Heather L. Cox

Molecular Dissection of an Outbreak of Carbapenem-Resistant Enterobacteriaceae Reveals Intergenus KPC Carbapenemase Transmission through a Promiscuous Plasmid

ABSTRACT Carbapenem-resistant Enterobacteriaceae (CRE) have emerged as major causes of health care-associated infections worldwide. This diverse collection of organisms with various resistance mechanisms is associated with increased lengths of hospitalization, costs of care, morbidity, and mortality. The global spread of CRE has largely been attributed to dissemination of a dominant strain of Klebsiella pneumoniae producing a serine β-lactamase, termed K. pneumoniae carbapenemase (KPC). Here we report an outbreak of KPC-producing CRE infections in which the degree of horizontal transmission between strains and species of a promiscuous plasmid is unprecedented. Sixteen isolates, comprising 11 unique strains, 6 species, and 4 genera of bacteria, were obtained from 14 patients over the first 8 months of the outbreak. Of the 11 unique strains, 9 harbored the same highly promiscuous plasmid carrying the KPC gene blaKPC. The remaining strains harbored distinct blaKPC plasmids, one of which was carried in a strain of Klebsiella oxytoca coisolated from the index patient and the other generated from transposition of the blaKPC element Tn4401. All isolates could be genetically traced to the index patient. Molecular epidemiological investigation of the outbreak was aided by the adaptation of nested arbitrary PCR (ARB-PCR) for rapid plasmid identification. This detailed molecular genetic analysis, combined with traditional epidemiological investigation, provides insights into the highly fluid dynamics of drug resistance transmission during the outbreak. IMPORTANCE The ease of horizontal transmission of carbapenemase resistance plasmids across strains, species, and genera of bacteria observed in this study has several important public health and epidemiological implications. First, it has the potential to promote dissemination of carbapenem resistance to new populations of Enterobacteriaceae, including organisms of low virulence, leading to the establishment of reservoirs of carbapenem resistance genes in patients and/or the environment and of high virulence, raising the specter of untreatable community-associated infections. Second, recognition of plasmid-mediated outbreaks, such as those described here, is problematic because analysis of resistance plasmids from clinical isolates is laborious and technically challenging. Adaptation of nested arbitrary PCR (ARB-PCR) to investigate the plasmid outbreak facilitated our investigation, and the method may be broadly applicable to other outbreaks due to other conserved mobile genetic elements. Whether infection control measures that focus on preventing transmission of drug-resistant clones are effective in controlling dissemination of these elements is unknown. The ease of horizontal transmission of carbapenemase resistance plasmids across strains, species, and genera of bacteria observed in this study has several important public health and epidemiological implications. First, it has the potential to promote dissemination of carbapenem resistance to new populations of Enterobacteriaceae, including organisms of low virulence, leading to the establishment of reservoirs of carbapenem resistance genes in patients and/or the environment and of high virulence, raising the specter of untreatable community-associated infections. Second, recognition of plasmid-mediated outbreaks, such as those described here, is problematic because analysis of resistance plasmids from clinical isolates is laborious and technically challenging. Adaptation of nested arbitrary PCR (ARB-PCR) to investigate the plasmid outbreak facilitated our investigation, and the method may be broadly applicable to other outbreaks due to other conserved mobile genetic elements. Whether infection control measures that focus on preventing transmission of drug-resistant clones are effective in controlling dissemination of these elements is unknown.

First Clinical Cases of OXA-48-Producing Carbapenem-Resistant Klebsiella pneumoniae in the United States: the “Menace” Arrives in the New World

ABSTRACT OXA-48 has emerged as a major carbapenemase associated with the Enterobacteriaceae in Europe, North Africa, and Asia. We report the first two clinical cases of OXA-48-type carbapenemase-producing Enterobacteriaceae in the United States from patients recently hospitalized in Saudi Arabia and India. Each is more carbapenem resistant than nearly all previously reported OXA-48-type-producing Enterobacteriaceae.

Fatal cross infection by carbapenem-resistant Klebsiella in two liver transplant recipients

Abstract: Members of the family Enterobacteriaceae including Klebsiella have re‐emerged as major pathogens in solid organ transplantation. The recent appearance and dissemination of carbapenemase‐producing Enterobacteriaceae in Europe and the northeastern United States represents a major challenge to the treatment of enteric gram‐negative bacterial infections in immunocompromised patients; however, few reports have detailed the outcomes of such infections. Here we report 2 cases of Klebsiella pneumoniae carbapenemase (KPC)‐producing Klebsiella infections in orthotopic liver transplant recipients, which were the index case and initial secondary case for an outbreak of KPC‐producing Enterobacteriaceae in our institution. In both instances, the pathogens were initially misidentified as being carbapenem sensitive, the infections recurred after cessation of directed therapy, and the patients ultimately succumbed to their infections.

Nested Russian doll-like genetic mobility drives rapid dissemination of the carbapenem resistance gene blakpc

ABSTRACT The recent widespread emergence of carbapenem resistance in Enterobacteriaceae is a major public health concern, as carbapenems are a therapy of last resort against this family of common bacterial pathogens. Resistance genes can mobilize via various mechanisms, including conjugation and transposition; however, the importance of this mobility in short-term evolution, such as within nosocomial outbreaks, is unknown. Using a combination of short- and long-read whole-genome sequencing of 281 blaKPC-positive Enterobacteriaceae isolates from a single hospital over 5 years, we demonstrate rapid dissemination of this carbapenem resistance gene to multiple species, strains, and plasmids. Mobility of blaKPC occurs at multiple nested genetic levels, with transmission of blaKPC strains between individuals, frequent transfer of blaKPC plasmids between strains/species, and frequent transposition of blaKPC transposon Tn4401 between plasmids. We also identify a common insertion site for Tn4401 within various Tn2-like elements, suggesting that homologous recombination between Tn2-like elements has enhanced the spread of Tn4401 between different plasmid vectors. Furthermore, while short-read sequencing has known limitations for plasmid assembly, various studies have attempted to overcome this by the use of reference-based methods. We also demonstrate that, as a consequence of the genetic mobility observed in this study, plasmid structures can be extremely dynamic, and therefore these reference-based methods, as well as traditional partial typing methods, can produce very misleading conclusions. Overall, our findings demonstrate that nonclonal resistance gene dissemination can be extremely rapid, presenting significant challenges for public health surveillance and achieving effective control of antibiotic resistance.

Control of Simultaneous Outbreaks of Carbapenemase-Producing Enterobacteriaceae and Extensively Drug-Resistant Acinetobacter baumannii Infection in an Intensive Care Unit Using Interventions Promoted in the Centers for Disease Control and Prevention 2012 Carbapenemase-Resistant Enterobacteriaceae Toolkit

OBJECTIVE We describe the efficacy of enhanced infection control measures, including those recommended in the Centers for Disease Control and Preventions 2012 carbapenem-resistant Enterobacteriaceae (CRE) toolkit, to control concurrent outbreaks of carbapenemase-producing Enterobacteriaceae (CPE) and extensively drug-resistant Acinetobacter baumannii (XDR-AB). DESIGN Before-after intervention study. SETTING Fifteen-bed surgical trauma intensive care unit (ICU). METHODS We investigated the impact of enhanced infection control measures in response to clusters of CPE and XDR-AB infections in an ICU from April 2009 to March 2010. Polymerase chain reaction was used to detect the presence of blaKPC and resistance plasmids in CRE. Pulsed-field gel electrophoresis was performed to assess XDR-AB clonality. Enhanced infection-control measures were implemented in response to ongoing transmission of CPE and a new outbreak of XDR-AB. Efficacy was evaluated by comparing the incidence rate (IR) of CPE and XDR-AB before and after the implementation of these measures. RESULTS The IR of CPE for the 12 months before the implementation of enhanced measures was 7.77 cases per 1,000 patient-days, whereas the IR of XDR-AB for the 3 months before implementation was 6.79 cases per 1,000 patient-days. All examined CPE shared endemic blaKPC resistance plasmids, and 6 of the 7 XDR-AB isolates were clonal. Following institution of enhanced infection control measures, the CPE IR decreased to 1.22 cases per 1,000 patient-days (P = .001), and no more cases of XDR-AB were identified. CONCLUSIONS Use of infection control measures described in the Centers for Disease Control and Preventions 2012 CRE toolkit was associated with a reduction in the IR of CPE and an interruption in XDR-AB transmission.

A Healthcare Improvement Intervention Combining Nucleic Acid Microarray Testing With Direct Physician Response for Management of Staphylococcus aureus Bacteremia

Background Nucleic acid microarray (NAM) testing for detection of Staphylococcus aureus bacteremia (SAB) and S. aureus resistance gene determinants can reduce time to targeted antibiotic administration. Evidence-based management of SAB includes bedside infectious diseases (ID) consultation. As a healthcare improvement initiative at our institution, with the goal of improving management and outcomes for subjects with SAB, we implemented NAM with a process for responding to positive NAM results by directly triggered, mandatory ID consultation. Methods Preintervention, SAB was identified by traditional culture and results passively directed to antibiotic stewardship program (ASP) pharmacists. Postintervention, SAB in adult inpatients was identified by Verigene Gram-Positive Blood Culture test, results paged directly to ID fellow physicians, and consultation initiated immediately. In the new process, ASP assisted with management after the initial consultation. A single-center, retrospective, pre-/postintervention analysis was performed. Results One hundred six preintervention and 120 postintervention subjects were assessed. Time to ID consultation after notification of a positive blood culture decreased 26.0 hours (95% confidence interval [CI], 45.1 to 7.1 hours, P < .001) postintervention compared with preintervention. Time to initiation of targeted antibiotic decreased by a mean of 21.2 hours (95% CI, 31.4 to 11.0 hours, P < .001) and time to targeted antibiotics for methicillin-sensitive S. aureus decreased by a mean of 40.7 hours (95% CI, 58.0 to 23.5 hours, P < .001). The intervention was associated with lower in-hospital (13.2% to 5.8%, P = .047) and 30-day (17.9% to 8.3%, P = .025) mortality. Conclusions Compared with an ASP-directed response to traditionally detected SAB, an efficient physician response to NAM was associated with improved care and outcomes for SAB.

A single‐center experience with infections due to daptomycin‐nonsusceptible Enterococcus faecium in liver transplant recipients

Infections caused by vancomycin‐resistant Enterococcus faecium (VRE) are a major cause of morbidity and mortality in the liver transplant population. Daptomycin (DAP) is often used to treat infections caused by VRE, but DAP nonsusceptibility in Enterococcus is increasing.

An Infectious Diseases Physician-Led Antimicrobial Stewardship Program at a Small Community Hospital Associated With Improved Susceptibility Patterns and Cost-Savings After the First Year

The importance of antimicrobial stewardship is increasingly recognized, yet data from community hospitals are limited. Despite an initially low acceptance rate, an Infectious Diseases physician-led program at a 70-bed rural hospital was associated with a 42% decrease in anti-infective expenditures and susceptibility improvement in Pseudomonas aeruginosa over 3 years.