Strep Poker

Don't you hate it when you have a sore throat and half of your face falls off? That's the worst.source:

Don’t you hate it when you have a sore throat and half of your face falls off? That’s the worst!

Not unlike blizzards or public radio telethon week, sore throats happen. Sure, you can eat all the right things, get plenty of exercise, wear a hat when it’s cold, and dry your hair when it is wet, but the honest truth is that sore throats will still happen. Whether it was the 5 yr old at the bank who never covered his mouth when he coughed or the fact that you never washed your hands before leaving the birthday party at Chuck E. Cheese, as far as your immune system is concerned, it is only a matter of time before an infection sets in. Thankfully, a number of safe, easy, and reliable testing methods have been developed in recent years to aid clinicians in identifying these elusive, agents of infection and help patients arrive at a speedy recovery.

A Storm on The Horizon 

Morning is a cruel mistress

Morning is a cruel mistress

We can always feel it coming can’t we…that scratchy feeling in our throat, the dull twinge in our ears when we try to swallow. Oh yes, it’s sore throat time. Stayed out a little too late last night didn’t you? DIDN’T YOU?! Now just look what you did. That’s ok. Surprisingly, it is our body’s own immune response that produces the bulk of the drama when it comes to the really nasty cases of strep throat, especially in cases of neglected or under treated infections. Once the bacteria is recognized by our macrophages (the border patrol of our innate immunity) a cascade effect of cytokines, or cellular signals are released that bring about a variety of changes. Not only are white cells called to the site of the infection for a phagocytic schmackdown (when bacteria are either engulfed by macrophages or tagged by protective proteins for certain death by osmotic implosion), but inflammation is also induced by those white cells that are called to serve.

Blame those naughty antigens

The distinct molecular attributes of the streptococcus bacteria, or antigens, are largely to blame. The antigens (in this case, membrane bound proteins and carbohydrates that elicit an immune response) on the surface of the bacteria kick the immune system into overdrive, producing chemical cytokines or cellular signals that induce white blood cell action and inflammation (Phew…that’s technical!).This is what produces the characteristic soreness, swelling, and redness at the site of the infection. This not only makes swallowing difficult and painful but, lymph node glands can also begin to swell resulting in muscle ache in the neck. Fever and chills may also accompany the infection, as well as nausea and vomiting often in response to the persistent pain and discomfort. In the trade we like to refer to these as flu-like symptoms.

Sources of Infection

The bacteria can be spread from person to person by droplets from the cough or sneeze of an infected person. That’s right people, cover your pie holes! It is also possible to pick up the infection after touching contaminated surfaces like door handles or keyboards and then touching your eyes, nose, or mouth whereby the bacteria can easily gain access to the upper respiratory tract. Strep throat caused by S. pyogenes typically effects children or anyone with a weakened immune system. The infection can clear up on its own, however in some cases, S. pyogenes infections can lead to further complications, such as scarlet fever, toxic shock syndrome, and glomerular nephritis.

Behind the scenes

Typically when clinicians test for strep throat they are looking for the bacterium Streptococcus pyogenes. That is not to say that other bacteria as well as viruses are not just as capable of causing upper respiratory infections, but when it comes to the characteristically red, inflamed sore throats, in this region of the world anyway, it is S. pyogenes that usually gets called in for questioning. It is a handsome, frisky Group A, Beta-hemolytic strain of bead like bacteria that can produce mild to aggressive infections. “Beta hemolytic” refers to the ability of the bacteria to completely rupture (lyse) red cells on a culture plate, demonstrating a distinct, clear zone of red cell destruction. If you were to hold up an agar plate to the light it looks like someone took their thumb and rubbed the gel away where the Strep had been growing. Just think about the kind of damage something like that can do in your throat…ewww. That zone of hemolysis is a diagnostically reliable behavior that lab folks use to pick our star bad boy out of the line up.

Blinded by Science – Testing Principle

I hear lipstick models have really bad eyesight

I hear lipstick models have really bad eyesight

There is a bargain bin of strep testing kits out there in the biotechnology market. They all tend to work off the same testing principle of immunofixation whereby a sought after antigen (in this case the S. pyogenes membrane bound carbohydrate) is bound to specific antibodies within the testing media. There is also a color indicator in the mix that forms a unique complex which displays the presence of that antigen. The color change is then interpreted as a positive result. It is way less dramatic and not nearly as fun as mystery flavor koolaide. These tests are limited by sensitivity, meaning that an individual can in fact have a Strep infection that is below the detectable limits of the test. This is why it is a good practice for the physician to order a follow up culture for negative rapid strep screens.

Penicillin to the rescue!

As mean as sore throat infections can be they are often easily treatable. If they do not clear up quickly enough on their own we can typically zap them with antibiotics in the form of our favorite cell wall attacking antibiotics like penicillin, amoxicillin, or any taster’s choice cephalosporin on the market. Just be sure to take your full prescribed dose. Those microbes are sneaky and like to play dead. Under treating an infection is the perfect real world example of “what does not kill us, makes us stronger” except in this case it’s the Strep that can come back stronger. Of course, antibiotic resistance will have to wait for another article.

Stay classy my friends and never stop learning.

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