ID Flashcards
How are community and hospital acquired pneumonia defined?
- community occurs in the community or within the first 72 hours of hospitalization
- hospital occurs during hospitalization after the first 72 hours
Typical Community Acquired Pneumonia
- that which occurs outside the hospital setting or within the first 72 hours of hospitalization
- most commonly caused by S. pneumoniae, H. influenzae, and aerobic gram-negatives like Klebsiella
- presents with acute onset of fever and shaking chills, cough productive of thick purulent sputum, pleuritic chest pain, and dyspnea
- patients are typically tachycardic, tachypneic, and have late inspiratory crackles on exam
- CXR typically shows lobar consolidation
- treat with a fluoroquinolone or a second or third generation cephalosporin in the outpatient setting
- treat with a fluoroquinolone or a third generation cephalosporin with a macrolide in the inpatient setting
Atypical Community Acquired Pneumonia
- a community acquired pneumonia caused by an organism that is not visible on gram stain and is not culturable on standard blood agar
- more common in younger, healthy patients
- common agents include Mycoplasma pneumoniae, chlamydia pneumoniae, Coxiella burnetii, Legionella, and viruses such as flu, adenovirus, parainfluenza, etc.
- presents with a more insidious onset including headache, sore throat, fatigue, myalgias, dry cough, and fever without chills
- notably, they often have pulse-temperature dissociation in that their pulse is normal in the setting of a very high fever
- CXR typically shows diffuse reticulonodular infiltrates with minimal or without consolidation
- treat with macrolides or doxycycline
How do typical and atypical community acquired pneumonias differ?
- atypical are those that can’t be visualized using gram stain or cultured using standard blood agar
- typical includes S. pneumonia, H. influenza, and some aerobic, gram-negative rods while atypical includes Mycoplasma pneumoniae, Chlamydia pneumoniae, Coxiella, Legionella, and viruses
- typical will present with a more acute onset while atypical has a more insidious onset
- typical will usually have tachycardia while atypical is likely to have temperature-pulse dissociation
- typical usually presents with a productive cough while atypical presents with a dry cough
- on CXR typical demonstrates consolidation while atypical has diffuse reticulonodular infiltrates
What specific etiologic agents are associated with pneumonia in alcoholics and in immigrants?
- alcoholics: think Klebsiella
- immigrants: think TB
Which etiologic agents are most likely to be the cause of a secondary pneumonia?
Strep pneumo followed by S. aureus
Describe the role of CXR in the diagnosis of pneumonia.
- a PA and lateral CXR are required to confirm the diagnosis
- additionally it is considered sensitive, so if the CXR does not suggest pneumonia, do not treat with antibiotics
- CXR may take 6 weeks after clinical change to demonstrate resolution
How long after clinical resolution of a pneumonia may it take for the CXR to show resolution?
up to 6 weeks
False-negative CXRs looking for pneumonia are most often caused by what four things?
- neutropenia
- dehydration
- infection with PCP
- early disease (less than 24 hours)
What is unique about Legionella pneumonia?
- it is common in organ transplant recipients, patients with renal failure, patients with chronic lung disease, and smokers
- it presents with a pneumonia accompanied by GI symptoms and hyponatremia
How is the decision about whether or not to hospitalize a patient with pneumonia made?
using the pneumonia severity index, which takes into account demographics, comorbid illness, physical exam findings, lab findings, and radiographic findings
How is community acquired pneumonia treated?
outpatients require treatment for at least 5 days and until they have been afebrile for at least 48 hours
- for patients younger than 60 in the outpatient setting, we’re worried about S. pneumonia, Mycoplasma, Chlamydia, and Legionella: treat with macrolide or doxy as first-line agents and add a fluoroquinolone as an alternative therapy
- for patients over 60, who have a comorbid condition, or who have been treated with antibiotics in the last three months we’re worried about more typical agents: start with a fluoroquinolone and add on a second- or third-generation cephalosporin
for hospitalized patients, use a fluoroquinolone alone or a third-generation cephalosporin plus a macrolide
How is hospital-acquired pneumonia treated?
treatment is aimed at gram-negative rods:
- cephalosporins with pseudomonas coverage including ceftazidime or cefepime
- carbapenems
- zosyn
What are the most common complications of pneumonia?
- pleural effusions
- pleural empyema
- acute respiratory failure
How is pleural effusion in the setting of pneumonia managed?
- usually they are uncomplicated and resolve with treatment of the pneumonia
- a thoracentesis is needed only if it is more than 1 cm on lateral decubitus film
- it rarely progresses to an empyema but this requires chest tube drainage if it does
Ventilator Associated Pneumonia
- mechanical ventilation is a risk factor because it imapirs normal mucociliary clearance
- a bronchoalveolar lavage is performed to get cultures
- treat with a combination of two of the following: cephalosporin/penicillin/carbapenem, aminoglycoside/fluroquinolone, and vanc/linezolid
Lung Abscess
- defined as one or more suppurative cavitary lesions more than 2 cm in diameter
- results when infected lung tissue becomes necrotic, typically in the setting of inadequately treated pneumonia
- the most common agents are oral anaerobes Prevotella, Peptostreptococcus, Fusobacterium, and Bacteroides and other bacteria like S. aureus or S. pneumoniae
- because aspiration is the biggest risk factor, these abscess most commonly arise in the posterior segments of the RUL and the superior segments of the RLL
- has an indolent onset with cough productive of foul-smelling sputum, shortness of breath, fever, chills, and constitutional symptoms
- CXR reveals a thick-walled cavitation with air-fluid levels but a CT may be necessary to differentiate it from an empyema
- sputum stain or culture is unreliable and a bronchoscopy or transtracheal aspiration may be needed
- treat with hospitalization, postural drainage, and a long course of antibiotics until the cavity is gone
- antibiotics selection: ampicillin or vanc for gram-positive cocci, clindamycin or metronidazole for anaerobes, and a fluoroquinolone or ceftazidime for gram-negatives
Primary TB
- an infection due to inhalation of aerosolized M. tuberculosis
- this initial infection is known as primary TB and affects predominately the middle or lower lobes of the lungs
- although asymptomatic in most cases, primary TB will lead to a positive PPD
- the organism replicates in macrophages and may spread via the lymphatics to the hilar nodes, causing lymphadenopathy
- involvement of the hilar nodes forms a Ghon complex, which is the combination of hilar lymphadenopathy and a parenchymal, caseating granuloma in the subpleural space
- in most cases, the bacteria are walled off in these granulomas, fibrosed, and calcified, forming a Ranke complex with the infection becoming latent
- rifampin and isoniazid can be used as prophylaxis to prevent reactivation
Secondary TB
- a symptomatic stage of TB caused by reactivation of the bacteria, typically following application of TNFa inhibitors or the onset of some other immune compromised state
- reactivated bacteria tend to involve the upper lobes of the lungs where O2 content is highest and presents with cough, hemoptysis, night sweats, weight loss, and apical rales on exam
- the hematogenous spread of progressive primary or secondary TB is known as miliary TB
- spread to the brain forms cavitary lesions known as tuberculomas; spread to the vertebral column, most often the lower thoracic or upper lumbar, is known as Pott disease
- sputum culture is the definitive method for diagnosis but requires 4-8 weeks, PCR is more rapid, and AFB on microscopy is supportive of diagnosis
- rifampin, isoniazid, pyrazinamide and ethambutol is the preferred treatment combination
Primary TB is characterized by what type of granulomas?
caseating granulomas in the subpleural space of the lower lobe of the lung, which stain with AFB
What is the difference between a Ghon focus, Ghon complex, and Ranke complex?
they are progressive stages of a TB lesion
- a Ghon focus is a small area of granulomatous inflammation
- it is said to be a Ghon complex if it also involves the adjacent lymphatics or hilar lymph nodes
- when the Ghon complex fibroses and calcifies, it becomes known as a Ranke complex
What is primary progressive TB?
a primary TB infection that involves pulmonary and constitutional symptoms because the immune response is incomplete or inadequate, so it never enters a latent phase
Describe TB skin testing.
- a screening test to detect those who may have been exposed to TB
- it is for the diagnosis of latent TB, not active TB (if active TB is suspected, get a sputum acid-fast test and CXR)
- 15 mm induration is positive in those with no risk factors
- 10 mm induration is positive in those who live in a high-prevalence area, are immigrants from within the last 5 years, are homeless, prisoners, healthcare workers, nursing home residents, alcoholics, or diabetics, and those with a close contact with primary TB
- 5 mm induration is positive in those who are HIV-positive, steroid users, transplant recipients, in close contact with someone with active TB, or who have radiographic evidence of TB
- should repeat the test after 1-2 weeks if it is the individuals first time being tested
- follow up a positive test with a CXR to evaluate for active disease
How is TB treated?
- a positive PPD without CXR evidence of active TB should be followed by 9 months of isoniazid, even if the patient has a history of BCG vaccination
- those with active TB must be isolated and treated with isoniazid, rifampin, pyrazinamide, and ethambutol or streptomycin for two months followed by four more months of INH and rifampin
- remember that all these agents can cause hepatotoxicity but should only be discontinued if liver transaminases rise to 3-5 times the upper limit of normal
Isoniazid should always be given alongside what other agent? Why?
- it should always be started with vitamin B6, aka pyridoxine
- this helps prevent symptoms of B6 deficiency including stomatitis, glossitis, cheilosis, convulsions, hyper irritability, peripheral neuropathy, and sideroblastic anemia
Why is the diagnosis of TB challenging in patients with HIV?
- PPD skin testing may be falsely negative due to anergy
- patients have atypical CXR findings
- sputum smears are more likely to be negative
- granuloma formation may not be present in the later stages
What is an adverse reaction that can be caused by all TB medications? What is the indication to stop these meds?
- all can cause hepatotoxicity
- they should be discontinued only if liver transaminases rise to 3-5 times the upper limit of normal
Influenza
- caused by orthomyxovirus, divided into two antigenic types A and B, which is transmitted via respiratory droplets during the winter months
- annual epidemics are due to minor genetic reassortment while rare pandemics are due to major genetic recombination and are more often fatal
- presents with rapid onset fever, chills, malaise, headache, nonproductive cough, and sore throat
- treatment is supportive; antivirals, primarily neuraminidase inhibitors, are indicated only in severe disease or in those with a high risk of complications and must be given in the first 48 hours of illness
What is zanamivir and oseltamivir?
they are neuraminidase inhibitors which prevent the enzyme from cleaving budding viral progeny from their cellular envelope attachment points (neuraminic acid) just prior to release
Meningitis
- inflammation of the meningeal membranes that envelope the brain and spinal cord
- classified as acute, onset within hours to days, versus chronic, onset within weeks to months
- the cause of acute meningitis varies heavily by age but agents include GBS, E. coli, S. pneumoniae, H. influenzae, and N. meningitidis
- chronic meningitis is most often caused by mycobacteria, fungi, Lyme disease, or parasites
- aseptic meningitis is cased by a variety of nonbacterial pathogens such as enterovirus and HSV
- it may also be caused by non-infectious processes such as medications, SLE, and sarcoidosis
- presentation includes the classic triad of fever, nuchal rigidity, and change in mental status as well as n/v, malaise, photophobia, and headache
- signs include the manifestations of increased ICP, Kernig sign, and Brudzinski sign
- diagnosed based on LP, but should get a CT first if there are focal neurologic signs or evidence of increased ICP
- treat meant should be started immediately following the LP or before the LP if there will be a delay such as the need for a CT
- treat with empiric antibiotics, usually requiring some combination of cephalosporins, vancomycin, and ampicillin; add steroids if cerebral edema is present
Give the likely pathogens and the empiric treatment for acute bacterial meningitis in the following:
- less than 3 months (neonates)
- 3 months to 50 years old
- over 50 years old (elderly)
- immunocompromised
- neonates: GBS, E. coli, and Listeria treated with cefotaxime, amp, and vanc
- 3-50: N. meningitidis, S. pneumoniae, and H. influenzae treated with ceftriaxone/cefotaxime and vanc
- elderly: S. pneumoniae, N. meningitis, Listeria treated with ceftriaxone/cefotaxime, amp, and vanc
- immunocompromised: S. pneumoniae, N. meningitidis, Listeria, and aerobic gram-negative bacilli like Pseudomonas treated with ceftazidime, amp, and vanc
What are the Kernig and Brudzinski signs?
they are signs of meningitis
- Kernig is an inability to fully extend the knees when patients are supine with hips flexed
- Brudzinski is flexion of the legs and thighs brought on by passive flexion of the neck
What will an LP show for the following types of meningitis:
- bacterial
- viral
- fungal/TB
- bacterial: elevated opening pressure, cloudy appearance, increased cell count of predominately PMNs, increased protein, and reduced CSF-to-serum glucose ratio
- viral: normal or slightly elevated opening pressure, clear appearance, increased cell count of predominately lymphocytes, slightly increased protein, and normal clugose
- fungal/TB: elevated opening pressure, cloudy appearance, increased cell count of predominately lymphocytes, elevated protein, and diminished glucose
How does the treatment of aseptic meningitis differ from that of acute bacterial meningitis?
aseptic is self-limited and does not require anything more than supportive care, including analgesics and antipyretics
Encephalitis
- a diffuse inflammation fo the brain parenchyma
- most often viral in origin, including HSV-1, arboviruses such as West Nile, and enteroviruses such as polio
- may also be caused by toxoplasmosis, cerebral aspergillosis, metabolic encephalopathies, and T-cell lymphoma
- presents with a prodrome of headache, malaise, and myalgias; often complicated by meningitis and associated symptoms; typically progresses to altered mental status and behavioral abnormalities; focal neurologic deficits and seizures may be occur
- MRI brain is the imaging study of choice; increased areas of T2 signal in frontotemporal region is consistent with HSV encephalitis
- CSF PCR is the most specific and sensitive test for diagnosing many of the viral encephalitis causes
- treat with supportive care, antivirals (acyclovir for HSV and ganciclovir or foscarnet for CMV), and management of possible complications
How is cerebral edema treated?
hyperventilation, osmotic diuresis, and steroids to reduce ICP
Which agents are likely to cause a brain abscess in in those who have AIDS or are neutropenic?
- AIDS: toxoplasma gondii and fungi
- neutropenic: Candida, aspergillus, and zygomycosis
What is the differential diagnosis for altered mental status?
MOVE STUPID
- metabolic (B12, thiamine, serotonin, thyroid)
- oxygen (cardiopulmonary, anemia)
- vascular (HTN, CVA, vasculitis)
- electrolyte/endocrine
- seizure
- tumor/trauma/temperature
- uremia (renal or hepatic)
- psychiatric
- infection
- drugs, including withdrawal
