The effect of new broad-spectrum antibiotics on faecal flora of cancer patients

The effects of newly available broad-spectrum antibiotics, used for infection prophylaxis and therapy in cancer patients, on faecal aerobic and anaerobic bacteria were investigated. Quantitative and qualitative aerobic and anaerobic cultures were performed in 34 patients before therapy and between the sixth and eleventh day of therapy. Of the two prophylactic regimens norfloxacin plus amphotericin-B eliminated Enterobacteriaceae and enterococci without encouraging growth of yeasts or Clostridium difficile whereas trimethoprim-sulphamethoxazole did not eliminate enterococci and colonization with toxin producing C. difficile occurred in two of ten patients. The effect of the two infection prophylaxis regimens on counts of faecal anaerobes was comparable. Monotherapy with ceftazidime and combination therapy with ceftazidime plus tobramycin did not result in major changes (greater than or equal to 3 log increase or decrease) in faecal anaerobic bacteria. Enterobacteriaceae were eliminated except in one patient treated with ceftazidime. The effect of these therapeutic regimens on enterococci was variable. Colonization by yeasts or by toxin negative C. difficile (two of three patients) were found in the ceftazidime group only. During combination therapy with piperacillin plus amikacin for fever during granulocytopenia signs of a disturbed faecal flora were found in one of three patients. Changes in faecal anaerobic bacteria were most marked in the ceftazidime plus piperacillin group. Moreover the isolation of a toxin positive C. difficile occurred in this group, in a patient who was colonized with toxin negative C. difficile before treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Selection of resistance to gentamicin and netilmicin in the faecal flora following prophylaxis for colo-rectal surgery

The selection of aminoglycoside-resistant bowel flora, following the administration of either gentamicin or netilmicin in combination with metronidazole for prophylaxis, during colo-rectal surgery in 88 patients has been examined. Both antibiotic regimens resulted in the selection of an aminoglycoside-resistant flora in a total of 57 (65%) of patients: in half of the patients there was a net gain in the aminoglycoside-resistant flora, and in 13 (15%) one aminoglycoside-resistant strain present prior to prophylaxis was displaced by another following operation. Three patients (3%) lost aminoglycoside-resistant strains after prophylaxis. Most of the resistant organisms selected were considered to be of little importance as potential pathogens, at least in the short term. In only a small minority (5%) of patients were aminoglycoside-resistant enterobacteria isolated. Aminoglycoside-resistant Staphylococcus aureus was not isolated. Of the resistant enterobacteria, only one strain, an isolate of Enterobacter cloacae selected in a patient receiving gentamicin, carried a resistance determinant which was self-transmissible to Escherichia coli.     

The effect of antimicrobial agents on fecal flora of children.

Influences of antibiotics on the fecal flora in children were studied for oral ampicillin, penicillin V, erythromycin, cefaclor, and gentamicin and for intravenous ampicillin, methicillin, cefpiramide, and ceftazidime. All antibiotics affected the normal flora, although the quality and quantity of the changes were variable. No substantial differences were noted between the oral and intravenous use of ampicillin with regard to its effect on the flora. Three penicillins, ampicillin, penicillin V, and methicillin, caused remarkable changes. The characteristic pattern observed was the considerable suppression of Bifidobacterium, Streptococcus, and Lactobacillus species. Although enterobacteria did not significantly change in number, Klebsiella spp. frequently replaced Escherichia coli. In patients given erythromycin and cefaclor, the reduction in the number of Bifidobacterium spp. was 1 log10 and that of members of the family Enterobacteriaceae was 3 log10. Gentamicin administered orally caused a drastic change, including a remarkable decline of E. coli to less than 2 log10/g of feces. Cefpiramide, a parenteral expanded-spectrum cephalosporin, suppressed normal flora so markedly that almost all species of organisms were eradicated, and the active growth of yeasts was promoted (2.6 log10 increase). Ceftazidime caused similar changes as cefpiramide, but the changes were less extensive. Yeasts increased after treatment with most antibiotic groups. This increase was particularly prominent in patients given oral penicillins and expanded-spectrum cephalosporins.     

Influence of antibiotic therapy on faecal carriage of P-fimbriated Escherichia coli and other gram-negative bacteria in neonates

The influence of previous antibiotic therapy on the aerobic faecal flora, including P-fimbriated Escherichia coli, was studied in 953 neonates at discharge from 22 neonatal wards in Sweden. Antibiotics, mainly ampicillin (with or without gentamicin) or cefuroxime, had been received by 37% of the infants. Treatment with ampicillin (with or without gentamicin) increased Klebsiella/Enterobacter and reduced Esch. coli colonization. Cephalosporin therapy (71% cefuroxime) reduced the frequency of colonization with both Esch. coli and Klebsiella/Enterobacter spp. but doubled the isolation rate of other Gram-negative bacteria (Citrobacter, Pseudomonas, Proteus and Acinetobacter spp.) and tripled the incidence of specimens yielding no aerobic Gram-negative growth. Gentamicin showed no significant ecological impact. The selection of Klebsiella/Enterobacter and P-negative Esch. coli strains by ampicillin was correlated with their resistance to this agent, while the association between P-fimbriated Esch. coli and cefuroxime therapy was not related to cefuroxime resistance.     

A comparison of the costs of ceftazidime therapy and gentamicin combinations in three UK hospitals.

This study compares the utilization costs of ceftazidime therapy with those of gentamicin in combination with other antibacterial drugs. The results show that the relatively high purchase cost of ceftazidime compared to combinations is more than counterbalanced by the additional materials used for drug administration and serum antibiotic assays, even when other drugs were combined with ceftazidime. The average drug and equipment costs were 230.13 pounds for ceftazidime regimens and 253.94 pounds for gentamicin regimens. It is also shown that ceftazidime therapy is associated with a reduction in personnel time compared to gentamicin regimens. The average times per patient for administration and assay were 1 h 43 min for ceftazidime and 4 h 57 min for gentamicin regimens. We conclude that ceftazidime regimens are cheaper than gentamicin regimens when all drug and equipment costs are quantified. Moreover, the use of ceftazidime will release staff time for other purposes.     

Effect of oral spiramycin on the faecal and oral bacteria in human volunteers

Six healthy adult volunteers were treated with 1 g of oral spiramycin twice daily for five days, and their oral and faecal microbial flora were studied. Mean saliva and serum concentrations of the antibiotic never exceeded 2.1 +/- 1.1 mg/l. The number of volunteers whose oral cavity was colonized by Enterobacteriaceae, group D streptococci, staphylococci, and fungi remained unchanged following treatment. The mean count of anaerobic faecal bacteria was 10.3 +/- 0.6 log10 cfu/g initially. This did not change significantly during the treatment, nor did the composition of the predominant anaerobic flora. Mean counts of group D streptococci were 1000 times lower than those of anaerobes before treatment, and also remained unchanged during therapy. No overgrowth of fungi, staphylococci, or Pseudomonas aeruginosa was observed. No significant modifications occurred in the mean total count of faecal Enterobacteriaceae (7.9 +/- 0.4 versus 7.4 +/- 1.0 log10 cfu/g of faeces before and during treatment respectively). However, faecal concentrations of highly spiramycin-resistant Enterobacteriaceae (MIC greater than or equal to 512 mg/l) increased from 4.8 +/- 1.2 to 7.0 +/- 1.8 log10 cfu/g during treatment. The MIC50 value of spiramycin for anaerobes, Enterobacteriaceae, and group D streptococci were 0.125, 64, and 0.5 mg/l respectively before treatment, and these increased to 1024, 512 and 1024 mg/l respectively during treatment. This was attributed to the rise in the faecal concentrations of spiramycin, which reached 689 +/- 48 micrograms/g of faeces on the fifth day of treatment. These concentrations decreased rapidly on cessation of treatment.     

The effect of amoxycillin on vaginal colonization resistance and normal vaginal flora in monkeys.

Previous studies have shown that vaginal colonization resistance in monkeys can be eliminated by amoxycillin and restored by flushing vaginal flora from a healthy monkey into the vagina of a monkey colonized with Escherichia coli. The hypothesis that the effect of amoxycillin resulted from elimination of parts of the normal flora was tested in the present study. Nine monkeys were flushed vaginally with amoxycillin daily for six days. The number of anaerobic bacteria decreased during amoxycillin administration, as did the number of species isolated. The most obvious effects were observed among the genera Bacteroides and Peptostreptococcus, while Lactobacillus spp. were less affected. Restoration of the flora after amoxycillin administration was slow in most of the monkeys. During amoxycillin administration, all monkeys became colonized spontaneously with E. coli. This was not, however, associated with increased adherence in vitro. The colonization persisted throughout the study period (29 days). It was concluded that amoxycillin disturbs vaginal colonization resistance by eliminating at least part of the normal vaginal flora, thereby promoting periurethral colonization with enterobacteria.     

Antibiotic therapy for patients with spinal cord injury undergoing urologic procedures

This prospective study was performed to determine whether gentamicin can be prescribed routinely to patients with spinal cord injury undergoing urologic procedures, or whether antibiotic therapy must be selected on the basis of recent urine microbiologic test results. Between January 2004 and June 2005, procedures were performed on 38 patients, all of whom were prescribed antibiotics on the basis of a microbiology report. Sixteen patients who underwent urologic surgery during 2003 and received gentamicin empirically served as a control group. The patients clinical course was monitored for postprocedure sepsis. Only 12 patients received gentamicin as the sole antibiotic; 10 patients required an additional antimicrobial for urine samples that grew more than 1 organism and contained bacteria resistant to gentamicin; 26 patients needed antibiotics other than gentamicin for gentamicin-resistant uropathogens. Three patients with organisms sensitive to gentamicin as well as another antibiotic received an agent considered less nephrotoxic than gentamicin. After the procedure, sepsis occurred in only 1 patient, a man with chronic lymphocytic leukemia and small cell carcinoma of the urinary bladder. Three control group patients developed a fever in excess of 39°C. One of these patients did not require a change of antibiotic, another patient recovered after 3 changes of antibiotic, and the third patient recovered from septicemia after receiving ventilatory support. Antibiotics should be prescribed on the basis of recent urine microbiologic test results, and empiric therapy with gentamicin should be avoided in patients with spinal cord injury who are scheduled to undergo urologic procedures.     

Ceftazidime as initial therapy for suspected bacterial infections in hospitalized pediatric patients

Ceftazidime, a new beta-lactam antibiotic, was used to treat 60 children with suspected bacterial infections occurring outside the central nervous system. The patients ranged in age from 0.1 to 21 years and received 30 mg of ceftazidime per kg up to a total single dose of 1 g administered every 8 h. Fifty-three pathogens were isolated from 43 children before the initiation of therapy. All children responded clinically, although one child failed bacteriologically and five children were considered colonized at the end of ceftazidime therapy. Adverse reactions associated with ceftazidime administration were primarily alterations in laboratory parameters and were clinically insignificant. Ceftazidime administered on an 8-h dosing regimen is effective monotherapy for the treatment of childhood infections.     

Prolonged stability of antimicrobial activity in peritoneal dialysis solutions.

OBJECTIVE: To evaluate the stability of the antimicrobial chemical and bioactivity of gentamicin, vancomycin, and gentamicin and vancomycin in combination, and the stability of the bioactivity of ceftazidime, admixed in standard peritoneal dialysis solutions and then maintained over a 14-day period at room temperature or under refrigeration. SETTING: Peritoneal dialysis center and microbiology laboratory at a military, teaching medical center. MEASUREMENTS: Standard peritoneal dialysate bags admixed with gentamicin, vancomycin, gentamicin and vancomycin in combination, or ceftazidime were stored at either 4 degrees C or 20 degrees C for 14 days. Sequential aliquots were withdrawn and assayed for antibiotic activity by bioassay and, except for ceftazidime, immunoassay for chemical activity. The bioassay was performed using a standardized Kirby-Bauer disc method. Significance was determined by ANOVA and, where the effect size was significant at the p < 0.05 level, the application of the paired t-test or the Wilcoxon signed rank test to the difference in activity between the first and last samples. RESULTS: Antibiotic concentration by immunoassay did not significantly deteriorate over 14 days for vancomycin or gentamicin when either room temperature or refrigerated samples were studied. By bioassay, gentamicin and ceftazidime, but not vancomycin, lost moderate but significant activity over 14 days when refrigerated bags were assayed (except for an insignificant decrement in gentamicin in the combined vancomycin and gentamicin bags). Bags stored at room temperature, in general, lost significant bioactivity over 14 days, but to levels where clinical efficacy would still be expected. The vancomycin bioassay performed on the combination bags demonstrated a remarkably enhanced bioactivity, presumably reflecting synergy with gentamicin. CONCLUSION: These data indicate that the study antibiotics admixed with peritoneal dialysis fluids retain stable chemical activity, whether refrigerated or kept at room temperature, for at least 14 days. A moderate decrement in bioactivity occurred for study antibiotics when stored either refrigerated or at room temperature over 14 days, although clinically significant levels were maintained.The clinical significance of a possible synergy between vancomycin and gentamicin is yet to be determined.     

Piperacillin-tazobactam is more effective than ceftriaxone plus gentamicin in febrile neutropenic patients with hematological malignancies: a randomized comparison

GOALS: Efficacy and costs of empirical antibacterial therapy in febrile neutropenic patients are important issues. Several strategies have been reported to be similarly effective: monotherapy with cefepime, ceftazidime or a carbapenem or duotherapy with an antipseudomonal beta-lactam antibiotic or ceftriaxone in combination with an aminoglycoside. Piperacillin-tazobactam monotherapy is promising, but its role in this setting still has to be defined. PATIENTS AND METHODS: Of 212 consecutive febrile episodes in 130 neutropenic patients with hematological malignancies randomized to receive either piperacillin-tazobactam (4.5 g every 8 h; group A) or ceftriaxone (2 g once daily plus gentamicin 5 mg/kg once daily; group B), 183 episodes (98 group A, 85 group B) were evaluable for response. RESULTS: Defervescence within 72 h without modification of the antibiotic therapy was achieved in 56/98 episodes (57.1%) in group A and in 30/85 (35.3%) in group B (P=0.0047). If fever persisted, teicoplanin plus gentamicin (group A) or teicoplanin plus ciprofloxacin (group B) were added. All patients still febrile then received meropenem, teicoplanin and amphotericin B. With these modifications of antibiotic therapy, 89.8% of patients in group A had responded at 21 days but only 71.8% in group B (P=0.005). The mean total antibiotic drug cost in group A was only 39.4% of that in group B (euro 445 versus euro 1129; P=0.010). CONCLUSION: Piperacillin-tazobactam monotherapy is significantly more effective and cost-efficient than ceftriaxone plus gentamicin as first-line therapy in febrile neutropenic patients with hematological malignancies.     

Pattern of antibiotic therapy and clinical outcome in acute generalized peritonitis in semi-urban and rural Nigerians

To determine the pattern of antibiotic therapy and clinical outcome a prospective survey of all patients operated on for acute generalized peritonitis was undertaken. The male to female ratio was 1.7:1, and the mean age was 27.6 +/- 18.3 years. Operative findings were typhoid ilea perforation in 75 (38.1%), complicated acute intestinal obstruction in 44 (22.3%), complicated and uncomplicated acute appendicitis in 34 (17.3%), peptic ulcer perforation in 18 (9%) and traumatic intestinal injury in 11 (5.6%), representing the majority of the patients. A combination of chloramphenicol, gentamicin and metronidazole was given to 80 (40.6%), ampiclox, gentamicin and metronidazole to 72 (36.5%), ampiclox and gentamicin to 21 (10.6%) and other combinations to 5. A single antibiotic was administered in 13 (6.6%), that is clavulanate-amoxicillin, ampiclox, and cefuroxime. Antibiotics were changed in 37 patients (18.8%): to amoxicillin-clavulanate in 13, cefuroxime in 11, ceftriazone in 7, cefuroxime and metronidazole in 4 and amoxicillin-clavulanate and metronidazole in 2 patients. Postoperative complications were mainly wound infection in 105 (42.6%), wound dehiscence in 33 (16.7%), residual intra-abdominal sepsis in 19 (9.6%), residual intra-abdominal abscess in 17 (8.6%), postoperative chest infection in 14 (7%), incisional hernia in 11 (5.6%), anaemia in 6, faecal fistula in 5 and there was a mortality of 15.7%.     

Treatment of peritonitis in continuous ambulatory peritoneal dialysis (CAPD) with intraperitoneal cefazolin and gentamicin

Between 1983 and 1988 57 peritonitis episodes in an unselected patient population were initially treated with intraperitoneal cefazolin and gentamicin. The loading dose consisted of 500 mg cefazolin/L dialysate and 40 mg gentamicin/L dialysate. The maintenance dosage was 125 mg cefazolin and 8 mg gentamicin per liter dialysate. Forty-five (78.9%) patients were primarily cured with this regimen (responder group = RG). Twelve patients (21.1%) did not respond to the initial therapy (nonresponder group = NG). Eight peritonitis episodes in the NG (14.0% of all patients) were caused by tunnel infections and 2 by diverticulitis (3.5%). The cure rate in patients without tunnel infection or bowel disease was 95.7%. A relapse occurred in 2 patients (3.5%). Duration of therapy was assessed by daily white blood cell count (WBC) in the effluent and treatment was discontinued when the WBC was less than 100/microliters for 3 days. The mean duration of therapy with cefazolin and gentamicin was 8.1 days in the RG and 6.0 days in the NG. Nonresponders were subsequently treated with a modified antibiotic regimen on an average 11.9 days.     

Full and Broad-Spectrum In Vivo Eradication of Catheter-Associated Biofilms Using Gentamicin-EDTA Antibiotic Lock Therapy

Biofilms that develop on indwelling devices are a major concern in clinical settings. While removal of colonized devices remains the most frequent strategy for avoiding device-related complications, antibiotic lock therapy constitutes an adjunct therapy for catheter-related infection. However, currently used antibiotic lock solutions are not fully effective against biofilms, thus warranting a search for new antibiotic locks. Metal-binding chelators have emerged as potential adjuvants due to their dual anticoagulant/antibiofilm activities, but studies investigating their efficiency were mainly in vitro or else focused on their effects in prevention of infection. To assess the ability of such chelators to eradicate mature biofilms, we used an in vivo model of a totally implantable venous access port inserted in rats and colonized by either Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, or Pseudomonas aeruginosa. We demonstrate that use of tetrasodium EDTA (30 mg/ml) as a supplement to the gentamicin (5 mg/ml) antibiotic lock solution associated with systemic antibiotics completely eradicated Gram-positive and Gram-negative bacterial biofilms developed in totally implantable venous access ports. Gentamicin-EDTA lock was able to eliminate biofilms with a single instillation, thus reducing length of treatment. Moreover, we show that this combination was effective for immunosuppressed rats. Lastly, we demonstrate that a gentamicin-EDTA lock is able to eradicate the biofilm formed by a gentamicin-resistant strain of methicillin-resistant S. aureus. This in vivo study demonstrates the potential of EDTA as an efficient antibiotic adjuvant to eradicate catheter-associated biofilms of major bacterial pathogens and thus provides a promising new lock solution.     

Antibiotic-resistant bacteria in surveillance stool cultures of patients with prolonged neutropenia.

The value of stool surveillance for antibiotic-resistant gram-negative bacteria was analyzed in 86 neutropenic bone marrow transplant patients. Twice-weekly specimens were inoculated onto culture medium containing gentamicin plus carbenicillin. The recovered organisms were identified to the species level and tested for antibiotic susceptibility. Forty-eight resistant organisms were recovered from 35 patients. Thirteen isolates persistently colonized patients. Escherichia coli (29%) and Pseudomonas aeruginosa (19%) were the most frequently recovered organisms. Although most organisms were recovered while patients were on antibiotics, 15 isolates, including eight of nine resistant P. aeruginosa, were detected before antibiotics were initiated. The duration of antibiotic use was longer for patients persistently colonized than for those not colonized (P = 0.03). Of the 15 resistant organisms which caused infection, 12 were detected in the surveillance cultures. Infections by antibiotic-resistant organisms occurred more frequently in patients colonized than in those not colonized (P = 0.006) and more frequently in patients persistently colonized than in those colonized only once (P = 0.01). The absence of colonization or persistent colonization correlated well with the absence of infection (negative predictive values of 94 and 91%, respectively).     

Comparative efficacy of different beta-lactam antibiotics and gentamicin in Klebsiella pneumoniae septicaemia in neutropenic mice

The in-vivo activity of ceftazidime, cefotetan, imipenem/cilastatin, piperacillin and gentamicin against two strains of Klebsiella pneumoniae was evaluated in a model of experimental septicaemia in neuropenic mice. Single agent therapy with the aminoglycoside was highly effective against both strains. Among the beta-lactams, ceftazidime and cefotetan were nearly as active as gentamicin, whereas imipenem/cilastatin was slightly less effective, and the results achieved with piperacillin were markedly inferior.     

Amikacin and ceftazidime as empirical antibiotic therapy in severely neutropenic patients: analysis of prognostic factors

This study aimed to evaluate the efficacy of amikacine and ceftazidime as an empirical antibiotic therapy for neutropenic patients affected by haematological neoplasms and to investigate the presence of prognostic features suggesting a poor outcome with this antibiotic combination at the onset of infection. This could allow the identification of subgroups of patients with a low rate of response to amikacin/ceftazidime therapy; in these patients different initial empirical therapy may be indicated. The study population comprised 166 severely neutropenic (absolute neutrophil count below 500/l) oncohaematological patients with fever or clinical signs of infection. Multivariate analysis confirmed four negative prognostic factors: 3 or more days of hospitalization at the onset of an infectious episode, a diagnosis of acute myeloid leukaemia, a haematological disease status different from complete remission, the presence of pneumonia. Depending on how many factors are present, cases can be stratified into three groups, of significantly different prognosis: favourable (0 or 1 factor) 76% success; intermediate (2 factors) 52% success; unfavourable (3 or 4 factors) 19% success. At the onset of an infectious episode a subgroup of patients with a very low response rate to empirical amikacin/ceftazidime antibiotic therapy is identifiable, for whom a different therapy is indicated. Because of the high rate of proven or probable fungal infections in this group, the immediate administration of a systemic antifungal therapy, in addition to antibacterial agents, could be considered in these high-risk patients. Studies should be specifically addressed to evaluating a stratification of empirical antibiotic therapy according to risk factors present at the onset of infection.     

The effect of selective decontamination of the digestive tract on gastrointestinal enterococcal colonization in ITU patients

Objective The effect of selective decontamination of the digestive tract (SDD) on Intensive Therapy Unit (ITU)-acquired enterococcal infection and colonization was studied. Changes in the predominant species isolated and resistance patterns to antimicrobial agents were also studied.Design Three groups were investigated: historical control (HC), contemporaneous control (CC) and patients receiving SDD (topical polymyxin, amphoterecin B and tobramycin throughout ITU stay with intravenous ceftazidime for the first 3 days only).Setting Adult general ITU with 7 beds.Patients Patients with a nasogastric tube in situ and who were likely to remain in ITU for 48 h or longer were recruited.Results Enterococcal infections occured in 3 of 84 HC patients and 2 of 91 CC patients. There were no unit-acquired enterococcal infections in the SDD group. There were 140 episodes of enterococcal colonization occurring in 112 patients, with significantly more in the SDD and CC groups (p<0.05. There were no significant differences in antibiotic sensitivities between the three groups.Enterococcus faecalis was the most frequently isolated species.Conclusion SDD does not predispose to enterococcal infection but does encourage colonization in patients receiving the regimen and other patients in ITU at the same. There is a complex interaction of factors which influence faecal flora and the likelihood of patients becoming colonized or infected with enterococci.This study was supported by grants from Bristol and Weston Health Authority and Glaxo Research (UK). RW was funded as a Research Fellow by Glaxo Research Limited (UK). The results of this study were presented in part at the 90th Annual Meeting of the American Society for Microbiology, Anaheim, California, May 1990     

The influence of single dose intravenous antibiotics on faecal flora and emergence of Clostridium difficile

The influence of a single intravenous dose of antibiotic on faecal flora and the emergence of Clostridium difficile was studied in volunteers. Seventy-eight volunteers (13 groups of 6 receiving 5 penicillins and 8 cephalosporins) were given a single intravenous dose of antibiotic. Results were compared with a control group of 6 volunteers who did not receive an antibiotic. Changes in the faecal flora were monitored over two weeks. Only cephalosporins were associated with emergence of Cl. difficile, penicillins and controls were not. Frequency of emergence of Cl. difficile in the 6 volunteers in each of the cephalosporin groups were as follows: cephaloridine 0, cephazolin, 1 cefuroxime 1, cefoxitin 2, cefotaxime 2, latamoxef 3, ceftriaxone 2, cefotetan 4. Latamoxef (moxalactam) was associated with a significant rise in total aerobic bacterial counts largely due to increased counts of enterococci. Cefotetan eliminated Escherichia coli and Bacteroides fragilis from the faecal flora three days after administration.     

A between-species comparison of antimicrobial resistance in enterobacteria in fecal flora

Enterobacteria in fecal flora are often reported to be highly resistant. Escherichia coli is the main species; resistance data on other species are rare. To assess the effect of the host's environment, antimicrobial resistance was determined in fecal species of the family Enterobacteriaceae from three populations: healthy people (HP)(n = 125) with no exposure to antimicrobials for 3 months preceding sampling, university hospital patients (UP) (n = 159) from wards where the antibiotic use was 112 defined daily doses (DDD)/bed/month, and geriatric long-term patients (LTP) (n = 74) who used 1.8 DDD/bed/month. The mean length of hospital stay was 5 days for the UP and 22 months for the LTP. The isolates were identified to at least genus level, and MICs of 16 antimicrobials were determined. From the university hospital, resistance data on clinical Enterobacteriaceae isolates were also collected. Resistance data for on average two different isolates per sample (range, 1 to 5) were analyzed: 471 E. coli isolates and 261 other Enterobacteriaceae spp. Resistance was mainly found among E. coli; even in HP, 18% of E. coli isolates were resistant to two or more antimicrobial groups, with MIC patterns indicative of transferable resistance. Other fecal enterobacteria were generally susceptible, with little typically transferable multiresistance. Clinical Klebsiella and Enterobacter isolates were significantly more resistant than fecal isolates. The resistance patterns at both hospitals mirrored the patterns of antibiotic use, but LTP E. coli isolates were significantly more resistant than those from UP. Conditions permitting an efficient spread may have been more important in sustaining high resistance levels in the LTP. E. coli was the main carrier of antimicrobial resistance in fecal flora; resistance in other species was rare in the absence of antimicrobial selection.