The bacteria Staphylococcus aureus is a common organism often found living harmlessly on the skin and in the upper respiratory tract of healthy individuals. When this bacterium causes a throat infection, known as staphylococcal pharyngitis, the diagnosis can be easily overlooked. While many sore throats are caused by viruses or Streptococcus bacteria, a Staph infection in the throat is possible, though it is a significantly less frequent cause of pharyngitis. Recognizing this possibility is important because it requires a different approach to diagnosis and treatment compared to prevalent causes like Group A Streptococcus.
The Organism and Transmission
Staphylococcus aureus is a Gram-positive bacterium, a member of the normal human microbiota, meaning it frequently colonizes the body without causing illness. This organism is commonly found in the nose and on the skin, but the throat (oropharynx) is also a recognized site of colonization. Estimates suggest that up to 30% of the population carries S. aureus in their nose, and a high percentage also carries it in their throat.
Colonization is the presence of the bacteria in the throat and is generally asymptomatic. An active infection begins when this colonization shifts to an invasive process, often when the body’s local defenses are compromised. This bacteria is considered an opportunistic pathogen, meaning it takes advantage of a weakened state to cause disease.
Transmission occurs through direct contact with a carrier or an infected person, or through contact with contaminated objects. In pharyngitis, the infection frequently arises from the person’s own colonized bacteria. The bacteria may multiply and invade the tissue following a preceding viral illness that has irritated the mucosal lining. The throat can sometimes harbor S. aureus even when the nose is clear, which is why screening procedures for carriers target both locations.
Clinical Presentation
The symptoms of staphylococcal pharyngitis often closely resemble those of other, more common causes of a sore throat, making a diagnosis based on visual inspection or patient history alone unreliable. Patients typically experience a sore throat, pain when swallowing, and often a fever. General symptoms such as headache, body aches, and tender, swollen lymph nodes in the neck may also be present.
The difficulty in diagnosis lies in the symptom overlap, especially with Group A Streptococcus (Strep throat), which is the most frequent bacterial culprit. Both infections can present with a red throat and, in some cases, enlarged tonsils with white spots or exudates. Unlike some viral causes, staph throat is often characterized by a sudden onset of symptoms.
Because S. aureus is not the primary suspect for pharyngitis, it is often missed when only a rapid Strep test is performed. Rapid antigen detection tests and standard throat cultures are typically geared toward identifying Group A Streptococcus. If the rapid Strep test is negative, the illness is often presumed to be viral, and no further bacterial testing is done.
Identifying S. aureus as the cause requires a specific throat culture. Without laboratory confirmation, a Staph infection can be misdiagnosed or go untreated with the correct medication. This diagnostic challenge highlights the necessity of microbiological testing when severe bacterial pharyngitis is suspected, but initial common tests are inconclusive.
Treatment and Management
The initial step after suspecting bacterial pharyngitis is to obtain a definitive diagnosis through a laboratory culture. This is important for Staph infections because the correct antibiotic choice depends on the specific strain. Once S. aureus is confirmed, the laboratory performs susceptibility testing to determine which antibiotics will be effective.
A concern in treating S. aureus is the high prevalence of antibiotic-resistant strains, most notably Methicillin-resistant Staphylococcus aureus (MRSA). If the infection is caused by Methicillin-sensitive Staphylococcus aureus (MSSA), it can be treated with standard penicillin-like antibiotics or certain cephalosporins. If the strain is identified as MRSA, a different class of antibiotics is required, as the bacteria are resistant to many common drugs.
Treatment for MRSA pharyngitis often involves antibiotics such as clindamycin, trimethoprim-sulfamethoxazole (TMP-SMX), or doxycycline, depending on the severity and local resistance patterns. Using an inappropriate antibiotic because the specific Staph strain was not identified can lead to treatment failure and worsening of the infection.
Patients are advised to complete the entire course of antibiotics, even if symptoms improve quickly, to ensure the bacteria are eradicated and minimize the risk of developing antibiotic resistance. Supportive care, including adequate hydration and over-the-counter pain relievers, is recommended to manage fever and throat discomfort. If symptoms do not improve within a few days of starting treatment, a follow-up consultation is necessary to re-evaluate the diagnosis and treatment plan.