USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 22-year-old woman comes to the emergency room with a fever, chills, and abdominal pain that began this morning. Two months ago, she was diagnosed with a herpes simplex genital infection and treated with valacyclovir. She is sexually active and has multiple sexual partners. She uses condoms inconsistently. Her last menstrual period was four weeks ago. She has not received the human papillomavirus vaccination series. Family history is noncontributory. Temperature is 38.3°C (100.9°F), pulse is 100/min, respirations are 20/min, and blood pressure is 120/75 mmHg. BMI is 32 kg/m2. Speculum examination reveals mucopurulent discharge with a friable, erythematous cervix. Cervical motion tenderness and right adnexal tenderness are present on bimanual examination. An external genital examination is non-contributory. Which of the following clinical sequelae is likely if this patient does not receive appropriate treatment?
The word Neisseria came from Neisser Albert, a German physician who discovered it, while gonorrhea is from the Greek words “gonos” which means "seed", and “rhoe” which means "flow", meaning "flow of seed", an illustration referring to the penile purulent discharge, which was mistakenly thought to be semen in infected males.
Now, a little bit of microbe anatomy and physiology. N. gonorrhoeae is a gram-negative bacterium, because its cell wall has a thin peptidoglycan layer and so it doesn’t retain purple dye used during Gram staining.
Instead, like any other Gram-negative bacteria, N. gonorrhoeae stains pink with safranin dye.
N. gonorrhoeae typically live in pairs called diplococci, stacked side to side, so the pair looks like a coffee bean.
They are also non-motile, non-spore forming, and obligate aerobes, which means that they absolutely need oxygen to grow.
Finally, they’re catalase and oxidase positive - which means they produce both these enzymes.
N. gonorrhoeae grows on a special chocolate medium called Thayer-Martin agar, which mainly consists of sheep blood... err, yum?
Some antimicrobials, like vancomycin and nystatin are usually added to the Thayer-Martin agar, to inhibit the possible growth of undesired bacteria or fungi, and maximize the growth of Neisseria species.
However, other Neisseria species, like N. meningitidis, have the same properties.
So the maltose fermentation test is done to differentiate the two.
To check for this, a pure sample from the culture of the suspected bacteria, is transferred to a sterile tube containing phenol red-maltose broth, which is then incubated at 36 degrees Celsius for 24 hours.
But this bacteria has a ton of other virulence factors, which it uses to attack and destroy host cells, and also to evade the immune system.
First, N. gonorrhoeae has pili, these little thread-like extensions radiating from the bacterial surface.
The pili help N. gonorrhoeae attach to a host’s mucosa surface.
Also, they help bacteria get physically connected with each other, making what’s known as a conjugation pilus, which is a hollow tiny rod, through which bacteria can swap genetic information back and forth - including antibiotic resistance genes.
Interestingly, N. gonorrhoeae pili are made of antigenic proteins which can vary with every infection – what’s known as phase variation.
Ok, so normally, when a certain bacteria causes an infection, the immune system keeps memory of the bacterial antigens configuration.
So if the same bacteria infects again, the immune system remembers it and quickly makes specific antibodies against it.
Pili aside, other virulence factors of N. gonorrhoeae include toxins.
The very important one is IgA protease, a toxic protein that this bacterium uses to destroy Immunoglobulin A – IgA.
IgA helps with bacteria opsonization - meaning it tags the bacteria so that neutrophils can recognize and destroy them.
So IgA protease neutralizes the first line of mucosal defense!
However, N. gonorrhoeae releases catalase, which breaks down H2O2.
The neutrophil eventually becomes too full, bursting open, and letting out a lot of bacteria in the bloodstream, which is known as gonococcemia.