Gram negative rod II Flashcards
What are the names of gram-negative bacteria?
Pseudomonas
Vibrio
Campylobacter
Helicobacter
Neisseria
Gram-negative bacteria, oxidase-positive, motile, aerobic bacilli.
Produce water-soluble pigment.
Occur widely in soil, water, plants, and animals.
Pseudomonas
Gram-negative, motile, aerobic rods, oxidase-positive, singly or pairs.
Widely distributed in nature and is commonly present in moist environments in hospitals.
Can produce multiple colony types.
Pseudomonas aeruginosa
Catalyzes the production of superoxide and hydrogen peroxide and causes tissue damage. Non-fluorescent bluish pigment.
Pyocyanin
Fluorescent pigment which gives a greenish colour to the agar
Pyoverdin
A red pigment, which is soluble in water but insoluble in alcohol
Pyorubin
A brown/black pigment
Pyomelanin
Are all strains of Pseudomonas pigmented?
No
Toxins:
- Exotoxin A: prevents the synthesis of proteins in eukaryotic cells
- Exoenzymes S and T: show adenosine diphosphate transferase activity, inhibit protein synthesis, and cause immunosuppression
Enzymes:
- Elastase: destroys elastin
- Alkaline protease: tissue destruction
- Phospholipase C: tissue destruction by breaking down lipids and lecithin
Cell wall components:
- Pili: adhesion of bacteria to the epithelial cells
- LPS: endotoxic activity, sepsis
- Pyocyanin: causes tissue damage, inflammation
P. aeruginosa
- An opportunistic pathogen
- Causes infections in immunocompromised host
- Respiratory tract infections: cystic fibrosis (thick, sticky mucus blocks the airway), bronchopneumonia, and lobar pneumonia.
- Skin infections: burn wound, chronic paronychia, infected toe web, pseudomonal folliculitis, and pseudomonal cellulitis.
- UTI
- Ear infections (swimmer’s ear)
- Eye infections: wearing contact lens are at increased risk of developing Pseudomonal infection
- Endocarditis, osteomyelitis, and secondary septicemia.
P. aeruginosa
Small, gram-negative, curved bacilli, motile, and oxidase positive.
Vibrio
What are the two main human pathogens in Vibrio?
V. cholera and V. parahemolyticus
Curved gram-negative rods, fermentative, aerobic and facultative anaerobic, non-sporing, and require salt for growth.
Natural inhabitants of seawater but are also found in freshwater.
Halophilic: widely distributed in marine environments.
Water-borne or associated with water-living animals.
Can multiply freely in water.
Never found in normal human.
Isolated from gastrointestinal tract and faeces of infected individuals/
V. cholerae
Cholera toxin: inhibits the absorption of sodium and chloride in the intestine, which causes hypersecretion of large volumes of water.
Toxin coregulated pilus: helps in adherence
Accessory colonization: helps in adhesion
Haemagglutination-protease (mucinase): induces intestinal inflammation and helps to release the bacteria
Neuraminidase: increases toxin receptors
V. cholerae
Causes cholera, epidemic diarrheal disease. Appearance of stool “rice-water” like. They do not reach the bloodstream but remain in gastrointestinal tract.
V. cholerae
Cause of seafood-associated gastroenteritis.
Major toxin is the Kanagawa toxin (Ka), Thermostable direct haemolysin (TDH), enterotoxin, cytotoxin, cardiotoxic, inducing oedema, erythema, and capillary permeability.
Haemolytic on human blood but not sheep’s blood agar.
V. parahaemolyticus
Thin, gram-negative, comma-shaped/curved bacilli, motile with single polar flagellum, micro-aerophilic growth condition.
Mild severe diarrhea, stool with blood and leukocytes, fever, nausea, and abdominal pain.
Campylobacter
Gram-negative rods with comma, S, or gull wing shapes. They are motile, with a single polar flagellum, and do not form spores.
Oxidase and catalase positive. Do not oxidize or ferment carbohydrates. Microaerophilic, which means require atmosphere with decreased oxygen concentration and increased carbon dioxide concentration for their growth.
C. jejuni
Causes enteric infections, abdominal pain, profuse diarrhea that may be grossly bloody, headache, malaise, and fever.
Post-diarrheal Guillain-Barré syndrome, a form of paralytic disease.
C. jejuni
Enterotoxins: adherence
LPS: adhesion
PEB1: antigen and major adhesion protein
Adhesion proteins: adhesion
Cytotoxic enzymes: cytotoxicity action
S protein: found in fetus and inhibits c3b binding
C. jejuni
Inhabit stomach of humans and many other mammals such as monkeys, dogs, and cats.
Spiral or helical morphology, gram-negative, non-sporing, and micro-aerophilic.
Motile, sheathed flagella, catalase and oxidase positive, a strong producer of urease, and causes peptic ulcer, gastric, and duodenal ulcers.
Helicobacter pylori
Cause alteration of gastric acid production, gastric inflammation, and tissue destruction.
H. pylori
Urease: helps in colonization
Flagella: helps to penetrate into gastric mucosa layer and protects the bacteria from acid environment of the stomach
Adhesins: facilitate binding
Enzymes: break down gastric mucus and prevent phagocytic killing of the bacteria
Heat shock protein: facilitate expression of the enzyme urease
cytotoxin: causes vacuolation
H. pylori
Gram-negative, aerobic, non-sporing, non-motile cocci, arranged in pairs with adjacent sides flattened together. Individual cocci are kidney shaped.
Fastidious, sensitive to low temperature and drying.
Oxidase and catalase positive.
Ferment sugars with production of acid but no gas.
Neisseria
What are the two species under Neisseria?
Neisseria gonorrhoea (Gonococcus)
Neisseria meningitidis (Meningococcus)
causes gonorrhea, neonatal conjunctivitis, and pelvic inflammatory disease (PID).
gonorrhea - sexually transmitted disease, infected kidneys, UTI, burning sensation when urination, inflammation of the penile, swollen testicles, and discharge from the penis.
disseminated gonococcal infections
ophthalmia neonatorum - bilateral conjunctivitis of a neonate by vaginal delivery from an infected mother and blindless is an important complication of this condition.
cause disease only in humans
N. gonorrhoeae
gram-negative diplococci, polysaccharide capsule -, have pili to adhere to the epithelial cells, produce toxins (endotoxin and exotoxin)
N. gonorrhoeae
Capsule - prevents phagocytosis
Pili - Adhere to epithelial cells
Por proteins
Opa proteins
Rmp proteins
N. gonorrhoeae
gram-negative diplococci, oxidase-positive, produce toxins (endotoxin and exotoxin), LPS (responsible for endotoxic effect).
have a prominent polysaccharide capsule to survive the hostile environment.
have pili to adhere to the epithelial cells
serotype A is the leading cause of epidemic meningitis
N. meningitidis
Causative agent of meningitis
Human are the only natural host
Inhabit mainly in nasopharynx
Transmitted via droplets or close contact and kissing
N. meningitidis
Capsule - prevents phagocytosis
LOS endotoxin - causes damage of the blood vessels
IgA protease - destroys IgA immunoglobulin
Lipooligosaccharides - host cell damage
N. meningitidis
meningococcal meningitis - fever, headache, stiff neck, and increased level of PMNs in spinal fluid
meningococcemia (septicemia) in severe form (Friderichsen syndrome) - high fever, DIC, purpuric skin rashes, shock, and multi-organ failure
N. meningitidis
