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[Investigation of serum resistance for Pseudomonas aeruginosa and Acinetobacter baumannii strains].

Serum resistance is one of the major virulence factors of Gram negative bacteria. The aim of this study was to investigate the serum resistance of Pseudomonas aeruginosa and Acinetobacter baumannii strains isolated from various clinical samples (19 tracheal aspirates, 14 urine, 7 sputum, 7 wound and one peritoneal fluid specimens). Forty-eight P. aeuginosa and 48 A. baumannii strains were tested for human serum bactericidal effect by using Benge's method. Thirty-five (72.9%), 9 (18.7%), and 4 (8.3%) of P. aeruginosa strains were found to be resistant, intermediate sensitive and sensitive to serum, respectively. These rates were detected as 81.2% (39/48), 14.5% (7/48), and 4.1% (2/48) for A. baumannii strains, respectively. It can be concluded that, high serum resistance rates of P. aeruginosa and A. baumannii isolates might have an important role in the pathogenesis of infections of these bacteria.

Acinetobacter Infections↗

Predictive biomarkers for drug-resistant Acinetobacter baumannii isolates with bla(TEM-1), AmpC-type bla and integrase 1 genotypes.

BACKGROUND AND PURPOSE: We tested whether antibiotic susceptibilities of drug-resistant Acinetobacter baumannii isolates could be used to predict the clinically important genotypes bla(TEM-1), AmpC-type bla, and integrase 1 gene (IntI1). METHODS: We analyzed 401 A. baumannii isolates obtained at Changhua Christian Hospital between April 2001 and March 2002. The isolates were all from blood cultures, and identification of A. baumannii was confirmed by API-20NE. Antibiotic susceptibility testing (phenotype) was performed by disk diffusion method. Polymerase chain reaction was used to detect the genes bla(TEM-1), AmpC-type bla and IntI1. RESULTS: Of 32 A. baumannii isolates, 10 possessed bla(TEM-1), 21 AmpC-type bla, and 26 IntI1. Resistance to ceftazidime (CAZ) predicted bla(TEM-1) genotype with 63.6% sensitivity, 100% specificity, 55.6% positive predictive value (PPV) and 0% negative predictive value (NPV). Trimethoprim-sulfamethoxazole (SXT) and gentamicin (GM) resistance predicted IntI1 genotype with 83.3% sensitivity, 71.4% specificity, 95.2% PPV and 45.4% NPV. No resistance phenotype could predict the AmpC-type bla genotype. CONCLUSIONS: CAZ resistance predicted the bla(TEM-1) genotype with 100% specificity, and SXT and GM resistance predicted the IntI1 genotype with 92.5% PPV. Therefore, antibiotic susceptibilities to CAZ, SXT, and GM can be utilized clinically to detect critical genotypes in A. baumannii.

Acinetobacter Infections↗

Colistin, meropenem and rifampin in a combination therapy for multi-drug-resistant Acinetobacter baumannii multifocal infection. A case report.

A 16 year-old girl underwent a multifocal (lungs, skin, soft tissues) infection due to multiresistant Acinetobacter baumannii after a car crash. To treat such a severe disease we used a combination therapy of colistin (2 millions Units twice/day), rifampicin (600 mg/day), meropenem (1 g 3 times a day) after a synergistic activity test was performed (checkerboard method on Mueller-Hinton broth and 5x10(5) cfu/mL inoculum). After 24 days, when a significant clinical improvement was gained, the 3-drugs combination therapy was replaced with i.v. levofloxacin 500 mg twice/day but, after 10 days of quinolones therapy, fever started again and the same multidrug resistant (MDR) A. baumannii was isolated from the skin grafts, central venous catheter tip and bronchial alveolar lavage. A combination therapy with colistin and meropenem was therefore started and definitive defervescence was obtained after 10 days. This therapy was continued for 70 days even if the patient was apyretic because A. baumannii was still present in the skin secretions. After 109 days of hospitalization in our intensive care unit, the patient was transferred to a rehabilitative unit. This case shows how useful is, in selected cases, rediscovering old antibiotic drugs, specially when they are adopted as a combination therapy, and highlights the importance of the clinical microbiological laboratory as it may help clinicians in choosing the best drugs combination.

Accidents, Traffic↗

Concerning the sensitivity of Acinetobacter calcoaceticus.

The strains of Acinetobacter calcoaceticus, var. anitratus (A. c. a.) were isolated in the nosocomial environment as an opportune pathogen. The therapy of choice may be determined after in vitro tests. Our results show following therapeutical possibilities: beta-lactam antibiotics--cephalosporins of IIIrd generation (cefotaxime), also combinations of antimicrobials have shown good results: amoxycillin or ticarcillin with clavulanic acid. Best synergistic effect was found in combination ticarcillin-amikacin.

Acinetobacter↗

Antimicrobial susceptibility of Acinetobacter strains identified by DNA-DNA hybridization.

The in vitro activity of 21 antimicrobial agents against 143 Acinetobacter strains (belonging to 12 different DNA hybridization groups) was studied. Of the antibiotics tested, ciprofloxacin, ofloxacin, doxycycline and imipenem had the lowest MICs. For most antibiotics there was a considerable overlap of the MICs between the DNA groups; however, some differences in antimicrobial susceptibility between DNA groups were found. Strains of DNA groups 2 (A. baumannii) and 13 (unnamed) were most resistant, and strains of DNA groups 8 (A. lwoffii) and 5 (A. junii) less resistant. Many DNA groups contain both saccharolytic and non-saccharolytic strains but in the present study no differences in antimicrobial susceptibility were found between strains of a particular DNA group with regard to this property.

Acinetobacter↗

Antibiogram, biotyping and plasmid profile analysis of Acinetobacter calcoaceticus var. anitratus.

Antibiogram, biotyping, and plasmid profile analysis were studied on 115 isolates (40 nosocomial and 75 community strains) of Acinetobacter calcoaceticus var. anitratus isolated from clinical specimens. By disk diffusion method, we found 14 antimicrobial susceptibility patterns. Among them, the gentamicin-resistant patterns were recovered more frequently from nosocomial origin than from community-acquired origin. Fifteen patterns of biocodes were found by using GNI card of AutoMicrobic System (Vitek System). By using rapid alkaline extraction method and agarose gel electrophoresis, 102 isolates (88.7%) contained plasmids, and 72 distinct profiles were found. No particular plasmid profile correlates with specific antibiogram or biotype. However, multiple isolates with identical antibiogram and biotype recovered from the same patient were usually of identical plasmid profile. In view of the heterogeneity of the plasmid patterns that were found, the combined use of antibiogram, biotyping, and plasmid profile analysis could be satisfactory for epidemiological investigation.

Acinetobacter↗

[Phenotypes of resistance to antibiotics of Acinetobacter baumannii. Impact on therapeutic orientation].

By studying the sensitivity to antibiotics of 74 Acinetobacter baumannii strains, four phenotype groups were distinguished. The resistance of one of them (11% of the strains) to imipenem, argues against the therapeutic attitudes that now prevail. From studies on the kinetics of bactericidal activity of antibiotics and there association we propose what should be done in the laboratory to provide help to the physician for the antibiotic choice.

Acinetobacter↗

Room humidifiers as the source of Acinetobacter infections.

Twenty-four patients contracted systemic infections with Acinetobacter calcoaceticus during a four-month period. Unheated room humidifiers at the patients' bedsides were implicated as the source of infection in six. The outbreak was terminated with the removal of the humidifers.

Acinetobacter↗

Meningitis with Acinetobacter calcoaceticus in cerebrospinal fluid. A case report.

A case of meningitis due to Acinetobacter calcoaceticus occurred after neurosurgery. The cerebrospinal fluid cytology showed intracellular diplococci that strongly resembled Neisseria meningitidis. However, subsequent bacteriologic studies revealed a bacterium identical to A. calcoaceticus. It is of practical importance for cytology laboratories to recognize this diplococcal form of organism.

Acinetobacter↗

Acinetobacter meningitis - a diagnostic pitfall. A report of 3 cases.

Three fatal cases of meningitis caused by Acinetobacter calcoaceticus var. anitratus are reported, 1 in a premature infant who was being artificially ventilated and 2 in adults who had had neurosurgical operations. The microscopic resemblance of this organism to Neisseria meningitidis is high-lighted and the problems of antimicrobial therapy are discussed.

Acinetobacter↗

[Bacteria of the species Acinetobacter calcoaceticus as the possible etiological factor in infectious complications in burns].

The results of the study of the etiological role of Acinetobacter calcoaceticus in infectious complications of burning lesions are presented. These bacteria were shown to occur in 28% of burn wounds, quite frequently as a monoculture or association with diphtheroids. A. calcoaceticus were capable of persisting in the wounds during the whole period of treatment (up to 2-3 months). A high level of the contamination of burn wounds with these microorganisms, reaching 10(5)-10(6) cells per 1 g of tissue or 1 cm2 of the wound surface, was observed. The occurrence of A. calcoaceticus in the blood of the patients from whose burn wounds these microorganisms could be isolated was 36.3%. All isolated strains possessed multiple drug resistance.

Acinetobacter↗

[Epidemiology and resistance pattern of Acinetobacter species considering the new nomenclature].

230 clinical isolates of Acinetobacter species were characterized according to genospecies (new taxonomy), relative frequency of isolation, distribution in clinical samples and resistance pattern. A.baumannii was more frequently found than any other species (42%), followed by A.lwoffii (28%), although only 60% of the former "A.lwoffi" corresponds to the new A.lwoffii. The other 40%, formerly A.lwoffi, were shared by A.junii and A.haemolyticus. Concerning habitat and resistance pattern, remarkable differences between the new biotypes were found. A.baumannii and A.lwoffii were isolated mainly from swabs. A.calcoaceticus was most frequently cultivated from samples of the upper respiratory tract, and from blood cultures preferably A.baumannii and, more rarely, A.lwoffii and A.haemolyticus were isolated. A.baumannii showed multidrug resistance against beta-lactam antibiotics, most of the tested penicillins and cephalosporins. The two most susceptible species in our study were A.junii and A.lwoffii. Resistance to imipenem, aminoglycosides and quinolones was rare with all strains.

Acinetobacter↗

Acinetobacter meningitis.

10,468 CSF samples from cases of meningitis in different age groups were cultured during 1988-1991. Acinetobacter calcoaceticus was isolated in 12 (5.6%) of 211 positive cultures. The strain were 100% resistant to ampicillin, cotrimoxazole and tetracycline 50% resistant to cephazolin gentamicin and kanamycin but 100% susceptible to chloramphenicol.

Acinetobacter↗

[A urinary outbreak of Acinetobacter baumanii in a spinal cord injury unit].

From January 1990 to April 1992, 114 urinary strains of Acinetobacter baumanii were isolated in 57 patients with traumatic spinal cord [correction of medular] injury. The strains were characterized by having all of them the same biochemical identification, except for citrate, maltose and tryptophan-desaminase. Until December 1990, (5 strains) were resistant to all antibiotics, except to tobramicine, amikacine, cotrimoxazol and imipenem (6.3%, 33.9%, 26.7% and 0% of resistances, respectively); since January 1991, (99 strains) became resistant to all of them, except to imipenem. 39.5% of AB were isolated in pure cultures, 46% of them with pyuria. Between February 1991 and January 1992, we observed the highest number of affected patients, although without seasonal predominance. We observed as well a higher incidence among males (46 males, 11 females). 80% of them carried a permanent probe. Only 6 patients presented clinical signs directly related to AB. The environmental study could not demonstrate any source of contagion or transmission mechanism.

Acinetobacter Infections↗

[Epidemic occurrences of multiresistant Acinetobacter baumannii strains in a neonatal intensive care unit].

In a period of nine months (May 1991 to January 1992), 39 infants were colonized with Acinetobacter baumannii in a paediatric intensive care unit. Colonization was observed mainly in premature infants, weighing between 680 g and 2,000 g, who were artificially ventilated. Shortly after birth, A. baumannii was isolated regularly from tracheal washings, and less frequently from other material, such as gastric juice, catheter tips, and umbilical swabs. In older children or adults, the bacteria were found only in very low frequency. In the intensive care unit, A. baumannii could be isolated from tap water, sinks, water traps of the ventilation devices, the inner wall of incubators, and from the hands of medical personnel. Patients strains of A. baumannii, and those isolated monitoring the intensive care unit had an identical biochemical profile and a similar pattern of antimicrobial resistance, as well as a similar reaction in other typing methods. Anti-infective measures are discussed.

Acinetobacter↗

Antibiotic resistance pattern and R-plasmids of Acinetobacter calcoaceticus subsp. anitratus.

During a 6 month period from March 1990 to August 1990, a total of 159 strains of Acinetobacter calcoaceticus subsp. anitratus were isolated from various samples and studied for antibiotic resistance pattern to 12 drugs by Kirby-Bauer method. Ceftazidime and Netilmycin were the most sensitive drugs followed by Cefotaxime, Norfloxacin and Augmentin. All the strains were resistant to Chloramphenicol and Tetracycline. Commonest pattern of resistance was ACGKSTSu. Forty eight isolates were tested for R-plasmids by conjugation experiments using Nalidixic acid resistant E. coli K12F-Lac+ as the recipient strain. The incidence of R-plasmids was 81.25%.

Acinetobacter Infections↗

Cell surface properties of Acinetobacter baumannii.

Cell surface properties of 78 strains of Acinetobacter baumannii of different origin (lower respiratory tract, wound, blood and environment) were investigated. The bacterial adhesion to collagen, fibronectin, fibrinogen and vitronectin was detected by particle agglutination assays. Salt aggregation tests were used to determine the cell surface hydrophobicity of isolated A. baumannii strains. We found that A. baumannii strains originating from patients with wound infection and bacteraemia showed significantly lower aggregative properties compared to respiratory and environmental strains. Electron microscopic investigations revealed more fimbriated bacterial cells among the highly aggregative A. baumannii strains. This study demonstrates that the investigated A. baumannii strains can be divided into two different groups according to their cell surface properties and source of isolation, whereas the majority of strains, from the lower respiratory tract and the hospital environment expressed strong adhesive properties.

Acinetobacter↗

Differentiation of Acinetobacter baumannii biotypes by amplification of 16S-23S rRNA intergenic spacer sequences.

Isolates of Acinetobacter baumannii (32 strains) from blood samples obtained from patients in five Chilean hospitals were identified and biotyped according to their phenotypic properties. They were also submitted to random amplified polymorphic DNA (RAPD) using eight randomly designed 10-mers and the core sequence of M13 phage (15-mers) as well as amplification of the spacer regions between 16S and 23S genes in the prokaryotic rRNA genetic loci. With some primers, RAPD discriminated between biotypes, whereas with others each isolate showed a particular profile. When amplification of spacer regions was performed, a clear correlation between patterns and biotypes was found. This last technique allowed correct biotyping of clinical isolates. Both genetic methods might be used for the identification of A. baumannii biotypes.

Acinetobacter↗