Bacterial Infections and Mycoses Commons^™

Determining The Effects Of Methanol, Ethanol, Isopropanol, And Glycerol On Both Thermal Stability And Catalytic Activity Of Rv0045c, An Enzyme From M. Tuberculosis, Katelyn Baumer

Undergraduate Honors Thesis Collection

Tuberculosis (TB) is a highly infectious respiratory disease contracted through the inhalation of Mycobacterium tuberculosis. Serine hydrolases are abundant in M. tuberculosis and serve as a model for studying the inhibition of TB. Rv0045c is an example of such with little known regarding its biological function. Rv0045c was exposed to methanol, ethanol, isopropanol, or glycerol and the effects of varying concentration of these alcohols on the catalytic efficiency and thermal stability of the enzyme was determined. The thermal stability of Rv0045c was found to decrease with concentration of methanol, ethanol, or isopropanol. The opposite was true of the thermal stability …

Nitrosative Stress Sensing In Porphyromonas Gingivalis: Structure And Function Of The Heme Binding Transcriptional Regulator Hcpr, Benjamin R. Belvin

Theses and Dissertations

Porphyromonas gingivalis, a Gram negative anaerobe implicated in the progression of periodontal disease, is capable of surviving and causing infection despite high levels of reactive nitrogen species found in the oral cavity due to its efficient nitrosative stress response. HcpR is an important sensor-regulator that plays a vital step in the initiation of the nitrosative stress response in many Gram negative anaerobic bacteria. We employ a combination of X-ray crystallography, SAXS, resonance Raman spectroscopy, UV-Vis spectroscopy, and molecular biology techniques to better understand this key regulator. Knockout of the hcpR gene in W83 P. gingivalis results in the inability of …

Characterizing The Role Of Cpsa In Mycobacterial Pathogenesis, Amir Hassan

Undergraduate Research Symposium Posters

Mycobacterium tuberculosis infects one-third of the world’s population and causes an estimated 2 million deaths per year, more than any other single bacterial pathogen. The inadequacies of existing tuberculosis therapies demand the discovery of novel agents to treat M. tuberculosis infection, which requires mechanistic insight into the pathways involved in mycobacterial pathogenesis. We identified an unanticipated role of the M. tuberculosis protein CpsA in preventing phago-lysosome fusion by host macrophages, resulting in enhanced intracellular survival of bacteria within the host. Strains of M. tuberculosis lacking cpsA are severely attenuated in both macrophage and mouse models, thus establishing CpsA as a …

Human Tear Fluid Reduces Culturability Of Contact Lens-Associated Pseudomonas Aeruginosa Biofilms But Induces Expression Of The Virulence-Associated Type Iii Secretion System, Yvonne T. Wu, Connie Tam, Lucia S. Zhu, David J. Evans, Suzanne M. J. Fleiszig

Faculty Publications & Research of the TUC College of Pharmacy

Purpose

The type III secretion system (T3SS) is a significant virulence determinant for Pseudomonas aeruginosa. Using a rodent model, we found that contact lens(CL)-related corneal infections were associated with lens surface biofilms. Here, we studied the impact of human tear fluid on CL-associated biofilm growth and T3SS expression.

Methods

P. aeruginosa biofilms were formed on contact lenses for up to 7 days with or without human tear fluid, then exposed to tear fluid for 5 or 24 h. Biofilms were imaged using confocal microscopy. Bacterial culturability was quantified by viable counts, and T3SS gene expression measured …

Mucosal Fluid Glycoprotein Dmbt1 Suppresses Twitching Motility And Virulence Of The Opportunistic Pathogen Pseudomonas Aeruginosa, Jianfang Li, Matteo E. O. Metruccio, David J. Evans, Suzanne M. J. Fleiszig

Faculty Publications & Research of the TUC College of Pharmacy

It is generally thought that mucosal fluids protect underlying epithelial surfaces against opportunistic infection via their antimicrobial activity. However, our published data show that human tear fluid can protect against the major opportunistic pathogen Pseudomonas aeruginosa independently of bacteriostatic activity. Here, we explored the mechanisms for tear protection, focusing on impacts of tear fluid on bacterial virulence factor expression. Results showed that tear fluid suppressed twitching motility, a type of surface-associated movement conferred by pili. Previously, we showed that twitching is critical for P. aeruginosa traversal of corneal epithelia, exit from epithelial cells after internalization, and corneal virulence. Inhibition …

Mc-Ppea As A New And More Potent Inhibitor Of Clp-Induced Sepsis And Pulmonary Inflammation Than Fk866., Peixin Huang, Mark W Lee, Keivan Sadrerafi, Daniel P. Heruth, Li Q. Zhang, Dev Maulik, Shui Qing Ye

Manuscripts, Articles, Book Chapters and Other Papers

Our previous study indicated that overexpression of nicotinamide phosphoribosyltransferase (NAMPT) aggravated acute lung injury, while knockdown of NAMPT expression attenuated ventilator-induced lung injury. Recently, we found that meta-carborane-butyl-3-(3-pyridinyl)-2E-propenamide (MC-PPEA, MC4), in which the benzoylpiperidine moiety of FK866 has been replaced by a carborane, displayed a 100-fold increase in NAMPT inhibition over FK866. Here, we determined the effects of MC4 and FK866 on cecal ligation and puncture (CLP) surgery-induced sepsis in C57BL/6J mice. MC4 showed stronger inhibitory effects than FK866 on CLP-induced mortality, serum tumor necrosis factor α (TNFα) levels, pulmonary myeloperoxidase activity, alveolar injury, and interleukin 6 and interleukin1β messenger …

Biomarkers Of Sepsis: A Retrospective Approach, Jose M. Roberts

Williams Honors College, Honors Research Projects

Background: Biomarkers are taking the spotlight in becoming the norm for early diagnoses. Sepsis is an inflammatory disease that increases metabolic rate in children. The first biomarker is hyponatremia. Hyponatremia is a frequent electrolyte imbalance in clinical practice, often observed in children with inflammatory disease and infection. Presence of hyponatremia is associated with electrical signaling imbalances, inflammation and renal dysfunction. The clinical value of hyponatremia in pediatric patients is unknown. The C-reactive protein is a second biomarker. Its presence signifies that necrotic cells and inflammation are present.

Objectives: To evaluate the use of biomarkers in children seen in the Emergency …

Discovering A Novel Antifungal Target In Downstream Sterol Biosynthesis Using A Squalene Synthase Functional Motif, Kristin Brooke Linscott

Theses and Dissertations--Molecular and Cellular Biochemistry

The sterol biosynthetic pathway is essential for growth of all eukaryotic cells and the main target of antifungal agents. The emergence of resistance to these antifungals in an already ill patient population indicates a need to develop drugs that have a broad spectrum of activity among pathogenic fungi and have minimal patient toxicity. Squalene synthase is the first committed step in the sterol pathway and has been studied intensively for development of antifungal agents. While the overall architecture of this enzyme is identical throughout eukaryotes, it was shown that plant and animal genes cannot complement a squalene synthase knockout mutation …

Epidemiological Investigation Of Candida Species Causing Bloodstream Infection In Pediatric Small Bowel Transplant Recipients, Mallory J. Suhr, João Carlos Gomes-Neto, Nabaraj Banjara, Diana F. Florescu, David F. Mercer, Peter C. Iwen, Heather E. Hallen-Adams

Department of Food Science and Technology: Faculty Publications

Small bowel transplantation (SBT) can be a life-saving medical procedure. However, these recipients experience high risk of bloodstream infections caused by Candida. This research aims to characterize the SBT recipient gut microbiota over time following transplantation and investigate the epidemiology of candidemia in seven pediatric patients. Candida species from the recipients’ ileum and bloodstream were identified by internal transcribed spacer sequence and distinguished to strain by multilocus sequence typing and randomly amplified polymorphic DNA. Antifungal susceptibility of bloodstream isolates was determined against nine antifungals. Twenty-two ileostomy samples harbored at least one Candida species. Fungemia were caused by Candida parapsilosis …

Life-Threatening Hypercalcemia During Prodrome Of Pneumocystis Jiroveci Pneumonia In An Immunocompetent Infant, Judith Sebestyen Vansickle, Tarak Srivastava, Uri S. Alon

Manuscripts, Articles, Book Chapters and Other Papers

Severe hypercalcemia in infants is usually attributed to genetic etiologies and less commonly to acquired ones. An 8-week-old girl presented with failure to thrive, mild respiratory distress, and life-threatening hypercalcemia (23.5 mg/dL). Serum 1,25(OH)2-D) level was elevated and parathyroid hormone undetectable. Evaluation for genetic mutations and malignant etiologies of hypercalcemia was negative. Treatment with intravenous hydration, loop diuretic, and calcitonin failed to correct the hypercalcemia, which was subsequently controlled with bisphosphonate therapy. Due to progressive respiratory deterioration, a bronchopulmonary lavage was done on day 17 of her hospitalization disclosing Pneumocystis jiroveci infection. The subsequent immunological investigation showed no abnormalities. She …

Comparative Genomic Analysis Of Two Serotype 1/2b Listeria Monocytogenes Isolates From Analogous Environmental Niches Demonstrates The Influence Of Hypervariable Hotspots In Defining Pathogenesis, Aidan Casey, Kieran Jordan, Aidan Coffey, Edward M. Fox, Olivia Mcauliffe

Department of Biological Sciences Publications

The vast majority of clinical human listeriosis cases are caused by serotype 1/2a, 1/2b, 1/2c, and 4b isolates of Listeria monocytogenes. The ability of L. monocytogenes to establish a systemic listeriosis infection within a host organism relies on a combination of genes that are involved in cell recognition, internalization, evasion of host defenses, and in vitro survival and growth. Recently, whole genome sequencing and comparative genomic analysis have proven to be powerful tools for the identification of these virulence-associated genes in L. monocytogenes. In this study, two serotype 1/2b strains of L. monocytogenes with analogous isolation sources, but …

Geographical Incidence Of Antimicrobial Resistant Gonorrhea, Christofer A. Rodriguez

Master's Projects and Capstones

Evolving throughout the last century, Gonorrhea has become a superbug, becoming difficult to treat. As the second most commonly reported notifiable disease, gonorrhea rates have been increasing, despite efforts in prevention and treatment. Populations at risk are mainly MSM and FSW. In 2015, men’s gonorrhea rates in the United States were higher compared to women, at 140.9 and 107.2 per 100,000 population, respectively. Illinois has consecutively had higher rates of infection compared to the US, at 133.5 per 100,000 population compared to the US rate of 123.9 per 100,000 population. The surveillance of gonococcal isolate resistance to current antimicrobials began …

Xpert Mtb/Rif Assay Shows Faster Clearance Of Mycobacterium Tuberculosis Dna With Higher Levels Of Rifapentine Exposure., A Jayakumar, R M Savic, C K Everett, Debra Benator, D Alland, C M Heilig, M Weiner, S O Friedrich, N A Martinson, A Kerrigan, C Zamudio, S V Goldberg, W C Whitworth, J L Davis, P Nahid

Medicine Faculty Publications

The Xpert MTB/RIF assay is both sensitive and specific as a diagnostic test. Xpert also reports quantitative output in cycle threshold (CT) values, which may provide a dynamic measure of sputum bacillary burden when used longitudinally. We evaluated the relationship between Xpert CT trajectory and drug exposure during tuberculosis (TB) treatment to assess the potential utility of Xpert CT for treatment monitoring. We obtained serial sputum samples from patients with smear-positive pulmonary TB who were consecutively enrolled at 10 international clinical trial sites participating in study 29X, a CDC-sponsored Tuberculosis Trials Consortium study evaluating the tolerability, safety, and antimicrobial activity …

Pertussis-Associated Pneumonia In Infants And Children From Low- And Middle-Income Countries Participating In The Perch Study., Breanna Barger-Kamate, Maria Deloria Knoll, E Wangeci Kagucia, Christine Prosperi, Henry C Baggett, Daniel E. Park, +31 Additional Authors

Epidemiology Faculty Publications

BACKGROUND:  Few data exist describing pertussis epidemiology among infants and children in low- and middle-income countries to guide preventive strategies.

METHODS:  Children 1-59 months of age hospitalized with World Health Organization-defined severe or very severe pneumonia in 7 African and Asian countries and similarly aged community controls were enrolled in the Pneumonia Etiology Research for Child Health study. They underwent a standardized clinical evaluation and provided nasopharyngeal and oropharyngeal swabs and induced sputum (cases only) for Bordetella pertussis polymerase chain reaction. Risk factors and pertussis-associated clinical findings were identified.

RESULTS:  Bordetella pertussis was detected in 53 of 4200 (1.3%) cases …

Cost Of Care For Hospitalized Patients With Pulmonary Mycobacterial Diseases In The United States., Mary Beth Wells Allen

Electronic Theses and Dissertations

Background: Pulmonary mycobacterial diseases describe both tuberculosis (TB) and nontuberculous mycobacteria (NTM). Few data are available measuring the cost burden of mycobacterial diseases on the national level. The purpose of this study was to evaluate the cost burden and measure emerging trends in hospitalization of pulmonary TB and NTM in the US from 2001 through 2012. Methods: This study was a retrospective community based cost analysis of hospitalized patients with a principal diagnosis of pulmonary mycobacterial diseases from 2001 through 2012. Data for pulmonary TB and NTM were retrieved from the Healthcare Cost and Utilization Project (HCUP), US Department of …

Intravenous Versus Oral Antibiotics For Postdischarge Treatment Of Complicated Pneumonia., Samir S. Shah, Rajendu Srivastava, Susan Wu, Jeffrey D. Colvin, Derek J. Williams, Shawn J. Rangel, Waheeda Samady, Suchitra Rao, Christopher Miller, Cynthia Cross, Caitlin Clohessy, Matthew Hall, Russell Localio, Matthew Bryan, Gong Wu, Ron Keren, Pediatric Research In Inpatient Settings Network

Manuscripts, Articles, Book Chapters and Other Papers

BACKGROUND AND OBJECTIVES: Postdischarge treatment of complicated pneumonia includes antibiotics administered intravenously via a peripherally inserted central venous catheter (PICC) or orally. Antibiotics administered via PICC, although effective, may result in serious complications. We compared the effectiveness and treatment-related complications of postdischarge antibiotics delivered by these 2 routes.

METHODS: This multicenter retrospective cohort study included children ≥2 months andadministration, classified as PICC or oral. The primary outcome was treatment failure. Secondary outcomes included PICC complications, adverse drug reactions, other related revisits, and a composite of all 4 outcomes, termed "all related revisits."

RESULTS: Among 2123 children, 281 (13.2%) received antibiotics …

Epidemiology And Impact Of Campylobacter Infection In Children In 8 Low-Resource Settings: Results From The Mal-Ed Study, Shahida Qureshi, Aneeta Hotwani, Sadia Shakoor, (Mal-Ed) Network Investigators, Imran Ahmed, Didar Alam, Syed Asad Ali, Zulfiqar Ahmed Bhutta, Muneera Rasheed, Sajid Bashir Soofi, Ali Turab, Anita K. M. Zaidi

Department of Paediatrics and Child Health

Background: Enteropathogen infections have been associated with enteric dysfunction and impaired growth in children in low-resource settings. In a multisite birth cohort study (MAL-ED), we describe the epidemiology and impact of Campylobacter infection in the first 2 years of life.
Methods: Children were actively followed up until 24 months of age. Diarrheal and nondiarrheal stool samples were collected and tested by enzyme immunoassay for Campylobacter Stool and blood samples were assayed for markers of intestinal permeability and inflammation.
Results: A total of 1892 children had 7601 diarrheal and 26 267 nondiarrheal stool samples tested for Campylobacter We describe a high …

Tb Screening Guidelines For Transitional Care Unit, Caleb E. Newcomer

Scholars Week

The basis of this research was the formation of new TB screening and risk assessment guidelines on a Transitional Care Unit within a medical center. Current evidence-based research studies helped to guide the recommendations for the policy changes based on their results and findings. The most pertinent policy changes are the treatment offered for patients suspected with HIV, the rigorous use of the Risk Assessment Tool, and BAMT testing for TB.

Path To Resistance: Risk Factors Associated With Carbapenem-Resistant Pseudomonas Aeruginosa, Kushal Patel, Jessica J.F. Kram, Dennis J. Baumgardner

Journal of Patient-Centered Research and Reviews

Background: An estimated 51,000 health care-associated Pseudomonas aeruginosa infections occur in the United States annually. More than 13% are secondary to non-carbapenem multidrug-resistant strains, which result in 400 yearly deaths. Traditional risk factors for resistance include ICU stay, mechanical ventilation, previous hospitalization and major comorbidities. As microbes evolve, risk factors also may evolve.

Purpose: To determine if traditional and/or new risk factors for P. aeruginosa resistance are valid and predictive of infection with carbapenem-resistant P. aeruginosa.

Methods: We retrospectively studied inpatients and outpatients ≥ 18 years old who presented to an Aurora Health Care facility with a positive P. …

Novel Mutation Of Interferon-Γ Receptor 1 Gene Presenting As Early Life Mycobacterial Bronchial Disease, Maria J. Gutierrez, Neelu Kaira, Alexandra Horwitz, Gustavo Nino

Pediatrics Faculty Publications

Mendelian susceptibility to mycobacterial diseases (MSMD) are a spectrum of inherited disorders characterized by localized or disseminated infections caused by atypical mycobacteria. Interferon-γ receptor 1 (IFNGR1) deficiency was the first identified genetic disorder recognized as MSMD. Mutations in the genes encoding IFNGR1 can be recessive or dominant and cause complete or partial receptor deficiency. We present the case of a 2½-year-old boy with a history of recurrent wheezing, diagnosed with endobronchial mycobacterial infection. Immunological workup revealed a homozygous nonsense mutation in the IFNGR1 gene, a novel mutation predicted in silico to cause complete IFNGR1 deficiency. This case demonstrates that ( …

A 5-Year-Old With Fever, Headache, Neck Stiffness, And Leg Pain., Joy L. Solano, Grace Winningham, Duha Al Zubeidi, Angela Myers

Manuscripts, Articles, Book Chapters and Other Papers

A 5-year-old boy presented with fever, headache, fatigue, neck stiffness, and 2 episodes of nocturnal urinary incontinence, prompting a visit to the emergency department. He had experienced intermittent frontal headaches and leg and buttock pain for several months, which had worsened over the previous 2 weeks. His history was notable for a spinal hemangioma with vascular tract, but he was otherwise healthy. On examination, he was febrile and tachycardic. He held his neck slightly rotated to the right with limited range of motion in all directions due to pain. No focal neurologic deficits were noted, and sensation and deep tendon …

When It Isn’T Always Lyme: Expanding The Differential Diagnosis For Acute-Onset Polyarthralgia In The West Virginia Eastern Panhandle, Natalie A. Moffett, Rosemarie Lorenzetti

Marshall Journal of Medicine

This case presentation discusses a 36 year-old female animal care worker presenting with an acute-onset polyarthropathy during the summer months in a Lyme endemic region. Though she appeared to be a good candidate for the diagnosis of Lyme borreliosis, her screening serology reported negative results and alternative diagnoses were considered. Her subsequent diagnosis with parvovirus B19 acts to remind the general practitioner to have confidence in the accuracy of a negative Lyme screen and, upon negative result, to expand the differential to include less common infections including parvovirus B19. It also highlights the need to remember parvovirus B19 in a …

There Is A Trend Favoring Vancomycin Vs. Metronidazole In Treating Severe C. Difficile Infection, Dean D. Fouchia

Clinical Research in Practice: The Journal of Team Hippocrates

A critical appraisal and clinical application of Johnson S, Louie TJ, Gerding DN, et al. Vancomycin, metronidazole, or tolevamer for Clostridium difficile infection: results from two multinational, randomized, controlled trials. Clin Infect Dis. 2014;59(3):345-354. doi: 10.1093/cid/ciu313

Changing Diagnostic Methods And Increased Detection Of Verotoxigenic Escherichia Coli, Ireland, Thomas Rice, Noreen Quinn, Roy D. Sleator, Brigid Lucey

Department of Biological Sciences Publications

The recent paradigm shift in infectious disease diagnosis from culture-based to molecular-based approaches is exemplified in the findings of a national study assessing the detection of verotoxigenic Escherichia coli infections in Ireland. The methodologic changes have been accompanied by a dramatic increase in detections of non-O157 verotoxigenic E. coli serotypes.

Investigation Of Cnt-Induced Escherichia Coli Lysis And Protein Release, Abdollah Mosleh

Graduate Theses and Dissertations

This research investigated the use of carbon nanotubes (CNTs) as a treatment to increase the permeability of a bacterial cell wall. Recombinant Escherichia coli BL21 (DE3) containing a plasmid that expressed Green Fluorescent Protein (GFP) and -lactamase were exposed to CNTs under various levels of agitation for different times. Fluorescence assay for GFP, optical absorbance for -lactamase activity, and Transmission Electron Microscopy (TEM) were used to determine the amount of released protein, and visually examine the permeability enhancement of the cells, respectively. It was found that more -lactamase was present in the culture fluid after treatment with CNTs in a …

Comparisons Of Selected Household And Commercial Disinfectants Against Poultry Salmonella Isolates And A Survey Of Internal Parasites In Backyard Poultry In Arkansas, Kayleigh Moyle

Graduate Theses and Dissertations

Backyard and exhibition poultry have been gaining in popularity and as such there has been a large increase in the number of small flocks. As the interaction with poultry has increased, so has the opportunity for diseases and parasites, for both birds and people. One of the major zoonotic illnesses is caused by the bacteria Salmonella, which can be found in commercial and small flocks. Salmonella is the number 2 contributor of foodborne illnesses so its prevalence in commercial flocks is of high concern. Despite improved cleaning, disinfection, and biosecurity practices, there is still potential for disease outbreaks and infections …

Study Design Of A Cluster-Randomized Controlled Trial To Evaluate A Large-Scale Distribution Of Cook Stoves And Water Filters In Western Province, Rwanda, Corey L. Nagel, Miles Kirby, Laura D. Zambrano, Ghislaine Rosa, Christina K. Barstow, Evan A. Thomas, Thomas Clasen

Mechanical and Materials Engineering Faculty Publications and Presentations

Background: In Rwanda, pneumonia and diarrhea are the first and second leading causes of death, respectively, among children under five. Household air pollution (HAP) resultant from cooking indoors with biomass fuels on traditional stoves is a significant risk factor for pneumonia, while consumption of contaminated drinking water is a primary cause of diarrheal disease. To date, there have been no largescale effectiveness trials of programmatic efforts to provide either improved cookstoves or household water filters at scale in a low-income country. In this paper we describe the design of a clusterrandomized trial to evaluate the impact of a national-level program …

Endothelial Hspa12b Is A Novel Protein For The Preservation Of Cardiovascular Function In Polymicrobial Sepsis Via Exosome Mir-126, Xia Zhang

Electronic Theses and Dissertations

Sepsis is the most frequent cause of mortality in most intensive care units. Cardiovascular dysfunction is a major complication associated with sepsis, with high mortality rates up to 70%. Currently, there is no effective treatment approach for sepsis.

The integrity of the endothelium is fundamental for the homeostasis of the cardiovascular system. Sepsis induces endothelial cell injury which is the key factor for multiple organ failure. The increased expression of adhesion molecules and chemokines in endothelial cell promotes leukocytes infiltration into the tissue. The loss of tight junction proteins and increased permeability of the endothelial cells will provoke tissue hypoxia …

Linezolid Induced Delirium In The Absence Of Serotonin Syndrome: A Psychiatric Consultation/Liaison Case Report, Hani Nazha, Md, Nathan T. Harrington, Md

Marshall Journal of Medicine

Delirium is one of the most common mental illnesses that can affect elderly patients and patients with advanced medical problems. Because these patients are frequently on multiple medications and/or are more sensitive to medications secondary to their age, interactions with current medications, or existing medical problems; medication toxicity is frequently the etiology behind their delirium. This is a case report of a patient admitted for cellulitis that developed delirium from Linezolid however did not develop any other signs or symptoms of Serotonin Syndrome; a known side effect of Linezolid. This distinctive case highlights the importance of a careful analysis of …

Gram-Negative Bacteria And Sepsis, Christine D. Ridge

Nursing Student Class Projects (Formerly MSN)

Today’s medical world encompasses an environment in which gram-negative bacteria that once were defeated with common antibiotics, have now become resistant. Gram-negative bacteria like Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterobacter, and Acinetobacter are pathogens that are an emerging threat causing sepsis due to multidrug-resistance (Pop-Vicas & Opal, 2014, p.189). The multidrug-resistance mechanisms of gram-negative bacteria coupled with a patient population commonly seen in hospital settings, that consist of immunocompromised adults due to advancing age, comorbidities (e.g. AIDS, history of transplants, diabetes, and chemotherapy), and immunotherapies, create an environment for advanced infection or sepsis to take place.

Complications of multidrug-resistant gram-negative bacteria …