Evaluation of the accuracy of phenotypic methods proposed by reference manuals in the Klebsiella pneumoniae carrier classification of the blaKPC gene.
Name: JAQUELINE PEGORETTI GOULART
Publication date: 12/04/2017
Advisor:
Name |
Role |
|---|---|
| ANA PAULA FERREIRA NUNES | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| ANA PAULA FERREIRA NUNES | Advisor * |
| KÊNIA VALÉRIA DOS SANTOS | External Alternate * |
| LILIANA CRUZ SPANO | Internal Examiner * |
| MOISES PALACI | Internal Alternate * |
Summary: Hospital infections caused by multidrug resistant bacteria constitute a serious public health problem worldwide associated with treatment failure and higher mortality rates. Among Enterobacteriaceae family, KPC-producing K. pneumoniae is an important pathogen responsible for these infections and have received the most attention because they have high potential to spread. Accurate detection of KPC producers is essential for infection control measures and antibiotic therapy. However, this is a major issue in microbiology laboratories, because the current clinical breakpoints used by reference guidelines are not capable to detect all carbapenemase producers and none confirmatory tests have 100% sensibility and specificity. The aim of the study was to evaluate methods and interpretative criteria proposed in Clinical and Laboratory Standards Institute (CLSI) and Brazilian Committee on Antimicrobial Susceptibility Testing (BrCAST) manuals to detect carbapenemase production in 47 K. pneumoniae clinical samples carrying blaKPC gene. The carbapenems susceptibility testing and the screening criteria to select samples to perform confirmatory tests (Modified Hodge Test and Inhibitor-based method) were performed through disk diffusion method and minimum inhibitory concentration (MIC) determination and was interpreted according clinical breakpoints proposed by both guidelines. All clinical samples were classified as MDR (non-susceptibility to at least three antimicrobial classes). The results support that carbapenems clinical breakpoints plus criteria of screening to select strains proposed by BrCAST presented better performance to correctly select K. pneumoniae possessing blaKPC strains to confirmatory tests. It is important to use all three carbapenems to ensure higher accuracy in susceptible testing. Furthermore, was observed that disk diffusion method applying BrCAST criteria was the only capable to correctly select all strains to confirmatory tests. Both confirmatory tests were able to identify carbapenemase production in the same 40 strains. Seven strains showed negative results on confirmatory tests in despite of the presence of blaKPC gene.
