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

Interactions between Candida albicans and the resident microbiota

Candida albicans is a prevalent, opportunistic human fungal pathogen. It usually dwells in the human body as a commensal, however, once in its pathogenic state, it causes diseases ranging from debilitating superficial to life-threatening systemic infections. The switch from harmless colonizer to virulent pathogen is, in most cases, due to perturbation of the fungus-host-microbiota interplay. In this review, we focused on the interactions between C. albicans and the host microbiota in the mouth, gut, blood, and vagina. We also highlighted important future research directions. We expect that the evaluation of these interplays will help better our understanding of the etiology of fungal infections and shed new light on the therapeutic approaches.

MiniBioReactor Array (MBRA) in vitro gut model: a reliable system to study microbiota-dependent response to antibiotic treatment

Background

Antimicrobial drugs are mostly studied for their impact on emergence of bacterial antibiotic resistance, but their impact on the gut microbiota is also of tremendous interest. In vitro gut models are important tools to study such complex drug–microbiota interactions in humans.

Methods

The MiniBioReactor Array (MBRA) in vitro microbiota system; a single-stage continuous flow culture model, hosted in an anaerobic chamber; was used to evaluate the impact of three concentrations of a third-generation cephalosporin (ceftriaxone) on faecal microbiota from two healthy donors (treatment versus control: three replicates per condition). We conducted 16S microbiome profiling and analysed microbial richness, diversity and taxonomic changes. β-Lactamase activities were evaluated and correlated with the effects observed in the MBRA in vitro system.

Results

The MBRA preserved each donor’s specificities, and differences between the donors were maintained through time. Before treatment, all faecal cultures belonging to the same donor were comparable in composition, richness, and diversity. Treatment with ceftriaxone was associated with a decrease in α-diversity, and an increase in β-diversity index, in a concentration-dependent manner. The maximum effect on diversity was observed after 72 h of treatment. Importantly, one donor had a stronger microbiota β-lactamase activity that was associated with a reduced impact of ceftriaxone on microbiota composition.

Conclusions

MBRA can reliably mimic the intestinal microbiota and its modifications under antibiotic selective pressure. The impact of the treatment was donor- and concentration-dependent. We hypothesize these results could be explained, at least in part, by the differences in β-lactamase activity of the microbiota itself. Our results support the relevance and promise of the MBRA system to study drug–microbiota interactions.

Drug use evaluation (DUE) of ceftriaxone: A quality metric in a pediatric hospital

BACKGROUND

Ceftriaxone is frequently used as empiric therapy because of its broad spectrum and dosing characteristics. The purpose of this study was to evaluate the appropriateness of ceftriaxone therapy among hospitalized children using drug use evaluation (DUE) methodology.

METHODS

Hospitalized patients who received one or fewer dose of intravenous ceftriaxone at Children's Hospital of Eastern Ontario between January 1, 2018, and June 30, 2018, were identified. Duration was defined as empiric if 72 or less and definitive if more than 72 hours. Two infectious disease physicians reviewed the charts and rated appropriateness using a previously developed scale.

RESULTS

A total of 276 ceftriaxone courses in 248 patients (mean age 6.0 y) were reviewed. Of these, 153 (55.4%) were assessed as definitively or possibly indicated. The most common reason for inappropriate empiric use was an overly broad spectrum. Of the 120 courses given empirically for which there was no indication, the three most common reasons were lower respiratory infections (51; 42.5%), head and neck infections (18; 15.0%), and intra-abdominal infections (15; 12.5%). Of the 39 (14.1%) courses of ceftriaxone that were given for more than 72 hours, 14 (35.9%) met criteria for a definitive or possible indication.

CONCLUSION

Ceftriaxone is still overused as empiric therapy. Although 85% of courses were discontinued after three doses, 14% were continued for longer than 72 hours, with approximately one-third ultimately meeting an indication. DUE using Canadian pediatric and local guidelines criteria is useful to identify clinical presentations for which narrower spectrum antimicrobials should be used.

Impact of antimicrobial therapy on the gut microbiome

The gut microbiome is now considered an organ unto itself and plays an important role in health maintenance and recovery from critical illness. The commensal organisms responsible for the framework of the gut microbiome are valuable in protection against disease and various physiological tasks. Critical illness and the associated interventions have a detrimental impact on the microbiome. While antimicrobials are one of the fundamental and often life-saving modalities in septic patients, they can also pave the way for subsequent harm because of the resulting damage to the gut microbiome. Contributing to many of the non-specific signs and symptoms of sepsis, the balance between the overuse of antimicrobials and the clinical need in these situations is often difficult to delineate. Given the potency of antimicrobials utilized to treat septic patients, the effects on the gut microbiome are often rapid and long-lasting, in which case full recovery may never be observed. The overgrowth of opportunistic pathogens is of significant concern as they can lead to infections that become increasingly difficult to treat. Continued research to understand the disturbances within the gut microbiome of critically ill patients and their outcomes is essential to help develop future therapies to circumvent damage to, or restore, the microbiome. In this review, we discuss the impact of the antimicrobials often used for the treatment of sepsis on the gut microbiota.

Effect of administration route and dose escalation on plasma and intestinal concentrations of enrofloxacin and ciprofloxacin in broiler chickens

Background

The (mis)use of fluoroquinolones in the fowl industry has led to an alarming incidence of fluoroquinolone resistance in pathogenic as well as commensal bacteria. Next to simply reducing antimicrobial consumption, optimizing dosage regimens can be regarded as a suitable strategy to reduce antimicrobial resistance development without jeopardizing therapy efficacy and outcome. A first step in order to limit antimicrobial resistance is to assess the exposure of the intestinal microbiota to enrofloxacin after different treatment strategies. Therefore, a study was conducted in broiler chickens to assess the effect of route of administration (oral versus intramuscular) and dose escalation (10 and 50 mg/kg body weight) on plasma and intestinal concentrations of enrofloxacin and its main metabolite ciprofloxacin after treatment with enrofloxacin once daily for five consecutive days. Four different parts of the intestinal tract were sampled: ileum, cecum, colon and cloaca. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to quantify both analytes in plasma and intestinal content. Sample preparation prior to LC-MS/MS analysis consisted of extraction with ethyl acetate. For intestinal content samples PBS buffer was added before extraction. The supernatant was evaporated to dryness and resuspended in water prior to analysis.

Results

The results in plasma and intestinal content demonstrated that biotransformation of enro- to ciprofloxacin in broiler chickens is limited. In general, the intestinal microbiota in cecum and colon is exposed to significant levels of enrofloxacin after conventional treatment (21–130 μg/g). A clear increase of intestinal concentrations was demonstrated after administration of a five-fold higher dose (31–454 μg/g). After intramuscular administration, intestinal concentrations were comparable, except for the higher levels in cloaca due to the complete bioavailability and urinary excretion.

Conclusions

The intestinal microbiota is exposed to high levels of the antimicrobial, after oral as well as parenteral therapy. Furthermore, a dose and time dependent correlation was observed. The impact of the detected intestinal levels on resistance selection in the intestinal microbiota has to be further investigated.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-014-0289-1) contains supplementary material, which is available to authorized users.

Association between vancomycin-resistant Enterococci bacteremia and ceftriaxone usage

OBJECTIVE

Vancomycin-resistant enterococci (VRE) have become a public health concern with implications for patient mortality and costs. Hospital antibiotic usage may impact VRE incidence, but the relationship is poorly understood. Animal investigations suggest that ceftriaxone may be associated with VRE proliferation. We measured antimicrobial usage and VRE bloodstream infection (VRE-BSI) incidence to test our hypothesis that increased ceftriaxone usage would be associated with a higher incidence of VRE-BSI.

DESIGN

Retrospective cohort study.

SETTING

University of Alabama at Birmingham Medical Center, a 900-bed urban tertiary care hospital.

PARTICIPANTS

All patients admitted during the study period contributed data.

METHODS

We conducted a retrospective analysis of antimicrobial usage and VRE-BSI from 2005 to 2008 (43 months). Antimicrobial usage was quantified as days of therapy (DOTs) per 1,000 patient-days. VRE-BSI incidence was calculated as cases per 1,000 patient-days. Negative binomial regression with adjustment for correlation between consecutive observations was used to measure the association between antimicrobial usage and VRE-BSI incidence at the hospital- and care-unit levels.

RESULTS

VRE-BSI incidence increased from 0.06 to 0.17 infections per 1,000 patient-days. Hospital VRE-BSI incidence was associated with prior-month ceftriaxone DOTs (incidence rate ratio, 1.38 per 10 DOTs; P = .005). After controlling for ceftriaxone, prior-month cephalosporin usage (class) was not predictive of VRE-BSI (P = .70). Similarly, prior-month usage of piperacillin-tazobactam, ceftazidime, cefepime, cefazolin, or vancomycin was not predictive of VRE-BSI when considered individually (P≥ .4 for all comparisons). The final model suggests that type of intensive care unit was related to VRE-BSI incidence.

CONCLUSIONS

Ceftriaxone usage in the prior month, but not cephalosporin (class) or vancomycin usage, was related to VRE-BSI incidence. These findings suggest that an antimicrobial stewardship program that limits ceftriaxone may reduce nosocomial VRE-BSI incidence.

Impact of digestive and oropharyngeal decontamination on the intestinal microbiota in ICU patients

PURPOSE

Selective digestive microbial decontamination (SDD) is hypothesized to benefit patients in intensive care (ICU) by suppressing Gram-negative potential pathogens from the colon without affecting the anaerobic intestinal microbiota. The purpose of this study was to provide more insight to the effects of digestive tract and oropharyngeal decontamination on the intestinal microbiota by means of a prospective clinical trial in which faecal samples were collected from ICU patients for intestinal microbiota analysis.

METHODS

The faecal samples were collected from ICU patients enrolled in a multicentre trial to study the outcome of SDD and selective oral decontamination (SOD) in comparison with standard care (SC). Fluorescent in situ hybridization (FISH) was used to analyze the faecal microbiota. The numbers of bacteria from different bacterial groups were compared between the three regimens.

RESULTS

The total counts of bacteria per gram faeces did not differ between regimens. The F. prausnitzii group of bacteria, representing an important group among intestinal microbiota, was significantly reduced in the SDD regimen compared to the SC and SOD. The Enterobacteriaceae were significantly suppressed during SDD compared to both SOD and SC; enterococci increased in SDD compared to both other regimens.

CONCLUSIONS

The composition of the intestinal microbiota is importantly affected by SDD. The F. prausnitzii group was significantly suppressed during SDD. This group of microbiota is a predominant producer of butyrate, the main energy source for colonocytes. Reduction of this microbiota is an important trade-off while reducing gram-negative bacteria by SDD.

Potential contribution of fungal infection and colonization to the development of allergy

Fungi have long been recognized as an important source of allergens in patients with atopic disease. In this review, we explore the hypothesis that fungal exposures resulting in colonization or infection directly influence the tendency of an individual to develop allergic disease. According to this hypothesis, fungal exposures especially those early in life may influence the manner in which the immune response handles subsequent responses to antigen exposures. Studies detailing this potential connection between fungi have already provided important insights into the immunology of fungal-human interactions and offer the potential to provide new approaches and targets for the therapy of allergic disease. The first half of this review summarizes the data concerning fungal infections and asthma, including possible connections between fungal infections and urban asthma. The second half explores the potential role of the fungal gastrointestinal microbiota in promoting allergic inflammation.

The "Microflora Hypothesis" of allergic disease

Predisposition to allergic disease is a complex function of an individual's genetic background and, as is the case with multi-gene traits, environmental factors have important phenotypic consequences. Over a span of decades, a dramatic increase in the prevalence of allergic disease in westernized populations suggests the occurrence of critical changes in environmental pressures. Recently, it has been shown that the microbiota (i.e. microflora) of allergic individuals differs from that of non-allergic ones and that differences are detectable prior to the onset of atopy, consistent with a possible causative role. Features of the westernized lifestyle that are known to alter the microbiota, such as antibiotics and diet, are also associated with allergy in humans. In this chapter, we discuss the "Microflora Hypothesis" for allergy which predicts that an "unhealthy" microbiota composition, now commonly found within westernized communities, contributes to the development of allergy and conversely, that restoring a "healthy" microbiota, perhaps through probiotic supplementation, may prevent the development of allergy or even treat existing disease. In testing this hypothesis, our laboratory has recently reported that mice can develop allergic airway responses if their microbiota is altered at the time of first allergen exposure.

The 'microflora hypothesis' of allergic diseases

Increasingly, epidemiologic and clinical data support the hypothesis that perturbations in the gastrointestinal (GI) microbiota because of antibiotic use and dietary differences in 'industrialized' countries have disrupted the normal microbiota-mediated mechanisms of immunological tolerance in the mucosa, leading to an increase in the incidence of allergic airway disease. The data supporting this 'microflora hypothesis' includes correlations between allergic airway disease and (1) antibiotic use early in life, (2) altered fecal microbiota and (3) dietary changes over the past two decades. Our laboratory has recently demonstrated that mice can develop allergic airway responses to allergens if their endogenous microbiota is altered at the time of first allergen exposure. These experimental and clinical observations are consistent with other studies demonstrating that the endogenous microbiota plays a significant role in shaping the development of the immune system. Data are beginning to accumulate that a 'balanced' microbiota plays a positive role in maintaining mucosal immunologic tolerance long after post-natal development. Other studies have demonstrated that even small volumes delivered to the nasopharynx largely end up in the GI tract, suggesting that airway tolerance and oral tolerance may operate simultaneously. The mechanism of microbiota modulation of host immunity is not known; however, host and microbial oxylipins are one potential set of immunomodulatory molecules that may control mucosal tolerance. The cumulative data are beginning to support the notion that probiotic and prebiotic strategies be considered for patients coming off of antibiotic therapy.

Antimicrobial resistance in livestock

Antimicrobial resistance may become a major problem in veterinary medicine as a consequence of the intensive use and misuse of antimicrobial drugs. Related problems are now arising in human medicine, such as the appearance of multi-resistant food-borne pathogens. Product characteristics, dose, treatment interval and duration of treatment influence the selection pressure for antimicrobial drug resistance. There are theoretical, experimental and clinical indications that the emergence of de novo resistance in a pathogenic population can be prevented by minimizing the time that suboptimal drug levels are present in the infected tissue compartment. Until recently, attention has been focused on target pathogens. However, it should be kept in mind that when antimicrobial drugs are used in an individual, resistance selection mainly affects the normal body flora. In the long term, this is at least equally important as resistance selection in the target pathogens, as the horizontal transfer of resistance genes converts almost all pathogenic bacteria into potential recipients for antimicrobial resistance. Other factors contributing to the epidemiology of antimicrobial resistance are the localization and size of the microbial population, and the age, immunity and contact intensity of the host. In livestock, dynamic herd-related resistance patterns have been observed in different animal species.

Faecal candida and diarrhoea

BACKGROUND

Candida species are frequently isolated from stools of children with diarrhoea but are not proven enteropathogens. It is hypothesised that faecal candida causes diarrhoea.

AIMS

To determine the prevalence of faecal candida in childhood diarrhoea and the relation between faecal yeasts and diarrhoea.

METHODS

Comparison of clinical and laboratory data, including quantitative stool culture for yeasts from 107 children hospitalised with diarrhoea and 67 age matched controls without diarrhoea.

RESULTS

Yeast species, predominantly candida, were identified in the stools of 43 children (39%) with diarrhoea and 26 (36%) without diarrhoea. The concentration of candida was positively associated with recent antibiotic use (p = 0.03) and with the presence of another enteric pathogen (p < 0.005), but not with patient age, nutritional status, or duration of diarrhoea.

CONCLUSION

Candida species do not cause childhood diarrhoea in well nourished children.

Cefotaxime and desacetylcefotaxime antimicrobial interactions. The clinical relevance of enhanced activity: a review

This presentation reviews 15 years of in vitro, pharmacokinetic, and clinical data concerning the active metabolite of cefotaxime sodium, desacetylcefotaxime. This principle metabolite maintains an antimicrobial activity and spectrum superior to so-called "second-generation" cephalosporins, plus it has an extended serum elimination half-life. Furthermore, it penetrates well into various important body compartments. The metabolite enhances cefotaxime potency by additive or synergistic antimicrobial interactions that can significantly reduce cefotaxime minimum inhibitory concentrations (MICs) among oxacillin-susceptible staphylococci, Streptococcus species including pneumococci resistant to penicillin, anaerobes, enteric bacilli, Pseudomonas aeruginosa, and when tested in human serum, some enterococci. The high activity of cefotaxime alone and the contributions of desacetylcefotaxime to the drug's total antimicrobial value must be considered in reestablishing correct dosing of this "third-generation" cephalosporin. Physicians should use cefotaxime susceptibility tests to direct appropriate, cost-effective dosing and the selection of co-drugs when needed. Moreover, empiric cefotaxime regimen doses should also be reduced for some infections at sites where expected pathogen MICs remain low (< or = 2 micrograms/ml).

The in vitro inactivation of thirteen beta-lactam antibiotics by other mechanisms than adsorption to faecal substance

We have investigated the antibiotic inactivating capacity of intestinal contents in vitro in faeces. In the presently reported study the influence of beta-lactamase catalyzed hydrolysis on the antimicrobial activity of 13 commonly used beta-lactam antibiotics was investigated, while the influence of non-specific adsorption of antibiotics to faecal compounds was also taken into account. The following antibiotics were tested: benzylpenicillin, amoxicillin, amoxicillin/clavulanate, cloxacillin, piperacillin, temocillin, cefuroxime, cefamandole, cephradine, cefotaxime, ceftazidime, aztreonam and imipenem. Faecal samples were obtained from 30 healthy volunteers. Six different concentrations of each antibiotic were added to 1 g of faeces. After 24 h of incubation at 37 degrees C the remaining amount of active antibiotic was determined by means of a "growth inhibition assay". The contribution to the test results of non-specific adsorption to macromolecules was calculated by means of a model and the inactivation data were subsequently corrected. The amount of antibiotic non-specifically bound to faecal macromolecules varied from 0% to 80% of the amount of antibiotic initially added to the faeces. A considerable difference was found in the degree of inactivation of several antibiotics. However, in contrast to earlier investigations, the results of this study show that in a normal population the influence of beta-lactamase catalyzed hydrolysis on the activity of beta-lactam antibiotics is apparently very small when compared to the influence of non-specific adsorption of beta-lactam antibiotics to faecal compounds.

Effect of intramuscular ceftriaxone on aerobic oral and faecal flora of 11 healthy volunteers

11 volunteers received 1 g ceftriaxone i.m. every 24 h for 5 consecutive days. Volunteers were selected on the basis of the "ceftriaxone inactivating capacity" of their faeces, which should be 250 mg/kg faeces. The effect of treatment on the aerobic oral and faecal flora was studied. In the oral flora a temporary suppression of the viridans streptococci occurred, which normalised already during treatment. More spectacular was the effect on the faecal flora: suppression of aerobic Gram-negative bacilli with overgrowth of yeasts and enterococci. Two weeks after treatment the results of the faecal cultures were almost the same as before treatment in most of the volunteers. One volunteer experienced severe diarrhoea, starting the day after completion of ceftriaxone treatment and lasting 2 days.

Third generation cephalosporins: safety profiles after 10 years of clinical use

Compared with aminoglycosides, chloramphenicol, sulfonamides, tetracyclines, and even penicillins, the cephalosporins represent a remarkably safe class of antibiotics. Among the cephalosporins, the extended spectrum, third generation agents developed generally produce few side effects and appear to be less allergenic than the penicillins. Nephrotoxicity has not been a problem at recommended doses. Some third generation agents can cause hypoprothrombinemia if not administered with vitamin K, and disulfiram-like reactions occur with some agents because of the presence of a thiomethyl tetruzole moiety affixed to the cephem nucleus. There is a greater incidence of diarrhea associated with the agents excreted through a primarily biliary route, and this may contribute to the selection of drug resistant bacteria. Some agents are less active against staphylococci and their use may result in an increased incidence of superinfection or overgrowth of enterococci. If attention is given to the potential for adverse effects, many of these problems can be avoided and the third generation cephalosporins can be used safely in hospitals, nursing homes, and home care settings.

Safety of parenteral third-generation cephalosporins

Knowledge of side effects associated with different cephalosporins may be of help to prescribers. There are several side effects that are common to all cephalosporins, but overall, cefotaxime and ceftizoxime cause the fewest adverse reactions. Bleeding is probably the most common serious side effect of cephalosporins. Moxalactam causes coagulopathy and bleeding more often than do other cephalosporins, probably because it is carboxylated and has a methylthiotetrazole side chain. Cefoperazone also has a methylthiotetrazole side chain and may cause bleeding, particularly when used in doses greater than 4 g per day. Ceftriaxone has a similar side chain and there is some evidence that it can induce a coagulopathy. Coagulation tests should be monitored when any of the third-generation cephalosporins are given to patients with a high risk of bleeding. Disulfiram-like reactions are also related to the side chains associated with coagulation defects and have been reported when patients receiving cefoperazone, moxalactam, or ceftriaxone have ingested alcohol. Seizures have been reported with ceftazidime, but are uncommon. Hematologic reactions are rare with all third-generation cephalosporins. Benign diarrhea and Clostridium difficile colitis probably occur most often with moxalactam, cefoperazone, ceftazidime, and ceftriaxone, but there are few good data on this issue. Ceftriaxone has the unique ability to cause sludge (also referred to as pseudolithiasis) to form in the gallbladder, particularly in children. This may be associated with nausea, anorexia, epigastric distress, and colic, and is usually detected using ultrasonography. The sludge dissolves and symptoms subside after therapy is discontinued. None of the third-generation cephalosporins is clearly significantly nephrotoxic, even when combined with aminoglycosides. Most of the third-generation cephalosporins have surprisingly few serious side effects, which make them attractive for use in the treatment of a wide variety of serious infections.

Use of new beta-lactam antibiotics for surgical infections

The availability of beta-lactam antibiotics with extended spectra of activity against organisms commonly seen in surgical infections suggests that aminoglycoside-based therapy is no longer needed for most such community-acquired infections. The primary problems with specific beta-lactams are lack of activity against Bacteroides species and variable activity against Pseudomonas aeruginosa and enterococci. The pharmacokinetic properties of the newer beta-lactams vary considerably. This variation suggests specific settings in which these properties may be taken advantage of to improve clinical outcome.

Investigation of the biliary clearances of cefotaxime and desacetylcefotaxime by an original procedure in cholecystectomised patients

The biliary elimination of cefotaxime (CTX) and its metabolite desacetylcefotaxime (DSCTX) were measured by HPLC in nine recently cholecystectomised patients following the i. v. injection of 15 mg/kg body weight of CTX. All of the bile was collected by an original procedure: the inflated balloon of a Fogarty catheter was introduced into the distal branch of a Kehr drain T-tube. Biliary clearance of CTX and DSCTX was measured for 8 h. Cefotaxime peaked at 90 min after injection at 34.5 +/- 15.3 mg/l; in the 7-8 h sample it was 2.7 +/- 1.7 mg/l. DSCTX peaked at the same time at 49.3 +/- 17.0 mg/l, and was 4.6 +/- 3.2 mg/l at 8 h. The bile/serum ratio of CTX and DSCTX concentrations was above 1 from the first to the eighth hours (range: 1.35 +/- 1.08 to 11.0 +/- 3.1). The biliary clearance of CTX was 0.190 ml/min. The total amounts of CTX and DSCTX eliminated in bile were respectively 1050 +/- 472.8 micrograms and 1902.7 +/- 804.1 micrograms (0.093 +/- 0.041% of the dose and 0.186 +/- 0.077% of the dose). Considering the minimum inhibitory concentration of the pathogens currently encountered in biliary sepsis, CTX should be a suitable antimicrobial agent for the treatment of biliary infections.

[Biliary excretion of cefotaxime and desacetylcefotaxime]

The biliary excretion of cefotaxime (CTX) and its metabolite desacetylcefotaxime (DSCTX) was measured by HPLC in 9 recently cholecystectomized-patients following the IV injection of 15 mg/kg body weight of CTX. The totality of bile was collected by an original procedure: the inflated balloon of a Fogarty catheter was introduced into the distal branch of a Kehr drain T-tube. Biliary clearance of CTX and DSCTX was measured for 8 h. Cefotaxime peaked at 90 min. after injection at 34.5 +/- 15.3 micrograms/ml; in the 7-8 h sample it was 2.7 +/- 1.7 micrograms/ml. DSCTX peaked at the same time at 49.3 +/- 17.0 micrograms/ml, and was 4.6 +/- 3.2 micrograms/ml at 8 h. The bile/serum ratio of CTX and DSCTX concentration was 1 from the 1st to the 8th hours (range: 1.35 +/- 1.08 to 11.0 +/- 3.1). The biliary clearance of CTX was 0.190 ml/min. The total amounts of CTX and DSCTX eliminated in bile were respectively 1050 +/- 472.8 micrograms and 1902.7 +/- 804.1 micrograms (0.093 +/- 0.041 p. 100 of the dose and 0.186 +/- 0.077 p. 100 of the dose). Considering the minimum inhibitory concentration of the pathogens currently encountered in the biliary sepsis, CTX should be a suitable antimicrobial agent for the treatment of biliary infections.

The effect of selective decontamination of the digestive tract with the addition of systemic cefotaxime on the aerobic faecal flora of mice

The administration per-orally to mice of the non-absorbable antibiotics polymyxin E, tobramycin and amphotericin B resulted in the elimination of detectable aerobic gram-negative rods from the faecal flora without affecting the total viable aerobic count. The addition of parental cefotaxime to the regime caused a fall in the number of aerobic lactobacilli and an increase in the number of enterococci. The rise was associated with the translocation of viable enterococci to the mesenteric lymph nodes and the spleen. The changes induced by cefotaxime were reversed when the antibiotic was withdrawn. Following withdrawal of all antibiotics the total aerobic faecal flora increased to above normal levels, but there was no associated diarrhoea. Attempts to implant exogenous enterobacteria into the digestive tract resulted in only low level colonization both in treated mice and in control mice. These results may have implications for the use of this antibiotic regime for selective decontamination of the digestive tract in humans, particularly those who are immunocompromised.