Abundance of Rare Antibiotic-Resistant Bacteria Found in US Hospital

In an unexpected finding, scientists recently discovered that a drug-resistant and relatively rare strain of Klebsiella pneumoniae was quite prevalent at one Houston hospital.

A superbug associated with healthcare-acquired infections, Klebsiella, is a type of Gram-negative bacterial pathogen that spreads through person-to-person contact in hospitals and other healthcare settings. Although Klebsiella often live in human intestines, where it does not cause illness, the bacteria is pathogenic and can lead to infection when it’s present in other parts of the body. Hospital patients who have fallen ill with other conditions can be susceptible to respiratory or blood infections from Klebsiella if they come into contact with the bacteria through their respirators or intravenous catheters. The pathogen is one of the many causes of antibiotic-resistant pneumonia, bloodstream infections, wound infections, surgical site infections, and meningitis that some patients run the risk of acquiring during hospital stays, particularly after they’ve received extended courses of treatment with antibiotics.

In a new study led by researchers from Houston Methodist Research Institute and Houston Methodist Hospital and published in the journal mBio, a surprising number of patients with K. pneumoniae infections were found to be infected with a rare and drug-resistant strain of the bacteria. The study researchers sequenced the genomes of 1,777 extended-spectrum beta-lactamase (ESBL)-producing K. pneumoniae strains cultured from patients, from samples collected from September 2011 and May 2015. Such strains of the bacteria are commonly resistant to antibiotics such as penicillin and cephalosporins. Of the strains sequenced, 635 (35.7%) were identified to be from the relatively uncommon clonal group 307 (CG307), which scientists have found carry a diverse set of resistance genes. Strains of K. pneumoniae from clonal group 258 (CG258) — which are more prevalent and cause most of the K. pneumoniae infections in the United States — accounted for just 474 (26.7%) of the samples collected in the study.

Researchers have found clonal type 307 K. pneumoniae sporadically in parts of Europe, Africa, Asia, and South America, but never in such a high concentration in the United States, and the study team admitted that they can't determine the reasons for the abundance of CG307 in the Houston hospital. “Finding the otherwise uncommon strain in our city was a very surprising discovery,” said the study’s senior author James M. Musser, MD, PhD, in a recent press release. “Because Klebsiella pneumoniae is a common and important cause of human infections, we urgently need to identify potential vaccine targets or other new treatments, and develop new and rapid diagnostic techniques.”

In their paper, the authors also note that over the course of their study, which spanned nearly 4 years, the incidence of ESBL-producing K. pneumoniae steadily increased from approximately 18 to 28 strains recovered per month.

“Fortunately, the strain 307 identified in our study remains susceptible to certain antibiotics that can be used to successfully treat infected patients,” said study author S. Wesley Long, MD, PhD. “The faster we can successfully identify which antibiotics this strain is sensitive to, the faster a treating physician can target the appropriate therapy to these ill patients. Our discoveries also give us the tools to begin to understand how the germ is spreading throughout the Houston area.”