Objectives: (1) To determine the incidence and outcome of Pseudomonas aeruginosa infection in HIV-infected patients. (2) To study the antimicrobial susceptibility of P. aeruginosa isolates in this particular population. (3) To identify risk factors for these infections.
Patients and methods: A retrospective case-control study performed in a 28-bed infectious-diseases unit in a 940-bed university hospital. All cases were defined as HIV-infected patients with severe infections due to P. aeruginosa, including bacteremia, lower or upper respiratory tract infections, infections related to a central venous catheter, and cutaneous/muscular infection. Each case was matched with an HIV-seropositive control not infected by P. aeruginosa and hospitalized on the same dates as the cases.
Results: One thousand and thirty-five HIV-infected patients were hospitalized during the study period. A first severe P. aeruginosa infection was documented in 41 patients, giving an overall annual incidence note of 2.51 episodes per 100 admissions. Forty of the 41 case notes were available for analysis. They consisted of 17 cases of bacteraemia, four upper respiratory tract infections, 10 lower respiratory tract infections, three catheter-related infections, and six cutaneous/muscular infections. Of these 40 cases, 60% were nosocomial and the remainder were community-acquired. The overall mortality rate was 22% (47% in bacteraemic forms). Twenty five percent of patients relapsed after an average of 37 days. The case-control comparison showed that AIDS was more frequent among the cases (92% vs. 74%, P = 0.04), who also had a lower PN count (P = 0.005), and a lower CD4 cell count (15.7 +/- 18.8/mm3 vs. 118 +/- 211/mm3; P = 0.0007). The number of days spent in hospital in the previous 3 months (29.3 +/- 20.7 vs. 19.7 +/- 14, P = 0.04) was significantly higher among the cases. In a multivariate analysis, examining treatments received in the previous month, only co-trimoxazole [OR = 5.5 (1.1-26.9)], penicillins [OR = 5.2 (1.1-25.3)], steroids [OR = 5.5, (1.2-25.5)] and a CD4 cell count below 50/mm3 [OR = 13.2 (1.4-129.4)] were identified as risk factors.
Conclusion: P. aeruginosa infection is a not frequent bacterial disease in highly immunodeficient HIV-infected patients. It is frequently fatal and must be borne in mind in the advanced stages of HIV disease, especially when patients have received co-trimoxazole (trianthoprim-sulphamethoxazole), penicillins or steroids.