Feasibility of disinfection kinetics and minimum inhibitory concentration determination on bacterial cultures using flow cytometry.

Disinfection kinetics has been well established for selected antimicrobial agents on isolated bacterial strains. Due to the difficulties of culturing most bacteria, the majority of these studies have been limited to readily cultivable microorganisms of a single type or family. This study explores the feasibility of using flow cytometry for characterising the disinfection kinetics and minimum inhibitory concentration (MIC) of an Escherichia coli culture and a microbial consortium. The proposed method relies on fluorescent dye molecules to indicate the morphological and physiological status of numerous individual cells. Biocides of varying effectiveness and inactivation mechanisms (chlorine, iodine, and silver) were used to evaluate this novel application. Using pseudo-first-order kinetics, the coefficients of specific lethality of chlorine and iodine on Escherichia coli were 4.71 and 3.78 x 10(-3) L mg(-1) min(-1) and MIC of silver ion was between 60 and 80 microg L(-1). The coefficients of specific lethality of chlorine and iodine on the microbial consortium were 4.96 and 8.89 x 10(-3) L mg(-1) min(-1) and MIC of silver ion was between 40 and 60 microg L(-1). This method can be used to provide a rapid and consistent way of determining disinfection kinetics and MICs for pure and mixed bacterial cultures and can potentially be used to examine water and wastewater disinfection efficiency. However, caution should be used to ensure that the physiological and morphological status characterised by cytodyes is a result of the inactivation mechanisms of the disinfectants evaluated.

Structure and function in tracheal stenosis.

The mechanism of airflow obstruction was investigated in 21 patients with tracheal stenosis using tantalung tracheograms and pulmonary function studies, including flow-volume (FV) loops. In 4 patients with severe obstructive pulmonary disease, FV loops failed to demonstrate radiographically visible tracheal stenosis. In 17 patients, both FV loops and tracheograms demonstrated central airway obstruction. In three of the 17 patients, the stenotic segment was a rigid lesion at the thoracic outlet with similar limitation of inspiratory and expiratory flow. In nine of the 17 patients, the lesion was extrathoracic (rigid in 6 patients and pliable in 3). The 3 pliable extrathoracic lesions produced marked limitation of inspiratory flow but normal expiratory flow. Three rigid extrathoracic lesions produced inspiratory flow that was more limited than expiratory flow, suggesting dynamic inspiratory compression of the normal extrathoracic trachea. The one rigid intrathoracic lesion caused expiratory flow limitation greater than inspiratory flow limitation, suggesting dynamic compression of the intrathoracic trachea on expiration. The position of the obstructing lesion and dynamic compression of the normal, compliant trachea may be the major determinants of the difference in flow limitation between expiration and inspiration in some patients.

Interstitial pulmonary edema.

Florid pulmonary edema is frequently preceded by interstitial edema formation. Because of alterations in the balance of oncotic and hydrostatic pressures between the capillary and lung interstitium or changes in capillary permeability, edema fluid forms in the interstitial spaces of the lung. Once the capacitance of the pulmonary lymphatics is exceeded, interstitial and alveolar edemas become more prominent. Bronchoconstriction and increased vascular resistance lead to ventilation-perfusion imbalance, reduced lung compliance, and increasing symptoms. Early detection is possible by noting characteristic changes in gas exchange and chest radiograph. Awareness and early recognition of these changes, together with the predisposing clinical settings, can lead to the institution of appropriate therapy before patients become severely ill with frank alveolar pulmonary edema.

Trephine air drill, bronchial brush, and fiberoptic transbronchial lung biopsies in immunosuppressed patients.

Seventy-nine nonthoracotomy lung and bronchial biopsy procedures were performed in 52 immunosuppressed patients: 22 renal transplants, 24 lymphoreticular malignancies, and 6 other disorders. The total diagnostic yield was 74 per cent (23 of 31) of the forcepts transbronchial biopsy procedures, 82 per cent (14 of 17) of the percutaneous trephine lung biopsies, and 28 per cent (9 of 31) of the bronchial brush biopsies. An etiologic diagnosis, including a variety of viral fungal, and parasitic diseases, was obtained in 42 per cent (13 of 31) of the transbronchial biopsy procedures and 65 per cent (11 of 17) of the percutaneous trephine lung biopsies. The etiologic diagnostic yield was increased to 48 per cent when bronchial brushing was combined with forceps transbronchial biopsy. Hemorrhage complicated 26 per cent of the transbronchial biopsy procedures and 17 per cent of the percutaneous trephine biopsies, whereas pneumothorax occurred in 19 per cent and 60 per cent, respectively. Hemorrhagic complications in patients undergoing transbronchial biopsy occurred 3 times as frequently among the uremic patients (5 of 11, 45 per cent) as among the nonazotemic patients (3 of 20, 15 per cent). Patients with thrombocytopenia, when corrected by platelet infusion, presented no increased risk. Of the 52 patients, 19 (36 per cent) died 2 to 60 days after biopsy, but no fatalities were related per se to the biopsy procedure.

Oral fibroma in a captive python.

A massive growth in the lower jaw of an Indian python (Python molurus) was diagnosed from biopsy samples as a fibroma. Moderately satisfactory treatment was achieved by surgical excision.