Case Presentation: A 70-year-old male presented to the emergency department with complaints of right leg swelling, redness, and pain. The patient worked as a landscaper, and five days earlier, he had spent several hours cutting a field of tall grass that had been watered that morning with non-potable pond water. Upon completing his workday, the patient noticed multiple tiny abrasions on both lower legs, with several areas of embedded grass fragments. The following morning the patient noticed the onset of redness, followed shortly thereafter by progressive swelling and discomfort. The patient’s past medical history was remarkable for a recent acute exacerbation of COPD. At the time of presentation, his medications included prednisone 10 mg PO BID as part of a prescribed taper. Physical exam was remarkable for blood pressure of 103/80 mm Hg, heart rate of 130, and moderate edema and erythema of the right lower extremity below the knee. WBC was 23,000/L, and procalcitonin was elevated at 5.08 ng/mL. Whole blood lactate was 2.5 mmol/L. Right lower extremity venous doppler exam was negative for thrombus. The patient was fluid resuscitated, and empiric antibiotic therapy with intravenous vancomycin and ceftriaxone was initiated. Within 48 hours, Pseudomonas mendocina was isolated from all admission blood culture bottles. Antibiotic therapy was transitioned to intravenous cefepime, and a ten-day course was successfully completed, with resolution of all signs and symptoms of infection.
Discussion: Pseudomonas mendocina is an aerobic gram-negative rod that may be found both in soil and in warm, untreated water (1). It is an extremely uncommon pathogen, with less than twenty cases of human infection and only three cases of skin and soft tissue involvement reported in the world literature. Other types of P. mendocina infection have included endocarditis, osteomyelitis, peritonitis, arthritis, and bacteremia without an identified source. Environmental exposure has been described as a risk factor in two individuals (2). In this patient, small penetrations of the skin of the lower extremities caused by lawnmower-propelled grass fragments recently soaked with pond water were the presumed ports of entry. The patient’s prednisone therapy may have also been a predisposing factor to disease severity. The organism is typically sensitive to all anti-pseudomonal agents, and patients respond well to therapy, with attributed mortality of 0% (3).
Conclusions: Pseudomonas mendocina is an extremely rare cause of complicated cellulitis and sepsis in hospitalized patients. Suspicion should be aroused if the patient provides a history of occupational or environmental exposure to soil or untreated water, especially if there is any associated history or sign of skin disruption. The organism is susceptible to anti-pseudomonal antibiotics, and the prognosis for full recovery is excellent.