Efficacies of cefepime, ceftazidime, and imipenem alone or in combination with amikacin in rats with experimental pneumonia due to ceftazidime-susceptible or -resistant Enterobacter cloacae strains

The antibacterial activities of human regimens of cefepime, ceftazidime, and imipenem alone or in combination with amikacin against an isogenic pair of Enterobacter cloacae strains (wild type and its corresponding derepressed cephalosporinase mutant) were compared by using our nonlethal model of pneumonia with 180 immunocompetent rats. Compared with untreated animals, all beta-lactam-treated rats, except those inoculated with the mutant isolate and receiving ceftazidime, had significantly lower bacterial counts in their lungs 60 h after the onset of therapy. Although the combination of a beta-lactam and amikacin was more bactericidal than each corresponding antimicrobial agent alone, true synergy was noted only with cefepime and imipenem against the constitutive derepressed strain.

Kluyvera cryocrescens finger infection: case report and review of eighteen Kluyvera infections in human beings

We report a case of soft tissue infection with Kluyvera cryocrescens and a critical review of Kluyvera infections. A 31-year-old diabetic man used a new chemical for stripping the floor with his bare hands. Two days later he developed a blister on a finger which progressed to tenosynovitis in spite of intravenous nafcillin therapy. After 11 days culture and sensitivity results dictated treatment with intravenous ticarcillin/clavulanic acid. The wound was debrided twice, and later a skin flap was done. Wound cultures became sterile after 7 days of treatment with ticarcillin/clavulanic acid, and he recovered. This case represents the fourth clinical infection with K. cryocrescens and the eighteenth of Kluyvera to be reported. Four others were K. ascorbata, and the remaining ten Kluyvera infections in humans were not identified beyond genus. Our case and review of the 17 previous cases emphasize that while Kluyvera rarely cause disease, these opportunistic Gram-negative bacilli may be virulent in a variety of sites under as yet poorly defined host conditions. Sites of infection varied, but the brain and meninges were not among them. Two patients had diabetes mellitus, none had AIDS, and four died. Once shown clinically to be the cause of an infection, Kluyvera deserve aggressive treatment which acknowledges their ampicillin resistance.

[A simple kidney cyst in childhood]

OBJECTIVE

To report on a 6-year-old patient with an infected simple renal cyst.

METHODS/RESULTS

A 6-year-old girl was admitted on three occasions for acute infectious syndrome and right lumboabdominal pain. The ultrasound scans showed a simple cyst in the right kidney which contained cellular elements. The patient was treated with antimicrobials on each occasion and the symptoms disappeared a few days later. On her third admission surgery was decided due to the recurrent clinical symptoms, a persistently high erythrocyte sedimentation rate and the presence of intracystic cellular elements, which raised the suspicion of intracystic abscess or tumor. The patient was submitted to surgery; the cyst was drained, resected and the internal wall marsupialized. The postoperative period was unremarkable and the patient is asymptomatic 10 months after surgery.

CONCLUSION

The case described herein is uncommon; to our knowledge, a similar case has not been reported in the literature.

The mechanism of in vivo bacteriostasis of bovine lactoferrin

Recently we have reported that orally administered bovine Lf(bLf) exerts bacteriostatic effects against bacterial overgrowth in the intestine of specific-pathogen-free (SPF) mice fed milk. In this animal model, the in vivo bacteriostatic effect of bLf against the proliferation of intestinal Enterobacteriaceae, the bacteria most sensitive to bLf, was independent of the iron-chelating ability of bLf. In addition various proteolytic hydrolysates of bLf (with differing antibacterial activities in vitro) showed the same bacteriostatic effect as undigested bLf. These results suggest that the mechanism of in vivo bacteriostasis of Lf differs from the in vitro mechanism reported. In SPF mice fed milk differing in concentrations of lactose, glucose and galactose, the proliferation of intestinal Enterobacteriaceae was dependent on the carbohydrate concentration in the diet. The addition of 2% bLf to the diets significantly suppressed this carbohydrate-dependent proliferation of bacteria except in the case of diets containing excess carbohydrate. In germ-free mice fed sterile milk, the addition of 2% bLf to milk resulted in a significant decrease in concentrations of lactose, glucose and galactose in the cecal contents. In an in vitro assay system using everted sacs of the small intestine of SPF mice, both bLf and its pepsin hydrolysate apparently stimulated glucose absorption. Based on these findings, we propose that the in vivo mechanism of action of ingested bLf involves the stimulation of carbohydrate absorption resulting in a bacteriostatic effect against Enterobacteriaceae in the intestine of mice fed milk.

Decreasing antibiotic resistance of Enterobacteriaceae by introducing a new antibiotic combination therapy for neutropenic fever patients

Prompt empiric antibiotic therapy is of critical importance for patients with neutropenic fever. However, a major concern with important clinical consequences is the emergence of bacterial resistance to antibiotics. After using ceftazidime with a glycopeptide as initial empiric therapy for neutropenic fever, we were confronted with a 75% reduced susceptibility rate to ceftazidime of inducible Enterobacteriaceae collected in 1994. The initial empiric therapy was therefore replaced in May 1995 by a combination of cefepime with amikacin, with addition of a glycopeptide after 48 h if necessary. After this change, we observed a significant decrease in reduced susceptibility of inducible Enterobacteriaceae, not only to ceftazidime, but also to amikacin, cotrimoxazole and ciprofloxacin. There was also a decrease in reduced susceptibility of non-inducible Enterobacteriaceae, such as Klebsiella spp, to ceftazidime. The reduction of resistance may be related at least in part to the combined use of cefepime together with an aminoglycoside. This study shows that it is possible to reverse bacterial resistance by modifying the antibiotic regimen used.

Ciprofloxacin in preterm neonates: case report and review of the literature

We report the use of ciprofloxacin in a preterm boy suffering from an invasive multiple resistant Enterobacter cloacae infection. The treatment was effective, after other antibiotics failed, and no adverse effects were observed during 3 years of follow up. The literature on compassionate ciprofloxacin use in 28 preterm or low birth weight infants is reviewed. Ciprofloxacin has been used to treat neonatal pneumonia, meningitis and septicaemia and was effective in all cases. Side-effects were limited to dental dyschromia and one observation on the emergence of resistance. Pharmacokinetics of ciprofloxacin were studied in seven preterm infants; iv doses ranging from 4 to 40 mg/kg per day revealed adequate serum peak concentrations (0.98-5.7 mg/l) but trough-peak ratios were high (median ratio: 32%), suggesting slower elimination in preterm infants as compared to older children. CSF concentrations were 0.10-1.45 mg/l.

CONCLUSION

Ciprofloxacin treatment of preterm or low birth weight infants may be effective and without severe side effects in infections with bacteria resistant to other antibiotics

Control of an outbreak of a highly beta-lactam-resistant Enterobacter cloacae strain in a neonatal special care unit

Two successive outbreaks of colonization and infection with Enterobacter cloacae resistant to third generation cephalosporins (cephalosporin-resistant E. cloacae, CREC) and involving 15 infants occurred within 12 months in a neonatal special care unit. Isolates of clinical significance were obtained from four infants (urine 2 cases, blood, pleural drainage). According to epidemiological typing using computerized biochemical fingerprinting and pulsed-field gel electrophoresis (PFGE) the same CREC strain was found in both outbreaks. The origin of the strain and its reservoir between the two outbreaks remained unknown. Emphasizing strict barrier nursing of the infants had little or no impact on the presence and transmission of the strain in the unit. In contrast, replacing ampicillin plus cefotaxime as standard empiric therapy with penicillin G plus netilmicin plus consequent cohorting of newborns and staff promptly halted both the outbreaks. During a 5-y follow-up after the last episode, the choice of antibiotics for empirical treatment has varied, and no further outbreaks of CREC have been seen, with the exception of two sporadic cases.

Comparative activities of novel beta-lactamase inhibitors, 6-exomethylene penamsulfones (CH1240, CH2140) in experimental mouse infection model

The antibacterial activity of novel beta-lactamase inhibitors, 6-exomethylene penamsulfones (CH1240, CH2140), has been compared in vivo with that of sulbactam and clavulanic acid against beta-lactamase producing strains. In vivo microbiological assessment was used as experimental mouse infection model by gram negative strains. Against Pseudomonas aeruginosa F0013, cefoperazone/CH1240 was slightly less active than sulbactam. Ampicillin/CH1240 was more active than sulbactam against Citrobacter diversus species. That of ampicillin/CH2140 was less effective than sulbactam against Escheriachia coli 3457. Especially against Citrobacter diversus 2046E, amoxicillin/CH2140 was the most potent and amoxicillin/CH1240 was slightly more active than clavulanic acid. Consequently the difference in efficacy between the drug combinations appears to be related to the degree of protection afforded the animals by the beta-lactamase inhibitors. CH1240 and CH2140 are promising new agents and should undergo further investigations.

Comparison of antibiotic administration in conjunction with supportive measures versus supportive measures alone for treatment of dairy cows with clinical mastitis

OBJECTIVE

To determine whether antibiotic and supportive treatment would improve outcome for dairy cows with naturally developing clinical mastitis, compared with supportive treatment alone.

DESIGN

Randomized controlled trial.

ANIMALS

124 cows in one herd with 172 episodes of clinical mastitis.

PROCEDURE

Cows were examined at the onset of clinical mastitis, assigned a severity score, and randomly assigned to receive antibiotic (intramammary administration of cephapirin, i.v. administration of oxytetracycline, or both) and supportive treatment (administration of oxytocin, stripping of affected glands, and, in severely affected cows, administration of flunixin meglumine or fluids) or supportive treatment alone. Treatment was continued until 24 hours after signs of clinical mastitis resolved (clinical cure). Milk samples from affected glands were submitted for bacterial culture before initial treatment and every 2 weeks thereafter until the causative organism was no longer isolated (bacteriologic cure).

RESULTS

When mastitis was caused by Streptococcus spp or coliform bacteria, clinical cure rate by the tenth milking was significantly higher if antibiotics were used. Bacteriologic cure rate at 14 days was significantly higher when antibiotics were used, particularly if mastitis was caused by Streptococcus spp. Cows receiving antibiotics developed fewer subsequent episodes of clinical mastitis during the 60 days after the initial episode of mastitis and had less severe clinical disease than cows that did not.

CLINICAL IMPLICATIONS

Results suggest that, in herds in which mastitis is often caused by environmental bacteria, antibiotic and supportive treatment may result in a better outcome for cows with clinical mastitis than supportive treatment alone.

Infection in the intensive care unit: beta-lactamase-mediated resistance among Enterobacteriaceae and optimal antimicrobial dosing

Class I beta-lactamase-mediated resistance in Enterobacteriaceae is increasingly common, clinically important, and often associated with previous use of third-generation cephalosporins. Extended-spectrum beta-lactamases that confer resistance to third-generation cephalosporins are also becoming more widespread. Beta-lactamase-producing organisms often display multiresistance, and this has been associated with increased mortality among patients. For all beta-lactam antimicrobials, the time that the plasma concentration exceeds the minimum inhibitory concentration (MIC) is the principal factor determining antibacterial activity. For concentration-dependent antimicrobials such as aminoglycosides and fluoroquinolones, the area under the plasma-concentration time curve:MIC ratio is the variable that has the strongest link to clinical outcome, particularly when relatively low peak: MIC values (< 10:1) are achieved. Peak concentration is of major concern for suppression of resistance. When high peak: MIC ratios (> or = 10:1) are achieved, this may suppress resistance and become the primary variable linked to outcome. When designing antimicrobial dosage regimens, it is important to take into account the pharmacodynamics of the drug in order to maximize the potential for achieving a positive clinical outcome and suppressing the emergence of bacterial resistance.

Sparfloxacin vs ofloxacin in the treatment of acute bacterial exacerbations of chronic bronchitis: a multicenter, double-blind, randomized, comparative study. Sparfloxacin Multicenter ABECB Study Group

STUDY OBJECTIVE

Comparison of efficacy and safety of sparfloxacin vs ofloxacin for treatment of acute bacterial exacerbations of chronic bronchitis (ABECB).

DESIGN

Multicenter, double-blind, randomized study.

SETTING

Sixty-eight private offices and outpatient clinics in the United States and Canada.

PATIENTS

Seven hundred ninety-eight adults with ABECB, as confirmed by the acute onset of new (or worsened from the immediate premorbid state) cough and sputum production.

INTERVENTIONS

Randomization 1:1 to sparfloxacin, 400 mg on day 1, then 200 mg once daily, or ofloxacin, 400 mg twice daily, with matching comparator placebos, given concurrently for 10 consecutive days.

RESULTS

The primary efficacy parameter was overall response in the bacteriologically evaluable population. Overall success rates in this population were 85.3% and 89.3% for sparfloxacin and ofloxacin, respectively. The two-sided 95% confidence interval was -9.9, 1.9, indicating that sparfloxacin was statistically equivalent to ofloxacin. The all-treated population analysis was similar to that in the evaluable population. Bacterial eradication rates were similar in both treatment groups for Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, Chlamydia pneumoniae, Haemophilus parainfluenzae, Klebsiella pneumoniae, Enterobacter cloacae, and Staphylococcus aureus. The frequency of adverse events overall was comparable in the two treatment groups. The sparfloxacin group had a lower frequency of digestive and nervous system adverse events, but a higher frequency of photosensitivity reactions than the ofloxacin group.

CONCLUSIONS

Once-daily oral treatment with 200 mg sparfloxacin (after initial 400 mg dose) is as effective as twice-daily treatment with 400 mg ofloxacin in patients with ABECB.

Important and emerging beta-lactamase-mediated resistances in hospital-based pathogens: the Amp C enzymes

Resistance to third-generation cephalosporins mediated by beta-lactamases is an increasing problem for clinical therapeutics. A wide range of Enterobacteriaceae produce these AmpC enzymes (Bush-Jacoby-Medeiros group 1), including Enterobacter spp., Citrobacter freundii, Morganella morganii, Providencia spp., and Serratia marcescens. Resistance via this mechanism has been shown to be statistically correlated with the use of some third-generation cephalosporins, and the infections caused by these stably derepressed enzyme-producing species seem to occur most frequently in the seriously ill. More recently the genes encoding this enzyme have been documented on plasmids capable of transfer into other species such as Klebsiella pneumoniae. Fourth-generation cephalosporins, with stability and low affinity for the Amp C beta-lactamases and the ability to penetrate rapidly into the periplasmic space of Gram-negative organisms, offer a viable alternative in the treatment of these infections or as empiric regimens. Furthermore, these compounds (example: cefpirome) possess greater potency against the frequently occurring Gram-positive cocci such as oxacillin-susceptible staphylococci and the streptococci (including some penicillin-resistant strains) as compared to previously used anti-pseudomonal cephalosporias, ceftazidime.

[Intracranial hypertension in a newborn treated with quinolone]

BACKGROUND

Fluoroquinolones have not received administrative authorization for use in children, but because of multiresistant pathogens in neonatal intensive care, floroquinolones may be the only alternative.

CASE REPORT

A premature infant exclusively nourished by parenteral nutrition developed enterobacteria sepsis. Ceftazidine was given initially but resistance led to the prescription of fluoroquinolone. Signs of intracranial hypertension developed 3 days after onset of fluoroquinolone treatment and regressed 48 hours after its withdrawal.

DISCUSSION

The main potential adverse effects with fluoroquinone in the newborn are arthropathy, photosensitivity, discoloration of the teeth and neurological disorders. Intracranial hypertension is a known complication of nalidixic acid both in adults and children, but to our knowledge has not been previously with floroquinolone in the newborn.

Antibiotic therapy and outcome of monomicrobial gram-negative bacteraemia: a 3-year population-based study

Within the 3-y period 1992-94 a total of 815 episodes of monomicrobial bacteraemia caused by Enterobacteriaceae not including Salmonella were registered in the County of Northern Jutland. The 30-d case fatality rate was 24%, ranging from 21% for Enterobacter spp. (n = 43), 22% for E. coli (n = 577) to 32% for both Klebsiella spp. (n = 138) and a group of miscellaneous enterobacteria (n = 57). In 16% of the bacteraemias, antibiotic treatment was not instituted before notification of positive blood cultures; in 9% empirical antibiotic treatment was inappropriate. Antibiotic regimens mainly included beta-lactams, ampicillin or mecillinam in combination with an aminoglycoside. The following factors were independently associated with case fatality: age > or = 75 y, high comorbidity index, admission to a medical ward or an intensive care unit, nosocomial acquisition, a source of infection outside the urinary tract or an undetermined focus, Klebsiella spp., inappropriate coverage or lack of antibiotic treatment before notification of positive blood culture. It is a matter of concern that in one-sixth of patients the physicians had not responded to the possibility of bacteraemia with institution of empirical antibiotic therapy.

[Enterobacter aerogenes pneumopathy treated by a cefepime-sulbactam-gentamicin combination]

BACKGROUND

Enterobacter aerogenes is the fifth most frequent pathogen causing nosocomial infections. Several strains have developed multiple resistance by over-production of a natural cephalosporinase and by the presence of wide-spectrum betalactamases.

CASE REPORT

A patient with chronic respiratory failure developed Enterobacter aerogenes pneumonia while under mechanical ventilation. The infection was successfully treated with a cefepime, sulbactam, gentamycin combination.

DISCUSSION

Choosing the optimum antibiotic therapy is a difficult task in many nosocomial infections. In certain cases, combining a betalactamase inhibitor with the appropriate antibiotic can improve bactericidal activity and provide successful cure.

The molecular and clinical epidemiology of enterobacteriaceae-producing extended-spectrum beta-lactamase in a tertiary care hospital

To describe the epidemiology of Enterobacteriaceae-producing extended-spectrum beta-lactamase (EP-ESBL) in a non-outbreak setting, and to define the risk factors associated with colonization, a 5-month surveillance study was initiated. Ten of 333 patients were colonized with EP-ESBL, as defined by isoelectric focusing. Klebsiella sp. and Escherichia coli were the species most commonly harbouring these plasmid-mediated enzymes. Of the 16 SHV-producing isolates, 10 were SHV-3-like (pI 7.0) and six were SHV-5-like (pI 8.2). All isolates were resistant to ceftriaxone. Ceftazidime resistance was detected in 50% and 100% of SHV-3-like and SHV-5-like producing isolates, respectively. One patient was colonized with four different SHV-5-like producing Enterobacteriaceae. These isolates carried plasmids that were indistinguishable by restriction endonuclease analysis, indicating broad plasmid transfer within the patient. By logistic regression, haemodialysis was a strong risk factor for colonization with EP-ESBL, suggesting that, in our hospital, horizontal transmission is an important mechanism of dissemination of these resistant pathogens.

Cefepime and amikacin synergy in vitro and in vivo against a ceftazidime-resistant strain of Enterobacter cloacae

The activities of cefepime and amikacin alone or in combination against an isogenic pair of Enterobacter cloacae strains (wild type and stably derepressed, ceftazidime-resistant mutant) were compared using an experimental model of pneumonia in non-leucopenic rats. Animals were infected by administering 8.4 log10 cfu of E. cloacae intratracheally, and therapy was initiated 12 h later. At that time, the animals' lungs showed bilateral pneumonia and contained more than 7 log10 E. cloacae cfu/g tissue. Because rats eliminate amikacin and cefepime much more rapidly than humans, renal impairment was induced in all animals to simulate the pharmacokinetic parameters of humans. In-vitro susceptibilities showed an inoculum effect with cefepime proportional to the bacterial titre against the two strains, but more pronounced with the stably derepressed mutant strain, whereas with bacterial concentrations of up to 7 log10 cfu/mL, no inoculum effect was observed with amikacin. In-vitro killing indicated that antibiotic combinations were synergic only at intermediate concentrations. At peak concentrations, the combination was merely as effective as amikacin alone. At trough concentrations, a non-significant trend towards the superiority of the combination over each antibiotic alone was noted. Moreover, cefepime was either bacteriostatic or permitted regrowth of the organisms in the range of antibiotic concentrations tested. Although each antibiotic alone failed to decrease bacterial counts in the lungs, regardless of the susceptibility of the strain used, the combination of both antibiotics was synergic and induced a significant decrease in the lung bacterial count 24 h after starting therapy when compared with tissue bacterial numbers in untreated animals or animals treated with either antibiotic alone. No resistant clones emerged during treatment with any of the antibiotic regimens studied.

Relationship between in vitro sensitivity of coliform pathogens in the udder and the outcome of treatment for clinical mastitis

The relationship between in vitro sensitivity to antimicrobials and the outcome of treatment was studied in 228 cows with coliform mastitis. All the cows were treated with a preparation containing sulphonamide and trimethoprim, and 197 of them were also treated with a non-steroidal anti-inflammatory drug (NSAID). The relationship between in vitro sensitivity to sulphonamide/trimethoprim and recovery was analysed by multivariate logistic regression. The possible confounding effects of treatment with an NSAID, days in lactation, parity, herd, and type of infecting organism were tested. Only treatment with an NSAID had a significant confounding effect and was included in the final statistical model. The recovery rate of the 165 cows infected by coliforms that were sensitive to sulphonamide/trimethoprim (89.1 per cent) was higher than that of the 63 cows infected by coliforms that were resistant to sulphonamide/trimethoprim (74.6 per cent). The odds ratio of recovery for the cases associated with organisms that were sensitive to sulphonamide/trimethoprim relative to the cases associated with organisms that were resistant to sulphonamide/trimethoprim was 2.75, with a 95 per cent confidence from 1.25 to 5.85. The odds ratio of recovery for the cases treated with an NSAID relative to the cases treated with sulphonamide/trimethoprim only was 2.76 with a 95 per cent confidence interval from 1.12 to 6.79.

Efficacy of parenteral administration of three antimicrobial agents in treatment of clinical mastitis in lactating cows: 487 cases (1989-1995)

OBJECTIVE

To evaluate the efficacy of parenteral administration of procaine penicillin G, spiramycin, or enrofloxacin in the treatment of clinical mastitis in lactating cows.

DESIGN

Noncontrolled, clinical retrospective study.

ANIMALS

487 cows with mastitis involving 543 quarters.

PROCEDURE

Clinical signs, histories, and results of bacteriologic examination, somatic cell count, and N-acetyl-beta-D-glucosaminidase activity of milk samples taken before and 3 to 4 weeks after treatment were retrieved from hospital records. Cows treated parenterally with procaine penicillin G, spiramycin, or enrofloxacin for 3 to 5 days were included. Supportive treatment alone was given to 35 cows infected with Escherichia coli. Factors possibly affecting outcome were analyzed, using ANOVA, correlation analyses, and the Mann-Whitney test. chi 2 Test was used to compare bacteriologic cure rates.

RESULTS

Bacteriologic cure rates for mastitis caused by Staphylococcus aureus, coagulase-negative staphylococci, and streptococci were 34, 76, and 65%, respectively. Cure rates in cows in their first lactation and infected with S aureus and coagulase-negative staphylococci were significantly higher than those for older cows. In cows with mastitis caused by E coli, the cure rate was 74% for those treated with penicillin G and 71% for those not treated with antimicrobials. High N-acetyl-beta-D-glucosaminidase activity in milk samples obtained at initial examination indicated a poor outcome in S aureus and streptococcal mastitis. Cows infected in the early lactation period had more severe inflammatory responses and clinical signs if infected with coagulase-negative staphylococci and coliforms.

CLINICAL IMPLICATIONS

3 to 5 days of treatment with parenterally administered penicillin G for clinical mastitis caused by penicillin-susceptible S aureus strains is efficacious in young cows. Parenteral administration of spiramycin or enrofloxacin does not give satisfactory results in mastitis caused by penicillin-resistant S aureus. Use of antimicrobials in the treatment of mastitis caused by coliform bacteria is questionable.