Gram-negative Bacteria Increase ICU Admission, Deaths in Sarcoidosis, ILDs

The presence of certain types of bacteria, specifically gram-negative bacteria other than Pseudomonas aeruginosa, increases the risk of death, admission to an intensive care unit (ICU), and the need for vasopressors in patients with sarcoidosis or other interstitial lung diseases (ILD) who are hospitalized, a study found.

The findings were presented Oct. 10 at the 2018 Chest Annual Meeting, in San Antonio, Texas. The presentation was titled “Role of Respiratory Pathogens in Disease Outcomes in Hospitalized Patients with Interstitial Lung Disease.”

Prior studies have suggested that the burden and the type of bacteria involved in lung infections are risk factors increasing the chances of worse clinical outcomes in patients with ILD.

Now, researchers at Beaumont Health Systems, the largest healthcare system in Michigan, studied the influence of the type of bacteria and their virulence on the clinical outcomes of hospitalized patients with ILD, including patients with sarcoidosis.

The team reviewed clinical data from 472 ILD patients admitted to a large tertiary care academic center in Michigan from 2010 to 2016. The majority of these patients had either idiopathic pulmonary fibrosis (40.6%) or sarcoidosis (27.6%).

A total of 170 samples of airway fluid and lung biopsies were screened for four groups of bacteria: Pseudomonas aeruginosa, which usually causes serious infections in hospitalized patients or those with weakened immune systems; methicillin-resistant staphylococcus aureus (MRSA), a type of bacteria resistant to several common antibiotics, which often can cause serious infections in hospitalized patients with chronic conditions; gram-negative bacteria other than P. aeruginosa; and gram-positive bacteria other than MRSA.

The terms gram-negative and gram-positive denote two classes of bacteria distinguished on the basis of the exclusion or retention of a dye called gram stain. The staining reflects differences in the composition and thickness of the cell wall between the two bacteria groups. P. aeruginosa is a gram-negative species, while MRSA belongs to the gram-positive group.

Most pathogens identified in the samples were gram-negative bacteria (38.8% Pseudomonas aeruginosa and 17.6% other bacteria), and MRSA (26.5%).

Patients infected with gram-negative organisms (other than Pseudomonas) and MRSA had the highest 30-day mortality rates — 39.3% in patients infected with gram-negative bacteria; 31.8% in those with MRSA infection. 

Patients infected with Pseudomonas and other gram-positive bacteria had a lower 30-day mortality — 7.4% and 13.8%, respectively.

After data adjustment for other variables, including type of ILD, age, gender, comorbid conditions and smoking history, patients infected with gram-negative organisms (other than Pseudomonas) were also found to be at higher risk of vasopressor administration (60.7%), and of being admitted to an ICU (53.6%).

No significant link was found between the use of immunosuppressants or anti-fibrotics and clinical outcomes, including the development of resistant bacteria.

“The presence of gram-negative bacteria is a risk factor for adverse events. This bacteria could lead to a higher mortality rate, ICU admission and increased vasopressor use,” Hira Iftikhar, MD, an internal medicine specialist at Beaumont Health Systems and lead author of the study, said in a press release. 

According to Iftikhar, “a larger study should be conducted to establish the risk factors for the mortality in hospitalized ILD patients.”