Woman Infected With Rare Bacteria Causing Excruciating Pain and Requiring Hip Replacement From Dog Scratch

Being scratched by your pet dog may not seem like a big deal, but for one 66-year-old British woman, such an injury resulted in months of excruciating pain and a hip replacement, according to a case study published in BMJ Case Reports.

The woman, who had already undergone hip replacement surgery in 1997 but was otherwise healthy, first became aware of a problem when she began experiencing pain in her groin and buttocks. This pain lasted for several months before she visited her orthopedist.

The orthopedist sent the woman for some diagnostic scans, which showed she did not have cancer, easing her initial fears. Doctors suspected that the pain might be due to an infection of the woman’s replacement hip.

But the results were inconclusive, with six out of the seven cell cultures—a technique in which cells are removed from the body and grown in a fluid medium—showing nothing. The seventh, however, revealed the presence of an unidentifiable bacterium.

"All this time, the pain was becoming worse, and I was becoming increasingly frightened by what might actually be happening to me,” the patient revealed to the study authors.

After further tests confirmed the presence of the unidentified pathogen, doctors sent the samples to a specialist microbiology lab at Cardiff University to see if they could untangle the mystery.

1607551896_87c54678f5_o A dog scratch led to an infection with a rare bacteria. Eddie~S/Flickr

The woman reported that by this time, 14 months after she first saw her doctor, she was in “horrendous pain.” Diagnostic scans showed significant damage to the tissue surrounding the prosthetic hip.

A diagnostic technique known as 16S PCR helped scientists finally locate the cause of the infection. Through this test, considered to be the gold standard in bacterial identification, the team identified a microbe known as Capnocytophaga canimorsus. This bacterium that can be transmitted through the bites or licks of certain animals, including cats and dogs.

The entire medical literature includes only two reports of C. canimorsus infecting prosthetics. And neither of these cases involved an infection that developed so slowly and persisted for such a long period of time.

After being told the news, the woman recalled that she had been scratched by her pet dog roughly nine months before first visiting the orthopedist.

Doctors suggest that the animal transferred the bacteria to its claws when it licked its paws, enabling the bacteria to enter the woman’s bloodstream when she was scratched. The woman was eventually given a new hip and an appropriate course of antibiotics to clear away the pathogen. She now reports that she is living pain-free and is functioning well.

Although C. canimorsus is relatively common in dogs—scientists think about one in four harbor the pathogen in their mouths—infections caused by the bacteria are very rare because only certain strains are dangerous for humans, according to a previous study published in the journal Nature.

However, if infections do occur and they remain untreated, C. canimorsus can lead to blood-poisoning (septicemia), meningitis, inflammation of the heart’s inner lining (endocarditis) and other potentially fatal conditions.