Molecular characterisation of Klebsiella oxytoca strains isolated from patients with antibiotic-associated diarrhoea.

BACKGROUND AND STUDY AIM: Colitis is a common complication after treatment with antibiotics such as ß-lactams, quinolones, and aminoglycosides. Recently, Klebsiella oxytoca has been implicated in this type of diarrhoea. The prevalence and characterisations of K. oxytoca isolated from patients with antibiotic-associated diarrhoea were investigated. The K. oxytoca isolates were also tested for cytotoxin production. PATIENTS AND METHODS: This study was conducted from May 2011 to Dec 2013. Faecal samples were collected from hospitalised patients receiving antibiotic treatment. Initial cultivation was performed on specific media. The clinical isolates were confirmed by polymerase chain reaction (PCR) using the specific K. oxytoca polygalacturonase (pehX) gene. The double-disc diffusion test was used to detect extended-spectrum beta-lactamase (ESBL)-producing strains. Tracking of ESBL-encoding genes was performed via PCR. The organism was cultured on Hep-2 cell lines for cytotoxin production. RESULTS: Out of 331 samples collected from patients, 40 were confirmed molecularly to be clinical isolates of K. oxytoca. Fourteen (35%) ESBL-producing strains were isolated using the double-disc diffusion method. Among the molecularly confirmed K. oxytoca isolates, seven (17.5%) tested positive for the blaSHV gene, 12 (30%) for blaTEM, 10 (25%) for blaCTX-M, three (7.5%) for blaOXA, nine (22.5%) for blaCTX-M-15, and seven (17.5%) for blaTEM-1. Five (12%) isolates showed cytotoxin activity below 30%, 12 (30%) strains showed moderate cytotoxin activity between 30% and 60%, and 23 (58%) strains showed cytotoxin activity ⩾60%. CONCLUSIONS: The cytotoxin-producing K. oxytoca is found to be one of the causes of antibiotic-induced colitis. Discontinuing treatment and allowing normal intestinal flora to be established or prescribing appropriate medication after antibiogram can help patients with antibiotic-induced haemorrhagic colitis in a timely manner.

Irreversible changes in protein conformation due to interaction with superparamagnetic iron oxide nanoparticles.

The understanding of the interactions between nanomaterials and proteins is of extreme importance in medicine. In a biological fluid, proteins can adsorb and associate with nanoparticles, which can have significant impact on the biological behavior of the proteins and the nanoparticles. We report here on the interactions of iron saturated human transferrin protein with both bare and polyvinyl alcohol coated superparamagnetic iron oxide nanoparticles (SPIONs). The exposure of human transferrin to SPIONs results in the release of iron, which changes the main function of the protein, which is the transport of iron among cells. After removal of the magnetic nanoparticles, the original protein conformation is not recovered, indicating irreversible changes in transferrin conformation: from a compact to an open structure.