Different bacteria may interact to increase likelihood of disease

by Molly Walker, Staff Writer, MedPage Today June 05, 2017

Action Points
• Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
• Nursing home patients with indwelling urinary catheters had an increased risk of multi-drug resistant bacteria present in their urine if they were colonized with more than one multi-drug resistant organism.
• Note that the presence of one multi-drug resistant organism increased the risk of colonization with other drug-resistant bacteria.

NEW ORLEANS — Nursing home patients with indwelling urinary catheters had an increased risk of multi-drug resistant bacteria present in their urine if they were colonized with more than one multi-drug resistant organism, researchers found here.
Co-colonization with a pair of multi-drug resistant organisms was linked to a higher risk of developing a catheter-associated urinary tract infection, reported Joyce Wang, PhD, of the University of Michigan, and colleagues.
Notably, co-colonization with Escherichia coli and Proteus mirabilis was linked to a more than threefold increased risk of developing an E. coli catheter-associated UTI (HR 3.1).
Co-colonization with MRSA and P. mirabilis and co-colonization with E. coli and VRE were both associated with a more than fourfold increased risk of a Staphyloccus aureus catheter-associated UTI (HR 4.8) and an Enterococcus catheter-associated UTI, respectively (HR 4.0).
The authors called these risks statistically significant at P<0.1, though P<0.05 is generally considered the threshold for significance.
At a poster presentation at the ASM Microbe meeting, Wang told MedPage Today that, generally, acute care hospitals are the focus of most of the discussion around antibiotic resistance, but the risk exists in nursing homes as well.
Wang and colleagues looked at data from a study that examined patients in 12 nursing homes in southeast Michigan. But they took it a step further — by looking at the biology of the drug-resistant bacteria there. She said the goal was to determine “is this bacteria here because the patients are so sick, they are vulnerable to anything, or do these bacteria actually interact with each other.”
They examined data from 234 nursing home residents equipped with an indwelling urinary catheter for more than 72 hours. Patients were swabbed at the groin and rectal area on the first day of enrollment, day 14 and monthly thereafter, to detect the colonization of antibiotic resistant organisms.
Overall, there were 182 catheter-associated urinary tract infections, and multi-drug resistant organisms were frequently found in the groin and peri-rectal areas.
They identified antibiotics in the samples, such as penicillins, carbapenems, aminoglycosides, glycopeptides and nitrofurans, and multi-drug resistant organisms such as E. coli, P. mirabilis, vancomycin-resistant enterococci(VRE), methicillin-resistant S. aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii.
Not surprisingly, antibiotic use was associated with a significant increased risk of colonization with these drug-resistant bacteria:
• Nitrofurans linked to increased risk of P. mirabilis (HR 9.3)
• Carbapenems and aminoglycosides linked to increased risk of P. aeruginosa (HR 7.3 and HR 5.7)
• Aminoglycosides linked to increased risk of A. baumannii (HR 6.4)
• Glycopeptides linked to increased risk of VRE (HR 5.9)
• Penicillin linked with a more than fourfold risk of the presence of E. coli (HR 4.5, P<0.05 for all)
But the presence of one multi-drug resistant organism increased the risk of colonization with other drug-resistant bacteria. A patient colonized with A. baumannii had more than an eleven-fold risk of being colonized with P. mirabilis. This risk went in both directions, with patients colonized with P. mirabilis a five-fold increased risk of being colonized with A. baumannii.
Asked for his opinion, Stephen Jenkins, MD, a clinical microbiologist at Weill-Cornell Medicine and New York-Presbyterian, who was not involved with the research, told MedPage Today that nursing homes are known to be sources of multi-drug resistant organisms.
“I think it’s because of the recurrent antibiotic exposure these people have,” he said. “Bugs learn fast.”
Jenkins added that more judicious antibiotic use and surveillance cultures might make sense in this population.
“At least that way, the nursing homes will know they need to start empirically with a drug that’s going to cover a multi-drug resistant organism,” Jenkins said. “As it stands now, without that, they’ll have to wait for cultures to come back, and the potential morbidity and mortality in this population could be a disaster.”
Wang said the next steps involve collecting data on a national scale. She said her group is potentially collaborating with the CDC to look at how these pathogens move from hospital to nursing home to community.
Wang emphasized the importance of having “the optimal combination of antibiotics” for patient care, but added that “we’re not going to tell doctors how to prescribe to patients.”
• Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner