Bertil Christensson

Biofilm formation by Propionibacterium acnes is a characteristic of invasive isolates

Propionibacterium acnes is a common and probably underestimated cause of delayed joint prosthesis infection. Bacterial biofilm formation is central in the pathogenesis of infections related to foreign material, and P. acnes has been shown to form biofilm both in vitro and in vivo. Here, biofilm formation by 93 P. acnes isolates, either from invasive infections (n = 45) or from the skin of healthy people (n = 48), was analysed. The majority of isolates from deep infections produced biofilm in a microtitre model of biofilm formation, whereas the skin isolates were poor biofilm producers (p <0.001 for a difference). This indicates a role for biofilm formation in P. acnes virulence. The type distribution, as determined by sequencing of recA, was similar among isolates isolated from skin and from deep infections, demonstrating that P. acnes isolates with different genetic backgrounds have pathogenic potential. The biofilm formed on plastic and on bone cement was analysed by scanning electron microscopy (EM) and by transmission EM. The biofilm was seen as a 10-mum-thick layer covering the bacteria and was composed of filamentous as well as more amorphous structures. Interestingly, the presence of human plasma in solution or at the plastic surface inhibits biofilm formation, which could explain why P. acnes primarily infect plasma-poor environments of, for example, joint prostheses and cerebrospinal shunts. This work underlines the importance of biofilm formation in P. acnes pathogenesis, and shows that biofilm formation should be considered in the diagnosis and treatment of invasive P. acnes infections.

Heparin-Binding Protein: An Early Marker of Circulatory Failure in Sepsis

BACKGROUND The early detection of circulatory failure in patients with sepsis is important for successful treatment. Heparin-binding protein (HBP), released from activated neutrophils, is a potent inducer of vascular leakage. In this study, we investigated whether plasma levels of HBP could be used as an early diagnostic marker for severe sepsis with hypotension. METHODS A prospective study of 233 febrile adult patients with a suspected infection was conducted. Patients were classified into 5 groups on the basis of systemic inflammatory response syndrome criteria, organ failure, and the final diagnosis. Blood samples obtained at enrollment were analyzed for the concentrations of HBP, procalcitonin, interleukin-6, lactate, C-reactive protein, and the number of white blood cells. RESULTS Twenty-six patients were diagnosed with severe sepsis and septic shock, 44 patients had severe sepsis without septic shock, 100 patients had sepsis, 43 patients had an infection without sepsis, and 20 patients had an inflammatory response caused by a noninfectious disease. A plasma HBP level > or = 15 ng/mL was a better indicator of severe sepsis (with or without septic shock) than any other laboratory parameter investigated (sensitivity, 87.1%; specificity, 95.1%; positive predictive value, 88.4%; negative predictive value, 94.5%). Thirty-two of the 70 patients with severe sepsis were sampled for up to 12 h before signs of circulatory failure appeared, and in 29 of these patients, HBP plasma concentrations were already elevated. CONCLUSION In febrile patients, high plasma levels of HBP help to identify patients with an imminent risk of developing sepsis with circulatory failure.

Interferon-α and Ribavirin Treatment of Hepatitis C in Children with Malignancy in Remission

Twenty-eight cases of hepatitis C virus (HCV) infection were identified in children in a pediatric oncology ward during 2 nosocomial outbreaks. HCV infection spontaneously cleared in 6 patients (21%). Eleven patients with persistent HCV viremia who had malignant diseases in remission after treatment were given a 48-week course of combined therapy with interferon-alpha (5x106 U 3 times weekly) and oral ribavirin (15 mg/kg/d). Seven (64%) of the 11 patients had sustained virological responses 6 and 12 months after cessation of therapy. Side effects were common but generally were mild or moderate.

Low Antibody Levels against Cell Wall-Attached Proteins of Streptococcus pyogenes Predispose for Severe Invasive Disease

Acute-phase serum samples from 70 patients with group A streptococcal (GAS) invasive disease were analyzed for IgG antibodies against 6 recently characterized GAS virulence factors (SclA, SclB, GRAB, MtsA, EndoS, and IdeS) and SpeB. Antibody levels against the cell wall-attached GAS antigens SclA, SclB, and GRAB were significantly lower in patients with severe invasive disease (streptococcal toxic shock syndrome [STSS] and/or necrotizing fasciitis [NF]; n=35), compared with levels in patients with nonsevere GAS bacteremia (n=35). Among patients with severe invasive disease, significantly lower antibody levels against GRAB were found in patients with STSS (n=10) than in patients with NF (n=17). Antibody levels against SpeB in patients with severe bacteremia were similar to those in patients with nonsevere bacteremia, and levels in patients with STSS were similar to those in patients with NF. The data indicate that immunity to cell wall-attached proteins may play a role in the protection against severe invasive disease and that antibodies against GRAB may be of importance in the pathogenesis of STSS.

Serum S100B levels in patients with cerebral and extracerebral infectious disease

S100B has been shown to increase in cerebrospinal fluid (CSF) and serum after various neurological diseases and it has been postulated that S100B could serve as a serum marker for brain damage. However there is limited information concerning serum S100B levels in infectious diseases of the brain. Blood samples were collected from patients at the Department of Infectious Diseases at or soon after admission. The different diagnoses studied were bacterial meningitis, pneumonia, viral meningitis, cerebral abscess, enteritis, erysipelas, viral encephalitis and neuroborreliosis. A serum S100B level >0.15 μg/l was defined as increased. 57 patients were included in the study. S100B was elevated in 33% of patients (19/57). 73% (8/11) of patients with bacterial meningitis showed increased levels compared to 7% (1/14) of patients with viral meningitis. Viral encephalitis showed the highest mean S100B levels (mean 0.58 μg/l). 25% (6/24) of patients with extracerebral infections showed raised S100B levels. S100B levels were generally higher in patients with cerebral infections than in extracerebral infections. However, both false negative and false positive S100B levels were observed which may limit the use of S100B as a brain specific serum marker.

Expression of Collagen-Binding Protein and Types 5 and 8 Capsular Polysaccharide in Clinical Isolates of Staphylococcus aureus

In vitro collagen binding of 216 Staphylococcus aureus isolates from patients with various diagnoses was studied. Polymerase chain reaction was used to examine these isolates regarding the existence of the corresponding cna gene. Distribution of capsular polysaccharide (CP) types was examined. Fifty-six (57%) of 99 S. aureus isolates from patients with endocarditis or bacteremic bone or joint infection were cna-positive compared with 65 (56%) of 117 isolates from bacteremic patients without signs of bone or joint infection (P = .99). There was a good correlation between in vitro collagen binding and presence of the cna gene. These data suggest that collagen binding is not a prerequisite for the development of endocarditis, osteomyelitis, or septic arthritis. There was no significant difference in the distribution of CP types among various patient groups, although there was a strong association between CP type 8 and the existence of the cna gene.

Detection of candidaemia in patients with and without underlying haematological disease

Diagnosing candidaemia remains difficult despite the development of new diagnostics. We report a direct comparison of three different blood-culture systems and four indirect tests. One hundred and fourteen episodes either with haematological disease and fever despite antibacterials, or with documented invasive candidiasis, were enrolled prospectively. Clinical, para-clinical information and surveillance cultures were obtained. Blood culture was performed using conventional blood-culture bottles, mycosis bottles, and the Isolator 10 lysis centrifugation system. Serum D-arabinitol/L-arabinitol (DA/LA) ratios were determined by gas chromatography mass spectrometry. Antigen, mannan-antigen (Ag) and anti-mannan antibody (Ab) were detected by CandTec, Platelia Candida Ag ELISA and Candida AB/AC/AK kits, respectively. Episodes were classified as proven (n = 24), probable (n = 14), possible (n = 52) or unlikely (n = 24) invasive candidiasis. Candidaemia involved C. albicans (17), C. albicans + C. glabrata (3), C. tropicalis (1) and yeast (1). Mycosis bottles yielded two additional positives and the conventional blood culture yielded one positive not identified by other blood-culture methods. Considering proven and unlikely episodes, respectively, sensitivity and specificity were as follows: mannan-Ag and/or anti-mannan Ab: 83.3%, 78.3%; DA/LA ratio: 41.7%, 86.4%; and CandTec Candida Ag: 66.6%, 70.8%. Lowering the cut-off values to mannan-Ag 0.10 ng/mL and anti-mannan Ab 4 AU/mL, the values were: 100%, 73.9%. Applying the DA/LA ratio to only patients with haematological neutropenia the values were: 75%, 90.5%. Fungal blood culture allowed slightly improved detection of candidaemia. The best indirect test performance was obtained from combined mannan-Ag and anti-mannan Ab detection, especially with lower cut-offs. DA/LA ratio appears to be useful in the context of haematological neutropenia.

IdeS, a Highly Specific Immunoglobulin G (IgG)-Cleaving Enzyme from Streptococcus pyogenes, Is Inhibited by Specific IgG Antibodies Generated during Infection

ABSTRACT IdeS, a recently discovered cysteine proteinase secreted by the important human pathogen Streptococcus pyogenes, interferes with phagocytic killing by specifically cleaving the heavy chain of immunoglobulin G. The fact that the enzyme targets one of the key molecules of the adapted immune response raised the question of whether an antibody response against IdeS could inhibit, i.e., neutralize, enzyme activity. Paired acute- and convalescent-phase serum samples from patients with pharyngotonsillitis (n = 10), bacteremia (n = 7), and erysipelas (n = 4) were analyzed. Antibodies with the ability to neutralize IdeS enzymatic activity were already found in two-thirds of acute-phase sera. However, patients who seroconverted to IdeS, in particular patients with pharyngotonsillitis and erysipelas, developed specific antibodies during convalescence with an increased capability to efficiently neutralize the enzymatic activity of IdeS. Also, the presence of neutralizing antibodies decreased the ability of IdeS to mediate bacterial survival in human immune blood. In patients with bacteremia, several acute-phase sera contained neutralizing antibodies, but no correlation was found to severity or outcome of invasive infections. Still, the fact that the human immune response targets the enzymatic activity of IdeS supports the view that the enzyme plays an important role during streptococcal infection.

Group B streptococcus in prosthetic hip and knee joint-associated infections.

The incidence of invasive group B streptococcus (GBS) infections in non-pregnant adults is increasing. Little is known about GBS in periprosthetic joint infections (PJIs). We aimed to analyse the clinical presentation of GBS PJI and its treatment in association with the outcome. The characteristics of 36 GBS PJIs collected from 10 centres were investigated. In 34 episodes, follow-up examination of ≥ 2 years was available, allowing treatment and outcome analysis. Most infections (75%) occurred ≥ 3 months after implantation. Most patients (91%) had at least one comorbidity; 69% presented with acute symptoms and 83% with damaged periprosthetic soft tissue. In 20 of 34 episodes debridement and retention of implant was attempted, but in five of these the prosthesis was ultimately removed. Hence, in 19 (56%) episodes, the implant was removed, including 14 immediate removals. In four episodes the removal was permanent. Penicillin derivatives and clindamycin were the most common antimicrobials administered (68%). In 94% the infection was cured, and in 82% functional mobility preserved. Debridement with implant retention was successful if the duration of symptoms was short, the prosthesis stable, and the tissue damage minor (10/10 vs 3/10 episodes, P = 0.003). Surgery that complied with a published algorithm was associated with a favourable outcome (P = 0.049).

Heparin-binding protein: A diagnostic marker of acute bacterial meningitis*

Background:The early detection of bacterial meningitis is crucial for successful outcome. Heparin-binding protein, a potent inducer of increased vascular permeability, is released from activated neutrophils in severe sepsis. Objective:In this study we investigated whether heparin-binding protein levels in cerebrospinal fluid could be used as a diagnostic marker for acute bacterial meningitis. Design:One prospective and one retrospective patient cohort from two university hospitals in Sweden were analyzed. Setting and Patients:Cerebrospinal fluid samples were collected from 174 patients with suspected central nervous system infection. Thirty-seven patients with acute community-acquired bacterial meningitis, four patients with neurosurgical bacterial meningitis, 29 patients with viral meningitis or encephalitis, seven patients with neuroborreliosis, and 97 control patients were included. Interventions:None. Measurements and Main Results:Cerebrospinal fluid samples were analyzed for the concentrations of heparin-binding protein, lactate, protein, glucose, neutrophils, and mononuclear cells. Heparin-binding protein levels were significantly higher (p < .01) in patients with acute bacterial meningitis (median 376 ng/mL, range 12–858 ng/mL) than in patients with viral central nervous system infection (median 4.7 ng/mL, range 3.0–41 ng/mL) or neuroborreliosis (median 3.6 ng/mL, range 3.2–10 ng/mL) or in control patients with a normal cerebrospinal fluid cell count (median 3.5 ng/mL, range 2.4–8.7 ng/mL). In the prospectively studied group, a heparin-binding protein concentration exceeding 20 ng/mL gave a sensitivity of 100%, a specificity of 99.2%, and positive and negative predictive values of 96.2% and 100%, respectively, in diagnosing acute bacterial meningitis. The area under the receiver-operating characteristic curve for heparin-binding protein was 0.994, which was higher than for the other investigated parameters. Conclusion:Elevated cerebrospinal fluid levels of heparin-binding protein distinguish between patients with acute bacterial meningitis and patients with other central nervous system infections.