Vancomycin Now Less Effective Against Bacteria

Patients who suffer from pulmonary infections or painful skin burns caused by staphylococcus aureus, a pathogenic bacteria which sometimes infects hospital patients after surgeries, may have even more to worry about now.

In the December 6, 1997, issue of The Lancet, an international medical journal published in Great Britain, Dr. Keiichi Hiramatsu of Tokyo's Juntendo Hospital reported that 20 percent of all staphylococcus aureus has become resistant to vancomycin, the only universal drug for the bacteria. It afflicts nearly one million of the 23 million Americans who undergo surgery annually, especially infants and the elderly.

The study was motivated by Hiramatsu's 1996 discovery of vancomycin-resistant staphylococcus aureus (VRSA) in a four-month-old male infant suffering from staphylococcus aureus infection after open-heart surgery. The patient failed to respond to vancomycin therapy and was cured only with a combination of other antibiotics. The strain was named Mu50 and became known as the world's first case of VRSA.

Hiramatsu also discovered that several strains of staphylococcus aureus--namely the Mu3 strain--had the potential of developing into VRSA. Hiramatsu reported that after repeated treatment with vancomycin, Mu3 developed a resistance level equal to Mu50, the VRSA strain. With each dosage of vancomycin the doctor prescribed, the more resistant the population grew, until it became just steps away from full-blown resistance.

What is Staphylococcus Aureus?

Staphylococcus aureus is a dreadful pathogen that invades the body of certain patients after surgery. It most frequently attacks people with weak immune systems, namely infants and the elderly. Intravenous drug users can also be susceptible to community-acquired staphylococcus aureus.

The bacteria leads to a wide variety of bacterial pathologies, from fatal pulmonary infections to painful skin burns. Blood infection, infection of the heart valves, infection of the lungs, meningitis (invasion of the spinal cord), osteomyelitis (infection of bone marrow), septic arthritis and perinephric abscess may also result. Many of these conditions can lead to death.

The Resistance of S. Aureus

Staphylococcus aureus, an "elite force" in the bacteria battalion, is an adaptable organism that has always developed antibiotic resistance with haste. For example, staphylococcus aureus becomes resistant to erythromycin, a protein inhibitor, after only seven to ten days. Resistance to penicillin developed a few years after its commercial production in 1941, and resistance to four or more antibiotics became the norm for 40 percent of the strains by the end of the 1950s.

Aditi Bagchi `99 says she learned all about this in Science B-55, "Evolutionary Biology." "The history of staphylococcus aureus demonstrates the need for cooperation between the medical and pharmaceutical industries, and the agricultural industries," she says. "Vancomycin is used in huge amounts in animals abroad. Therefore, it's not enough to regulate its use in the medical industry but in the agricultural one as well."

Preventative measures have been implemented by hospitals to prevent cross-contamination and infection among ward patients. Clinical usage of methicillin in the 1960s and 1970s controlled the expansion of multi-drug resistance somewhat but never assuaged the problem entirely.

Social Implications

Despite the danger of antibiotics, however, few patients have heeded the warnings. When penicillin came out, it was hailed as the savior for staphylococcus aureus patients, and afflicted individuals today would like to believe the same about vancomycin.

However, doctors say patients underestimate how quickly the bacteria can spread. A study done by the New York City Health Department showed that 470 strains of methillin-resistant staphylococcus aureus (MRSA) from around the world all descended from a single MRSA strain from Cairo, Egypt.

Even antibiotics for the common cold can have adverse effects. Over 230 million prescriptions are written each year in the United States, and physicians and patients alike have come to believe that broad-spectrum antibiotics are effective against almost any infection.

Director of University Health Services Dr. David S. Rosenthal 59 said in an interview earlier this year that Harvard students are no exception. "A lot of people come on drugs to Harvard," Rosenthal says. "They have a fever, they have antibiotics. They develop resistance to antibiotics."