L2 Gram Positive Rods Flashcards
Genus Bacillus
- > 60 species
- Diverse ecological niches
- Most are non pathogenic to humans
- Not anaerobic (is not poisoned by oxygen)
- Phenotypic differences conferred by genes on plasmids
Bacillus cereus
Typically found in rice especially reheated rice dishes
Produces enterotoxin - works in bowels
Food poisoning including diarrhoea
bacillus thuringiensis
Used as an insecticide
Produces protein crystals when producing spores
□ destroy the gut function of certain insects
□ Genetically over 500 different types
□ Encoded by cry genes which are located on a plasmid
□ Toxic to mosquitos and moths and caterpillars
Cry genes can be inserted into crop genomes to make them insect resistant
Used to control river blindness caused by onchocerca volvulus transmitted by blackflies breeding in fast flowing streams in Africa
□ Causes microfilaria damage to the eye
□ Used to poison blackflies
Used to control Ross River virus in Australia in the south west where mosquitos breed by dropping a sludge from helicopters
food poisining from reheated rice dishes is caused by
bacillus cereus
insecticide that destroys the gut function of insects
bacillus thuringiensis
cry genes
- encode protein crystals which destroy gut functions of some insects
- encoded on a plasmid in bacillus thuringiensis
- toxic to mosquitos, moths, and catarpillars
- can be inserted into crop genomes to make them insect repellant
bacteria used to control Ross River virus in south west
- bacillus thuringiensis
- used to control mosquitos
bacteria used to control river blindness
- bacillus thuringiensis
- controls onchocerca volvolus transmitted by blackflies
- causes microfilarial damage to the eye
anthrax caused by
bacillus anthracis
bacillus anthracis
Highly virulent pathogen Soil organism Zoonotic infection for animals that graze on grass and plants on the ground eg. Sheep, horses Worldwide distribution Causes economic disruption to farming
Anthrax Belt
strip of land in New South Wales from Victoria to Queensland
□ Main focus of human and animal cases in Australia
- Introduced from India in blood and bone meal and infects cattle herds
infective form of bacillus anthracis
- spores
- survival in the environment
- may remain viable for over 100 years
anthrax
- caused by bacillus anthracis
- Humans acquire infection when in contact with infected animals, their meat or other animal products
□ Their spores are the infective form
□ Clinical manifestations are determined by transmission routes
□ Used in biological warfare
3 types of anthrax infection
- cutaneous
- inhalational
- gastrointestinal
cutaneous anthrax
◊ through breakages in the skin
◊ Most common form
◊ Produces papule, vesicle, ulcer and then an eschar
} Eschar: an elevated black scab surrounded by cellulitis and swelling
◊ Swelling and redness
◊ Untreated mortality 10-40%
inhalational anthrax
◊ aerosol or dust causing pulmonary anthrax
◊ Spores are inhaled and enter the lung
◊ Macrophages within the alveoli engulf the spores, but the bacteria survives within the macrophages creating a form with an incubation period of up to 60 days, after which the organism grows within the macrophage
◊ Macrophage carries the bacteria into the surrounding lymph nodes and into the mediastinal lymph nodes where they cause haemorrhagic necrosis of perihilar and other thoracic lymph nodes
◊ Mediastinum: area around heart and in between lungs
◊ Causes a widening of the mediastinum which can be seen on an X-ray
◊ Eventually gets into the lungs and causes haemorrhagic necrosis
◊ 100% untreated mortality rate
gastrointestinal
◊ Though ingestion
◊ contaminated meat causing gastrointestinal anthrax
◊ Inflammation, swelling, haemorrhaging from mouth to caecum
◊ Up to 50% untreated mortality
how are phenotypic differences conferred between species of bacillus
genes on plasmids
genus clostridium
- Spore forming anaerobic bacteria
- Spores persist in the environment and are the infective form
- Produce toxins responsible for their diseases
Classified according to which toxins they produce
3 things caused by clostridium perfringens
gas gangrene
food poisoning
enteritis necroticans (pig bel)
gas gangere is caused by
clostridium perfringens
pig bel is caused by
clostridium perfringens
gas gangrene
Clostridial myonecrosis
Spores introduced into open or traumatic wounds
Common issue in old warfare where it was contracted through injuries from soil and dirt
Rapid invasion and liquefactive necrosis of muscle and surrounding tissue
gas production in tissue
food poisoning from clostridium perfringens
§ Ingestion of meat contaminated by growing bacteria
§ During spore formation in small intestine, elaboration of potent enterotoxin
§ Crampy abdominal pain, diarrhoea, self limiting
pig bel
§ Necrotising bowel disease
§ Ingestion of contaminated food together with sweet potato or yams (food rich in trypsin inhibitors, trypsin is a digestive juice)
§ Elaboration of bacterial B-toxin in intestines, which is not destroyed because trypsin was inhibited
§ Necrosis of bowel or bowel segment
§ Sporadic in south pacific, PNG, Africa, Asia
§ Typically in children with protein malnutrition
clostridium tetani
○ Tetanus
○ Spores found in soil
○ Inoculated into would and germinate
○ Produces a powerful neurotoxin - tetanospasmin
○ Blocks inhibitory nerve impulses
○ Disease rare in developed countries due to vaccination
○ Common in developing countries
○ Fatality rate >40%
○ Increased muscle tone and painful spasms
trismus
lockjaw
risus sardonicus
spasms of facial muscles
apnoea
rigidity of muscles of breathing
clostridium botulinum
○ Botulism
○ Rare, potentially life threatening neuroparalytic illness
○ Spores enter the host in food or sometimes wound contamination
○ Typically aged or preserved food
○ Potent neurotoxin
○ Prevents release of acetyl choline and neuromuscular junction
○ Progressive descending paralysis
cause of tenanus
clostridium tetani
cause of botulism
clostridium botulinum
clostridium defficile
○ Profuse diarrhoea that contaminates surfaces
○ In faeces of up to 30% hospital patients
○ Spores persist in the environment
○ Spread on the hands of staff
○ enterotoxin producing strains cause diarrhoea
§ Antibiotic associated diarrhoea
□ During or after antibiotic treatment
□ Mild to severe intractable diarrhoea
§ Pseudomembranous colitis
□ Sever inflammatory condition
□ Colon becomes inflamed and may have to be removed
genus lactobacillus
- Rarely pathogenic
- Normal flora of GIT and vagina
- Non-endospore forming, regular morphology
- Ferment carbohydrates to lactic acid
- maintains vaginal pH at 3.8-4.5
listeria monocytogenes
- Uncommon but serious infections
- Regular morphology, non-endospore forming
- Can still grow in refrigerated conditions
listeria monocytogenes are found in
- Found ○ Water ○ Animal and human faeces ○ Raw meat ○ Dairy products ○ Vegetables - Acquired from high risk foods ○ Coleslaw, raw cabbage ○ Unpasteurised milk ○ Soft cheeses ○ Pate ○ Undercooked chicken Prepacked sliced meats
clinical syndromes of listeria monocytogenes
○ Asymptomatic in those with normal functioning immune system
○ Listeriosis
§ In elderly, infants, immunocompromised, pregnancy
§ Non-specific bacteraemia - flu-like symptoms
§ Septicaemia and/or meningitis (high mortality)
○ Fetal infection if mother is infected by crossing the placenta
§ Miscarriage, stillbirth, prem labour
§ Live birth - septicaemia, meningitis, neurological or other damage
erysipelothrix rhusiopathiae
- Causes Erysipeloid
- Non-endospore forming regular morphology
- From handling meat, poultry, fish, crustaceans, farm animals
- Enters the skin through abrasions
- Painful, raised areas of inflammation of the skin - cellulitis
erisipeloid is caused by
erisipelothrix rhusiopathiae
inflammation of the skin after handling fish, meat, crustacians, farm animals most likely caused by
erysipelothrix rhusiopathiae
genus corynebacterium
- Small, irregular gram positive rods
- ‘Coryneform’ or ‘diphtheroid’ morphology
- Many are commensals of humans and animals (such as the skin)
- Frequent contaminants of blood cultures
- Some of these cause uncommon infections eg. Foreign devices
○ Prosthetic heart valve or joints etc.
corynebacterium diptheriae
○ Diphtheria
○ Major pathogen
○ Serious childhood illness in pre vaccination days and countries without vaccination
○ Caused by endotoxin producing strains of the species
○ Infection of nose and throat but sometimes skin ulcers
○ Inflammation and swelling, pseudomembrane formation in nasopharynx and upper airways
○ Swelling may cause asphyxiation
○ Exotoxin is absorbed into body, severe pathology
○ Myocarditis
§ Damage to the heart muscle
§ Arrythmias
§ Heart failure
○ Neuropathy
§ Paralysis of palate muscles, cranial nerves
§ Peripheral sensory and motor neuropathy
○ Other
§ Focal necrosis in kidneys, adrenal, liver
acne vulgaris caused by
propionibacterium acnes
genus propionibacterium
- Mostly non-pathogenic
- Commensals of the human skin - contaminant of blood cultures
- Coryneform morphology
- Typical contaminant of blood culture
- P acnes has a role in acne vulgaris - facial acne
- Causes infections of implanted foreign devices eg. Heart valves, prosthetic joints
4 filamentous/branching actinomycetes
- Actinomyces
- Nocardia
- Actinomadura
- Streptomyces
3 diseases caused by filamentous/branching actinomycetes
actinomycotic mycetoma
non-mycetoma nocardia infections
actinomycosis
actinomycete mycetoma
§ Most common genera causing disease
□ Nocardia
□ Actinomadura
□ Streptomyces
§ Cutaneous implantation - stick, thorn, splinter
□ More common in developing parts of the world or places where people are likely to walk barefoot
§ Chronic lesion (years), usually the foot
□ Swelling
□ Discharging sinuses (tunnels that discharge pus)
□ ‘granules’ - concretions of bacteria packed together
non-mycetoma nocardia infections
§ In immunocompromised hosts especially in hospital settings
□ People receiving drugs against cancer
□ Inhalation, respiratory infection
□ Lung nodules, pneumonia, cavities
□ Spread through the blood stream from the lungs
□ Abscesses in other organs, can lead to the brain
§ In immunocompetent hosts
□ Skin implantation
□ Nodular/pus-filled lesions tracking up lymphatics
□ This appearance is called ‘sporotrichoid’
® Chronic ulceration lesion on hand or finger where it is implanted
® Over weeks or months there are abscesses moving up the limb
actinomycosis
§ Actinomyces spp.
§ Commensal of the oropharynx, GIT, genital tract
§ An endogenous infection, typical forms being:
□ Cervicofacial -
□ Thoracic -
□ Abdomen, pelvis (longstanding IUD association)
§ Swelling, contiguous spread
§ Discharging fistulas
§ Pus containing granules
