Acinetobacter baumannii is an important nosocomial pathogen that often causes infections in patients in the intensive care unit. An ICU patient was diagnosed with a ventilator-associated Acinetobacter baumannii infection. Initial susceptibility analysis indicated that minimum inhibitory concentrations for various antibiotics were; amoxycillin MIC 256 μg/mL, ampicillin plus clavulanic acid MIC 256 μg/mL, imipenem MIC 64 μg/mL and colistin MIC

Question

Acinetobacter baumannii is an important nosocomial pathogen that often causes infections in patients in the intensive care unit. An ICU patient was diagnosed with a ventilator-associated Acinetobacter baumannii infection. Initial susceptibility analysis indicated that minimum inhibitory concentrations for various antibiotics were; amoxycillin MIC >256 μg/mL, ampicillin plus clavulanic acid MIC > 256 μg/mL, imipenem MIC <0.5 μg/mL, tigecycline MIC 10 μg/mL, amikacin MIC > 64 μg/mL and colistin MIC < 0.5 μg/mL.

Initial treatment failed and upon rechecking the MIC analyses, the isolated strain showed an MIC for colistin of 64 μg/mL. The pmrA, pmrB and pmrC genes were sequenced in both the colistin-sensitive parent and also in the newly colistin-resistant strain. This analysis identified a mutation in pmrB that would result in an amino acid change in PmrB compared to the sensitive parent.

What do you predict the role of this mutation is in the observed colistin resistance?

Answer

The mutation in PmrB would lead to increased activity of the PmrB protein, which in turn increases expression of the phosphoethanolamine transferase PmrA

Answer

The mutation in PmrB would inactivate the phosphoethanolamine transferase PmrB, which would result in loss of lipopolysaccharide production

Answer

The mutation in PmrB would lead to increased activity of the PmrB protein, which in turn increases expression of the phosphoethanolamine transferase PmrC

Answer

The mutation in PmrB would lead to increased expression of the phosphoethanolamine transferase PmrB and production of lipopolysaccharide with reduced negative charge

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Acinetobacter baumannii is an important nosocomial pathogen that often causes in...

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