Infectious Diseases in Critical Care Medicine

Table 8

Radiographic Findings (

Continued

)

Pathogen

Chest radiographic findings

Comments and other radiologic findings

Q fever (

C. burnetii

)

Pneumonia is the most common clinical presentation

(50% of patients). Appearance is nonspecific on chest Xray and chest CT. May appear as segmental, patchy, orlobar consolidation with or without pleural effusions.

CT may detect mild lymphadenopathy not seen on chest X ray

but this is not specific for Q fever.

Ricin toxin from

R. communis

(castor

beans)

A sublethal dose of intratracheal instilled ricin (2

mg/100 g

body weight) induced a similar response in lungs but didnot cause detectable damage in other organs. Lungs ofmice that recovered from a sublethal dose of ricindisplayed evidence of fibrosis and residual damage.

Intratracheal instillation of a lethal dose of ricin (20

mg/100 g body

weight) resulted in a hemorrhagic inflammatory response inmultiple organs.

SEB

Airways exposition to SEB (7.5–250 ng/trachea) caused a dose- and time-dependent neutrophil accumulation in BAL fluid, the

maximal effects of which were observed at 4 hr post-SEB exposure (250 ng/trachea). Eosinophils were virtually absent in BAL fluid,whereas mononuclear cell counts increased only at 24 hr post-SEB. Significant elevations of granulocytes in bone marrow (matureand immature forms) and peripheral blood have also been detected.

Typhus fever (

R. prowazekii

)

Interstitial pneumonia.

Mice developed interstitial pneumonia, with consolidation of the

alveoli, hemorrhages in lungs, multifocal granulomas in liver,and hemorrhages in brain, as seen in humans.

Viral encephalitis [alphaviruses (e.g.,

Venezuelan equine encephalitis,EEE,WEE)]

MR more sensitive than CT for encephalitis. For EEE,

abnormalities are seen in the basal ganglia and thalamus.T2-weighted images show increased intensity in basal gangliathat represents inflammation, ischemia, and edema ratherthan necrosis. Abnormalities regress with clinicalimprovement.

Basal ganglia rather than temporal lobe

abnormalities differentiates this from herpes encephalitis.

Viruses (noroviruses, hepatitis A

virus)

Norovirus commonly causes gastroenteritis. Hepatits A has

been associated with bacterial pneumonia.

Water safety threats (e.g.,

V. cholerae

,

C. parvum

)

Cryptosporidia usually causes diarrhea that may be severe.

It has caused respiratory distress as part of disseminateddisease in immune compromised infants, Non-01 strainsof

V. cholerae

has caused lobar pneumonia.

Protozoa (

C. cayatanensis,

G. lamblia, Entamoeba histolytica,Toxoplasma

spp.,

Microsporidia

)

E. histolytica

: pneumonia, lung abscess, pleurisy,

hepatobronchial fistulization, and more infrequentlypulmonary embolism. The preferential localization is theright hemithorax related to abscess in the right lobe of theliver. Left lobe abscesses lead to left-sidedpleuropulmonary complications with the risk of ruptureinto the pericardium.

E. histolytica

: Pleuropulmonary complications almost always

occur in patients with a liver abscess, the intrathoraciccontamination via transphrenic dissemination predominating.

(Continued )

Bioterrorism Infections in Critical Care 463