Exam 1 Flashcards
The outer membrane of Gram- Negative Cells contains
Lipopolysaccharides (LPS)
Are gram-positive or gram-negative cells vulnerable to lysozyme and penicillin attack?
Gram-positive
What is the name of the polysacharide in Gram- + cell wall that acts as an antigenic determinant?
Teichoic Acid (important for serologic identification of many gram + species)
Lipopolysaccharide is composed of 3 covalently linked components, what are they?
- Outer carbohydrate extending into the surrounding media, O-specific side chain or O-antigen (antigenic determinants)
- Center part- water soluble core polysaccharide
- Interior- lipid A, toxic to humans and known as gram-negative endotoxin
When bacteria are lysed in efficiently working immune systems, what is released into the circulation and induces septic shock?
Lipid A
Which 2 gram + RODS produce spores?
- Bacillus
- Clostridium
Which 2 gram + RODS DO NOT produce spores?
- Cornyebacterium
- Listeria
What is the name of the special flagella on Spirochetes that run sideways under the outer membrane sheath?
Periplasmic flagella
Which bacteria ribosomal subunit does Erythromycin work on?
50s- large subunit
Tetracycline blocks protein synthesis of the ___ subunit
30s- small subunit
Properties of Facultative Anaerobes:
- prefer oxygen but can function anaerobically (similar to how we can switch to anaerobic glycolysis)
- have catalase and superoxide dismutase (SOD)
Properties of Microaerophilic bacteria:
- use fermentation and have no ETC
- can tolerate low amounts of oxygen because they have SOD
What does VIRULENCE mean?
The degree of organism pathogenicity, ability to cause disease
- depends on the presence of certain cell structures and on bacterial exotoxins and endotoxins (which are virulence factors)
Chemotaxis is:
the coordinated manner by which flagella move bacteria toward a chemical concentration gradient or away from the gradient
What is the mechanism and associated binding sites for the H and L subunits of Tetanospasmin (Tetanus Toxin) from Clostridium tetani
- H (Heavy) subunit binds to neuronal gangliosides
- L (Light) subunit: blocks release of inhibitory neurotransmitters (glycine, GABA) from Renshaw inhibitory interneurons
Which two pathogens have a window period of infection between 6 months to 2 years of age?
- Neisseria meningitidis
- H. Influenzae
What is the classic clue that there is an invasive meningococcal infection?
- the appearance of a petechial rash (due to endotoxin release from the meningococus causing vascular necrosis, inflammatory reaction and hemorrhage in the surrounding skin)
High risk groups for Neisseria meningitidis are (3):
- Infants (6months-2 years)
- Army Recruits
- College Freshmen
Which organisms is one of the most common causes of localized pneumonia in patients presenting with fever and productive cough with blood tinged sputum; Gram stain of the sputum has Gram-positive diplococci that are catalase negative, and the inflammatory response is suppurative?
Streptococcus pneumoniae
A 47-year old man with a history of sickle cell disease has had numerous hospitalizations requiring the placement of intravenous (IV) lines. The patient develops right arm swelling and discomfort at an IV site. His temperature increases to 40.1° C.
The isolated organism is catalase positive, coagulase negative, and non-hemolytic on blood agar media. Which organism is the most likely cause of this patient’s symptoms?
- Staphylococcus epidermis (Remember that staphylococcus aureus is coagulase positive and that s. epidermis produces a biofilm making it highly resistant to antibiotics)
What gram-positive cocci is beta-hemolytic, produces a golden yellow pigment when cultured, catalase +, coagulase + and PCR detects rRNA?
- Staphylococcus aureus
What are the three most common exotoxin-dependent presentations of staphyloccocus aureus?
- Gastroenteritis (food poisoning)- rapid onset, rapid recovery
- Toxic Shock Syndrome (high grade fever, N/V, watery diarrhea, erythematous rash, hypotension (may lead to frank shock), desquamation of palms and soles
- Scalded Skin Syndrome (exfoliative toxin A and B- neonates and older children with skin infections)
A throat swab from a tonsillar exudate was submitted for aerobic culture and grew gram-positive, beta hemolytic, catalase negative
cocci; so the appropriate antibiotic was prescribed. Presently, the physical examination reveals hypertension and mild
generalized edema. The physician suspects glomerular disease with hematuria and proteinuria. Which of the following is the most likely microorganism responsible for this child illness?
Streptococcus pyogenes (Group A streptococcus)
What is the clinical term for isolated pustules that rupture and become crusted; highest incidence in children; probable mode of spread is contact (transmission from carriers or patients)?
Impetigo
