Case #9:

Clinical Presentation:
A 67 year old, steroid-dependent, asthmatic woman was readmitted with fever, wheezing, and a productive cough several days after hospital discharge for an acute asthmatic attack. Her regular medications included prednisone 30 mg per day and theophylline. Respiratory failure with bilateral pulmonary infiltrates, persistent fever, and recurrent bacteremia with varying gram-negative isolates (Serratia marcescens, Enterobacter cloacae, and Escherichia coli) complicated her hospital course.

Clinical Diagnoses(in order of usual consideration):
Community Acquired Bacterial Pneumonia (eg Stretococcus pneumoniae)
Hospital Acquired Bacterial Pneumonia (eg Pseudomonas aeruginosa)
Legionella Pneumonia (Legionella pneumophila)
Adult Respiratory Distress Syndrome due to Asthma

Culture of a pulmonary bronchoscopy specimen demonstrates a serpentine distribution of various bacterial colonies across blood agar media (Case 9 Image 1).

Discussion:
Microbiologic Diagnosis:
Strongyloides Hyperinfection Syndrome
Wandering larvae of the nematode human parasite Stronglyoides stercoralis track bacteria across the plate in a "string of pearls" pattern. Larvae were observed in stool (Case 9 Image 2) and in direct examination of sputum Gram staining (Case 9 Image 3) and sputum cytology (Case 9 Image 4).

Direct penetration of the skin by free-living filariform larvae in the soil transmits the parasite. The larvae migrate to the lungs and are passed up the respiratory tract to the trachea where the may be swallowed and can persist for many years as auto-infecting, egg-producing adults in the small intestine. Immunocompromising conditions such as chronic prednisone therapy allow unrestrained autoinfection resulting in a hyperinfection syndrome. Strongyloidiasis occurs in tropic regions such as Latin America and is endemic in the southeastern United States.