Drug-resistant BlaKPC may be spreading

November 2007

CHICAGO – Researchers have discovered the presence of the BlaKPC gene in bacteria in patients in a St. Louis hospital. Prior to this, the gene, which enables bacteria to become resistant to several important antibiotics, was typically found in the East Coast. Researchers say this discovery may indicate that BlaKPC is gaining strength and spreading.

Jonas Marschall, MD, a fellow in infectious disease at Washington University School of Medicine in St. Louis, presented the findings at the 47th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy, held in Chicago in September.

BlaKPC was first discovered in Klebsiella pneumoniae taken from patients in hospitals in New York City less than 10 years ago. Experts have remained concerned about the spread of bacteria with BlaKPC; the gene allows bacteria to be resistant to antibiotics in the carbapenem class, which are typically used to treat the most critically-ill patients. Studies have shown that the mortality rate may be as high as 50% for patients who test positive for bacteria with the BlaKPC gene.

Easily transferable

Marschall said the study indicated that BlaKPC may be easily transferable, thus indicating that its spread may continue. “It appears that this gene is located on a plasmid and can therefore be passed on to other bacteria relatively easily,” Marschall told Infectious Disease News . “Also, patients that are either infected or colonized with BlaKPC-positive bacteria may be unrecognized using standard clinical lab methods, which can allow for transmission of the bacteria to other patients.”

Marschall and his colleagues used polymerase chain reaction to isolate and amplify bacterial DNA to detect the BlaKPC gene. The researchers studied 243 samples from 223 patients with bloodstream-based bacterial infections. Four of the samples tested positive for BlaKPC.

Marschall said that although this number is small, the finding is significant because the gene is easily spread. It may be only a matter of time before rates increase.

Marschall said hospitals need to take steps to help prevent further spread of BlaKPC. However, there are many challenges.

Stopping the spread

“In general, contact isolation of a patient infected with BlaKPC-positive bacteria would prevent transmission to other patients,” Marschall said. “Isolation, however, implies detection. Detection of these bacteria is not optimal with conventional testing for antimicrobial susceptibility. Some laboratories do not test routinely for susceptibility to carbapenem antibiotics. Thus, as a first step to reduce resistance, methods for detection should be optimized.”

Marschall added that screening methods at many hospitals are inadequate. “There is no established screening method for BlaKPC-positive bacteria, in contrast to methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus,” he said. “The value of screening and the necessary tools are still being discussed in the scientific community.”

Marschall recommended that detection methods for BlaKPC should be improved. “Optimal detection methods should be further investigated, including the question of whether molecular screening tools need to be used,” he said.

Marschall also recommended that researchers investigate alternative antibiotic methods that can be used when antibiotics in the carbapenem class are ineffective. “Further studies should examine alternative treatment regimens that can be used if carbapenems fall away, including the development of new compounds with activity against gram-negative bacteria,” he said.

For more information:

• Marschall J, Tibbetts R, Dunne W, et al. Presence of the KPC carbapenemase gene in Enterobacteriaceae bacteremia, correlation with carbapenem susceptibility, and the impact on clinical outcomes. #196. Presented at: the 47th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy; Sept. 17-20, 2007; Chicago.