The woman in her 70s was in trouble. What started as a broken leg led to an infection in her hip that hung on for two years and several hospital stays. At a Nevada hospital, doctors gave the woman seven different
antibiotics, one after the other. The drugs did little to help her.
Lab results showed that none of the 14 antibiotics available at
the hospital could fight the infection, caused by the bacterium
Epidemiologist Lei Chen of the Washoe County Health
District sent a bacterial sample to the U.S.
Centers for Disease Control and Prevention.
The bacteria, CDC scientists found, produced
a nasty enzyme called New Delhi metallo-beta-lactamase, known for disabling many antibiotics. The enzyme was first seen in a patient from
India, which is where the Nevada woman broke
her leg and received treatment before returning
to the United States.
The enzyme is worrisome because it arms bacteria against
carbapenems, a group of last-resort antibiotics, says Alexander
Kallen, a CDC medical epidemiologist based in Atlanta, who
calls the drugs “our biggest guns for our sickest patients.”
The CDC’s final report revealed startling news: The bacteria
raging in the woman’s body were resistant to all 26 antibiotics
available in the United States. She died from septic shock; the
infection shut down her organs.
Kallen estimates that there have been fewer than 10 cases of
completely resistant bacterial infections in the United States.
Such absolute resistance to all available drugs, though incredibly rare, was a “nightmare scenario,” says Daniel Kadouri,
a microbiologist at Rutgers School of Dental Medicine in
Antibiotic-resistant bacteria infect more than 2 million
people in the United States every year, and at least 23,000 die,
according to 2013 data, the most recent available from the CDC.
It’s time to flip the nightmare scenario and send a killer
after the killer bacteria, say a handful of scientists with a new
approach for fighting infection. The strategy, referred to as a
“living antibiotic,” would pit one group of bacteria — given as
a drug and dubbed “the predators” — against the bacteria that
are wreaking havoc among humans.
The approach sounds extreme, but it might be necessary. Anti-
microbial resistance “is something that we really, really have to
take seriously,” says Elizabeth Tayler, senior technical officer for
antimicrobial resistance at the World Health Organization in
Geneva. “The ability of future generations to manage infection
is at risk. It’s a global problem.”
The number of resistant strains has exploded, in part
because doctors prescribe antibiotics too often. At least
30 percent of antibiotic prescriptions in the United States are
not necessary, according to the CDC. When more people are
exposed to more antibiotics, resistance is likely to build faster.
And new alternatives are scarce, Kallen says, as the pace of
developing novel antibiotics has slowed.
In search of new ideas, DARPA, a Department of Defense
agency that invests in breakthrough technologies, is support-
ing work on predatory bacteria by Kadouri, as well as Robert
Mitchell of Ulsan National Institute of Science and Technology
in South Korea, Liz Sockett of the University of Nottingham in
England and Edouard Jurkevitch of the Hebrew University of
Jerusalem. This work, the agency says, represents “a significant
departure from conventional antibiotic therapies.”
The approach is so unusual, people have called Kadouri and
his lab crazy. “Probably, we are,” he jokes.
A movie-worthy killer
The notion of predatory bacteria sounds a
bit scary, especially when Kadouri likens the
most thoroughly studied of the predators,
Bdellovibrio bacteriovorus, to the vicious
space creatures in the Alien movies.
B. bacteriovorus, called gram-negative
because of how they are stained for microscope viewing, dine on
other gram-negative bacteria. All gram-negative bacteria have
an inner membrane and outer cell wall. The predators don’t go
after the other main type of bacteria, gram-positives, which have
just one membrane.
When it encounters a gram-negative bacterium, the predator
appears to latch on with grappling hook–like appendages. Then,
like a classic cat burglar cutting a hole in glass, B. bacteriovorus
Scientists study an out-there
approach to fight infections
By Elizabeth S. Eaton
In and out Bdellovibrio, a bacterium, may offer a new way to fight
infections. It enters its bacterial host by force, squeezing in between the
cell wall and inner membrane. The predator’s enzymes break down the
prey’s innards. Next, the predator replicates, eventually bursting out of
the dead prey with its progeny. SOURCE: A.R. WILLIS ET AL/ CURREN T BIOLOGY 2016
“The ability of
to manage infection
is at risk. It’s a