Match each clinical scenario involving an emergent or highly drug-resistant infection to the precise molecular mechanism responsible for its antimicrobial resistance profile.
- A 64-year-old critically ill patient with relapsing fungemia develops breakthrough infection with Candida glabrata while receiving empiric micafungin therapy.Mutations in FKS1 or FKS2 genes resulting in reduced binding affinity of the target enzyme complex.
- A 28-year-old patient presents with disseminated gonococcal infection; isolates demonstrate high-level minimum inhibitory concentrations to ceftriaxone, prompting treatment with alternative agents.Acquisition of mosaic penA alleles leading to structural modifications in penicillin-binding protein 2.
- A 45-year-old agricultural worker with no prior antifungal exposure is diagnosed with invasive pulmonary aspergillosis; cultures yield Aspergillus fumigatus that is pan-resistant to itraconazole and voriconazole.Environmental acquisition of the tandem repeat TR34 and L98H mutation in the cyp51A gene.
- A 71-year-old ICU patient is treated for carbapenem-resistant Klebsiella pneumoniae with ceftazidime-avibactam; the isolate develops resistance to the regimen during therapy while regaining susceptibility to imipenem.Amino acid substitutions in the omega loop of a class A serine carbapenemase, altering its active site.
- A 55-year-old with multidrug-resistant tuberculosis is started on a bedaquiline-containing regimen; after 3 months, the isolate demonstrates high-level resistance to both bedaquiline and clofazimine.Mutations in the Rv0678 transcriptional repressor gene leading to upregulation of the MmpS5-MmpL5 efflux pump.
Answer
The accurate molecular resistance pairings are: C. glabrata (micafungin resistance) with FKS1/FKS2 mutations; N. gonorrhoeae (ceftriaxone resistance) with mosaic penA alleles; A. fumigatus (environmental azole resistance) with cyp51A TR34/L98H mutations; K. pneumoniae (ceftazidime-avibactam resistance / imipenem susceptibility) with KPC omega loop mutations; and M. tuberculosis (bedaquiline/clofazimine resistance) with Rv0678 efflux pump upregulation.
Each pathogen-phenotype pair maps exclusively to a specific genetic alteration. FKS mutations disrupt echinocandin binding in Candida. Mosaic penA structural changes prevent ceftriaxone binding in Neisseria. The TR34/L98H cyp51A mutation is the hallmark of environmentally acquired azole resistance in Aspergillus. KPC omega-loop mutations uniquely enhance ceftazidime hydrolysis while sacrificing carbapenemase activity. Finally, Rv0678 mutations in MTB upregulate the MmpS5-MmpL5 efflux pump, creating dual resistance to bedaquiline and clofazimine.
Step-by-Step Solution
Key Concept
Molecular mechanisms of advanced antimicrobial resistance in emergent pathogens