Microbiology of Postoperative Infections

Biohybrid nanostructured iron oxide nanoparticles and Satureja hortensis to prevent fungal biofilm development

Cutaneous wounds are often superinfected during the healing process and this leads to prolonged convalescence and discomfort. Usage of suitable wound dressings is very important for an appropriate wound care leading to a correct healing. The aim of this study was to demonstrate the influence of a nano-coated wound dressing (WD) on Candida albicans colonization rate and biofilm formation. The modified WD was achieved by submerging the dressing pieces into a nanofluid composed of functionalized magnetite nanoparticles and Satureja hortensis (SO) essential oil (EO). Chemical composition of the EO was established by GC-MS. The fabricated nanostructure was characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Differential Thermal Analysis (DTA) and Fourier Transform-Infrared Spectroscopy (FT-IR). The analysis of the colonized surfaces using (Scanning Electron Microscopy) SEM revealed that C. albicans adherence and subsequent biofilm development are strongly inhibited on the surface of wound dressing fibers coated with the obtained nanofluid, comparing with regular uncoated materials. The results were also confirmed by the assay of the viable fungal cells embedded in the biofilm. Our data demonstrate that the obtained phytonanocoating improve the resistance of wound dressing surface to C. albicans colonization, which is often an etiological cause of local infections, impairing the appropriate wound healing.

Epidemiology and antimicrobial sensitivities of 536 multi-drug-resistant gram-negative bacilli isolated from patients treated on surgical wards

BACKGROUND

In this era of increasing antimicrobial resistance, infections caused by multi-drug-resistant (MDR) gram-negative bacilli (GNB) are becoming more common and pose a challenge to all clinicians, including surgeons.

METHODS

We evaluated the epidemiology and antimicrobial sensitivities of GNB isolated from patients treated on surgical wards at the University Hospital of Heraklion, Crete, Greece, from 2004 to 2009. The MDR isolates were defined according to an international expert proposal supported by the U.S. Centers for Disease Control and Prevention and the European Centre for Disease Prevention and Control.

RESULTS

A total of 1,153 GNB were isolated; 536 (46.5%) were MDR. The most common isolates were Escherichia coli (312 [27.8%]; MDR rate 50.2%), Pseudomonas aeruginosa (298 [25.8%]; MDR rate 39.6%), Acinetobacter baumannii (137 [11.9%]; MDR rate 83.9%), and Klebsiella pneumoniae (112 [9.7%]; MDR rate 44.6%). Most pathogens were isolated from patients hospitalized in the Departments of Surgical Oncology (32.3%), Orthopedic and Trauma Surgery (31.8%), General Surgery (18.1%), and Pediatric Surgery (15.5%). The clinical specimens comprised pus (45.1%), normally sterile fluids (22.5%), urine (16.8%), blood (6.3%), and other body fluids. Most effective in vitro against all MDR pathogens were colistin (83%), meropenem (57%), and imipenem-cilastatin (56%). The MDR P. aeruginosa was susceptible most often to colistin (94%) and aminoglycosides (tobramycin 56%, amikacin 55%), MDR A. baumannii only to colistin (94%), and MDR K. pneumoniae to meropenem (92%) and aminoglycosides (amikacin 76%, gentamicin 74%).

CONCLUSION

In a region with a high prevalence of antibiotic resistance, almost one-half of GNB isolated from surgical patients were MDR. Surgeons may consider these developments to guide empiric antibiotic therapy for infections caused by gram-negative pathogens.

The use of carbapenems in the treatment of serious infections

Inadequate initial antimicrobial treatment in serious infections leads to increased mortality. Achieving adequate treatment is increasingly difficult because of the increasing prevalence of multidrug-resistant (MDR) pathogens. The carbapenems are potent, broad-spectrum antibiotics that have been shown to be safe and efficacious therapies in the treatment of serious infections. This review is intended to compare the 4 major members of the carbapenem class, which include imipenem, meropenem, ertapenem, and doripenem, with other widely used antimicrobial agents in the intensive care unit (ICU). The carbapenems are potent, broad-spectrum antibiotics that have been shown to be safe and efficacious therapies in the treatment of serious infections. They provide better gram-negative coverage than other beta-lactams and are stable against extended-spectrum beta-lactamases and AmpC beta-lactamases, making them effective in the treatment of many MDR bacteria. The newly approved carbapenem, doripenem, may help preserve the utility of the carbapenem class.