by Z. Esra Ilhan

We all know the feeling…struggling to swallow anything, even the sip of water necessary to get down those painkillers that will ease the terrible headache and fever. If you are experiencing these symptoms but do not have a runny nose you are probably a victim of “strep throat”. The most common cause of strep throat is a bug called Streptococcus pyogenes. It is one of the puss producing (or if you prefer the less icky scientist-word, pyogenic) bacteria. S. pyogenes and its other Streptococcus relatives make themselves at home on your skin and in your intestines, nose, mouth or throat.

These creatures operate like double agents. Usually, under the watchful eyes of white blood cells, you don’t even notice that they are there. However, when your immunity system weakens, they strike. S. pyogenes releases toxins in large quantities, toxins that cause the inflammation in your throat that hurts. One of its kin, Streptococcus pneumoniae, resides in the upper respiratory tract. When it hitchhikes through the bloodstream to other body parts in a person with a weakened immune system, it can cause pneumonia (in the lungs) and meningitis (in the nervous system).

S. pyogenes is not only guilty of causing strep throat but also more severe conditions, such as scarlet fever, flesh-eating disease, toxic shock syndrome and cellulitis (not cellulite).  The father of medicine, Hippocrates was credited for the oldest record of Streptococcus as flesh-eating bacteria. Of course Streptococcus doesn’t eat the flesh by taking small bites; it kills the soft tissue with its toxins in an (sometimes successful) attempt to get all the way through to the bloodstream.

Children, elderly and immune-compromised individuals are at greater risk for developing strep infections. However, no one is fully exempt. Sharing your mucus or saliva is the most common way of spreading strep. And if you share either of these things with a puppy, well, they can get strep too.

Because humans share both mucus and saliva liberally (albeit often unintentionally) strep spreads readily, especially in schools, where close contact and a certain drooliness cannot be avoided. As a result, strep is the second most common reason that children get antibiotics. Nor is any of this very new. The very first infection a commercial antibiotic was ever used for was, you’ve got it, strep.

Hildegard Domagk, the daughter of Gerhard Domagk, became infected with Streptococcus after pricking her hand with a knitting needle. At the time, blood infections with strep were lethal. Hildegard became critically ill. Luckily her father Gerhard, a successful German physician, was testing antimicrobial properties of a dye called Prontosil on mice infected with Streptococcus. Two Bayer chemists who worked with Domagk, Josef Klarer and Fritz Mietzsch, suggested using Prontosil as an antibiotic. Desperate to save his daughter, Gerhard injected a high dose of Prontosil into Hildegard. Miraculously, she recovered rapidly. Prontosil not only saved Gerhard’s daughter’s life but also brought him a Nobel Prize. In 1936, a year after Gerhard published his report, the treatment of Eleanor and Franklin Roosevelt’s son with Prontosil led to a boom in the use of sulfonamide drugs like it to treat bacterial infections.

We all have a wild cousin and so know that sharing a common ancestry with your cousin does not mean you share their personality. Within the clan of Streptococcus lives an unambiguous good guy. S. thermophilus has deactivated virulence genes. As suggested by its name, S. thermophilus likes hot temperatures (~500C) and leaves those humans who happen upon it in peace.

If you are looking to find S. thermophilus, you can find it in a cow gut or, for the less adventurous, in a yogurt cup. The average Western diet includes about 1000000000000000000000 cells of S. thermophilus per year. A lactic acid bacterium, S. thermophilus and its Lactobacillus buddies give the Greek yogurt its distinctive taste and texture. Yogurt is not the only dairy product S. thermophilus helps produce; it is also used as a starter culture for a variety of cheeses including cheddar, mozzarella, Swiss, Parmesan and many others. It has the ability to digest proteins in the milk as well as produce acid through fermentation. Moreover, S. thermophilus allows the curding of low-fat versions of mozzarella and cheddar.

S. thermophilus is considered a probiotic culture. Consuming it helps you soothe gastrointestinal problems like diarrhea, a nasty side effect that often occurs after treatment with antibiotics. Because probiotics help recover normal gastrointestinal flora zapped by the antibiotics, doctors recommend taking probiotics along with antibiotic treatment.  So the next time you take antibiotics for your strep throat, don’t forget to consume strep’s kinder, gentler cousin S. thermophilus in your favorite yogurt.


1. Goh, Y. J., Goin, C., O’Flaherty, S., Altermann, E., & Hutkins, R. (2011). Specialized adaptation of a lactic acid bacterium to the milk environment: the comparative genomics of Streptococcus thermophiles LMD-9. Microbial Cell Factories, 10.

2. Wong, S.S.Y., Yuen, K.Y., (2012) Streptococcus pyogenes and re-emergence of scarlet fever as a public health problem, Emerging Microbes and Infections, 1.

3. Chemical Heritage Foundation (Gerhard Domagk) Retrieved October, 2013, from

About the Author

Z. Esra Ilhan is a Microbiology PhD student at Arizona State University, working in the laboratory of Rosa Krajmalnik-Brown. Originally from Turkey, Esra first completed a Master of Science degree in Environmental Sciences at Iowa State University before attending ASU. Her current research focuses on gut microbiota and host energy metabolism after surgical weight-loss procedures. She uses metabolomic and metagenomic approaches to understand how microbes contribute to host energy balance.