Title : Incidences of hVISA in North India; Screening, Mechanism of Resistance and Possible Treatment
Abstract:
Heterogeneous vancomycin intermediate Staphylococcus aureus (hVISA) strains are increasingly reported and their association with vancomycin treatment failure is a well-known problem worldwide. Methicillin resistant S. aureus (MRSA)(n=500) were screened for hVISA by four different methods. Transmission electron microscopy (TEM) were performed to see the cell wall thickness of hVISA. Survivability study was performed on dry cotton swab, and fitness cost was evaluated by estimating growth kinetics and generation time constant in BACTEC automated system. Molecular features were evaluated by Polymerase chain reaction (PCR). Genetic relatedness was studied by pulsed-field gel electrophoresis (PFGE). Antibiofilm activity and possible mechanism of action of Cu 2 O-NPs (Cuprous oxide nanoparticles) were evaluated against hVISA isolates. hVISA strains detected by four different methods- BHIV4/ gradient plate/ macro E-test (MET)/ and GRD E test were as follows: 11.6/ 10/ 9 and 9.5% in 2011-12, 12.1/ 9.7/ 8.9 and10.5% in 2012-13), 13.9/ 11.7/ 11.1 and 12.8% in 2013-14 respectively. PAP-AUC analysis confirmed hVISA in 4.5% (9/198), 6.5% (8/123) and 6.7% (12/179) in respective years; 24% (7/29) of hVISA isolates were non-susceptible to daptomycin. MET had the highest positive predictive value (59.1%) compared to other screening methods (range, 46.2% to 54.7%). Overall 2% (10/500) strains were identified as VISA. TEM showed significant increase in cell wall thickness of hVISA isolates (p < 0 .001) with distinct reduction in their biofilm formation ability. Total mean maximum time of recovery on primary culture was 4.1 and 7.1weeks (P = 0.0001)for hVISA and vancomycin sensitive S. aureus (VSSA), respectively, in dry starved condition. No significant difference between the mean value of lag phase duration (P = 0.89) was noted between hVISA and VSSA isolate in growth kinetics. However, we observed lesser generation time of hVISA isolates compared to S. aureus ATCC 29213 (P = 0.0076). Molecular studies showed distribution of SCCmec types in hVISA was as follows: 13/29 (44.8%) each of types II and V,1/29 (3.4%) type III and 2/29 (6.9%) type IVa. Among VS-MRSA isolates, 20/50 (40.0%) were SCCmec type II,17/50 (34.0%) were type III, 3/50(6.0%) were type IVa and 10/50 (20.0%) were type V. SCCmec type V was significantly associated with hVISA, whereas SCCmec type III showed an association with VS-MRSA (P = 0.020 and P = 0.001, respectively). The PVL gene was detected in 9/29 hVISA (31.0%) and 13/50 VS-MRSA (26.0%). By PFGE analyses, both hVISA and VS-MRSA strains were found to be clonally unrelated. In hVISA isolates, 24/29 (82.8%) were agr type I, 3/29 (10.3%) were type III and 2/29 (6.9%) were non-typeable. However, in VS-MRSA isolates, 25/50 (50.0%) were type II, 15/50 (30.0%) were type I, 7/50 (14.0%) were type III and 3/50(6.0%) were non-typeable. Through result increased trend of hVISA was observed over the study period. Daptomycin non-susceptibility among hVISA strains is an emerging clinical concern. Since PAP-AUC is a cumbersome technique, each clinical laboratory should use at least one screening method for presumptive identification of hVISA strains. These observation suggests that hVISA have fitness cost compared to VSSA. However, further studies with more cases are required. The study shows that healthcare-associated MRSA strains may harbour community-acquired MRSA genetic markers. The changing molecular epidemiology and role of agr I in reduced vancomycin susceptibility in hVISA requires further investigation. The results of Cu2O-NPs study suggest that Cu2O-NPs exert their action by disruption of the bacterial cell membrane and can be used as effective antistaphylococcal and antibiofilm agents in diverse medical devices.
Audience take away:
- Explain how the audience will be able to use what they learn?
Reply: Audience will learn how reduced susceptible vancomycin resistant isolates are going to become increasing threat for mankind and going to increase treatment cost. They will learn screening methods for hVISA detection in laboratory settings - How will this help the audience in their job?
Reply: They will learn a new technique in bacteriology and able to screen hVISA. This will increase addition technique in bacteriology laboratory. - Is this research that other faculty could use to expand their research or teaching?
Reply: Yes - Does this provide a practical solution to a problem that could simplify or make a designer’s job more efficient?
Reply: Not sure - Will it improve the accuracy of a design, or provide new information to assist in a design problem?Reply: Yes
- List all other benefits.
Reply: They will also learn possible treatment options for such type of bugs.
