Mechanism of persistent infection associated with peritoneal implants.

The ability of rabbits to clear an intraperitoneal injection of Pseudomonas aeruginosa in the presence or absence of a surgically implanted peritoneal device was investigated. Sham-operated rabbits without an implant eliminated a P. aeruginosa challenge of 5 x 10(6) cfu/ml; lavage fluid and peritoneal tissues became culture-negative within 96 h. However, peritonitis developed in rabbits that were given the same number of bacteria in the presence of an implant; high bacterial counts were recovered from the lavage fluid and the device itself. Scanning and transmission electronmicroscopy revealed bacterial biofilms on the surface of the device. Insertion of pre-colonised devices demonstrated a rapid multiplication of sessile organisms within the resulting bacterial biofilm. Counts reached a plateau of about 1 x 10(7) cfu/cm2 of Silastic by day 16 and fluctuated around this level until the end of the study. Pre-immunisation with formalin-killed whole cells of P. aeruginosa did not reduce this bacterial growth despite high levels of specific IgG. The results confirm the failure of peritoneal defences to clear an infection in the presence of an implant following either challenge with planktonic bacteria or insertion of a pre-colonised device, and demonstrate the rapid development of bacterial biofilms on the surface of the implant which appear to protect the bacteria from host defences, even when primed by pre-immunisation.     

Rat model of experimental bacterial prostatitis

A reproducible rat model of chronic bacterial prostatitis was developed employing a defined bacterial pathogen to study the pathophysiology of acute and chronic bacterial prostatitis. The progression of inflammation and its consequences following the retrograde introduction of bacteria through the acute and finally the chronic stages of prostatitis can be documented with microbiological, histological, ultrastructural and immunologic data. This model has many striking similarities to the natural history of human chronic bacterial prostatitis and further microbiological, antimicrobial and immune modulation or manipulation of this model should help us to further delineate the pathogenic mechanisms involved in this chronic infective disease.Zum Studium der Pathophysiologie der akuten und chronischen bakteriellen Prostatitis wurde ein reproduzierbares Rattenmodell für die chronische bakterielle Prostatitis entwickelt, dabei wird ein definierter bakterieller Erreger verwendet. Das Fortschreiten der Entzündung und ihrer Folgeerscheinungen nach retrogradem Einführen der Bakterien über die akuten und schließlich die chronischen Stadien der Prostatitis kann mit mikrobiologischen, histologischen, ultrastrukturellen und immunologischen Daten dokumentiert werden. Dieses Modell hat bemerkenswerte Ähnlichkeiten mit dem natürlichen Verlauf der chronischen bakteriellen Prostatitis beim Menschen; weitere mikrobiologische, antimikrobielle und immunmodulierende oder anderweitige Veränderungen dieses Modells dürften dazu beitragen, daß die Pathomechanismen dieser chronischen Infektionskrankheit weiter abgeklärt werden können.     

Short-Ti inversion-recovery pulse sequence: analysis and initial experience in cancer imaging

Inversion recovery (IR), commonly considered a pulse sequence capable of producing T1-weighted images with excellent display of normal anatomy, is versatile: The null point and peak time provide a useful, succinct summary of the properties of IR and its capacity for producing both T1- and T2-weighted images. Shortening of the inversion time (TI) and creation of a short-TI inversion-recovery (STIR) pulse sequence increases sensitivity to malignancy and other abnormalities by making the effects of prolonged T1 and T2 on signal intensity additive and by nulling the signal from fat. The authors examined over 300 patients with various malignancies and compared STIR images with T1- and T2-weighted images obtained at 0.5 T. In 43 cases, signal-difference-to-noise ratios (SD/Ns) were calculated between tumor, fat, and muscle. In general, STIR images demonstrated tumor as a conspicuously high-intensity area in a background of muted, discernible anatomic detail. The good contrast achieved with STIR sequences between tumor and fat (SD/N = 18.1) and tumor and muscle (SD/N = 12.9) consolidated into a single image the information contained separately on T1- and T2-weighted images, which facilitates efficient detection and localization of malignancy.     

Solitary rectal ulcer syndrome: findings at barium enema study and defecography

Sixteen cases of histopathologically proved solitary rectal ulcer syndrome were encountered. Fifteen patients underwent barium enema study; in nine cases the findings--including rectal stricture, granularity of the mucosa, and thickened rectal folds-were nonspecific. In six cases the study was normal. All patients had a long history of defecation disorders, and defecography was performed in all. In seven cases, intussusception of the rectal wall was seen; in another case the intussusception was accompanied by a rectocele. One case showed rectal prolapse. In four cases, failed relaxation of the puborectalis occurred and prevented the passage of the bolus; in another case there was abnormal perineal descent. In two patients studies were normal. In patients with defecation disorders, the possibility of this syndrome should be considered. Defecography is the method of choice for establishing the diagnosis.