A 57-year-old man who had received treatment for B cell lymphoma presented with West Nile virus (WNV) meningoencephalitis. During his 99-day hospitalization, no WNV-specific antibodies were detected. In postmortem central nervous system samples obtained at autopsy, WNV RNA and WNV antigens were detected. This patient's case raises important issues related to the diagnosis, pathogenesis, and possible treatment of persistent WNV infection.

In four patients with Pseudomonas aeruginosa infections, the infecting strain developed resistance to moxalactam during therapy with this drug. In addition, P. aeruginosa isolates from two of these four patients showed increased resistance to aminoglycosides. Isolates from a third patient acquired cross-resistance to other antipseudomonal ,3-lactams. with a final volume of 3 ml and a final inoculum of 105 colony-forming units (CFU) per ml. The minimal inhibitory concentration (MIC) was defined as the lowest antibiotic concentration preventing macroscopically detectable growth after 18 h of incubation at 35°C in air. Subcultures (0.01 ml) were made of all clear tubes to drug-free agar, and the minimal bactericidal concentration (MBC) was defined as the lowest concentration preventing growth upon subculture. This represented a 99.9o kill of the original inoculum (12). MICs or MBCs for posttherapy isolates were considered increased above results obtained with pretherapy isolates if they differed at least fourfold. Tests on pre-and posttherapy isolates were performed simultaneously. Results of susceptibility tests were interpreted according to criteria pubished by the National Committee for Clinical Laboratory Standards (10). For moxalactam, an organism was considered (i) resistant if the MIC was 264 ,ug/ml and (ii) susceptible if the MIC was c32 pLg/ml. ,B-Lactamase assays were performed by a spectrophotometric test as described previously (16). Enzymes were induced by growing the strains overnight on cefoxitin agar (16). Strains resistant to aminoglycosides were tested for inactivating enzymes by R. Hare (Schering Corp., Bloomfield, N.J.).Agarose gel electrophoress. To compare the plasmid profiles of the isolates, cultures were lysed by the method of Meyers et al.

Organisms encoding multiple antibiotic resistance genes are becoming increasingly prevalent. In this report we describe a multiply resistant Klebsiella pneumoniae which possesses at least five different beta-lactamase genes. Isoelectric focusing, polymerase chain reaction and restriction fragment length polymorphism analysis identified TEM-1, multiple SHVs, OXA-9 and a plasmid-mediated ampC, beta-lactamase. Furthermore, Southern analysis and conjugation experiments established that most of the resistance genes were encoded on one large transferable plasmid. This report demonstrates the complexity of multiply resistant organisms.