C-reactive protein, metabolic syndrome and incidence of severe hip and knee osteoarthritis. A population-based cohort study

OBJECTIVE

To explore the relationships between C-reactive protein (CRP), metabolic syndrome (MetS) and incidence of severe knee or hip osteoarthritis (OA) in a prospective study.

METHODS

A population-based cohort (n=5171, mean age 57.5+/-5.9 years) was examined between 1991 and 1994. Data was collected on lifestyle habits, measures of overweight, blood pressure as well as high-density lipoprotein (HDL) cholesterol, triglycerides, glucose and CRP measured with high-sensitive methods. Incidence of severe OA, defined as arthroplasty due to knee or hip OA, was monitored over 12 years of follow-up, in relation to CRP levels and presence of the MetS according to the adult treatment panel III-national cholesterol education program (ATPIII-NCEP) definition.

RESULTS

A total of 120 participants had severe hip OA and 89 had knee OA during the follow-up. After adjustment for age, sex, smoking, physical activity and CRP, presence of MetS was associated with significantly increased risk of knee OA (relative risk [RR]: 2.1, 95% confidence interval [CI]: 1.3-3.3). However, this relationship was attenuated and non-significant after adjustment for body mass index (BMI) (RR: 1.1, 95% CI: 0.7-1.8). MetS was not significantly associated with incidence of hip OA. In women, CRP was associated with knee OA in the age-adjusted analysis. However, there was no significant relationship between CRP and incidence of knee or hip OA after risk factor adjustments.

CONCLUSION

The increased incidence of knee OA in participants with the MetS was largely explained by increased BMI. CRP was not associated with incidence of knee or hip OA when possible confounding factors were taken into account.

Incidence of severe knee and hip osteoarthritis in relation to different measures of body mass: a population-based prospective cohort study

OBJECTIVE

To determine in a prospective population-based cohort study relationships between different measures of body mass and the incidence of severe knee and hip osteoarthritis defined as arthroplasty of knee or hip due to osteoarthritis.

MATERIALS AND METHODS

Body mass index (BMI), waist circumference, waist-hip ratio (WHR), weight and percentage of body fat (BF%) were measured at baseline in 11,026 men and 16,934 women from the general population. The incidence of osteoarthritis over 11 years was monitored by linkage with the Swedish hospital discharge register.

RESULTS

471 individuals had knee osteoarthritis and 551 had hip osteoarthritis. After adjustment for age, sex, smoking and physical activity, the relative risks (RR) of knee osteoarthritis (fourth vs first quartile) were 8.1 (95% CI 5.3 to 12.4) for BMI, 6.7 (4.5 to 9.9) for waist circumference, 6.5 (4.6 to 9.43) for weight, 3.6 (2.6 to 5.0) for BF% and 2.2 (1.7 to 3.0) for WHR. Corresponding RR for hip osteoarthritis were 2.6 (2.0 to 3.4) for BMI, 3.0 (2.3 to 4.0) for weight, 2.5 (1.9 to 3.3) for waist, 1.3 (0.99 to 1.6) for WHR and 1.5 (1.2 to 2.0) for BF%.

CONCLUSION

All measures of overweight were associated with the incidence of knee osteoarthritis, with the strongest relative risk gradient observed for BMI. The incidence of hip osteoarthritis showed smaller but significant differences between normal weight and obesity. Our results support a major link between overweight and biomechanics in increasing the risk of knee and hip osteoarthritis in men and women.

Cutaneous delayed-type hypersensitivity reactions in smokers with chronic bronchitis and recurrent exacerbations: comparison with asymptomatic smokers and never-smokers

The aim of the present study was to investigate whether smoking patients with chronic bronchitis (CB) and recurrent exacerbations show signs of depressed cell-mediated immunity (CMI), as reflected in the cutaneous delayed-type hypersensitivity (DTH) reaction, in comparison with asymptomatic smokers and healthy never-smokers. The study was a comparative clinical study performed at a university hospital center of respiratory medicine. Sixteen smokers with stable CB and recurrent exacerbations, five of whom had mild airflow obstruction, 18 asymptomatic smokers and 18 healthy never-smokers, all aged between 35 and 64 years, participated. No subjects treated with corticosteroids or N-acetylcysteine were included. Cutaneous DTH-reactions to seven recall antigens were assessed with Multitest, a standardized in vivo test of clinical CMI. Reactions were assessed 48 h after application by measurement of skin induration. A score (sum in mm of positive reactions) was created to assess overall reactivity. Neither the score nor the number of positive reactions differed significantly between the three study groups. Men had a significantly higher reactivity than women (P < 0.05) irrespective of group affiliation. No influence of smoking status on DTH reactivity could be seen. In the CB group no correlation was found between DTH reactivity and number of exacerbations the past 2 years. Patients with chronic bronchitis and recurrent exacerbations did not differ from asymptomatic smokers or healthy never-smokers with respect to cutaneous DTH reactions. Depression of CMI, as measured in this study, does not seem to be a primary factor behind recurrent exacerbations in smokers with CB.

Immunological findings in blood and bronchoalveolar lavage fluid in chronic bronchitis patients with recurrent infectious exacerbations

Bronchial infections are common in smokers and seem to be related to the presence of chronic bronchitis (CB). Why only some smokers develop repeated bronchial infections is not known. The aim of this study was to screen for immunological changes associated with disease in patients with CB and recurrent infectious exacerbations compared to asymptomatic smokers. Sixteen smokers with stable CB and recurrent infectious exacerbations, and 18 asymptomatic smokers, all without any immunomodulating treatment, underwent bronchoscopy and bronchoalveolar lavage (BAL). Smoking history and current smoking status were comparable. Serum levels of immunoglobulin (Ig)A, IgM, IgG and IgG subclasses were measured. Blood and BAL lymphocyte phenotypes and proliferative responses of peripheral blood mononuclear cells (PBMCs) to various stimulators were analysed. Unstimulated and tetanus toxoid-stimulated production of cytokines in PBMC cultures was measured. Natural killer (NK-) cell activity was analysed. A significantly (p<0.05) lower level of IgG3 was found in the CB group, and a significantly (p<0.01) higher proliferative response of PBMCs was found in the CB group after stimulation with diphtheria toxoid. Detectable levels of interleukin (IL)-6, tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma, but not of IL-2, IL-4 or transforming growth factor-beta2, were found in supernatants from cultured cells in both study groups. Stimulated TNF-alpha production was significantly (p<0.05) higher in the CB group. NK-cell activity did not differ significantly between the study groups. There were no major differences between the groups in lymphocyte subpopulations in blood or BAL. In conclusion, no major alterations in the analysed indices of cell-mediated and humoral immunity were found in patients with chronic bronchitis prone to recurrent infectious exacerbations when compared with asymptomatic smoking controls.

Supernatants from Staphylococcus epidermidis grown in the presence of different antibiotics induce differential release of tumor necrosis factor alpha from human monocytes

Bacterial products from gram-positive bacteria, such as peptidoglycan, teichoic acid, and toxins, activate mononuclear cells to produce tumor necrosis factor alpha (TNF). The present study evaluated the release of soluble cell wall components from Staphylococcus epidermidis capable of inducing TNF after exposure of the bacteria to various antibiotics. A clinical S. epidermidis isolate (694) was incubated with either penicillin, oxacillin, vancomycin, or clindamycin at five times the MIC. Supernatants of the cultures obtained by filtration were added to plastic adherent monocytes in the absence or presence of human serum. After 18 h of incubation, monocyte supernatants were tested for the presence of TNF by enzyme-linked immunosorbent assay (ELISA). Supernatants from bacteria incubated with beta-lactam antibiotics induced higher TNF levels than those obtained from bacteria incubated with culture medium only (no antibiotics), vancomycin, or clindamycin. Human serum potentiated supernatant-induced TNF release, especially in beta-lactam supernatants. The soluble peptidoglycan and teichoic acid contents of supernatants, as estimated by inhibition ELISA and, for peptidoglycan, also by affinity depletion with vancomycin-Sepharose gel, were proportional to TNF release. Differences in the ability of individual antibiotics to generate TNF-releasing products from S. epidermidis were observed, the most potent antibiotics being penicillin and oxacillin.

Intracellular pathways involved in tumor necrosis factor-alpha release by human monocytes on stimulation with lipopolysaccharide or staphylococcal peptidoglycan are partly similar

This study compared the effects of intracellular pathway inhibitors on tumor necrosis factor-alpha (TNF-alpha) release from human monocytes. Cells were stimulated with peptidoglycan (PG) from Staphylococcus epidermidis or with Escherichia coli lipopolysaccharide (LPS), both in the presence of 10% human serum. Of 10 substances tested, only the protein tyrosine kinase inhibitor tyrphostin AG 126 discriminated significantly between PG and LPS: TNF-alpha release induced by PG, but not by LPS, was dose-dependently suppressed. The results obtained with other modulatory substances, including different protein kinase and G protein inhibitors, suggest that calmodulin-dependent protein kinase, protein tyrosine kinase, and a cholera-toxin-sensitive G protein are involved in both PG- and LPS-induced TNF-alpha release. Further, drugs such as pentoxifylline, chloroquine, and the antioxidant apocynin similarly inhibited TNF-alpha release by PG- as well as LPS-stimulated cells.

Comparative antibacterial activity of L-695,256, a carbapenem active against methicillin-resistant staphylococci

The activity of a new prototype carbapenem, L-695,256, against clinical isolates of gram-positive and gram-negative aerobes was studied in vitro by agar dilution. L-695,256 was highly active against methicillin-resistant and -susceptible isolates of staphylococci (MICs, 0.016 to 2 micrograms/ml) and against penicillin-resistant pneumococci (MICs, 0.016 to 0.064 micrograms/ml), irrespective of penicillin susceptibility. Activity against members of the family Enterobacteriaceae was less than that of imipenem, while Proteus mirabilis and Morganella morganii were more susceptible to L-695,256.

Serum-induced potentiation of tumor necrosis factor alpha production by human monocytes in response to staphylococcal peptidoglycan: involvement of different serum factors

Peptidoglycan from a Staphylococcus epidermidis strain, isolated from a patient with septicemia, was preincubated with human serum. This mixture was then investigated for its potency to induce tumor necrosis factor (TNF) secretion by human blood monocytes. TNF was measured in the supernatants by using a bioassay and/or an enzyme-linked immunosorbent assay specific for TNF alpha (TNF-alpha). Although earlier studies indicated that staphylococcal peptidoglycan alone is a relatively poor stimulator of TNF-alpha production, the present study shows that human serum highly potentiates peptidoglycan-induced TNF-alpha release by human monocytes. In the presence of serum and in the low-dose range, peptidoglycan was almost as potent as endotoxin. At high peptidoglycan concentrations, monocytes showed an extremely high TNF-alpha response, but again only in the presence of serum. At low peptidoglycan doses, the stimulatory effect of serum was abrogated by heat treatment or depleting serum of complement components C1 and C3/C4, which suggests a role for the classical complement pathway. At high doses of peptidoglycan, the serum stimulatory effect depended mainly on immunoglobulin G.

Analysis of immunoglobulin isotype levels in acute pneumococcal bacteremia and in convalescence

In 48 patients with a history of a pneumococcal bacteremia, serum taken during the acute phase of the infection was analyzed for IgG and IgG subclasses. Once the patients were free of infection, a serum sample was analyzed for IgG, IgG subclasses, IgA and IgM. In an additional 20 patients, it was only possible to analyze serum from the infection-free phase. Seventeen of 48 (35%) patients had reduced levels of total IgG or of one or more of the IgG subclasses during acute disease. Of the 48 patients in whom both acute phase and infection-free phase serum were analyzed, values of IgG (p < 0.001), IgG1 (p < 0.001), IgG2 (p < 0.001), IgG3 (p < 0.01) and IgG4 (p < 0.01) were decreased during the acute infection. During the infection-free phase, 12 of 68 (18%) patients had a recognizable immunodeficiency, including two patients with common variable immunodeficiency. Routine screening for immunoglobulins during the infection-free period could result in the discovery of previously unrecognized immunoglobulin deficiencies in patients with a history of bacteremic pneumococcal infection.

Peptidoglycan and teichoic acid from Staphylococcus epidermidis stimulate human monocytes to release tumour necrosis factor-alpha, interleukin-1 beta and interleukin-6

Cytokines play a major role in the pathophysiology of septic shock. In this study, human peripheral blood monocytes were stimulated with peptidoglycan and teichoic acid, purified from a strain of Staphylococcus epidermidis. Polymyxin B (PM-B) was added to avoid the effects of possible contamination with endotoxin. Tumour necrosis factor-alpha (TNF), interleukin-1 beta (IL-1), and interleukin-6 (IL-6) in the supernates were measured by enzyme-linked immunosorbent assays. Peptidoglycan and teichoic acid induced TNF, IL-1, and IL-6 in a concentration-dependent manner. Teichoic acid was a weaker inducer than peptidoglycan, especially for IL-1. Lipopolysaccharide from an E. coli strain was used as a control, being 100-1000 times more potent than peptidoglycan and teichoic acid.

Neurologic adverse effects during concomitant treatment with ciprofloxacin, NSAIDS, and chloroquine: possible drug interaction

OBJECTIVE

To report a case of neurologic adverse effects that developed during concomitant treatment with ciprofloxacin, nonsteroidal antiinflammatory drugs (NSAIDs), and chloroquine. Possible mechanisms for a drug interaction are discussed.

CASE SUMMARY

A 68-year-old woman who was receiving chronic treatment with NSAIDs and chloroquine developed dizziness, anxiety, and tremors when ciprofloxacin 500 mg twice daily was begun for Salmonella osteitis. When she discontinued the antirheumatic treatment, there was a prompt relief of symptoms. After indomethacin was reintroduced, the patient developed signs and symptoms of peripheral neuropathy, which partially subsided when ciprofloxacin was discontinued.

DISCUSSION

Enhanced neurologic adverse effects of ciprofloxacin when taken together with NSAIDs or chloroquine may result from reduced effects of gamma-aminobutyric acid. An alternative explanation could be that NSAIDs and chloroquine impair the elimination of ciprofloxacin, thereby contributing to toxic concentrations of the antibiotic.

CONCLUSIONS

The possibility of interactions between ciprofloxacin and antirheumatic drugs should be considered.

Bronchoscopic diagnosis of pulmonary infections in a heterogeneous, nonselected group of patients

Fiberoptic bronchoscopy with bronchoalveolar lavage and protected specimen brush technique has become an established method for etiologic diagnosis in severe forms of pulmonary infections during recent years. In this study, including 62 bronchoscopies in 53 patients, a standardized program, covering all important pulmonary pathogens, has been evaluated in a heterogeneous group of patients. Results providing therapeutic guidelines were obtained in 53 percent (16/30) of the immunocompromised patients (including 5 bronchoscopies on HIV-positive patients), but only 19 percent (6/32) of the immunocompetent patients (p < 0.001). We conclude that bronchoscopy is of great value for diagnosing pulmonary infections in immunocompromised patients. In immunocompetent patients, the diagnostic yield is lower and the indication for bronchoscopy must be established for each individual patient based on clinical importance, resources, and risk. When bronchoscopy is performed, we believe that a standardized program like ours reduces the risk of missing important pathogens.

Characterization and distribution of Pasteurella species recovered from infected humans

During a 3-year period, all Pasteurella strains recovered at the Clinical Microbiological Laboratory, Lund, Sweden, were studied biochemically with respect to their relationship to the recently described taxa of this genus. Of 159 strains recovered from 146 infected humans, 95 were identified as Pasteurella multocida subsp. multocida, 21 as Pasteurella multocida subsp. septica, 28 as Pasteurella canis, 10 as Pasteurella stomatis, and 5 as Pasteurella dagmatis. The homology within and between the Pasteurella species regarding cellular fatty acids and enzymatic activities was also studied. Strains of the different Pasteurella species were indistinguishable from each other regarding fatty acid composition; all strains contained major amounts of C14:0, C16:1, C16:0, and 3-OH-C14:0 acids and minor amounts of C18:2, C18:1, and C18:0 acids. Neither did the enzymatic activities distinguish between strains belonging to different species. In addition, of 56 strains examined, toxin production was demonstrated only in 1 strain each of P. multocida subsp. multocida and P. canis. Except for one severe case of necrotizing cellulitis involving P. dagmatis, P. multocida subsp. multocida or P. multocida subsp. septica was recovered in the more serious cases of infection. Except for P. canis, which in all cases was associated with dog bites, most Pasteurella strains were recovered in cases of infection associated with cat bites or scratches. Pasteurella strains occurred in four infected patients without evident connections with animals.

In vivo processing of Staphylococcus aureus lipase

The Staphylococcus aureus lipase gene encodes a 76-kDa protein. Extracellular lipase purified from culture supernatants is only 45 to 46 kDa, however. We show that the lipase is secreted in vivo as an 82-kDa protein with full enzymatic activity. It is then sequentially processed, both in culture and in cell-free supernatants, to a mature, 45- to 46-kDa protein. Protein sequencing demonstrates that the N-terminal region of the 82-kDa prolipase, comprising 295 amino acids, is cleaved from the central and C-terminal moieties, which contain the active site. A metallocysteine protease is probably responsible for initiating this processing. The extremely hydrophobic, mature lipase is resistant to further protease degradation and retains the full catalytic activity of the prolipase.

Antibody response to Staphylococcus aureus whole cell, lipase and staphylolysin in patients with S. aureus infections

Three assays to measure antibodies against Staphylococcus aureus whole cells, lipase and staphylolysin were used to try to discriminate between complicated and uncomplicated S. aureus septicaemia. Sera were examined from 8 patients with S. aureus endocarditis, 23 patients with complicated S. aureus septicaemia, 12 patients with uncomplicated S. aureus septicaemia and 93 febrile non-septicaemic controls. No single assay could distinguish between complicated and uncomplicated S. aureus septicaemia. If the criterion for a positive result is defined as positive antibody level in the anti-lipase ELISA as well as in at least 1 of the other 2 assays, 10/31 patients with S. aureus endocarditis or complicated septicaemia were positive compared to 0/93 non-septicaemic patients and 0/12 patients with uncomplicated S. aureus septicaemia. Therefore, the combined use of serological assays in the diagnosis of complicated S. aureus septicaemia, one of which is the anti-lipase ELISA, is recommended.

Severe Pasteurella multocida infections in pregnant women

We report 2 cases of severe infections due to Pasteurella multocida, both occurring during pregnancy in previously healthy women. Both women had contact with animals (dog and cat) but neither of them had been bitten. Apart from a slight decrease in IgG levels, no immunological defects could be detected. Both women had received oral phenoxymethylpenicillin in the early phase of the disease, but still fell ill with severe infections. One woman had meningitis while the other suffered from cellulitis with deep abscess formation.

Recurrent pneumonia: a review of 90 adult patients

Recurrent pneumonia is still an important problem. In this retrospective study we reviewed the records of 90 patients with a history of 3 or more episodes of acute pneumonia. The 90 patients accounted for altogether 347 episodes of acute pneumonia, treated at the Department of Infectious Diseases, Lund. 12 patients died while being treated for pneumonia at the department. Pneumonia alone caused the death in 7 of these 12 patients. In all, 51 of the patients died during the 11-year study period. Death certificates, stating the cause of death, were available in 38 cases, and pneumonia was the direct cause of death in 15 patients. Most of the infections were community-acquired, only 47 were nosocomial, 20/90 patients suffered from disorders associated with immune deficiency, and 70 patients had other predisposing illnesses. We found a larger number of underlying immunoglobulin deficiencies (11 patients of 38 investigated) than previously reported. Of 13 patients without other known, predisposing conditions, hypogammaglobulinemia was found in 3 patients. We suggest that patients with recurrent pneumonia should be thoroughly investigated, in order to find previously unrecognized immune deficiency.

Aggregation of human granulocytes by Staphylococcus aureus lipase

The effects of purified extracellular lipase from Staphylococcus aureus on human granulocytes were studied in vitro with a turbidimetric technique. Within the concentration range 0.6-4.4 micrograms/ml, lipase caused monophasic aggregation accompanied by the release of lactoferrin; the corresponding concentrations of the solvent in which it was suspended, Triton X100, had no effect. Lipase-induced aggregation did not occur in the presence of autologous plasma.

Influence by staphylococcal lipase on granulocyte metabolism and killing of bacteria

Lipase purified from Staphylococcus aureus interferes with granulocyte phagocytic killing of S. aureus but not with killing of Streptococcus pneumoniae or Streptococcus agalactiae group B. Lipase treatment of granulocytes did not influence bacterial adherence to the cells.

Are tumor necrosis factor (TNF) or cortisol of value for the diagnosis of acute septicemia?

Early diagnosis is of great importance to improve the prognosis of septicemia. Traditional laboratory tests are either delayed like blood cultures, or unspecific like WBC count or ESR. In this retrospective pilot study we have assayed plasma cortisol, blood sugar and serum tumor necrosis factor (TNF) from patients with verified septicemia. With the approach used in this study none of the tests were able to differentiate between septicemia and other infectious febrile illnesses, or to predict if the causing organism was gram-positive or gram-negative.

In vitro activities of cefcanel and some other cephalosporins against Pasteurella multocida

Thirty-five strains of Pasteurella multocida from humans and animals were tested for susceptibility to five cephalosporins by a broth dilution method. Cefcanel showed high activity against all isolates (MIC and MBC, less than or equal to 0.64 micrograms/ml). The corresponding figure for cefaclor and cefuroxime was 2.56 micrograms/ml. Cefadroxil and cephalexin were the least active compounds tested.

Crystal violet binding, cell surface properties and extracellular enzyme profiles of Staphylococcus aureus producing toxic shock syndrome toxin-1

Staphylococcus aureus isolated from clinically diagnosed cases of toxic shock syndrome (TSS) showed susceptibility to phage types belonging to both I and III groups (90.5%). Phage typing patterns showed a wide diversity among 87 toxic shock syndrome toxin-1 (TSST-1) positive strains isolated from different non TSS clinical sources. Toxin producing strains isolated from both TSS and non TSS showed a remarkable ability to bind to crystal violet (pattern C/D, 97.2%) incorporated into brain heart infusion agar media at subinhibitory concentrations and these isolates were traced to biotype var. hominis. The cellular fatty acid compositions of TSS and non-TSS strains belonging to the three biotypes S. aureus var. hominis, S. aureus var. bovis and S. aureus var. canis did not differ. TSST-1 producing strains demonstrated a high salt aggregation test value (above 1.5) indicating a low cell surface hydrophobicity. Both TSS and non TSS strains demonstrated a high lipolytic activity. TSST-1 positive strains in general, showed significantly higher lipase activity than strains isolated from septicemia (p less than 0.0001) and superficial (p less than 0.0001) infections. The proteolytic activity is higher among TSS (median value 0.075 U/ml) than to non TSS (median value 0.045 U/ml) strains. There was no correlation with the quantity of toxin production in vitro and to the properties described.

A comparative study of two lipases from different strains of Staphylococcus aureus

In order to compare lipases from two different Staphylococcus aureus strains (FN 37 and TEN 5), the enzymes from the respective strains were purified using octyl-Sepharose chromatography and characterized with regard to chemical, immunological and enzymatic properties. Differences in the size of the lipases in their native forms necessitated modifications of the purification process, but after purification identical subunits of about 43 kD were found in SDS-PAGE, and both lipases had an apparent molecular weight of 110 kD when subjected to gel chromatography on Sephadex G-200. Analysis of the amino acid compositions of the lipases showed considerable differences. Serine was the predominant amino acid in the FN 37 lipase, whereas glycine was most abundant in the TEN 5 lipase. Nevertheless, the two lipases were similar when tested with double immune diffusion against an antiserum raised against the TEN 5 lipase, and inactivation of enzyme activities by the antiserum followed the same patterns. Enzymatically, the enzymes were similar with regard to salt inhibition, ion dependency and heat inactivation. The substrate specificities, tested against glyceride substrates, were similar. Thus, the two staphylococcal lipases seem to be similar but not identical.

Pasteurella multocida occurs in a high frequency in the saliva of pet dogs

Pasteurella multocida is a frequent cause of infection after animal bites. In contrast to earlier reports, P. multocida appeared to be as common among dogs as among cats. We found 17 (81%) of 21 pet dogs to harbour P. multocida in their saliva. At normal contact, the risk of transmission from dogs to humans seems to be negligible. Only 1/27 dogs owners was found to harbour the organism. None of 13 cat owners or 23 persons without animal contacts harboured P. multocida.

The Tween 80 reaction does not correlate to triglyceride lipase production of Staphylococcus aureus

This comparison of Tween 80 reaction with triglyceride lipase production comprises 357 Staphylococcus aureus strains from various clinical sources. Tween 80 is a water-soluble substrate, and thus estimates esterase activity. Lipase production was assayed using water-insoluble substrates (radiolabelled triglyceride emulsions). Only a minor proportion of Tween 80-positive strains had significant triglyceride lipase production (greater than 5 mU/10(9) bacteria). The discrepancy between the two methods was most pronounced in subgroups of samples with low frequency of lipase production, e.g. from isolates from superficial locations such as nasal mucosa and impetigo. Owing to its low specificity, the Tween 80 reaction therefore seems unsuitable as a marker for lipase activity in clinical isolates of Staphylococcus aureus.

Interference of Staphylococcus aureus lipase with human granulocyte function

The influence of purified Staphylococcus aureus lipase on granulocyte function and morphology was studied. The lipase itself was strongly chemotactic; in addition preincubation of granulocytes with low concentrations of lipase enhanced the directed movement, as assayed in the agarose system. Higher concentrations of lipase, in contrast, gave a progressive reduction of granulocyte chemotaxis; at 12 micrograms lipase per ml, cells were almost immobilized. Phagocytic killing of Staphylococcus aureus by granulocytes preincubated with lipase was reduced in a dose-dependent manner. At 12 micrograms lipase per ml almost no staphylococcal killing occurred. This was mainly accounted for by a reduction of bacterial uptake, but some decrease in intragranulocytic killing was also noted. These functional alterations, which can all be ascribed to an interference with membrane functions, were associated with marked changes of the granulocyte surface structure, which was denuded and lacked normal microvilli. The effects of lipase were partly retained after heat inactivation of lipase activity, indicating that the effects of staphylococcal lipase on granulocyte function are not due to enzymatic activity alone. These effects of lipase may be an important virulence factor and contribute to the preferential location of lipase-producing Staphylococcus aureus strains at deep sites of infection.

Positional specificity and substrate preference of purified Staphylococcus aureus lipase

We have studied the substrate preference and specificity, including positional specificity, of a lipase purified from Staphylococcus aureus (strain FN 37). This extracellular bacterial enzyme is relatively insensitive to product inhibition, and hydrolyzes tri-, di- and monooleoylglycerol in emulsified and micellar form at similar rates and without marked substrate preference. The lipase lacks positional specificity, and the hydrolysis of triacylglycerol proceeds rapidly to free fatty acid and glycerol without accumulation of intermediary products.

Purification and characterization of a lipase from Staphylococcus aureus

An extracellular lipase from Staphylococcus aureus (strain FN 37) was purified to homogeneity. A cell-free culture broth was subjected to ammonium sulphate precipitation, and the lipase was isolated from the resuspended pellet by adsorption chromatography on octyl-Sepharose. The purification was 957-fold, and the recovery of the octyl-Sepharose chromatography was about 100%. The specific activity of the purified lipase was 546 mU of lipase activity per micrograms protein. The purity of the final product was documented by SDS-polyacrylamide gel electrophoresis in which a homogeneous protein band of 43 kDa was found. In gel chromatography on Sephadex G-200 the lipase eluted as a homogeneous peak with an apparent molecular mass of 110 kDa, suggesting that the lipase may exist as an oligomer in physiological media. Analysis of the amino-acid composition revealed a predominance of polar, non-charged amino acids, with serine accounting for 24 mol% of the amino-acid residues.

Lipolytic activity of Staphylococcus aureus strains from disseminated and localized infections

Lipase production of 425 S. aureus strains isolated from patients with different clinical diagnoses and healthy carriers were measured by a specific method, using emulsified trioleoylglycerol substrate. Strains isolated from patients with septicemia showed significantly higher lipase activity than osteomyelitis strains (p = 0.011), impetigo strains (p = 0.002) and strains isolated from healthy relatives of patients with recurrent furunculosis (p = 0.019). Recurrent furunculosis and pyomyositis strains had significantly higher (p = 0.002 and 0.032, respectively) lipase activity than septicemia strains. S. aureus strains isolated from patients with a significant antibody response in an antilipase ELISA did not show a higher lipase activity in culture supernatants than strains from patients without a significant antibody response. The lipase activity was significantly higher in strains isolated from deep or subcutaneous infections, i.e., septicemia, pyomyositis, osteomyelitis, aerobic and anaerobic furunculosis, than in strains from superficial infections, i.e. impetigo, or from nasal mucosa.

A simple turbidimetric method for specific measurement of Staphylococcus aureus lipase activity

We have developed a simple semiquantitative method for measuring Staphylococcus aureus lipase activity. Enzymatic activity is measured as the decrease in spectrophotometric absorbancy in a lipid emulsion after incubation with the sample. The sensitivity, precision and accuracy are adequate for routine purposes. The assay is rapid and simple and does not require advanced technical equipment.