Mechanisms and treatment of cancer cachexia.

According to a recent consensus, cachexia is a complex metabolic syndrome associated with underlying illness and characterised by loss of muscle with or without loss of fat mass. The prominent clinical feature of cachexia is weight loss. Cachexia occurs in the majority of terminal cancer patients and it is responsible for the deaths of 22% of cancer patients. Although body weight is, indeed, an important factor to be taken into consideration in any cachexia treatment, body composition, physical performance and quality of life should be monitored. From the results presented here, one can speculate that a single therapy may not be completely successful in the treatment of cachexia. From this point of view, treatments involving different combinations are more likely to be successful. The objectives of any therapeutical combination are two: an anticatabolic aim directed towards both fat and muscle catabolism and an anabolic objective leading to the synthesis of macromolecules such as contractile proteins.

Photobiomodulation of pain and inflammation in microcrystalline arthropathies: experimental and clinical results.

OBJECTIVE: This article presents the results of laser therapy in crystal (hydroxyapatite, calcium pyrophosphate, and urates) deposition-induced arthritis in rats and the clinical applications in humans. BACKGROUND DATA: Microcrystalline arthropathies are prevalent among geriatric patients, who are more vulnerable to the side effects of drugs. The effectiveness of laser therapy for pain relief, free of side effects, has been reported in painful conditions. METHODS: Two milligrams of each of the above-mentioned crystals was injected in both joints of the back limbs in three groups of rats; these groups were then treated with laser irradiation. Three other groups received no treatment after the injections. We determined the plasmatic levels of inflammatory markers (fibrinogen, prostaglandin E2, and TNF(alpha)), tissues (prostaglandin E(2)) and conducted anatomopathological studies. Twenty-five patients with acute gout arthritis were randomized into two groups and treated over 5 days: group A, diclofenac 75 mg orally, twice a day; and group B, laser irradiation once a day. Forty-nine patients with knee chronic pyrophosphate arthropathy were randomized into two groups and treated over 21 days; group A, diclofenac 50 mg orally, twice a day; and group B, laser irradiation once a day. Thirty patients with shoulder chronic hydroxyapatite arthropathy were randomized into two groups and treated over 21 days; group A, diclofenac 50 mg orally, twice a day; and group B, laser irradiation once a day. RESULTS: Fibrinogen, prostaglandin E(2), and TNF(alpha) concentrations in the rats injected with crystals and treated with laser decreased significantly as compared with the groups injected with crystals without treatment. Both laser therapy and diclofenac achieved rapid pain relief in patients with acute gouty arthritis without significant differences in efficacy. Laser therapy was more effective than diclofenac in patients with chronic pyrophosphate arthropathy and in patients with chronic apatite deposition disease. CONCLUSION: Laser therapy represents an effective treatment in the therapeutic arsenal of microcrystalline arthropathies.

Liver mitochondrial dysfunction and oxidative stress in the pathogenesis of experimental nonalcoholic fatty liver disease.

Oxidative stress and hepatic mitochondria play a role in the pathogenesis of nonalcoholic fatty liver disease. The aim of the present study was to evaluate the role of hepatic mitochondrial dysfunction and oxidative stress in the pathogenesis of the disease. Fatty liver was induced in Wistar rats with a choline-deficient diet (CD; N = 7) or a high-fat diet enriched with PUFAs-omega-3 (H; N = 7) for 4 weeks. The control group (N = 7) was fed a standard diet. Liver mitochondrial oxidation and phosphorylation were measured polarographically and oxidative stress was estimated on the basis of malondialdehyde and glutathione concentrations. Moderate macrovacuolar liver steatosis was observed in the CD group and mild liver steatosis was observed in the periportal area in the H group. There was an increase in the oxygen consumption rate by liver mitochondria in respiratory state 4 (S4) and a decrease in respiratory control rate (RCR) in the CD group (S4: 32.70 +/- 3.35; RCR: 2.55 +/- 0.15 ng atoms of O2 min-1 mg protein-1) when compared to the H and control groups (S4: 23.09 +/- 1.53, 17.04 +/- 2.03, RCR: 3.15 +/- 0.15, 3.68 +/- 0.15 ng atoms of O2 min-1 mg protein-1, respectively), P < 0.05. Hepatic lipoperoxide concentrations were significantly increased and the concentration of reduced glutathione was significantly reduced in the CD group. A choline-deficient diet causes moderate steatosis with disruption of liver mitochondrial function and increased oxidative stress. These data suggest that lipid peroxidation products can impair the flow of electrons along the respiratory chain, causing overreduction of respiratory chain components and enhanced mitochondrial reactive oxygen species. These findings are important in the pathogenesis of nonalcoholic fatty liver disease.

Corneal morphometry prior to and five years after corneal stromal photoablation: the possible role of topical anesthesia on postablative corneal morphometry / Morfometría corneal previa a y cinco años tras fotoablación estromal corneal: el posible papel de la anestesia tópica en la morfometría corneal postablativa

The aim of this study was to investigate central corneal thickness values prior to and five years after ablation of the central cornea using 193 nm UV radiation. Thirty eight eyes of 38 subjects were analysed in a prospective study. Central corneal thickness measurements were carried out prior to and 60 months after corneal stromal photoablation under a 160 ?m flap with the Summit Excimed SVS plus excimer laser (Summit Technology, Inc. Walthan, MA). Mean intended ablation depth was 55±20 ?m. Central corneal thickness measurements were carried out with the DGH 2000 AP ultrasonic pachymeter (DGH Technology, Inc., San Diego, USA). Consecutive central corneal thickness readings were made until three consecutive measurements were within 5 mm of each other. The mean of these three consecutive readings was used as the value of central corneal thickness in this study. Preoperative mean central corneal thickness was 556±55 ?m; five years later it was 513.41 ?m (p<0.001). The difference between the "theoretical" postablative corneal thickness values and the "real" corneal thickness values observed 60 months after stromal photoablation was also significant (p<0.001). Five years after central corneal stromal photoablation using 193 nm UV radiation there was a disparity between the programmed postoperative residual corneal thickness and the corneal thickness obtained by ultrasound pachymetry. Further research is neccesary in order to identify possible unexpected values of corneal thickness after a paracentral corneal stromal photoablation has been carried out (AU)

El objetivo de este estudio era investigar los valores del espesor corneal previo a y cinco años tras la ablación de la córnea central empleando radiación UV de 193 nm. Treinta ojos de treinta sujetos fueron analizados en un estudio prospectivo. Las mediciones del espesor corneal se realizaron previo a y 60 meses tras la fotoablación estromal bajo un flap de 160 micras con el láser excimer Summit Excimed SVS plus (Summit Technology, Inc. Walthan, MA). La media de la ablación intentada fue de 55ñ20 micras. Las mediciones del espesor corneal central se realizaron con el paquímetro ultrasónico DGH 2000 AP (DGH Technology, Inc. San Diego, USA). Se realizaron mediciones consecutivas del espesor corneal hasta que tres consecutivas de ellas estuviesen entre 5 micras de diferencia. La media de estas tres mediciones consecutivas se usó como el valor del espesor central en este estudio. El espesor central medio era 565ñ55 micras; cinco años después era 513ñ41 micras (p<0.001). La diferencia entre los teóricos valores del espesor corneal y los verdaderos observados 60 meses tras la ablación estromal también fue significativa (p<0.001).Cinco años tras la fotoablación estromal empleando radiación UV de 193 nm existe una disparidad entre el espesor residual postoperativo programado y el espesor corneal obtenido mediante paquimetría ultrasónica. Es necesaria mayor investigación con la finalidad de identificar los posibles valores inesperados del espesor corneal tras ser realizada una ablación estromal paracentral (AU)

He-Ne laser on microcrystalline arthropathies.

OBJECTIVE: The objective of this work is to assess the anti-inflammatory capacity of He-Ne laser therapy as determined by the plasmatic levels of inflammatory markers, fibrinogen, and TNFalpha and by histopathological study in rats with arthropathy induced by calcium pyrophosphate crystals. BACKGROUND DATA: Microcrystalline arthropathies are a group of diseases characterized by the deposit of different crystals in joints. MATERIALS AND METHODS: Two milligrams of dicalcium pyrophosphate crystals (DCPP) were injected in both joints of the lower limbs of rats during 2 days. A group was treated with laser of He-Ne (6 mW) on the injected joints during 3 consecutive days. After 96 h of the first injection, animals were sacrificed to determine TNFalpha using the ELISA method and fibrinogen was assessed using spectrophotometry. Sections from the lower limbs were used for histopathology. RESULTS: A statistically significant increase (p < 0.001) in plasma fibrinogen levels and TNFalpha was noted between the control group and the laser-treated group. The histological transversal section of a posterior limb joint of a rat injected with DCPP showed fibroadipose tissue with diffuse chronic infiltrate. The histopathology of the group of rats injected with DCPP and subsequently treated with He-Ne laser showed no inflammatory response. CONCLUSION: He-Ne laser treatment in the microcrystalline arthropathy induced in rats by DCPP injection might have an antiinflammatory effect, evaluated by fibrinogen plasma levels and TNF-alpha (inflammatory markers) and by the histopathology regressive process.

Effect of dexamethasone and pentoxifylline in combination with amoxicillin in the treatment of penicillin-insensitive pneumococcal pneumonia in guinea pigs.

A fatal guinea pig model of pneumococcal pneumonia was developed in order to evaluate the efficacy of amoxicillin combined with either pentoxifylline or dexamethasone. Parameters assessed were survival time and lung changes (alterations, bacterial colony counts, inducible nitric oxide synthase [iNOS] and cyclooxygenase-2 [COX-2] protein expression). Animals receiving pentoxifylline (50 mg/kg) showed higher survival rates than controls (p < 0.05). Animals which received amoxicillin (50 mg/kg), alone or combined, showed significantly higher survival rates than controls (p < 0.05). Animals dying in spite of receiving amoxicillin alone or combined had lung colony counts significantly lower than those that did not receive the antibiotic (p < 0.001), but their lungs showed identical changes. The correlation between COX-2 protein expression and mortality was rather high (r = 0.75). The addition of either dexamethasone or pentoxifylline to amoxicillin improved neither survival rates nor lung pathology when compared with the antibiotic alone.

The chemical architecture of the rat's periaqueductal gray based on acetylcholinesterase histochemistry: a quantitative and qualitative study.

The chemoarchitecture of the periaqueductal gray has been extensively studied, based on acetylcholinesterase reaction and comparing it to other chemical markers. We have divided the periaqueductal gray into four main longitudinal columns, namely dorsomedial, dorsolateral, lateral and ventrolateral. We also identified the dorsal midline column, the supraoculomotor cap and the juxta-aqueductal ring. The acetylcholinesterase gave rise to a strong reaction in the outer half of the lateral column, the outer half of the dorsomedial column, the supraoculomotor cap and the ventral half of the juxta-aqueductal ring. This labeling was in part complementary to that of the NADPH diaphorase and allowed the lateral column to be differentiated from the ventrolateral column. However, the inner half of both lateral and ventrolateral columns displayed the same chemical properties including acetylcholinesterase, tyrosine hydroxilase and serotonin. Thus, from the chemical view, these inner halves should be considered as one different region. Finally, the juxta-aqueductal ring was composed of two clearly different halves, i.e. dorsal and ventral. The dorsal half did not show any clear differences from the above columns and was negative for acetylcholinesterase, NADPH diaphorase and tyrosine hydroxilase, while the ventral half was clearly different from the lateral and ventrolateral columns and displayed a positive reaction to all those chemical markers. From these results, we strongly suggest the use of acetylcholinesterase histochemistry as a tool for accurate parcellation of the periaqueductal gray.

Supplementing pasture to lactating Holsteins fed a total mixed ration diet.

Beginning in September 1997, a 6-week study was conducted to compare performance and income-over-feed cost of lactating Holsteins cows fed either a total mixed ration diet (TMR) only, compared to TMR in the afternoon and pasture in the morning, or TMR in the morning and pasture in the afternoon. Fifty-four Holstein cows in midlactation, averaging 28.1 kg/d of milk, were used in the study. Cows were on pasture for 8 h/d after either the p.m. or the a.m. milking. Predominantly orchardgrass with lesser amounts of white clover and Kentucky bluegrass were grazed. Pasture was sampled once per week, and weekly composites were analyzed. Compressed sward height and herbage dry matter (DM) yield were estimated once per week. Milk yield was electronically recorded and was sampled biweekly. Body condition score and body weight (BW) was recorded at the beginning and end of the study. Income-over-feed cost was calculated for each treatment. Compressed sward height and DM yield averaged 12.7 cm and 1397 kg/ha, respectively. Pasture crude protein, neutral detergent fiber, and acid detergent fiber averaged 27.0, 55.7, and 26.9%, respectively, and net energy-lactation was 1.65 Mcal/kg of dry matter. Milk production was greater for cows on the TMR treatment (29.1 vs. 28.2 and 27.6). No significant difference occurred in percentage of milk fat (3.54, 3.42, and 3.46%), or protein (3.28, 3.20, and 3.22%) for the above respective treatments. The SNF content (8.77 vs. 8.67 and 8.63%) was higher in TMR cows. While BW change did not differ among treatments (23, 32, and 22 kg), body condition score change was greater in cows fed TMR only (0.14 vs. -0.06 and 0.01). As expected, TMR intake was greatest for cows fed TMR only and lowest for cows grazing after the p.m. milking (26.6 vs. 20.3 vs. 17.5 kg/d dry matter). Income-over-feed cost differed between treatments and was approximately 18.6 and 7.5% higher for cows grazing high quality pasture during the afternoon and the morning, respectively, compared with cows on the TMR treatment.

Milk production and composition, rumen fermentation parameters, and grazing behavior of dairy cows supplemented with different forms and amounts of corn grain.

The objectives were to compare milk production and composition, change in body weight and body condition score, rumen fermentation parameters and grazing patterns by cows when supplemented with different forms and amounts of corn grain. In experiment 1, 36 Holstein cows were supplemented with either 6, 6, 6, or 4 kg/d of dry matter of high moisture corn, coarsely ground corn, finely ground corn, or high moisture corn in two equal daily feedings, respectively. Milk yield (30.3 kg/d), milk protein (2.97%), and milk urea N (14.7 mg/dl) were not different among treatments. Body weight change and body condition score change were similar (23.1 kg and -0.24) for the 10-wk study. During experiment 2, four rumen cannulated cows in midlactation were supplemented with 6 kg/d of dry matter from either coarsely ground corn or high moisture corn in two equal feedings after milking. After the p.m. milking, ruminal pH was measured and rumen fluid samples, were collected from cows to determine ammonia N and volatile fatty acids at 0.5, 1, 2, 3, ...8 h post-corn feeding during grazing. Ruminal pH values were similar for corn supplements, and, with one exception, were 6.0 or below between 5 and 8 h. Ruminal ammonia-N concentrations reached a maximum at 7 h also. In experiment 3, 40 cows were observed for grazing behavior every 30 min for two consecutive days. Cows grazed an average of 6.4 h/d, 4.1 h in the afternoon and 2.3 h in the morning. Milk yield, milk composition, change in body weight, and body condition were similar regardless of the type or amount of corn supplemented.

Antimicrobial treatment of an experimental otitis media caused by a beta-lactamase positive isolate of Haemophilus influenzae.

A gerbil model of otitis media induced by a beta-lactamase producing and non-serotypeable isolate of Haemophilus influenzae was used to assess the in-vivo efficacy of co-amoxiclav and cefuroxime at low (5 mg/kg) and high (20 mg/kg) doses. The MIC of the antibiotics tested against the pathogen was 1 mg/L (1/0.5 mg/L for co-amoxiclav). The organism was inoculated (+/-10(6) cfu) by transbullar challenge directly in the middle ear and antibiotic treatment was commenced 2 h post-inoculation and continued at 8 h intervals for three doses. Only high dose co-amoxiclav significantly reduced the number of culture-positive specimens as compared with untreated animals or with other treatment groups (91.7% as compared with 36.7% for high dose cefuroxime). The results obtained in any treatment group were related to middle ear antibiotic level/MIC. Antibiotic concentrations in the middle ear 90 min after administration were about 10% of serum levels at 15 min, probably related to a slight inflammatory response. Only after high dose co-amoxiclav did the concentration in the middle ear exceed the MIC by a factor of four. In otitis media with effusion, if indicated, antibiotics active in vitro should be administered in high doses and, to avoid side effects, probably in short courses.

In vitro antibiotic sensitivity testing breakpoints and therapeutic activity in induced infections in animal models.

Antimicrobial susceptibility breakpoints are artificially designated to classify organisms as susceptible, intermediate or resistant but such values may differ according to the relative weight given to the microbiological, pharmacological and clinical information. Animal models of bacterial infections are considered necessary to establish tentative breakpoints before initiating clinical trials in humans. Studies in animals provide a preliminary indication of the most effective and least toxic concentration of the antibiotic and give a rational basis for the selection of dosages and schedules. Animal models of therapeutic efficacy have demonstrated the importance of the inoculum effect, showing that the minimum inhibitory concentration (MIC) determined with high inoculum (10(7)-10(8) CFU/ml) is, under some experimental conditions, a better predictor of therapeutic efficacy than the value obtained with standard (10(4)-10(5) CFU/Ml) inoculum. Studies in animals have demonstrated the failure of some fluoroquinolones in respiratory tract infections where Streptococcus pneumoniae was present or the efficacy of penicillins and third-generation cephalosporins for treating respiratory tract infections and meningitis by pneumococci with diminished susceptibility to such agents. Although most therapeutic models in animals should be carried out during preclinical studies, many are done during later phases of antibiotic development, as explicate models of what is seen in clinical practice.

Correlation of in-vitro activity and pharmacokinetic parameters with in-vivo effect of amoxycillin, co-amoxiclav and cefotaxime in a murine model of pneumococcal pneumonia.

In an attempt to determine the susceptibility breakpoints for amoxycillin, co-amoxiclav and cefotaxime in pneumococcal pneumonia, a neutropenic mouse model was established and tested with two strains having different susceptibility to penicillins and cefotaxime. With a penicillin-sensitive strain (MIC/MBC = 0.01/0.01 mg/L) the minimum dosage tested achieving significant cure was 2 mg/kg for amoxycillin, co-amoxiclav and cefotaxime. For the penicillin-insensitive strain (MIC/MBC = 1/2 mg/L), the minimum dosage tested giving significant cure was 50 mg/kg for amoxycillin and co-amoxiclav but 100 mg/kg for cefotaxime. Our results support the belief that MICs of amoxycillin, co-amoxiclav and cefotaxime for pneumococcal strains of < or = 0.5 or < or = 1 mg/L can be considered as clinically relevant susceptibility breakpoints.

Treatment of experimental endocarditis due to penicillin-resistant Streptococcus pneumoniae.

Using two strains of pneumococci for which MICs of penicillin were 1 and 4 micrograms/ml, those of cefotaxime were 0.01 and 0.5 micrograms/ml, and those of teicoplanin were 0.01 and 0.1 micrograms/ml, we studied the efficacy of different dosages of penicillin, cefotaxime, and teicoplanin in the treatment of experimental pneumococcal endocarditis in rabbits. Animals treated with dosages of penicillin G procaine needed to achieve levels in serum near the MIC for pneumococci showed a significant reduction in log10 CFU per gram of vegetation, as compared with the control (P < 0.001), although only 20% of the animals showed sterile vegetations. When levels of penicillin in serum were in the range of three- to fourfold the MIC, a greater reduction in log10 CFU per gram of vegetation was seen, and 88% of the animals showed sterile vegetations. Only the regimen of penicillin that provided concentrations in serum above the MIC throughout the interval between two doses provided constant sterilization of the cardiac vegetations. Dosages of cefotaxime and teicoplanin selected to achieve concentrations in serum equivalent to that obtained in humans during treatment resulted in levels of antimicrobial agents in serum hundreds or thousands of times higher than the MICs for the infecting strains. In terms of antimicrobial efficacy, cefotaxime and teicoplanin were equivalent to regimens with high dosages of penicillin.

[The development of an informational logic support for aiding diagnosis and treatment. The Edecan-Med program. I. The assessment of nutritional status]. / Elaboración de soporte lógico informático para ayuda al diagnóstico y tratamiento. Programa Edecan-Med. Parte I: Valoración del estado nutricional.

We present the elaboration of an informatic program (Informatic Logic Support [SLI]) as a clinical help in diagnosis and treatment, for use by compatible computers PC. In this first part dedicated to artificial nutrition, we explain the scientific support, the capture of anthropometric and biochemical data, the processing, the results and the conclusions delivered by the computer that inform us about all the calculated nutritional parameters the type of malnutrition, the surgical risk of morbimortality (nutritional prognostic), and the caloric needs.

Treatment of encrusted cystitis caused by Corynebacterium group D2 with norfloxacin, ciprofloxacin, and teicoplanin in an experimental model in rats.

Oral doses of norfloxacin (80 mg/kg of body weight per day) and ciprofloxacin (25 and 80 mg/kg/day) and intramuscular doses of teicoplanin (5 mg/kg/day), all administered once a day for 10 days, were evaluated as a means of preventing encrusted cystitis caused by Corynebacterium group D2. Zinc disks dipped into a 24-h broth culture of these microorganisms were inserted into the bladders of female Wistar rats, and treatment was started 14 days after bacterial challenge. The appearance of encrusted cystitis was directly related to a documented urinary tract infection by these coryneforms (71.7 and 0% for rats with positive and negative urine cultures, respectively). All rats that died between days 18 to 43 after bacterial challenge presented very severe encrusted cystitis, which was prevented by teicoplanin and high doses of ciprofloxacin. Rats surviving up to day 44 after bacterial challenge were sacrificed; they presented a lower incidence of encrusted cystitis which was also less severe, with teicoplanin and a high dose of ciprofloxacin being more active in reducing the rate of positive cultures (78.8 and 65.7% reduction, respectively). All antibiotics and doses used were active in vivo at preventing encrusted cystitis by Corynebacterium group D2, but the best therapeutic effect was obtained with teicoplanin.

Primary structure and inhibition of protein synthesis in eukaryotic cell-free system of a novel thionin, gamma-hordothionin, from barley endosperm.

A new sulfur-rich and basic polypeptide, designated as gamma-hordothionin, has been isolated from barley endosperm by a semi-preparative purification consisting of extraction with a volatile salt solution followed by high-performance liquid chromatography using a reversed-phase C4 column. The isolated polypeptide was found to be homogeneous by micro-two-dimensional gel electrophoresis in the presence of sodium dodecyl sulfate. The complete primary structure of gamma-hordothionin was determined by automatic degradation of the intact, S-carboxymethylated and S-pyridylethylated gamma-hordothionin and fragments obtained by proteolytic cleavage. gamma-Hordothionin consists of a single polypeptide chain of 47 amino acids with a calculated molecular mass of 5250 Da and contains four disulfide bridges. gamma-Hordothionin inhibits translation in cell-free systems derived from mammalian (rabbit reticulocyte, mouse liver) as well as non-mammalian (Artemia embryo) cells, at several levels. At low concentrations (1-10 microM) the protein seems to affect mainly the polypeptide-chain-initiation process, although it might also act at the elongation level. At higher concentrations (20-80 microM) this inhibitor induces activation of an eukaryotic polypeptide-chain initiation factor 2 alpha-subunit (eIF-2 alpha) kinase in hemin-supplemented reticulocyte lysates, as does hemin deficiency. The presence of the disulfide bridges in gamma-hordothionin appears to be essential for the eIF-2 alpha kinase activation. Based on its similarity at both the structural and functional level with the different genetic variants of thionins (alpha and beta-thionins, from wheat and barley), gamma-hordothionin is a putative member of the thionin family.

Relevance of the inoculum effect of antibiotics in the outcome of experimental infections caused by Escherichia coli.

The minimum dosage of antibiotics that reduced mortality in bacteraemic rats inoculated with two different Escherichia coli isolates was determined in an attempt to study the therapeutic importance of the inoculum effect. Low mortality rates (0-5%) at 48 h were obtained when antibiotics with minimal or no inoculum effect (ampicillin, cefuroxime, cefoxitin and gentamicin) were administered to yield serum levels 5 to 14 times the MIC, while antibiotics with a pronounced inoculum effect (piperacillin, cefotaxime and aztreonam) had to be administered to yield serum levels 57 to more than 1000 times the MIC determined with a standard (low) inoculum. All of the antibiotics with inoculum effect studied here are administered empirically in clinical practice at a higher dose than the microbiological and pharmacokinetic data would indicate (in order to reach peak serum concentrations exceeding the MICs of the pathogens by 4-10 times). Our experiment suggests that such high and empirical doses of antibiotics with inoculum effect may be justified.

Effect of Bacteroides fragilis on mortality induced by Escherichia coli in an experimental infection treated with cefotaxime, aztreonam or gentamicin.

The possibility that beta-lactamase-producing strains of Bacteroides fragilis can protect Escherichia coli from cefotaxime was studied in an in-vivo model of peritoneal infection in rats. The protective effect of cefotaxime, aztreonam and gentamicin in peritonitis induced by E. coli alone or combined with B. fragilis was evaluated by analysing mortality at 24 and 48 h after bacterial inoculation and treating the animals with two doses of each antibiotic. Comparisons, by drugs, at 24 and 48 h revealed that a statistically significant high mortality rate was obtained at 48 h when mixed infections were treated with cefotaxime, a drug very active in the infection caused by E. coli alone. Infections by mixed flora or E. coli alone treated with aztreonam or gentamicin did not show any significant difference in mortality rate analysed at 24 or 48 h. These in-vivo results confirm previous in-vitro studies and suggest that cefotaxime could be inactivated in mixed infections if a beta-lactamase-producing strain, such as B. fragilis, is involved in a clinical infection.