Acinetobacter spp, Stenotrophomonas maltophilia, Burkholderia cepacia

1- Acinetobater species:

  • Gram negative coccobacilli that are non-motile and oxidase negative.
  • They oxidize sugars, but do not ferment, and do not reduce nitrate.
  • Identification to species level is unnecessary for clinical isolate.
  • Nosocomial strains may be multi-drug resistant. Carbapenem resistant strains can occur.

2- Stenotrophomonas maltophilia:

  • Motile, late oxidase positive gram negative rods.
  • They oxidize, but do not ferment sugars.
  • They are DNAse positive.
  • Inherently resistant to carbapenems, which may aid in presumptive identification.

3- Burkholderia cepacia:

  • Motile, oxidase variable gram negative rods.
  • They oxidize, but do not ferment sugars.
  • Isolates are characteristically resistant to polymyxins.

SENSITIVITY TESTING AND REPORTING

MIC testing is preferable to disk diffusion testing for non-fermenters. However, disk diffusion is more convenient for most clinical laboratories.

QC strains must be tested daily to ensure the validity of test results. The following QC strains must be tested:

  • coli ATCC® 29522
  • aeruginosa ATCC® 27853
  • coli ATCC® 35218 (for β-lactam/β-lactamase inhibitor combinations); with disk diffusion and MIC results within the ranges proposed by the CLSI.
  • Acinetobacter spp.
  • Ceftazidime and Imipenem should always be tested and reported.
  • Other agents may be reported as alternative therapeutic options e.g. Fluoroquinolones, tetracyclines, trimethoprim/sulfamethoxazole, aminoglycosides, etc.
  • Polymyxins may be tested by measuring MICs (by broth microdilution or agar dilution) for multi-drug resistant isolates.
  • Alternative antimicrobials in each group are not cross-reportable.
  • Isolates sensitive to tetracycline are usually sensitive to doxycycline and minocycline; however, some tetracycline resistant isolates may be sensitive to either doxycycline and/or minocycline.
  • Stenotrophomonas maltophilia.
  • Trimethoprim/sulfamethoxazole is the therapeutic agent of choice and must always be reported.
  • Carbapenems should not be tested/ reported.
  • Other agents may be reported as alternatives e.g., fluoroquinolones, tetracyclines.
  • Cephems (cephalosporins including ceftazidime), chloramphenicol, and ticarcillin/clavulanate may be reported based on MIC results.
  • Minocycline is the preferable than tetracycline to test against Stenotrophomonas maltophilia strains.
  • Burkholderia cepacia
  • Trimethoprim/sulfamethoxazole is the therapeutic agent of choice and must always be reported.
  • Polymyxins should not be tested/ reported.
  • Other agents may be reported as alternatives e.g. cephems, carbapenems, tetracyclines.
  • Fluoroquinolones, chloramphenicol, and ticarcillin/clavulanate may be reported based on MIC results.

July 2018
Dr.Fizza Faroqui
Year V Resident
Department of pathology and laboratory medicince
Aga Khan University Hospital, Karachi