- Volume 50, Issue 1, 2001

Salicylate was shown to increase the frequency at which a fusidic acid-susceptible strain of Staphylococcus aureus underwent mutation to become fusidic acid-resistant. These fusidic acid-resistant mutants had alterations in spectinomycin and kanamycin resistance levels indicative of mutations in fusA, the gene that encodes elongation factor-G, the target of fusidic acid.

This study investigated the bactericidal capability of circulating neutrophils from blunt trauma patients admitted to an Intensive Care Unit against Staphylococcus aureus and Pseudomonas aeruginosa. Among those patients, two groups were considered and compared: patients who developed adult respiratory distress syndrome (ARDS) and patients who developed only pneumonia. Peripheral blood samples were drawn as soon as a diagnosis of pneumonia or ARDS was made, followed by the isolation of neutrophil cells and assessment of bacteria phagocytosis and killing. The results demonstrated that in patients with ARDS, phagocytosis and killing efficiency were significantly impaired in comparison with patients with pneumonia and healthy controls. A possible dysregulation of reactive oxygen species production involving the release of humoral mediators in early ARDS may be involved.

Shiga-like toxin-producing Escherichia coli O157 isolates were characterised by random amplification of polymorphic DNA by PCR (RAPD-PCR) analysis developed to allow robust epidemiological typing of E. coli. Amplification with primer 1247 or 1290 generated a reproducible profile, but was not capable of distinguishing sufficiently between epidemiologically unrelated strains. Subsequent digestion of the amplicons with selected restriction endonucleases improved the discriminatory ability of this method for strains showing limited differentiation following RAPD-PCR analysis alone. Restriction endonuclease analysis of RAPD-PCR fragments generated from closely related strains has the potential to provide additional discriminatory information without loss of specificity.

Leptospira fainei serovar Hurstbridge is a recently discovered Leptospira species and so far it has only been cultured from animal sources. Based on positive serology and positive PCR for L. fainei among patients suspected of having leptospirosis, a role in human disease seems likely. This study describes two patients with Weil's disease from whom L. fainei was cultured. A local source of the infections was suspected, as these two patients resided in the same area of Denmark, were hospitalised approximately at the same time and had not been travelling recently. The Leptospira species was determined by serology, PCR and sequencing of bacterial DNA. One patient developed autoimmune hepatitis in the course of the L. fainei infection and was treated with both antibiotics and immunosuppression with good effect. The other patient had a self-limiting disease and did not receive any treatment.

Following the coincidental discovery that β-actin isolated from renal epithelial cells was precipitated by staphylococcal protein A (SPA), the possibility that SPA and cytoskeletal actin filaments may be involved in Staphylococcus aureus infection of epithelial cells was considered. Therefore, to clarify the potential role of SPA and actin filaments in S. aureus infection, the invasion efficiency of S. aureus was determined quantitatively by measuring the number of cfu of viable organisms recovered from cultured KB cells. S. aureus invasion was found to be time dependent (0–60 min) and increased linearly when increasing numbers of bacteria were added (104–106 cfu/ml). However, significant variation in the level of invasion was noted in protein A-deficient S. aureus Wood 46. Cytochalasin B inhibited the invasion efficiency of S. aureus in a dose-dependent manner. The present study suggests that interaction of staphylococcal protein A and cytoskeletal actin filaments is involved in the S. aureus invasion of cultured KB cells, and this process may contribute, in part, to the intracellular movement, cell-to-cell spread and dissemination of S. aureus within human oral epithelial cells in vivo.

A collection of 70 clinical isolates of Acinetobacter baumannii from Bilbao in northern Spain was examined by PCR for the presence of class 1 integron structures. The organisms comprised 21 distinct RAPD genotypes, with 10 distinct antibiogram patterns. Four different integron structures were detected in a total of 59 (84%) of the 70 isolates, with two predominant integron structures found in 20 and 30 isolates each. No clear antibiogram differences could be correlated with the presence or absence of integron structures, but sequence analysis of two of the internal integron regions indicated homology with genes encoding ANT(2″) adenyltransferase activity and AAC(6′)-Ib acetyltransferase activity. Phenotypic analysis of aminoglycoside resistance profiles indicated that many isolates produced a combination of aminoglycoside-modifying enzymes, with most of the observed resistance to amikacin being associated with a gene encoding APH(3′)-VI phosphotransferase, as detected by PCR. RAPD analysis indicated that all the Bilbao isolates producing APH(3′)-VI were distinct from an epidemic integron-carrying and APH(3′)-VI-producing Acinetobacter strain found in other regions of Spain. It is concluded that, although class 1 integrons are widely disseminated amongst clinical isolates of A. baumannii from the Bilbao region of Spain, at present they are not playing a major role in the dissemination of antibiotic resistance genes in this region.

Earlier studies showed that Micrococcus luteus cells and cell walls induced anaphylactoid reactions leading to death, in some instances within 1 h, in C3H/HeN mice primed with muramyl dipeptide (MDP). They also induced serum cytokines in the surviving mice. The present study investigated the structural components responsible for these activities. Teichuronic acids, a component of M. luteus cell walls, induced tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in MDP-primed C3H/HeN mice. Peptidoglycans had little effect on the cytokine-inducing activities. Reducing teichuronic acids, i.e., teichuronic acids whose carboxyl groups had been reduced, lost their cytokine-inducing activities. Neither peptidoglycans nor teichuronic acids induced anaphylactoid reactions in the MDP-primed mice. Purified teichuronic acids also induced TNF-α and IL-6 production in C3H/HeN murine peritoneal macrophages and human whole-blood cells in the culture, but reduced teichuronic acids did not. The purified teichuronic acids induced no TNF-α and only low levels of IL-6 in MDP-primed C3H/HeJ mice, and neither cytokine in peritoneal macrophage cultures from C3H/HeJ mice with a single point of mutation in Toll-like receptor 4 (TLR4) gene. These findings suggest that induction of cytokines by teichuronic acids is mainly TLR4-dependent.

Subinhibitory concentrations of azoles are known to inhibit hyphal branching of Candida albicans in liquid media. This study showed that subinhibitory concentrations of fluconazole also inhibit agar invasion by C. albicans in YPD solid medium. Agar invasion was markedly inhibited in two C. albicans strains that were resistant to fluconazole. This suggests that the degree to which fluconazole inhibits agar invasion by C. albicans hyphae could serve as a marker of susceptibility to azoles.

The detection of specific IgM antibodies has been the most frequently used serological marker for diagnosing recent toxoplasmosis. However, the persistence of specific IgM antibodies in some patients and the use of tests with a low specificity have complicated the interpretation of serological results when toxoplasmosis is suspected. The purpose of the present study was to determine the value of newer serological techniques in the diagnosis of acute acquired toxoplasmosis. Sixty-four sera, 31 from patients with Toxoplasma gondii infection and 33 from patients with latent infection, were tested. Anti-T. gondii IgA was measured by two antibody capture ELISA tests (Platelia® Toxo IgA and ETI-TOXOK A) and an automated direct ELISA (IMx® Toxo IgA); all three assays detected antibody levels compatible with a recent infection in sera from all 31 patients with acute toxoplasmosis. However, significant levels of IgA were also detected with high frequency by all three assays in sera from patients with latent infection. IgE antibodies detected by IgE immunosorbent agglutination assay (ISAGA) were present in 26 (84%) of 31 patients with acute toxoplasmosis and in sera from two subjects with latent infection taken >1 year after the beginning of the clinical symptoms of infection. Thirty (97%) of 31 patients with a recent T. gondii infection and 15 (45%) of 33 subjects with latent infection had an AC/HS pattern compatible with acute toxoplasmosis. The avidity of T. gondii IgG was evaluated by two methods. One method was based on the titration of each serum sample and calculation of the titres, in the absence and presence of urea, in relation to a defined cut-off value. In the other method, a single serum dilution was used and the absorbances of the reactions in the presence and absence of urea were compared. The titration method was more sensitive for diagnosing recent primary infection; all 31 sera from patients with acute toxoplasmosis had avidity indices compatible with acute toxoplasmosis by the titration method, whereas with the single dilution method, sera from four patients had equivocal results. In the 33 individuals with latent infection, similar results were obtained with the two avidity methods; only one serum sample had a non-compatible avidity value with the titration method. The results obtained in the present study show that the current serological markers used for diagnosing acute acquired toxoplasmosis have significant limitations. The data suggest that determination of the avidity of T. gondii-specific IgG by the titration method in patients with detectable IgM antibodies defines most accurately the stage of infection by T. gondii.