Combination therapy with rifampicin or fosfomycin in patients with Staphylococcus aureus bloodstream infection at high risk for complications or relapse: results of a large prospective observational cohort.

OBJECTIVES: To investigate whether Staphylococcus aureus bloodstream infection (SAB) patients at high risk for complications or relapse benefit from combination therapy with adjunctive rifampicin or fosfomycin. METHODS: In this post hoc analysis, SAB patients with native valve infective endocarditis, osteoarticular infections or implanted foreign devices were included. The co-primary endpoints were all-cause 90 day mortality and death or SAB-related late complications within 180 days. To overcome treatment selection bias and account for its time dependence, inverse probability of treatment weights were calculated and included in marginal structural Cox proportional hazard models (MSCMs). RESULTS: A total of 578 patients were included in the analysis, of which 313 (54%) received combination therapy with either rifampicin (n = 242) or fosfomycin (n = 58). In the multivariable MSCM, combination therapy was associated with a better outcome, that is, a lower rate of death or SAB-related late complications within 180 days (HR 0.65, 95% CI 0.46-0.92). This beneficial effect was primarily seen in patients with implanted foreign devices, in which combination therapy was associated with a lower rate of death or SAB-related late complications within 180 days (HR 0.53, 95% CI 0.35-0.79) and a lower 90 day mortality (HR 0.57, 95% CI 0.36-0.91). Upon agent-specific stratification, we found no significant differences in outcomes between combination therapy containing rifampicin and fosfomycin; however, the number of patients in most subgroups was not large enough to draw firm conclusions. CONCLUSIONS: In patients with implanted foreign devices, combination therapy was associated with a better long-term outcome. Larger prospective studies are needed to validate these findings.

Staphylococcus aureus bacteremia with iliac artery endarteritis in a patient receiving ustekinumab.

BACKGROUND: Ustekinumab (Stelara®), a human monoclonal antibody targeting the p40-subunit of interleukin (IL)-12 and IL-23, is indicated for moderate to severe plaque psoriasis and psoriatic arthritis. In large multicenter, prospective trials assessing efficacy and safety of ustekinumab increased rates of severe infections have not been observed so far. CASE PRESENTATION: Here, we report the case of a 64-year old woman presenting with chills, pain and swelling of her right foot with dark maculae at the sole, and elevated inflammatory markers. She had received a third dose of ustekinumab due to psoriatic arthritis three days before admission. Blood cultures revealed growth of Staphylococcus aureus and imaging showed a thickening of the aortic wall ventral the bifurcation above the right internal iliac artery, resembling an acute bacterial endarteritis. Without the evidence of aneurysms and in absence of foreign bodies, the decision for conservative management was made. The patient received four weeks of antibiotic therapy with intravenous flucloxacillin, followed by an oral regime with levofloxacin and rifampicin for an additional four weeks. Inflammatory markers resolved promptly and the patient was discharged in good health. CONCLUSION: To our knowledge, this is the first report of a severe S. aureus infection in a patient receiving ustekinumab. Albeit ustekinumab is generally regarded as a safe drug, severe bacterial infections should always be included in the differential diagnosis of elevated inflammatory markers in patients receiving biologicals as these might present with nonspecific symptoms and fever might be absent. Any effort to detect deep-seated or metastatic infections should be made to prevent complications and to secure appropriate treatment. Although other risk factors for an invasive staphylococcal infection like psoriasis, recent corticosteroid injection, or prior hospitalisations were present, and therefore a directive causative link between the S. aureus bacteraemia and ustekinumab can not be drawn, we considered the reporting of this case worthwhile to alert clinicians as we believe that ongoing pharmacovigilance to detect increased risks for rare but severe infections beyond phase II and phase III trials in patients treated with biologicals is essential.

Haemin represses the haemolytic activity of Staphylococcus aureus in an Sae-dependent manner.

Staphylococcus aureus is a major human pathogen and a common cause of nosocomial infections. This facultative pathogen produces a large arsenal of virulence factors, including the haemolysins, which allow the bacterium to lyse erythrocytes and thereby release large amounts of the haem-containing haemoglobin. The released haem is thought to be the main iron source of this organism during the course of infection, and is considered to be crucial for bacterial proliferation in vivo. High concentrations of haem and its degradation products, on the other hand, are known to be toxic for S. aureus, making it essential for the pathogen to tightly control haem release from red blood cells. Here we show that S. aureus responds to haemin by downregulating the expression of haemolysins. Subinhibitory concentrations of haemin were found to significantly reduce transcription of the haemolysin genes hlb (encoding ß-haemolysin) and hlgA (encoding the S-class component of γ-haemolysin), while hla (encoding α-haemolysin) and RNAIII (encoding δ-haemolysin) transcription did not appear to be affected. The presence of haemin also reduced the haemolytic potential of the supernatants of S. aureus LS1 cultures. Inactivation of the sae locus in LS1 abolished the haemin effect on the transcription of haemolysin genes, indicating that the two-component regulatory system is required for this regulatory effect. Iron limitation, on the other hand, was found to induce the expression of haemolysins, and this effect was again abolished in the sae mutant, indicating that S. aureus modulates its haemolysin production in response to iron and haem availability in an Sae-dependent manner.

Effect of Clinically Uninfected Orthopedic Implants and Pacemakers/AICDs in Low-Risk Staphylococcus aureus Bloodstream Infection on Crude Mortality Rate: A Post Hoc Analysis of a Large Cohort Study.

BACKGROUND: The standard treatment duration in low-risk Staphylococcus aureus bloodstream (SAB) is 14 days. However, it is unclear whether an extended course of antimicrobial therapy is necessary in patients with clinically uninfected prosthetic joints/osteosyntheses or pacemakers/automated implanted cardioverter-defibrillators (AICDs). Thus, we compared the duration of antimicrobial therapy and outcomes in patients with and those without clinically uninfected foreign bodies. METHODS: We conducted a post hoc analysis of data from the prospective Invasive Staphylococcus aureus Infection Cohort (INSTINCT) study. Adult low-risk patients who survived ≥4 days were assessed for duration of treatment, SAB-related events (attributable death, relapse, or new deep-seated infection), and survival. RESULTS: Of the 1288 patients enrolled, 292 satisfied criteria for low-risk SAB. Forty-three patients (15%) had a clinically uninfected pacemaker/AICD or orthopedic implant. Patients with foreign bodies were significantly older (mean age, 72 vs 62 years for those without; P < .001; P = .9) and had a higher Charlson score (median, 3 vs 2; P = .06). The total duration of antimicrobial therapy (median, 18 vs 17 days, respectively; P = .7), all-cause mortality rate (16% vs 14%; P = .7), and prevalence of SAB-related events within 90 days were similar (2% vs 2%) in the 2 groups. At 1-year follow-up, SAB-related events were more frequent in patients with foreign bodies (7% vs 4% in those without; P = .4) (hazard ratio, 1.41; 95% confidence interval, .35-5.69; in a multivariable Cox model), but this difference was not statistically significant. CONCLUSIONS: Low-risk patients with clinically uninfected foreign bodies received a similar duration of antimicrobial therapy without a significant impact on mortality rate. The observed higher hazard ratio of SAB-related events within 1 year necessitates additional studies before recommendations concerning treatment duration in this patient subgroup can be adapted or modified.

eap Gene as novel target for specific identification of Staphylococcus aureus.

The cell surface-associated extracellular adherence protein (Eap) mediates adherence of Staphylococcus aureus to host extracellular matrix components and inhibits inflammation, wound healing, and angiogenesis. A well-characterized collection of S. aureus and non-S. aureus staphylococcal isolates (n = 813) was tested for the presence of the Eap-encoding gene (eap) by PCR to investigate the use of the eap gene as a specific diagnostic tool for identification of S. aureus. Whereas all 597 S. aureus isolates were eap positive, this gene was not detectable in 216 non-S. aureus staphylococcal isolates comprising 47 different species and subspecies of coagulase-negative staphylococci and non-S. aureus coagulase-positive or coagulase-variable staphylococci. Furthermore, non-S. aureus isolates did not express Eap homologs, as verified on the transcriptional and protein levels. Based on these data, the sensitivity and specificity of the newly developed PCR targeting the eap gene were both 100%. Thus, the unique occurrence of Eap in S. aureus offers a promising tool particularly suitable for molecular diagnostics of this pathogen.

Staphylococcus aureus bloodstream infection in patients with ventricular assist devices-Management and outcome in a prospective bicenter cohort.

OBJECTIVES: Ventricular assist devices (VAD) are increasingly implanted in patients with terminal heart failure. Here we describe the clinical course, management and outcome of VAD patients with S. aureus bloodstream infection (SAB). METHODS: We conducted a post hoc analysis of data from 1073 patients who had been prospectively enrolled in two consecutive SAB bicenter cohort studies. Patients with VAD in situ at the onset of SAB were identified. Follow-up of patients was at least 90 days. RESULTS: Twelve VAD patients with SAB were identified. Compared to the overall cohort, patients with VAD presented more often with fever (92% vs. 65%) and septic shock (33% vs. 23%) and showed higher C-reactive protein levels (mean 244 vs. 132 g/ml). The median time to onset of SAB after device implantation was 161 days (range 24-790 days). 30-day mortality was comparable to the whole cohort (17% vs. 19%). Infection-related surgical interventions were performed in six patients. Hematogenous dissemination to distant foci was not found in any patient. One out of nine surviving patients required continuous suppressive antibiotic therapy. CONCLUSIONS: Mortality rates for VAD patients with SAB were comparable to SAB without VAD. No hematogenous disssemination or persistent infections were recorded, which might be associated with the prompt and aggressive antibiotic and surgical management in VAD patients. SAB per se does not preclude successful transplantation.

Staphylococcus aureus bacteremia in patients with rheumatoid arthritis - Data from the prospective INSTINCT cohort.

OBJECTIVES: Patients with rheumatoid arthritis (RA) are considered to be at increased risk of severe infections. We here describe the clinical characteristics, course and outcome of RA patients with Staphylococcus aureus bacteremia (SAB). METHODS: We conducted a post hoc analysis of data from a German bi-center prospective SAB cohort study (period 2006-2014). Patients were followed-up for one year. Primary and secondary outcomes were survival time and osteoarticular infection (OAI). RESULTS: A total of 1069 patients with SAB were analyzed, with 31 patients suffering from RA. RA patients showed significantly more often OAI (15/31 patients, 48% vs. 152/1038, 15%), disseminated infection (12/31, 39% vs. 164/1038, 16%) and severe sepsis/septic shock (12/31, 39% vs. 235/1038, 23%). Day-30 mortality in RA patients was 36% (vs. 19% in non-RA patients, p = 0.034), and day 90 mortality was 58% (vs. 32%, p = 0.003). Multivariate analyses confirmed RA to be an independent risk factor for death (HR 2.3, 95% CI 1.4-3.7) and OAI (OR 4.2, 95% CI 1.8-9.8). CONCLUSIONS: Patients with RA exhibit a complicated SAB course and a high mortality, their management is challenging. Adequate antibiotic treatment, prompt invasive diagnostic and therapeutic procedures like joint lavage or surgery are of pivotal importance. Joint damage due to RA may confer a higher risk of acquiring OAI than immunosuppression.

Conservative management of Candida infection of prosthetic aortic graft by means of caspofungin and fluconazole alone.

Candida albicans infections after prosthetic graft implantation due to acute aortic dissection are rare. A combination of surgical resection and lifelong antifungal drug therapy is the gold standard for treatment of aortic graft infection, yet surgical interventions are associated with high mortality rates. Herein, we present the case of a 57-year-old man who presented with peripheral microembolism due to late-onset C. albicans infection of a prosthetic graft of the thoracic aorta, which was diagnosed by positron emission tomographic imaging. Given the high risk of reoperation, the patient was treated with intravenous caspofungin for 4 weeks, followed by oral administration of fluconazole. During a follow-up of 500 days, he remained asymptomatic, with slightly elevated inflammatory markers. This case suggests that in some instances, particularly in patients with high operative risk, Candida prosthetic graft infection can be managed conservatively with antifungal therapy alone. However, such an approach should be applied with caution and necessitates close follow-up on a long-term basis.

Antibody response to the extracellular adherence protein (Eap) of Staphylococcus aureus in healthy and infected individuals.

The extracellular adherence protein (Eap) from Staphylococcus aureus has been suggested as a vaccine candidate and for therapeutic use due to its immunomodulating and antiangiogenic properties; however, little is known about anti-Eap antibodies in humans. We determined anti-Eap antibody titers by enzyme-linked immunosorbent assay and Western blot and measured serum samples from 92 patients with proven S. aureus infections and 93 healthy controls. The functionality of antibodies was assessed by a phagocytosis assay using Eap-coated fluorescent microspheres. Antibodies were detected in all human samples, but not in mice. Patients showed significantly higher titers than controls [immunoglobulin M (IgM), P=0.007; IgG, P<0.0001]. Patients with deep or severe infections showed higher titers than those with superficial or mild disease. Eap alone was sufficient to promote phagocytosis by peripheral blood mononuclear cell and granulocytes that was moderately enhanced in the presence of human serum, but no correlation was found with the levels of anti-Eap antibodies. Anti-Eap antibodies are prevalent in all tested humans and correlate with the severity of S. aureus infection; however, they do not seem to provide protection against invasive infections. Before considering Eap for therapy or as a vaccine candidate, further studies are warranted to assess the impact of the interference between Eap and its specific antibodies.

Characterisation of Clostridium difficile isolates by slpA and tcdC gene sequencing.

The genotyping of Clostridium difficile is generally performed by the analysis of fragment- or amplification-length polymorphism by pulsed field gel electrophoresis (PFGE) or polymerase chain reaction (PCR) ribotyping. However, sequence-based methods allow typing technique standardisation and data comparison. In the present study 100 C. difficile isolates, obtained from various institutions in the state of Saarland, Germany, were prospectively analyzed by surface layer protein A single locus sequence typing (slpAST). A high proportion (52%) of isolates attributable to ribotype 027 (RT027) was found indicating that the new outbreak strain has become endemic, at least in parts of Germany. RT027 strains displayed characteristic mutations of the potential toxin repressor gene tcdC and antibiotic resistance to macrolides and fluoroquinolones. C. difficile isolates attributable to ribotypes RT001 (27%), RT014/066 (5%), RT078 (4%), to the smz genotype (3%), and to more sporadic genotypes were also identified. Overall, the prevalence of strains with resistance to macrolides or fluoroquinolones was >80%. slpAST allows the comprehensive identification of C. difficile strains by global data comparison, exemplified here by our identification of smz strains previously identified by slpAST of a Japanese outbreak. In conclusion, slpAST appears to be a powerful discriminative tool for the straightforward, standardised genotyping of C. difficile isolates.

Transcription analysis of the extracellular adherence protein from Staphylococcus aureus in authentic human infection and in vitro.

BACKGROUND: Wound infections caused by Staphylococcus aureus are associated with significant morbidity and mortality. The staphylococcal extracellular adherence protein (Eap) has been shown to delay wound healing by interfering with host defense and angiogenesis, yet the expression of Eap in the human wound is required to exert these functions. METHODS: A protocol was developed to determine eap transcription levels in vivo (human wounds) relative to those in vitro. In parallel, isolates derived from positive blood cultures were analyzed for eap transcription. RESULTS: Transcription of eap was found in vivo as well as in vitro for all isolates, with eap transcription in vivo being significantly elevated relative to that in the in vitro cultures. In vivo, isolates from deep wounds yielded higher transcription than did those from superficial wounds, whereas in vitro transcription levels for blood culture isolates exceeded those for wound isolates. CONCLUSION: This is the first comprehensive transcription analysis of S. aureus eap in authentic human wounds, and our findings support the hypothesis that Eap contributes to the development of chronic infections by interfering with wound-healing mechanisms. These findings open the door to a novel approach for exploring the complex in vivo interactions between bacteria and the host in such settings.

The roles of the nitrate reductase NarGHJI, the nitrite reductase NirBD and the response regulator GlnR in nitrate assimilation of Mycobacterium tuberculosis.

Mycobacterium tuberculosis can utilize various nutrients including nitrate as a source of nitrogen. Assimilation of nitrate requires the reduction of nitrate via nitrite to ammonium, which is then incorporated into metabolic pathways. This study was undertaken to define the molecular mechanism of nitrate assimilation in M. tuberculosis. Homologues to a narGHJI-encoded nitrate reductase and a nirBD-encoded nitrite reductase have been found on the chromosome of M. tuberculosis. Previous studies have implied a role for NarGHJI in nitrate respiration rather than nitrate assimilation. Here, we show that a narG mutant of M. tuberculosis failed to grow on nitrate. A nirB mutant of M. tuberculosis failed to grow on both nitrate and nitrite. Mutant strains of Mycobacterium smegmatis mc(2)155 that are unable to grow on nitrate were isolated. The mutants were rescued by screening a cosmid library from M. tuberculosis, and a gene with homology to the response regulator gene glnR of Streptomyces coelicolor was identified. A DeltaglnR mutant of M. tuberculosis was generated, which also failed to grow on nitrate, but regained its ability to utilize nitrate when nirBD was expressed from a plasmid, suggesting a role of GlnR in regulating nirBD expression. A specific binding site for GlnR within the nirB promoter was identified and confirmed by electrophoretic mobility shift assay using purified recombinant GlnR. Semiquantitative reverse transcription PCR, as well as microarray analysis, demonstrated upregulation of nirBD expression in response to GlnR under nitrogen-limiting conditions. In summary, we conclude that NarGHJI and NirBD of M. tuberculosis mediate the assimilatory reduction of nitrate and nitrite, respectively, and that GlnR acts as a transcriptional activator of nirBD.