A new superbug on the horizon
Thursday, September 28, 2017
According to the Centers for Disease Control and Prevention (CDC), about 23,000 Americans die each year from infections resistant to antibiotics, with at least 2 million people becoming infected with drug-resistant bacteria.
The World Health Organization has posted a list of 12 bacterial superbugs that are resistant to most or all known antibiotic medicines and pose the greatest threat. Pathogens categorized by priority for research and development include:
- Critical bacteria: Acinetobacter baumannii, carbapenem-resistant; Pseudomonas aeruginosa, carbapenem-resistant; Enterobacteriaceae, carbapenem-resistant, ESBL-producing
- High priority: Enterococcus faecium, vancomycin-resistant; Staphylococcus aureus, methicillin-resistant, vancomycin-intermediate and resistant; Helicobacter pylori, clarithromycin-resistant; Campylobacter spp., fluoroquinolone-resistant; Salmonellae, fluoroquinolone-resistant; Neisseria gonorrhoeae, cephalosporin-resistant, fluoroquinolone-resistant
- Medium priority: Streptococcus pneumoniae, penicillin-nonsusceptible;Haemophilus influenzae, ampicillin-resistant; andShigella spp., fluoroquinolone-resistant
But heads up: A new emerged superbug has been discovered. A fatal outbreak of ST11 carbapenem-resistant hypervirulent Klebsiella pneumoniae occurred in a Chinese hospital.
According to researchers, K. pneumoniae strains proliferate in the gastrointestinal tract of humans and animals and may cause opportunistic infections such as pneumonia in clinical settings. After acquiring a plasmid encoding a carbapenemase gene, these strains become resistant to the carbapenem antibiotics and cause difficult-to-treat infections, earning the definition of "superbug," and often evolving to become ST11 CR-HvKP by acquiring hypervierulence plasmids.
This strain, ST11 CR-HvKP, can cause untreatable and fatal infections, even in those who are healthy with normal immunity.
In this study, Dr. Sheng Chen and colleagues conducted an investigation into a fatal outbreak of pneumonia in the Second Affiliated Hospital of Zhejiang University in China. They collected 21 carbapenem-resistant K. pneumoniae strains from five patients and characterized these strains for their antimicrobial susceptibility, multilocus sequence types and genetic relatedness using VITEK-2 compact system, multilocus sequence typing and whole genome sequencing.
One representative isolate from each patient was selected to establish the virulence potential using a human neutrophil assay and Galleria mellonella model as well as the genetic basis of their hypervirulence phenotype.
All five patients had undergone surgery for multiple traumas and subsequently received mechanical ventilation. The patients (aged 53-73 years) were admitted to the intensive care unit between late February and April of 2016. They all had severe pneumonia, carbapenem-resistant K. pneumoniae infections and poor responses to antibiotic treatment. They all died from severe lung infection, multiorgan failure or septic shock.
All five representative carbapenem-resistant K. pneumoniae strains belonged to the ST11 type, which is the most prevalent carbapenem-resistant K. pneumoniae type in China, and originated from the same clone. The strains were positive on the string test, had survival of about 80 percent after one hour incubation in human neutrophils, and killed 100 percent of wax moth larvae (G. mellonella) within 24 hours, suggesting that they were hypervirulent K. pneumoniae.
Genomic analyses showed that the emergence of these ST11 carbapenem-resistant hypervirulent K. pneumoniae strains was due to the acquisition of a roughly 170 kbp pLVPK-like virulence plasmid by classic ST11 carbapenem-resistant K. pneumoniae strains, which the researchers detected in specimens collected in other regions of China.
The ST11 carbapenem-resistant hypervirulent K. pneumoniae strains pose a substantial threat to human health because they are simultaneously hypervirulent, multidrug resistant and highly transmissible. The researchers recommend implementing control measures to prevent further dissemination of such organisms in the hospital setting and the community.
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