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PubMed2004

[Carbapenemase detection in Acinetobacter baumannii clones resistant to imipenem].

INTRODUCTION: The aim of this study was to detect carbapenemases in imipenem-resistant Acinetobacter baumannii isolates obtained in the microbiology department of a Basque Country Public Health Service hospital over a period of 19 months, and to genetically characterize the resistant clones. METHODS: Susceptibility tests to imipenem, meropenem, ticarcillin, ceftazidime, cefotaxime, cefepime and aztreonam were done by determining the minimum inhibitory concentration on agar plates. A tRNA technique was used for species identification and PCR with primers ERIC2, AP3 and M13 for genetic typing of resistant isolates. Carbapenemase production was detected by the Hodge test and metallo-beta-lactamase by the EDTA test and Etest MBL. RESULTS: A total of 76 isolates were resistant to imipenem and 49 of these were resistant to all the betalactam antibiotics tested. Genetic typing showed three predominant clones, denominated I (9 isolates), II (48 isolates) and III (8 isolates). Hodge and EDTA tests were positive in 45 and 8 isolates belonging to clone II, 8 and 4 belonging to clone I and 7 and 3 belonging to clone III, respectively. The Etest confirmed 7 results (45% of the 17 positive EDTA test isolates). CONCLUSION: Our results show that one factor contributing to the high level of imipenem resistance in the isolates analyzed is dissemination of a predominant, multiresistant clone able to produce OXA-type carbapenemases and metallo-beta-lactamases.

Acinetobacter Infections↗
PubMed2004

[Clonal diversity and antimicrobial susceptibility of Acinetobacter baumannii isolated in Spain. A nationwide multicenter study: GEIH-Ab project (2000)].

INTRODUCTION: A nationwide multicenter study was performed in Spain to evaluate the clonal diversity and antimicrobial susceptibility of Acinetobacter baumannii clinical isolates. METHODS: A total of 221 consecutive A. baumannii isolates recovered from clinical samples from 25 Spanish hospitals during November 2000 were studied. Isolate identification was performed by phenotyping methods and by amplified rDNA restriction analysis. Clonal relationships among A. baumannii isolates were determined by pulsed field gel electrophoresis. MICs of amikacin (AK), ampicillin (AP), cephalothin (CF), cefoxitin (FX), ceftazidime (CZ), ciprofloxacin (CP), cotrimoxazole (T/S), doxycycline (DX), gemifloxacin (GX), gentamicin (GN), imipenem (IP), meropenem (MP), minocycline (MI), piperacillin (PP), polymyxin B (PB), rifampicin (RI), tetracycline (TT), sulbactam (SB) and tobramycin (TO) were determined by microdilution (NCCLS guidelines). RESULTS: Seventy-nine A. baumannii clones were differentiated. MIC50/MIC90 (mg/L) values for the 221 A. baumannii isolates were PP: > 512/> 512; AP, CF, FX: > 256/> 256; TT, GN: > 128/> 128; CZ: 128/> 256; CP: > 64/> 64; FP: 64/256; AK: 32/256; DX: 32/64; GX: > 16/> 16; TO: 16/128; SB, T/S: 16/64; MP: 8/> 128; IP: 4/128; RF: 4/8; MI: 2/16 and PB: 1/2. Percentages of susceptible isolates were PB: 100%; MI: 65.8%; IP: 52.5%, RF: 49.3%; SB: 46.7%; MP: 43.1%; AK: 34.7%; DX: 32.0%; TO: 21.3% and CZ, FP, GN, T/S, TT, GX, CP, AP, PP, CF and FX: < 20%. CONCLUSIONS: A. baumannii isolates show high clonal variability in Spain. The most active antimicrobial agents against this organism were polymyxin B, minocycline, rifampicin, imipenem, sulbactam, meropenem, amikacin and doxycycline.

Acinetobacter Infections↗
PubMed2001

Acinetobacter baumannii--an emerging nosocomial pathogen in the burns unit Manipal, India.

A retrospective study on 113 patients admitted to the burns unit over a period of 12 months was undertaken to investigate the emerging trend of Acinetobacter baumannii infection. Wound infection with A. baumannii was seen in 13 (11.5%) patients. Of these six (46%) patients developed septicaemia with the same bacteria and five (38%) expired. The virulence of these bacteria, drug susceptibility pattern and its role as a nosocomial pathogen is discussed.

Acinetobacter↗
PubMed2002

Multi-resistant Acinetobacter baumannii on a burns unit--clinical risk factors and prognosis.

Burns patients are highly susceptible to infection, and preventing and treating infection are integral to the successful management of severe burns.Multi-resistant Acinetobacter baumannii (MR-AB) strains are becoming increasingly important in nosocomial infections. We conducted a retrospective study of all adult admissions to the Singapore General Hospital (SGH) National Burns Center over an 18-month period. The only independent risk factors for the acquisition of MR-AB were the APACHE II score on admission and the number of intravascular lines placed. The only independent predictor of infection with MR-AB was the number of intravascular lines placed. The only independent predictors of longer length of stay were the total number of operations required and infection with MR-AB. The only independent predictor of mortality was the APACHE II score. This is in contrast to other studies that have suggested that the acquisition of MR-AB is an independent risk factor for mortality.

APACHE↗
PubMed2000

Evaluation of antibiotic synergy against Acinetobacter baumannii: a comparison with Etest, time-kill, and checkerboard methods.

Acinetobacter baumannii is becoming increasingly resistant to antibiotics, often requiring combination therapy. Numerous methods exist to detect the presence of in vitro synergy with the time-kill and checkerboard tests being widely used. The Epsilometer test (E test) is a new method that is less labor intensive, but has not been evaluated using a wide range of antimicrobials and organisms. We assessed synergy using the time-kill and checkerboard tests and compared the results to the E test method using 10 clinical isolates of A. baumannii. Antimicrobial combinations evaluated consisted of trovafloxacin or tobramycin in combination with cefepime or piperacillin. Synergy was detected with all combinations by either the checkerboard or time-kill method. Synergy was not detected by the Etest method. The agreement between the time-kill test and Etest method was 72% (range 42-97%); for the time-kill and checkerboard tests, agreement was 51% (range 30-67%). The Etest method appears promising although further testing should be performed with additional antimicrobial agents and organisms.

Acinetobacter↗
PubMed2003

Identification of an epidemic carbapenem-resistant Acinetobacter baumannii strain at hospitals in Buenos Aires City.

To identify epidemic Acinetobacter baumannii (AB) clones, 38 carbapenem-resistant AB isolates from 5 hospitals were analyzed. Macrorestriction classified 24 isolates as clone IV, susceptibility pattern clustering analysis grouped almost all of them together, and they were uniformly biotype 8. Clone IV was present at all 5 hospitals, so that it represents a carbapenem-resistant AB strain with epidemic behavior.

Acinetobacter Infections↗
PubMed1997

Activity of selected beta-lactams, ciprofloxacin, and amikacin against different Acinetobacter baumannii biotypes from Chilean hospitals.

The activity of some third generation cephalosporins, aztreonam, imipenem, ciprofloxacin, and amikacin against isolates of Acinetobacter baumannii of various biotypes has been studied. The isolates, independently of the biotype, exhibited a broad multiresistance against cephalosporins. Ceftazidime was the most active and cefoperazone the least active compound. Aztreonam also showed low activity and no imipenem-resistant strains were found. Ciprofloxacin and amikacin were somewhat more active than cephalosporins, but resistant isolates were also frequent. Isolates of Biotypes 9 and 8 exhibited broader multiresistance than those of Biotype 6 and "other."

Acinetobacter↗
PubMed1999

PCR detection of aminoglycoside resistance genes: a rapid molecular typing method for Acinetobacter baumannii.

Aminoglycoside resistance is common among strains of Acinetobacter baumannii responsible for nosocomial infections, and inactivation of these antibiotics by enzymatic modification is the main mechanism. Different types of aminoglycoside acetyltransferases (AAC), nucleotidyltransferases (ANT), and phosphotransferases (APH) are synthesized by clinical isolates, and several enzymes can be produced by a single strain. Using a multiplex PCR procedure carried out on bacterial thermolysates, we analyzed the aminoglycoside resistance gene content of strains belonging to eight clusters identified by pulsed-field gel electrophoresis. In a single reaction were combined three primer pairs in order to amplify the genes coding for AAC(6')-Ih, AAC(3)-I, and AAC(3)-II, three primer pairs for the genes coding for ANT(2'')-I, APH(3')-VI, and rRNA 16S as internal control, and finally two primer pairs for the genes coding for AAC(6')-Ib and APH(3')-I. According to the aminoglycoside resistance gene patterns, the strains of the eight clusters were distributed into seven classes. This simple and rapid (< 8 h) fingerprinting technique could be a useful tool for the epidemiological investigation of A. baumannii nosocomial infections.

Acetyltransferases↗
PubMed2002

In vitro investigation of the susceptibility of Acinetobacter baumannii strains isolated from clinical specimens to ampicillin/sulbactam alone and in combination with amikacin.

The sensitivity of 52 strains of Acinetobacter baumannii was determined to 13 antimicrobial drugs. All strains tested were multiresistant. Compared with MICs of amikacin and ampicillin/sulbactam alone, there was a significant decrease in MICs for both drugs when the combination was used. The results of the in vitro study of this combination showed a synergistic or partial synergistic effect in 98% of the strains.

Acinetobacter Infections↗
PubMed2003

Severe nosocomial infections with imipenem-resistant Acinetobacter baumannii treated with ampicillin/sulbactam.

Forty consecutive patients with nosomial infections caused by multidrug-resistant Acinetobacter baumannii were treated with intravenous ampicillin/sulbactam. The infections were primary bloodstream (32.5%), pneumonia (30%), urinary tract (15%), peritonitis (7.5%), surgical site (7.5%), meningitis (5%) and sinusitis (2.5%). Most were severe infections with underlying conditions (median APACHE II score: 14.5) and 72.5% occurred in the ICU. Twenty-seven (67.5%) were improved/cured, seven (17.5%) were failures and six (15%) were considered to have an indeterminate outcome because patients died within the first 48 h of treatment. Two cases of meningitis were treated and did not respond. The median daily dose of ampicillin/sulbactam was 6 g/3 g and six patients received 12 g/6 g. No adverse effects were observed. This study indicates that ampicillin/sulbactam may be a good and safe therapeutic option to treat severe nosocomial infections caused by multi-drug resistant A. baumannii.

Acinetobacter Infections↗
PubMed1993

Immunobiology of Acinetobacter baumannii and genospecies 3.

Five representative, taxonomically and serologically defined clinical isolates of Acinetobacter baumannii and genospecies 3, and A. baumannii strain ATCC 19606 were examined for immunogenicity in rabbits following experimental bacteremia. All rabbits seroconverted as determined with the aid of the tube O-agglutination, indirect hemagglutination, and enzyme-linked immunosorbent assay (ELISA) procedures. Immunoblots detected over twenty immunogenic, proteinase-K-degradable polypeptide antigens in trichloroacetic acid extracts, outer membrane protein fractions, and mechanically disrupted (type MM2 mixer drill) cell preparations. Sodium periodate-susceptible phenol-water and phenol-chloroform-light petroleum lipopolysaccharide (LPS) extracts proved to be immunogenic for the rabbits as well. Convalescent sera from two patients with documented bacteremia due to genospecies 3, serovar 4, likewise revealed numerous anti-polypeptide and anti-LPS antibodies comprising the immunoglobulin G (IgG) and the IgM class.

Acinetobacter↗
PubMed1993

The distribution of Acinetobacter species in clinical culture materials.

A total of 584 Acinetobacter strains were isolated from 420 patients from 12 different hospitals over a period of twelve months. Identification of strains at the species level was done according to the new taxonomy proposed by Bouvet and Grimont. A. baumannii strains were isolated most frequently (n = 426; 72.9%), followed by A. species 3 (n = 55), A. johnsonii (n = 29), and A. lwoffii (n = 21). Most isolates were recovered from respiratory tract specimens (n = 251; 42.9%), blood cultures (n = 116; 19.9%), wound swabs (n = 90; 15.4%), catheter tips (n = 75; 12.8%), and urinary tract specimens (n = 20; 3.4%). Strains belonging to species other than A. baumannii were isolated more frequently (n = 158; 27.1%) than previously reported, mainly from blood cultures, respiratory tract specimens, and central venous catheters.

Acinetobacter↗
PubMed1993

Comparative characterization of Acinetobacter strains isolated from different foods and clinical sources.

Eighty-three Acinetobacter strains from clinical sources, and 170 from various foods (including fresh and spoiled meat and fish, vegetables, raw milk and cheese) were identified according to recently improved taxonomy, using a computer-assisted probabilistic method based on phenotyping tests. Apart from some atypical characters, most of the strains (94%) were identified to belong to the genospecies or groups of genospecies described in the literature. Among our strains from hospitals, the A. calcoaceticus- A. baumannii complex predominated, whereas the strains isolated from food were predominated by genospecies 7 (A. johnsonii), followed by genospecies 8/9 (A. lwoffii). The isolates from clinical environments showed a major incidence of antibiotic resistance, haemolytic strains and strains producing polysaccharidic material.

Acinetobacter↗
PubMed1996

Biotypes, serovars and antimicrobial resistance patterns of Acinetobacter baumannii clinical isolates.

255 Acinetobacter strains, from clinical specimens of inpatients and outpatients, were identified phenotypically according to the new taxonomy proposed by Bouvet and Grimont. A. baumannii was the most frequent species (80.8%). This species underwent biotyping and serotyping according to the scheme of Bouvet and Grimont, and that of Traub, respectively, 81.2% of samples belonged to biotypes 2, 6 and 9 with a predominance of biotype 2. 86.6% of the strains could be serotyped; 2 new serotypes were encountered. The new serotype 29, being the most frequently isolated, was related to biotype 2 (86.6%), whereas serotype 13 was related to biotype 6 (84.8%). These clones presented marked multiple resistance patterns and were widespread in different wards. No outbreak was reported during the period studied. These phenotypical methods proved to be useful in differentiating strains of A. baumannii and, if used together, they showed a high discriminatory power.

Acinetobacter↗
PubMed1996

Clusters of nosocomial cross-infection due to Acinetobacter baumannii and genospecies 3: comparison of serotyping with macrorestriction analysis of genomic DNA with pulsed-field gel electrophoresis.

Triplets of isolates representing 20 putative clusters of nosocomial cross-infection due to Acinetobacter baumannii and genospecies 3 were examined comparatively using serotyping and analysis of restriction fragments (SmaI and ApaI) of genomic DNA with the aid of pulsed-field gel electrophoresis. Carbon source assimilation tests disclosed phenotypic variation among 6 to 20 triplets of isolates. Two misleading results of serotyping were encountered. With respect to the presumptive cluster No. 9, one of the genospecies 3 (originally serovar 4) isolates proved to be polyagglutinable upon repeat examination; this particular putative cluster was shown to be a pseudocluster by comparison of the macrorestriction profiles of the respective triple isolates. A strain of A. baumannii serovar 15 had infected 8 patients in a surgical intensive care unit, while a second, genotypically totally different strain of identical serovar had caused infection in one additional patient. With this exception, the correlation between serotyping and analysis of macrorestriction profiles was excellent.

Acinetobacter↗
PubMed1997

An apparent outbreak of infection with Acinetobacter calcoaceticus reconsidered after investigation by pyrolysis mass spectrometry.

In a previously reported apparent outbreak of infection due to Acinetobacter calcoaceticus on a Regional Burns Unit in which both clinical and environmental isolates were available for study, investigations of the organisms by electrophoretic typing of surface proteins, plasmid profiling and antibiograms were inconclusive and unable to identify a single epidemic strain of the organism. The same collection of isolates has been analysed for inter-strain comparison by pyrolysis mass spectrometry (PyMS). PyMS analysis suggested that a few isolates were very different from the majority but that most of the collection comprised a group of closely similar but nonetheless distinct isolates. These isolates may well be representatives of a limited variety of strains occupying an ecological niche but not yet a single emergent strain. The ability of PyMS to detect a single epidemic strain of A. calcoaceticus when present in such a collection of isolates was demonstrated by analysis of a "constructed outbreak collection", using some of the original isolates. This study illustrates the versatility of PyMS for inter-strain comparison studies of species not yet amenable to conventional typing methods. The application of rapid, highly discriminatory, high-volume inter-strain comparison methods such as PyMS to apparent outbreaks of nosocomial infection is likely to reveal patterns of organism acquisition other than point-source transmission.

Acinetobacter Infections↗