Enterococcal urinary tract infections: eight years experience at a regional hospital in Trinidad, West Indies

OBJECTIVE: To investigate the prevalence of significant enterococcal isolates from urine and determine what factors are associated with the increased prevalence, with particular reference to antibiotic susceptibilities. METHODS: Retrospective analysis over an 8-year period of hospital laboratory records of urinary isolates of enterococci was done. Species were identified via colony morphology, growth in 6.5% sodium chloride and their ability to hydrolyze esculin in the presence of 40% bile salts. Susceptibility testing via the disc diffusion technique with 9 commonly used antibiotics was also done as defined by the National Committee for Clinical Laboratory Standards. RESULTS: From 39,881 urine specimens, 9116 (22.9%) were culture positive. Of this 9116, 1001 (11.0%) were enterococci, the 4th most common urinary isolate. E. coli was the most common (36.2%). Most enterococci were from pediatric patients (28.4%) and the urology unit (24.5%). All enterococci were fully sensitive to ampicillin and augmentin (amoxicillin-clavulanic acid). Sensitivity to gentamicin decreased significantly from 79% in 1990 to 58% in 1997 (P < 0.005). Sensitivity to the cephalosporins and nitrofuratoin were relatively stable, but sensitivity to nalidixic acid varied. No resistance to vancomycin was detected during the study, and no cases of bacteremia complicated bacteriuria were seen. CONCLUSION: Isolation of enterococci was relatively stable during the 8-year period, and all isolates were fully sensitive to the older beta-lactams, ampicillin, cefaclor and augmentin, but displayed varying degrees of multi-resistance to other commonly used urinary agents such as nalidixic acid and co-trimoxazole (trimethoprim-sulfamethoxazole). Because of the emergence of multi-resistant enterococci in many countries, and the high cost of drugs in our society, it is imperative that vigilance be maintained in monitoring enterococcal infections in hospitals.

An experimental mouse model to study the pathogenicity of Prevotella bivia and investigations of possible virulence

Induction of subcutaneous abscesses in mice was used to study the pathogenicity of Prevotella bivia both in mono-infection and in mixed cultures with Escherichia coli and Peptostreptococcus spp. Virulence factors such as coaggregation and aggregate formation of cells, haemagglutination activity and tolerance to serum bactericidal activity were investigated for their possible role in P bivia pathogenicity. Monocultures of P bivia, E coli and Peptostreptococcus spp did not induce subcutaneous abscess at concentrations as high as 10 9 colony forming units/millilitre (cfu/ml). Only E coli persisted at the infection site for up to 7 days post infection but with a marked decline in cell count (8.0x10 squaredcfu/ml). The anaerobic organisms did not persist at the infection sites beyond the fifth day. In contrast, mixed cultures of P bivia and E coli or all three organisms potentiated for infective abscess two weeks after infection. Viable cells were recovered from abscesses in greater numbers as the infection progressed. Prevotella bivia was the predominant organism in chronic abscesses while E coli predominated in abscesses in the acute stage of the infection. Prevotella bivia lacked haemagglutination activity against human and sheep erythrocytes and showed marked susceptibility to 50 percent human serum. These may limit its haematogenous spread. Its ability to form aggregates in molar salt solutions and coaggregate with facultative organisms may account for its persistence in pathological sites.(Au)

Latex agglutination in the aetiological diagnosis of bacterial meningitis - abstract

Bacterial meningitis causes significant mortality (5-15 per cent) and considerable morbidity (30-40 per cent), and delays in diagnosis and initiation of appropriate antimicrobial therapy can be devastating. The traditional microbiological procedures of Gram stain and culture could be rendered insensitive by the prior administration of antibiotics. Latex agglutination (LA) has been found to be more sensitive in these circumstances. In this prospective study from March to October, 1988, 193 CSF samples were evaluated by Gram stain, culture (horse blood agar at 37§C, supplemented chocolate agar, 37§C and 5 per cent CO2 and Levinthal broth), standard biochemical analysis and LA (Directigen Meningitis Combo test kit, Becton Dickenson Microbiology Systems). The medical records of the 193 patients were reviewed and 29 were diagnosed as having bacterial meningitis based on the history, signs, symptoms and CSF findings. The sensitivities of the LA, Gram stain and culture were 90 per cent, 42 per cent and 43 per cent respectively. The LA was far superior in sensitivity to Gram stain and culture and in this study identified 13 cases that were missed by Gram stain and culture. The LA test could be a valuable adjunct to the latter 2 tests in the aetiological diagnosis of bacterial meningitis (AU)