Medical Microbiology & Diagnosis

Background: In ventilated patients already critically ill, isolation of Acinetobacter baumannii from lower respiratory tract may have clinical importance and the differentiation between infection and colonization can be difficult.

Aim: We sought to overcome the confounding element of critical illness by using Simplified Acute Physiology score (SAPS II) to predict mortality risk and comparing this in critically ill ventilated patients between those with A. baumannii alone and those entirely negative lower respiratory tract cultures.

Methods: 138 eligible cases from an urban-based tertiary hospital intensive care unit (ICU) were retrospectively reviewed.

Results: Between 43 patients with A. baumannii [mean age (SD): 47 (18.5) yrs; 65% male] and 95 matched patients with negative cultures [51 (17.5); 53%], median risks of hospital mortality were not significant different but the median (IQR 25-75 ) length of total hospital stay [19 (11-32) vs. 14 (9-21) days, p=0.022] and ICU [8 (4-19) vs. 7 (3-9), p=0.010] were significantly longer in A. baumannii group. Such findings occur irrespective of whether the underlying lungs were diseased or not and whether the isolates were resistant (except for cefepime-resistance).

Conclusion:Isolation of lower respiratory tract A. baumannii alone in critically ill patients is no more likely to cause increased mortality risk than in those with negative culture, and prolonged ICU stay is likely responsible for the acquisition of A. baumannii .

Objective: A real-time polymerase chain reaction (PCR) test is expected for early and precise detection of pathogens in blood. In this study, we compared the ability of the PCR test and blood culture to detect pathogens in the blood of patients with sepsis.

Methods: Patients who were diagnosed as or suspected of having sepsis were included in this prospective observational study. A whole blood sample for PCR test was obtained serially simultaneously with the blood culture sample, and the results were compared.

Results: We obtained 93 samples from 26 patients; 69 samples were obtained during the septic condition, and 24 samples were from the non-septic condition. Origins of sepsis were pneumonia in 9 patients, necrotizing fasciitis in 5 patients, and other causes in 12 patients. In the septic condition, rates of positive results were 29.0% for the PCR test and 23.2% for blood culture. Sample contamination occurred in 1 PCR test sample and 5 blood culture samples. In positive PCR samples, 16 of 20 samples were obtained during sepsis after beginning administration of broad- spectrum antibiotics, whereas 5 of 12 samples, except for contaminated samples, were positive in blood culture.

Conclusion: In sepsis, the PCR test detected more bacteria than did blood culture even after administration of empirical antibiotics, which might contribute to precise diagnosis of the bacteremic cause of sepsis