Ventilator-associated pneumonia

Trauma and Antimicrobial Resistance Are Independent Predictors of Inadequate Empirical Antimicrobial Treatment of Ventilator-Associated Pneumonia in Critically Ill Patients

Background: We aimed to assess independent risk factors for inadequate initial antimicrobial treatment (IAT) in critically ill patients with ventilator-associated pneumonia (VAP) treated in intensive care units (ICU) and to determine whether IAT is associated with adverse outcomes in patients with VAP. Patients and Methods: A prospective cohort study was performed and included 152 patients with VAP treated in an ICU for more than 48 hours. The main outcomes of interest were all-cause ICU mortality and VAP-related mortality. Other outcomes considered were: intra-hospital mortality, VAP-related sepsis, relapse, re-infection, length of stay in ICU (ICU LOS), and number of days on mechanical ventilation (MV). Results: One-third of patients (35.5%) received inadequate antimicrobial therapy. Trauma (odds ratio [OR], 3.55; 95% confidence interval [CI], 1.25-10.06) and extensively drug-resistant (XDR) causative agent (OR, 3.09; 95% CI, 1.23-7.74) were independently associated with inadequate IAT. Inadequate IAT was associated with a higher mortality rate (OR, 3.08; 95% CI, 1.30-7.26), VAP-related sepsis (OR, 2.39; 95% CI, 1.07-5.32), relapse (OR, 3.25; 95% CI, 1.34-7.89), re-infection (OR, 6.06; 95% CI, 2.48-14.77), and ICU LOS (β 4.65; 95% CI, 0.93-8.36). Acinetobacter spp., Pseudomonas aeruginosa and Klebsiella/Enterobacter spp. were the most common bacteria in patients with IAT and those with adequate antimicrobial therapy. Conclusions: This study demonstrated that inadequate IAT is associated with a higher risk of the majority of adverse outcomes in patients with VAP treated in ICUs. Trauma and XDR strains of bacteria are independent predictors of inadequate IAT of VAP in critically ill patients.

Pseudomonas aeruginosa biofilms: mechanisms of immune evasion

The opportunistic gram-negative bacterium Pseudomonas aeruginosa is implicated in many chronic infections and is readily isolated from chronic wounds, medical devices, and the lungs of cystic fibrosis patients. P. aeruginosa is believed to persist in the host organism due to its capacity to form biofilms, which protect the aggregated, biopolymer-embedded bacteria from the detrimental actions of antibiotic treatments and host immunity. A key component in the protection against innate immunity is rhamnolipid, which is a quorum sensing (QS)-regulated virulence factor. QS is a cell-to-cell signaling mechanism used to coordinate expression of virulence and protection of aggregated biofilm cells. Rhamnolipids are known for their ability to cause hemolysis and have been shown to cause lysis of several cellular components of the human immune system, for example, macrophages and polymorphonuclear leukocytes (PMNs). In this chapter, the interplay between P. aeruginosa and the PMNs in chronic infections is discussed with focus on the role of rhamnolipids and extracellular DNA.

Management of ventilator-associated pneumonia in a multidisciplinary intensive care unit: does trauma make a difference?

OBJECTIVE

Antibiotic exposure and timing of pneumonia onset influence ventilator-associated pneumonia (VAP) isolates. The first goal of this investigation was to evaluate whether trauma also influences prevalence of microorganisms.

DESIGN

A retrospective, single-center, observational cohort study.

SETTING

Multidisciplinary teaching ICU.

PATIENTS

Adult patients requiring mechanical ventilation identified as having VAP.

INTERVENTIONS

Retrospective evaluation of a prospective manual database.

MEASUREMENTS AND MAIN RESULTS

VAP isolates in a multidisciplinary ICU documented by quantitative respiratory cultures and recorded in a 42-month database were compared, based on the presence or absence of trauma. Causative microorganisms were classified in four groups, based on mechanical ventilation duration (> 5 days), and previous antibiotic exposure. One hundred eighty-three patients developed 196 episodes of VAP (98 trauma). Methicillin-sensitive Staphylococcus aureus (MSSA) was more frequent (34.5% vs. 11.5%, p < 0.01) in trauma, whereas methicillin-resistant Staphylococcus aureus (MRSA) was more frequent (2% vs. 11.5%, p < 0.01) in non-trauma. No significant differences were found between trauma and non-trauma patients regarding prevalence of other microorganisms. In trauma patients, MSSA episodes were equally distributed between early- and late-onset VAP (51% vs. 49%), but no MRSA episode occurred in the early-onset group.

CONCLUSIONS

Trauma influences the microbiology of pneumonia and it should be considered in the initial antibiotic regimen choice. Our data demonstrate that patients with trauma had a higher prevalence of MSSA, but the overall prevalence was sufficiently high to warrant S. aureus coverage for both groups. On the other hand, since no MRSA was isolated during the first 10 days of mechanical ventilation on trauma patients, MRSA coverage in these patients becomes necessary only 10 days after admission.