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Flashcards in this deck (66)
  • Gram-negative bacteria are characterized by a thin layer of peptidoglycan in their cell wall, which affects their staining properties.

    microbiology gram-negative cbi4_week_5
  • The Gram stain technique categorizes bacteria into two groups: gram-positive and gram-negative.

    microbiology gram-stain cbi4_week_5
  • The primary stain used in the Gram staining process is crystal violet.

    microbiology gram-stain cbi4_week_5
  • After applying crystal violet, a mordant is used to fix the stain, which is known as Gram iodine.

    microbiology gram-stain cbi4_week_5
  • The importance of lipopolysaccharides in the gram-negative cell wall relates to their role in pathogenicity and immune response.

    microbiology lipopolysaccharides cbi4_week_5
  • Gram-negative bacteria typically stain pink after the Gram staining process due to their thin peptidoglycan layer.

    microbiology gram-negative cbi4_week_5
  • The diagnostic tests used to categorize gram-negative bacteria include Gram stain, culture, and sensitivity testing.

    microbiology diagnostics cbi4_week_5
  • The thickness of the peptidoglycan layer in bacteria determines whether they will stain purple or pink during Gram staining.

    microbiology gram-stain cbi4_week_5
  • In a clinical scenario, an 85-year-old woman with a urinary tract infection may have an infection caused by gram-negative bacteria.

    clinical microbiology cbi4_week_5
  • The alcohol solution used in the decolorization step is typically 95% ethanol.

    cbi4_week_5 microbiology gram-negative
  • The counterstain added to the sample after decolorization is safranin.

    cbi4_week_5 microbiology gram-negative
  • Gram-negative bacteria appear pink after the addition of safranin due to their thinner peptidoglycan layer.

    cbi4_week_5 microbiology gram-negative
  • The peptidoglycan layer is composed of cross-linked NAMs and NAGs.

    cbi4_week_5 microbiology peptidoglycan
  • Gram-negative bacteria typically range from 0.1 µm to 10 µm in size.

    cbi4_week_5 microbiology gram-negative
  • The bacterial cell envelope is crucial for survival, virulence, and resistance.

    cbi4_week_5 microbiology cell-envelope
  • Gram-negative bacteria have a periplasmic space before the peptidoglycan layer and an outer membrane layer.

    cbi4_week_5 microbiology gram-negative
  • The outer membrane of gram-negative bacteria contains lipopolysaccharides (LPS) and lipoproteins.

    cbi4_week_5 microbiology outer-membrane
  • Porins in the outer membrane allow hydrophilic solutes to diffuse into the periplasm.

    cbi4_week_5 microbiology porins
  • LPS, or endotoxin, is toxic to human cells and can be released after cell lysis.

    cbi4_week_5 microbiology lps
  • The three components of LPS include Lipid A, a core polysaccharide, and an O antigen polysaccharide.

    cbi4_week_5 microbiology lps
  • Lipid A anchors the LPS molecule to the phospholipid layer of the outer membrane.

    cbi4_week_5 microbiology lps
  • Lipid A can bind to immune complexes and is a potent stimulator of the immune system.

    cbi4_week_5 microbiology immune-response
  • LPS can trigger shock and aid bacteria in evading immune attacks by manipulating host cells’ sialic acid.

    cbi4_week_5 bacteria immunology
  • The O antigen is composed of 3, 4, or 5 sugars repeated up to 25 times.

    cbi4_week_5 bacteria pathogenicity
  • The strain of Escherichia coli O157:H7 is known to cause hemolytic uremic syndrome.

    cbi4_week_5 bacteria pathogenicity
  • The O antigen helps the immune system recognize gram-negative bacteria during repeat exposure.

    cbi4_week_5 immunology bacteria
  • Endotoxins like lipid A are released when bacteria cells are lysed or when LPS becomes dislodged.

    cbi4_week_5 endotoxins bacteria
  • Sepsis is characterized by a source of infection plus vital sign instabilities such as fever, hypotension, and tachypnea.

    cbi4_week_5 sepsis bacteria
  • Lipid A binds to immune complexes and stimulates the immune system through receptors like TLR4 and CD14.

    cbi4_week_5 immunology bacteria
  • The release of cytokines like TNF-α, IL-1, and IL-6 from macrophages causes fever.

    cbi4_week_5 cytokines immunology
  • Exotoxins typically consist of an A subunit for toxicity and a B subunit for adherence to host cells.

    cbi4_week_5 exotoxins bacteria
  • Bordetella pertussis, Escherichia coli, and Vibrio cholerae are examples of gram-negative bacteria that produce exotoxins.

    cbi4_week_5 exotoxins bacteria
  • The exotoxin of Pseudomonas inhibits elongation factor 2 (EF2) by ADP-ribosylation.

    cbi4_week_5 exotoxins mechanism
  • The elongation factor 2 (EF2) is inhibited by ADP-ribosylation which halts polypeptide elongation, preventing cells from producing the proteins they need to survive. This mechanism resembles that of the Diphtheria toxin.

    cbi4_week_5 bacteria pathogenicity
  • Symptoms similar to shock occur when free lipid A concentrations reach toxic levels. This condition is known as septic shock.

    cbi4_week_5 bacteria shock
  • Tissue and vascular damage lead to the activation of tissue factor, initiating the extrinsic pathway of the coagulation cascade, raising the potential for disseminated intravascular coagulation (DIC).

    cbi4_week_5 bacteria coagulation
  • Adherence factors allow bacteria to bind to host cells and form microcolonies and biofilms. Examples include fimbriae and pili.

    cbi4_week_5 bacteria adherence
  • Special enzymes that determine bacterial pathogenicity include hemolysins, cytolysins, and proteases.

    cbi4_week_5 bacteria enzymes
  • Gram-negative bacteria develop resistance due to their impermeable outer cell membrane which protects them from larger antibiotics like vancomycin.

    cbi4_week_5 bacteria resistance
  • Bacteria can mutate to resist antimicrobials through mechanisms such as cell pumps that expel medications or β-lactamases that inactivate them.

    cbi4_week_5 bacteria resistance
  • The overuse of broad-spectrum antibiotics can lead to the growth of resistant strains and the overgrowth of pathogenic bacteria due to the eradication of good bacteria.

    cbi4_week_5 bacteria antibiotics
  • To identify gram-negative bacteria in culture, laboratory tests can confirm the organism's identity based on its shape and reactions to coagulase or oxidase.

    cbi4_week_5 bacteria identification
  • The shape of bacteria can be classified as: - cocci - coccobacilli - bacilli - curved rods.

    cbi4_week_5 microbiology bacteria
  • Gram-negative bacteria do not produce coagulase; the only clinically significant bacterium that does is Staphylococcus aureus.

    cbi4_week_5 microbiology bacteria
  • The final step in the electron transport chain of bacteria may involve the enzyme cytochrome oxidase.

    cbi4_week_5 microbiology biochemistry
  • Bordetella pertussis can be cultured on: - Regan-Lowe agar - Bordet-Gengou agar.

    cbi4_week_5 microbiology culture
  • Brucella spp reacts positively to: - catalase - oxidase - urease.

    cbi4_week_5 microbiology biochemical_tests
  • Neisseria gonorrhoeae can be identified by its positive reaction to glucose and oxidase.

    cbi4_week_5 microbiology bacteria
  • Campylobacter jejuni requires Skirrow agar at 42°C and has a curved shape.

    cbi4_week_5 microbiology culture
  • Escherichia coli is known for its positive reaction to lactose and produces a green sheen on EMB agar.

    cbi4_week_5 microbiology bacteria
  • Pseudomonas aeruginosa produces a blue green pigment and has a characteristic grape odor.

    cbi4_week_5 microbiology bacteria
  • Yersinia enterocolitica can grow at 4°C and is identified by its “Safety pin” shape on CIN agar.

    cbi4_week_5 microbiology bacteria
  • Yersinia pestis is urease negative, lactose negative, and oxidase negative.

    bacteria yersinia cbi4_week_5
  • Yersinia pestis can grow at 4°C and has a characteristic safety pin shape.

    bacteria yersinia cbi4_week_5
  • The LPS component of gram-negative bacteria features lipid A, which is an endotoxin.

    bacteria lps cbi4_week_5
  • The toxic component of LPS that induces an immunological reaction in host cells is Lipid A protein.

    bacteria lps cbi4_week_5
  • Gram-negative bacteria's cell wall is characterized by a thinner peptidoglycan layer and an outer membrane.

    bacteria cell_wall cbi4_week_5
  • One method to combat antibiotic resistance in gram-negative bacteria is sensitivity testing.

    bacteria antibiotic_resistance cbi4_week_5
  • Despite their impermeable outer membrane, gram-negative bacteria can selectively absorb materials via porins.

    bacteria porins cbi4_week_5
  • Antibiotic resistance in gram-negative bacteria can result in more persistent diseases that are more refractory to treatment.

    bacteria antibiotic_resistance cbi4_week_5
  • Compared with gram-positive bacteria, gram-negative bacteria have lipopolysaccharide in their outer cell membrane.

    bacteria cell_membrane cbi4_week_5
  • The outer cell membrane is unique to gram-negative bacteria and aids in their resistance against certain antibiotics.

    cbi4_week_5 microbiology gram-negative_bacteria
  • Which of the following aids in antibiotic resistance for gram-negative bacteria? - β-Lactamases - Cell pumps - Exotoxins - Outer cell membrane - Pili

    cbi4_week_5 microbiology antibiotic_resistance
  • The importance of lipopolysaccharides in the gram-negative cell wall is significant for their structure and function.

    cbi4_week_5 microbiology cell_wall
  • Diagnostic tests like Gram stain and culture are used to categorize gram-negative bacteria.

    cbi4_week_5 microbiology diagnostics
  • Understanding the characteristics of gram-negative bacteria is crucial for health care workers.

    cbi4_week_5 microbiology healthcare