Model of Staphylococcus aureus central venous catheter-associated infection in rats.

BACKGROUND AND PURPOSE: Staphylococcus aureus is an important cause of intravascular catheter-associated bacteremia. We developed a rat central venous catheter (CVC)-associated infection model to study pathogenesis and treatment. METHODS: A silastic lumen-within-lumen catheter and rodent-restraint jacket were designed. Subcutaneously tunneled catheters were inserted in the jugular vein of 20 male Sprague Dawley rats. Twelve rats (group 1) were inoculated with S. aureus via the CVC; three rats (group 2) were inoculated with S. aureus via the tail vein, five rats (group 3) served as uninfected controls; and three rats (group 4) were inoculated with S. aureus via the tail vein but did not undergo CVC insertion. Five to eight days after inoculation, animals were euthanized, CVCs were aseptically removed, and quantitative culture was done. Quantitative culture also was performed on blood, heart, liver, lungs, and kidneys. RESULTS: Infection, characterized by bacteremia and metastatic disease, was observed in all rats inoculated via the CVC with as few as 100 colony-forming units (CFU) of S. aureus. Rats of group 2 were not as likely to develop CVC-associated infection, and none of the animals of groups 3 or 4 developed infection. CONCLUSIONS: This model of CVC-associated infection should prove suitable for studying pathogenesis and treatment of the condition.     

Microarrays reveal that each of the ten dominant lineages of Staphylococcus aureus has a unique combination of surface-associated and regulatory genes

Staphylococcus aureus is the most common cause of hospital-acquired infection. In healthy hosts outside of the health care setting, S. aureus is a frequent colonizer of the human nose but rarely causes severe invasive infection such as bacteremia, endocarditis, or osteomyelitis. To identify genes associated with community-acquired invasive isolates, regions of genomic variability, and the S. aureus population structure, we compared 61 community-acquired invasive isolates of S. aureus and 100 nasal carriage isolates from healthy donors using a microarray spotted with PCR products representing every gene from the seven S. aureus sequencing projects. The core genes common to all strains were identified, and 10 dominant lineages of S. aureus were clearly discriminated. Each lineage carried a unique combination of hundreds of "core variable" (CV) genes scattered throughout the chromosome, suggesting a common ancestor but early evolutionary divergence. Many CV genes are regulators of virulence genes or known or predicted to be expressed on the bacterial surface and to interact with the host during nasal colonization and infection. Within each lineage, isolates showed substantial variation in the carriage of mobile genetic elements and their associated virulence and resistance genes, indicating frequent horizontal transfer. However, we were unable to identify any association between lineage or gene and invasive isolates. We suggest that the S. aureus gene combinations necessary for invasive disease may also be necessary for nasal colonization and that community-acquired invasive disease is strongly dependent on host factors.     

Bacteremia caused by viridans streptococci in 71 children.

A review of the hospital records of 71 patients from whose blood viridans streptococci were isolated showed that in 13 cases the patient''s illness was definitely related to the bacteremia: 4 patients had endocarditis, 3 had pneumonia, 2 had peritonitis and 1 each had meningitis, a scalp wound infection, sinusitis and otitis media. The bacteremia may have contributed to the two deaths among these 13 patients. In 45 cases the viridans streptococci may have contributed to the patient''s illness: 15 patients had an infection of the lower respiratory tract and 7 an infection of the upper respiratory tract, 8 were neonates with suspected septicemia, 3 had soft tissue infections, 3 had leukemia and sepsis, and 9 had miscellaneous infections; the bacteremia was unrelated to the two deaths in this group. In another 13 cases the viridans streptococci could not be related to the patient''s illness. The species most frequently isolated were Streptococcus mitis, S. sanguis II and S. MG-intermedius. The outcome of the bacteremia was generally good, even among the 11 patients not treated with antibiotics. When viridans streptococci are cultured from a single blood sample, further samples of blood and, if feasible, specimens from the associated focus of infection should be obtained for culture; further blood cultures are especially important in cases of suspected endocarditis.     

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

Abstract 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.     

Complete genome sequence of the clinical Streptococcus salivarius strain CCHSS3

Streptococcus salivarius is a commensal species commonly found in the human oral cavity and digestive tract, although it is also associated with human infections such as meningitis, endocarditis, and bacteremia. Here, we report the complete sequence of S. salivarius strain CCHSS3, isolated from human blood.     

Distinctive patterns in the human antibody response to Staphylococcus aureus bacteremia in carriers and non-carriers

Staphylococcus aureus is both a prominent cause of nosocomial infections with significant morbidity and mortality and a commensal with nasal carriage in around 30% of the population. The rapid spread of multi-resistant strains necessitates novel therapeutic strategies, a challenging task because the species S. aureus and the host response against it are highly variable. In a prospective study among 2023 surgical and non-surgical patients, 12 patients developed S. aureus bacteremia. They were analysed in detail using a personalized approach. For each patient, the extracellular proteins of the infecting S. aureus strain were identified and the developing antibody response was assessed on 2-D immunoblots. S. aureus carriers showed clear evidence of strain-specific pre-immunization. In all immune-competent bacteremia patients, antibody binding increased strongly, in most cases already at diagnosis. In endogenous infections, the pattern of antibody binding was similar to the pre-infection pattern. In exogenous infections, in contrast, the pre-infection pattern was radically altered with the acquisition of new specificities. These were characteristic for individual patients. Nevertheless, a common signature of 11 conserved S. aureus proteins, recognized in at least half of the bacteremic patients, was identified. All patients mounted a dynamic antibody response to a subset of these proteins.     

Effect of salicylic acid on invasion of human vascular endothelial cells by Staphylococcus aureus

Invasion of vascular endothelial cells by Staphylococcus aureus is associated with diverse complications and recurrent infection. Little is known about the effect of salicylic acid, the major metabolite of aspirin, on the interaction between S. aureus and vascular endothelial cells. We examined the adhesion of S. aureus strain 8325-4 cultured with or without salicylic acid to human umbilical vein endothelial cells (HUVECs), and the ability of the strain to invade these cells. Strain 8325-4 cells grown in salicylic acid were significantly less adherent to and invasive in HUVECs. Production of cytokine interleukin (IL)-6 was lower from the HUVECs infected with clinical isolates of S. aureus cultured in salicylic acid compared with those unexposed to salicylic acid. This study raises the possibility of using salicylic acid as an adjuvant therapeutic agent in the treatment of S. aureus bacteremia to prevent its complications or recurrence.     

Immunity induced by Staphylococcus aureus surface protein A was protective against lethal challenge of Staphylococcus aureus in BALB/c mice

Staphylococcus aureus is the most common cause of hospital-acquired bacteremia. Due to emergence of antibiotic-resistant strains, these infections present a serious public health threat. In this study, to develop a broadly protective vaccine, we tested whether immune responses induced by several proteins associated with S. aureus toxicity could protect mice from lethal challenge with human clinical S. aureus isolate USA300. We found that the surface protein A (SasA) of S. aureus could protect mice from lethal challenge of the bacteria.     

Toxic shock syndrome: clinical and laboratory findings in 30 patients.

Thirty patients with toxic shock syndrome (TSS) that developed between May 1980 and March 1983 in Vancouver were studied prospectively. In the 15 cases related to menstruation the illness followed a uniform and predictable clinical course. In the 15 other cases (3 in males) the disease was not related to menstruation, and the sources of the Staphylococcus aureus infections were diverse; 67% were hospital-acquired. Profound but transient lymphocytopenia associated with marked leukocytosis was the most striking laboratory finding and one not previously emphasized in the literature. S. aureus was isolated from sites of soft-tissue infection, the vagina or the endocervix in all except one case. Two patients had bacteremia. Phage types 29 and 29 + predominated among the isolates tested. All the genital S. aureus isolates tested produced the TSS marker protein, while the bacteria from wounds, throat, nose and blood were sometimes positive. Two patients (7%) died from refractory shock and multiple organ failure. All patients with a febrile, exanthematous, multisystem illness, particularly if it is associated with menstruation or a staphylococcal infection, should be evaluated promptly and treated empirically for TSS.     

Staphylococcus aureus subcutaneous abscess complicating acupuncture: need for implementation of proper infection control guidelines

We report a case of Staphylococcus aureus subcutaneous abscess centered over the Jizhong acupuncture point (DU 6) which lies along the Du (Back midline) meridian after acupuncture at the corresponding acupuncture point for low back pain. The patient recovered after surgical debridement and drainage and 5 weeks of cloxacillin therapy. Among the 16 anecdotal case reports of pyogenic bacterial infections complicating acupuncture described in the English literature (MEDLINE Search 1996-2002), S. aureus was documented to be the causative agent in 9 (56%). Three patients had septic arthritis, 2 had chronic osteomyelitis, 2 had abscess formation, 1 had chondritis, and 1 had infective endocarditis. Five patients had S. aureus bacteremia. All patients who recovered required prolonged antibiotic treatment of 5-6 weeks, and 6 required drainage and/or debridement. Overall, 3 patients (30%) died. S. aureus causes significant morbidity and mortality in patients who receive acupuncture treatment. More resources should be spent on implementation of proper infection control guidelines, as the money lost due to prolonged hospitalization and medication would far exceed that used for implementation.     

RNAIII-inhibiting peptide improves efficacy of clinically used antibiotics in a murine model of staphylococcal sepsis

RNAIII-inhibiting peptide (RIP, YSPWTNF-NH2) is a quorum-sensing peptide inhibitor that prevents Staphylococcus aureus toxin production and biofilm formation. A mouse sepsis model was used to test the efficacy of RIP alone or in combination with conventional antibiotics in suppressing S. aureus-induced sepsis. Mice were injected intravenously with 3.0x10(6)CFU of S. aureus ATCC 25923 or with 3.0x10(6)CFU of S. aureus strain Smith diffuse. All animals were randomized to receive intravenously isotonic sodium chloride solution as a control, or 20 mg/kg RIP alone or combined with 20 mg/kg cefazolin, 10 mg/kg imipenem, or 10 mg/kg vancomycin immediately or 6 h after bacterial challenge. Main outcome measures were bacteremia and lethality. All compounds reduced lethality when compared to controls. Although, in general combined-treated groups had significant lower bacterial counts when associated to singly-treated groups only the combination between RIP and vancomycin with respect to cefazolin gave a statistically significant decrease in the lethality rate. Lowest lethality rates (10%) and bacteremia (<10(2)CFU/ml) were obtained when RIP was administered in combination with vancomycin. Because RIP can be synergistic with current antibiotic therapies and help to reduce S. aureus exotoxins production, it can be considered a promising agent to associate with antibiotics for further clinical research into treatment of sepsis.     

Comparative immunoenzyme analysis of sera for the presence of antibodies to a preparation of Staphylococcus aureus teichoic acids and DNA

The comparative analysis of the titers of antibodies to the preparations of S. aureus teichoic acids and DNA in the sera of healthy donors and patients with infectious endocarditis and rheumatic carditis was made by means of ELISA. The sera of patients with infectious endocarditis and rheumatic carditis, in contrast to the sera of healthy donors, showed the presence of antibodies to DNA in 23.5-76.2% of cases. The correlation between the presence of antibodies to S. aureus teichoic acids and DNA in the sera of the patients was weakly pronounced.     

Spondylodiskitis and endocarditis due to <Emphasis Type="Italic">Streptococcus gordonii</Emphasis>

Background

Streptococcus gordonii is an infrequent cause of infective endocarditis (IE); associated spondylodiskitis has not yet been described in the literature.

Purpose

We describe 2 patients who presented with new-onset, severe back pain; blood cultures revealed S. gordonii bacteremia, which led to the diagnosis of spondylodiskitis and IE. We review our 2-decade experience with S. gordonii bacteremia to describe the clinical and epidemiological characteristics of these patients.

Results

In our hospital over the last 20 years (1998–2017), a total of 15 patients with S. gordonii bacteremia were diagnosed, including 11 men and 4 women, and the mean age was 65 ± 22 (range 23–95). The most common diagnosis was IE (9 patients), spondylodiskitis (the presented 2 patients, who in addition were diagnosed with endocarditis), necrotizing fasciitis (1), sternitis (1), septic arthritis (1) and pneumonia (1). The 11 patients with IE were treated with penicillin ± gentamicin, or ceftriaxone for 6 weeks, 5 required valve surgery and 10/11 (91%) attained complete cure. The 2 patients with diskitis required 2–3 months of intravenous antibiotics to achieve complete cure.

Conclusion

Spondylodiskitis was the presenting symptom of 2/11 (18%) patients with S. gordonii endocarditis. Spondylodiskitis should probably be looked for in patients diagnosed with S. gordonii endocarditis and back pain as duration of antibiotic treatment to achieve complete cure may be considerably longer.

     

Novel structurally designed vaccine for S. aureus α-hemolysin: protection against bacteremia and pneumonia

Staphylococcus aureus (S. aureus) is a human pathogen associated with skin and soft tissue infections (SSTI) and life threatening sepsis and pneumonia. Efforts to develop effective vaccines against S. aureus have been largely unsuccessful, in part due to the variety of virulence factors produced by this organism. S. aureus alpha-hemolysin (Hla) is a pore-forming toxin expressed by most S. aureus strains and reported to play a key role in the pathogenesis of SSTI and pneumonia. Here we report a novel recombinant subunit vaccine candidate for Hla, rationally designed based on the heptameric crystal structure. This vaccine candidate, denoted AT-62aa, was tested in pneumonia and bacteremia infection models using S. aureus strain Newman and the pandemic strain USA300 (LAC). Significant protection from lethal bacteremia/sepsis and pneumonia was observed upon vaccination with AT-62aa along with a Glucopyranosyl Lipid Adjuvant-Stable Emulsion (GLA-SE) that is currently in clinical trials. Passive transfer of rabbit immunoglobulin against AT-62aa (AT62-IgG) protected mice against intraperitoneal and intranasal challenge with USA300 and produced significant reduction in bacterial burden in blood, spleen, kidney, and lungs. Our Hla-based vaccine is the first to be reported to reduce bacterial dissemination and to provide protection in a sepsis model of S. aureus infection. AT62-IgG and sera from vaccinated mice effectively neutralized the toxin in vitro and AT62-IgG inhibited the formation of Hla heptamers, suggesting antibody-mediated neutralization as the primary mechanism of action. This remarkable efficacy makes this Hla-based vaccine a prime candidate for inclusion in future multivalent S. aureus vaccine. Furthermore, identification of protective epitopes within AT-62aa could lead to novel immunotherapy for S. aureus infection.     

Infective Endocarditis in the U.S., 1998–2009: A Nationwide Study

Background

Previous studies based on local case series estimated the annual incidence of endocarditis in the U.S. at about 4 per 100,000 population. Small-scale studies elsewhere have reported similar incidence rates. However, no nationally-representative population-based studies have verified these estimates.

Methods and Findings

Using the 1998–2009 Nationwide Inpatient Sample, which provides diagnoses from about 8 million U.S. hospitalizations annually, we examined endocarditis hospitalizations, bacteriology, co-morbidities, outcomes and costs. Hospital admissions for endocarditis rose from 25,511 in 1998 to 38, 976 in 2009 (12.7 per 100,000 population in 2009). The age-adjusted endocarditis admission rate increased 2.4% annually. The proportion of patients with intra-cardiac devices rose from 13.3% to 18.9%, while the share with drug use and/or HIV fell. Mortality remained stable at about 14.5%, as did cardiac valve replacement (9.6%). Other serious complications increased; 13.3% of patients in 2009 suffered a stroke or CNS infection, and 5.5% suffered myocardial infarction. Amongst cases with identified pathogens, Staphylococcus aureus was the most common, increasing from 37.6% in 1998 to 49.3% in 2009, 53.3% of which were MRSA. Streptococci were mentioned in 24.7% of cases, gram-negatives in 5.6% and Candida species in 1.0%. We detected no inflection in hospitalization rates after changes in prophylaxis recommendations in 2007. Mean age rose from 58.6 to 60.8 years; elderly patients suffered higher rates of myocardial infarction and death, but slightly lower rates of Staphylococcus aureus infections and neurologic complications. Our study relied on clinically diagnosed cases of endocarditis that may not meet strict criteria. Moreover, since some patients are discharged and readmitted during a single episode of endocarditis, our hospitalization figures probably slightly overstate the true incidence of this illness.

Conclusions

Endocarditis is more common in the U.S. than previously believed, and is steadily increasing. Preventive efforts should focus on device-associated and health-care-associated infections.     

The “Incubation Period” of Subacute Bacterial Endocarditis

In an attempt to gain information about the “incubation period” of subacute bacterial endocarditis, the literature was searched for case reports stating a specific interval between an event likely to cause bacteremia and the onset of symptoms. In 76 cases of streptococcal endocarditis for which this information was given, the median “incubation period” was one week. Symptoms began within two weeks in 64 of these cases (84%). Although there may be a bias toward reporting short incubation periods, it is concluded that the incubation period of subacute bacterial endocarditis is often shorter than is generally realized, and that procedures carried out more than two weeks before onset of symptoms are less likely to be causally related. In postcardiotomy cases, where timing of the bacteremia causing endocarditis is less easy to define, 27% of 122 cases of staphylococcal endocarditis developed within two weeks of surgery. This information is relevant to the planning and evaluation of prophylactic chemotherapy against bacterial endocarditis.     

Prevalence of Clonal Complexes and Virulence Genes among Commensal and Invasive Staphylococcus aureus Isolates in Sweden

Staphylococcus aureus encodes a remarkable number of virulence factors which may contribute to its pathogenicity and ability to cause invasive disease. The main objective of this study was to evaluate the association between S. aureus invasiveness and bacterial genotype, in terms of the presence of virulence genes and affiliation to clonal complexes. Also, the significance of different virulence genes, mainly adhesins, for the development of infective endocarditis was investigated.DNA microarray technology was used to analyze 134 S. aureus isolates, all methicillin-susceptible, derived from three groups of clinically well-characterized patients: nasal carriers (n=46), bacteremia (n=55), and bacteremia with infective endocarditis (n=33).Invasive isolates were dominant in four of the major clonal complexes: 5, 8, 15, and 25. Of the 170 virulence genes examined, those encoding accessory gene regulator group II (agr II), capsule polysaccharide serotype 5 (cap5), and adhesins such as S. aureus surface protein G (sasG) and fibronectin-binding protein B (fnbB) were found to be associated with invasive disease. The same was shown for the leukocidin genes lukD/lukE, as well as the genes encoding serine protease A and B (splA/splB), staphylococcal complement inhibitor (scn) and the staphylococcal exotoxin-like protein (setC or selX). In addition, there was a trend of higher prevalence of certain genes or gene clusters (sasG, agr II, cap5) among isolates causing infective endocarditis compared to other invasive isolates. In most cases, the presence of virulence genes was linked to clonal complex affiliation.In conclusion, certain S. aureus clonal lineages harboring specific sets of virulence genes seem to be more successful in causing invasive disease.     

In vivo detection of Staphylococcus aureus endocarditis by targeting pathogen-specific prothrombin activation

Coagulase-positive Staphylococcus aureus (S. aureus) is the major causal pathogen of acute endocarditis, a rapidly progressing, destructive infection of the heart valves. Bacterial colonization occurs at sites of endothelial damage, where, together with fibrin and platelets, the bacteria initiate the formation of abnormal growths known as vegetations. Here we report that an engineered analog of prothrombin could be used to detect S. aureus in endocarditic vegetations via noninvasive fluorescence or positron emission tomography (PET) imaging. These prothrombin derivatives bound staphylocoagulase and intercalated into growing bacterial vegetations. We also present evidence for bacterial quorum sensing in the regulation of staphylocoagulase expression by S. aureus. Staphylocoagulase expression was limited to the growing edge of mature vegetations, where it was exposed to the host and co-localized with the imaging probe. When endocarditis was induced with an S. aureus strain with genetic deletion of coagulases, survival of mice improved, highlighting the role of staphylocoagulase as a virulence factor.     

Platelet receptor polymorphisms do not influence Staphylococcus aureus-platelet interactions or infective endocarditis

Cardiac vegetations result from bacterium-platelet adherence, activation and aggregation, and are associated with increased morbidity and mortality in infective endocarditis. The GPIIb/IIIa and FcγRIIa platelet receptors play a central role in platelet adhesion, activation and aggregation induced by endocarditis pathogens such as Staphylococcus aureus, but the influence of known polymorphisms of these receptors on the pathogenesis of infective endocarditis is unknown. We determined the GPIIIa platelet antigen Pl(A1/A2) and FcγRIIa H131R genotype of healthy volunteers (n?=?160) and patients with infective endocarditis (n?=?40), and investigated the influence of these polymorphisms on clinical outcome in infective endocarditis and S. aureus-platelet interactions in vitro. Platelet receptor genotype did not correlate with development of infective endocarditis, vegetation characteristics on echocardiogram or the composite clinical end-point of embolism, heart failure, need for surgery or mortality (P?>?0.05 for all), even though patients with the GPIIIa Pl(A1/A1) genotype had increased in vivo platelet activation (P?=?0.001). Furthermore, neither GPIIIa Pl(A1/A2) nor FcγRIIa H131R genotype influenced S. aureus-induced platelet adhesion, activation or aggregation in vitro (P?>?0.05). Taken together, our data suggest that the GPIIIa and FcγRIIa platelet receptor polymorphisms do not influence S. aureus-platelet interactions in vitro or the clinical course of infective endocarditis.     

A combination of methods to evaluate biofilm production may help to determine the clinical relevance of Staphylococcus in blood cultures

Staphylococcus is the most prevalent pathogen causing bacteremia and many of its isolates possess the ability to form biofilm. In this study Staphylococcus isolates from the blood of patients with bacteremia were analyzed by two biofilm detection phenotypic methods: Congo red agar (CRA) and microtiter-plate adherence (MPA) in relation to the presence of ica genes, detected by PCR. Their oxacillin susceptibility was also evaluated. Among 127 isolates evaluated, 47 were S. aureus and 80 were coagulase negative staphylococci (CNS). Seventy-four (58.3%) isolates were mecA gene positive (27.7%S. aureus and 76.3% CNS isolates). Among the 40 S. aureus isolates which were positive for the ica genes, 25 (62.5%) were positive in MPA and 27 (67.5%) in CRA, whereas both methods combined detected 34 (85%) isolates as biofilm producers. Among 12 S. epidermidis isolates carrying ica genes, 8 were positive in MPA and 5 in CRA. The combination of CRA and MPA methods provided a better prediction of the presence of ica genes in S. aureus isolates than did either method alone.