BacT lecture 5 Flashcards
What is a Opportunistic pathogens?
Pathogens are organisms that do not cause disease in a healthy host, with a healthy immune system.
What pathogens are equipped with virulence genes for adherence, invasion, evasion form the immune system and toxins?
True pathogens
Nosocomial Infections
Hospital acquired infections
Which type if infection almost always causes nosocomial infections?
Opportunistic pathogens
Clinical classifications in diagnostic microbiology of bacterial pathogens?
Gram-neg vs Gram-pos
Cocci vs Rods
Fermenter vs Nonfermenter
Based on their oxygen requirements of bacterial pathogens?
Aerobic
Facultative anaerobic
Anaerobic
Microaerophillic
Dichotomous keys are like?
Phylogenetic trees used to ID bacteria in diagnostic labs
The majority of bacteria are?
Extracellular pathogens
Extra cellular pathogens
Multiply, feed, and replicate in the fluid outside the cell
Obligate Intracellular pathogens are
Pathogens that only survive and replicate inside the cell. Lack the metabolic pathways to live outside the cell
T:F Obligate intracellular pathogens can be cultivated in medium?
False
Obligate intracellular pathogens can only be grown in cells or animals
Facultative intracellular pathogens are
Pathogens that can survive inside the cell to protect from the immune system, but also can survive outside the cell.
Example of Obligate intracellular pathogen?
Rickettsia, Chlamadia
Example of Facultative intracellular pathogen?
Mycobacterium
In terms of veterinary practice what are the two important Gram positive cocci?
Staphylococcus
Streptococcus
Staphylococcus is a?
Facultatively anaerobic, that is an opportunistic pathogen. Often skin infections, mucus membrane infections, Pyogentic bacteria (puss producing), post surgical infection.
The four veterinary significant Staphylococcus
S. aureus
S. intermedius (Dogs)
S. hyicus (Greasy pig disease)
S. Schleiferi subsp. coagulans
What is significant about Staphylococcus aureus?
Opportunistic nosocomial and community infection. Increased notoriety due to methicillin-resistant Staphylococcus aureus (MRSA) infection.
Staphylococcus cause?
Hot spots in dogs -traumatic dermatitis
Greasy pig disease
Peracute gangrenous mastitis in cows, goat, sow, ewe
Pathogenicity in Staphylococcus?
Botryomycosis- also known as bacterial pseudomycosis are a rare chronic granulomatous bacterial infection that affects the skin, and sometimes viscera; infrequent chronic pyogranulomatous inflammation, leasions, udder
Coagulase is?
An enzyme that virulent strains produce that coagulate blood plasma
Staphylococcus exotoxins and virulence factors that are produced?
Enterotoxin A-E Exfoliatin Epidermolytic toxin Haemolysins Leukocidins Protein A
What is Enterotoxin A-E
Food poisoning superantigens. Heat resistant. Most common cause of food poisoning.
Exfoliatin
Skin- toxin specific for the epidermidis, produced by S. aureus and S. hyicus.
Epidermolytic toxins effect the?
skin
Haemolysins
Destroy blood cells- erythrocytes from various species differ in susceptibility to the 4 different toxins.
Leukocidins
Kills immune system cells. Leucocites- granulocytes and macrophages
Protein A
Present as a surface component (cell wall) on most strains of virulent S. aureus. Is antiphagocytic and has the ability to bind to Fc fragment of IgG
What type of antibiotic is S. aureus resistant to?
Beta-lactam antibiotics (penicillins and cephalosporins)
How are S. aureus resistant to Beta-Lactam antibiotics?
They produce a phage-coded penicillinase. Some strains have a modified penicillin binding protein PBP2A conded by a Mec A gene
Healthy person carrying MRSA and not becoming ill, but passing it on to others that become ill is known as
MRSA-Community acquired
Streptococcus is
A large group that occurs widely in nature and also as normal flora of man and animal. Facultatively anaerobic.
List some Streptococcus
S. pyogenes - mostly human S. agalactiae - mastitis S. dysgalactiae - mastitis S. equi subsp. equi - strangels in horses S. equi subsp. zooepidemicus
The two Streptococcus that are pyogenic bacteria are?
S. pneumonia
S. equi subsp. equi
Streptococcus pyogenic bacteria have?
Capsule - non antigenic but interferes with phagocytosis
Streptococcus have homolysins. What are homolysins?
Production of a wide variety of toxins capable of destroying erythrocytes, resulting in a clear area surrounding colonies.
What is Lancefield groups?
Serological classification of Streptococcus based CHO cell wall antigens.
The most important groupable streptococci are?
A,B and D
Groupable Streptococcus, infectious disease group A include?
S. pyogenes - scarlet fever in humans
S. pneumoniae
S. mutans
Gram-positive rods can be classified into what two groups?
Endospore- forming and non endospore- forming
Give examples of Gram-pos rods that are endospore forming.
Bacillus
Clostridium
What was the first bacterium shown to cause disease?
Bacillus anthracis
Bacillus anthracis is commonly known as?
Anthrax - serious, often fatal zoonotic disease of wild and domestic mammals
Bacillus is a?
Obligate aerobe that is a edospore producing gram-pos rod
Bacillus anthracis’s virulence factors include?
Endospores
Capsule
Exotocins
Despite Bacillus anthracis’s exotocins being 3 heat labile protein components it is still a?
A-B toxin
Horizontal gene transfer of the virulent strains in plasmids of Bacillus anthracis was done by?
Conjunction
Virulent strains of Bacillus anthracis harbor two plasmids, what are they
PXO1 -codes for the toxin (EF, PA, LF)
PXO2 -condes for the Capsule- (Poly D glutamic acid capsule)
Bacillus anthracis causes?
Spleenomegaly
T:F You should never open a animal that is thought to have Bacillus anthracis infection?
True
The spores can spread to you or other animals.
Which parts of the protein belong to parts of the A-B toxin?
Lethal factor and edema factor enzymes are Part A
Protective antigen binding is Part B
What are the ways humans can become infected with Bacillus anthracis?
Cutaneous - direct contact with disease animals
Inhalation - Woolsorter’s disease
Ingestion - meat from diseased animals
Clostridium is a?
Obligate anaerobe
What are the four groups that Clostridium can be divided into according to what disease they produce.
Histotoxic Clostridia
Hepatotoxic Clostridia
Enterotoxigenic Clostridia
Neurotoxic Clostridia
Clostridium that cause tissue infections (mostly muscle) following wounds, other trauma eg Malignant edema
Histotoxic Clostridia
Hepatotoxic Clostridia
Clostridium that produces toxins in the liver (cause bacillary hemogleobinuria and black disease)
Clostridium that produces mainly enterotoxemia and food poisoning.
Enterotoxigenic Clostridia
Neurotoxic Clostridia
Clostridium that causes disease by production of potent exotosins (neurotoxins) of tetanus and botulism (not food botulism)
What are the Histotoxic and invasice clostridium species?
C. chauvoei (black leg)
C. septicum (malignant edema and braxy)
C. novyi (Types A, B, C- gas gangrene, black disease, ost)
C. perfringens (gas gangrene)
C. perfringens (gas gangrene)
Gangrenous and emphysematous myositis. Caused wound colonization after soil, and to a lesser extent intestinal tract, contamination. Primarily seen in times of war as a result of non-sterile field hospitals and projectile wounds. The term gas gangrene refers to swelling of tissues due to release of gas, as fermentation products of clostridia
What are the Neurotoxic Clostridium species?
C. tetani - TeNT - tetanus (exotoxin tentanopasmin, AB toxin)
C. botulinum - BoNT
What are some of the disease caused by Neurotoxic Clostridium botulinum?
Food- borne botulism (not infection but an intoxication) Infant botulism (non pasteurized honey) Wound botulism (wound infection) Botox related botulism
Clostridium botulinum in animals food related.
Flaccid paralysis. Not an infection but a intoxication. Animals ingesting large amounts of toxins. Eg. dead fish or grass with lots of toxins.
Clostridium botulinum characteristics?
Multiply in dead carcass and produce toxin.
Eating spoiled foods in which the toxin has been produced under anaerobic conditions.
Different types of toxin (A-G) preference in what they attack.
Neurotoxin: heat-labile protein - destroyed when food is cooked properly
Clostridium tetani
Spastic paralysis originates from trauma, surgical wound, puncture. Tetanus (Locked jaw or wooden horse). Commonly found in the soil, dust and animal feces. Anaerobic conditions
What are the same about Neurotoxins - BoNT & TeNT?
Same mode of action: bind to neuromuscular junctions. Cleaves synaptobrevin and prevent release of neurotransmitter acetylcholine.
What are the different about Neurotoxins - BoNT & TeNT?
Different site of action: BoNT-peripheral neurons- flaccid paralysis. TeNT - central nervous system- spastic paralysis.
What are the two Enterotoxigenic Clostridium
C. perfringens
C. difficile
What is the only gram negative Clostridium?
Atypical Clostridium pilliforme
What is Clostridium pilliforme
It is a an atypical obligate intracellular pathogen that causes Tyzzer disease and colitis in rodents, rabbits and horses.
