Sunday, 19 May 2019

Fast-changing genetics key to hospital superbug survival

A highly drug-resistant bacteria common in hospitals, Klebsiella pneumoniae, represents a significant antimicrobial resistance threat and should be monitored globally, say researchers. The warning follows new genetic analyses revealing how K. pneumoniae are able to quickly evolve to change their genetic makeup. This has implications for understanding how several species of bacteria -- called Enterobacteriaceae -- can rapidly adapt to essentially any antibiotic currently used in treatment.

By genetically analysing 100 strains of K. pneumoniae bacteria sampled from infected patients, carriers without symptoms and the hospital ward environment over a 14-month period, they found that the bacteria were highly transmissible and able to genetically adapt to any available antibiotic within very short periods of time.


The hospital outbreak strains of K. pneumoniae were found to be very highly drug-resistant, with all isolates analysed showing resistance to multiple drug classes, including to Carbapenems -- antibiotics used as a last resort in the treatment of severe infections.

With the number of deaths from drug-resistant infections predicted to rise from 700,000 to 10 million per year by 2050, Carbapenem-resistant Enterobacteriaceae are listed as one of three urgent threats by the Centers for Disease Control and Prevention and a key global 'critical-priority' by the World Health Organization.

READ MORE: Potential antibody treatment for multidrug-resistant K. pneumoniae

The team used whole genome DNA sequence data to reconstruct the evolution of the highly drug-resistant bacteria, including tracking their transmission within the hospital, spanning three campuses, 19 wards and two intensive care units. By using genome-wide genetic data the researchers could clearly follow their spread around the hospital. It's remarkable to see how easily these bacteria were moving between patients, particularly those in intensive care units, but we also found that they were transmitting across different hospital sites via ward equipment, including ward bed rails and medical devices.

The researchers found the bacteria were carrying many resistance plasmids, and in some cases these plasmids were present in multiple copies. We demonstrated that the number of copies helped to predict how successfully treatment was evaded by the bacteria. This means it isn't just the presence of a gene conferring resistance that is important, but also its abundance in an infecting strain.

Journal reference:

Lucy van Dorp, Qi Wang, Liam P. Shaw, Mislav Acman, Ola B. Brynildsrud, Vegard Eldholm, Ruobing Wang, Hua Gao, Yuyao Yin, Hongbin Chen, Chuling Ding, Rhys A. Farrer, Xavier Didelot, Francois Balloux, Hui Wang. Rapid phenotypic evolution in multidrug-resistant Klebsiella pneumoniae hospital outbreak strains. Microbial Genomics, 2019; DOI: 10.1099/mgen.0.000263
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology

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