By Carol A. Kemper, MD, FACP
Corporate Antibiotic Stewardship
Antibiotic stewardship is not just for hospitals and medical clinics. In an August press release, McDonald’s announced that they are ahead of schedule in tightening the use of antibiotics in their broiler chicken supply. The press release states that “engaging farmers, producers and veterinarians in the responsible use of antibiotics is key to our vision of preserving antibiotic effectiveness through ethical practices.” The company announced that it had attained the goal of serving broiler chicken throughout the United States that had not received certain antibiotics (as designated by the World Health Organization) earlier than expected in 2016. And they are on track to eliminate the use of antibiotic-treated broiler chicken in Europe, Brazil, Canada, and Japan by January 2018, and plan to ban the use of colistin in broiler chicken by the end of 2019. Similar restrictions are planned for beef, pork, and laying hens.
Their goals are being reached sooner than anticipated with the assistance of the U.S. Department of Agriculture and the development of more rapid screening techniques for verifying antibiotic-free meat.
But … the cat is already out of the bag.
Hypervirulence Meets Antibiotic Resistance — A Lethal Combination
SOURCE: Gu D, Dong N, Zheng Z, et al. A fatal outbreak of ST11 carbapenem-resistant hypervirulent Klebsiella pneumoniae in a Chinese hospital: A molecular epidemiological study. Lancet Infect Dis 2017; doi.org/10/1016?S1473-3099(17)30489-9.
Chinese investigators report the appearance of a new Klebsiella “superbug,” which appears to be a convergence of hypervirulent and multidrug-resistant strains of Klebsiella pneumoniae. Five critically ill, mechanically ventilated trauma patients admitted to intensive care at a new branch of Zhejiang University Hospital (in Hangzhou, China) between February and April 2016 developed severe pneumonia. All of them failed to respond to antibiotics and died with multi-organ system failure and septic shock. Carbapenem-resistant K. pneumoniae, which were resistant to 26 different antibiotics, were recovered from blood or respiratory secretions.
Since this kind of multidrug-resistant organism had not been previously found in this brand new facility, which had opened only three months earlier, an outbreak investigation was launched. Twenty-one carbapenem-resistant K. pneumoniae strains were recovered from various clinical specimens from the five patients. All 21 strains shared similar PFGE profiles, except for one patient who had four slightly different strains. One representative strain was selected from each patient, and all five carried blaKPC2, blaTEM-1, and blaCTX-M-65 genes — meaning all were New Dehli metallo-beta-lactamase (NDM) strains. Pairwise SNP analysis suggested the different organisms derived from a single clone. The first patient with recognized infection had been transferred to the Zhejiang facility from an outside hospital following a car accident with multiple injuries, and ultimately was considered the source for the outbreak.
Bacterial colonies were found to be unusually viscous with a positive string test. Eighty percent of organism survived within neutrophils for one hour, and killed 100% of wax moth larvae within 24 hours, consistent with other hypervirulent K. pneumoniae strains. Further testing revealed they belonged to the ST11 strain type with the acquisition of a pLVPK-like virulence plasmid. In addition to containing the typical virulence genes for ST11 strains, the five outbreak strains also contained iucABCD, rmpA2, and iutA genes, which are considered additional virulence genes.
The authors retrospectively screened 387 clinical ST11 carbapenem-resistant K. pneumoniae strains from 25 provinces and municipalities in China from 2015. Eleven isolates (3%) from three different provinces carried the pLVPK-like virulence plasmid, similar to above, all of which also carried blaKPC-2 genes. Two isolates also carried rmpA2 and iucA, while the other nine carried rmpA and iroN genes, suggesting they could harbor the full cassette of genes observed in the five cases above. All of the isolates were recovered from blood and/or respiratory secretions, and five of the patients had died.
These results demonstrate the convergence of a highly virulent ST11 strain of K. pneumoniae, which has acquired a unique set of virulence genes, together with NDM-containing organism with the blaKPC-2 gene — creating a most effective, lethal, and drug-resistant superbug.
Glue Masquerading as an Aortic Root Abscess
SOURCE: Silverton N, Bull DA, Morrissey CK. Excessive surgical adhesive: A case report of aortic root abscess doppelganger. A A Case Rep 2017;9:57-59.
Aortic root abscess is considered a surgical emergency — especially when involving a prosthetic valve. This unfortunate 23-year-old was admitted with streptococcal aortic valve endocarditis requiring prosthetic valve replacement. His post-operative course was complicated by cardiac arrest, complete heart block requiring temporary pacing, and recurrent sepsis and hemodynamic instability. Repeat transesophageal echocardiogram (TEE) showed a new 1 × 2 cm tricuspid valve vegetation with severe TCV regurgitation, and a heterogenous echodensity at the base of the aortic valve concerning for root abscess. He was taken back to the operating room for intended tricuspid and aortic valve replacement and aortic root debridement and reconstruction.
Once the surgeons got into the chest, they discovered that the aortic valve was well seated and functioning normally with no evidence of abscess. Instead, they found an excess of surgical glue posterior to the aortic root that was removed easily with suction. The TCV was replaced, and the patient made an uneventful recovery, except for problems with his pacer.
Surgical glue often is used as an adjunct to strengthen the suture line in cardiovascular surgery. Surgical glue is made from a combination of bovine serum albumin and glutaraldehyde, and comes in a pre-filled syringe. Cardiologists should be aware that globs of surgical glue may appear on echocardiogram as a heterogenous fluid collection mimicking abscess. It would be interesting to know how long this image persists post-operatively and what magnetic resonance imaging would reveal.
Molecular Diagnostic Coup
SOURCE: Sada R, Uno S, Hosokawa N, Komiya T. Prosthetic valve endocarditis caused by Bartonella henselae presenting as recurrent fever and imitating granulomatosis with polyangiitis. J Formos Med Assoc 2017; doi: 10.1016/j.jfma.2017.04.001.
The use of 16S ribosomal RNA PCR testing for diagnostic purposes has greatly expanded our diagnostic ability in tough cases of culture-negative endocarditis that come to surgery for valve replacement. A colleague had a recent diagnostic coup using 16S RNA testing of pathologic tissue samples from a case of culture-negative endocarditis. All cultures and serologies, including serologies for Bartonella henselae and B. quintana, had been unrevealing, but PCR of valve tissue yielded Bartonella clarridgeiae — which allowed for appropriate antibacterial therapy in this challenging case.
These authors describe a case of a 61-year-old Japanese dairy farmer with recurrent fever of unknown origin for months, which seemed to respond transiently to various courses of antibacterial therapy. The patient had a remarkable history of prosthetic aortic valve replacement, but multiple blood cultures were negative, and echocardiography on three separate occasions was unremarkable. Because of continued fever, his workup was extended — and he was found to have polyclonal gammopathy with anti-PR3-ANCA. He then developed nephritis with active sediment, and renal biopsy demonstrated crescentic glomerulonephritis. A tentative diagnosis of granulomatosis with polyangiitis was made. Just before corticosteroids were introduced, a fourth echocardiogram suggested a small prosthetic valve vegetation, prompting aortic valve replacement. Surgical specimens were positive for B. henselae by 16S ribosomal gene PCR sequencing, using specific primers, and Bartonella henselae IgM and IgG serologies were positive.
Infective endocarditis rarely may mimic vasculitis, and C-ANCA (especially with an atypical pattern) may be found in a number of conditions stimulating a strong immune system response, including inflammatory bowel disease, cystic fibrosis, rheumatoid arthritis, and chronic infection. In this dairy farmer with house cats and dogs, an occult zoonosis makes sense.