The neonatal intensive care unit at Prince George’s Hospital Center in Md. was temporarily shut down on August 9 after tests discovered the potentially deadly pseudomonas bacteria. Nine babies were transferred to nearby Children’s National Medical Center in D.C. (Video: WUSA9 / Photo: Mark Gail/The Washington Post)

The neonatal intensive care unit at Prince George’s Hospital Center in Md. was temporarily shut down on August 9 after tests discovered the potentially deadly pseudomonas bacteria. Nine babies were transferred to nearby Children’s National Medical Center in D.C. (Video: WUSA9 / Photo: Mark Gail/The Washington Post)

The neonatal intensive care unit at Prince George’s Hospital Center was temporarily shut down Tuesday after the discovery of potentially deadly bacteria in nasal swabs of three infant patients, hospital officials said.

Nine babies were being transferred from the hospital in Cheverly, Md., to the NICU at Children’s National Medical Center in Washington “out of an abundance of caution,” said Delores Butler, a spokeswoman for Dimensions Healthcare Systems, the nonprofit entity that runs hospitals in Prince George’s County.

Those transfers were expected to be completed by Tuesday night.

Hospital officials emphasized that the babies who tested positive for the pseudomonas bacteria have not shown any symptoms of illness from that infection, which can be mild in healthy individuals but far more serious for those with compromised or immature immune systems.

[Here’s what we know about pseudomonas bacteria]

Officials from the Prince George’s Hospital Center in Cheverly, Md., confirmed that nine patients in the neonatal intensive care unit were being transferred to other hospitals. (Reuters)

Dimensions board members were notified by phone Sunday about the presence of what hospital officials are describing as a troubling “cluster” of the bacteria among the NICU patients, according to two individuals with direct knowledge of the phone calls.

The discovery of the bacteria followed two recent deaths in the neonatal unit, said the two people, who spoke on the condition of anonymity because they were not authorized to comment to reporters. They also said the bacteria were found in water pipes near the NICU.

Hospital officials said that the cause of the two infant deaths was still being investigated and that so far there was no evidence that the deaths were related to the presence of the bacteria.

“There have been no clear deaths associated with these infections,” said Carnell Cooper, chief medical officer for the hospital center. He added that neonatal patients suffer from “a number of conditions that put them at risk to die.”

Cooper declined to provide details on the infants’ deaths, which along with the presence of the bacteria, were first reported by WJLA (Channel 7).

He said the hospital routinely swabs the nostrils of infants in the NICU to survey the amount and types of bacteria on their skin. When those tests showed pseudomonas in more than one baby, the hospital notified state health officials, who suggested moving the infants to another hospital.

Hospital officials are now working backward to determine how long the bacteria may have been present in the NICU and how they were introduced.

The hospital stopped admitting neonatal patients Thursday and also stopped using tap water in the intensive care unit at that point, said Dimensions executive vice president Sherry Perkins.

Joan Hebden, a nurse specializing in infection prevention with the University of Maryland Medical School, said the hospital has hired a water company to collect samples and analyze the water to determine the source of the bacteria.

Water enters the hospital through three intakes from a local municipal system that has its own filtration system, she said. Hebden did not say whether the NICU has additional water filtration or uses a separate system for its sensitive patients.

The strain of pseudomonas, she said, does not appear to be resistant to antibiotics. Hebden said there are no signs of any problems with water elsewhere in the hospital building. All water entering and leaving the facility will be tested several times and decontaminated, if necessary, before the NICU can be reopened, hospital officials said.

“In most cases, there is no single source of contamination,” said Kerri A. Thom, an infectious-disease physician with the University of Maryland Medical School. “However, in many cases, a water source can be implicated.”

When found in tap water, Pseudomonas aeruginosa, one of the most common strains of pseudomonas, is not harmful to most healthy people, experts said. But it is a bigger problem in hospitals, where it can be fatal in patients with weakened immune systems, said Chuck Gerba, a microbiology professor at the University of Arizona who has written about pseudomonas.

Patients can fall ill from drinking water that contains the bacteria, or from being contaminated by health-care workers who wash their hands with such water, he said. Gerba said pseudomonas is “fairly common” in household water faucets, but studies have shown that hospitals that use water filters cut down on pseudomonas infections by 95 percent.

Lawrence Muscarella, an expert in hospital safety who has written papers on pseudomonas bacteria, said general guidelines call for NICU infants to come in contact only with sterile water. The question, he said, becomes: How were these infants exposed?

There have been cases of the bacteria being transferred to patients from the artificial fingernails of health-care workers and via medical equipment that has been disinfected but then rinsed in tap water, Muscarella said.

The bacteria also have been known to colonize incubators that have been washed using non-sterile water. The infants in those incubators “are inhaling pseudomonas,” he said.

Water-quality experts say chlorine usually kills bacteria in water pipes, but hospitals typically take extra precautions for patients with weak immune systems, such as newborns.

A spokesman for the Washington Suburban Sanitary Commission said the utility did not find any problems when it tested chlorine levels in the water system in Cheverly last Wednesday, as part of its weekly tests of 90 sites in Montgomery and Prince George’s counties.

Jim Neustadt, the spokesman, said that one of the test sites is close to the hospital and that “chlorine levels in our water tested in that area were within the appropriate range needed to treat bacteria.” A pipe on the hospital property that leads from the WSSC system would be the hospital’s responsibility, Neustadt said.

The University of Maryland Medical System has worked with Dimensions for several years to improve Dimensions’ operations and financial performance, part of a plan negotiated between the state and county to have UMMS take over the Prince George’s hospital system and oversee construction of a new regional medical center in Largo.

Prince George’s Hospital Center has the only Level 3 NICU in Southern Maryland, according to the hospital’s website. NICUs designated as Level 3 can provide continuous life support for “extremely high-risk newborns and those with complex and critical illnesses,” according to the American Academy of Pediatrics website.

Justin Wm. Moyer, Katherine Shaver and Theresa Vargas contributed to this report.