Non-aeruginosa Pseudomonas spp: a critical analysis of 29 surgical and blood stream infections

Authors:
Hugo Bonatti, Saron Araya, Pooja Ajith, Sridha Gona, Aaron George

Body of Abstract:
Background: Pseudomonas aeruginosa is by far the most common non-fermentative Gram-negative rod causing human diseases. Due to new microbiology techniques recently re-classifications in this group of organisms were undertaken, and an increasing number of infections caused by other Pseudomonas strains have been reported, many in immuno-compromised individuals.

Methods: Our institutional database was searched for all surgical and blood stream infections caused by non-aeruginosa Pseudomonas spp. during a 4-year period.

Results: In total 35 isolates of non-aeruginosa Pseudomonas spp. in 29 patients were identified. Median age of the cohort was 65.3 (range 0.1-88.2) years with 58.6% being male. Rates of comorbid conditions were DM 34%, hypertension 31%, hyperlipidemia 17%, COPD 7%, CAD 7%, and malignancies 10%; 61% of individuals were obese and 24% were active smokers. Demographic, clinical, and microbiology data are shown in table 1. Isolated strains included Ps. species (14%), Ps. fluorescence (10%), Ps. putida (31%), Ps. fluorescence/putida (24%), Ps. luteola (10%), Ps. stutzeri (7%) and Ps. oleovorans (3%); 55% of infections were polymicrobial with staphylococci in 37%, streptococci in 13%, Gram-negative rods in 20%, anaerobes in 27% and yeast in 3% as co-pathogens. Blood cultures accounted for 28% of specimens, drainage fluids/tissue specimens for 31% and wound cultures for 38% of specimens, 3% came from drained abscesses. The specimens were sent in 31% by surgical services, 28% by medical services including critical care and infectious diseases, 21% by primary care physicians and 21% by the emergency department. Lower extremity soft tissue infections accounted for 62% of infections, upper extremities were involved in 3%, and 7% were intraabdominal infections. Treatment for surgical infections included incision and drainage, debridement and amputation as indicated together with antibiotics according to sensitivity testing, which showed great variability between strains.

Conclusion: Non-aeruginosa Pseudomonas spp. are a diverse group of pathogens. During the same time period 850 isolates of Ps aeruginosa in 572 patients were identified. Whereas most non-aeruginosa Pseudomonas infectious episodes were successfully treated, during a 2 year follow up 24% of patients died reflecting their severe chronic co-morbid conditions.