(20). Disc diffusion, as per CLSI guidelines (14), and MIC, by the macrodilution method, were assessed. The isolates were also subjected to MIC testing for meropenem using the broth macrodilution technique. The organism was considered sensitive if the MIC was < 4 μg/mL and resistant if it was selleck inhibitor > 16 μg/mL according to
CLSI guidelines. The choice of meropenem was based on information from the clinicians in Mangalore that meropenem is the drug of choice in multidrug resistant Acinetobacter infections, rather than imipenem and ertapenem. Four CRA primers (21, Table 1) were initially tested for their specificity in RAPD-PCR. Of these, the primer CRA 22 was found to be most suitable as it generated polymorphic bands and the results obtained were reproducible. The banding patterns were compared using Gelcompar II software version 2.5 (Applied Maths, Sint-Martens-Latem, Belgium). The levels of similarities between different profiles were calculated using the Pearson coefficient correlation and clustered by the UPGMA algorithm. In this study, identification of A. baumannii was based both on
the basis of phenotypic tests and the on the presence of blaOXA-51 gene, which has been reported to be intrinsic to this species. Out of 62 Acinetobacter isolates included in this study, 48 were identified as A. baumannii and 14 as other Acinetobacter spp. (Table click here 2). Of the 48 A. baumannii, 15 were from the respiratory tract, 15 from skin and soft tissues, 11 from blood, 5 from urine and Phloretin 2 from other sources. Among the other Acinetobacter spp., the majority of the isolates (9/14) were from blood (Table 2). Multiplex PCR-based analysis of the isolates for the four major classes of carbapenemase genes (Fig. 1) revealed the presence of blaOXA-23-like genes in 27 isolates, of which 23 were A. baumannii and 4 comprised other Acinetobacter spp. (Table 2). Of the 20 isolates that were positive for blaOXA-24-like genes, 11 were A. baumannii
and 9 were other Acinetobacter spp. Only seven isolates had blaOXA-58-like genes, among these two were A. baumannii and five were other Acinetobacter spp. The prevalence of blaOXA-23-like genes in A. baumannii was 47.9% while in other Acinetobacter spp. it was 28.5%. On the other hand the prevalence of blaOXA-24-like genes in A. baumannii was only 22.9% and in other Acinetobacter spp. it was as high as 64.3%. A low prevalence of blaOXA-58-like genes (4.2%) was seen in A. baumannii, whereas for other Acinetobacter spp. it was 35.7%. Polymerase chain reaction for the presence of the insertional sequence ISAba1 using specific primers (Table 1) showed 33.3% (16/48) of A. baumannii isolates harbored this gene. None of the other Acinetobacter spp. were positive for this gene. The presence of ISAba1 in A. baumannii was detected only in the upstream region of blaOXA-23-like gene (Fig.