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Report: Careless Use of Drugs Bred Baby-Threatening ‘Superbug’

Scientists blame post-war tetracycline use

Careless use of a broad-spectrum antibiotic in the 1950s created a “hyper-virulent” strain of germ that worsened risks for newborn babies, according to new research by gene scientists in Europe.

Today’s strain of Streptococcus agalactiae resulted from massive over-use of tetracycline in the post-World War II antibiotics boom, they report in Nature Communications.

Strains of the microbe that were sensitive to tetracycline were wiped out, leaving behind a dominant, resistant “superstrain” that is dangerous for newborn babies without careful preventive care, the authors say.

S. agalactiae is a common bacterium that colonizes the intestines or the urinary–genital tract. Between 15% and 30% of people carry the germ, but most of these individuals do not become ill from it. The bacterium can be dangerous to newborns, however, if they are exposed to it through infected fluids during delivery.

Called group-B strep (GBS), the infection can lead to potentially fatal pneumonia, meningitis, and blood infection.

The new study deciphered the genetic code of 229 samples of S. agalactiae dating from 1950 to the present, enabling scientists to draw up a family tree of the bug and its evolution.

The probe revealed a “hypervirulent” strain called CC17 that began to emerge in the early 1960s, coinciding with a worrying surge in GBS cases in both the U.S. and Europe that affected approximately one in three births.

“The use of tetracycline from 1948 onwards led in humans to the complete replacement of a diverse GBS population by only [a] few tetracycline-resistant clones particularly well adapted to their host,” the article states.

Ninety percent of S. galacticae found in human samples are of this resistant strain, the new study found.

Lead investigator Dr. Philippe Glaser of France’s Pasteur Institute said: “The impact [of tetracycline abuse] is being felt today, even though tetracycline is no longer in general use.”

Doctors usually prescribe oral antibiotics, such as penicillin or cephalexin, to kill the streptococcus before delivery. Today, GBS infections occur in approximately 1 in every 2,000 births in western countries.

Sources: Medical Xpress; August 4, 2014; and Nature Communications; August 4, 2014.

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