New staph strain alarms isle doctors
In the war between bugs and drugs, the bugs have gained ground.
The Health Department sent out a medical alert Friday warning about a strain of staph A bacteria that infected a 61-year-old Honolulu woman who had been hospitalized with chronic diabetes and end-stage kidney disease.
The strain is partially resistant to an antibiotic called vancomycin. It is the first such infection in Hawaii.
"It is definitely a concern, a wake-up call to physicians," said Dr. Sarah Park, acting state epidemiologist.
She urged doctors to select the type and dose of antibiotics with caution "in the critical fight against the rise in anti-microbial resistance."
News of the so-called vancomycin-intermediate staph A infection comes as doctors are already wary of another, more serious strain, methicillin-resistant Staphylococcus aureus (MRSA) -- the so-called superbug.
The patient identified with vancomycin-intermediate Staphylococcus aureus (VISA) had undergone vancomycin therapy for methicillin-resistant staph, the Health Department reported.
"It was classic," Park said. "She was on renal dialysis, a long-standing diabetic. Because of poor healing qualities, it was hard to treat her infections and she was probably more prone to multiple and chronic infections.
"She was probably getting more antibiotic treatment than most people ... leading to vancomycin exposure."
There is no sign that the infection has spread to other people, Park said.
About 80 to 100 U.S. cases have been reported in 10 years, all associated with previous exposure to vancomycin, she said.
Infectious disease specialists suspect there will be more in a short time because of frequent exposure of some patients to vancomycin.
"We are seeing the levels of vancomycin creeping up," said Dr. Matt Bankowski, vice president and director for clinical microbial infectious disease at Diagnostic Laboratory Services, where the germ for the Hawaii patient was identified.
"Usage has always been high and continues to be high, but the actual level of tolerance for Staph aureus, whether MRSA or VISA, has been going higher," said Bankowski.
One of three partners running a Summer Staph Institute at the John A. Burns School of Medicine, he said the vancomycin-intermediate case is a concern "because now it's in that middle gray zone that it could take to the next step where we'll start to see vancomycin-resistant Staph aureus."
The cell walls of the bacteria are getting thicker and thicker to tolerate vancomycin at levels normally prescribed and physicians are increasing frequency or dosage of the drug as the bacteria becomes more resistant, he said.
There are other drugs that can be used but doctors don't want to use them "because then we won't have anything to use if it gets to the point of a highly resistant strain," he said. "What it comes down to is, we want to get away from indiscriminate use of vancomycin and really make some good choices on other drugs that could be tried first."
Because of a characteristic that's developed with vancomycin-intermediate staph A germs, the U.S. Centers for Disease Control and Prevention has noticed decreased susceptibility to another drug, daptomycin, so that shouldn't be considered as an option, Park said.
Other antibiotics should be considered, although "less and less are open to us," she said.
Common bacteria causes varied symptoms
Staphylococcus aureus is a common bacterium that can cause a wide range of infections, from mild to life-threatening. The typical treatment is with an anti-bacterial agent such as penicillin, methicillin, oxacillin, amoxicillin and vancomycin.
The problem is that the few germs that survive can mutate to be resistant to the drugs.
That has happened with the so-called superbug" -- methicillin-resistant Staphylococcus aureus (MRSA).
Vancomycin often is an alternative antibiotic treatment for the superbug.
But now some staph A infections are appearing that are partially resistant to vancomycin.
These bugs, known as vancomycin-intermediate Staphylococcus aureus or VISA, have developed thicker cell walls so it's harder for the drug to penetrate.
In 10 years, 80 to 100 cases of VISA have been documented in the United States.
Bacteria that are completely resistant to vancomycin have a different mechanism.
Only nine U.S. cases have been identified, in Michigan, Pennsylvania and New York.