A Review of Bacterial Infections for the Physician Assistant Exam
Many bacterial infections exist, but for the Physician Assistant Exam (PANCE), there are seven biggies. Bacterial causes of diarrhea, especially food poisoning, can make someone deathly ill. Rheumatic fever isn’t commonly seen, but tests ask about it a lot.
Causes of diarrhea
For most people, diarrhea is merely inconvenient. But for people in the developing world, especially children, it’s a leading cause of death. The three big causes of diarrhea are cholera, shigella, and salmonella.
Cholera is caused by Vibrio cholerae, which is introduced when a person eats or drinks food or water contaminated by the feces of an infected person. You see cholera mainly in Africa and Third World countries. Cholera can cause a profuse secretory diarrhea, and the affected person can lose massive amounts of fluid.
The person is at risk of significant dehydration if the fluid isn’t aggressively repleted. The treatment for dehydration includes aggressive oral and/or intravenous rehydration. Cholera is treated with tetracycline derivatives or macrolide antibiotics.
Shigella is a bacterium that can cause an infectious colitis. This bacterium has several subtypes, but you need to know Shigella flexneri. It can be transmitted by eating food or drinking water that’s contaminated.
One of the main presenting symptoms of shigella is bloody diarrhea. Anyone who has contact with infected stool can acquire shigella.
Shigella diarrhea is usually a self-limited disease that runs its course in about 7 to 10 days in immunocompetent individuals. Antibiotics are used in moderate to severe cases. Penicillin and fluoroquinolones have also been used.
Salmonellosis is caused by Salmonella enterica, a bacterium that can produce an infectious diarrhea or an infectious colitis. Symptoms of nausea, vomiting, and diarrhea can develop as soon as a few hours after infection, or they can take as long as 3 days to develop. Salmonella enterica has several subtypes. People can acquire this bacterium through infected food.
Here are some key points about salmonellosis:
Symptoms of salmonellosis can be gastrointestinal upset and/or a flu-like illness. An initial presentation can be bloody diarrhea.
Antibiotic treatment is given only in moderate to advanced cases of salmonella. Many experts think that early antibiotic treatment may actually prolong the illness. Sulfa drugs and fluoroquinolones are often used.
An older adult may tell you that he or she has a history of rheumatic fever, which is a reaction to a bacterial infection caused by a beta hemolytic Group A streptococcus infection. It usually affects the heart about 3 weeks after pharyngitis or a skin infection, and it’s a leading cause of mitral stenosis.
Rheumatic fever is diagnosed by the Jones criteria, which consists of major and minor criteria:
Major criteria: The major Jones criteria are Sydenham’s chorea, carditis, polyarticular joint inflammation, subcutaneous nodules, and a characteristic skin rash, erythema marginatum. The carditis can be myocarditis or pericarditis.
Minor criteria: The minor Jones criteria can include fever, joint pain, an elevated white cell count on a CBC, laboratory evidence of inflammation (including a high sed rate), and signs of conduction block on a ECG.
If you have one minor criterion and two of the major criteria in the setting of a recent Strep infection, you have your diagnosis of rheumatic fever.
Rheumatic fever as a new diagnosis is rare these days, because many Strep infections are caught and treated early. The initial treatments consist of antibiotics, including penicillin, as well as medications to reduce inflammation. Sometimes prednisone is given.
Botulism is caused by Clostridium botulinum. The clinical scenario is eating something from a damaged can or from an improperly home-canned product, and getting sick. Within several hours, nasty symptoms can develop, including vision problems and gastrointestinal upset. The really bad symptoms include paralysis and respiratory failure. That’s approximately equal to death.
Other symptoms can include problems with talking or swallowing food — these symptoms represent the body’s muscles becoming paralyzed because of the botulinum toxin. The paralysis is so bad that the affected person needs to be put on a ventilator. The treatment is the administration of antitoxin.
Tetanus, also known as lockjaw, is caused by the bacterium Clostridium tetani, which is found in the soil. It usually gets into a body through some kind of injury, such as by stepping on a rusty nail.
The bacteria make a toxin that can produce significant muscle spasms, which begin in the jaw and spread. The muscle spasms can become more intense, so strong that they can actually cause a tear in the muscle. Muscle rigidity increases. The person can have difficulty swallowing. Sometimes a person can present with seizures.
The treatment for tetanus is antibiotics, usually penicillin or metronidazole (Flagyl). If you see a PANCE question about treating tetanus and one of the answer choices is metronidazole, pick it. Benzodiazepines can help relax the muscles. The most important treatment for tetanus is the administration of immunoglobulin.
Diphtheria is a condition you may have heard your grandparents or great-grandparents talk about when they discussed their childhoods. Before immunization, it was a common cause of death. The United States had an estimated 100,000 to 200,000 cases in the 1920s. In the period from 2000 to 2007, there were only 3 cases! Not being vaccinated is a serious risk factor for acquiring diphtheria.
Diptheria is caused by Corynebacterium diphtheriae. The initial symptoms of diphtheria can resemble a common upper respiratory tract infection or pharyngitis. Then they can turn nasty. Here are some key points to remember about diphtheria:
Diphtheria infection can cause the formation of a gray pseudomembrane on the pharynx of the affected person.
The significant adenopathy caused by diphtheria can give the sufferer a bull-neck appearance.
Diphtheria can be a cause of myocarditis.
The treatment is the use of erythromycin or penicillin that is given intramuscularly. A specific diphtheria antitoxin is used when significant symptoms, such as a pseudomembrane, develop.