Group A Streptococcus (GAS) is the bacterium responsible for strep throat, an infection of the tonsils and throat. Standard treatment involves a ten-day course of antibiotics, typically penicillin or amoxicillin, which are highly effective against this bacteria. Despite this treatment, some individuals experience a return of symptoms while still taking the medication or shortly after finishing it. This raises the question of whether the original infection was never fully cleared (relapse) or if a brand new infection was contracted from an outside source (reinfection).
Distinguishing Between Relapse and True Reinfection
When strep symptoms return while a person is on antibiotics or shortly after completing the regimen, the cause is categorized as either a microbiological relapse or a true reinfection. A relapse occurs when the original strain of Streptococcus pyogenes was never completely eradicated from the throat. This persistence allows the bacteria to survive the antibiotic treatment, leading to a recurrence of symptoms once the drug levels in the body drop.
One biological reason for relapse involves the bacteria internalizing themselves within the cells lining the tonsils and throat. Common antibiotics like penicillin may not penetrate these areas effectively. While penicillin and amoxicillin are successful at killing bacteria in the bloodstream and tissue, they are less effective at reaching these intracellular hiding spots. Surviving bacteria can then re-emerge and cause a full infection once the antibiotic course is finished, which is a failure of the original treatment.
A true reinfection means the patient has been exposed to and infected by a completely new strain of Group A Strep from an external source. This can happen even if the original infection was successfully treated and the patient is still taking the medication. Since antibiotics only kill the bacteria and do not grant immunity, exposure to a new strain of GAS from a household member or close contact can lead to a fresh infection.
Being on antibiotics does not create a shield against contracting a new illness from the environment. The new infection is distinct from the first. Differentiating between relapse and reinfection usually requires a second strep test and a medical evaluation of the patient’s symptoms and exposure history.
Factors That Complicate Strep Treatment
The failure of an antibiotic course to eradicate Group A Strep can be due to several complicating factors, often unrelated to the bacteria’s susceptibility to the drug. One common reason for treatment failure is poor patient compliance, meaning the full ten-day course of medication was not completed. Stopping antibiotics early, even if symptoms have improved, allows resilient bacteria to survive and multiply, leading to a quick return of the illness.
The presence of other bacteria in the throat can interfere with the effectiveness of first-line antibiotics like penicillin. Some people host co-pathogens, such as Haemophilus influenzae, which produce the enzyme beta-lactamase. This enzyme can inactivate penicillin, shielding the Streptococcus bacteria from the drug and allowing the strep infection to persist.
While Streptococcus pyogenes has not developed widespread resistance to penicillin, resistance to alternative antibiotics, particularly macrolides like erythromycin and azithromycin, is a recognized problem. If a patient is allergic to penicillin and is treated with a macrolide, the treatment may fail if the infecting strain is resistant to that specific drug class. Local resistance patterns must be considered when prescribing alternative treatment.
Another complication is misdiagnosis, often involving a strep carrier experiencing a concurrent viral infection that mimics strep symptoms. Up to 25% of children may be asymptomatic strep carriers, meaning the bacteria is present but not causing illness. If a carrier develops a sore throat due to a virus, a strep test will still be positive. However, the antibiotics given will not treat the underlying viral cause, leading to the perception that the strep treatment has failed.
When Symptoms Persist or Return
If strep throat symptoms reappear while a person is taking antibiotics or shortly after the course is finished, the immediate step is to contact a healthcare provider. Do not simply restart the old medication or try to self-diagnose. The provider will need to determine if the issue is a treatment failure, a true reinfection, or a persistent carrier state with a new viral illness.
The first diagnostic step is to perform a new strep test to confirm the presence of Group A Strep bacteria. If the test is positive, the doctor may switch the patient to a different class of antibiotic, such as a cephalosporin or clindamycin. These alternatives are often more effective against persistent bacteria or those protected by co-pathogens. They may have better tissue penetration or are resistant to the beta-lactamase enzyme that interferes with penicillin.
To prevent the spread of the infection and minimize the risk of true reinfection, basic hygiene measures are important. The bacteria is easily transmitted through respiratory droplets. This includes frequent hand washing and avoiding the sharing of utensils, food, or drinks. It is also recommended to replace or disinfect items that have been in the mouth, such as toothbrushes.
Patients should remain home from work, school, or daycare until they have been on the new or adjusted antibiotic treatment for a minimum of 12 to 24 hours and their fever has resolved. This ensures they are no longer contagious, reducing the risk of transmitting the bacteria to others. Ultimately, only a medical professional can confirm the cause of the recurrence and prescribe an effective new course of action.