Toxicity and clearance of intravitreal cefotetan

Direct intravitreal injection of antibiotics plays an important role in the management of bacterial endophthalmitis. In the present study we investigated the toxicity and clearance of intravitreally injected cefotetan in a rabbit model. No toxic ocular side effects could be detected by electroretinography (ERG) or light and electron microscopy up to and including a single intravitreal dose of 1000 micrograms. Intravitreal injection of 2000 micrograms cefotetan resulted in mild degeneration of photoreceptor outer segments and, sporadically, in cataract formation. After intravitreal injection of 4000 micrograms, moderate toxic degeneration of photoreceptors occurred, with displacement and mitochondrial swelling of inner segments. In addition, lysosomal lamellar inclusion bodies could be detected in pigment epithelial cells. After a single intravitreal injection of 1000 micrograms cefotetan, concentrations greater than the minimum necessary for the inhibition of most commonly occurring intraocular pathogens (except Pseudomonas aeruginosa and Staphylococcus epidermidis) were maintained in the vitreous humor for greater than 48 h. Cefotetan may be a potentially important drug for intravitreal injection, especially in cases of gram-negative and suspected anaerobic endophthalmitis.

Antifungal activity of diethyldithiocarbamate

Sodium diethyldithiocarbamate (DTC) was evaluated for its ability to combat four different species of fungi in vitro. Using a microtiter-broth-dilution method we were able to demonstrate an antifungal activity against Candida albicans, Cryptococcus neoformans, Aspergillus fumigatus and Mucor mucedo in doses achievable by intravenous administration in man.

[Rational dosing intervals in streptococcal infections of the pharynx]

Optimum therapy of streptococcal pharyngitis is still a matter of great debate. Kill kinetics of streptococci group A were investigated under the influence of fluctuating concentrations of penicillin V, ampicillin, cefalexin and erythromycin. Antibiotic concentrations in our in vitro model were adjusted to concentrations found in vivo in tonsillar tissue, penicillin V showed superior antimicrobial activity to ampicillin, cefalexin and erythromycin. Only the eight hourly administration of concentrations determined after the in vivo administration of either 100,000 IU/kg BW penicillin or 100 mg/kg BW of ampicillin or cefalexin effectively eradicated streptococci in the kinetic model. beta-lactamase forming bacteroides did not interfere with the elimination of streptococci by non beta-lactamase stable antibiotics. These data suggest that penicillin V constitutes the optimum choice of antibiotic. Efficient eradication can be achieved by the administration of a total daily dosage of 100,000 IU/kg BW at 8 hourly intervals.

[Mechanisms of action of chemotherapeutic drugs--microcalorimetric studies]

The technique of microcalorimetry allows observation of the effects of antimicrobial agents on bacterial metabolism without interruption. In contrast to the traditional methods, microcalorimetry assesses the thermal activity rather than the multiplication of bacteria. With one exception - polymyxins show a rapid fall of the power-time-curve to the zeroline, just like disinfectants - one can clearly differentiate bacteriocidal chemotherapeutics from bacteriocidal disinfectants using microcalorimetry. Bacteriocidal chemotherapeutics are not able to put an immediate stop to the metabolic activity of the bacteria.

[Pathogens of urinary tract infections in ambulatory care--resistance status and pathogen spectrum]

320 bacterial strains, isolated in January 1988 in the course of routine diagnostic investigations from patients with urinary tract infections, were compared with 594 strains isolated in 1983. Samples originated from outpatients in Tyrol and Vorarlberg. Most of the strains examined proved to be sensitive to oral chemotherapeutics. No increase in resistance to standard agents was observed from 1983 to 1988; the most frequently isolated organisms are still E. coli and enterococci. In contrast to the situation in hospitals, bacteriological investigation of urinary samples is not mandatory for outpatients with acute urinary tract infection.

[Selection of physiologic bacterial flora by chemotherapeutic agents]

A variety of antimicrobial agents has been shown to induce alterations in the bacterial homeostasis of the human microflora. Although the role of the normal flora is still poorly understood, there is evidence that alterations in the flora have a number of important clinical consequences. The normal flora acts as a natural defence against colonization or infection with pathogens. In addition, the altered flora may assume importance as a reservoir of potential pathogens. Thus, antibiotic-induced colonization predisposes patients to subsequent endogenous infections with these organisms which, in turn, have been rendered partially or totally resistant to formerly highly active agents. Broad spectrum antimicrobials with a high degree of biliary elimination show a marked impact on the faecal flora. Susceptible enteric bacteria are eliminated within 48 hours and are replaced by enterococci and Candida albicans. Recolonization occurs after discontinuation of therapy by multiresistant organisms like Klebsiella/Enterobacter and Pseudomonas. Oral antibiotics also lead to substantial alterations in the composition and resistance patterns of the faecal flora. In clinical medicine we should be aware of the substantial alterations of the human microflora which may accompany the use of antimicrobial agents.

[The kinetics of bacterial killing by fluctuating concentrations of antibiotics]

Differences in kill kinetics and the regrowth pattern of bacteria under the influence of various antibiotics are frequently not represented by their MIC values. The area under the concentration curve represents antimicrobial activity more accurately than the peak concentration. Readministration of antibiotics should occur prior to bacterial regrowth for optimal efficacy. When administering combinations of antibiotics non-simultaneous dosing is superior to simultaneous administration.

Listeria monocytogenes cholecystitis

Listeriosis usually manifests at the extremes of age, during pregnancy or among immunocompromised individuals as an acute meningoencephalitis with or without associated septicemia. Localized infections are rare. We investigated the incidence of Listeria monocytogenes cholecystitis using the data of the Listeria reference laboratory of the University of Würzburg/FRG. Out of 467 culture proven L.m-infections in the years 1986 and 1987, two cases were localized infections of the gall bladder. Although studies of the microbiology of gallbladder infections have not demonstrated the recovery of Listeria monocytogenes as a pathogen in acute or chronic cases of cholecystitis, these two cases substantiate the existence of this rare form of listeriosis as an entity and support the theory of the importance of the gastrointestinal tract in the pathogenesis of Listeria infections.

Effects of disinfectants on bacterial metabolism evaluated by microcalorimetric investigations

The technique of microcalorimetry allows uninterrupted observation of the effects of antimicrobial agents on bacterial metabolism; bacteriostasis and bacterial death can be distinguished from one another directly from the thermal output, without the necessity of inactivating the antimicrobial drugs. In contrast to the traditional methods, microcalorimetry assesses the thermal activity of bacteria rather than their multiplication; the microcalorimetrical results correlate with those of traditional test methods as far as MIC (minimal inhibitory concentration) and MBC (minimal bactericidal concentration)_ are concerned. Microcolarimetry permits a clear differentiation between disinfectants and antibiotics/chemotherapeutics, except in the case of polymyxins which, like the tested disinfectants, show a rapid fall to the zero-line of the power-time-curve at bacteridical concentrations. At sub-bactericidal concentrations, however, each of the disinfectants tested produced an individually characteristic microcalorimetrical curve pattern. This leads us to suspect that the various disinfectants attack at different points in bacterial metabolism. Although the technique of microcalorimetry does not replace standard evaluation, it provides additional insight into the mode of action of disinfectants.

[Experience using bone marrow transplantation in the treatment of hematologic neoplasms and solid tumors]

Between October 1983 and October 1985, 12 allogeneic bone marrow transplantations from HLA-identical siblings were performed for treatment of malignant disease (11 haemopoietic malignancies) or severe aplastic anaemia (1 case). All patients showed prompt and complete engraftment of donor cells on average around day 17 after transplantation. 10 patients are alive and well 50-760 days after transplantation, without any signs of recurrence and partly without immunosuppressive therapy. Two patients died, one due to relapse of the leukaemia, and one as a result of CMV interstitial pneumonia. Graft versus host disease was seen in 6 of the 12 patients. Additional immunosuppressive therapy was necessary in 4 of them. The incidence of idiopathic interstitial pneumonia in our group of patients was low (two cases). Also tested was an experimental protocol for the treatment of chemotherapy-resistant metastatic solid tumours. After removal of all clinically detectable tumour tissue by maximal surgical therapy in 5 patients, residual systemic metastases were treated by means of total body irradiation and high-dose cyclophosphamide, followed by autologous bone marrow transplantation with curative intention. Relapse occurred in 4 patients between day 100 and 720 after BMT bone marrow transplantation. Only one patient remains without sign of relapse.

The influence of third-generation cephalosporins on the aerobic intestinal flora

The influence of three third-generation cephalosporins with varying degrees of biliary excretion on the aerobic flora was investigated. The faecal flora prior to therapy with one of these substances consisted mainly of anaerobic bacilli. Escherichia coli was present in concentrations of 10(9) organisms/g stool. Candida albicans and enterococci were observed in concentrations of 10(5) - 10(6) organisms/g stool. Within 24 hours after the administration of ceftriaxone and cefoperazone, the gram-negative aerobic flora was completely eradicated. C. albicans and enterococci increased to 10(9) organisms/g stool. Between the third and tenth days (mean 6.7 days) of therapy Pseudomonas aeruginosa, Enterobacter and Citrobacter in this order of frequency reappeared in the faecal flora with complete resistance to all betalactam antibiotics. C. albicans and enterococci decreased to 10(7) organisms/g stool. The anaerobic flora was largely unaltered. In contrast, cefotaxime had only a moderate influence on the aerobic faecal flora. Concentrations of gram-negative organisms decreased to 5 X 10(7) organisms/g stool during the first five days of therapy; the concomitant increase in C. albicans and enterococci was approximately 1 log 10. No alterations in the susceptibility pattern were observed. We would like to emphasize that substantial alterations of the faecal flora and the susceptibility pattern of antibiotics may accompany the use of antimicrobial agents, particularly those with a high degree of biliary elimination.