Ann Croft

Publications of Ann Croft

• Performance of the Phoenix bacterial identification system compared with disc diffusion methods for identifying extended-spectrum {beta}-lactamase, AmpC and KPC producers.

  Authors: Mark A Fisher, Paul D Stamper, Kristine M Hujer, Zachary Love, Ann Croft, Samuel Cohen, Robert A Bonomo, Karen C Carroll, Cathy A Petti

  Journal of medical microbiology. 07/2009; 58(Pt 6):774-8.

  Phenotypic identification of AmpC, KPC and extended-spectrum beta-lactamases (ESBLs) among members of the Enterobacteriaceae remains challenging. This study compared the Phoenix AutomatedPhenotypic identification of AmpC, KPC and extended-spectrum beta-lactamases (ESBLs) among members of the Enterobacteriaceae remains challenging. This study compared the Phoenix Automated Microbiology System (BD Diagnostics) with the Clinical and Laboratory Standards Institute confirmatory method to identify ESBL production among 200 Escherichia coli and Klebsiella pneumoniae clinical isolates. The Phoenix system misclassified nearly half of the isolates as ESBL-positive, requiring manual testing for confirmation. Inclusion of aztreonam+/-clavulanic acid (CA) and cefpodoxime+/-CA in the testing algorithm increased the ESBL detection rate by 6 %. Boronic acid-based screening identified 24 isolates as AmpC(+), but in a subset of genotypically characterized isolates, appeared to have a high false-positivity rate. PCR screening revealed eight KPC(+) isolates, all of which tested as ESBL(+) or ESBL(+) AmpC(+) by phenotypic methods, but half were reported as carbapenem-susceptible by the Phoenix system. Overall, these results indicate that laboratories should use the Phoenix ESBL results only as an initial screen followed by confirmation with an alternative method.

• Evaluation of partial 16S ribosomal DNA sequencing for identification of nocardia species by using the MicroSeq 500 system with an expanded database.

  Authors: Joann L Cloud, Patricia S Conville, Ann Croft, Dag Harmsen, Frank G Witebsky, Karen C Carroll

  Journal of clinical microbiology. 03/2004; 42(2):578-84.

  Identification of clinically significant nocardiae to the species level is important in patient diagnosis and treatment. A study was performed to evaluate Nocardia species identification obtained byIdentification of clinically significant nocardiae to the species level is important in patient diagnosis and treatment. A study was performed to evaluate Nocardia species identification obtained by partial 16S ribosomal DNA (rDNA) sequencing by the MicroSeq 500 system with an expanded database. The expanded portion of the database was developed from partial 5' 16S rDNA sequences derived from 28 reference strains (from the American Type Culture Collection and the Japanese Collection of Microorganisms). The expanded MicroSeq 500 system was compared to (i). conventional identification obtained from a combination of growth characteristics with biochemical and drug susceptibility tests; (ii). molecular techniques involving restriction enzyme analysis (REA) of portions of the 16S rRNA and 65-kDa heat shock protein genes; and (iii). when necessary, sequencing of a 999-bp fragment of the 16S rRNA gene. An unknown isolate was identified as a particular species if the sequence obtained by partial 16S rDNA sequencing by the expanded MicroSeq 500 system was 99.0% similar to that of the reference strain. Ninety-four nocardiae representing 10 separate species were isolated from patient specimens and examined by using the three different methods. Sequencing of partial 16S rDNA by the expanded MicroSeq 500 system resulted in only 72% agreement with conventional methods for species identification and 90% agreement with the alternative molecular methods. Molecular methods for identification of Nocardia species provide more accurate and rapid results than the conventional methods using biochemical and susceptibility testing. With an expanded database, the MicroSeq 500 system for partial 16S rDNA was able to correctly identify the human pathogens N. brasiliensis, N. cyriacigeorgica, N. farcinica, N. nova, N. otitidiscaviarum, and N. veterana.

• Description of a multiplex Bordetella pertussis and Bordetella parapertussis LightCycler PCR assay with inhibition control.

  Authors: Joann L Cloud, Weston C Hymas, Arthur Turlak, Ann Croft, Udo Reischl, Judy A Daly, Karen C Carroll

  Diagnostic microbiology and infectious disease. 08/2003; 46(3):189-95.

  While culture for Bordetella species is highly specific, sensitivity is extremely variable due to patient age, immunization status, antibiotic treatment, and specimen transport conditions. WeWhile culture for Bordetella species is highly specific, sensitivity is extremely variable due to patient age, immunization status, antibiotic treatment, and specimen transport conditions. We evaluated a real-time multiplex PCR assay as an alternative to culture for the detection and differentiation of Bordetella pertussis and Bordetella parapertussis. The PCR conditions allowed the simultaneous detection of one B. pertussis organism and five B. parapertussis organisms per reaction. An inhibition control was incorporated into the assay. Of 163 total samples evaluated, 37 of 38 samples positive by either culture or direct fluorescent antibody testing (DFA) were also positive by PCR (97% sensitivity). Of 125 culture- or DFA-negative samples, 101 were also negative by PCR (81% specificity). The described multiplex assay is a rapid, sensitive, contamination-limiting, real-time PCR assay that controls for inhibition. The assay performs well using liquid or swab samples and from dried material on slides.

• Spotting the spirochete: rapid diagnosis of leptospirosis in two returned travelers.

  Authors: Stephanie S Gelman, Adi V Gundlapalli, DeVon Hale, Ann Croft, Musa Hindiyeh, Karen C Carroll

  Journal of travel medicine : official publication of the International Society of Travel Medicine and the Asia Pacific Travel Health Association. 9(3):165-7.