Plasmid profiles, phage typing, antibiograms, and biotyping were used to characterize Staphylococcus epidermidis isolated from multiple cultures of blood of four patients with prosthetic valve endocarditis. Epidemiological evidence implicated a common source for these infections. Of 20 clinically significant isolates, 14 exhibited variations from the prototype pattern of multiple resistance to five antibiotics. All isolates tested appeared to be the same strain by phage typing. Of 18 isolates available for plasmid analysis, 10 contained six plasmids of identical size, whereas eight differed from the prototype profile in the loss of one to three plasmids. Loss of resistance to gentamicin, chloramphenicol, erythromycin, and clindamycin but not to methicillin was associated with the loss of specific plasmids. Because antibiotic resistance in this strain of S. epidermidis was unstable, the use of antibiograms alone was not a reliable means of evaluating the relatedness of these multiple isolates.

No abstract

Analysis of aminoglycoside-resistant Enterobacteriaceae isolated from patients at the Seattle Veterans Administration Medical Center indicated that a single 68-kilobase R factor was responsible for the epidemic spread of low-level resistance to gentamicin, kanamycin, and tobramycin. An examination, by means of the phosphocellulose paper binding assay, of resistant strains carrying this R factor resulted in the identification of a 2"-O-adenyltransferase [ANT(2")]-modifying enzyme. This enzyme was later detected in strains containing 150-kilobase plasmids. For more convenient monitoring of the dissemination of the ANT(2") gene among clinical isolates at the medical center, a DNA probe was developed by cloning of the ANT(2") structural gene from the 68-kilobase factor into pBR322. A 310-base pair Ava I restriction fragment isolated from the interior of the cloned ANT(2") gene was radiolabeled and used in Southern hybridization gels as a probe for plasmids isolated from aminoglycoside-resistant organisms. The probe proved to be highly specific and was more sensitive than enzymologic techniques for detection of the ANT(2") gene in clinical isolates with complex aminoglycoside resistance phenotypes.

Fifteen isolates of tetracycline-resistant Campylobacterjejuni were recovered from stool samples of cynomologous monkeys (Macaca fascicularis) housed at the University of Washington Primate Research Center, Seattle. Resistance was associated with carriage of a 38-megadalton plasmid which was transmissible to other strains of C. jejuni but not to Escherichia coli. Seven isolates also contained a 2.6-megadalton plasmid which was phenotypically cryptic.Campylobaeterjejuni, recently recognized as an agent of acute diarrheal disease in humans (4,6,7,11,12,16,18,20,21), has been isolated from a variety of animals, including poultry (6,10,13,17,19), rodents (9), domestic herbivores (5)(6)(7)18), and simians (23,24

Two DNA probes were developed to screen for the genes encoding 3'-aminoglycoside phosphotransferase activity in gram-negative bacilli. The 3'-I phosphotransferase [APH(3')I] probe was subcloned from Tn903; the APH(3')II probe was subcloned from Tn5. Each probe proved to be specific for genes corresponding to its own APH(3') subclass and did not hybridize with DNA from other classes when tested at high stringency by either Southern hybridization or dot-blot hybridization methods. The APH(3')I probe hybridized to DNA obtained from organisms demonstrating APH(3')I activity as measured by the phosphocellulose paper binding assay (PPBA) as well as to DNA from organisms reported to have both APH(3')I and APH(3')II activity by PPBA. This probe did not hybridize to DNA from organisms showing only APH(3')II activity by PPBA. The APH(3')II probe demonstrated homology with DNA from organisms showing APH(3')II activity by PPBA but not with DNA from organisms showing APH(3')I activity or both APH(3')I and APH(3')II activity by PPBA. We conclude that organisms previously believed to contain both APH(3')I and APH(3')II genes based on PPBA contain in fact only the APH(3')I gene.