Infective endocarditis caused by an unusual gram-negative rod, Rahnella aquatilis

An 11-month-old girl with congenital heart disease developed infective endocarditis. Blood cultures revealed an unusual gram-negative rod, Rahnella aquatilis. The patient was successfully treated with a combination of netilmicin and ceftazidime. This is the first case report of infective endocarditis caused by this organism. R. aquatilis should be recognized as a clinical pathogen capable of causing life-threatening infection in children and adults.

Liver biopsy in liver transplantation: no additional risk of infections in patients with choledochojejunostomy

BACKGROUND/AIMS

This study aimed to determine whether there is an increased infectious risk following liver biopsy in liver transplant patients with choledochojejunostomy.

METHODS

We evaluated the incidence of liver-biopsy-related sepsis in a consecutive series of 27 patients who underwent choledochojejunostomy, either during the transplant procedure (17 patients) or later following biliary complications (10 patients). We evaluated another 138 patients as a control group who had orthotopic liver transplantation during the same period and underwent duct-to-duct anastomosis. All liver biopsies had routine, prior ultrasound evaluation to detect dilated biliary ducts.

RESULTS

In the 27 patients who underwent choledochojejunostomy, 96 liver biopsies were performed: the sepsis rate was 3.12% per biopsy (n = 96) or 7.4% per patient (n = 27). However, despite a normal ultrasound, subsequent ERCP demonstrated biliary obstruction in one patient. Thus the rate of sepsis was 2.1% per biopsy or 3.7 per patient. In the control group 338 liver biopsies were performed: the sepsis rate was 1.5% per biopsy (n = 338) or 2.9% per patient (n = 138). The difference was not significant. All septic episodes had positive blood cultures for a single enteric microorganism, and all responded to antibiotics

CONCLUSIONS

Our data do not suggest that liver-transplanted patients with choledochojejunostomy are more at risk of sepsis following liver biopsy, providing there is no "occult" biliary obstruction; therefore, they do not require prophylactic antibiotics as has been suggested by other authors.

A hospital outbreak of high-level beta-lactam-resistant Enterobacter spp.: association more with ampicillin and cephalosporin therapy than with nosocomial transmission

We studied an 8 month outbreak of a 7-fold increased isolation rate of high-level beta-lactam-resistant Enterobacter spp. from clinical infections (20 patients, 22 isolates: 20 E. cloacae, 2 E. aerogenes). In a case-control analysis the occurrence of resistant Enterobacter spp. was found to be associated with treatment with multiple antibiotics (p = 0.03), broad-spectrum beta-lactam agents (p = 0.0001) including ampicillin (p = 0.04), and cephalosporins (cefuroxime and cefotaxime, p = 0.004). Biochemical fingerprinting and pulsed-field gel electrophoresis (PFGE) typing showed no identity between the resistant isolates, indicating that neither cross-infection nor nosocomial transmission from a common source was the immediate cause of the problem. The outbreak was not paralleled by the overall Enterobacter spp. isolation rate or the antibiotic usage pattern in the hospital. Thus, the underlying cause of the outbreak remained obscure.

The relationship between antecedent antibiotic use and resistance to extended-spectrum cephalosporins in group I beta-lactamase-producing organisms

Gram-negative pathogens are increasingly resistant to extended-spectrum cephalosporins (ESCs). Using a prospective, case-controlled observational study, we examined the prevalence and the risk factors for development of resistance to ESCs in group I beta-lactamase-producing organisms. Of the 386 isolates of Enterobacter species, Pseudomonas aeruginosa, Citrobacter species, and Serratia marsescens from 340 consecutive patients, 70 (18.1%) were resistant to ESCs; the highest rates of resistance were found among Citrobacter freundii (40.9%), Enterobacter cloacae (31.1%), and Enterobacter aerogenes isolates (18.9%). Patients' prior antibiotic use and the mean number of antibiotics used were significantly greater in association with resistant vs. susceptible isolates. Resistance was associated with prior use of ceftizoxime or cefotaxime (P = .008), ceftazidime (P = .004), and piperacillin (P = .001). Other antibiotics were not associated with resistance. Resistance was less frequent in patients receiving ESCs and an aminoglycoside. We conclude that prior use of ESCs is associated with the isolation of resistant group I beta-lactamase-producing organisms. Concomitant use of an aminoglycoside may decrease this risk.

Vertical transmission of Citrobacter diversus documented by DNA fingerprinting

OBJECTIVE

To confirm the vertical transmission of Citrobacter diversus from a mother to her infant and to evaluate the epidemiologic usefulness of a new automated procedure for analysis of polymerase chain reaction (PCR)-generated DNA fingerprints.

DESIGN

Repetitive element-based PCR (rep-PCR) analysis of C diversus isolates from the blood and amniotic fluid of a mother and the blood of her infant was performed. Unrelated C diversus isolates also were characterized and compared with the isolates from mother and infant. DNA fingerprints were generated by gel electrophoresis of PCR products derived from either unlabeled standard repetitive sequence-based oligonucleotide primers or fluorescent primers. The standard rep-PCR fingerprints were analyzed by visual inspection. The fluorescent primers were used in fluorophore-enhanced rep-PCR (FERP), and the FERP DNA fingerprints were analyzed by an Applied BioSystems (ABI) Model 373A laser scanning unit equipped with Genescan 672 software (Applied Biosystems, Inc, Foster City, CA).

SETTING AND PATIENTS

A mother and her newborn infant, both with invasive disease due to C diversus, in an urban tertiary-care hospital.

RESULTS

The DNA fingerprints of the maternal blood, amniotic fluid, and infant blood isolates of C diversus were identical by both visual inspection of ethidium bromide-stained agarose gels and computer-aided analysis of FERP patterns. These strains appeared to differ from all but one control isolate, which had been collected 7 years earlier in the same city in which the infant was born.

CONCLUSIONS

Vertical transmission of C diversus from mother to infant can occur in utero. Automated analysis of rep-PCR-generated DNA fingerprints derived using fluorescent primers is an objective means for comparing isolates of C diversus and in all likelihood would be useful for other species of bacteria that possess repetitive elements.

Effects of tazobactam on the frequency of the emergence of resistant strains from Enterobacter cloacae, Citrobacter freundii, and Proteus vulgaris (beta-lactamase derepressed mutants)

When Enterobacter cloacae, Citrobacter freundii, and Proteus vulgaris were treated with piperacillin (PIPC) in combination with tazobactam (TAZ), the in vitro frequency of emergence of resistant strains (beta-lactamase producing mutants) was lower than with PIPC or ceftazidime (CAZ) treated bacteria. In a mouse intraperitoneal infection model caused by E. cloacae, beta-lactamase derepressed mutants were detected following therapy with PIPC or CAZ, although no derepressed mutants were detected after treatment with PIPC in combination with TAZ. This suppression of the selection of derepressed mutants, which produce large amounts of beta-lactamases, by the combination of TAZ and PIPC suggests that the combination delays the increase of resistant mutants compared with PIPC alone.

Enterococcal nosocomial infection: epidemiology and practice

Caring for patients susceptible to enterococcal infections is a part of practice for nurses working in today's hospital units. While enterococci are not particularly virulent organisms, they are well suited to causing infection in hospitalized patients, especially in the very old, the seriously ill, and the immunosuppressed. Despite increased understanding of the clinical threat posed by multiresistant strains of enterococci, the incidence of nosocomial enterococcal infection is growing. In this article the author examines the epidemiology and risk factors for colonization and infection with enterococcal bacteria and provides a brief review of antibiotic sensitivities for the organisms. A case study illustrates the course and consequence of infection with multiresistant enterococcus for the seriously ill patient. The importance of education of health professionals in prevention and control of enterococcal infection and superinfection is discussed.

Bactericidal killing activities of cefepime, ceftazidime, cefotaxime, and ceftriaxone against Staphylococcus aureus and beta-lactamase-producing strains of Enterobacter aerogenes and Klebsiella pneumoniae in an in vitro infection model

Cefepime (CP) is a new injectable cephalosporin with a broad spectrum of activity and stability against common chromosomally and plasmid-mediated beta-lactamases. The bactericidal activities of CP, ceftazidime (CZ), cefotaxime (CTX), and ceftriaxone (CAX) against reference and clinical strains of Staphylococcus aureus, an isogenic pair of Enterobacter aerogenes strains (wild type and a CZ-resistant derepressed mutant), and a Klebsiella pneumoniae isolate possessing a TEM-10 beta-lactamase were investigated in a two-compartment pharmacodynamic in vitro infection model which simulates human pharmacokinetics. An inoculum of approximately 10(6) CFU/ml was used in all model experiments. Antibiotics were administered to simulate the following regimens: CP at 2 g every 12 h (q12h), CZ at 2 g q8h, CTX at 2 g q8h, and CAX at 2 g q24h. Human albumin was added during experiments with CAX and staphylococci to simulate protein binding. Samples were removed at multiple time points over a 48-h period to determine the inoculum size for time-kill curves. Development of resistance was detected by inoculating samples obtained at 0, 24, and 48 h onto antibiotic-containing agar plates. The time to 99.9% killing was used to compare drug regimens. Against staphylococci, the time to bacterial eradication was significantly delayed with CAX-albumin. All regimens had similar activities against the wild-type Enterobacter strain; however, regrowth was noted with CZ, CTX, and CAX against the CZ-resistant strain. There were no differences between the CP, CTX, and CAX regimens against K. pneumoniae. Of interest, no regrowth of any organism was noted with CP. These data indicate that CP has activity against S.aureus and CZ-resistant gram-negative bacilli.

Effect of selective bowel decontamination with norfloxacin on spontaneous bacterial peritonitis, translocation, and survival in an animal model of cirrhosis

Selective bowel decontamination with the orally administered quinolone antibiotic, norfloxacin, has been shown to suppress gut gram-negative bacteria and help prevent gram-negative infections in cirrhotic patients who are at high risk of bacterial infection. Because this drug does not eradicate gram-positive organisms, it is conceivable that gram-positives could replace the suppressed gram-negatives in the gut and lead to subsequent infection. Also the effect of norfloxacin on translocation (as defined by culture positivity of mesenteric lymph nodes) has received little attention. In this study, the effect of oral norfloxacin on translocation, bacterial peritonitis, and survival was investigated in an animal model of carbon tetrachloride-induced cirrhosis and ascites. Treated rats received daily doses of orally administered norfloxacin from the onset of cirrhosis until they died or were killed. Controls received no antibiotic. Norfloxacin led to a reduction in bacterial peritonitis from 70% in untreated cirrhotic controls to 28% in treated cirrhotic rats; these data were statistically significant (P = .012). There was no effect on overall translocation rate (28% with norfloxacin vs. 50% without norfloxacin) (P > .1). Gram-positives were isolated in 100% of the bacterial peritonitis episodes and in 71.4% of culture-positive mesenteric lymph nodes in treated animals compared with only 25% of peritonitis episodes and 10% of culture-positive mesenteric lymph nodes of untreated cirrhotic controls (P < .01 for peritonitis and P < .05 for translocation). The survival rate was not different between groups (P > .1).(ABSTRACT TRUNCATED AT 250 WORDS)

Psoas abscess following ileo-anal pouch surgery

An unusual case of psoas abscess complicating one of the earliest performed ileo-anal pouch anastomoses is reported. The authors have been unable to find a similar previously published case.

Antibiotic availability and multiresistant coliforms in a rural Ugandan hospital

Twenty-seven strains of coliforms (Enterobacteriaceae) isolated at Kisiizi Hospital, Uganda, were tested for their sensitivity to antibiotics. Sixteen of the 18 patient strains were identified as Escherichia coli, but biochemical analysis, serotyping, plasmid profile and antibiogram showed them to be heterogeneous. Resistance was very common to the antibiotics available in the community (ampicillin, chloramphenicol, tetracycline and trimethoprim), but was much less frequent for the agents used only in the hospital (gentamicin, ciprofloxacin and nitrofurantoin). A correlation was noted between the presence of large plasmids (150 kb or larger) and resistance to amoxicillin in patient strains of E. coli. The nine strains of coliform from the water supply were more heterogeneous and less resistant. The availability of antibiotics in the community seems linked to the development of multiresistant coliforms, which in a Ugandan context are very difficult to treat, and even more difficult to prevent.

Bacteraemia caused by Rahnella aquatilis: report of two cases and review

Rahnella aquatilis, a rare Gram-negative rod, usually found in fresh water, was isolated from blood of a diabetic patient and a patient with laryngeal carcinoma. Both recovered from the infection after treatment with parenteral antibiotics including gentamicin.

Enterobacter cloacae in a neonatal intensive care unit: account of an outbreak and its relationship to use of third generation cephalosporins

After uneventful use of cefotaxime and ceftazidime as first line therapy for three years in our neonatal intensive care unit we isolated cephalosporin-resistant Enterobacter cloacae (CREC) strains which caused clusters of cases or colonization and/or serious neonatal infection. By using two or more typing methods, at least five different strains with similar patterns of antimicrobial sensitivities were identified. The results of a case-control study did not support the notion that the use of third generation cephalosporins was associated with colonization and infection by CREC. The outbreak was brought under control by interrupting the transmission of the epidemic strain D, by measures such as cohort nursing, diligent handwashing before and after procedures, and thorough environmental cleaning as well as by decontamination with glutaraldehyde after dismantling of the blood gas analyser believed to have acted as a persistent reservoir. Our experience highlights the danger of inadequate supervision and maintenance of equipment used for near-patient testing and the need to monitor such equipment not only in terms of its calibration and analytical performance but also microbiologically.

Development of resistance by Enterobacter cloacae during therapy of pulmonary infections in intensive care patients

The emergence of resistance during therapy and the efficacy of different antibiotic therapy regimens were studied in 38 intensive care patients suffering from pulmonary infections caused by Enterobacter cloacae. Every three days a fresh isolate was obtained from each patient and tested in vitro for susceptibility to 16 antibiotics by determination of the minimal inhibitory concentrations. During therapy with cefotaxime and tobramycin the E. cloacae strains from 47% of the patients became resistant to cefotaxime within 6 days. In all cases resistance encompassed all other broad-spectrum penicillins and cephalosporins tested, as well as aztreonam. Development of resistance regularly led to persistence of bacteria. Resistance to tobramycin, ciprofloxacin or imipenem was not observed. Treatment of 25 patients with persisting E. cloacae infections was successful in 17 out of 18 patients treated with imipenem and in 6 out of 7 patients receiving ciprofloxacin.

Multiple antibiotic resistance in Klebsiella spp. and other Enterobacteriaceae isolated in Singapore

A common pattern of multiple antibiotic resistance has been noted in bacteria isolated from Singaporean patients. The resistance pattern includes: ampicillin, cefuroxime, ceftazidime and other third generation cephalosporins, aztreonam, gentamicin and other aminoglycosides. The bacterial species implicated are Klebsiellas and other members of the Enterobacteriaceae. Preliminary laboratory investigation with a disk-diffusion augmentation test suggests the presence of extended-spectrum beta-lactamases. A retrospective study of laboratory blood culture records shows a rising incidence of resistance in Klebsiella spp. since 1985. Antimicrobial susceptibility results suggest a high degree of co-transfer of aminoglycoside resistance. The high frequency of this type of multiple antibiotic resistance should result in greater caution in the selection of presumptive antibiotic therapy for septicaemia, in order to avoid treatment failure and further selection of resistant strains.

[A case of severe pneumonia in an elderly man, caused by Citrobacter freundii suspected to have a low susceptibility to imipenem/cilastatin sodium]

An 80-year-old blind man with lepromatous leprosy suffered from right femoral neck and humeral neck fractures on July 9, 1993. Because of fever (38.6 degrees C), difficult expectoration and diffuse bilateral perihilar infiltrates with consolidation in the left lower lung field on his chest radiograph, severe pneumonia was diagnosed. With intravenous hyperalimentation, imipenem/cilastatin (IPM/CS), ceftazidime, minocycline, gentamicin (GM), and human immunoglobulin were administrated. On July 29, hip screw-plate fixation was done. Citrobacter freundii was isolated from the sputum and its susceptibility was IPM/CS+, GM3+. Multi-drug therapy with GM and other antibiotics improved the patients' condition, but Citrobacter freundii were still detected and 43 days of medication were needed. According to a report by the Ministry of Health and Welfare in 1992, the resistance rate of IPM/CS against Citrobacter freundii is only 0.7%, and IPM/CS is more effective than beta-Lactams. This is a very rare case of severe pneumonia in an elderly patient caused by Citrobacter freundii that was suspected to have low susceptibility to IPM/CS.

Bifocal cervical spondylodiscitis due to Citrobacter diversus

Spondylodiscitis due to Citrobacter diversus is rare. An unusual case of bifocal cervical spondylodiscitis following transurethral prostatectomy is reported. C. diversus was detected by urinary cultures and locally by intervertebral disc puncture. Satisfactory recovery occurred after treatment with imipenem and amikacin, and then imipenem alone. Citrobacter infections are still rare in adults but are increasing in immunocompromised patients and sometimes occur in healthy subjects following surgery.

[Basic and clinical studies of fleroxacin on infectious enteritis. Research Group of AM-833 on infectious enteritis]

A clinical study was conducted on fleroxacin (FLRX) in 143 patients and carriers with infectious enteritis (shigellosis, Salmonella enteritis, Campylobacter enteritis, pathogenic Escherichia coli enteritis, Vibrio parahaemolyticus enteritis, cholera, multiple bacterial infections, pathogen-negative enteritis). Furthermore, its antibacterial activity against clinical isolates, fecal concentration and effect on fecal microflora were conducted. FLRX was administered orally in doses of 200 mg once a day (200 mg group) or 300 mg once a day (300 mg group) for 3 days to cholera, for 7 days to Salmonella enteritis and for 5 days to the other infectious enteritis. The clinical efficacy rates were 100% in both the 200 mg and 300 mg groups. The bacteriological efficacy rates were 100% against Shigella spp., Salmonella spp., pathogenic E. coli, V. parahaemolyticus and V. cholerae O1, and 63.6% against Campylobacter spp. in the 200 mg group. The rates of the 300 mg group were 93.3% against Shigella spp., and 100% against Campylobacter spp. and pathogenic E. coli. As adverse effects, skin rash was observed in 1 case each in both groups (1.1%, 2.1%). Abnormal laboratory findings consisted of 1 case of increased eosinophils and 1 case of elevated GOT and GPT levels in the 200 mg group (2.8%), and 1 case of elevated GPT in the 300 mg group (2.9%). The clinical usefulness rates were 92.9% and 93.3% in the 200 mg and 300 mg groups, respectively. Antibacterial activity was somewhat inferior to that fo ciprofloxacin and equal to or better than that of norfloxacin, demonstrating MIC90 values against Shigella spp., Salmonella spp., pathogenic E. coli, V. parahaemolyticus and Campylobacter spp. of 0.1, 0.2, 0.1, 0.2 and 0.78 micrograms/ml, respectively. Peak fecal concentrations of the drug were 49.0 micrograms/g and 274.4 micrograms/g in the 200 mg group, and 43.3 micrograms/g and below the detection limit (5.0 micrograms/g) in the 300 mg group. With respect to fecal microflora (4 cases), a decrease in Enterobacteriaceae was observed in 3 cases during dosing. But this change showed a tendency to recover after completion of dosing. No effects were observed on anaerobic bacteria.

[Gentamycin resistant Enterobacteriaceae at a neonatal care unit]

A case of septicaemia in a seven-day-old infant with a gentamicin-resistant strain of Enterobacter cloacae prompted an epidemiological survey in a neonatal unit. Another 18 patients harboured gentamicin-resistant Enterobacteriaceae without symptoms. Control of the outbreak was achieved by cohort nursing, strict hygiene and reduction of aminoglycoside consumption by 50%. Efficiency of the measures was monitored by weekly faecal samples from all patients. All strains produced the aminoglycoside modifying enzyme AAC(3)II. The resistance was plasmid-mediated.

Increasing Enterobacter bacteremia in pediatric patients

Thirty-two episodes of Enterobacter bacteremia were identified in 30 patients at Children's Hospital of Michigan between September, 1989, and November, 1992. Fifty-six percent of the episodes were nosocomial. Enterobacter accounted for 14% of all nosocomial bacteremias and was the most common Gram-negative organism causing such infections. Enterobacter cloacae was the most commonly isolated species (72%). Twenty-nine (97%) patients had underlying risk factors for infection, including central venous catheters in 22. The susceptibility pattern of 46 Enterobacter isolates from blood during the same study period showed high resistance to extended spectrum penicillins and third generation cephalosporins but low resistance to aminoglycosides and trimethoprim-sulfamethoxazole (TMP/SMX). Resistance to third generation cephalosporins increased throughout the study period and was higher in patients who had received these agents during the previous month. In situations where there is a high frequency of Gram-negative bacteremias with organisms resistant to third generation cephalosporins, we suggest that initial therapy be a combination of a beta-lactam agent and an aminoglycoside or TMP/SMX.

Consecutive mutations leading to the emergence in vivo of imipenem resistance in a clinical strain of Enterobacter aerogenes

Three consecutive isolates of Enterobacter aerogenes were obtained from the blood cultures of a hospitalised patient who was receiving antibiotic therapy. The initial isolate possessed an inducible cephalosporinase and was susceptible to third-generation cephalosporins. After ceftazidime treatment, a second isolate resistant to this antibiotic and characterised by stable overproduction of the chromosomal beta-lactamase was obtained, and therapy was altered to a new combination which included imipenem. During this course of treatment, a strain of E. aerogenes was isolated that was resistant to virtually all beta-lactam agents including imipenem. Comparison of biotypes and ribotyping profiles indicated that the three isolates were probably derived from a single strain which had undergone several mutations during antibiotic exposure. Examination of outer-membrane protein (OMP) preparations and lipopolysaccharide (LPS) profiles showed that the imipenem-resistant isolate lacked a major OMP and high molecular mass LPS. Furthermore, this isolate displayed reduced permeability to cephaloridine compared with the initial isolate. The introduction of a plasmid carrying a wild-type ampD allele prevented cephalosporinase production and restored beta-lactam susceptibility in the imipenem-resistant isolate. It was concluded that stable derepression of class-I beta-lactamase production and reduced permeability are both required for expression of imipenem resistance in E. aerogenes, and that previous exposure to cephalosporins may encourage the emergence of such strains.