Microbial isolates from patients in an intensive care unit, and associated risk factors

A retrospective one-year analysis of blood, sputum and urine samples taken from all patients admitted for more than 48 hours to the Intensive Care Unit at the University Hospital of the West Indies (UHWI) was undertaken. Positive trapped sputum cultures were found in 50% of patients, positive blood cultures in 32.7% and positive urine cultures in 23.1%. Gram-negative organisms predominated especially Pseudomonas aeruginosa (41.3%) and Acinetobacter spp (33.5%). Coagulase-negative staphylococcus (20%) and streptococcus group D (18.7%) were the most common gram-positive organisms. The Acinetobacter spp showed marked resistance to most antibiotics except for meropenem (82.7% susceptibility) while P. aeruginosa was most susceptible to ceftazidime (84.4%) and amikacin (89.1%). Both the coagulase-negative staphylococcus and streptococcus group D were relatively sensitive to amoxycillin/clavulanate (80.6% and 79.3% respectively). There was a high incidence of yeast found in sputum (27.1%) and urine (16.8%). Mechanical ventilation was a significant risk factor for developing a positive sputum culture (p = 0.01), this effect being particularly prominent in those ventilated for > 5 days. Central venous pressure lines significantly increased the risk of a positive blood culture (p = 0.005). This increase was seen particularly in those with CVP lines for > 7 days. Other risk factors for developing positive cultures included preadmission infection, antibiotic use just prior to ICU admission, increasing APACHE II score and increasing age.