StaphPlex system for rapid and simultaneous identification of antibiotic resistance determinants and Panton-Valentine leukocidin detection of staphylococci from positive blood cultures.

Phenotypic methods take several days for identification and antimicrobial susceptibility testing of staphylococcal isolates after gram-positive cocci in clusters (GPCC) are observed in positive blood cultures. We developed and validated a StaphPlex system that amplifies and detects 18 gene targets simultaneously in 1 reaction for species-level identification of staphylococci, detection of genes encoding Panton-Valentine leukocidin (PVL), and antimicrobial resistance determinants of staphylococci. The StaphPlex system was compared to phenotypic methods for organism identification and antimicrobial resistance detection for positive blood culture specimens in which GPCC were observed. Among a total of 360 GPCC specimens, 273 (75.8%), 37 (10.3%), 37 (10.3%), 1 (0.3%), 3 (0.8%), and 9 (2.5%) were identified by StaphPlex as coagulase-negative Staphylococcus (CoNS), methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptible S. aureus (MSSA), or mixed infections of CoNS and MRSA, CoNS and MSSA, or nonstaphylococci, respectively, with an overall accuracy of 91.7%. The 277 CoNS-containing specimens were further identified to the species level as containing 203 (73.3%) Staphylococcus epidermidis isolates, 10 (3.6%) Staphylococcus haemolyticus isolates, 27 (9.7%) Staphylococcus hominis isolates, 1 (0.4%) Staphylococcus lugdunensis isolate, and 36 (13.0%) other CoNS isolates, with an overall accuracy of 80.1% compared to an API STAPH test and CDC reference identification. Numerous very major errors were noticed when detection of aacA, ermA, ermC, tetM, and tetK was used to predict in vitro antimicrobial resistance, but relatively few major errors were observed when the absence of these genes was used to predict susceptibility. The StaphPlex system demonstrated 100% sensitivity and specificity, ranging from 95.5% to 100.0% when used for staphylococcal cassette chromosome mec typing and PVL detection. StaphPlex provides simultaneous staphylococcal identification and detection of PVL and antimicrobial resistance determinants within 5 h, significantly shortening the time needed for phenotypic identification and antimicrobial susceptibility testing.

Degradation of volatile hydrocarbons from steam-classified solid waste by a mixture of aromatic hydrocarbon-degrading bacteria.

Steam classification is a process for treatment of solid waste that allows recovery of volatile organic compounds from the waste via steam condensate and off-gases. A mixed culture of aromatic hydrocarbon-degrading bacteria was used to degrade the contaminants in the condensate, which contained approx. 60 hydrocarbons, of which 38 were degraded within 4 d. Many of the hydrocarbons, including styrene, 1,2,4-trimethylbenzene, naphthalene, ethylbenzene, m-/p-xylene, chloroform, 1,3-dichloropropene, were completely or nearly completely degraded within one day, while trichloroethylene and 1,2,3-trichloropropane were degraded more slowly.

Degradation of mixtures of aromatic and chloroaliphatic hydrocarbons by aromatic hydrocarbon-degrading bacteria.

The well-characterized toluene-oxidizing bacteria Pseudomonas putida PaW1, P. putida F1, P. mendocina KR1, Burkholderia cepacia G4, B. cepacia JS150, and Ralstonia pickettii PKO1, as well as several strains of bacteria isolated from activated sludge, were examined for their ability to degrade mixtures of aromatic and chloroaliphatic hydrocarbons. Collectively, the strains tested were able to transform all of the 14 aromatic hydrocarbons included in the mixtures, with most strains degrading five or more. Few strains degraded trichloroethylene well under these conditions, only one degraded methylene chloride, and none were able to transform chloroform. G4, PKO1, KR1, F1, and JS150 exhibited generally broad but oxygenase-specific degradation profiles, with the three monooxygenase strains degrading significantly more o-xylene and trichloroethylene, and F1 and JS150 degrading greater quantities of isopropylbenzene and 1,4-dichlorobenzene. PaW1 degraded only the methylaromatic hydrocarbons and styrene. Sludge isolates enriched on benzene, toluene, styrene and the xylenes exhibited degradation profiles similar to F1 or PaW1, while the pattern of hydrocarbon degradation for the ethylbenzene, isopropylbenzene, 1,3,5-trimethylbenzene, and 1,3-dichlorobenzene isolates were distinct from the other strains and from each other. Overall, our results showed that many of the bacteria which utilize aromatic compounds are capable of degrading a diverse array of aromatic hydrocarbons in mixtures, but that chloroaliphatics such as methylene chloride and chloroform may be recalcitrant to co-oxidation in the presence of aromatics or trichloroethylene.