Targeting Pili in Enterococcal Pathogenesis

Pinkston, Kenneth L.; Singh, Kavindra V.; Gao, Peng; Wilganowski, Nathaniel; Robinson, Holly; Ghosh, Sukhen C.; Azhdarinia, Ali; Sevick‐Muraca, Eva M.; Murray, Barbara E.; Harvey, Barrett R.

doi:10.1128/iai.01403-13

Cited by 40 publications

(46 citation statements)

References 52 publications

(71 reference statements)

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“…In addition, success in preventing endocarditis infection by a monoclonal antibody that targets the Ebp pili of E. faecalis has been demonstrated (42). Furthermore, it was recently shown that immunization with EbpA, the counterpart of EmpA in E. faecalis, provides protection against catheter-associated bladder infections in mice (38).…”

Section: Resultsmentioning

confidence: 99%

Role of the Emp Pilus Subunits of Enterococcus faecium in Biofilm Formation, Adherence to Host Extracellular Matrix Components, and Experimental Infection

et al. 2016

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cEnterococcus faecium is an important cause of hospital-associated infections, including urinary tract infections (UTIs), bacteremia, and infective endocarditis. Pili have been shown to play a role in the pathogenesis of Gram-positive bacteria, including E. faecium. We previously demonstrated that a nonpiliated ⌬empABC::cat derivative of E. faecium TX82 was attenuated in biofilm formation and in a UTI model. Here, we studied the contributions of the individual pilus subunits EmpA, EmpB, and EmpC to pilus architecture, biofilm formation, adherence to extracellular matrix (ECM) proteins, and infection. We identified EmpA as the tip of the pili and found that deletion of empA reduced biofilm formation to the same level as deletion of the empABC operon, a phenotype that was restored by reconstituting in situ the empA gene. Deletion of empB also caused a reduction in biofilm, while EmpC was found to be dispensable. Significant reductions in adherence to fibrinogen and collagen type I were observed with deletion of empA and empB, while deletion of empC had no adherence defect. Furthermore, we showed that each deletion mutant was significantly attenuated in comparison to the isogenic parental strain, TX82, in a mixed-inoculum UTI model (P < 0.001 to 0.048), that reconstitution of empA restored virulence in the UTI model, and that deletion of empA also resulted in attenuation in an infective endocarditis model (P ‫؍‬ 0.0088). Our results indicate that EmpA and EmpB, but not EmpC, contribute to biofilm and adherence to ECM proteins; however, all the Emp pilins are important for E. faecium to cause infection in the urinary tract.

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Section: Resultsmentioning

confidence: 99%

Role of the Emp Pilus Subunits of Enterococcus faecium in Biofilm Formation, Adherence to Host Extracellular Matrix Components, and Experimental Infection

et al. 2016

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“…The numbers of bacterial CFU per gram were log transformed to negate the effect of large positive skewing of recovery values prior to performing unpaired t tests to obtain P values (21,56,(61)(62)(63)(64). Cultures yielding no growth were scored as sterile and were assigned a value of 1 CFU for statistical analysis or to obtain geometric means of CFU per gram of vegetation.…”

Section: Methodsmentioning

confidence: 99%

“…Cultures yielding no growth were scored as sterile and were assigned a value of 1 CFU for statistical analysis or to obtain geometric means of CFU per gram of vegetation. In animals that had only 1 colony recovered from the entire undiluted tissue homogenate, this value was converted to the number per gram of tissue (as was done with other recovered CFU) to determine the minimum detection limit (MDL) CFU per gram (21,56,(61)(62)(63)(64). Data and graphs were generated using Prism for Windows (version 4.00; GraphPad Software).…”

Section: Methodsmentioning

confidence: 99%

Efficacy of Ceftaroline against Methicillin-Susceptible Staphylococcus aureus Exhibiting the Cefazolin High-Inoculum Effect in a Rat Model of Endocarditis

Singh

Tran

Nannini

et al. 2017

Antimicrob Agents Chemother

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Certain Staphylococcus aureus strains exhibit an inoculum effect (InE) with cefazolin (CFZ) that has been associated with therapeutic failures in highinoculum infections. We assessed the in vitro activities of ceftaroline (CPT), CFZ, and nafcillin (NAF) against 17 type A ␤-lactamase (␤la)-producing, methicillin-susceptible S. aureus (MSSA) strains, including the previously reported TX0117, which exhibits the CFZ InE, and its ␤la-cured derivative, TX0117c. Additionally, we determined the pharmacokinetics of CPT in rats after single intramuscular doses of 20 and 40 mg/kg of body weight and evaluated the activities of CPT (40 mg/kg every 8 h [q8h]), CFZ, and NAF against TX0117 and TX0117c in a rat model of infective endocarditis. No InE was observed for CPT or NAF, whereas a marked InE was detected for CFZ (MIC, 8 to Ն128 g/ml). CPT and NAF treatment against TX0117 resulted in mean bacterial counts of 2.3 and 2.1 log 10 CFU/g in vegetations, respectively, compared to a mean of 5.9 log 10 CFU/g in the CFZ-treated group (CPT and NAF versus CFZ, P ϭ 0.001; CPT versus NAF, P ϭ 0.9830). Both CFZ and CPT were efficacious against the ␤la-cured derivative, TX0117c, compared to time zero (t 0 ) (P ϭ Ͻ0.0001 and 0.0015, respectively). Our data reiterate the in vivo consequences of the CFZ InE and show that CPT is not affected by this phenomenon. CPT might be considered for highinoculum infections caused by MSSA exhibiting the CFZ InE.KEYWORDS ␤-lactamase, Staphylococcus aureus, ceftaroline, endocarditis S taphylococcus aureus continues to be a leading cause of bacterial infections worldwide, including skin and soft tissue infections, bacteremia, pneumonia, endocarditis, septic arthritis, and osteomyelitis (1-3). The prevalence of methicillin-susceptible S. aureus (MSSA) isolates exhibiting the cefazolin (CFZ) inoculum effect (InE) in the United States has been reported to range from 19% to 27% (4, 5). Besides the United States, the overall prevalence of the cefazolin InE was reported to be 36% in South America (Colombia, Ecuador, Peru, and Venezuela), where MSSA ␤-lactamase (␤la) type A and type C were 66% and 31%, respectively (6). In South Korea, the blaZ gene was detected in 92% of 220 MSSA isolates studied, and a pronounced cefazolin InE was observed in 13%, most of which (79%) expressed type A ␤-lactamase (7). More recently, a study

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“…IgG Fab fragments against the aggregation substance AS were shown to confer partial protection against enterococcal endocarditis (45). In addition, passive immunization using a monoclonal antibody raised against the major component of E. faecalis pili, EbpC, significantly prevented the establishment of rat endocarditis (44). Our results with active vaccination using EfbA showed a significant reduction (Ͼ35%) in the number of immunized rats that developed E. faecalis infective endocarditis.…”

Section: Discussionmentioning

confidence: 57%

“…In this regard, there is increasing interest in the use of alternatives approaches to current antibiotic strategies such as the development of novel immunotherapies targeting proteins that are important for pathogenicity (41,42). MSCRAMMs, which are factors ubiquitously present in traditional and opportunistic Gram-positive pathogens, have been used as a target to develop vaccine candidates against E. faecalis (10,(43)(44)(45). Three proteins have been identified thus far as potential targets against E. faecalis endocarditis.…”

Section: Discussionmentioning

confidence: 99%

The Fibronectin-Binding Protein EfbA Contributes to Pathogenesis and Protects against Infective Endocarditis Caused by Enterococcus faecalis

et al. 2015

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EfbA is a PavA-like fibronectin adhesin of Enterococcus faecalis previously shown to be important in experimental urinary tract infection. Here, we expressed and purified the E. faecalis OG1RF EfbA and confirmed that this protein binds with high affinity to immobilized fibronectin, collagen I, and collagen V. We constructed an efbA deletion mutant and demonstrated that its virulence was significantly attenuated (P < 0.0006) versus the wild type in a mixed inoculum rat endocarditis model. Furthermore, efbA deletion resulted in diminished ability to bind fibronectin (P < 0.0001) and reduced biofilm (P < 0.001). Reintroduction of efbA into the original chromosomal location restored virulence, adherence to fibronectin, and biofilm formation to wild-type levels. Finally, vaccination of rats with purified recombinant EfbA protein protected against OG1RF endocarditis (P ‫؍‬ 0.008 versus control). Taken together, our results demonstrate that EfbA is an important factor involved in E. faecalis endocarditis and that rEfbA immunization is effective in preventing such infection, likely by interfering with bacterial adherence. E nterococci are among the first microbial colonizers of the infant gastrointestinal tract and, in healthy adults, they are part of the commensal intestinal microbiota (1). However, since the middle to late 1970s, enterococci have emerged as opportunistic pathogens and major causes of health care-associated infections, most notably urinary tract infections (UTIs) and bacteremia, second only to Staphylococcus spp. in the hospital setting (2-5). Among cases of enterococcal endocarditis, Enterococcus faecalis has been recognized as the most abundant species, accounting for more than 90% of isolates from this infection (2, 3, 6). Treatment of enterococcal endocarditis has been clinically challenging due to the emergence of strains resistant to commonly used antibiotics, i.e., aminoglycosides, although more recent use of ampicillin in combination with ceftriaxone seems to have alleviated this concern (7). The associated mortality remains high, with rates between 9 and 15% in Europe and the United States, respectively (8, 9).Adherence to and colonization of host tissue components, such as platelets and the extracellular matrix (ECM), are abilities that facilitate the early steps toward the development of infective endocarditis. To date, a variety of factors involved in the pathogenesis of experimental E. faecalis aortic valve infection have been identified; these include MSCRAMM (microbial surface components recognizing adhesive matrix molecules) proteins such as the adhesin to collagen, Ace, and the endocarditis and biofilm-associated pili, Ebp (10-12).Fibronectin is a glycoprotein consisting of two protein chains of approximately 250 kDa each, covalently linked by disulfide bonds, that is present in soluble forms in blood plasma and other body fluids. An insoluble, fibrillar form of fibronectin is present in the ECM and is known to support bacterial adherence (13). A recent study from Torelli et al. report...

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Targeting Pili in Enterococcal Pathogenesis

Cited by 40 publications

References 52 publications

Role of the Emp Pilus Subunits of Enterococcus faecium in Biofilm Formation, Adherence to Host Extracellular Matrix Components, and Experimental Infection

Role of the Emp Pilus Subunits of Enterococcus faecium in Biofilm Formation, Adherence to Host Extracellular Matrix Components, and Experimental Infection

Efficacy of Ceftaroline against Methicillin-Susceptible Staphylococcus aureus Exhibiting the Cefazolin High-Inoculum Effect in a Rat Model of Endocarditis

The Fibronectin-Binding Protein EfbA Contributes to Pathogenesis and Protects against Infective Endocarditis Caused by Enterococcus faecalis

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