The gyrA gene mutations associated with quinolone resistance were determined in 21 epidemiologically unrelated clinical isolates of Acinetobacter baumannii. Our studies highlight the conserved sequences in the quinolone resistance-determining region of the gyrA gene from A. baumannii and other bacteria. All 15 isolates for which the MIC of ciprofloxacin is Ն4 g/ml showed a change at Ser-83 to Leu. Six strains for which the MIC of ciprofloxacin is 1 g/ml did not show any change at Ser-83, although a strain for which the MIC of ciprofloxacin is 1 g/ml exhibited a change at Gly-81 to Val. Although it is possible that mutations in other locations of the gyrA gene, the gyrB gene, or in other genes may also contribute to the modulation of the MIC level, our results suggest that a gyrA mutation at Ser-83 is associated with quinolone resistance in A. baumannii.

Antimicrobial susceptibility testing was performed on 54 epidemiologically unrelated clinical isolates of Acinetobacter baumnannii by using a standard agar dilution technique. On the basis of the in vitro activities, imipenem and doxycycline were the most active agents, whereas amikacin, isepamicin, and the new fluorquinolones ciprofloxacin and ofloxacin presented moderate activity. Cephalosporinase activity was found in 98% of the strains, whereas lactamases of TEM type 1 and one with a pI of 7 to 7.5 were present in 16 and 11% of the strains, respectively. Resistance to aminoglycosides was explained by the production of the three classes of aminoglycoside-modifying enzymes, with predominance of aminoglycoside-3'-phosphotransferase VI

No abstract

Summary. Arbitrarily primed polymerase chain reaction (AP-PCR) and ribotyping were compared in an investigation of an outbreak of Acinetobacter baumannii infections. Twentyfive clinical isolates shown previously by other criteria to belong to two different groups, and nine randomly selected A . baumannii clinical isolates from other hospitals were investigated. Among the strains analysed, nine different EcoRI rRNA gene restriction pattern fingerprints were observed. While similarity was detected between strains of the same group, these fingerprints differed clearly between the two A . baumannii groups defined in the outbreak. Two of the nine strains selected randomly had the same ribotype as those strains involved in the outbreak, whereas the remaining seven strains each had a different ribotype. When the strains were tested by AP-PCR with 0.25, 0-5 or 1 ,UM of M13 forward primer, 10 different profiles were obtained. However, 11 profiles were observed if two different primer concentrations (0-25 and 1 p~) were used. It was concluded that ribotyping and AP-PCR exhibited a similar discriminatory power, although AP-PCR had the additional advantages of speed and simplicity.

Summary:Current guidelines for the treatment of catheter-related bacteraemia (CRB) advise against central venous catheter (CVC) exchange because of the potential risk of prolonging infection. However, there are no consistent data proving this recommendation. We evaluated prospectively the usefulness of CVC exchange by guidewire for the treatment of CRB in patients undergoing BMT or intensive chemotherapy. CVC exchange was considered when fever and positive blood cultures persisted after 2 days of adequate antimicrobial therapy and no potential source of bacteraemia other than CVC could be identified. The guidewire exchange was preceded and followed by a slow infusion of adequate antimicrobial therapy. Bacteraemia was confirmed as catheter-related by demonstrating concordance between isolates from the tip and blood cultures by pulsed-field electrophoresis of genomic DNA. This procedure was performed in 19 episodes of bacteraemia during a 1-year period. Fourteen episodes (74%) were catheter-related and 71% of these were due to coagulase-negative staphylococci. Guidewire replacement was accomplished uneventfully 4 days after development of sepsis (range 3-6). In all cases, clinical signs of sepsis disappeared in less than 24 h after replacement. Definitive catheter withdrawal was carried out a median of 16 days (range 3-42) after guidewire exchange; in all cases, the tip culture was negative. We conclude that CVC replacement by guidewire under adequate antimicrobial therapy may be a reasonable option for the treatment of CRB when antimicrobial therapy alone has been unsuccessful. Keywords: catheter-related bacteraemia; infections treatment; catheter exchange Bacteraemia is the most frequent life-threatening complication of central venous catheters (CVC). 1 Catheter removal is usually required for the diagnosis and the treatment of catheter-related bacteraemia (CRB). Nevertheless, the catheter may not be the source of infection in as many as three out of four suspected cases of CRB. 2 CVC exchange by guidewire is currently accepted in the management of suspected CRB, although the catheter should be relocated to a new site if the tip culture confirms the diagnosis of CRB. [3][4][5][6] This recomendation is based on several studies 7-9 reporting anecdotal cases of immediate tip contamination of the guidewire-inserted catheter. However, in BMT patients and other high-risk patients with thrombocytopenia, this policy constitutes a potential risk for haemorrhage. We hypothesized that, as it occurs in replacement surgery of infected prosthetic devices, adherence of microorganisms and subsequent biofilm formation on the CVC exchanged by guidewire would be unlikely if a high concentration of an appropriate antibiotic were present on the surface of the catheter at the time or shortly after the arrival of the pathogen and were maintained for a critical span of time.To evaluate the safety and efficacy of CVC exchange by guidewire after unsuccesful antimicrobial therapy in patients undergoing BMT or intensive chemotherapy with a...