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Robin Patel

Publications and source records attributed to Robin Patel.

At least 37 records · Page 2Linked to original sources
PubMed2006

Intranasal exposure to bacterial superantigens induces airway inflammation in HLA class II transgenic mice.

Staphylococcus aureus is widely prevalent in the nasopharynges of healthy individuals (carriers) but can also cause serious infections. S. aureus can elaborate a variety of superantigen exotoxins in "carrier" or "pathogenic" states. Streptococcus pyogenes can also colonize the nasopharynx and elaborate superantigens. Unlike the acute effects of superantigen exotoxins absorbed through the gut or vaginal mucosa, little is known regarding the pathogenesis of superantigens entering through the intranasal route. In the current study, we evaluated the local and systemic effects of staphylococcal enterotoxin B (SEB) and streptococcal pyrogenic exotoxin A (SPEA) delivered through the intranasal route. Superantigens were administered intranasally on multiple occasions, and experimental animals were sacrificed on day 8 for experimental analyses. SEB-induced airway inflammation was more pronounced for HLA-DR3 transgenic mice than for BALB/c mice, consistent with bacterial superantigens binding more efficiently to human than murine major histocompatibility complex class II. The nature of the airway inflammation in HLA-DR3 mice was determined by the concentration of SEB applied intranasally. Low concentrations (20 ng) induced eosinophilic airway inflammation as well as eosinophil degranulation, whereas intranasal exposure to higher concentrations (2,000 ng) resulted in neutrophilic airway inflammation, permanent airway destruction, toxic shock, and mortality. SEB-induced eosinophilic inflammatory response was enhanced in signal transducer and activator of transcription (STAT)-4-deficient HLA-DQ8 transgenic mice with defective interleukin-12 signaling. Intranasal administration of SPEA induced airway inflammation and systemic immune activation in HLA-DQ8 transgenic mice. In conclusion, repeated chronic intranasal exposure to bacterial superantigens causes airway inflammation and systemic immune activation.

Administration, Intranasal↗
PubMed2006

Sonication of explanted prosthetic components in bags for diagnosis of prosthetic joint infection is associated with risk of contamination.

Explanted orthopedic implants from 54 patients with aseptic failure and 24 patients with prosthetic knee or hip infection were sonicated in polyethylene bags. The sensitivities of periprosthetic tissue and sonicate fluid cultures for the diagnosis of prosthetic joint infection were 54% and 75%, whereas the specificities were 98% and 87%, respectively. Sonication in bags improved bacterial recovery from the surface of orthopedic implants; however, it lacked specificity, due to bag leakage.

Adult↗
PubMed2006

Vancomycin-resistant enterococci: colonization, infection, detection, and treatment.

Vancomycin-resistant enterococci (VRE) are becoming a major concern in medical practice. Their increased prevalence and their ability to transfer vancomycin resistance to other bacteria (including methicillin-resistant Staphylococcus aureus) have made them a subject of close scrutiny and intense investigation. Colonization is usually acquired by susceptible hosts in an environment with a high rate of patient colonization with VRE (eg, intensive care units, oncology units). Vancomycin-resistant enterococci can survive in the environment for prolonged periods (>1 week), can contaminate almost any surface, and can be passed from one patient to another by health care workers. Whether VRE colonization leads to infection depends on the health status of the patient. Whereas immunocompetent patients colonized with VRE are at low risk for infection, weakened hosts (patients with hematologic disorders, transplant recipients, or severely ill patients) have an increased likelihood of developing infection following colonization. Quinupristin-dalfopristin and linezolid are among the anti-infective agents that have recently become available to treat infection caused by VRE. Other antimicrobials are currently under development. Molecular techniques such as polymerase chain reaction and standard culture studies are being used to detect VRE colonization, infection, and outbreaks.

Colony Count, Microbial↗
PubMed2005

Daptomycin treatment of Staphylococcus aureus experimental chronic osteomyelitis.

BACKGROUND: Infection due to methicillin-resistant Staphylococcus aureus (MRSA) is increasingly common in nosocomial and community settings. Daptomycin is a cyclic lipopeptide anti-infective with activity against MRSA, approved for treatment of complicated skin and skin structure infections. Daptomycin may be useful in systemic or local treatment of chronic osteomyelitis. METHODS: We measured mechanical strength of daptomycin- and vancomycin-loaded polymethylmethacrylate (PMMA), assayed in vivo release of daptomycin and vancomycin from daptomycin- and vancomycin-loaded PMMA, respectively, and compared the efficacy of two systemic doses of daptomycin with that of vancomycin, each with or without the respective anti-infective loaded into PMMA, using a rat model of MRSA chronic osteomyelitis. RESULTS: Neither tensile nor compressive strength of PMMA was impacted by impregnation with these antimicrobials at a concentration of 7.5% by weight. The peak concentrations of daptomycin and vancomycin in rat tibial bone surrounding a 7.5% daptomycin- and vancomycin-loaded 3 mm PMMA bead were 178 and 49 mg/L, respectively. In the treatment of experimental osteomyelitis, rats assigned to no treatment, daptomycin 50 mg/kg subcutaneously twice daily, daptomycin 60 mg/kg subcutaneously twice daily, and vancomycin 50 mg/kg intraperitoneally twice daily had 6.4, 4.1, 4.0 and 4.5 median log10 cfu/g of bone at the end of 21 days of therapy. All systemic anti-infectives studied were more active than was no treatment. Daptomycin- or vancomycin-loaded PMMA did not, however, exhibit microbiological efficacy alone or adjunctively, as assessed 21 days after implantation. CONCLUSIONS: Daptomycin is released from PMMA in vivo at a rate similar to that of vancomycin. Systemic daptomycin is as active as vancomycin in a rat model of chronic MRSA experimental osteomyelitis.

Animals↗
PubMed2005

A real-time combined polymerase chain reaction assay for the rapid detection and differentiation of Anaplasma phagocytophilum, Ehrlichia chaffeensis, and Ehrlichia ewingii.

A rapid real-time polymerase chain reaction (PCR) assay capable of the simultaneous detection and differentiation of Anaplasma phagocytophilum, Ehrlichia chaffeensis, and Ehrlichia ewingii was developed using the LightCyclertrade mark instrument (Roche Applied Sciences, Indianapolis, IN). The assay targets the operon groEL of the heat shock protein. Base pair mismatches in amplified DNA in regions of detection probe hybridization allowed organism differentiation by melting curve analysis. The analytical sensitivity was at least 10 copies per reaction. DNA extracts from 59 specimens previously confirmed positive for A. phagocytophilum (n = 37), E. chaffeensis (n = 19), or E. ewingii (n = 3) were used to evaluate the assay. All of the specimens positive for 1 of the 3 organisms by conventional PCR were likewise positive by the LightCycler method. Sensitivity and specificity were at least 100% compared with conventional PCR. This assay provides a rapid method for the detection and differentiation of the causative agents of human ehrlichiosis in the United States.

Anaplasma phagocytophilum↗
PubMed2005

In vitro activity of daptomycin against clinical isolates of Gram-positive bacteria.

We determined the activity of daptomycin, a recently FDA-approved antimicrobial agent, against clinical isolates of Gram-positive bacteria, including viridans group streptococci (16 Streptococcus mitis species group, 12 S. mutans species group, 9 S. anginosus species group, 8 S. sanguinis species group, 5 S. salivarius species group) from patients with infective endocarditis, 32 methicillin-resistant Staphylococcus aureus, 32 high-level penicillin-resistant Streptococcus pneumoniae, 38 vancomycin-resistant enterococci (including 1 linezolid-resistant isolate), and the following unusual Gram-positive bacteria: 3 Listeria monocytogenes, 4 Erysipelothrix rhusiopathiae, 9 Corynebacterium species, 10 Abiotrophia/Granulicatella species, 2 Rothia (Stomatococcus) mucilaginosus, and 4 Gemella morbillorum. Daptomycin minimum inhibitory concentration (MIC)(90) values for the viridans group streptococci, methicillin-resistant S. aureus, penicillin-resistant S. pneumoniae, and Enterococcus species were 0.5, 0.5, < or =0.125, and 4 microg/ml, respectively. The daptomycin MIC range for the unusual Gram-positive bacteria was < or =0.125-2 microg/ml. We conclude that daptomycin has in vitro activity against viridans group streptococci associated with endocarditis as well as against several types of unusual Gram-positive bacteria that can cause endocarditis.

Anti-Bacterial Agents↗
PubMed2005

The diagnosis of prosthetic joint infection: current techniques and emerging technologies.

It is important to diagnose prosthetic joint infection accurately because the medical and surgical treatment of prosthetic joint infection differs from that of other causes of prosthetic joint failure. Recognition of the presence or absence of infection at or before the time of surgery is important in directing the appropriate surgical approach. Recovery and susceptibility testing of the infecting organism are essential to the selection of appropriate anti-infective therapy.

Bacteria↗
PubMed2005

Biofilms and antimicrobial resistance.

The pathogenesis of many orthopaedic infections is related to the presence of microorganisms in biofilms. I examine the emerging understanding of the mechanisms of biofilm-associated antimicrobial resistance. Biofilm-associated resistance to antimicrobial agents begins at the attachment phase and increases as the biofilm ages. A variety of reasons for the increased antimicrobial resistance of microorganisms in biofilms have been postulated and investigated. Although bacteria in biofilms are surrounded by an extracellular matrix that might physically restrict the diffusion of antimicrobial agents, this does not seem to be a predominant mechanism of biofilm-associated antimicrobial resistance. Nutrient and oxygen depletion within the biofilm cause some bacteria to enter a nongrowing (ie, stationary) state, in which they are less susceptible to growth-dependent antimicrobial killing. A subpopulation of bacteria might differentiate into a phenotypically resistant state. Finally, some organisms in biofilms have been shown to express biofilm-specific antimicrobial resistance genes that are not required for biofilm formation. Overall, the mechanism of biofilm-associated antimicrobial resistance seems to be multifactorial and may vary from organism to organism. Techniques that address biofilm susceptibility testing to antimicrobial agents may be necessary before antimicrobial regimens for orthopaedic prosthetic device-associated infections can be appropriately defined in research and clinical settings. Finally, a variety of approaches are being defined to overcome biofilm-associated antimicrobial resistance.

Animals↗
PubMed2005

Editorial comment.

Explore the source record for details and available documents.

Congresses as Topic↗
PubMed2005

High rate of aminoglycoside resistance among staphylococci causing prosthetic joint infection.

Gentamicin and tobramycin are two aminoglycosides commonly impregnated into polymethylmethacrylate for treatment and prevention of prosthetic joint infection. Susceptibilities of staphylococci to aminoglycosides are not reported routinely in the United States. The gentamicin and tobramycin minimum inhibitory value of 93 staphylococci from patients with PJI were determined. Forty-one and 66% of the isolates were resistant to gentamicin and tobramycin, respectively. Methicillin-resistant Staphylococcus aureus isolates were more likely to be resistant to gentamicin or tobramycin than were their methicillin susceptible counterparts. The findings suggest that consideration should be given to the further study of agents other than aminoglycosides for incorporation into polymethylmethacrylate for the treatment and prevention of prosthetic joint infection.

Anti-Bacterial Agents↗
PubMed2005

Epidemiology and mechanisms of glycopeptide resistance in enterococci.

PURPOSE OF REVIEW: This review updates epidemiologic trends and our understanding of glycopeptide resistance in enterococci. RECENT FINDINGS: Colonization and infection rates with vancomycin resistant enterococci continue to increase throughout the world while factors contributing to this rise continue to be defined. While no interventions exist to eradicate colonization, infection control procedures are cost effective and decrease the prevalence of vancomycin resistant enterococcal colonization and infection. New molecular methods show great promise in strengthening our ability to detect colonization with these bacteria. Furthermore, our understanding of the origin of vancomycin resistant enterococci continues to grow. Paenibacillus species found in soil have been found to carry homologues of vanA-associated glycopeptide resistance genes found in enterococci. Also, additional evidence supports previous data that VanB-associated resistance may have been horizontally transferred from gastrointestinal tract bacteria to enterococci. Finally, glycopeptide resistance has been transferred to methicillin-resistant Staphylococcus aureus in clinical practice on several occasions. SUMMARY: The prevalence of vancomycin resistant enterococci will likely continue to increase. Implementation of infection control strategies, in conjunction with deployment of advanced technologies for detection of vancomycin resistant enterococci, may curb this rise. The emergence of vancomycin resistant S. aureus is of concern.

Anti-Bacterial Agents↗
PubMed2005

Selection of cross-resistance following exposure of Pseudomonas aeruginosa clinical isolates to ciprofloxacin or cefepime.

Exposure of ciprofloxacin- and cefepime-susceptible Pseudomonas aeruginosa isolates to increasing concentrations of ciprofloxacin selected for ciprofloxacin resistance in 26/27 and cefepime nonsusceptibility in 7/27 isolates. Exposure of the isolates to increasing concentrations of cefepime selected for cefepime nonsusceptibility in 20/27 isolates but not for ciprofloxacin resistance.

Anti-Infective Agents↗
PubMed2005

Putative VanRS-like two-component regulatory system associated with the inducible glycopeptide resistance cluster of Paenibacillus popilliae.

Paenibacillus popilliae contains vanF encoding a putative D-Ala:D-lactate (D-Lac) ligase, VanF, as part of the vanY(F)Z(F)H(F)FX(F) cluster that is similar in structure to the enterococcal vanA and vanB clusters. Using growth curves, we demonstrated that vancomycin resistance in P. popilliae is inducible. Using degenerate oligonucleotides targeted at bacterial cell wall ligases, we identified a second ligase gene with features of a D-Ala:D-Ala ligase in both P. popilliae and the related, vancomycin-susceptible, Paenibacillus lentimorbus. The 3,380-bp region upstream of vanY(F)Z(F)H(F)FX(F) in P. popilliae ATCC 14706 was sequenced and found to contain genes encoding a putative two-component regulator, VanR(F)S(F), similar to VanRS but more closely related to a family of two-component regulators linked to VanY-like carboxypeptidases in several glycopeptide-susceptible Bacillus species. This upstream region also included a transposase similar to a transposase found in Bacillus halodurans and, in some strains, a 99-bp insertion of unknown function with 95% nucleotide identity to a portion of the Tn1546 transposase gene. Analysis of glycopeptide resistance-associated clusters from soil and/or insect-dwelling organisms may provide important clues to the molecular evolution of acquired glycopeptide resistance elements in human pathogens.

Amino Acid Sequence↗
PubMed2005

In vitro and in vivo evaluations of the activities of lauric acid monoester formulations against Staphylococcus aureus.

Due to increasing mupirocin resistance, alternatives for Staphylococcus aureus nasal decolonization are needed. Lauric acid monoesters combined with lactic, mandelic, malic, or benzoic acid are being evaluated as possible alternatives. We determined the in vitro activity of 13 lauric acid monoester (LAM) formulations and mupirocin against 30 methicillin-susceptible S. aureus (MSSA) isolates and 30 methicillin-resistant S. aureus (MRSA) isolates. We then used a murine model of MRSA nasopharyngeal colonization to compare the in vivo activity of mupirocin with three LAM formulations. MSSA and MRSA MIC(90) values were 0.25 microg/ml for mupirocin and </=4 microl/ml for all LAM formulations tested. Hsd:ICR mice were challenged with 10(8) CFU/naris MRSA. Five days later, S. aureus colonization was documented by culture. Treatment with bland, mupirocin, or one of three LAM ointments was then administered unblinded thrice daily for 2 days. Three days after treatment, both anterior nares were cultured for S. aureus. Administration of 128774-49E or 128774-53A was associated with greater eradication of MRSA carriage (24/34 [71%] or 33/40 [83%]) of animals, respectively) than bland ointment (12/38 [32%]) (P < 0.005). 128774-53A administration resulted in greater MRSA carriage eradication than mupirocin (19/38 [50%]) (P < 0.005) in this model. LAM formulations warrant evaluation for S. aureus nasal decolonization in humans.

Animals↗
PubMed2005

Phenotypic and genotypic mupirocin resistance among Staphylococci causing prosthetic joint infection.

Mupirocin MICs and mupA presence were determined in 108 staphylococci causing prosthetic joint infection. Zero of 35 isolates (0%) of methicillin-susceptible Staphylococcus aureus, 4/15 (27%) methicillin-resistant S. aureus isolates, 3/16 (19%) methicillin-susceptible coagulase-negative staphylococci, and 11/42 (26%) methicillin-resistant coagulase-negative staphylococci were mupirocin resistant. mupA was detected in all five high-level mupirocin-resistant staphylococci and one mupirocin-susceptible staphylococcus.

Adolescent↗
PubMed2005

Prosthetic joint infection.

Infection is the second most common cause of prosthetic joint failure. Signs and symptoms associated with prosthetic joint infection may develop weeks or even years following arthroplasty. While some patients with prosthetic joint infection present with findings consistent with acute septic arthritis, many present with pain alone. Morbidity and cost associated with repeat surgery, prolonged medical treatment and joint immobilization render importance to the accurate and timely diagnosis, and appropriate treatment of prosthetic joint infection. No consensus exists, however, in terms of the most cost-effective diagnostic methods or the ideal medical and/or surgical interventions. This review describes diagnostic tests and available treatment for prosthetic joint infection and gives a practical approach to this challenging clinical entity.

Anti-Bacterial Agents↗