Patel, Robin

ABSTRACT Staphylococcus lugdunensis is an atypically virulent coagulase-negative staphylococcal species associated with acute and destructive infections that often resemble Staphylococcus aureus infections. Several types of infection caused by S. lugdunensis (e.g., native valve endocarditis, prosthetic joint infection, and intravascular catheter infection) are associated with biofilm formation, which may lead to an inability to eradicate the infection due to the intrinsic nature of biofilms to resist high levels of antibiotics. In this study, planktonic MICs and MBCs and biofilm bactericidal concentrations of 10 antistaphylococcal antimicrobial agents were measured for 15 S. lugdunensis isolates collected from patients with endocarditis, medical device infections, or skin and soft tissue infections. Planktonic isolates were susceptible to all agents studied, but biofilms were resistant to high concentrations of most of the drugs. However, moxifloxacin was able to kill 73% of isolates growing in biofilms at ≤0.5 μg/ml. Relative to the effect on cell density, subinhibitory concentrations of nafcillin substantially stimulated biofilm formation of most isolates, whereas tetracycline and linezolid significantly decreased biofilm formation in 93 and 80% of isolates, respectively. An unexpected outcome of MBC testing was the observation that vancomycin was not bactericidal against 93% of S. lugdunensis isolates, suggesting widespread vancomycin tolerance in this species. These data provide insights into the response of S. lugdunensis isolates when challenged with various levels of antimicrobial agents in clinical use.

ABSTRACT Staphylococci, common orthopedic pathogens, form antibiotic-resistant biofilms. Polymethylmethacrylate (PMMA) beads loaded with the quorum-sensing inhibitor RNAIII-inhibiting peptide (RIP) were implanted in rats and shown to prevent methicillin-resistant Staphylococcus aureus infection. RIP release was bimodal, typical of previously-tested antibiotics. These results suggest that RIP-PMMA warrants further evaluation for management of orthopedic infections caused by staphylococci.

ABSTRACT Conjunctival exposure to the Staphylococcus aureus superantigen staphylococcal enterotoxin B (SEB) may occur accidentally, as a result of bioterrorism, or during colonization or infection of the external eye. Using human leukocyte antigen class II transgenic mice, we show for the first time that conjunctival exposure to SEB can cause robust systemic immune activation.

ABSTRACT The activity of garenoxacin was compared to that of levofloxacin or penicillin in a rabbit model of Streptococcus mitis group (penicillin MIC, 0.125 μg/ml) and Streptococcus sanguinis group (penicillin MIC, 0.25 μg/ml) endocarditis. Garenoxacin and levofloxacin had MICs of 0.125 and 0.5 μg/ml, respectively, for both study isolates. Rabbits with catheter-induced aortic valve endocarditis were given no treatment, penicillin at 1.2 × 10 6 IU/8 h intramuscularly, garenoxacin at 20 mg/kg of body weight/12 h intravenously, or levofloxacin at 40 mg/kg/12 h intravenously. For both isolates tested, garenoxacin area under the curve (AUC)/MIC and maximum concentration of drug in serum ( C max )/MIC ratios were 368 and 91, respectively. Rabbits were sacrificed after 3 days of treatment; cardiac valve vegetations were aseptically removed and quantitatively cultured. For S. mitis group experimental endocarditis, all studied antimicrobial agents were more active than no treatment ( P < 0.001), whereas for S. sanguinis group endocarditis, no studied antimicrobial agents were more active than no treatment. We conclude that AUC/MIC and C max /MIC ratios may not predict activity of some quinolones in experimental viridans group endocarditis and that garenoxacin and levofloxacin may not be ideal choices for serious infections caused by some quinolone-susceptible viridans group streptococci.

ABSTRACT 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.

ABSTRACTStaphylococcus aureusis widely prevalent in the nasopharynges of healthy individuals (carriers) but can also cause serious infections.S. aureuscan elaborate a variety of superantigen exotoxins in “carrier” or “pathogenic” states.Streptococcus pyogenescan 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.

ABSTRACT 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.

ABSTRACT 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 μg/ml for mupirocin and ≤4 μl/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.

ABSTRACT 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 Tn 1546 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.

ABSTRACT 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.