New, deadly drug-resistant pathogen emerges in Ohio, exchanges genes with other bacteria

(NaturalNews) Health researchers have announced the discovery of a new antibiotic-resistant superbug in Ohio, in a study published ahead of print in the journal Antimicrobial Agents and Chemotherapy. The print version is due for publication in October.

Although any new superbug is cause for concern, researchers are particularly worried about this specific strain of Pseudomonas aeruginosa because they suspect that it may already have been spreading unnoticed for some time. In addition, the evidence suggests that the new superbug has been swapping genetic material with other potentially infectious bacteria. The genetic component responsible for their antibiotic resistance is common in bacteria worldwide, but until now has been rare in the United States.

Resistant to "last resort" drugs

Because so many different varieties of antibiotics exist, drug resistance is not always an immediate cause for concern in bacteria. More serious is multi-drug resistance, in which a species becomes resistant to multiple antibiotic varieties. In these cases, doctors are forced to either rely on much-larger-than-usual doses of mainline antibiotics or turn to rarer drugs such as the older antibiotic vancomycin, which is toxic to the kidneys.

Another common strategy for treating multidrug-resistant infections is to treat them with a combination of the antibiotic imipenem, which is highly vulnerable to being broken down within the body, and a chemical known as colistin, which denatures the enzymes that the body uses to break apart imipenem. This strategy has been particularly popular in treating P. aeruginosa, which naturally produces an enzyme to break down imipenem.

But the new strain of P. aeruginosa, researchers have found, contains a gene that codes for an enzyme called verona integron-encoded metallo beta-lactamse (VIM). VIM is common in bacteria globally but has rarely been seen in the United States.

VIM attacks a chemical structure known as a beta-lactam ring, which forms a critical structural component of a wide range of antibiotics (beta-lactam antibiotics), including not just imipenem but also penicillins, carbapenems and cephalosporins.

"VIM enzymes confer resistance to imipenem and all other beta-lactams," said lead author Federico Perez, of the Louis Stokes Cleveland Department of Veterans Affairs Medical Center in Cleveland, Ohio. "They are not inhibited by metallo beta-lactamase inhibitors."

But the new bacteria were not just resistant to beta-lactams; they also were able to resist drugs designed to disable VIM.

"Alarmingly, the [extensively drug-resistant] phenotype expressed by some of these isolates precluded any reliable antibiotic treatment since they even displayed intermediate resistance to colistin, an 'agent of last resort,'" the researchers wrote. "Patients who were affected had multiple comorbidities, endured prolonged colonization, required long-term care and, in one instance had a lethal outcome from a bloodstream infection."

Resistance spreading to other species

The new superbug was first discovered in March 2012, in a 69-year-old diabetic man with a foot wound who was living in a long-term care facility. Six other cases were eventually identified, and one patient died from the highly virulent infection. All but one of the cases were eventually traced to long-term care facilities in Northeast Ohio. The one exception was a person who appeared to have contracted the infection in another country.

Although P. aeruginosa typically only infects people with compromised immune systems, health researchers are concerned that the new strain of VIM may soon spread to other pathogens, if it hasn't already. The VIM was discovered within an integron, a type of bacterial genetic unit that can jump between different species and attach to either chromosomes or plasmids. There was also evidence that the P. aeruginosa contained a transposon, another mobile genetic element, that it had recently acquired from a Salmonella bacteria.

"This movement of genetic material creates concern that metallo beta-lactamases will disseminate rapidly in these enteric pathogens that are also very invasive," Perez said.

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