Enterobacter bacteremia: clinical features and emergence of antibiotic resistance during therapy

Microbiological efficacy and pharmacokinetics of prophylactic antibiotics in liver transplant patients

The pharmacokinetics of perioperative systemic antibiotics and the microbiological effectiveness of oral nonabsorbable antibiotics started immediately prior to surgery were studied in 18 adult patients undergoing liver transplantation. All patients received cefotaxime, 2 g intravenously, at 6-h intervals during surgery and then at 8-h intervals thereafter for 48 h; eight patients also received ampicillin at the same dose and schedule. This regimen produced levels of antibiotics in blood that appeared appropriate for prophylaxis. The first dose peak (68 +/- 18 micrograms/ml) and trough (6.9 +/- 4.7 micrograms/ml) levels of cefotaxime in serum and the first dose peak (73 +/- 22 micrograms/ml) and trough (4.1 +/- 2.3 micrograms/ml) levels of ampicillin in serum, which were assayed by high-performance liquid chromatography, were similar to levels reported in normal volunteers, despite mean intraoperative blood loss of 3.3 liters and fluid replacement of 21 liters. On postoperative days 1 and 2, the levels of cefotaxime and ampicillin were maintained at or above 0.9 and 1.3 micrograms/ml, respectively, with little accumulation. By random assignment, 8 patients received systemic antibiotics alone and 10 patients received systemic antibiotics plus a 3-week regimen of oral nonabsorbable antibiotics (gentamicin, polymyxin E, and nystatin) beginning when a donor liver was procured. Pre- and postoperative cultures of rectum, throat, and gastric aspirate samples showed persistence of aerobic gram-negative bacilli for the first 2 postoperative weeks in about half of the patients in each group. Failure of the regimen of oral nonabsorbable antibiotics to supplement cefotaxime in eradicating aerobic gram-negative bacilli from stools probably results from impaired peristalsis during and after surgery and warrants earlier initiation of the regimen.

Bacteremia in transplant recipients: a prospective study of demographics, etiologic agents, risk factors, and outcomes

BACKGROUND

Bacteremic infections are a major cause of death among organ transplant recipients. We sought to identify the risk factors associated with death and examine the timing of the bacteremic episode after operation to recognize patients who may benefit from perioperative prophylactic antibiotic therapy.

METHODS

A total of 125 episodes of bacteremia or fungemia in 16 heart, 26 kidney, and 70 liver recipients were monitored prospectively in 1 year.

RESULTS

The urinary tract was the most frequent portal for kidney recipients, the gastrointestinal and biliary tracts were frequent for liver recipients, and the lung was frequent in heart recipients. Heart and liver recipients were more severely ill at the time of bacteremia and had bacteremia sooner after operation. Death at 14 days after onset of bacteremia was 33% in heart recipients, 24% in liver recipients, and 11% in kidney recipients. Risk of death was associated with the severity of the underlying condition of the transplant recipient, the source of the bacteremia, and the microbial agent. Pseudomonas aeruginosa and Enterobacter species had fatality rates of 47% and 63%, respectively. P. aeruginosa and Enterobacter were also most commonly associated with failures of perioperative antibiotic prophylaxis.

CONCLUSIONS

There are distinct clinical patterns of bacteremia in transplant recipients. The emergence of P. aeruginosa and Enterobacter species in the immediate postoperative period appeared to be a significant cause of morbidity and death among transplant recipients.

Outbreak of ceftazidime resistance due to a novel extended-spectrum beta-lactamase in isolates from cancer patients

Ceftazidime is widely used in the therapy of infectious complications in neutropenic patients. We studied an outbreak of ceftazidime-resistant gram-negative bacillary infections in pediatric cancer patients receiving empirical ceftazidime therapy for neutropenic fever. Fourteen isolates (12 Klebsiella pneumoniae and 2 Escherichia coli) from 13 patients were studied. Specimens were obtained from multiple clinical sites including blood, urine, throat, and lung. The organisms were resistant to ceftazidime, aztreonam, and penicillins but remained susceptible to cephamycins and imipenem. All resistant isolates produced a novel beta-lactamase (TEM-26) with a pI of approximately 5.58, which was transferred by transformation to E. coli on a 7.9-kb nonconjugative plasmid which cotransferred resistance to trimethoprim-sulfamethoxazole. This enzyme readily hydrolyzed ceftazidime, aztreonam, and penicillins in a spectrophotometric assay. DNA sequencing data suggest that TEM-26 is derived from TEM-1.

The crisis in antibiotic resistance

The synthesis of large numbers of antibiotics over the past three decades has caused complacency about the threat of bacterial resistance. Bacteria have become resistant to antimicrobial agents as a result of chromosomal changes or the exchange of the exchange of genetic material via plasmids and transposons. Streptococcus pneumoniae, Streptococcus pyogenes, and staphylococci, organisms that cause respiratory and cutaneous infections, and members of the Enterobacteriaceae and Pseudomonas families, organisms that cause diarrhea, urinary infection, and sepsis, are now resistant to virtually all of the older antibiotics. The extensive use of antibiotics in the community and hospitals has fueled this crisis. Mechanisms such as antibiotic control programs, better hygiene, and synthesis of agents with improved antimicrobial activity need to be adopted in order to limit bacterial resistance.

Resistance to ciprofloxacin of respiratory pathogens in patients with cystic fibrosis

OBJECTIVE

To determine the incidence of resistance to ciprofloxacin in respiratory pathogens isolated from patients with cystic fibrosis (CF) compared with that of isolates from patients without CF. The hypothesis was that repeated exposure of these respiratory pathogens to ciprofloxacin would reduce their sensitivity.

DESIGN

Isolates of Pseudomonas aeruginosa and Staphylococcus aureus were obtained prospectively from sputa of patients with CF, as part of their routine care. The sensitivities of these isolates to ciprofloxacin were determined by standard agar dilution techniques.

SETTING AND PATIENTS

The study was carried out in patients who attended the outpatient clinic or were treated as inpatients of a tertiary referral hospital. Sputa were obtained from 71 patients with CF (age range, 2-31 years) and isolates of P. aeruginosa and S. aureus were compared with those from 54 hospital patients who did not have CF.

OUTCOME MEASURES

Sensitivities to ciprofloxacin, expressed as the minimal concentrations required to inhibit growth of the organisms (MIC), were used to make comparisons between different isolates and the same isolates within patients at different times.

RESULTS

A higher incidence of ciprofloxacin resistance was displayed by isolates of P. aeruginosa from CF patients who had been previously prescribed ciprofloxacin (MIC50 of 2.0 mg/L and 4.0 mg/L for mucoid and non-mucoid strains respectively). The MIC of individual organisms tended to rise after a course of ciprofloxacin had been given to their host. A much lower incidence of resistance was displayed by isolates of P. aeruginosa from patients without CF (MIC50, 0.25 mg/L). Similarly, S. aureus isolates from patients with CF exhibited greater resistance to ciprofloxacin (MIC50, 32 mg/L) than isolates from other patients (MIC50, 0.75 mg/L).

CONCLUSION

The resistance of P. aeruginosa appears to be related to ciprofloxacin exposure, so further development of resistance may be diminished by restricting the frequency of ciprofloxacin administration to individual patients.