High-level persistence of biofilm formation in in methicillin resistant Staphylococcus aureus

Aims@#Biofilm formation by Methicillin-resistant Staphylococcus aureus on a variety of surfaces and detection of the biofilm-forming population by the most reliable method is very much essential to diagnose the nosocomial infection caused by S. aureus. @*Methodology and results@#This study is aimed to evaluate the biofilm producing ability of S. aureus by qualitative Congo red agar (CRA), and quantitative microtitre plate (MTP) methods. The morphological difference of biofilms analysis was done by SEM (Scanning Electron Microscope) and genotyping analysis of mecA and femA for determination of MRSA among isolated S. aureus strains and to check the biofilm producers among MRSA strains. Biofilm production was found to be at different intensities by MTP. The strong, moderate and weak biofilm producers were found to be 38.63%, 31.81%, and 29.54% respectively. The strong adherent biofilm formed by representative isolate developed a dense biofilm with thick mucus three-dimensional multilayered structure of macroscopic dimension. Conversely, SEM analysis of moderate and weak biofilm representative strain failed to form a monolayer of scattered single cells to three-dimensional structure. The 47.72% of S. aureus isolates have shown positive for the genotypic analysis of mecA and femA. The strong and moderate biofilm forming MRSA was found to be 38.63% and 9.09%, respectively. @*Conclusion, significance and impact of study@#The great challenge is associated with biofilm mediated infection caused S. aureus healthy and hospitalized individual hence the present study reinforces the need of precautionary measures to avoid the indiscriminate use of antibiotics in case of biofilm-forming MRSA.

Widespread Emergence of Multidrug Resistant Pseudomonas aeruginosa Isolated from CSF Samples.

Bacterial infections of the central nervous system, especially acute infections such as bacterial meningitis require immediate, invariably empiric antibiotic therapy due to the widespread emergence of resistance among bacterial species. Nosocomial infections by Pseudomonas aeruginosa have been described with an increasing trend towards multidrug resistance. P. aeruginosa isolates n = 53 (66%) isolated from the cerebrospinal fluid (CSF) were used for this study. Antibiotic resistance in 53 P. aeruginosa clinical isolates from 80 CSF samples were evaluated. Of these, n = 42 (80%) of the isolates showed multidrug resistance to more than eight antibiotics and n = 17 (32%) isolates were found to be imipenem resistant P. aeruginosa (IMPR-Pa). Genotypical examination by ERIC based PCR revealed minor genetic variations. Polymicrobial infections are common in the CSF samples. However, high prevalence of P. aeruginosa as an opportunistic pathogen has been developing with increased resistance to antimicrobial agents and thus becoming a significant threat.

Bacteriophage therapy for Staphylococcus aureus bacteremia in streptozotocin-induced diabetic mice.

The protective effect of bacteriophage was assessed against experimental Staphylococcus aureus lethal bacteremia in streptozotocin (STZ) induced-diabetic and non-diabetic mice. Intraperitoneal administrations of S. aureus (RCS21) of 2 × 108 CFU caused lethal bacteremia in both diabetic and non-diabetic mice. A single administration of a newly isolated lytic phage strain (GRCS) significantly protected diabetic and non-diabetic mice from lethal bacteremia (survival rate 90% and 100% for diabetic and non-diabetic bacteremic groups versus 0% for saline-treated groups). Comparison of phage therapy to oxacillin treatment showed a significant decrease in RCS21 of 5 and 3 log units in diabetic and non-diabetic bacteremic mice, respectively. The same protection efficiency of phage GRCS was attained even when the treatment was delayed up to 4 h in both diabetic and non-diabetic bacteremic mice. Inoculation of mice with a high dose (10¹° PFU) of phage GRCS alone produced no adverse effects attributable to the phage per se. These results suggest that phages could constitute valuable prophylaxis against S. aureus infections, especially in immunocompromised patients.

Aminoglycoside-resistance mechanisms in multidrug-resistant Staphylococcus aureus clinical isolates.

Aminoglycoside resistance in six clinically isolated Staphylococcus aureus was evaluated. Genotypical examination revealed that three isolates (HLGR-10, HLGR-12, and MSSA-21) have aminoglycoside-modifying enzyme (AME) coding genes and another three (GRSA-2, GRSA-4, and GRSA-6) lacked these genes in their genome. Whereas isolates HLGR-10 and HLGR-14 possessed bifunctional AME coding gene aac(6')-aph(2''), and aph(3')-III and showed high-level resistance to gentamycin and streptomycin, MSSA-21 possessed aph(3')-III and exhibited low resistance to gentamycin, streptomycin, and kanamycin. The remaining three isolates (GRSA-2, GRSA-4, and GRSA-6) exhibited low resistance to all the aminoglycosides because they lack aminoglycoside-modifying enzyme coding genes in their genome. The transmission electron microscopy of the three isolates revealed changes in cell size, shape, and septa formation, supporting the view that the phenomenon of adaptive resistance is operative in these isolates.