Simplified method for producing pyocins from Pseudomonas aeruginosa

Properties of R plasmids determining gentamicin resistance by acetylation in Pseudomonas aeruginosa

Two clinical isolates of Pseudomonas aeruginosa, one a pyocin type 5 strain from Atlanta, could transfer gentamicin resistance by conjugation. Donor and recipient strains inactivated gentamicin by acetylation. The R plasmids, pMG1 and pMG2, also determined resistance to sisomicin, another substrate of gentamicin acetyltransferase I, sulfonamides, and streptomycin, but not resistance to kanamycin, neomycin, tobramycin, butirosin, or BB-K 8. They were transmissible to many strains of P. aeruginosa, including a Rec(-) strain, but not to Escherichia coli or other enterobacteriaceae. These R plasmids were compatible with R plasmids transmissible to P. aeruginosa from E. coli, including members of C, N, P, and W incompatibility groups. From a strain carrying pMG1 and a compatible plasmid, pMG1 was transferred independently but transfer of the second plasmid often resulted in cotransfer of pMG1. In contrast, pMG1 and pMG2 were incompatible with pseudomonas R plasmids R931 and R3108, and with R931 they readily formed recombinant plasmids. The four plasmids in this incompatibility group determine additional biological properties, including resistance to inorganic and organic mercury compounds, to ultraviolet light, and to certain deoxyribonucleic acid phages. pMG1 and pMG2 also phenotypically inhibited pyocin production. Consequently such R plasmids alter the phage and pyocin types of their host strains.

Epidemiology of Pseudomonas aeruginosa in a general hospital: a four-year study

A retrospective study was done to determine the epidemiology of infection and/or colonization due to Pseudomonas aeruginosa in a Brazilian general hospital. In 1966, 1968, and 1969, there were only two instances where probable cross-contamination was shown; the remaining isolates were unrelated. In late 1971 the hospital experienced a marked increase in P. aeruginosa isolation. Contaminated dextrose solutions used in the infant feeding were the apparent cause of the problem which occurred in the premature and special care nurseries. A contaminated oxygen humidifying bottle was the source of a different outbreak in surgery. There was also evidence in four instances that cross-infection and/or contamination had occurred. Pyocin and serological typing revealed that many strains were involved and led to a clear understanding of the complex epidemiological relationships among all the strains.

Problems in evaluating nitrofurantoin susceptibility tests for Klebsiella-Enterobacter

Tube dilution susceptibility tests in Trypticase soy broth showed that resistance to gentamicin (minimum bactericidal concentration ≧12.5 μg/ml) among hospital isolates of Pseudomonas aeruginosa increased from 13.9% in 1969 to 38.9% in 1972. Transfer of drug resistance to six aminoglycosides from one wild Pseudomonas strain to another was accomplished in recombination experiments. A carbenicillin-resistant, beta-lactamase-producing strain served as the recipient. The exconjugant was resistant not only to aminoglycosides, including amikacin, but also to all clinically employed antimicrobials. Aminoglycoside resistance in the exconjugant was cured by sodium dodecyl sulfate. This transferable aminoglycoside resistance was not mediated by adenylylation or, as judged by bioassay, by other antibiotic-inactivating or -modifying processes.

Pyocin typing of Pseudomonas aeruginosa: a simplified method

A simplified method has been devised for typing Pseudomonas aeruginosa by pyocin production. Pyocins are produced as strains grow overnight in Trypticase soy broth (without glucose) plus 1% potassium nitrate. Because P. aeruginosa can use nitrate instead of oxygen as a terminal electron acceptor, mechanical shaking is not necessary, nor is induction by mitomycin C. Pyocins can now be produced in screw-cap tubes in a water bath or incubator. A total of 250 strains were tested as possible pyocin indicators, which included 60 strains already used in pyocin-typing systems. The final set contained 18 indicators which were chosen because (i) they had clear positive or clear negative reactions, thus eliminating reactions difficult to read, (ii) they had few zones due to bacteriophage lysis, and (iii) they were most sensitive in differentiating clinical isolates of P. aeruginosa. The final typing method was tested in several studies and the results were clear; thus definitive epidemiological conclusions could be made. Because it is simple to perform and easily automated, the new method should have application in many hospitals; however, it should be used only in carefully planned epidemiological studies. The method and its application are described in detail, and some pitfalls are discussed.

Pyocin sensitivity of Pseudomonas species

Only the fluorescent pseudomonads, Pseudomonas aeruginosa, P. putida, and P. fluorescens, were sensitive to pyocins produced from P. aeruginosa.