The influence of agitation on oil substrate dispersion and oxygen transfer in Pseudomonas aeruginosa USM-AR2 fermentation producing rhamnolipid in a stirred tank bioreactor.

Water-immiscible substrate, diesel, was supplied as the main substrate in the fermentation of Pseudomonas aeruginosa USM-AR2 producing rhamnolipid biosurfactant, in a stirred tank bioreactor. In addition to the typical gas-aqueous system, this system includes gas-hydrocarbon-aqueous phases and the presence of surfactant (rhamnolipid) in the fermentation broth. The effect of diesel dispersion on volumetric oxygen transfer coefficient, k L a, and thus oxygen transfer, was evaluated at different agitations of 400, 500 and 600 rpm. The oxygen transfer in this oil-water-surfactant system was shown to be affected by different oil dispersion at those agitation rates. The highest diesel dispersion was obtained at 500 rpm or impeller tip speed of 1.31 m/s, compared to 400 and 600 rpm, which led to the highest k L a, growth and rhamnolipid production by P. aeruginosa USM-AR2. This showed the highest substrate mixing and homogenization at this agitation speed that led to the efficient substrate utilization by the cells. The oxygen uptake rate of P. aeruginosa USM-AR2 was 5.55 mmol/L/h, which showed that even the lowest k L a (48.21 h-1) and hence OTR (57.71 mmol/L/h) obtained at 400 rpm was sufficient to fulfill the oxygen demand of the cells. The effect of rhamnolipid concentration on k L a showed that k L a increased as rhamnolipid concentration increased to 0.6 g/L before reaching a plateau. This trend was similar for all agitation rates of 400, 500 and 600 rpm, which might be due to the increase in the resistance to oxygen transfer (k L decrease) and the increase in the specific interfacial area (a).

Pericardial cyst: a rare cause of pericardial effusion.

Pericardial cysts occur rarely, with an incidence rate of 1 per 100,000. They are usually detected by chance and clinically silent in most cases. Pericardial cysts are the most common benign tumours of the pericardium and presents by the third or fourth decade of life, and equally common in males and females. In principle, they only require follow-up, however, an enlarging or symptomatic cyst requires surgical removal. We report a case of a 32 year-old Malay lady, who presented with history of recurrent pericardial effusion followed by right pleural effusion. Computed tomography (CT) thorax identified a large mediastinal cyst as the cause of her problem, requiring exploratory thoracotomy.

Role of topical antibiotic prophylaxis in prevention of bacterial translocation into upper trachea in nasally intubated patients undergoing tonsillectomies.

INTRODUCTION: The human oropharynx and nasopharynx are home of different bacteria and fungi. The initial sterile endotracheal tube (ETT) transfers mechanically the bacteria from the nasopharynx and oropharynx to the sterile tracheobronchial tree. We investigated the efficacy of Neomycin-Bacitracin combination spray in the prevention of this bacterial translocation through its application over and inside the lumen of the endotracheal tubes preoperatively. PATIENTS AND METHODS: Ninety patients aged (from 8 to 15 years) with ASA I and II were randomly assigned into 2 groups (45 patients for each): Group I; patients with naso-tracheal intubation which sprayed by placebo spray (Lidocaine) and group II; with naso-tracheal intubation that sprayed with antibiotic spray (combined Neomycin sulphate and Bacitracin) on the outside wall of the tube and inside its lumen. At the end of surgery and immediately after extubation, swabs were taken from the upper trachea using cotton tipped swab for bacterial growth. Inflammatory biomarkers were assessed preoperatively and postoperatively to detect any laboratory differences between both groups. RESULTS: In the control group, all patients had heavy bacterial contamination and they were at either level 3 or 4 colony forming units. Thirty-two patients (71%) were at level 3 while 13 patients (29%) were at level 4. In the study group, there were 28 (62.2%) patients showed no bacterial growth, 15 (33.3%) patients were level 1, and 2 patients (4.4%) at level 2 colony forming units. There were no clinical differences between the 2 groups. Also, there was no significant difference between the 2 groups regarding to their postoperative body temperature although the inflammatory biomarkers were significantly higher in the control group. CONCLUSION: Bacterial translocation by endotracheal intubation to the tracheobronchial tree could be prevented by local antibiotic spray application to outer and inner walls of the endotracheal tubes.

Pericardial cyst: a rare cause of pericardial effusion

Pericardial cysts occur rarely, with an incidence rate of 1 per 100,000. They are usually detected by chance and clinically silent in most cases. Pericardial cysts are the most common benign tumours of the pericardium and presents by the third or fourth decade of life, and equally common in males and females. In principle, they only require follow-up, however, an enlarging or symptomatic cyst requires surgical removal. We report a case of a 32 year-old Malay lady, who presented with history of recurrent pericardial effusion followed by right pleural effusion. Computed tomography (CT) thorax identified a large mediastinal cyst as the cause of her problem, requiring exploratory thoracotomy.