Micro USMLE 8-29(19) (qmax 8/24 1-31 Flashcards
This patient presents with a dry cough and fever, and a chest x-ray shows consolidation in a single lobe, which suggests that she likely has pneumonia. The inability to grow the infectious organism in sputum culture suggests that?
Chlamydophila pneumoniae is the causative organism. Furthermore, her sputum sample does not stain with Gram stain, a characteristic feature of intracellular pathogens such as chlamydiae.
Chlamydophila pneumoniae is an obligate intracellular bacterium that causes atypical pneumonia, characterized by ?
a dry, hacking cough, sore throat, fever, and headaches. In contrast to typical pneumonias, the onset of atypical pneumonia is insidious, and patients look less acutely ill. This patient’s x-ray shows lung consolidation and some minor patches. In addition to patches, chest x-rays obtained from patients with pneumonia caused by this pathogen may also show streaks of infiltrate but may also reveal no abnormalities. Cytoplasmic inclusions (indicated by the number 3 in the image below) are only observed on Giemsa-stained sputum smears.
Chlamydia trachomatis is a sexually transmitted organism that can cause pneumonia during infancy. Mycoplasma pneumoniae can cause atypical pneumonia but does not produce cytoplasmic inclusions. Nocardia asteroides is a?
gram-positive bacterium that can cause pneumonia and alos pulmonary abscesses. Streptococcus pneumoniae is a gram-positive bacterium and is the most common cause of typical pneumonia.
Chlamydophila pneumoniae is an obligate intracellular bacterium that can cause ?
an atypical pneumonia with dry, hacking cough, sore throat, fever, and headache. The organisms are seen as cytoplasmic inclusion bodies on Giemsa staining of sputum.
The patient has a severe, potentially fatal, pneumonia with prominent systemic symptoms, including fever and muscle pain. The chest X-ray shows consolidation in the right lower lobe, indicated by the circle. In addition to his pneumonia, this patient has developed watery diarrhea and hyponatremia. Taken together, this description suggests respiratory legionellosis, also known as Legionnaires’ disease. Named for an epidemic that followed an American Legion convention at a Philadelphia hotel, the causative pathogen is?
Legionella pneumophila. Hyponatremia is commonly associated with Legionnaires’ disease and is more often present in this type of pneumonia than any other.
Patients with Legionnaires’ disease tend to be older (75%–80% of patients are over 50) and may have additional risk factors, including
Smoking Alcoholism Diabetes Chronic illness Immunosuppressive therapy Male sex (60%–70% of cases are seen in men) Diagnosis can be confirmed with?
lower respiratory secretions cultured on buffered charcoal yeast extract and a urine antigen test.
Listeria monocytogenes and Klebsiella pneumoniae are not notable causes of pneumonia. Although Staphylococcus aureus and Streptococcus pneumoniae are common causes of pneumonia, the patient’s lab results and the overall clinical picture point to ?
Legionella as the more likely culprit.
Staphylococcus aureus can cause pneumonia and is easily cultured on routine media. Patients with S. aureus pneumonia typically present with a short prodrome of fever followed by the onset of respiratory issues. The patient’s history of alcoholism raises the possibility of S. aureus infection, but his lab results and systemic symptoms, suggest ?
a different pathogen is responsible for his disease.
Although Klebsiella pneumoniae is not a common cause of ?
community-acquired pneumonia; it can be possible cause, particularly in the setting of diabetes, COPD, or alcohol abuse, as seen in this patient. K. pneumoniae infection would not explain this patient’s gastrointestinal manifestations and altered electrolytes and is, therefore, not the best answer.
Listeria monocytogenes causes listeriosis and is not a notable cause of pneumonia. Patients with listeriosis (older adults, pregnant women, newborns, and immunocompromised patients) typically present with fever and muscle aches preceded by diarrhea and/or gastrointestinal symptoms. Pregnant women typically present with?
nonspecific symptoms, such as fatigue and body aches. However, infections during pregnancy can cause stillbirths, miscarriage, premature delivery, or infection of newborns such as meningitis.
Streptococcus pneumoniae can cause pneumonia and is easily cultured on routine media. Pneumococcal disease occurs across the world, and high-risk populations include children younger than 2 years, adults over the age of 65, and people with weakened immune systems. The clinical picture alone would not rule out ?
S. pneumoniae, but this patient’s systemic symptoms point away from pneumococcal disease.
egionella pneumophila causes pneumonia in older patients; risk factors include a history of alcoholism, tobacco use, diabetes, chronic illness, or immunosuppression. Diagnosis can be confirmed with?
lower respiratory secretions cultured on buffered charcoal yeast extract and a urine antigen test. It is often acquired from contaminated water and is associated with watery diarrhea and hyponatremia.
This previously healthy elderly patient presents with a recent history of fever, chills, and a productive cough. Taken in combination with lobar findings on physical examination (dullness to percussion, bronchial breath sounds, and egophony in a focal area), as well as lobar consolidation on a chest x-ray, her symptoms suggest a likely diagnosis of pneumococcal pneumonia. This patient lives in the community and has no comorbid conditions or recent history that would predispose her to hospital-acquired or travel-associated pulmonary infections; this makes community-acquired pathogens the most likely cause of her condition. Streptococcus pneumoniae, the most common cause of?
community-acquired pneumonia in adults, is α-hemolytic, bile soluble, and optochin sensitive.
β-Hemolytic and bacitracin sensitive is the pattern seen with Streptococcus pyogenes. Catalase positive and coagulase positive is the pattern seen with Staphyloccocus aureus. Lactose fermentation is characteristic of ?
Klebsiella species. Cold agglutinins are seen with Mycoplasma pneumoniae.
Pneumococcal pneumonia is the most common cause of community-acquired pneumonia. It is a typical pneumonia, which presents with ?
fever, chills, and productive cough. A chest x-ray and findings on a physical examination will indicate lobar consolidation.
