Antibiotic-Resistant 'Nightmare' Bacteria a Growing US Threat

Megan Brooks

April 04, 2018

Health departments working with the Centers for Disease Control and Prevention (CDC) Antibiotic Resistance Lab Network (ARLN) found more than 220 instances of germs with "unusual" antibiotic resistance genes in the United States last year, according to a Vital Signs report released Tuesday.

The report also shows that the CDC's "containment" strategy put forth in 2017 is helping to stop the spread of new and unusual types of antibiotic resistance that have yet to spread widely.

"The bottom line is that resistance genes with the capacity to turn regular germs into nightmare bacteria have been introduced into many states, but with an aggressive response we have been able to stomp them out promptly and stop their spread between people, between facilities and between other germs," CDC Principal Deputy Director Anne Schuchat, MD, reported during a media briefing.

Each year, 2 million Americans develop antibiotic-resistant infections and 23,000 die of these infections. "Today, we are talking about tackling a less common but highly important piece of the antibiotic resistance problem — using CDC's containment strategy to stop new and unusual resistance from spreading," said Schuchat.

"These unusual threats are the uncommon or highly resistant germs that have yet to spread throughout the US. We are working to get in front of these germs before they do become common. We have data showing that an aggressive approach works," she noted.

Putting Out Sparks Before They Start Fires

The CDC's containment strategy calls for rapid detection of unusual resistance in patients, assessing infection control in the facility if unusual resistance is found, screening of exposed contacts to identify asymptomatic colonization, coordinating the response with other facilities, and continuing these interventions until transmission is controlled.

The Vital Signs report summarizes the CDC's experience over the first several months of improved lab testing by the ARLN.  From January to September 2017, health departments in the ARLN tested 4442 carbapenem-resistant Enterobacteriaceae (CRE) isolates and 1334 carbapenem-resistant Pseudomonas aeruginosa  isolates; 32% and 1.9%, respectively, were carbapenemase producers.

Notably, 221 isolates with non–Klebsiella pneumoniae carbapenemases were identified. "These rare forms of resistance have the potential to add to the US CRE burden and represent an important opportunity to prevent the spread of novel resistance at its earliest stage," the authors say.

These results prompted an aggressive response, including infection control assessments and colonization screening of 1489 contacts to identify asymptomatic carriers. "The screenings showed that about 1 in 10 tests were also positive — meaning the unusual resistance had spread to other patients and could have continued spreading if left undetected. When screening tests were positive, vigilant infection control and additional screenings continued until the spread was stopped," Schuchat noted.

The Vital Signs report also details changes in the annual proportion of selected pathogens that were nonsusceptible to extended-spectrum cephalosporins (extended-spectrum β-lactamase [ESBL] phenotype) or resistant to carbapenems (CRE), using infection data from the National Healthcare Safety Network from 2006 to 2015.

The results show that the percentage of ESBL phenotype Enterobacteriaceae decreased by 2% per year, while the CRE percentage decreased by 15% per year.  This difference may be due in part to the more directed control efforts implemented to slow transmission of CRE than those applied for ESBL-producing strains, Schuchat explained.

For CRE alone, the CDC estimates that the containment strategy would prevent as many as 1600 new infections in 3 years in a single state, a 76% reduction. "The containment strategy will let us bend the curve, or slow the spread of rising resistance," Schuchat said.

Limiting the spread of emerging forms of antibiotic resistance is a public health priority, and a timely and coordinated effort among healthcare facilities, local and state health departments, and the CDC is needed to accomplish this goal, she noted.  And the improved detection and response capacities from the newly established ARLN and stronger state-based antibiotic resistance response efforts are having an impact.

"Germs do more than spread and cause infections in people. They can also share their resistance with other germs, making some untreatable. Much like a fire, finding and stopping unusual resistance early when it's just a spark protects people. The new lab capacity allows us to detect smaller resistance fires and in some cases even resistance sparks so that they can be extinguished immediately," said Schuchat.

Vital Signs. Published online April 3, 2018. Full text

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