Got Strep Throat???

Is it sore throat season already? Well, sore throats can occur year round. The primary cause of a sore throat, or pharyngitis, is a bacterium known as Streptococcus pyogenes. The primary infection of Streptococcus pyogenes is a strep throat or tonsillitis. A painful, red throat with white patches on your tonsils is characteristic of pharyngitis, otherwise known as strep throat.  It is usually accompanied by swollen lymph nodes, fever, and headache.  Occasionally nausea, vomiting, and abdominal pain also accompany it. The suppurative sequelae of the initial infection are sinusitis or otitis media. Other nonsuppurative sequelae of S. pyogenes are scarlet fever. The frequency of Streptococcus pyogenes for the general population is 15-35%. Streptococcus pyogenes is classified as Group A streptococcus. Group A streptococci typically have a capsule composed of hyaluronic acid and are beta-hemolytic, which is characteristic for Streptococcus pyogenes. Beta-hemolytic streptococci produce a toxin that forms a clear zone of hemolysis on blood agar, demonstrating its ability to destroy red blood cells.  This hemolysis is attributed to toxins formed by Group A streptococci called streptolysins.  Streptolysins can destroy not only red blood cells, but also the white blood cells responsible for fighting off bacteria and disease, as well as other body cells.

The identification of Streptococcus pyogenes is to make a presumptive decision based on the gram stain and colony morphology. After, a PYR test can easily be performed. If the test is positive, it can be presumptively identified as Streptococcus pyogenes. Further tests such as a Bacitracin disk are performed where the expected results are to be sensitive to the organism. A quick test that can be performed in a clinic setting rather than the clinical laboratory is the Quick Vue Dipstick Strep A Test. It is a rapid lateral-flow immunoassay where the extracted antigen attaches to the antibody to the step A colored particles. The complex then migrates through the membrane and attaches the antibody to the strep A where the test line will produce a pink to purple color. On the control line, the complex reacts with the antibody, or protein A, to produce a blue color. To report a positive test, it must be reported as “Positive for Group A Streptococcus antigen.” To report a negative test, it must be reported as “Negative for Group A Streptococcus antigen.” For an invalid report, it must be reported as “Invalid Group A Streptococcus antigen test result. Possible interfering substance present. Please submit another sample if clinically indicated.” The advantages to this assay are that it has good specificity where the patient can be treated sooner, and it is faster than a culture. The disadvantages to this assay are that it has lower sensitivity than a culture and it does not detect other infections due to other groups of streptococci.

According to a CDC report dated April 3, 2008, approximately 9,000-11,500 cases of invasive GAS disease (3.2-3.9 per 100,000 population) occur each year in the United States. More than 10 million noninvasive GAS infections (primarily throat and superficial skin infections) occur annually. The best way to avoid strep throat is to avoid close contact with someone who is already infected with strep. It may also be helpful to reduce stress, get plenty of rest, and fortify your body's natural defenses. Frequent hand washing can help prevent infection as well.

Found a pretty tough quiz that include some questions from my blog but also from our respiratory tract infection lectures. Check it out!!!

Respiratory Infection Quiz!