GI Microbiota and Carbapenem-Resistant Pseudomonas aeruginosa Colonization Risk

Pseudomonas aeruginosa, petri dish
Pseudomonas aeruginosa, petri dish
Decreases in abundance of several taxa may be linked to increased risk for carbapenem-resistant P aeruginosa colonization-acquisition ICU patients.

Decreases in abundance of several bacterial taxa may be associated with increased risk for carbapenem-resistant Pseudomonas aeruginosa colonization-acquisition in intensive care unit (ICU) patients, according to a study published in Clinical Infectious Diseases.

The gastrointestinal (GI) microbiota provides colonization resistance by preventing pathogen colonization and/or inhibiting pathogen overgrowth. However, a significant subset of hospitalized patients experience a collapse of their GI microbiota that increases the risk for colonization and infection by antibiotic-resistant pathogens. In addition, antibiotics are major contributors to dysbiosis in the GI microbiota. Around 28% of ICU patients colonized with carbapenem-resistant P aeruginosa develop infection as a result of colonizing a strain of the bacteria during their ICU stay, suggesting prevention of carbapenem-resistant P aeruginosa colonization-acquisition represents an important target for interventions to reduce infection and the spread of carbapenem-resistant P aeruginosa in the hospital. Previous studies have not examined relationships among the microbiota, medications, and carbapenem-resistant P aeruginosa colonization-acquisition. Therefore, this study aimed to describe the GI microbiota of ICU patients, examine the effect of antibiotics and other medications on the GI microbiota, and identify taxonomic markers associated with carbapenem-resistant P aeruginosa colonization-acquisition in the GI tract.

At the University of Maryland Medical Center, data and 259 perirectal swabs were collected from 109 patients in the ICU. Patients were then classified into 3 groups by carbapenem-resistant P aeruginosa colonization-acquisition status and antimicrobial exposure, including patients with carbapenem-resistant P aeruginosa colonization-acquisition during their ICU stay (group 1), patients without carbapenem-resistant P aeruginosa colonization-acquisition (group 2), and patients who did not receive systemic antibiotics and did not have carbapenem-resistant P aeruginosa colonization-acquisition during their ICU stay (group 3). After 16S rRNA gene sequencing of at least 2 swabs, associations among patient characteristics, medications, carbapenem-resistant P aeruginosa colonization-acquisition, and the GI microbiota were evaluated. The 3 patient groups did not differ significantly by age, sex, race, or time between collection of swab 1 and swab 2.

Results demonstrated that the GI microbiota of patients in the ICU is characterized by high levels of pathobionts (Enterococcus, Escherichia, Staphylococcus, Enterobacteriaceae, and/or Pseudomonas) and low levels of bacterial diversity. In these patients, the effective number of species in their GI microbiota was low, ranging from 5 to 14 effective species per patient across all groups compared with the approximately 160 different taxa in healthy people. Further, 55.9% of patients were experiencing dominance by at least 1 of the 5 most frequent pathobionts at ICU admission. Piperacillin-tazobactam was prescribed more frequently to patients with carbapenem-resistant P aeruginosa colonization-acquisition compared with patients without colonization, and was associated with low abundance of potentially protective bacterial taxa and increased risk for Enterococcus domination (odds ratio [OR], 5.50; 95% CI, 2.03-14.92). Potentially protective bacterial taxa had higher abundance in patients who did not receive opioids. Between groups 1 and 2, the study examined the effect of combined use of 2 commonly prescribed and mutually exclusive antibiotic groups on carbapenem-resistant P aeruginosa colonization-acquisition: anti-anaerobic and anti-methicillin-resistant Staphylococcus aureus. Results suggested that the risk for carbapenem-resistant P aeruginosa colonization-acquisition was associated with prescription of both antibiotic groups when compared with prescription of no antibiotics (OR 3.06; 95% CI, 1.00-9.40).

Related Articles

Overall, the study authors concluded that, “Greater understanding of these relationships will facilitate 1) the development microbiota disruption indices that could be used for monitoring patients for risk of [carbapenem-resistant P aeruginosa] colonization and infection, and 2) the development of strategies to minimize infection and spread of [carbapenem-resistant P aeruginosa] in the hospital.”


Pettigrew MM, Gent JF, Kong Y, Halpin AL, Pineles L, Harris AD, Johnson JK. Gastrointestinal microbiota disruption and risk of colonization with carbapenem-resistant Pseudomonas aeruginosa in ICU patients [published online Novemeber 1, 2018]. Clin Infect Dis. doi: 10.1093/cid/ciy936/5154869