ABSTRACT
Objectives: This study aimed to detect heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) among methicillin-resistant S. aureus (MRSA) isolated from healthcare-associated infections and identify staphylococcal cassette chromosome mec (SCCmec) types. Methods: This study was conducted from February 2019 to March 2020 and included patients admitted in 4 tertiary care hospitals in Karnataka, India. Isolation and identification of MRSA were done using standard bacteriological methods. Antimicrobial susceptibility testing was done using Kirby-Bauer disc diffusion; macrolide-lincosamide-streptogramin B phenotypes were identified using the D test. The minimum inhibitory concentration (MIC) of vancomycin was determined using agar dilution. hVISA were confirmed by the modified population analysis profile-area under the curve test. SCCmec types and the Panton-Valentine leukocidin (pvl) gene were detected using multiplex polymerase chain reaction. Results: Of 220 MRSA stains, 14 (6.4%) were hVISA. None of the MRSA isolates was vancomycin-intermediate or -resistant and all hVISA were susceptible to linezolid and teicoplanin. The macrolide-streptogramin B phenotype was present in 42.9% of hVISA; 92.9% of the hVISA strains had vancomycin MIC in the range of 1-2 µg/mL. Majority of the hVISA and vancomycin-susceptible MRSA were isolated from patients with skin and soft tissue infections. SCCmec III and IV were present in 50% and 35.7% of hVISA, respectively; 14.3% of the hVISA harboured SCCmec V. Conclusion: The prevalence rate of hVISA among MRSA was 6.4%. Therefore, MRSA strains should be tested for hVISA before starting vancomycin treatment. None of the isolates was vancomycin-intermediate or -resistant and all the hVISA strains were susceptible to linezolid and teicoplanin. The majority of the hVISA were isolated from patients with skin and soft tissue infections and harboured SCCmec III and IV.
Subject(s)
Methicillin-Resistant Staphylococcus aureus , Soft Tissue Infections , Staphylococcal Infections , Humans , Vancomycin/pharmacology , Vancomycin/therapeutic use , Linezolid/pharmacology , Linezolid/therapeutic use , Staphylococcus aureus/genetics , Vancomycin-Resistant Staphylococcus aureus , Methicillin-Resistant Staphylococcus aureus/genetics , Teicoplanin/therapeutic use , Staphylococcal Infections/drug therapy , Staphylococcal Infections/epidemiology , Soft Tissue Infections/drug therapy , Tertiary Care Centers , Streptogramin B/therapeutic use , India/epidemiology , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/therapeutic use , Macrolides/therapeutic useABSTRACT
The prevalence of OXA-type carbapenemase genes, ISAba1 insertion sequence, carbapenem resistance, biofilm forming ability and genetic heterogeneity in clinical isolates of Acinetobacter spp. from hospitals in Mangalore, South India was studied. Based on the presence of the bla(OXA-51) -like gene, the 62 isolates of Acinetobacter spp. were identified as 48 A. baumannii and 14 other Acinetobacter spp. The prevalence of bla(OXA-23) -like, bla(OXA-24) -like and bla(OXA-58) -like genes in A. baumannii was 47.9%, 22.9% and 4.2%, while in other Acinetobacter spp. it was 28.5%, 64.3% and 35.7% respectively. Several A. baumannii isolates (16/48) harbored the insertion sequence ISAba1 in the upstream region of the bla(OXA-23) -like gene. Resistance to meropenem was seen in 39.6% and 14.2% of A. baumannii and other Acinetobacter spp. isolates, respectively. The ability to form biofilm was observed to be higher among A. baumannii in comparison to other Acinetobacter spp. The present study shows that bla(OXA-23) -like genes are more common in A. baumannii,whereas bla(OXA-24) -like genes are common to other Acinetobacter spp. The study revealed genetic heterogeneity among the isolates, indicating multiple sources in the hospitals.
