Artificial Test Soil Helped Improve Recovery Rate of Health Care Pathogens

Overdoses Related to Heroin Tripled in Three-Year Period
Overdoses Related to Heroin Tripled in Three-Year Period
Cell characteristics appear to play the biggest role in recovery.

A sponge on a stick and simulated body fluids may help the Centers for Disease Control and Prevention better understand the role surfaces play in the spread of healthcare-associated infections.

Investigators routinely collect surface samples when looking into healthcare-associated infections or evaluating cleaning and disinfection procedures, but no standard sampling protocol and the recovery efficiency of sampling tools has not been fully explored.

“Surfaces in hospitals and healthcare settings are reservoirs for multidrug-resistant organisms,” Hollis Houston, a biologist in the CDC’s Division of Healthcare Quality Promotion, said Friday during a poster session Friday at ASM 2016. “We are trying to find a way to standardize a method to sample these samples. We’ve done some work with creating a protocol, but this is more in-depth testing.”

Houston is part of a team evaluating the efficiency of the Sponge Stick (3M™), which outbreak teams use in the field, in recovering Acinetobacter baumannii, Clostridium difficile, carbapenem-resistant Klebsiella pneumoniae, and vancomycin-resistant Enterococcus faecalis from steel, laminate, and acrylic. A piece of each surface was inoculated with each organism suspended in phosphate buffer or artificial test soil that mimics bodily fluids, and allowed to dry before being sampled with a Sponge Stick.

Researchers then removed the bacteria from the Sponge Stick, cultured them, and calculated percent recovery (%R).

The artificial test soil was associated with significantly superior R% compared with the phosphate buffer (see table for data from pooled materials).

Phosphate buffer (%)

Artificial test soil (%)


Acinetobacter baumannii




C. difficile




Klebsiella pneumoniae




Enterococcus faecalis




Houston said %R varied with organism, surface, matrix and deposition method, leading researchers to believe that something in the nature of the cells of a given pathogen may be the biggest determinant in %R.

“Recovery is really surface-independent,” she said. “We’re interested in seeing what is it about each of these bacteria that makes them harder to recover or easier to recover in future studies.”


1. Houston H, Rose LJ , West-Deadwyler R, J. A. Noble-Wang. Recovery of Four Healthcare Associated Organisms from Hospital Surfaces Using Sponge Sticks. Poster presented at: ASM Microbe 2016. June 16-20, 2016; Boston, MA