Identification and Differentiation of Acinetobacter calcoaceticus-Acinetobacter baumannii Complex by Multiplex PCR: Common Nosocomial Pathogens Among Children

Abstract

Acinetobacter baumannii is one of the most common pathogens causing nosocomial infections worldwide involving a range of infections such as surgical site infections, pneumonia, urinary tract infections and others. They are also an important pathogen to study due to multidrug resistant worldwide, for which identification is very crucial for effective treatment. Acinetobacter is a complex genus which contains multiple species, most of which have similar morphological characteristics and biochemical properties leading to a complicated analysis process in a regular routine care. This study was based on clinical isolates where Acinetobacter baumannii and other closely related species of Acinetobacter, commonly called Acinetobacter calcoaceticus- Acinetobacter baumannii (ACB) complex, were confirmed by conventional multiplex PCR using primers targeting the ITS region followed by confirmation of Acinetobacter baumannii only by RT-PCR using “blaOXA-51-LIKE” primers, which helped us to validate the different kinds of primers as well as help us to compare the identification results between these multiple methods. At the same time, the antibiotic susceptibility test (AST) results from the routine labs were analyzed using these isolates to understand their resistance pattern. The results indicated that PCR methods were able to confirm Acinetobacter baumannii more accurately compared to conventional biochemical methods, and that both the primers can be used simultaneously without hesitation. We also found the presence of other Acinetobacter species from the ACB complex which was not possible to identify by conventional biochemical methods. On the other hand, Burkholderia cepacia was found among these isolates indicating that, these isolates showed a conflicting biochemical results with Acinetobacter species that might lead to misidentification. From the AST results, we found out that Acinetobacter baumannii isolates showed high resistance pattern in almost all of the available antibiotics. To conclude, conventional multiplex PCR method was a much better option for identification due to low cost expenses which can be performed in a regular diagnostic routine lab practices.