Diane C. Halstead

Molecular Epidemiology of Carbapenem-Nonsusceptible Acinetobacter baumannii in the United States

ABSTRACT Acinetobacter baumannii is emerging as an important nosocomial pathogen worldwide. We report molecular epidemiology of 65 carbapenem-nonsusceptible A. baumannii isolates identified from hospitals in New York, Pennsylvania, Florida, Missouri, Nevada, and California between 2008 and 2009. All isolates were subjected to pulsed-field gel electrophoresis (PFGE). Select isolates then underwent multilocus sequence typing (MLST). While the PFGE patterns tended to cluster within each hospital, sequence types (STs) belonging to the clonal complex 92 (CC92) and the pan-European clonal lineage II (EUII; worldwide clonal lineage 2) were predominant in all hospitals. Of them, ST122 and ST208 were the most common and were found in four of the six hospitals. Isolates belonging to the pan-European clonal lineages I and III were identified in one hospital each. Carbapenemase-encoding genes bla OXA-23 and/or ISAba1-bla OXA-51-like were present among the majority of isolates. These findings suggest that carbapenem-nonsusceptible A. baumannii isolates found in U.S. hospitals constitute part of the global epidemic driven by CC92, but have unique STs other than ST92, which may be spreading by means of patient transfer between health care facilities within the United States.

Reality of Developing a Community-Wide Antibiogram

Antimicrobial surveillance may be defined as a systematic collection, analysis, and dissemination of data that may be used to identify resistance trends and assess the need for intervention (2). In 1988 the Centers for Disease Control and Prevention published guidelines for evaluation of surveillance systems for antimicrobial resistance (7), and an American Society for Microbiology task force (1) highlighted the importance of performing antimicrobial surveillance through local, national, and global networks. Unfortunately, the recommendations from this task force were not implemented, in part due to lack of funding (6). To this end, however, international as well as more than 21 national programs designed to capture susceptibility data for most clinically significant organisms (e.g., SENTRY and TSN) and 24 programs that focused on specific organisms (e.g., CARE and TRUST), were identified in 1999 through the World Health Organization Antimicrobial Resistance Information Bank (9). These programs may be government (e.g., ICARE and NNIS,), commercial (e.g., TSN), or industry (e.g., ARMp, MYSTIC, PROTEKT, SENTRY, and TRUST) supported. Additional data may be gleaned from postmarketing surveillance studies by pharmaceutical companies who monitor their new antimicrobial for resistance, e.g., MYSTIC (meropenem), SMART (quinupristin-dalfopristin), and ZAP (linezolid). Since testing methods may vary between laboratories and may potentially bias multilaboratory databases, some programs rely on a central laboratory to generate standardized susceptibility data. Quantitative (MIC) rather than qualitative (susceptible, intermediate, and resistant) data and the use of molecular methods, as employed in the MYSTIC and SENTRY programs, generally offer greater value in identifying resistance trends and providing a genetic basis for observed resistance, respectively.

Differences Between Ceftriaxone and Cefotaxime: Microbiological Inconsistencies

Objective: To review data to determine why pneumococcal isolates appear to be increasingly resistant to cefotaxime, historically regarded as having the same in vitro susceptibility to ceftriaxone, and what this observation might imply clinically. Data Sources: Literature was accessed through MEDLINE (1966–October 2007) using the MeSH terms cefotaxime, ceftriaxone, susceptibility, microbial sensitivity tests, antibiotics, pneumococcal infections, Streptococcus pneumoniae. resistance, and cephalosporin resistance. Abstracts and surveillance databases were reviewed and unpublished data were provided by state departments of health and institutions. Study Selection and Data Extraction: All articles published in the English language that were identified from the data sources were evaluated. Data Synthesis: An experimental model of pneumococcal infection in mice conducted 2 decades ago predicted that the delta T minimum inhibitory concentration (MIC) varied less for ceftriaxone than for cefotaxime. Studies of plasma and serum concentrations show that ceftriaxone remains at a concentration above the S. pneumoniae MIC for 100% of the dosing interval al 12 hours. Types of MIC susceptibility test methods for ceftriaxone and cefotaxime used against S pneumoniae respiratory isolates were found to be similar. Data from state and county health departments found microbiological discrepancies between ceftriaxone and cefotaxime. In areas with high rates of penicillin-resistant S. pneumoniae (PRSP), isolates were twice as susceptible to ceftriaxone versus cefotaxime. Surveillance databases consistently show differences between susceptibility of S. pneumoniae to cefotaxime versus ceftriaxone over time. MIC and pulsed-field gel electrophoresis studies suggest that phenotypic discrepancies may account for ponicillin resistance. Ongoing studies are examining S. pneumoniae isolates at the molecular level to determine the basis of difference in resistance to cefotaxime and ceftriaxone. Conclusions: An increase in rates of PRSP and differences in S. pneumoniae isolate susceptibility between ceftriaxone and cefotaxime emphasize the necessity for hospital laboratories to detect these changes as they occur. Clinicians should select the most appropriate agent for patients with S. pneumoniae.

Infectious Endocarditis in 49-Year-Old Man and Discussion of Phenotypic Characteristics of Aerococcus urinae and Viridans Streptococci.

PATIENT 49 year-old man. CHIEF COMPLAINT Dyspnea at rest and dyspnea on exertion. HISTORY OF PRESENT ILLNESS Diagnosed with upper respiratory tract infection 10 days previously. PAST MEDICAL HISTORY Obese (BMI not available), but no significant past medical history. SOCIAL HISTORY Noncontributory. FAMILY HISTORY Noncontributory.

Klebsiella pneumoniae Carbapenemase-producing Enterobacteriaceae, Northeast Florida.

Background: Since 2001 there have been several reported outbreaks due to carbapenem-resistant Klebsiella pneumoniae (Kp), particularly in the northeastern states. Methods: Carbapenemase-producing Enterobacteriaceae from healthcare facilities in Northeast Florida were phenotypically identified and confirmed using PCR amplification and sequencing of the blaKPC gene. Results: Results from PFGE analysis of these isolates demonstrated possible horizontal spread from two possible “outbreak” strains during the study period. Conclusions: We present the first published cluster of Kp and Escherichia coli (Ec) cases in Florida carrying the KPC-2 or KPC-3 gene.

A multi-laboratory comparison of two molecular methods for the detection of toxigenic Clostridium difficile

INTRODUCTION Diarrheal disease due to toxigenic Clostridium difficile (CD) accounts for an increased number of hospitalizations and deaths each year. Published guidelines recommend reflex testing of CD antigen-positive samples to molecular testing or testing samples directly by a molecular assay. This multicenter study was designed to compare the accuracy of two different molecular methods targeting different CD genes: Xpert C. difficile Epi RUO RT-PCR assay (XPCR) which targets toxin B (Cepheid, Sunnyvale, CA) and a laboratory-developed PCR (LDPCR) which targets mutations in the tcdC regulatory gene. METHODOLOGY Two molecular methods for toxigenic CD detection, the Xpert C. difficile Epi RUO RT-PCR assay (XPCR) [Cepheid, Sunnyvale, CA] and a laboratory-developed PCR assay (LDPCR) were compared to a consensus gold standard (CGS) or toxigenic culture (TC) as the reference method. A subset of specimens was subjected to additional molecular characterization of toxigenic CD. RESULTS Both molecular methods were >90% sensitive for CD detection. Discordant results were noted when molecular test results were compared to non-molecular methods. Supplemental molecular characterization illustrated inherent difficulties in comparisons using different molecular methods for CD. CONCLUSION Laboratories may consider using multiple CD detection methods or combinations of methods, including molecular detection for rapid and accurate diagnosis of CD, as driven by best practices for the respective healthcare environment. Laboratories must be aware of intrinsic differences when comparing performance characteristics of different molecular assays.

Respiratory virus identification by interval polymerase chain reaction testing in the southeastern United States

BACKGROUND This study was designed to determine if testing the first ~40 nasal washings (interval) each month for 1 year, could be used as an epidemiologic tool for seasonality and prevalence of respiratory viruses such as human metapneumovirus in an adult and pediatric population in the southeastern United States. MATERIALS AND METHODS Results of interval polymerase chain reaction (PCR) testing of 469 specimens for 8 viruses were compared with our current procedures using PCR, culture, or respiratory synctial virus antigen for all 7435 specimens (routine). RESULTS One hundred thirty-six viruses out of 469 specimens (29.0%) and 1,495 viruses out of 7,435 specimens (20.1%) were identified by interval and routine testing, respectively. Seasonal detection varied among viruses and to some degree between interval and routine testing. A higher percent of positives and dual infections were detected by interval testing of pediatric specimens, likely due to the use of PCR for viruses commonly seen in this population. Human metapneumovirus was detected in both pediatric and adult specimens between January and August. CONCLUSIONS Interval testing can be used to provide a snapshot of prevalence and seasonality of respiratory viruses, although as currently designed they may not be sensitive enough to identify the beginning of a specific virus season. Exclusive use of interval PCR testing identified several dual infections, including human metapneumovirus, throughout most of the year in Florida. A rapid turnaround time to results translates into improved infection control and improved patient care.

Executing Successful Performance Appraisals and Competency Assessments

A performance appraisal is a planned, motivational management tool used to evaluate an employee’s on-the-job behavior and to determine compensation, training needs, and career decisions. The appraisal should include clearly defined expectations, a valid and fair performance assessment, and documentation and follow-up of a plan for improvement. Formal appraisals should be performed by trained individuals to ensure that evaluations are non-discriminatory and confidential since they are discoverable in a court of law. Appraisals are generally position-specific and competency-based, using a rating system to measure the employee’s performance. Certified laboratories must according to CLIA ’88, show documented evidence of performance appraisals and semi-annual competency assessment of pre-analytical, analytical, and post-analytical processes as well as following implementation of any new method or instrument.