Precautionary measures controlled highly-resistant Gram-negative microorganism transmission

Willemsen I. Infect Control Hosp Epidemiol. 2011;32:333-341.

Issue: April 2011

The use of well-established transmission-based precautionary measures was associated with a relatively low transmission rate of highly-resistant Gram-negative rods in Dutch hospitals. Yet, the incidence for highly-resistant Gram-negative rods was higher in university hospitals vs. teaching and general hospitals, according to new study findings.

“Our study provides useful information about the incidence of patients with highly-resistant Gram-negative rods in Dutch hospitals, using a well-defined set of criteria,” the researchers wrote. “Other hospitals can use these data as a benchmark for their own situations.”

In the Incidence Density and Occurrence of Nosocomial Transmission study (TRIANGLe), Ina Willemsen, MD, in the department of medical microbiology and infection control at Amphia Hospital in the Netherlands, and colleagues assessed the incidence density and the occurrence of horizontal transmission of highly-resistant Gram-negative rods, as well as factors that influence these outcome measures, across five university hospitals, eight teaching hospitals and five general hospitals.

Patients had highly-resistant Gram-negative rods, as determined by sample testing, and were hospitalized between April 1 and Oct. 1, 2007.

Mean incidence density of patients with highly resistant gram-negative rods was 55 per 100,000 patient-days with a cumulative incidence of 39 per 10,000 patient admissions.

The only statistically significant (P=.03) independent determinant for higher incidence of highly-resistant Gram-negative rods was being hospitalized at a university hospital — this was due to the complexity of patient population and care provided in these hospitals, according to the researchers. Further, the overall adjusted transmission index of highly-resistant Gram-negative rods was 0.07.

“Most highly-resistant Gram-negative rods isolates were extended-spectrum b-lactamase producers, indicating the rapid increase in the production of this resistance mechanism in recent years,” they wrote. – by Ashley DeNyse

Disclosures: The researchers report no relevant financial disclosures.

Highly-resistant gram negatives are different than gram positives. Much, if not most of our insight into infection control has been with gram positives, which are in many respects, different from gram negatives in the environment that they live in and their potential for transmission. One of the most important areas that we’ve looked at lately has been the transmission of MRSA, where the reservoir is in people, whereas gram-negatives, the reservoir may be the toilets, the sinks, the floor, and more of the environment than people. So they have to be looked at differently, and the infection control measures need to be different as well. I think that this study did point out there is increasing incidence of infection and potential transmission in academic centers, but it may well be explained simply by a more complex group, with larger hospitals, use of house staff , etc. that may account for this. I think it does have useful methodology in regards to determining the incidence and transmission of gram-negatives that will be useful in the future. The most important aspect of the figures that they derived are to see what changes can be made, rather than just comparing one hospital with another, as all hospitals are very different in regard to the highly- resistant gram negatives that they have, their routes of transmission, and their specialization of medical care. This is an article that does contribute to the concepts and concerns about gram-negatives being transmitted, but it’s important that we look beyond just person-to-person transmission as we focus on any respects with MRSA outbreak and problems with staphylococci.

– Alan Tice, MD

Infectious Disease News Editorial Board member

Diclosure: Dr.Tice reports no relevant financial disclosures.

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