A multiplex polymerase chain reaction (PCR) was developed to detect the presence of the ail, yst, and virF genes of Yersinia enterocolitica simultaneously, quickly and accurately. The amplified fragment sizes were 356 base-pairs (bp) for the ail gene, 134 bp for the yst gene, and 231 bp for the virF gene. The specificity of the amplified products was confirmed by hybridization with digoxigenin-labelled oligonucleotide probes. Amplification was successful whether the template was derived from a single colony of bacteria, aliquots of boiled bacterial suspensions, from DNA extracted from pure or mixed cultures or from stool specimens. Amplification of the virF gene was also achieved from strains of Y. pseudotuberculosis carrying the 70 kb plasmid but not with preparations from other related Yersinia species or from other members of the family Enterobacteriaceae. The detection limit we established was 5-10 colony forming units per millilitre (cfu/ml) and 1.0 pg of DNA.

One hundred two isolates of methicillin-resistant Staphylococcus aureus (MRSA) randomly selected from across the Canadian province of Ontario were tested for their susceptibility to ciprofloxacin, norfloxacin, and nalidixic acid by the agar dilution method. Forty-nine percent (50 of 102) had high levels of resistance to these quinolone compounds. For the 50 resistant isolates, ciprofloxacin and norfloxacin had high MICs for 90% of isolates (MIC90s) of 128 ,ug/ml and >128 ,ug/ml, respectively; for these isolates, the nalidixic acid MIC90 was >640 ,ug/ml. The majority (98%) of the 50 isolates were also resistant to tobramycin (MIC90, >128 ,ug/ml), while 42% of the isolates were resistant to gentamicin (MIC90, 64 ,ig/ml). Quinolone-resistant MRSA isolates were susceptible to bacteriophages from several groups, indicating independent selection of resistant strains. These results suggest that a reappraisal of the use of fluoroquinolones against MRSA in Canada is necessary.

Polymyxin B sulfate diminished the endotoxin-mediated release of human blood neutrophil lysosomal enzymes. Similarly, this antibiotic reduced the endotoxin-induced increase in the neutrophil hexose monophosphate pathway activity as measured by the release of 14CO2 from [l-14C]glucose. Although these effects were seen with therapeutically attainable levels of polymyxin B sulfate, they could not be demonstrated when the cell-endotoxin interaction preceded treatment with polymyxin B sulfate.

Two hundred and fourteen isolates of Salmonella typhi submitted to our laboratory between 1992 and 1996 were tested for susceptibility to 20 antimicrobial agents. Forty-eight of the 214 isolates (22.4%), recovered from individuals who had travelled in South Asia, were multiresistant. Forty-four of the 48 isolates were resistant to ampicillin, chloramphenicol, tetracycline, streptomycin, sulfamethoxazole, trimethoprim, cotrimoxazole, ticarcillin, and piperacillin; the other four isolates were resistant to four to six agents. Forty-two of the multiresistant isolates belonged to Vi phage type E1, two isolates from the Punjab State belonged to phage type A, another from the Punjab State belonged to phage type E3, one isolate from Pakistan belonged to type M1, and one isolate from India belonged to type J1. Plasmids from 45 of 48 isolates showed a temperature-sensitive mechanism of transfer to Escherichia coli K-12 strains, characteristic of H1 incompatibility group plasmids. The majority of plasmids had an estimated molecular weight of 120 MDa and encoded both citrate utilization and mercury resistance. Plasmids from three isolates had an estimated molecular weight of 112-115 MDa; one of these isolates encoded citrate utilization but not mercury resistance. Analysis of isolates by pulsed-field gel electrophoresis after digestion with XbaI and SpeI indicated that the majority of multiresistant isolates shared a common restriction profile, while four isolates had unique patterns.

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