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Biofilm formation shows association with P. aeruginosa, MRSA
Bacterial species, but not clinical variables, were associated with the formation of certain biofilms, according to study results published in BMC Infectious Diseases.
“Notably, no clinical variables were found to be independently associated with biofilm formation in our study,” the researchers wrote. “Bacterial species significantly observed to be associated with the biofilm-producing group were Pseudomonas aeruginosa and MRSA.”
Alice E. Barsoumian, MD, of the infectious disease clinic at San Antonio Military Medical Center in Fort Sam Houston, Texas, and colleagues built on results from their previous investigation in which the phenotypic and genotypic characteristics of 221 randomly selected clinical bacterial isolates were analyzed for their ability to form biofilms. In their present study, 187 isolates were obtained from 144 patients; 78% of patients were men, 61% were members of the military, and 52% had combat trauma.
After duplicate and nonclinical isolates were omitted, potential clinical predictors of infection or colonization and associated outcomes were identified through medical records. The researchers also reviewed the anatomic source of isolates and any association with devices, including catheters. They distinguished between infecting and colonizing organisms by chart review and recorded outcomes, including clinical cure, relapse/reinfection and chronic infection. Follow up was greater than 24 months.
One hundred thirteen isolates produced biofilms. Both biofilm-producing and nonbiofilm-producing bacteria were identified in 12 patients. The clinical characteristics more common in the isolate group that formed biofilms included being male (P = .01), performing military service (P < .01) and having combat trauma (P = .01). These isolates also were more likely to be associated with specific anatomical sites, respiratory and wound cultures and orthopedic device-related infections.
P . aeruginosa and MRSA were significantly associated with the biofilm-producing group, while Escherichia coli was more commonly associated with the isolates that did not. After multivariate analysis, MRSA (OR = 5.09; 95% CI, 1.12-23.1) and P. aeruginosa (OR = 3.73; 95% CI, 1.46-9.53) were the only characteristics more likely to be present in the biofilm-producing group. E. coli was less likely to be present in that group (OR = 0.07; 95% CI, 0.03-0.2).
Mortality during the initial infection was more common in patients with biofilm-producing isolates compared with nonbiofilm-producing isolates (16% vs. 5%; P = .01), although attributable mortality was low, with just one isolate-related death among 14 during the study.
“Unlike previous studies, we did not observe biofilm formation to be statistically associated with relapse/reinfection or chronic infections,” the researchers wrote. “This analysis of potential clinical risk factors and infectious outcomes of a large data set is an important addition to the understanding of this phenotype’s role in disease. Continued investigation into infectious outcomes is warranted to balance our in vitro understanding with the in vivo implications.” – by Julia Ernst, MS
Disclosure: The researchers report no relevant financial disclosures.