A standardised approach to the treatment and management of significant acinetobacter species infection at academic complex hospitals in KwaZulu-Natal.
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Date
2017
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Abstract
Introduction: Carbapenem-resistant Acinetobacter species (Acinetobacter spp.) are increasingly
recognised as important pathogens, whose resistance patterns present a high-risk global challenge.
However, there is limited scientific data and a lack of a standardised approach to help the clinician
select optimal therapy in local setting. This study aimed to provide a standardised approach for
the management of significant Acinetobacter spp. infection based on phenotypic and genotypic
characterisation of local isolates, as well as clinical characteristics and outcomes of patients at
academic complex hospitals in KwaZulu-Natal.
Objectives: The significance of Acinetobacter spp. infections and the most effective drug
combinations for optimal therapy were determined. Acinetobacter spp. isolates were
phenotypically and genotypically characterised. This was followed by the development of a
standard management guideline for local use, based on the data obtained in the different
objectives.
Methods: The research consisted of a retrospective and prospective observational and
experimental laboratory component. The laboratory component included synergy testing of
colistin, susceptibility to antimicrobial agents in use at local hospitals, polymerase chain reaction
and sequencing for analysis of the resistant genes related to carbapenem, colistin and amikacin.
Phenotypic, genotypic, and clinical characterisation were utilised to develop a standardised
management approach of significant Acinetobacter spp. infection.
Results: Acinetobacter spp. was identified as a significant cause of sepsis and mortality among
patients in a surgical intensive care unit (ICU). Cases of multidrug-resistant (MDR) and
extensively drug-resistant (XDR) Acinetobacter spp. increased over seven years, together with
the emergence of pandrug-resistant (PDR) isolates. The results of synergy testing of colistin
combinations with amikacin, carbapemens (imipemen, meropenem), ciprofloxacin, tazocin,
linezolid, rifampicin and vancomycin against Acinetobacter spp. was highly diverse and speciesdependent.
Characterisation of Acinetobacter spp. isolates showed that oxacillinase β-lactamase
(OXA-23)-producing MDR isolates correlated with their antibiogram. Pulsed field gel
electrophoresis (PFGE) showed horizontal transfer between seven clusters, each containing two
patients each, totalling 14 patients. However, the PFGE typing revealed a diverse collection of
MDR Acinetobacter spp. clones, and that isolates from not more than two patients were related.
This suggests, therefore, that no outbreak had occurred based on the PFGE typing interpretation.
Further genetic investigation revealed that the aphA6 gene were associated with amikacin
resistance and IpxA gene may be associated with colistin resistance in our local setting.
Conclusion: The results highlighted the importance of antibiotic stewardship in the treatment
of Acinetobacter spp. infection. Individual-specific antibiograms are recommended as the best
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approach for treatment in KwaZulu-Natal (KZN) and synergy testing should be performed for
individualised direct therapy. The clinical and microbiological indicators of significant infection
are crucial when establishing the decision to treat. The study provided a valuable standardised
approach, including a flow chart of criteria for sepsis and colonisation; a standardised algorithm
for the management; and synergy test at academic complex hospitals, Medical Microbiology
laboratory, National Health Laboratory Service (NHLS) in KZN.
Description
Doctoral Degree. University of KwaZulu-Natal, Durban.