Colonization and infection by MRSA in critically ill patients

Objective

To determine the incidence of colonization and infection by MRSA in critically ill patients.

Methods

A prospective study during 30 months of the patients admitted to the ICU for 24 hours or more. Throat swab, tracheal aspirate and urine were taken on admission and twice weekly. The colonization and infection by MRSA were registered. The infections were diagnosed according to CDC criteria. The infections were classified based on throat flora as: primary endogenous (PE) when they were caused by germs that were already colonizing the throat on the ICU admission; secondary endogenous (SE) when they were caused by germs that were not colonizing the throat on the ICU admission but were acquired during the stay in ICU; or exogenous (EX) when they were caused by germs that were not colonizing the throat. The infections were classified based on the onset moment: early onset (EO) were those developed during the first 4 days of the ICU stay; and late onset (LO) were those developed 5 days after ICU admission.

Results

Were admitted 1,582 patients, 953 males (60.24%). The mean age was 57.91 ± 18.83 years. The mean APACHE II score was 13.95 ± 8.93. Admission diagnoses were: 737 (46.59%) heart surgery, 189 cardiological (11.95%), 196 neurologic (12.29%), 185 trauma (11.69%), 120 respiratory (7.59%), 104 digestive (6.57%) and 51 intoxication (3.22%). Mortality was 14.79% (234 patients). A total of 36 patients had colonization by MRSA, two patients at ICU admission and 34 patients during the ICU stay. We documented 24 infections caused by MRSA (four EO and 20 LO; zero PE, 21 SE and three EX): 18 pneumonias (three EO and 15 LO; zero PE, 15 SE and three EX), three primary bacteremias (one EO and two LO; three SE), two surgical wound infections (two LO and SE) and one pressure sore infection (one LO and SE). Death occurred in 7/24 patients (29.17%) with infection caused by MRSA: 6/18 (33.33%) pneumonias, 1/3 (33.33%) primary bacteremias and 0/3 other infections.

Conclusion

In our series, most of the infections caused by MRSA were pneumonias, had a late onset and were secondary endogenous.