The occurrence of multidrug-resistant Pseudomonas aeruginosa on hydrocarbon-contaminated sites

The main aim of this paper was the comprehensive estimation of the occurrence rate and the antibiotic-resistance conditions of opportunistic pathogen Pseudomonas aeruginosa in hydrocarbon-contaminated environments. From 2002 to 2007, 26 hydrocarbon-contaminated sites of Hungary were screened for the detection of environmental isolates. Altogether, 156 samples were collected and examined for the determination of appearance, representative cell counts, and antibiotic-resistance features of P. aeruginosa. The detected levels of minimal inhibitory concentrations of ten different drugs against 36 environmental strains were compared to the results of a widely used reference strain ATCC 27853 and four other clinical isolates of P. aeruginosa. Based on our long-term experiment, it can be established that species P. aeruginosa was detectable in case of 61.5% of the investigated hydrocarbon-contaminated sites and 35.2% of the examined samples that shows its widespread occurrence in polluted soil-groundwater systems. In the course of the antibiotic-resistance assay, our results determined that 11 of the examined 36 environmental strains had multiple drug-resistance against several clinically effective antimicrobial classes: cephalosporins, wide spectrum penicillins, carbapenems, fluoroquinolones, and aminoglycosides. The fact that these multiresistant strains were isolated from 8 different hydrocarbon-contaminated sites, mainly from outskirts, confirms that multiple drug-resistance of P. aeruginosa is widespread not only in clinical, but also in natural surroundings as well.

Chryseobacterium hungaricum sp. nov., isolated from hydrocarbon-contaminated soil

The taxonomic position of a strain isolated from kerosene-contaminated soil in Hungary and formerly misidentified as Brevundimonas vesicularis was examined using a polyphasic approach. The isolate, designated CHB-20p(T), could be clearly assigned to the genus Chryseobacterium (family Flavobacteriaceae) on the basis of 16S rRNA gene sequence similarity. Strain CHB-20p(T), a moderate oil degrader, was a Gram-negative, aerobic, mesophilic microbe with a temperature optimum of 28-30 degrees C. Predominant fatty acids were iso-C(15 : 0), summed feature 3 (comprising C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH) and iso-C(17 : 0) 3-OH. Menaquinone-6 (MK-6) was the predominant respiratory quinone; MK-5 was present as a minor component. The almost complete 16S rRNA gene sequence of strain CHB-20p(T) shared 94-97 % similarity with sequences of the type strains of species of the genus Chryseobacterium. DNA-DNA relatedness between strain CHB-20p(T) and its closest relative, Chryseobacterium caeni, was lower than 46 %. Moreover, several diagnostic phenotypic properties distinguished strain CHB-20p(T) from C. caeni. On the basis of biochemical, chemotaxonomic and genotypic data, isolate CHB-20p(T) represents a novel species within the genus Chryseobacterium, Chryseobacterium hungaricum sp. nov.; the type strain is CHB-20p(T) (=NCAIM B2269(T)=DSM 19684(T)).

Comparison of phenotypic and genotypic methods for the detection of environmental isolates of Pseudomonas aeruginosa

During remediation processes, biological monitoring should be generally required. Hydrocarbon contaminated soils may provide favorable conditions for several opportunistic pathogenic microorganisms, thereby increasing their populations over risky levels. Therefore, during remediation processes of the subsurface medium biological monitoring is of prime importance. The accuracy, time and cost efficiency of the relevant identification method are major factors while monitoring these microbes. During previous years (2002-05), we collected 68 soil samples from 17 different oil contaminated sites, such as petrol stations, airfields and pipeline-breaks. We compared frequently applied detection methods of Pseudomonas aeruginosa, both traditional microbiological and molecular biological techniques, on 43 environmental isolates originating from these sites. The following methods were subjected to comparative analysis: (i) the Hungarian Standard method; (ii) the method described in "The Prokaryotes" handbook; (iii) the API 20NE biochemical fingerprinting, as well as PCR protocols aimed to amplify; (iv) the exotoxin-A gene; and (v) the 16S rDNA variable regions V2 and V8. In five cases, phenotypic methods gave false-negative results. 16S rDNA sequence analysis was done to confirm the identity of these five strains, which verified the results of molecular methods. In addition, faults were found in the evaluation of the originally described ETA PCR protocol, which was corrected by us.

Comparative biodegradation examination of Pseudomonas aeruginosa (ATCC 27853) and other oil degraders on hydrocarbon contaminated soil

The soil that we investigated in our experiment was extremly high contaminated with petroleum hydrocarbons. The sample was originated from a former truck factory, next to an oil tank. We tried on this sample three different biodegradation treatments in a soil respirometer. The aim of the experiment was investigate if the clinical strain Pseudomonas aeruginosa ATCC 27853 is able to utilize petroleum hydrocarbons as carbon source. In spite of the relevant literature Pseudomonas aeruginosa ATCC 27853 (clinical isolate, from blood) was proven to be a good oil degrader.