Report: Rate of drug-resistant staph infection in Baltimore excessively high

Drug-resistant strain can potentially kill if untreated

By: Marie Cushing

Posted: 11/1/07

A drug-resistant form of staph infection has been found in Baltimore at an excessively high rate, according to a new report produced in part by Hopkins researchers.

Methicillin-resistant Staphylococcus aureus (MRSA) manifests itself as a severe respiratory infection. Unlike average staph infections, MRSA is resistant to treatment with antibiotics such as penicillin.

"I'm concerned that the rates of invasive MRSA are so high, particularly in Baltimore City," said Lee Harrison, principal investigator for the Maryland Active Bacterial Core Surveillance (ABCs) located at the Bloomberg School of Public Health.

Harrison was one of the Hopkins researchers who contributed data to the report published on Oct. 17 in the Journal of the American Medical Association.

Though previously found only in hospitals, MRSA has begun to spread into the community at an alarming rate.

There have been at least six students with MRSA infections at Hopkins since last spring, according to Director of the Student Health and Wellness Center Alain Joffe.

"We are fortunate that the students we are seeing today have relatively minor infections," Joffe said.

Surveillance found that the rate of MRSA infection in Baltimore was 116.7 per 100,000 in 2005. This figure is more than three times the study's average of 31.8 infected per 100,000. In the same year, the standardized mortality rate from the infection was 6.3 per 100,000.

But Harrison said that these figures do not represent the actual effect that MRSA infections are having.

"Only about seven percent of MRSA infections are invasive, so the overall burden of MRSA infections is over tenfold higher than reported," Harrison said.

Joffe said that the recovery rate for the students the Center has diagnosed with MRSA infections has been nearly 100 percent, with one student requiring hospital care to receive intravenous antibiotics.

The Maryland ABCs site conducts active, laboratory based surveillance for a variety of bacterial pathogens, including MRSA. This surveillance was supported by the Centers for Disease Control and Prevention.

Active surveillance involves frequent contact with hospitals to identify cases of MRSA infection not reported spontaneously.

"We have contacts in all hospitals [and] laboratories that perform cultures on Baltimore City residents with invasive MRSA infections," Harrison said.

Harrison could not explain why the rate in Baltimore was so high as compared to the other sites studied.

"The bottom line is that we really don't know for sure," Harrison said. "One possibility is that Baltimore City, a highly urban area, is being compared to other ABCs sites, which include more of a mix of urban, suburban and rural areas."

"It's comparing apples to oranges," said Laura Herrera, chief medical officer for the Baltimore City Health Department. She noted that chronic diseases are more prevalent in urban areas.

According to Harrison, it would be difficult to monitor the rate of MRSA infections in other areas. "Unfortunately, the number of ABCs sites is limited and it is very difficult to generate an accurate picture of MRSA disease burden in an area without doing the type of active surveillance we do in ABCs," Harrison said.

He added that the Maryland ABCs is discussing plans to modify MRSA surveillance in Baltimore by possibly monitoring all of Baltimore County and identifying the MRSA strains found in the city.

"I am hoping that, now that we have defined the public health burden of invasive MRSA infection, preventive measures will be increased," Harrison said.

"More information needs to be collected before a plan is put in place," said Herrera, who added that the Health Department is currently taking inventory of hospitals and other health care providers and requesting that they disclose MRSA infection statistics.

Anthony McCarthy, director of communications for Mayor Shelia Dixon, declined to comment.

"We all have a lot of work to do to get a handle on MRSA," said Nancy Fiedler, spokesperson for the Maryland Hospital Association (MHA).

"We need to be vigilant and we need to be aggressive," State Senator Lisa Gladden said.

She has announced plans to resubmit a bill which would require Maryland hospitals and nursing homes to identify patients who carry or are infected by MRSA.

The bill, which Gladden said follows guidelines established by the Society for Healthcare Epidemeology of America (SHEA), would also isolate patients who are infected with MRSA and require strict adherence to hand washing regulations.

An Oct. 17 article in the Baltimore Sun stated that the MHA is opposed to statewide mandates requiring the testing of all hospital patents for MRSA.

But according to Fiedler, while the MHA has "concerns about taking guidelines and putting them in legislation," it did not oppose the bill but rather supported an alternative version.

"The Hospital Association hates us and hates this bill," said Gladden, who said that the bill MHA supported was not enough.

"Whatever they are doing, is not effective. Since the only protocols shown to be effective in dealing with MRSA are the SHEA guidelines, let's start there," she said.

Harrison was also wary of legislation that would dictate clinical and hospital practice but conceded that "many hospitals that have an MRSA problem are testing patients for and isolating patients with MRSA, which is crucial to control the spread."

Herrera said that establishing guidelines in legislation was premature.

Gladden previously introduced the bill last year, when she said it received three votes.

"I know that heightened awareness starts the process of moving a very big ball forward up a very steep hill, but that doesn't mean bill gets passed," she said.

She hopes to introduce the MRSA legislation when regular session begins in January.

The report further stated that "incidence rates were consistently higher among blacks compared with whites in the various age groups."

The reason for this high rate among blacks is unknown, said Harrison.

"We are in the process of designing analyses to address this question."

The report noted that "the prevalence of underlying conditions, at least some of which vary by race, may play a role," and that "MRSA infection prevalence has been linked to socioeconomic status, and this might confound the association between race and incidence."

The report also found that while most MRSA infections were associated with health care, 58 percent occurred outside of the hospital.

"Community-associated MRSA did not emerge until the 1990's and has been increasing at an alarming rate since then," Harrison said.

"Both hospital-associated and community-associated MRSA infections have become endemic in the United States."

Scientists attribute this emergence of drug-resistant bacteria to the inappropriate use of antibiotics in both the hospital and the community.

While antibiotics such as penicillin are very effective at killing bacteria, the bacteria that survive because of mutations emerge more virulent and resistant than the original bacteria.

The concern for many is that MRSA could become resistant to even stronger antibiotics.

"Right now, MRSA strains, even though they are resistant to traditional antibiotics, are sensitive to antibiotics with minimal side effects," Joffe said.

Joffe added that while Hopkins students are not particulary susceptible to MRSA infections, students living in close quarters in the dorms "would theoretically be put at a higher risk."

He added that student athletes who participate in contact sports are most susceptible to MRSA infections because of their consistent exposure to skin-on-skin contact.

"We've been aware of staph infections for a long time," Head Athletic Trainer Brad Mountcastle said. While Hopkins athletic training has not yet seen a case of MRSA infection, Mountcastle said that he has been warned, "It's not a matter of not getting it - it's when."