APHL 2022 POSTER ABSTRACTS
Infectious Diseases
Clinical Evaluation of a Commercially Available Chromogenic Agar for Detection of Candida auris at a Large Academic Health Center Clinical Microbiology Laboratory
B Whitacre 1 , K Gavina 2 , K Van Benten 1 , J Lavik 1 , C Emery 1 , R Relich 1 ;
1
IUHealth , 2 Indiana University School of Medicine
Background : Candida auris , an often multi-drug resistant yeast of global health significance , can cause nosocomial outbreaks and easily be misidentified using standard laboratory methods . Global case counts may be underestimated and there is a need for more accurate , reliable , affordable and accessible identification test methods . HardyCHROM™ Candida + auris is a selective and differential medium used to identify C . auris , Candida albicans , Candida glabrata , Candida krusei and Candida tropicalis . We evaluated HardyCHROM™ Candida + auris media and assessed how it could be used to improve laboratory efficiency and reduce potential workplace hazards by relying on manual visualization of colonies without exposing personnel .
Methods : Clinical isolates ( n = 30 ) of C . auris ( appear white with a teal bullseye center and a fluorogenic reaction under UV light ), C . albicans , C . glabrata , C . krusei and C . tropicalis were tested , as well as six clinical isolates and reference strain ( ATCC 22019 ) of C . parapsilosis . Current lab protocol for positive identification of C . auris ( SAB + HardyCHROM™ Candida plates ) was used as the reference identification method . Colonies with indeterminate results by manual visualization were identified by mass spectrometry .
Results : Clinical isolates of C . auris , C . albicans , C . glabrata , C . krusei and C . tropicalis were identified as expected using the manufacture ’ s procedure under ambient lighting . C . auris , C . albicans and C . parapsilosis clinical isolates fluoresced under UV light . C . parapsilosis ( the clinical isolates and ATCC strain ), grew as a mixture of white or teal with colonies that exhibited a teal bullseye center , fluoresced under UV light , and were subsequently misidentified as C . auris .
Conclusions : We found that HardyCHROM™ Candida + auris plates can be used to easily distinguish among C . albicans , C . glabrata , C . krusei and C . tropicalis and from C . auris . However , C . parapsilosis was not easily distinguished from C . auris . Using fresh and frozen clinical isolates and our ATCC strain of C . parapsilosis , we could not rule out C . auris growth on the plates , phenotypically . Considering that C . parapsilosis is often encountered , HardyCHROM™ Candida + auris plates should be utilized with caution and alongside additional methods of identification to distinguish it from C . auris .
Presenter : Brynne Whitacre , Indiana University Health , bewhitac @ iu . edu
Identification of Blastomyces dermatitidis , Blastomyces gilchristii and Histoplasma capsulatumu using Multiplex Real-time PCR
E Stanton , J Dale , E Lundquist , A Gross and . Snippes Vagnone , Minnesota Department of Health
Blastomyces dermatitidis , Blastomyces gilchristii and Histoplasma capsulatum are dimorphic fungi that belong to the Ajellomycetaceae family . Dimorphic fungi switch between filamentous growth in the environment to yeast-like growth in the animal host . Blastomyces and Histoplasma are responsible for significant respiratory mycoses in North America , share similar geographic distributions and patients can present with similar symptoms . Culture-based methods of identification require conversion to the yeast phase which requires lengthy incubation and extensive expertise in mycology . Molecular diagnostics using the AccuProbe ® system rely on nucleic acid hybridization using probes complementary to ribosomal RNA . These assays are being phased out by the manufacturer . Therefore , the development of alternative methods for identification of Blastomyces and H . capsulatum are needed . No commercially available methods exist to differentiate between B . dermatitidis and B . gilchristii . Data regarding potential differences in pathogenicity , epidemiology and ecology between Blastomyces species are also lacking . Based upon previously published methods , we validated a multiplex real-time PCR ( RT-PCR ) assay to distinguish between Blastomyces species and H . capsulatum by amplification of the BAD1 and GADPH loci . Sequence variations within BAD1 were used to differentiate between B . dermatitidis and B . gilchristii , while GADPH was used to identify H . capsulatum . Isolates tested for validation of this assay were speciated by AccuProbe ® and culture confirmation , whole-genome sequencing or laboratory developed RT- PCR methods . Results from the multiplex RT-PCR validation showed accurate speciation of MDH Blastomyces isolates and correctly identified H . capsulatum . Implementation of a B . dermatitidis , B . gilchristii and H . capsulatum multiplexed RT-PCR assay enabled a rapid turn-around-time and will allow for a better understanding of the epidemiology of these organisms in Minnesota .
Presenter : Eliot Stanton , Minnesota Department of Health , eliot . stanton @ state . mn . us
Laboratory Investigation of an Outbreak of Serratia marcescens Infections among Incarcerated Persons at a State Prison
D Ferguson 1 , H Dowless 2 , R Lunsford 1 , A Krassa 1 , R Ryder 1 , R Chresaidos 1 , S Riddick 1 , M Colbert 1 ; 1 Monterey County Public Health Laboratory , 2 California Department of Corrections and Rehabilitation
Background : Serratia marcescens is a gram-negative bacterium that naturally occurs in soil and water but can survive in manmade environments , including disinfectant solutions , and has been the cause of nosocomial outbreaks . In 2020 – 21 , an outbreak of invasive S . marcescens infections ( e . g ., osteomyelitis , endocarditis , etc .) at a state prison was investigated . From March 2020 through August 2021 , 22 patients with S . marcescens infection were identified ; most reported recent injection drug use ( IDU ). This investigation included a robust laboratory component to identify the source of the infections .
Methods : MC PHL collected and tested large volumes of water from various sources , including holding tanks , wells and faucets from case-patient cells and a variety of environmental samples from case-patient cells , such as sinks , re-used bottles and containers used to store CB64 , a dilutable quaternary ammonium-based cleaner that is the primary disinfectant for the prison , scrub pads used for cleaning (“ scrubbies ”) and communal showers . Two needle / syringes were also collected for testing . Samples were collected from devices and containers used for mixing , storing or applying disinfectant and cleaners , such as dilution machines , reused containers and a mop bucket .