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The hypothesis that elimination of facultative and strict anaerobic microorganisms from the gastro-intestinal tract by antimicrobial drugs in the period of time around allogeneic bone marrow transplantation (BMT) prevents acute graft-versus-host disease (GVHD), was examined in a cohort of 112 children grafted between 1989 and 2002 for hematological malignancies. All patients received T-cell replete marrow from human leukocyte antigens (HLA) matched sibling donors under identical transplantation conditions. To eliminate microorganisms from the gastro-intestinal tract, total gastro-intestinal decontamination (GID) was applied by high doses of non-absorbable antimicrobial drugs while the graft recipient was maintained in strict protective isolation. About half of the children (51%) proved to be successfully decontaminated, and about half (49%) unsuccessfully. One recipient got acute GVHD in the first group and 8 in the second group (p = 0.013). The degree of success of total GID was decisive for the occurrence of acute GVHD, irrespective of the presence of other risk factors such as higher age of recipient and/or donor, female donor for male recipient and carriership or reactivation of herpesviruses. Our results demonstrate that successful total GID of the graft recipient prevents moderate to severe acute GVHD. We suppose that substantial translocation of gastro-intestinal microorganisms or parts of these, functioning as microbial-associated molecular patterns (MAMP's), triggering macrophages/dendritic cells via pattern recognizing receptors (PRR's) is prohibited. As a consequence the initiation and progression of an inflammatory process leading to acute GVHD is inhibited.

Purpose: We studied whether the risk of central venous catheter (CVC) -related thrombosis increased after an episode of CVC-related infection in patients undergoing intensive chemotherapy. Secondly, we determined whether thrombosis can be predicted or excluded by CVC lock fluid surveillance cultures., Patients and Methods: In a prospective setting, 105 consecutive patients were carefully examined for CVC-related infection and thrombosis. In all patients, microbial surveillance cultures of CVC lock fluid were taken every other day. All patients with clinical suspicion of CVC-related thrombosis underwent Doppler ultrasound or additional venography., Results: The cumulative incidence of CVC-related infection was 24% (25 of 105 patients). Clinically manifest thrombosis occurred in 13 (12%) of 105 patients. In patients with CVC-related infection, the risk of thrombosis increased markedly in comparison to those without infection (relative risk, 17.6; 95% CI, 4.1 to 74.1). In patients having two or more positive subsequent CVC lock fluid cultures with identical micro-organisms, 71.4% developed thrombosis, as compared with 3.3% in patients with negative or a single positive culture., Conclusion: The risk of clinically manifest thrombosis is increased after an episode of CVC-related infection in patients undergoing intensive chemotherapy. Surveillance culturing of CVC lock fluid may be clinically useful in estimating the risk for thrombosis and the instigation of focused early intervention.

Since endotoxins are potent inducers of stem cell mobilization, we hypothesized that their presence in the gut may play a role in cytokine-induced mobilization. To address this possibility we added ciprofloxacin and polymyxin B to the drinking water of Balb/c mice mobilized with either interleukin-8 (IL-8), granulocyte colony-stimulating factor (G-CSF), or flt3 ligand (FL). The yield of colony-forming units (CFUs) was significantly reduced in all mice treated with these antibiotics when compared with controls (IL-8: 192 +/- 61 vs 290 +/- 64, P <.05; G-CSF: 1925 +/- 1216 vs 3371 +/- 1214, P <.05; FL: 562 +/- 213 vs 1068 +/- 528, P <.05). Treatment with ciprofloxacin eliminated only aerobic Gram-negative bacteria from the feces without effect on mobilization. Polymyxin B treatment did not result in decontamination but significantly reduced the number of mobilized hematopoietic progenitor cells (HPCs) most likely due to the endotoxin binding capacity of polymyxin B. More than 90% of the gastrointestinal flora consists of anaerobic bacteria. Elimination of the anaerobic flora by metronidazol led to a significantly reduced number of mobilized HPCs when compared with controls (IL-8: 55 +/- 66 vs 538 +/- 216, P <.05). Germ-free OF1 mice showed a significantly reduced mobilization compared with their wild-type controls (IL-8 controls: 378 +/- 182, IL-8 germ free: 157 +/- 53, P <.05). Finally, we performed reconstitution experiments adding Escherichia coli-derived endotoxins to the drinking water of decontaminated mice. This resulted in partial restoration of the IL-8-induced mobilization (67 +/- 28 vs 190 +/- 98.1, P <.01). Our results indicate that endotoxins serve as cofactors in cytokine-induced mobilization. Modification of the endotoxin content by antibiotic treatment may affect the yield of cytokine-induced mobilization.

The infected and inflamed periodontium can act as a focus for systemic infection in neutropenic cancer patients. The incidence of these oral infections is unknown, but probably underestimated. Periodontal infections can easily be overlooked, primarily because symptoms of gingival inflammation may be minimal and the infection may be located in deeper parts of the periodontium. Assessment of a patient's periodontal condition before the onset of profound neutropenia is critical to the diagnosis and the management of these potentially life-threatening infections. This review article is aimed at informing supportive care providers of recent insights into the pathogenesis of periodontal diseases and the role of subgingival microorganisms, with the emphasis on these infections in cancer patients treated with high-dose chemotherapy. Furthermore, a multidisciplinary approach to the management of periodontal infections and the need for future research is discussed.

Background: Cardiopulmonary bypass predisposes the splanchnic region to inadequate perfusion and increases in gut permeability. Related to these changes, circulating endotoxin has been shown to rise during cardiac surgery, and may contribute to cytokine activation, high oxygen consumption, and fever ("postperfusion syndrome"). To a large extent, free endotoxin in the gut is a product of the proliferation of aerobic gram-negative bacteria and may be reduced by nonabsorbable antibiotics., Objective: To evaluate the effect of preoperative selective gut decontamination (SGD) on the incidence of endotoxemia and cytokine activation in patients undergoing open heart surgery., Design: Prospective, randomized, placebo-controlled double-blind trial., Setting: Tertiary-care university teaching hospital., Intervention: Preoperative administration for 5 to 7 days of oral nonabsorbable antibiotics (polymyxin B and neomycin) vs. placebo. The efficacy of SGD was assessed by culture of rectal swabs., Patients: Forty-four patients (median age 65 yrs, 29 males) were included in a pilot study to establish the sampling points of perioperative measurements. Seventy-eight consecutive patients (median age 65 yrs, 55 males) were enrolled for the prospective study; of these, 51 were randomly allocated to take SGD (n = 24) or placebo (n = 27); 27 were included in a control group (no medication)., Measurements and Results: SGD but not placebo effectively reduced the number of rectal swabs that grew aerobic gram-negative bacteria (27% vs. 93%, respectively; p < .001). SGD did not affect the occurrence of perioperative endotoxemia, nor did it reduce the tumor necrosis factor-alpha, interleukin-10, or interleukin-6 concentrations (p > .20), as determined before surgery, upon aorta declamping, 30 mins into reperfusion, or 2 hrs after surgery. Also, SGD did not alter the incidence of postoperative fever or clinical outcome measures such as duration of artificial ventilation and intensive care unit and hospital stay., Conclusion: SGD effectively reduces the aerobic gram-negative bowel flora in cardiac surgery patients but fails to affect the incidence of perioperative endotoxemia and cytokine activation during cardiopulmonary bypass and the occurrence of a postperfusion syndrome.

The intra- and interlaboratory reproducibilities of a commercial sandwich enzyme-linked immunosorbent assay (ELISA) for the detection of Aspergillus galactomannan in serum (Platelia Aspergillus; Sanofi Diagnostics Pasteur, Marnes-La-Coquette, France) were evaluated in six laboratories of university hospitals. Twenty serum samples were obtained from 12 neutropenic patients including 6 with invasive aspergillosis. These samples were blinded and sent to each center together with eight blinded ELISA-negative serum samples spiked with known concentrations of galactomannan. The centers were provided with ELISA microtiter plates from a single batch and a detailed protocol. Ten clinical samples showed ELISA reactivity, while 10 samples were ELISA negative. The mean coefficient of variation (CV) of the optical density values was 4.24% within a single assay and 25.6% between runs. The interassay CV of the ratios for the serum samples tested was 18.6%. Analysis of ordinal interpretation of the ELISA result (i.e., negative, gray zone, or positive) showed excellent reproducibility. Recalculation of the cutoff values for positive and negative samples suggested that the cutoff level recommended by the manufacturer could be lowered from 1.0 to 0.8 for negative samples and from 1.5 to 1.0 for positive samples. The intra- and interlaboratory reproducibilities were excellent when the ELISA results were interpreted as ordinal data, but considerable variation in optical density values and, to a lesser extent, in the ratios for the serum samples tested, was observed between runs. High assay variability was also found for serum samples spiked with known concentrations of galactomannan. Therefore, antigen titers in serum samples from a single patient, measured in different runs, should be compared with caution.

The prevalence of penicillin-resistant viridans streptococci was studied in healthy children and in paediatric and adult patients with leukaemia to determine whether the frequent presence of penicillin-resistant streptococci in the oral cavity of children with leukaemia is the result of antibiotic therapy. Twenty of the oral swabs from 50 healthy children who had not received antibiotics in the three months prior to sampling yielded viridans streptococci that could be cultured on blood agar containing 2 micrograms/ml benzyl-penicillin. In 11 of the 20 cases the streptococci were resistant to penicillin (MIC > or = 4 micrograms/ml). This prevalence is significantly higher than that found in adult leukaemia patients (40% vs. < or = 5%) but is about the same as that found in paediatric patients with leukaemia. The high prevalence of penicillin-resistant streptococci in the paediatric age group should be considered when selecting therapy and prophylaxis, especially when the risk of infection with one of these cocci is enhanced.

To determine which patients are at high risk for disseminated fungal infection and should be given systemic prophylaxis, we studied the charts of 341 patients with malignant hematologic disorders who were admitted to our institution during 10 consecutive years. These patients represented 636 admissions; during these admissions, 60 invasive fungal infections occurred, with deaths in 44 cases. All patients who died of these infections either had persisting granulocytopenia and a poor prognosis for the underlying disease or suffered from chronic graft-vs.-host disease. Two of 58 patients who had no or low-level candidal colonization developed this infection (P < .001). Nine of the 10 patients with candidal infection had microbiologically proven bacteremia within the week preceding the candidal infection. After bone marrow transplantation, 8 of 10 patients with chronic graft-vs.-host disease vs. 2 of 36 without this disease (P < .001) developed fatal infection with Aspergillus species. The results of our study reveal that patients with high-level candidal colonization who were treated for microbiologically proven bacteremia and patients with chronic graft-vs.-host disease might benefit from systemic antifungal prophylaxis.

Patients undergoing bone marrow transplantation become immunocompromised for various reasons. Deep granulocytopenia, induced by conditioning (chemotherapy and total body irradiation), renders the patient at risk for serious bacterial and fungal infections. Our strategy for prevention of these infections by selective decontamination (SD) is the result of more than 15 years of clinical experience and research. The combination of antibiotics, used as standard SD (neomycin, polymyxin B, pipemidic acid and amphotericin B), with the application of local antimicrobial agents eliminates aerobic Gram-negative rods, Staphylococcus aureus and Candida spp. from the mucosal surfaces of the digestive tract, while the majority of the anaerobic flora persist and support colonization resistance (CR). The antibiotics used either are not resorbed or do not yield therapeutic serum concentrations. Antibiotics which induce therapeutic serum concentrations, such as ciprofloxacin and cotrimoxazole, are only used for SD on a limited scale. When Gram-negative rods persist despite intake of the standard regimen, ciprofloxacin is given until these persisting rods are eliminated. If the patients cannot swallow the oral regimen, i.v. cotrimoxazole is given temporarily. Streptococcal infections are prevented by the i.v. administration of penicillin for 14 days starting on the first day after cytotoxic treatment (conditioning for bone marrow transplantation). The combination of SD and systemic prophylaxis has been shown to be adequate; the major problem then remaining is a relatively mild catheter-associated infection with coagulase-negative staphylococci.

In a controlled randomized study among 48 patients undergoing 75 courses of aggressive antileukemic therapy, it was shown that cotrimoxazole was less effective than penicillin G in preventing septicemia due to viridans streptococci. Both antibiotics were given intravenously. During 35 episodes of chemotherapy in the group of patients on penicillin G only, one patient developed a streptococcal bacteremia; this contrasted with bacteremia and septicemia in seven patients during 40 episodes in the group on cotrimoxazole. In three of these seven patients, septicemia was associated with respiratory failure and it was the cause of death in one. Both aerobic gram-negative rods and streptococci which caused infection despite cotrimoxazole prophylaxis were resistant to cotrimoxazole. Side effects such as hypersensitivity and favorable or unfavorable interaction with the oral selective decontamination regimen were similar for the two drugs, with the exception of colonization with Candida spp, which occurred more often in patients on cotrimoxazole than in patients on penicillin.

The results of bacteriologic cultures of blood and heparin-lock fluid, both drawn from the central venous catheters of 54 consecutive oncohematologic patients, have been used to determine their value for the diagnosis of systemic and catheter-associated infection. In 30 patients with clinical signs of infection (bacteremia or septicemia), 74 of 1000 (7.4%) heparin-lock fluid cultures, 114 of 542 (21%) catheter-drawn blood cultures, and 36 of 134 (26%) venipuncture blood cultures became positive, whereas in 24 patients without clinical signs of infection the respective values were 5 of 700 (0.7%), one of 220 (0.4%), and none of ten cultures. Comparison of the results of cultures sampled on the same day reveals that the positive and negative predictive values for catheter-drawn blood cultures, with the venipuncture blood cultures taken as the standard for bacteremia, are 82% and 95% respectively. The results of heparin-lock fluid are indicative for clinically relevant colonization of the catheter. Three or more positive heparin-lock fluid cultures, sampled on subsequent days, were correlated with the occurrence of bacteremia or septicemia with a positive predictive value of 100%. The conclusions are supported by the results of scanning electron microscopy.

A study was performed to determine the effect of parenteral treatment with four broad-spectrum cephalosporins (cefoperazone, ceftriaxone, ceftazidime, and cefepime) on the number of aerobic gram-negative rods and on the outgrowth of Candida albicans and a multiresistant strain of Citrobacter freundii in the feces of mice. The estimated fractions of a parenteral dose that were excreted into the gastrointestinal tract were 0.37 for cefoperazone, 0.11 for ceftriaxone, 0.03 for ceftazidime, and 0.002 for cefepime. All four cephalosporins significantly decreased the number of aerobic gram-negative rods in the feces, and virtually all gram-negative rods were eliminated at high doses of cefoperazone, ceftazidime, and ceftriaxone. Furthermore, at high doses these three compounds led to a significant increase of the outgrowth of resistant Citrobacter freundii. The outgrowth of Candida albicans was increased at high doses of cefoperazone and ceftriaxone, whereas ceftazidime and cefepime did not have this effect. The most profound changes in the gastrointestinal ecology were observed during treatment with high doses of cefoperazone. The results suggest that the colonization resistance of the gastrointestinal tract can be substantially decreased by parenteral treatment with cefoperazone and, to a lesser extent, with ceftriaxone and ceftazidime.

Oral and parenteral administration of aztreonam and oral administration of tigemonam to conventional mice caused a decrease in the number of aerobic gram-negative rods in the feces. Oral treatment with high doses of aztreonam (greater than or equal to 25 mg/kg/day) and tigemonam (100 mg/kg/day) adversely influenced colonization resistance, whereas oral treatment with lower doses of the monobactams or parenteral treatment with aztreonam did not.

A study was performed to investigate the pharmacodynamics of aztreonam and tigemonam against Escherichia coli and Klebsiella pneumoniae in vitro and in vivo. The in vitro concentration-effect relationships were determined in short-term growth experiments. The in vivo dose-effect relationships were determined in an experimental thigh muscle infection in irradiated mice. In this model, E. coli was injected into one thigh muscle and K. pneumoniae was injected into the other. Throughout these experiments aztreonam was administered subcutaneously and tigemonam was administered orally. For analysis of the antibacterial pharmacodynamics, the following parameters were determined: the maximum effect as a parameter for efficacy, the 50% effective concentration (or dose) as a parameter for potency, and the slope of the concentration-effect relationship. To assess the relationship between the concentration of the antibiotic and the antibacterial effect in vivo, the pharmacokinetics of the two drugs in the plasma of mice were determined as well. The maximum in vitro and in vivo effects of aztreonam and tigemonam against both bacteria did not differ substantially. However, both drugs killed E. coli more effectively than K. pneumoniae, indicating that the maximum in vitro effect of these drugs against E. coli was higher than that against K. pneumoniae. The maximum in vivo effect of both drugs against E. coli was similar to that against K. pneumoniae. Furthermore, in vitro aztreonam was about twice as potent as tigemonam, but in vivo the reverse was the case. These findings were explained by pharmacokinetic differences between subcutaneously administered aztreonam and orally administered tigemonam, because concentrations of tigemonam in plasma remained at microbiologically active concentrations longer than those of aztreonam did.

Since 1988 a number of reports on the emergence of vancomycin-resistant enterococci have been published. We describe an additional case of colonization of and subsequent infection with a vancomycin-resistant Enterococcus faecalis in a bone-marrow transplant recipient, who had never before received vancomycin therapy. The strain was resistant to most antibiotics tested, including low-level resistance to gentamicin and cross-resistance to teicoplanin. It was sensitive to amoxicillin and the lipopeptide antibiotic daptomycin. The origin, the mode of acquisition and the incidence of vancomycin-resistant enterococci are still unknown. The clinical and bacteriological features of the cases reported thus far and the genetic and biochemical basis of vancomycin resistance are discussed.

After the occurrence of septicaemia with a vancomycin-resistant Enterococcus faecalis strain in a patient, it was decided to determine the number of carriers of vancomycin-resistant cocci among haematologic patients. During a period of six months 135 stool samples from 25 children, and 400 samples from 70 adults were studied. All samples from the children were negative for vancomycin-resistant cocci. Nine of the adult patients had cultures positive for cocci, all identified as enterococci, which were highly resistant to vancomycin (MIC greater than 250 micrograms/ml), sensitive to amoxicillin, moderately resistant to gentamicin, slightly resistant to teicoplanin, and sensitive to daptomycin. None of these patients had been given vancomycin prior to the isolation of the vancomycin-resistant enterococci.

A thigh muscle infection induced with Escherichia coli in irradiated mice was used as a model to compare the in vivo pharmacodynamics of the antibacterial effect of four cephalosporins (i.e., cefepime, ceftriaxone, ceftazidime, and cefoperazone) with the in vitro antibacterial pharmacodynamics of these drugs. The following in vitro pharmacodynamic parameters were determined: the maximum effect as a measure for efficacy, the 50% effective concentration as a parameter for potency, and the slope of the concentration-effect relationship. For analysis of the in vivo antibacterial pharmacodynamics, the same parameters were applied for the dose instead of the concentration. For the detection of a relationship between concentration and antibacterial effect in vivo, we determined the pharmacokinetics of the four cephalosporins in the plasma of mice. The results showed that, in general, there is a direct relationship between the in vivo and in vitro pharmacodynamics of these cephalosporins. The maximum effects of cefepime, ceftazidime, and cefoperazone were approximately similar in vivo and in vitro. The sequence of potency of these drugs was, in descending order, cefepime, ceftazidime, and cefoperazone. Ceftriaxone differed from the other three cephalosporins in that it displayed unexpected in vivo pharmacodynamics. Ceftriaxone was just as efficacious as the other three in vitro, but its maximum effect in vivo was much lower. This relatively low maximum effect of ceftriaxone in vivo was not explained by the pharmacokinetic characteristics of the drug. From the present results it can be concluded that the in vitro efficacy of cephalosporins does not necessarily have a predictive value for the in vivo efficacy.

Between 1974 and July 1987 the diagnosis of severe aplastic anaemia (SAA) was confirmed in 82 patients. Overall actuarial survival was 57% at 7 yr. Four patients recovered while receiving conventional therapy, and four died before treatment with antithymocyte globulin (ATG) or bone marrow transplantation (BMT) could be initiated. Nineteen patients (median age 19.6 yr) were treated with allogeneic BMT (11 as initial therapy, eight after ATG). Incidence of acute and chronic graft versus host disease was high, occurring in 14/16 and 4/11 patients at risk, respectively. Survival of BMT patients (18/19 transfused) was 32% at 7 yr. Of 63 patients treated with ATG, survival was 63% at 7 yr but decreased to 43% at 11 yr. The 2.5 yr survival following ATG was influenced by pretreatment disease severity (defined by percentage reticulocytes, granulocyte and platelet counts), age and--in patients under 45 yr of age--by sex. However, pretreatment disease severity was less in patients aged between 20 and 45 yr and in females. Concomitant androgen therapy, animal source of ATG, interval diagnosis--ATG (which was in general rather short) and aetiology did not influence survival. Thirty-four patients became transfusion independent for up to 26 months after ATG. A gradual increase in granulocyte and platelet counts could be observed over a period of many years, and 26 patients recovered to show a normal haemoglobin level, granulocytes greater than or equal to 1.0 X 10(9)/l and platelets greater than or equal to 100 X 10(9)/l). Late complications (paroxysmal nocturnal haemoglobinuria, myelodysplastic syndrome/acute leukaemia, hepatocellular carcinoma) were observed in nine patients who survived with autologous marrow function. Five died within 12 yr of initial therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

A study was performed to assess the effect of parenteral administration of imipenem on the intestinal microbial ecology of mice in relation to the therapeutic efficacy of the drug. The therapeutic effect of imipenem was assessed in a short-term experimental thigh muscle infection with Escherichia coli in irradiated mice. The maximum antibacterial effect of imipenem was approached at a single dose of 80 mg/kg. At this dose of imipenem the number of viable E. coli in the thigh muscle decreased from 9 x 10(6) to 4 x 10(5), whereas in untreated controls this number increased from 9 x 10(6) to 2 x 10(8). Daily administration of a dose of 80 mg/kg imipenem caused significant changes in the intestinal flora of conventional mice, despite the low concentrations of the drug (about 1 mg/kg) found in the caecum 30 min after infection of this dose. These changes consisted of an increase in the number of E. coli and enterococci and a decrease in the number of Staphylococcus aureus in the faeces. Furthermore, at this dose of imipenem, the number of Candida albicans recovered from the faeces after oral contamination with this organism was increased. We conclude from these animal experiments that the use of imipenem in high doses causes ecological changes in the intestinal bacterial flora with the potential to promote colonization by candida.

In order to prevent septicaemia with streptococci, 20 consecutive selectively decontaminated patients on intermediate high-dose Ara-C treatment for malignant haematological diseases were given penicillin G. The incidence of infection with streptococci decreased from 0.76 per episode (14 patients, 17 episodes) for controls who did not receive penicillin G to 0.11 per episode in the prophylaxis group (20 patients, 26 episodes). Simultaneously, a decrease in the incidence of respiratory failure was observed, i.e. 0.52 per episode for controls and 0.19 per episode for patients on penicillin G. The results suggest that septicaemia with streptococci triggers the development of noncardiogenic pulmonary oedema in patients with pre-existing damage of the lung due to aggressive cytotoxic treatment. This suggestion is supported by the sequence of events, regarding the occurrence of infection and respiratory failure and the results of measurements of antileukoprotease serum concentrations, a parameter for pulmonary capillary leakage. Taking into account the data in the literature and the results of the present study, the conclusion is drawn that in patients treated with (intermediate) high dose Ara-C, prevention of streptococcal septicaemia is associated with a decrease in the incidence of respiratory failure.

Mice made monocytopenic with etoposide or both granulocytopenic and monocytopenic with cyclophosphamide were infected in a thigh muscle with 3 x 10(6) CFU of Staphylococcus aureus; 1 h later erythromycin or roxithromycin was administered, and 4 h after that the number of CFU per thigh was determined. In vitro as well as in vivo, the maximal effect of both antibiotics was only bacteriostatic. Monocytopenia did not diminish the efficacy of either erythromycin or roxithromycin in vivo, whereas the combination of granulocytopenia and monocytopenia markedly decreased the efficacy of both drugs: a 4-fold dose increase was necessary to obtain the same final number of CFU at the site of infection as in the controls. It is concluded that granulocytes contributed substantially to antibiotic efficacy against S. aureus in this short-term infection model.

Modulation of the bacterial flora of patients with a high risk of acquiring an infection can be achieved in several ways. The approach used in the Leiden University Hospital is based on selective elimination of the aerobic bacteria in the oropharyngeal cavity and intestinal tract, leaving the anaerobic flora intact. This kind of selective modulation of the host flora has an advantage in that it does not affect the colonization resistance provided by bacterial antagonism, which prevents colonization by resistant but potentially pathogenic bacteria or fungi. The elimination of aerobic bacteria combined with nursing in protective isolation and consumption of food with few bacteria has led to a significant reduction of the incidence of major and fatal infections in patients during episodes of severe granulocytopenia. From these results it may be concluded that the objective of selective antibiotic modulation, namely, the prevention of infections, can be achieved with this approach.

A study was performed to assess the suppressive effect of ciprofloxacin on the aerobic gram-negative flora of the gastrointestinal tract in mice in relation to its effect on colonization resistance. Ciprofloxacin exhibited a potent decontaminating effect, with the maximum effect being reached at a dose of 8 mg/kg/day. At this dose aerobic gram-negative rods were eliminated from the gastrointestinal tract within 24h without any adverse influence on the parameters of colonization resistance measured.

To confirm the results obtained in an earlier study, the incidence of infection was evaluated in 54 patients (62 periods of admission), nursed in conventional rooms and given a regimen of antimicrobial agents intended to modulate the intestinal flora selectively as a method to prevent infection during severe granulocytopenia. In 62 patients receiving selective antimicrobial modulation (SAM), 18% acquired major infections which was similar to 19% in patients on SAM in an earlier double-blind placebo controlled study and lower than 47% in the controls. Evaluation of a large number of surveillance cultures showed that the presence of specific potentially pathogenic aerobic bacteria was associated with the occurrence of major infection. If the bacterial species in question were not found in the cultures the chance of becoming infected was less than 5%, whereas the chance ranged between 42 and 62% depending on the species involved when these microorganisms were isolated.

In order to study the effect of modulation of the intestinal flora on granulopoiesis, conventional mice were given drinking water with or without a combination of antimicrobial drugs, i.e. neomycin, polymyxin B, amphotericin B and nalidixic acid. These antimicrobial drugs, which selectively eliminate the aerobic gram-negative rods and suppress yeasts, are currently administered to our patients to prevent infection during granulocytopenia (nalidixic acid has been replaced by pipemidinic acid). After sublethal irradiation, mice on antimicrobial drugs were granulocytopenic longer than the controls. Although these differences were rather small, i.e. two days, the impact on the course of an experimental infection at the end of the period of granulocytopenia was substantial. After injection of 1 x 10(5) live bacteria into the thigh muscle, both groups of granulocytopenic mice exhibited an initial increase in the number of bacteria in the thigh muscle. After 18 h a further increase in the number of bacteria was found for 63% of the mice receiving antimicrobial drugs, whereas the number had dropped below the baseline in 77% of the controls. These differences were reflected in the incidence of bacteremia, i.e. positive blood cultures for the bacteria injected into the thigh muscle were found for 26% of the mice on antimicrobial prophylaxis versus only 2% of the control mice. Remarkably, the number of peripheral blood granulocytes correlated with the number of CFU isolated from the thigh 18 h after injection for the animals on prophylaxis but not for the controls. This might mean that modulation of the intestinal flora affects not only the number of circulating granulocytes, but also other host defense factors.

To reduce the frequency and severity of bacterial infection, selective antimicrobial modulation (SAM) was applied in 39 patients with severely decreased host defense mechanisms. The objective was to eliminate potentially pathogenic aerobic microorganisms with minimal disturbance of the normal anaerobic bacterial flora. Elimination of potentially pathogenic aerobic microorganisms was easily accomplished in patients not infected at hospitalization. The anaerobic flora seemed to be undisturbed, and selection of or overgrowth with resistant microorganisms did not occur. The microbiologic results of the SAM regimen correlated with the incidence of infection. Only three major infections occurred in 23 patients who were free of potentially pathogenic microorganisms; 10 major infections occurred in 16 patients who were not free of potential pathogens. Seven of these 10 infections were present at hospitalization. The incidence of major infections was 47% in the patients on the SAM regimen and 82% in a group of control patients with a similar risk of infection.

Small slices of agar, each containing about 10(5.5) Escherichia coli organisms, were preincubated either in the contents of rat cecum or in brain heart infusion broth for 2 h and then were transferred to a small sample of saline. The purpose of these experiments was to examine the ability of E. coli to grow on the substrate that penetrated from the contents of rat cecum into the agar slices. It appeared that preincubation in brain heart infusion broth gave rise to abundant growth, whereas only poor growth occurred after preincubation in the contents of rat cecum. This poor growth was completely reversed by adding brain heart infusion. The same experiments were repeated under anaerobic conditions, in which growth on substrate that penetrated from the contents of rat cecum into the agar slices was extremely poor. This extremely poor growth under anaerobic conditions was reversed to abundant growth by adding brain heart infusion broth. The addition of nitrate as an electron acceptor also stimulated growth of E. coli. Similar results were obtained with other bacteria and with human feces. The results can be interpreted as a demonstration that under anaerobic conditions such as occur in large intestines, bacterial antagonism is caused in a high degree by competition for substrate.

Thirty-three patients with acute nonlymphocytic leukemia were studied during remission-induction treatment in a double-blind, placebo-controlled, randomized study to ascertain the effect on the incidence of infection of an oral regimen of selective antimicrobial modulation (SAM). A decrease in the number of major acquired infections was observed: three infections occurred in 16 patients receiving the SAM regimen compared with eight infections in 17 patients given the placebo. The reduction of infection was correlated with a reduction of fever, with a reduction of the frequency of administration of antimicrobial agents for the treatment of infection, and with the selective elimination of aerobic and facultative anaerobic gram-negative rods from the digestive tract. Substantial unfavorable side effects were not observed.

20 patients with severe aplastic anemia were treated with anti-thymocyte globulin (ATG), 6 of them in combination with haplo-identical bone marrow. 7 patients (35%) showed a good clinical response within 6 months; they were off transfusions and had greater than or equal to 0.8 x 10(9)/l neutrophils. ATG had the greatest effect on red-cell production and the least on platelet production. The hematological recovery with ATG could not be predicted from the bone-marrow histology, CFU-c growth, or clinical data. However, patients with strong HLA antibodies seemed to respond more often. The actuarial survival was 55% at 5 years. Under intensive supportive care, even 7 out of 12 non-responders were alive after 1 year. ATG appears to be a useful form of therapy for patients with severe aplastic anemia who are not candidates for bone-marrow transplantation.

In 31 consecutive patients who received an allogeneic bone marrow transplantation the loss of proteins during the period at risk for acute graft-versus-host disease (aGVHD) was studied in order to determine whether the quantity of protein loss could be used for grading the severity of aGVHD. It was shown that the grade classified on the basis of the severity of skin rash, the quantity of diarrhea and the seriousness of cholestasis, correlated with serum albumin loss, intestinal plasma loss (expressed by the intestinal alpha 1-antitrypsin clearance) and the occurrence of inflammatory cells (leukocytes) in feces. The quantity of albumin lost by intestinal route accounted for only one third of the total albumin loss. To investigate whether the remaining part of it could be explained by capillary leakage elsewhere in the body, leakage of antileukoprotease from the tissue of the respiratory tract into the blood was measured. It was shown that the serum concentration of this proteinase inhibitor correlated with albumin loss. This means that capillary leakage also occurs in the lung during aGVHD. In conclusion, the loss of proteins can be used as a parameter of the severity of aGVHD once the proper diagnosis has been established. It appears that a combination of the current 'familiar' grading system and SAL yields a more objective classification system with a greater prognostic value.

The effect of conservative treatment of aplastic anaemia was evaluated retrospectively in 40 patients. No significant beneficial effect was provided by long-term high-dose oxymethalone in 20 patients or by metenolone, adrenstonolone, or testosterone in 14 patients. Splenectomy gave no improvement in the majority of cases, although in some it decreased the transfusion requirement. Immunosuppressive treatment was successful in 1 patient with a positive LE phenomenon. Until a specific treatment becomes available, the possibility offered by alternative treatment, e.g. bone marrow transplantation, in cases with poor prognostic parameters should be considered.

Partial antibiotic decontamination and reverse isolation were carried out in nine patients undergoing bone marrow transplantation. The aim of this approach was to eradicate the patient's endogenous potentially pathogenic bacteria while preserving the anaerobic flora of the gut, which help to prevent recolonisation. No exogenous infections developed, and only one patient developed an infection associated with endogenous recolonisation. Colonisation resistance seemed normal in patients during partial antibiotic decontamination. This form of decontamination deserves further study in patients with immunodepression.