Over a 2 1 ⁄2-month period in 1999, 37 ceftazidime-resistant nonrepetitive enterobacterial isolates were collected from 37 patients in a Bangkok hospital, Thailand. Eighty-one percent of these strains expressed a clavulanic acid-inhibited extended-cephalosporin resistance profile. An identical extended-spectrum -lactamase (ESBL), VEB-1, was found in 16 unrelated enterobacterial isolates (Escherichia coli, n ؍ 10; Enterobacter cloacae, n ؍ 2; Enterobacter sakazakii, n ؍ 1; and Klebsiella pneumoniae, n ؍ 3) and in two clonally related E. cloacae isolates. The bla VEB-1 gene was located on mostly self-conjugative plasmids (ca. 24 to 200 kb) that conferred additional non--lactam antibiotic resistance patterns. Additionally, the bla VEB-1 gene cassette was part of class 1 integrons varying in size and structure. The bla VEB-1 -containing integrons were mostly associated with bla OXA-10 -like and arr-2-like gene cassettes, the latter conferring resistance to rifampin. These data indicated the spread of bla VEB-1 in Bangkok due to frequent transfer of different plasmids and class 1 integrons and rarely to clonally related strains. Plasmid-and integron-mediated resistance to rifampin was also found in enterobacterial isolates.
The beta-lactamase gene content and epidemiology of ceftazidime-resistant Pseudomonas aeruginosa isolates (24% of the total number of P. aeruginosa isolates) were investigated at a University Hospital in Thailand during a 4-month period in 1999. Of 33 nonrepetitive clinical isolates, 31 produced a VEB-1-like clavulanic acid-inhibited extended-spectrum beta-lactamase (ESBL). These isolates belonged to different pulsed-field gel electrophoresis types and subtypes. In 1 case, the bla(VEB-1)-like gene was plasmid located. The bla(VEB-1)-like genes were present as a gene cassette on class 1 integrons that varied in size and structure. In most cases, the veb-1 cassette was associated with an arr-2 cassette (rifampin resistance), aminoglycoside resistance gene cassettes, and an oxa-10-like cassette encoding a narrow-spectrum oxacillinase-type beta-lactamase. The present study indicates that ESBLs may be endemic in P. aeruginosa and illustrates that integrons are efficient means for their spread.
We have studied the appearance of whole-cell oxidizing activity for n-alkanes and their oxidation products in strains of Pseudomonas putida carrying the OCT plasmid. Our results indicate that the OCT plasmid codes for inducible alkane-hydroxylating and primary alcohol-dehydrogenating activities and that the chromosome codes for constitutive oxidizing activities for primary alcohols, aliphatic aldehydes, and fatty acids. Mutant isolation confirms the presence of an alcohol dehydrogenase locus on the OCT plasmid and indicated the presence of multiple alcohol and aldehyde dehydrogenase loci on the P. putida chromosome. Induction tests with various compounds indicate that inducer recognition has specificity for chain length and can be affected by the degree of oxidation of the carbon chain. Some inducers are neither growth nor respiration substrates. Growth tests with and without a gratuitous inducer indicate that undecane is not a growth substrate because it does not induce alkane hydroxylase activity. Using a growth test for determining induction of the plasmid alcohol dehydrogenase it is possible to show that heptane induces this activity in hydroxylase-negative mutants. This suggests that unoxidized alkane molecules are the physiological inducers of both plasmid activities.
A new rifampin resistance gene, arr-2, has been found in Pseudomonas aeruginosa. The ARR-2 protein shows 54% amino acid identity to the rifampin ADP-ribosylating transferase encoded by the arr gene from Mycobacterium smegmatis. This arr-2 gene is located on a gene cassette within a class I integron.
The plasmid-determined inducible alkane hydroxylase of Pseudomonas putida resolved into particulate and soluble fractions. Spinach reductase and spinach ferredoxin could replace the soluble hydroxylase component. Two alkane hydroxylase mutants show in vitro complementation (S. Benson and J. Shapiro, J. Bacteriol., 123: 759-760, 1975): one, alk-7, lacks an active soluble component and the other, alk-181, lacks an active particulate component. Together with previous results on a particulate alcohol dehydrogenase enzyme (Benson and Shapiro, J. Bacteriol., 126: 794-798, 1976), these results allowed us to assay three plasmid-determined inducible activities: soluble alkane hydroxylase (alkA ), particulate alkane hydroxylase (alkB ), and particulate alcohol dehydrogenase (alkC-). Growth tests and in vitro complementation assays revealed three groups of plasmid mutations that block expression of alkane hydroxylase activity: alkA, which so far includes only the alk-7 mutation; alkB, which includes alk-181 and 11 other mutations; and a pleiotropicnegative class, which includes nine mutations that lead to loss of alkA 4, alkB , and alkC+ activities. Thus, the alkgene cluster found on IncP-2 plasmids contains at least four cistrons. We believe it is significant that two of these determined the presence of membrane proteins. The accompanying paper shows that these loci are part of a single regulon.MATERIALS AND METHODS Bacterial strains. We used the Pseudomonas aeruginosa and Pseudomonas putida strains de-614 on July 16, 2020 by guest
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.