Lab Matters Fall 2024 | Page 63

APHL 2024 POSTER ABSTRACTS

( mCIM ) at the Nebraska Public Health Laboratory ( NPHL ) as a costeffective , rapid and reliable method to screen carbapenem-resistant Enterobacterales ( CRE , to include both intermediate and resistant ) for the presence of a carbapenemase gene .

Methods : The mCIM assay is performed according to CLSI ( Clinical and Laboratory Standards Institute ) methods on CRE isolates , determined by phenotypic methods to be intermediate ( MIC 2-4 µ g / ml ) or resistant ( MIC ≥8 µ g / ml ) to ertapenem or imipenem with varying results for meropenem . These isolates were submitted to the NPHL from clinical laboratories throughout Nebraska . Following mCIM screening , all isolates with indeterminate or positive mCIM results were further tested by the Cepheid Xpert ® Carba-R assay ( CARBAR ) and whole genome sequencing ( WGS ).

Results : A total of 586 CRE isolates were evaluated by the NPHL using the mCIM assay in 2023 . The results of testing were , 549 isolates screened negative , 27 tested indeterminate and 10 tested positive . Of the 37 indeterminate and positive isolates , five were identified as mCIM positive , which also tested positive by the CARBAR assay ( 3 OXA-48-like and 2 KPC ). All CPE isolates were reflexed to WGS and confirmed the presence of the five previously identified major carbapenemase genes . WGS also identified a variety of less common beta-lactamase-producing genes in the remaining 32 isolates , to include variants of the blaMIR , the blaACT and blaSHV genes . None of the isolates were related by SNP analysis .

Conclusion : In this study , utilization of the mCIM for screening of CRE allowed the NPHL to use a simple , cost-effective , rapid and reliable alternative method to screen for carbapenemase production as a means to support epidemiological investigating on a more timely basis .

Presenter : Peter Iwen , piwen @ unmc . edu

Utilization of the Modified Carbapenem Inactivation Method ( mCIM ) to Detect for Carbapenemase Production in Carbapenem-resistant Klebsiella ( Enterobacter ) aerogenes , Nebraska 2023

A . Roden , B . Ayers , A . Bartling , E . McCutchen , S . McGill , P . Iwen , Nebraska Public Health Laboratory

Introduction : Carbapenemase-producing Enterobacterales ( CPE ) have emerged as a serious threat in healthcare settings . Although multiple mechanisms exist that can result in carbapenem resistance , only about 30 % is due to the presence of a carbapenemase gene located on a motile element which can easily be spread . As participants in the CDC ’ s Antimicrobial Resistance Lab Network , public health laboratories have developed multiple test methods to detect for CPE . This report describes the results of using the modified carbapenem inactivation method ( mCIM ) to screen carbapenem-resistant or intermediate Klebsiella aerogenes ( CRKA ) for the presence of a carbapenemase gene .

Methods : The mCIM assay was performed according to CLSI ( Clinical and Laboratory Standards Institute ) methods on CRKA isolates submitted to the Nebraska Public Health Laboratory from clinical laboratories throughout Nebraska . All isolates submitted were determined by phenotypic methods at submitting facilities to be resistant to cefoxitin and cefazolin ( MIC > 16 µ g / ml ) and intermediate ( MIC 2-4 µ g / ml ) or resistant ( MIC ≥8 µ g / ml ) to ertapenem or imipenem while susceptible to meropenem ( MIC≤1 µ g / ml ). Following mCIM screening at the NPHL , all isolates with indeterminate or positive results by mCIM testing were further tested by the Cepheid Xpert ® Carba-R ( CARBAR ) assay and whole genome sequencing ( WGS ).

Results : A total of 240 CRKA isolates were evaluated by the NPHL in 2023 . Of these , 226 CRKA isolates screened negative by the mCIM assay while 13 isolates tested indeterminate and one isolate tested mCIM positive . Of these 14 isolates , all tested negative by the CARBAR assay and negative by WGS for a carbapenemase gene , but positive for the amp-C gene . None of the isolates were related by SNP analysis .

Conclusion : In this study , CRKA intermediate or resistant to ertapenem and / or imipenem , but susceptible to meropenem by phenotypic testing did not harbor a carbapenemase gene following WGS analysis . From an economic standpoint , these results showed that CRKA with this antimicrobial susceptibility testing ( AST ) pattern could be excluded from further testing to detect for a carbapenemase gene . These results showed that CRKA strains that are susceptible to meropenem could be included with Morganella morganii , Proteus species and Providencia species that have a similar AST pattern . These resistant strains are thus classified as having elevated resistance to ertapenem and / or imipenem , most likely due to hyperproduction of beta-lactamase following detection of the amp-C gene and not a carbapenemase gene .

Presenter : Amy Roden , amy . roden @ unmc . edu

Viral Hemorrhagic Fever Inactivation Occurs with Detergent and Heat

N . Scott , B . Harcourt , Centers for Disease Control and Prevention

The viruses that cause viral hemorrhagic fevers are primarily Risk Group 4 viruses requiring Biosafety Level ( BSL ) 4 containment . Serological assays are used as a vital tool for diagnostic purposes and tracking the seroprevalence of these viruses in both humans and animals . To safely perform these assays outside of BSL-4 containment , the specimens must first be inactivated . At CDC , the specimens are inactivated using a validated procedure by incubating in a diluent containing the detergent Tween-20 at a concentration of 0.5 %, followed by exposure to 2x106 rads of gamma irradiation . For field work , where BSL-4 containment is not available , or if gamma irradiation is not possible , an alternative inactivation procedure utilizing incubation in a field diluent ( FD ) containing 0.5 % Tween-20 and 0.5 % TritonX-100 and incubation at 56 ° C for 30 minutes is used . We are doing this study to generate inactivation data against a range of viruses , starting with Rift Valley Fever virus to determine if either heat alone , field diluent alone , or a combination of both is required to achieve inactivation .

Here , we challenged and evaluated the impact of time , heat , FD with heat and FD alone to determine the optimal viral inactivation conditions in whole blood . We have observed that FD alone inactivates Rift Valley Fever Virus ( RVFV ) and are further investigating the dynamics that heat and time have on whole blood viral inactivation . After defining the ideal condition for RVFV , we will identify the ideal inactivation conditions for Ebola virus , Lassa virus and Crimean Congo Hemorrhagic Fever virus .