One hundred and ninety-five central venous catheters used for intravenous nutrition in 113 patients were studied prospectively. Catheter-related sepsis (CRS), defined by recovery of the same organism from the catheter tip and peripheral blood cultures, occurred with only 3.3 per cent of catheters or 2.3 per 1000 days of therapy. In contrast, CRS was suspected with 30 per cent of catheters and catheter contamination occurred in 37 per cent. Contamination was defined by a positive catheter tip culture without recovery of the same organism from the blood. CRS was present in 4 of 12 cases (33 per cent) with greater than 1000 colony forming units on the catheter tip but in only 2 of 54 (4 per cent) with fewer organisms. Thirty-eight cases suspected of having CRS were randomized to have catheter removal and later replacement, or replacement over a guidewire. There were no significant differences in the catheter contamination rate but there were significantly fewer problems of insertion in the guidewire group. However, transfer of Klebsiella sp., during the guidewire procedure, resulted in subsequent sepsis in one case. It is concluded that replacement of catheters over a guidewire is a safe and convenient way of establishing whether sepsis is catheter-related. Because organisms may be transferred, the procedure is not an appropriate treatment for catheter-related sepsis.

~ ~~ ~~Gel electrophoresis of DNA from 95 clinical isolates of Shigella sonnei and Shigella JIexneri resistant to antibiotics revealed a heterogeneous plasmid population. Most of the plasmids were smaller than 6 megadaltons (Mdal). Six S. sonnei isolates with the most common antibiotic resistance pattern were characterized. They had two plasmids in common : one was a self-transmissible Fif plasmid of 46 Mdal encoding tetracycline resistance, while the other was a 5.5 Mdal non-conjugative plasmid encoding resistance to streptomycin and sulphafurazole. In addition, several cryptic plasmids ranging in size from 1.0 to 24.5 Mdal were present. Mobilization of the 5.5 Mdal SuSm plasmid and a 1.0 Mdal cryptic plasmid was demonstrated with all six S. sonnei isolates during conjugation. This mobilization was mediated by the 46 Mdal self-transmissible Fif R plasmid and also by a 24-5 Mdal Fiplasmid carrying no known drug resistance determinants.

The aims of this study were to estimate carriage prevalence, identify factors predictive of carriage, and compare strains of Neisseria meningitidis isolated from patients with meningococcal disease and their household contacts. A total of 954 contacts of 160 patients had a nasopharyngeal swab and an interview relating to factors associated with carriage. The carriage prevalence was 20.4% for Neisseria meningitidis, 11.3% for serogroup B, and 2.6% for serogroup C. Age-standardised carriage was higher in Maori (36.8%) than in Pacific Island (21.5%) or European/other (11.1%) ethnic groups. Factors associated with carriage were smoking, with personal smokers (odds ratio [OR] 2.5) and passive smokers (OR 1.6) having a higher carriage risk than those in smoke-free houses; ethnicity, with Maoris having a higher carriage risk than those of non-Maori or non-Pacific Island ethnicity (OR 2.2); gender, with males at higher risk than females (OR 1.7); and age, with 0-4-year-olds less likely and 15-24-year-olds more likely to be carriers than those over 25 years. Strong patient-contact clustering by meningococcal strain (chi-square1 = 16.7, P=0.00004) suggested an important role for the household setting in transmission. The low carriage prevalence of serogroup B Neisseria meningitidis among household contacts may reflect its low transmissibility but high virulence. No direct relationship was found between prevalence of ethnic-specific carriage and the incidence of meningococcal disease.

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