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Following the Bugs

Researchers in Australia have used whole-genome sequencing to examine a Pseudomonas aeruginosa outbreak in a hospital neonatal unit.

As reported in Infection Control & Hospital Epidemiology this week, the team led by Raymond Chan at the Royal Prince Alfred Hospital swabbed both infants and environmental fixtures like cribs, sinks, and phones to search for evidence of the pathogen.

Eighteen babies in the ward were colonized with the bacteria, though only one became ill with pneumonia due to P. aeruginosa. Eight sinks were also colonized with P. aeruginosa, though no other environmental samples showed traces of the bug.

Sequencing of these isolates revealed that most of the isolates were identical — belonging to the P. aeruginosa strain ST253 — though one infant harbored a different strain of the bacteria. Otherwise, the samples tightly clustered, the researchers say, indicating a common source for the outbreak.

They further appeared to have split off from a common ancestor of one isolate some two years to three years prior, the researchers say, noting some variability in that estimate. The source of the outbreak was likely the sink drain from which the Pa16 isolate was taken.

"Bacteria, such as P. aeruginosa, have evolved into many strains and frequently contaminate the healthcare environment, which makes it difficult to determine the source of an outbreak and control it using traditional methods," lead author Rebecca Davis from the Royal Prince Alfred Hospital says in a statement. "Whole genome sequencing, determining the organism's entire DNA sequence in real time, changes that."