin
If Jarisch-Herxheimer reaction evolves, simple supportive care, NSAID analgesia, and potentially benzodiazepine sedation are all that will be necessary – it is self limited.
The two diseases caused by Legionella
Pontiac fever and Legionaire’s Disease
Pontiac fever is an acute, nonfatal respiratory disease. It causes a mild upper respiratory infection that resembles acute influenza. Pontiac fever resolves spontaneously and often goes undiagnosed.
Legionaire’s Disease is a severe pneumonia associated with hyponatremia, diarrhea, and neurologic symptoms that usually occurs in smokers and can spread in epidemic fashion.
Both are treated with fluoroquinolones or macrolides.
Why is pseudomonas SO BAD for CGD patients?
It is encapsalted as well as both catalase positive and oxidase positive
What is going on in this individual’s foot?
This is a not uncommon clinical scenario.
Diabetic neuropathy predisposes diabetic patients to these foot ulcers. These ulcers are then at risk for subsequent infections, and one of the major offenders is Pseudomonas aeruginosa. P. aeruginosa is so bluish-green that it can literally color the wound site, making it apparent that it should be at the top of your differential in cases like this.
P. aeruginosa is also the most common cause of osteomyelitis in diabetic patients.
What is the #1 most common and most feared infection in a burn patient?
Pseudomonas aeruginosa
Patient presents to primary care with the following presentation. They report that they are up to date on their vaccination status and have been quarantining at home. They have been spending much of their time enjoying their home built hot tub which was recently finished.
What is the likely causative organism? How could this have been avoided?
This is hot tub folliculitis
It is caused by Pseudomonas aeruginosa, and is prevented from developing in hot tubs and swimming pools by adding chlorine to the water.
Patient with PMH notable for diabetes presents with subacute hearing loss and painful inflammation of the external ear. The following is observed upon speculum exam.
The most likely causative organism for this patient’s disease shares a toxin with what other deadly bacterium? How does the toxin work?
This patient most likely has Pseudomonas aeruginosa infection of the external ear.
Pseudomonas shares a toxin with Corynebacterium diphtheriae which works by ribosylating EF2 and preventing protein translation in mammalian cells, leading to cell deaths
What can kill Pseudomonas?
Piperacillin (penicillinase-resistant penicillin)
Aminoglycosides
Fluoroquinolones
Patient presents with cellulitis of the forearm following being bitten by their pet dog at this site the previous day. What is the likely causative organism?
Pasteurella multocida (think Pasteur’s pet dog Ella)
Note that this could easily have been a cat too, but it would have to be a bite, not a scratch (like for Bartonella). The organism lives in the respiratory tracts of dogs and cats.
Like Pseudomonas, Pasteurella are catalase positive, oxidase positive, and encapsulated, making them a nightmare for patients with CGD.
It displays bipolar “safety pin” staining. Treat w/ amoxicillin-clavulonate.
On laboratory testing, the bacteria associated with an individual’s sputum sample are found to be lacking a component of peptidoglycan called muramic acid.
What is the likely causative organism for their pneumonia?
Chlamydophila pneumoniae
Lack of muramic acid in the cell wall is a defining characteristic of the chlamydia and chlamydophila species. It also means that they are resistant to penicillins.
So, treat w/ macrolides. If C. trichomatis, then assume N. gonorrheae is also present and give ceftriaxone too.
When dealing with gram intermediate bacteria with complex life cycles, the ___ form is always the infectious form and the ___ form is the noninfectious form which can divide.
When dealing with gram intermediate bacteria with complex life cycles, the elementary form is always the infectious form and the reticulate form is the noninfectious form which can divide.
Reticulate means to divide!
Organisms that stain w/ Giemsa
- Borrelia (Lyme)
- Chlamydia species
- Klebsiella granulomatis (Donovanosis)
- Amoebic parasites:
- Plasmodium species (Malaria)
- Pneumocystis jirovecii
- Babesia species (Babesiosis)
Subgroups of Chlamydia trichomatis and what they cause
- A-C: Blindness
- D-K: STI
- L1-L3: Lymphogranuloma venerium (LGV)
Patient presents w/ genital infection. You suspect a common STI based on the clinical history.
How do the characteristics of the discharge of the wound influence your suspicion of the causative organism?
If the discharge is thick and purulent, it is more likely to be Neisseria gonorrheae
If the discharge is watery, it is more likely to be Chlamydia trichomatis
Note that either way, your treatment regimen will assume that both organisms are present, since they are often co-infectious.
Patient presents with fever, nausea, and greenish, lumpy, “pea soup”-looking stools, as well as a diffuse rash shown below. Murphy’s sign was present on exam.
Biopsy and culture of fluid from the gall bladder is likely to grow what organism? How would you treat?
This is classic typhoid fever, characteristic of Salmonella typhi infection.
S. typhi colonizes the gall baldders of infected individuals, who may acquire the bacteria from contaminated water or undercooked seafood, and causes chronic mild cholecystitis as well as episodes of acute typhoid fever with “rose spot” rash, B symptoms, and “pea soup” stools.
Treat w/ fluoroquinolones.
Fever patterns and malaria species
Why is the vector for T. cruzi called the “Kissing bug”?
Because it likes to bite around the victim’s mouth while they are asleep at night.
It leaves faeces infected with T. cruzi in the wound, and they are pushed further in when the victim inevitably scrathces the bitten area. After a LONG time, often two or more decades, Chagas disease will start to set in.
The kissing bug is native to South and Central America, but is slowly making its way North with climate change.
How is Chagas disease diagnosed?
With active disease: Blood smear! T. cruzi can be easily visualized as these wispy fellows during an active infection.
With chronic disease: Serology and clinical symptoms are sufficient
What is going on in this endocardial biopsy?
Chagas cardiomyopathy
The lesion shown is a T. cruzi burrow. This patient is likely presenting with symptoms of heart failure due to dilated cardiomyopathy.
Female patient presents with grayish-white, malodorous discharge from the vaginal canal. Litmus testing shows pH of 6.5.
You suspect a paritcular diagnosis, and so you do a wet mount of exudate and see the following.
What is the diagnosis? How should you treat?
The image shows “clue cells,” shed epithelial cells from the vaginal vault covered in bacteria.
This confirms the diagnosis of bacterial vaginosis, caused by Gardnerella vaginalis.
Treat w/ metronidazole.
You are on a trip to West Africa. One day following a hike, someone on your tour group begins to feel unwell. They become somnolent and develop recurring fever, as well as prominent axillary and cervical lymphadenopathy. You suspect a certain diagnosis and rush to the hospital to obtain a blood smear, shown below.
What is the diagnosis and how was it acquired? Why does it cause mulitple recurrent fevers? How should you treat?
This is African Sleeping Sickness, caused by Trypanosoma brucei subspecies. It is endemic to Western and Southern Africa, and utilizes the Tsetse fly as a vector.
As the name implies, it causes coma, as well as recurrent fever and lymphadenopathy. The recurrent fever is due to antigen rotation by the protazoa.
Treatment is with Melarsoprol for CNS infection and Suramin for blood infection. Both are usually required, as the infection is usually in both locations.
“Gas gangrene” is characteristic of ____.
What mediates its pathology? How do you treat?
Clostridium perfringens
Secrete an alpha toxin that cleaves phospholipids, damaging cell membranes, including of red cells (hemolysis). This toxin characteristically produces a double-zone of hemolysis on blood agar.
Treat w/ penicillin G
