Bacteria Flashcards
• Gram positive • Typically grow in clusters • Non-motile • Aerobic and facultatively anaerobic • Contain polysaccharide capsule and a slime layer/biofilm • Significant peptidoglycan layer • Contain penicillin binding proteins (PBP) • Contains structural components that facilitate adherence to host tissues • Ability to avoid phagocytosis • Production of a variety of toxins and proteolytic enzymes *Catalase activity *Coagulase activity *Pepidoglycan *Cytotoxins • Enterotoxins • Toxic shock syndrome toxin • Exfoliatin toxins A and B • Production of beta-lactamase • Methicillin resistance (MRSA) • Commonly cause nosocomial infections
Staphylococci
• Staphylococcal scalded skin syndrome (SSSS) • Also known as Ritter Disease • Severe exfoliative dermatitis • Localized, inflammed area rapidly spreads over entire body • Characterized by large bullae or cutaneous blisters • Primarily affects neonates and young children • Food poisoning / gastroenteritis • Toxic Shock Syndrome (TSS) • Cutaneous infections Impetigo • Cutaneous infections Fallicilitis • Furuncles • Carbuncles wound infections • Pneumonia / empyema • Osteomyelitis • Septic arthritis
Staphylococci. aureus
- Endocarditis
- Catheter / shunt infections
- Prosthetic joint infections
- Urinary tract infections
Staphylococci. epidermidis
- Diverse number of Gram positive organisms
- Typically grow in chains or pairs
- Aerobic and facultatively anaerobic
Streptococci
- Group A classification
- Beta hemolytic
- Spherical, grows in short to long chains
- Ability to avoid opsonization / phagocytosis
- Adhere to and invade host cells
- Production of toxins and enzymes
- Transient colonization of URT or skin surfaces
- Person-to-person contact
- Pharyngitis (Strep throat)
- Scarlet fever
- Rheumatic fever
- Acute glomerular nephritis
Streptococci pyogenes
• Virulence determined by ability to avoid
phagocytosis
• Group B classification
• Colonize lower GIT and genitourinary tract
• Common cause of septicemia and meningitis in
newborns
• Postpartum endometritis, wound infections and
UTIs in women
Streptococci agalactiae
• Associated with dental caries
Viridans strep thrive on dietary sucrose
Break down by glycolysis to form acids
Also use sucrose to form sticky glucan polymers
Mediate bacterial attachment to the tooth
• Subacute bacterial endocarditis
• Intra-abdominal infections
Viridans streptococci
• Gram positive cocci typically arranged in pairs or
short chains
• Bacteria are encapsulated (polysaccharide
capsule)
• Ability to colonize oropharynx and can easily
spread to:
• Causes mobilization of inflmmatory cells to the
focus of infection
• Pneumonia
• Sinusitis
• Meningitis
Streptococci pneumoniae
• Arranged in pairs or short chains • Gram positive cocci • Can grow both aerobically and anaerobically • Have been associated with life-threatening diseases • Virulence is associated with: Ability to adhere to tissues and form biofilms Antimicrobial resistance • Patients that are immunocompromised are particularly susceptible • Epidemiology • Enteric bacteria that can be found in the feces of humans and some animals • Common cause of nosocomial infections • Present in high concentrations in fecal mass (105 to 107 organisms per gram) • Risk factors for infection • IV or urinary catheters • Prolonged hospitalization • Immunocompromised patients • Previous use of broad-spectrum antibiotics (esp. those that do not have activity against enterococcus) • Nosocomial infections • UTI (esp. with catheterization) Asymptomatic Uncomplicated cystitis Pyelonephritis • Peritonitis (polymicrobial) • Bacteremia from local foci • Endocarditis
Enterococci
• Gram positive, non-motile rods • Form as single/paired rods or can be in chains • Spore forming • Toxin proteins • Polypeptide capsule • Human disease acquired through: Inoculation Inhalation Ingestion
Bacillus anthracis
• Opportunistic pathogens • Low capacity for virulence • Common diseases Gastroenteritis Ocular infections IV catheter sepsis • Ubiquitous organism • Most infections originate for environmental source • Food poisoning
Bacillus cereus
• Aerobic, gram positive cocco-bacilli (facultative
anaerobe)
• Exhibit end-over-end tumbling motion when
examined under the microscope
• Non spore forming
• Motile at room temperature, less so at body
temperature
• Weak beta-hemolysis
• Significant human pathogen
• Facultative intracellular pathogen
• Bacteria penetrate through intestinal lining and
are engulfed by macrophages and they live and replicate in macrophage
Listeria monocytogenes
• Aerobic, facultatively anaerobic Gm positive rods
• Nonmotile
• Catalase positive
• Pleiomorphic
• Major virulence factor is production of diphtheria
toxin
Corynebacterium diphtheriae
• Strictly aerobic, Gram-positive bacilli
• Weakly acid fast
• Catalase positive
• Slow growing
• Form branched filaments in tissues and in culture
• Presence of aerial hyphae and acid fastness is
unique
• Primary factor for virulence is the ability to avoid
phagocytic killing
can also replicate in macrophages
• Bronchopulmonary disease
• Cutaneous infection
Nocardia spp.
• Gram negative cocci (typically diplococci)
• Aerobic
• Catalase positive
• Major virulence factor is presence of
polysaccharide capsule
• Cell wall is typical of Gram negative bacteria
• Presence of pili
Neisseria
- One of the most common STDs in the U.S.
* Gonorrhea
Neisseria gonorrhoeae
- Transmitted by respiratory droplets
* Clinical disease - meningitis
Neisseria meningitidis
• Largest, most heterogenous collection of pathogenic Gram negative bacilli • Contains more than 50 genera • Ubiquitous in nature Enteric bacteria (related to the gut) Typically shaped as bacilli Facultative anaerobes Flagellated May produce endotoxins Many have developed significant resistance to antibiotics Morphology • Gram negative bacilli • Aerobic and facultatively anaerobic • The Enterobacteriaceae share a common antigen = enterobacterial common antigen • Do not form spores • Grow rapidly • Catalase positive and oxidase negative Helps differentiate Enterobacteriaceae with other GNB like Vibrio or Pseudomonas • Heat stable lipopolysaccharide is the major cell wall antigen motile (flagellated) • Many genera contain fimbirae (pili) • Endotoxin • Capsule • Antigenic phase variation (organism has genetic control of gene expression)
Enterobacteriaceae
• Organism is widely involved in many types of infections • Possesses general virulence factors common to the Enterobacteriaceae • Also has specialized virulence factors Adhesins Exotoxins Peritonitis Trauma / GSW UTI nosocomial infections Prominent organism in gastroenteritis • Neonatal meningitis • Septicemia
Escherichia coli
• Ingested through oral route
• Attaches to mucosa of the small intestine
• Bacteria invade M cells (microfold cells) or
enterocytes and replicate in th ecell
• Pathogenic process
Type III secretion system
• The organism can colonize virtually all animals
• Most infections result from ingestion of
contaminated food product
• Gastroenteritis
• Septicemia
• Typhoid fever (enteric fever)
Salmonella
S. typhi
• DNA analysis has identified these as biogroups
falling under E. coli
• cause disease by invading cells lining the
colon
• Type III secretion system injects proteins into
epithelial cells and macrophages
• The organism is engulfed by macrophages, lyse
the vacuole and replicate in the host cytoplasm
• Bacteria can be propelled through the cytoplasm
by rearranging actin filaments in the host cell
• This protects the organism from immunemediated
clearance
• survive phagocytosis by inducing
apoptosis
• Humans are the only reservoir
• Requires relatively small inoculum (100-200
bacteria)
• Gastroenteritis
Shigella
• Shigella dysentariae produces an exotoxin
(Shiga toxin)
• Common characteristic is the ability to resist
phagocytic killing
Mediated by type III secretion system
Bacteria secrete proteins into the phagocyte the
dephosphorylate proteins required for
phagocytosis
Type III system also supresses cytokine
production, diminishing inflammatory response to
infection
• All infections are zoonotic
Humans are accidental hosts
plague
Yersinia
• The plague caused
Yersinia pestis
