A Rare Resistance Enzyme Takes Hold in Indiana: VIM-Producing CRE, 2016–2017

Carbapenem-resistant Enterobacteriaceae (CRE) are an emerging antibiotic-resistance threat, and much of their spread may come from strains that make carbapenemases — enzymes that destroy carbapenem antibiotics. The genes for these enzymes usually sit on mobile genetic elements that pass easily between bacterial strains, which greatly increases their potential to spread. Carbapenemase-producing CRE (CP-CRE) are also dangerous because they resist many drugs, are associated with higher death rates, and — before 2016 — most U.S. public health laboratories lacked the capacity to detect them.

A rare enzyme in the United States

Which carbapenemases turn up varies around the world. In the United States the most common is Klebsiella pneumoniae carbapenemase (KPC); the others are rarer and usually found in patients who recently had health care abroad. Verona integron-mediated metallo-β-lactamase (VIM), for example, is common in southern Europe and Southeast Asia but seldom reported in the United States.

How Indiana found it

In December 2015 the Indiana State Department of Health made CP-CRE reportable. Its laboratories trained clinical laboratory staff to detect carbapenemases, and began characterizing CP-CRE in real time so health officials could act quickly. Whenever CP-CRE is found, the department helps the health care facility put infection control in place, and the local health department investigates the patient — including health care and international travel in the previous 6 months.

What turned up

From January 2016 to December 2017, Indiana recorded 649 CP-CRE isolates, nine of them producing VIM, from seven patients. After KPC, VIM was the most common carbapenemase found.

• The VIM genes appeared in several different bacteria, among them Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae complex, Citrobacter freundii complex, Proteus mirabilis and Providencia rettgeri.
• One patient carried three different VIM-producing organisms between January 2016 and March 2017.
• Patients ranged in age from 28 to 94.
• All seven had stayed overnight in Indiana health care facilities, and none had traveled internationally in the 6 months before testing.

That pattern points to VIM spreading within Indiana’s own health care facilities.

A regional problem?

VIM is still one of the least reported carbapenemases among U.S. CRE. But Indiana and neighboring states account for 29 (71%) of the 41 VIM-producing CRE reported to CDC so far — suggesting the mechanism may be emerging regionally.

Why labs matter

The finding shows how important state public health laboratories are, both in helping clinical labs identify and report CRE and in testing for the five carbapenemases of greatest concern: KPC, NDM, VIM, IMP and OXA-48. Such testing was once scarce, but CDC’s Antibiotic Resistance Laboratory Network has expanded carbapenemase testing and CRE screening nationwide, which will reveal regional differences as new enzymes emerge. Once CP-CRE is found, epidemiologists and laboratory staff working together can get infection control in place fast — the basis of containment.

Sources

Based on Shannon DJ, Blosser S, Walters M, Kallen A, Feaster C, "Notes from the Field: Domestically Acquired Verona Integron-Mediated Metallo-β-Lactamase–Producing Enterobacteriaceae — Indiana, 2016–2017," MMWR Vol. 67, No. 25, CDC; a work of the United States government in the public domain. The report says the nine isolates were seven different species, but its table lists six, so no count is given here.