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Highly virulent, drug-resistant P. aeruginosa strain identified in Ohio
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Researchers have identified a highly virulent, multidrug-resistant form of Pseudomonas aeruginosa in patient samples in a health care system in Ohio, according to a report in Antimicrobial Agents and Chemotherapy.
The pathogen produced metallo-beta-lactamase (MBL), which has remained uncommon in the United States, but is an emerging problem in P. aeruginosa in many other countries.
“Currently, [metallo-beta-lactamase]-mediated carbapenem resistance is infrequent in the United States, although national surveillance programs have detected blaMBLs in P. aeruginosa and other bacteria,” the researchers wrote. “At the local and regional level, the early detection of MBL-producing bacteria by clinical microbiology laboratories and their molecular characterization can help inform efforts to prevent and control their dissemination.”
The initial isolate was identified in March 2012 in a patient in a long-term care facility. The patient was a 69-year-old man with type 2 diabetes and the pathogen was found in a foot wound. Six additional patients were affected across three community hospitals, one long-term care facility and one tertiary care center, and one patient died.
The P. aeruginosa pathogen produced the Verona integron-encoded MBL (VIM-2) and was resistant to all fluoroquinolones, aminoglycosides and beta-lactams. Two of the isolates were also non-susceptible to colistin, the typical “agent of last resort.”
In addition, the researchers found that the integron was part of a region that included a transposon and the Salmonella genomic island 2, which indicated a recombination event between Salmonella and P. aeruginosa, adding even more resistance genes.
“This is the first description of genetic exchange of a large mobile element — the Salmonella genome island — and resistance genes between P. aeruginosa and Salmonella,” Federico Perez, MD, of the Louis Stokes Cleveland Department of Veterans Affairs Medical Center, said in a press release. “This movement of genetic material creates concern that metallo beta-lactamases will disseminate rapidly in these enteric pathogens that are also very invasive. We are also concerned about the possibility of enhanced virulence.”
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Thomas File, MD
This report of this multi-drug resistant (MDR) Pseudomonas aeruginosa is of particular interest to our health system in Akron, Ohio, which is in close proximity to Cleveland. It is a ‘warning’ for us to be vigilant for awareness of similar organisms, which as illustrated in this report, can be transferred from one institution to another. Of particular concern of the strain described is the reduced susceptibility to colistin. As is commonly associated with MDR (in this case extremely drug-resistant) pathogens, the patients had multiple comorbidities requiring long-term care. It is reassuring that with appropriate infection control, there have been no additional cases identified due to P. aeruginosa with that particular gene element.
This illustrates the utility of newer, sophisticated molecular tests and gene sequencing to identify specific pathogens and resistance patterns. Of interest, the investigators were able to identify genetic exchange of a large mobile element (the Salmonella Genome Island), which had not been previously described. Utilization of newer molecular tests to identify pathogens and gene sequences, as utilized in this report, will be a major improvement in diagnosis and therapy in the future. I believe it will lead to a major change in the paradigm for management of infectious diseases, as it will allow pathogen/genotype specific therapy. This, in combination with comprehensive antimicrobial stewardship, should lead to improved outcomes for our patients.
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