Search

Background Azithromycin (AZI) is recommended with ceftriaxone (CRO) for treatment of uncomplicated gonococcal urethritis and cervicitis in the United States, and an AZI-susceptibility breakpoint is needed. Neither the Food and Drug Administration (FDA) nor the Clinical and Laboratory Standards Institute (CLSI) has set interpretive breakpoints for AZI susceptibility. As a result, AZI antimicrobial susceptibility testing (AST) cannot be interpreted using recognized standards. This has contributed to increasingly unavailable clinical laboratory AST, although gonorrhea is on the rise with >550 000 US gonorrhea cases reported to the Centers for Disease Control and Prevention in 2017, the highest number of cases since 1991. Methods This article summarizes the rationale data reviewed by the CLSI in June 2018. Results The CLSI decided to set a susceptible-only interpretive breakpoint at the minimum inhibitory concentration of ≤1 µg/mL. This is also the epidemiological cutoff value (ECV) (ie, the end of the wild-type susceptibility distribution). This breakpoint presumes that AZI (1-g single dose) is used in an approved regimen that includes an additional antimicrobial agent (ie, CRO 250 mg, intramuscular single dose). Conclusions Having a breakpoint can improve patient care and surveillance and allow future development and FDA regulatory approval of modernized AST to guide treatment. The breakpoint coincides with a European Committee on AST decision to remove previously established, differing AZI breakpoints and use the ECV as guidance for testing. The CLSI breakpoint is now the recognized standard that defines AZI susceptibility for gonococcal infections.

Background Patients infected with multi-drug-resistant (MDR) pathogens may experience long delays to targeted therapies due to the incomplete antimicrobial menus and/or breakpoints tested on current commercial antimicrobial susceptibility testing (AST) systems. Detection of carbapenem resistance poses a challenge to rapid, accurate, minimum inhibitory concentrations (MIC) determinations because some resistant organisms may be inhibited by a carbapenem antibiotic until sufficient carbapenemase production has been achieved and traditional AST platforms must wait to make MIC calls. More accurate carbapenem MICs can be determined by implementing a carbapenemase test alongside rapid AST. Methods We demonstrate a novel, proprietary test to detect carbapenemase production that enables rapid MIC testing for carbapenem antibiotics. The test is processed in parallel with the Selux next-generation phenotyping (NGP) AST method, enabling rapid, Results This assay accurately identifies carabapenemases across multiple enzyme classes and bacterial species. Figure 1 shows the accuracy and speed of NGP AST at determining MICs for representative isolates from the FDA-CDC antimicrobial resistance bank compared with results from overnight broth microdilution (BMD). To date, over 100 challenge strains of Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii have been tested with no very major errors and an average time-to-result of 5.3 hours. Conclusion By incorporating a rapid, on-board carbapenemase activity assay, the NGP AST platform rapidly delivers accurate carbapenem results. Combined with NGP’s comprehensive antibiotic menus, this platform will therefore ensure prompt delivery of personalized antibiotic therapies for all patients, including those infected with MDROs, and enable streamlined antibiotic stewardship coordination. Disclosures All authors: No reported disclosures.

Objectives The scope of activities performed by clinical laboratory directors is sometimes unfamiliar to other physicians or hospital administrators. Consequently, hospital leadership may undervalue the role and assume that many director level activities could be delegated to a professional manager. In this study, we sought to define the activities of academic laboratory directors, and to determine which activities require doctorate level medical or scientific expertise. Methods We performed an audit of laboratory director activities at a large academic medical center by reviewing electronic calendars and other available records from the preceding 12 consecutive months. For episodic activities, the directors estimated the average number of hours devoted over the 1-year period. Results On average, directors worked 54.9 hours per week and performed at least some service work 47.7 weeks per year. Administrative duties accounted for the greatest proportion of effort (47.1%), followed by clinical activities (33.1%) and academic activities (19.8%). Among administrative duties, those that required doctorate level medical or scientific expertise comprised 60.3% of the total administrative effort, whereas the remaining 39.7% (18.7% of total activity) could be performed by a professional manager.. Conclusions Although the activities of clinical laboratory directors have been described elsewhere, this is the first study detailing the effort allocated to these various activities in quantitative terms. The study demonstrated that less than 20% of an academic laboratory director's effort involves administrative activities that could potentially be performed by a professional manager lacking doctorate level medical or scientific expertise.

Widespread resistance in Enterobacteriaceae and Pseudomonas aeruginosa to cephalosporin and monobactam antibiotics due to extended-spectrum β-lactamases (ESBLs) has resulted in the need for reassessment of the interpretative criteria (breakpoints) established for these agents more than 2 decades ago. Following extensive evaluation, the Clinical and Laboratory Standards Institute recently adopted and published new breakpoints for these agents for use in clinical laboratories and provided updated recommendations for use of the ESBL screening test. This paper summarizes the background and supportive rationale for new interpretative criteria for cephalosporins and aztreonam for testing Enterobacteriaceae.

Background Standard 2-tiered immunoglobulin G (IgG) testing has performed well in late Lyme disease (LD), but IgM testing early in the illness has been problematic. IgG VlsE antibody testing, by itself, improves early sensitivity, but may lower specificity. We studied whether elements of the 2 approaches could be combined to produce a second-tier IgG blot that performs well throughout the infection. Methods Separate serum sets from LD patients and control subjects were tested independently at 2 medical centers using whole-cell enzyme immunoassays and IgM and IgG immunoblots, with recombinant VlsE added to the IgG blots. The results from both centers were combined, and a new second-tier IgG algorithm was developed. Results With standard 2-tiered IgM and IgG testing, 31% of patients with active erythema migrans (stage 1), 63% of those with acute neuroborreliosis or carditis (stage 2), and 100% of those with arthritis or late neurologic involvement (stage 3) had positive results. Using new IgG criteria, in which only the VlsE band was scored as a second-tier test among patients with early LD (stage 1 or 2) and 5 of 11 IgG bands were required in those with stage 3 LD, 34% of patients with stage 1, 96% of those with stage 2, and 100% of those with stage 3 infection had positive responses. Both new and standard testing achieved 100% specificity. Conclusions Compared with standard IgM and IgG testing, the new IgG algorithm (with VlsE band) eliminates the need for IgM testing; it provides comparable or better sensitivity, and it maintains high specificity.

An important task of the clinical microbiology laboratory is the performance of antimicrobial susceptibility testing of significant bacterial isolates. The goals of testing are to detect possible drug resistance in common pathogens and to assure susceptibility to drugs of choice for particular infections. The most widely used testing methods include broth microdilution or rapid automated instrument methods that use commercially marketed materials and devices. Manual methods that provide flexibility and possible cost savings include the disk diffusion and gradient diffusion methods. Each method has strengths and weaknesses, including organisms that may be accurately tested by the method. Some methods provide quantitative results (eg, minimum inhibitory concentration), and all provide qualitative assessments using the categories susceptible, intermediate, or resistant. In general, current testing methods provide accurate detection of common antimicrobial resistance mechanisms. However, newer or emerging mechanisms of resistance require constant vigilance regarding the ability of each test method to accurately detect resistance.

Background Examination of multiple stool specimens per patient to rule out parasitic infection continues to be recommended in the literature. Attractive alternatives have been proposed, such as examination of a single specimen, but data to support their use have been inconclusive. Methods We reviewed the results of comprehensive stool ova and parasite examinations performed during a 1-year period to determine the incremental value of examining >1 specimen. Next, we implemented rejection criteria, allowing analysis of only a single specimen in most cases, and studied the impact of the change by reviewing data from a subsequent year. Results Prior to implementation of rejection criteria, 91% of parasites were detected in the first specimen submitted, although many clinical evaluations (72%) involved the submission of only 1 stool specimen. When at least 3 specimens were submitted, the sensitivity of examining the first in the series was 72%. Even the latter sensitivity provides negative predictive values of approximately 98%, approximately 97%, approximately 95%, or approximately 93% when the prevalence of parasites among those tested is 5%, 10%, 15%, or 20%, respectively. Examination of additional specimens after examination of the first specimen that yielded a positive finding revealed previously undetected parasites in only 10% of cases. After the application of rejection criteria, the parasite detection rate did not change significantly. Conclusions Comprehensive examination of a single stool specimen is sufficient for most patients, when the prevalence of infection among the tested population is up to 20%. Rational use of the stool ova and parasite examination relies on communication between clinician and laboratory, and retention of deferred specimens in case examination of additional specimens is clinically warranted.

Clinical microbiology laboratories are faced with the challenge of accurately detecting emerging antibiotic resistance among a number of bacterial pathogens. In recent years, vancomycin resistance among enterococci has become prevalent, as has penicillin resistance and multidrug resistance in pneumococci. More recently, strains of methicillin-resistant Staphylococcus aureus with reduced susceptibility to vancomycin have been encountered. In addition, molecular techniques have demonstrated that there are still problems detecting methicillin resistance in staphylococci, especially in coagulase-negative species. Among members of the family Enterobacteriaceae, mutated beta-lactamase enzymes may confer difficult-to-detect resistance to later-generation penicillins and cephalosporins. Anaerobic bacteria are no longer entirely predictable in their susceptibility to agents that might be selected for empiric therapy. Therefore, clinical microbiology laboratories may not be able to rely on a single susceptibility testing method or system to detect all those emerging resistant or fastidious organisms. For reliable detection, laboratories may need to employ conventional, quantitative susceptibility testing methods or use specially developed, single concentration agar screening tests for some resistant species. Certain of these screening tests are highly specific, while others may require additional confirmatory testing for definitive results. Therefore, laboratories must retain the versatility to apply several different approaches to detect resistance in both common and infrequently encountered bacterial pathogens.

We report three cases in which Streptobacillus moniliformis was isolated from abscesses. Abscess material in each case contained small, pleomorphic, gram-negative to gram-variable bacilli. Anaerobic blood agar cultures yielded pinpoint colonies adjacent to small gray-white colonies. The pinpoint colonies did not gram stain, and the gray-white colonies varied from gram-variable coccobacilli to long, curly, gram-variable rods. The pinpoint colonies microscopically resembled L-forms on Dienes-stained agar preparation. Subculture to serum-supplemented thioglycolate broth demonstrated "puff ball" colonies. Fatty acid profiles obtained with use of gas chromatography coupled with mass spectrometry showed major peaks for C16:0, C18:2, C18:1, and C18:0 fatty acids, a profile characteristic of S. moniliformis. Results of biochemical testing of each isolate were equivocal. S. moniliformis, bacterial L-forms, and common isolates from genital tract abscesses are discussed.

Rapid tests for influenza antigen detection are frequently used, but it is not known how receipt of intranasal influenza vaccine affects results of these tests. We tested healthy adults who received either intranasal or intramuscular influenza vaccine. Of the 14 intranasal vaccine recipients, 7 (50%) had a direct fluorescent antibody test (DFA) result and 2 (14%) had an enzyme immunoassay (EIA) result that was positive for influenza antigen within 7 days after vaccination. No subjects had positive EIA results on day 12 or 13 after vaccination. For some intranasal vaccine recipients, rapid influenza-antigen detection tests yield positive results within 1 week after vaccination.

1Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, GA, U.S.A 2Massachusetts General Hospital and Harvard Medical School, Boston, MA, U.S.A *Corresponding author: 1600 Clifton Road, MS C‐16, Atlanta, GA 30329; 404.639.2162 (ph); 404.718.2174 (fax); BBL7@cdc.gov **Alternate corresponding author: Microbiology Laboratory, Mailstop GRB 526; Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114; 617.643.2908 (ph); 617.726.5957 (fax); vmpierce@mgh.harvard.edu

The breakpoints used to interpret antimicrobial susceptibility tests should be carefully determined initially, using microbiological, pharmacokinetic, pharmacodynamic, and clinical data, and then reevaluated periodically as changes in bacterial resistance, susceptibility test methods, or antibiotic formulations occur. Throughout the world, different governmental agencies and professional organizations have responsibility for the initial establishment of antibiotic susceptibility breakpoints. In the United States, the National Committee for Clinical Laboratory Standards has a mechanism in place to establish breakpoints initially and to review and publish updates on an annual basis. There should be a continued effort to coordinate both susceptibility testing methods and breakpoint determinations in various parts of the world.

To the EditorIn the 15 February 2008 issue of Clinical Infectious Diseases, Anthony et al. [1] state, in the Methods section of their article, that the "Clinical Laboratory Standards Institute interpretive criteria for Enterobacteriaceae were used for both Enterobacteriaceae and A. baumannii (susceptible MIC, ^2 /?g/mL; intermediate MIC, >2 or

The comparative in-vitro activity of A-56268 (TE-031), a new semisynthetic macrolide antibiotic, was assessed against approximately 400 bacterial isolates. The new drug demonstrated excellent activity against penicillin-susceptible streptococci (MIC90s less than or equal to 0.06 mg/l) and methicillin-susceptible staphylococci (MIC90 = 0.25 mg/l). Among other Gram-positive organisms tested, a significant number were resistant to A-56268 as well as to erythromycin and clindamycin. A-56268 was at least as active as erythromycin against Pasteurella multocida and Campylobacter jejuni, but was more active than erythromycin against Legionella spp. (MIC90 less than or equal to 0.06 mg/l), Bacteroides fragilis (MIC90 = 4 mg/l) and Bact. melaninogenicus (MIC90 less than or equal to 0.125 mg/l). Activity of A-56268 was pH dependent (more active at pH 7 than at pH 6) and was moderately affected by inoculum size. The drug was bactericidal against two strains of Streptococcus pyogenes tested, but exerted a bacteriostatic effect against Staphylococcus aureus and Str. faecalis.