The sensitivity to normal human serum of 91 smooth strains of Escherichia coli isolated from urinary tract infections was determined. Production of hemolysin, which was common and associated primarily with the types 04, 06, 018, and 075, was significantly correlated with high levels of serum resistance, both within the total population and within individual 0 types. In contrast, serum resistance was not significantly associated with antibiotic resistance (whether transmissible or not), with colicinogeny in general, or with colicin V production in particular. This indicates that the carriage of R and ColV plasmids, shown previously to be capable of conferring increased levels of serum resistance on individual strains of E. coli isolated from other sources, does not play an important part in determining the serum sensitivity of the E. coli population involved in urinary tract infection.

SUMMARY One thousand bacterial isolates from consecutive suprapubic aspirations of urine in two groups of patients with symptomatic urinary tract infection and two groups with asymptomatic bacteriuria were studied.Staphylococci accounted for 13 and 27 % of the isolates from symptomatic patients but for only 3 and 4 % of strains from asymptomatic bacteriuria. Conversely, 18 and 30 % of Escherichia coli isolates from asymptomatic bacteriuria were auto-agglutinable when tested with antisera to the common urinary 0-serogroups, whereas such strains accounted for only 5 and 7 % of the E. coli from symptomatic patients. The high prevalence of auto-agglutinable E. coli in asymptomatic bacteriuria was accompanied by a reduction in the frequency of the common urinary O-serogroups rather than other smooth strains.We have previously reported a high prevalence of coagulase-negative staphylococci in two groups of patients with symptomatic urinary tract infection (Bailey et al., 1971;Dove et al., 1972) but found only a low prevalence of such organisms when screening for asymptomatic bacteriuria in non-pregnant women . In a study of Escherichia coli isolates from schoolgirls (Olling et al., 1973), it was found that the seven 0-serogroups most commonly associated with symptomatic infections were much less frequent in asymptomatic bacteriuria and appeared to be replaced by autoagglutinable strains. More recently , we have presented evidence that, unlike the situation in pregnancy, in the non-pregnant woman symptomatic infections rarely arise from preexisting asymptomatic bacteriuria.These findings raise the question of the relative importance of bacterial and host factors in determining whether or not symptoms occur in the presence of bacteriuria. In this report 1000 isolates, from consecutive suprapubic aspirates of urine, are reviewed with regard to the symptomatic status of the patient. Patients and methodsFour groups of patients were included in the study. Patients attending the urinary infection clinics at

SUMMARY.The effects of ethyleneglycoltetra-acetic acid (EGTA) and EGTA+magnesium (MgEGTA) on the viable counts of 10 strains of Escherichia coli 0 6 have been studied in normal human serum (NHS), heat-inactivated serum (HIS) and in culture media with and without the addition of a fl-lactam antibiotic. The addition of EGTA to NHS largely prevented bactericidal activity against serum-sensitive strains while, in contrast, it reduced the growth of a serum-resistant strain. These apparently paradoxical effects are due to the lower growth rate permitted by the reduced amount of available magnesium in the presence of EGTA.Experiments with equimolar concentrations of EGTA and magnesium indicated that whilst MgEGTA is a reagent allowing alternative complement-pathway activity, such activity must be determined by comparison with results in HIS+MgEGTA rather than in HIS alone, classical-pathway activity being taken as the difference between the results in NHS and in NHS + MgEGTA.By these criteria, prompt killing by serum was found to occur via the classical pathway while delayed serum bactericidal activity occurred by the alternative pathway in some strains and by the classical pathway in others.

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The sensitivities to cefuroxime and cephaloridine were compared in 500 bacterial isolates from consecutive cases of urinary tract infection. In the first 200 organisms there was generally good correlation between the diameters of the zone of inhibition around a 30 microgram cefuroxime disc and the MICs. Correlation was poorest with streptococci. From the preliminary observations, criteria were derived to relate the disc sensitivities to MICs for all 500 strains. Neither cephalosporin had significant activity against Pseudomonas spp. but, apart from one strain of Klebsiella and one methicillin-resistant staphylococcus, the only bacteria sensitive to cephaloridine but resistant to cefuroxime were Str. faecalis. Of the 500 organisms, 45% were beta-lactamase-producing Gram-negative bacilli and, overall, cefuroxime was more active than cephaloridine against them. The greater stability of cefuroxime to the beta-lactamases from these bacilli were also supported by a smaller increase in MIC when the inoculum size was increased. On the basis of these results, cefuroxime should prove an effective choice for the treatment of most urinary tract infections.