Susan Weir

Prevalence and Predictors of Nasal and Extranasal Staphylococcal Colonization in Patients Presenting to the Emergency Department

STUDY OBJECTIVE Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common causes of skin and soft tissue infections in patients presenting to the emergency department (ED). The prevalence of asymptomatic MRSA colonization in ED patients is less well described, particularly in the absence of a skin and soft tissue infection-related complaint. The goals of this study are to assess the prevalence of nasal and extranasal staphylococcal colonization in ED patients, evaluate risk factors, and molecularly characterize the strains. METHODS We performed active surveillance for methicillin-susceptible S aureus (MSSA) and MRSA colonization in 400 subjects presenting to an urban ED. Risk factor assessment was performed and culture testing was conducted on anterior nares, oropharynx, palms, groin, perirectal area, wounds, and catheter insertion sites. Multiplex polymerase chain reaction was used to identify the USA300/400 clonal types. RESULTS The prevalence of colonization with MSSA was 39% (95% confidence interval 34.2% to 44.0%), and prevalence of colonization with MRSA was 5% (95% confidence interval 3.1% to 7.6%). Among MRSA-colonized subjects, an extranasal site tested positive in 80% of subjects, and 45% had exclusive extranasal colonization. USA300 was identified in 55% of MRSA-colonized subjects. The main risk factors for MRSA colonization included HIV infection, diabetes, and participation in contact sports. CONCLUSION The overall prevalence of MRSA colonization in this ED population was lower than that reported in other high-risk ambulatory care settings. However, extranasal colonization was present in more than half of MRSA-colonized subjects, and USA300 was the predominant clonal type.

Identification of Immunologic and Pathologic Parameters of Death versus Survival in Respiratory Tularemia

ABSTRACT Francisella tularensis can cause severe disseminated disease after respiratory infection. The identification of factors involved in mortality or recovery following induction of tularemia in the mouse will improve our understanding of the natural history of this disease and facilitate future evaluation of vaccine candidate preparations. BALB/c mice were infected intranasally with the live vaccine strain (LVS) of F. tularensis subsp. holarctica and euthanized at different stages of disease to analyze the induction of immune molecules, gross anatomical features of organs, bacterial burdens, and progression of the histopathological changes in lung and spleen. Tissue-specific interleukin-6 (IL-6), macrophage inflammatory protein 2, and monocyte chemotactic protein 1 were immune markers of mortality, while anti-LVS immunoglobulin M and IL-1β were associated with survival. Moribund mice had enlarged spleens and lungs, while surviving mice had even more prominent splenomegaly and normal-appearing lungs. Histopathology of the spleens of severely ill mice was characterized by disrupted lymphoid follicles and fragmented nuclei, while the spleens of survivors appeared healthy but with increased numbers of megakaryocytes and erythrocytes. Histopathology of the lungs of severely ill mice indicated severe pneumonia. Lungs of survivors at early time points showed increased inflammation, while at late times they appeared healthy with peribronchial lymphoid aggregates. Our results suggest that host immune factors are able to affect bacterial dissemination after respiratory tularemia, provide new insights regarding the pathological characteristics of pulmonary tularemia leading to systemic disease, and potentially identify immune markers associated with recovery from the disease.

Pili (fimbriae) of Branhamella species

PURPOSE Pili (fimbriae) have frequently been found to be involved in the attachment of bacteria to mucosal epithelial cells, an important initial step in the disease process. The purpose of this study was to determine if Branhamella catarrhalis expresses type 4 pili. MATERIALS AND METHODS Piliated B. catarrhalis phenotypic characteristics of colony morphology, agar corrosion, twitching motility, competence for deoxyribonucleic acid (DNA) transformation, autoagglutination, and pellical formation were observed. DNA was isolated from Branhamella spp. and used in genomic Southern hybridizations with a Moraxella bovis pilin gene as a probe. Electron microscopy of negatively stained bacteria was carried out to visualize pili. RESULTS B. catarrhalis has several (but not all) of the phenotypic characteristics that are related to the presence of type 4 (MePhe) pili in closely related Moraxella spp., including competence for DNA transformation, autoagglutination, pellicle formation, colony morphology, and pitting of agar. The one phenotype we have not found that is generally characteristic of type 4 piliated bacteria is twitching motility. Genomic Southern hybridization analysis using a cloned M. bovis Q pilin gene as a probe reveals DNA homologous to the Q pilin gene in B. catarrhalis, Branhamella ovis, Branhamella caviae, and Branhamella cuniculi. Examination of B. catarrhalis strain ATCC25240 by electron microscopy reveals two different kinds of pili. One kind appears similar to other type 4 pili, whereas a second class is short pili extending outward from all portions of the bacteria. CONCLUSION Phenotypic, electron-microscopic, and hybridization data are all consistent with type 4 pili being present on some B. catarrhalis strains.

Bronchus-associated lymphoid tissue (BALT) and survival in a vaccine mouse model of tularemia.

Background Francisella tularensis causes severe pulmonary disease, and nasal vaccination could be the ideal measure to effectively prevent it. Nevertheless, the efficacy of this type of vaccine is influenced by the lack of an effective mucosal adjuvant. Methodology/Principal Findings Mice were immunized via the nasal route with lipopolysaccharide isolated from F. tularensis and neisserial recombinant PorB as an adjuvant candidate. Then, mice were challenged via the same route with the F. tularensis attenuated live vaccine strain (LVS). Mouse survival and analysis of a number of immune parameters were conducted following intranasal challenge. Vaccination induced a systemic antibody response and 70% of mice were protected from challenge as showed by their improved survival and weight regain. Lungs from mice recovering from infection presented prominent lymphoid aggregates in peribronchial and perivascular areas, consistent with the location of bronchus-associated lymphoid tissue (BALT). BALT areas contained proliferating B and T cells, germinal centers, T cell infiltrates, dendritic cells (DCs). We also observed local production of antibody generating cells and homeostatic chemokines in BALT areas. Conclusions These data indicate that PorB might be an optimal adjuvant candidate for improving the protective effect of F. tularensis antigens. The presence of BALT induced after intranasal challenge in vaccinated mice might play a role in regulation of local immunity and long-term protection, but more work is needed to elucidate mechanisms that lead to its formation.

Neisseria meningitidis PorB, a Toll-Like Receptor 2 Ligand, Improves the Capacity of Francisella tularensis Lipopolysaccharide To Protect Mice against Experimental Tularemia

ABSTRACT Francisella tularensis causes severe pneumonia that can be fatal if it is left untreated. Due to its potential use as a biological weapon, research is being conducted to develop an effective vaccine and to select and study adjuvant molecules able to generate a better and long-lasting protective effect. PorB, a porin from Neisseria meningitidis, is a well-established Toll-like receptor 2 ligand and has been shown to be a promising vaccine adjuvant candidate due to its ability to enhance the T-cell costimulatory activity of antigen-presenting cells both in vitro and in vivo. BALB/c mice were immunized with lipopolysaccharide (LPS) isolated from the F. tularensis subsp. holarctica live vaccine strain (LVS), with or without PorB from N. meningitidis, and the antibody levels induced during the vaccination regimen and the level of protection against intranasal challenge with LVS were determined. Antigen administered alone induced a specific F. tularensis LPS immunoglobulin M (IgM) response that was not maintained over the weeks and that conferred protection to only 25% of the mice. In contrast, F. tularensis LPS given in combination with neisserial PorB induced consistent levels of specific IgM throughout the immunization and increased the proportion of surviving mice to 70%. Postchallenge cytokine analysis showed that interleukin-6 (IL-6), monocyte chemoattractant protein 1, and gamma interferon were markers of mortality and that IL-1β was a correlate of survival, independent of the presence of PorB as an adjuvant. These data indicate that neisserial PorB might be an optimal candidate adjuvant for improving the protective effect of F. tularensis LPS and other subunit vaccines against tularemia, but there is still a need to test its efficacy against virulent type A and type B F. tularensis strains.

Activity of Fosfomycin against Extended-Spectrum-β-Lactamase-Producing Uropathogens in Patients in the Community and Hospitalized Patients

ABSTRACT Few oral antibiotics exist for the empirical treatment of extended-spectrum β-lactamase (ESBL) urinary tract infections (UTI). In this study, we sought to determine the activity of fosfomycin against ESBL-producing uropathogens from patients at 3 Veterans Affairs (VA) facilities between 2010 and 2013. Among the ESBL uropathogens, 19.9% were fosfomycin resistant. Klebsiella species were more likely than Escherichia coli to be resistant (46% versus 4%; P < 0.001). Fosfomycin remains active against a majority of the ESBL uropathogens, although resistance among Klebsiella spp. was higher than that in previous reports.

Normal motor nerve conduction studies using surface electrode recording from the supraspinatus, infraspinatus, deltoid, and biceps.

Proximal peripheral nerve conduction studies can provide useful information to the clinician. The difficulty of measuring the length of the proximal nerve as well as a frequent inability to stimulate at 2 points along the nerve adds a challenge to the use of electrodiagnosis for this purpose. The purpose of this article is to present normal values for the suprascapular, axillary, and musculocutaneous nerves using surface electrodes while accounting for side‐to‐side variability.

Synthesis and antibacterial evaluation of new, unsymmetrical triaryl bisamidine compounds

Herein we describe the synthesis and antibacterial evaluation of a new, unsymmetrical triaryl bisamidine compound series, [Am]-[indole]-[linker]-[HetAr/Ar]-[Am], in which [Am] is an amidine or amino group, [linker] is a benzene, thiophene or pyridine ring, and [HetAr/Ar] is a benzimidazole, imidazopyridine, benzofuran, benzothiophene, pyrimidine or benzene ring. When the [HetAr/Ar] unit is a 5,6-bicyclic heterocycle, it is oriented such that the 5-membered ring portion is connected to the [linker] unit and the 6-membered ring portion is connected to the [Am] unit. Among the 34 compounds in this series, compounds with benzofuran as the [HetAr/Ar] unit showed the highest potencies. Introduction of a fluorine atom or a methyl group to the triaryl core led to the more potent analogs. Bisamidines are more active toward bacteria while the monoamidines are more active toward mammalian cells (as indicated by low CC50 values). Importantly, we identified compound P12a (MBX 1887) with a relatively narrow spectrum against bacteria and a very high CC50 value. Compound P12a has been scaled up and is currently undergoing further evaluations for therapeutic applications.

Reversion From Methicillin Susceptibility to Methicillin Resistance in Staphylococcus aureus During Treatment of Bacteremia

Approximately 3% of Staphylococcus aureus strains that, according to results of conventional phenotypic methods, are highly susceptible to methicillin-like antibiotics also have polymerase chain reaction (PCR) results positive for mecA. The genetic nature of these mecA-positive methicillin-susceptible S. aureus (MSSA) strains has not been investigated. We report the first clearly defined case of reversion from methicillin susceptibility to methicillin resistance among mecA-positive MSSA within a patient during antibiotic therapy. We describe the mechanism of reversion for this strain and for a second clinical isolate that reverts at a similar frequency. The rates of reversion are of the same order of magnitude as spontaneous resistance to drugs like rifampicin. When mecA is detected by PCR in the clinical laboratory, current guidelines recommend that these strains be reported as resistant. Because combination therapy using both a β-lactam and a second antibiotic suppressing the small revertant population may be superior to alternatives such as vancomycin, the benefits of distinguishing between mecA-positive MSSA and MRSA in clinical reports should be evaluated.

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus Isolates from Patients Newly Identified as Nasal Carriers

ABSTRACT We aimed to determine whether additional molecular and microbiological evaluations of methicillin-resistant Staphylococcus aureus (MRSA) isolated from patients newly identified as nasal carriers were useful for control strategies and whether longitudinal testing during the same or repeat hospitalization changed MRSA status. Nasal swabs from patients positive by Xpert MRSA PCR and not known to be colonized in the previous year were cultured for S. aureus. Isolates were tested for resistance to a variety of antibiotics, including high-level mupirocin resistance (HLMR) and low-level mupirocin resistance (LLMR) and the presence of genes mecA and mupA and those for Panton-Valentine leukocidin (PVL), USA300, and USA400. Repeat nasal screens during the 6-month study were tested for continued presence of MRSA. Among 130 patients, cultures revealed MRSA in 85 (65.4%), methicillin-susceptible S. aureus in 19 (14.6%), and no growth in 26 (20%). MRSA isolates were USA300 positive in 13/85 (15.3%) and LLMR in 8/85 (9.4%) patients. No isolates were HLMR or mupA positive. mecA dropout was detected in 9/130 (6.9%) patients. The rate of subsequent MRSA infections in USA300-positive versus -negative patients was not different. MRSA nasal status remained concordant in 69/70 (98.6%) patients who had follow-up testing. The findings do not support expanding MRSA surveillance to include routine detection of genes for USA300, PVL, or mupA, all of which were either of low frequency or not significantly associated with MRSA infection risk in our population of newly identified nasal carriers. Repeat nasal screening for MRSA during the same or subsequent hospitalizations over 6 months could also be deferred, reducing costs associated with screening.