Survey of medical bacteriology I - Kozel Flashcards
What are the classifications of bacterial pathogens?
- aerobic, gram-pos cocci or rods
- aerobic, gram-neg cocci or rods
- anaerobes
- mycobacteria/acid fast bacteria
- spirochetes
- miscellaneous bacteria
What is streptococcus pyrogenes classified as?
Aerobic, gram-pos cocci.
Name some characteristics of S. pyrogenes.
- forms chains
- is beta hemolytic on blood agar
- Has group specific carbohydrate - Group A
- Has type specific protein - Group M
- Has numerous toxins, adhesins and antiphagocytic components
How can you identify S. pyrogenes?
- it is catalase negative
- it is bacitracin sensitive
- it has the Group A antigen
Name some suppurative (pus-forming) infections caused by S. pyrogenes.
- pharyngitis
- scarlet fever
- pyoderma
- erysipelas
- streptococcal toxic shock syndrome
- cellulitis
- necrotizing fasciitis
Name some non-suppurative diseases caused by S. pyrogenes.
- rheumatic heart disease
2. acute glomerulonephritis
What is Streptococcus agalactiae classified as?
Aerobic, gram-pos cocci.
Name some characteristics of S. agalactiae.
- forms chains
- is beta hemolytic
- contains Group B-GBS group specific cell wall carbohydrate
- contains a type specific antiphagocytic capsular polysaccharide
How can you identify S. agalactiae?
It is catalase negative, CAMP positive and has a Group B antigen.
What major diseases are caused by S. agalactiae?
- menengitis in newborns
- early onset neonatal disease
- late onset neonatal disease
- various disseminated infections in adults
What is Viridans streptococci classified as?
Aerobic, gram-pos cocci.
Name some characteristics of Viridans streptococci.
- forms chains
- is alpha hemolytic
- has no carbohydrate anitgen
- has many species
How can you identify Viridans streptococci?
It is catalase negative and optochin resistant. Must differentiate from alpha hemolytic S. pneumoniae - S. pneumoniae is optochin sensitive.
Name some different species of Viridans streptococci.
- S. mitis
- S. mutans
- S. salivaris
Name some diseases caused by Viridans streptococci.
- endocarditis
- dental caries
- bacteremia in neutropenic patients
What is the difference between alpha and beta hemolysis?
Some bacteria have the ability to break down RBC’s - called hemolysis. When these bacteria are placed on a blood agar their different ways of causing hemolysis results in different colors in the agar. Alpha hemolysis is caused by hydrogen peroxide produced by the bacteria. This oxidizes hemoglobin and makes the agar look green. Beta hemolysis is the complete break down of the RBC caused by an exotoxin called streptomycin. This results in the agar turning a light yellow to clear color.
What is Streptococcus pneumoniae classified as?
Aerobic, gram-pos cocci.
Name some characteristics of S. pneumoniae.
- forms Lancet-shaped pairs
- alpha hemolytic
- contains an antiphagocytic capsular polysaccharide
- there is a vaccine for this bacteria that targets the capsular polysaccharide or a CPS-protien conjugate
How can you identify S. pneumoniae?
It is catalase negative, bile soluble and optochin sensitive. The fact that it is optochin sensitive is a way to differentiate between it and Viridans streptococci.
Name some major diseases caused by S. pneumoniae.
- pneumonia
- meningitis
- bacteremia
- sinusitis and otitis media
- sickle cell disease is a risk factor
How is Staphylococcus aureus classified?
Aerobic, gram-pos cocci.
Name some characteristics of S. aureus.
- forms clusters
- has adhesive and antiphagocytic factors, toxins and virulence enzymes
- can be resistant to antibiotics - MRSA - has an altered PBP encoded by mecA gene
How can you identify S. aureus?
It is catalase positive, coagulase positive and has Protein A on its surface.
Name some suppurative infections caused by S. aureus.
- impetigo
- folliculitis
- furuncles/boils
- carbuncles
- bacteremia
- endocarditis
- osteomyelitis
- septic arthritis
- pneumonia and empyema (collection of pus in a naturally existing anatomical space such as pleural cavity)
- brain abscess
Name some toxin-mediated diseases caused by S. aureus.
- food poisoning
- toxic shock syndrome
- scalded skin syndrome
What is Lancefield grouping?
It is a method of grouping B-hemolytic bacteria based on the carbohydrate composition of their cell wall antigens.
How are coagulase-negative staphylococci classified?
Aerobic, gram-pos cocci.
Name some characteristics and identifiers of coagulase-negative staphylococci.
- catalase positive
- coagulase negative
- extracellular polysaccharide contributes to biofilm
Name some major diseases caused by coagulase-negative staphylococci.
- endocarditis
- catheter and shunt infections
- urinary tract infections
- UTI’s in young, sexually active women - mainly by the species Staphylococcus saprophyticus
What is the primary species of coagulase-negative staphylococci that causes clinical disease.
S. epidermidis - also S. saprophyticus causes UTI’s in young, sexually active women.
What is coagulase positivity?
Some bacteria produce coagulase - this enzyme catalyzes change of fibrinogen to fibrin. If present it will cause blood an plasma to clot- this is used diagnostically to differentiate between certain bacterias such as S. aureus.
How is Neisseria gonorrhoeae classified?
Aerobic gram negative cocci.
Name some characteristics of N. gonorrhoeae.
- forms diplococci
- multiple virulence factors/antigens on its surface
- resistant to most antibiotics - ceftriaxone now in use
- can diagnose by nucleic acid amplification
Name som major diseases caused by N. gonorrhoeae.
- gonorrhea
- disseminated infections - spread to skin or joints
- ophthalmia neonatorum - ocular infection acquired at birth
How is Neisseria meningitidis classified?
Aerobic, gram-neg cocci.
Name some characteristics of N. meningitidis.
- forms diplococci
- has antiphagocytic Group-specific capsular polysaccharide
- there is a vaccine against capsular polysaccharide or CPS-protein conjugate
Name some major diseases caused by N. meningitidis.
- menengitis - in young adults
- meningococcemia - disseminated infection with petechia and purport
- repeated attacks in patients with deficiencies in terminal complement proteins
How is Bacillus anthraces classified?
Aerobic, gram-pos rod.
Name some characteristics of B. anthracis.
- large, spore-forming rod
- has an antiphagocytic capsular polypeptide made from poly-glutamic acid
- has 3 exotoxins - protective antigen (PA), edema factor (EF), and lethal factor (LF)
4 is treated with ciprofloxacin
Name some major diseases caused by B. anthraces.
- cutaneous anthrax - forms a black eschar
- gastrointestinal anthrax - ulcers at site of invasion
- inhalation anthrax - non-specific signs followed by severe sepsis
How is Bacillus cereus classified?
Aerobic, gram-pos rod.
Name some characteristics of B. cereus.
- large, spore-forming rod
- ubiquitous in soil worldwide
- has two enterotoxins
Name some major diseases caused by B. cereus.
- food poisoning - vomiting and diarrheal forms
- ocular infection - traumatic penetrating injury
- severe pulmonary disease- severe anthrax-like pulmonary disease in immunocompetent patients
How is Listeria monocytogenes classified?
Aerobic, gram-pos rod.
Name some characteristics of L. monocytogenes.
- is a motile coccobacilli
- is a facultative intracellular pathogen
- grows at 4 degrees celsius - especially in contaminated food
- treatment via penicillin alone or with gentamycin
Name some major diseases caused by L. monocytogenes.
- contaminated food or transplacental spread
- neonatal disease - early onset
- is influenza-like or asymptomatic in healthy adults
- source of in utero infection - usually during third trimester - called early onset before birth and late onset after birth
How is Erysipelothrix rhusiopathiae classified?
Aerobic, gram-pos rod.
Name some characteristics of E. rhusiopathiae.
- thin, pleomorphic rods in filaments
- zoonotic - colonizes swine, turkeys, fish - is an occupational disease in humans
- treatment with penicillin
Name some major diseaes caused by E. rhusiopathiae.
- Erysipeloid - painful, pruritic inflammatory skin lesion at sites of trauma
- generalized cutaneous disease - diffuse cutaneous infection
- septicemia leading to endocarditis (uncommon)
How is Corynebacterium diphtheriae classified?
Aerobic, gram pos rod.
Name some characteristics of C. diphtheria.
- pleomorphic
- produces diptheria toxin - A-B toxin inactivates EF-2
- grown on special media - cysteine-tellurite agar
- has vaccine - to diphtheria toxin
Name some diseases caused by C. diphtheriae.
- respiratory diphtheria - starts with exudative pharyngitis evolving to pseudomembrane then releases toxins causing myocarditis and neurotoxicity
- cutaneous diphtheria - chronic, non-healing ulcer following contact with infected person.
How are pathotypes Escherichia coli classified?
Aerobic, gram-neg rod. There are many strains of E. coli. The pathogenic strains are further classified under five different pathotypes.
Name some characteristics of E. coli.
- They are fermentative (fermentation if no O2 available) rods
- Some strains are normal flora of the GI tract
- There are 5 different pathogenic groups with distinct toxins
Name some diseases caused by E. coli.
- gastroenteritis - five major groups with distinct sites of action, symptoms and virulence factors
- urinary tract infection - most common cause
- neonatal meningitis
- septicemia
What are the 5 pathotypes of E. coli?
- Uropathogenic (UPEC)
- Enterotoxigenic (ETEC)
- Enteropathogenic (EPEC)
- Enteroinvasive (EIEC)
- Enterohemorrhagic 0157:H7 (EHEC)
- Enteroaggregative (EAEC) - has same toxin as EHEC.
Describe UPEC.
Uropathogenic E. coli. This E. coli pathotype produces the exotoxin a-hemolysin, triggers inflammation and is an opportunistic infector.
Describe ETEC.
Enterotoxigenic E. coli. This pathotype produces the exotoxin a-hemolysin, triggers inflammation and is involved in UTI’s.
Describe EPEC.
Enteropathogenic E. coli. This pathotype produces the exotoxins Labile toxin (LT) and Stable toxin (ST), causes hypersecretion leading to watery diarrhea.
Describe EIEC.
Enteroinvasive E. coli. This pathotype triggers inflammation, produces ulcers and causes dysentery.
Describe EHEC 0157:H7.
Enterohemorrhagic E. coli. This pathotype produces Shiga toxin. This toxin binds to and colonizes the small intestines (also can bind in the kidneys) and causes hemorrhage leading to bloody diarrhea and hemolytic uremic syndrome.
Describe EAEC.
Enteroaggregative E. coli. This pathotype also produces Shiga toxin. It is involved in producing adherent biofilm and causing watery or blood diarrhea and hemolytic uremic syndrome.
How is Salmonella enterica classified.
Aerobic gram-neg rod.
Name some characteristics of S. enterica.
- is a non-fermenting rod
- most infections via contaminated food such as poultry or eggs.
- has over 2500 O serotypes
- The serovars Typhi and Paratyphi are highly adapted to humans.
Name some diseases caused by S. enterica.
- Gastroenteritis - infectious dose lower if reduced gastric acidity.
- Septicemia
- Enteric fever - typhoid fever produces by S. Typhi.
- Asymptomatic colonization - usually gallbladder, carrier for infection by S. Typhi and S. paratyphi.
How are the Shigella species classified?
Aerobic, gram-neg rods.
Name some characteristics of the Shigella species.
- They are non-fermenting rods.
- There are 4 species
- They produce Shiga toxin that damages intestinal epithelium and A-B toxin that blocks protein synthesis.
- Humans are their only reservoir.
What are the 4 Shigella species?
- S. sonnei
- S. flexneri
- S. dysenteriae
- S. boydii
Name some diseases caused by the Shigella species.
- Shigellosis - a type of gastroenteritis characterized by watery diarrhea (caused by enterotoxin), abdominal cramps, fever and bloody stool.
- Asymptomatic carriers are a reservoir.
How are the Yersinia species classified?
Aerobic, gram-neg rods.
Name some characteristics of Yersinia.
- zoonotic- rats, sqirrels, rabbits and domestic animals
- Y. pestis is the flea vector
- There have been 3 major pandemics caused by this bacteria.
Name some diseases caused by Yersinia.
- Bubonic plague- spread via fleas
- Pneumonic plague - spread via aerosol
- Y. enterocolitica and Y. pseudotuberculosis - cause enterocolitis following ingestion of infected meat, milk or water.
Name some clinically important Yersinia species.
- Y. pestis
- Y. enterocolitica
- Y. pseudotuberculosis
How is Klebsiella pneumoniae classified?
Aerobic, gram-neg rods.
Name some characteristics of K. pneumoniae.
- Can also be fermentative.
- Is encapsulated so has antiphagocytic properties.
- Has a strain that is resistant to carbapenemase - CRKP or Carbapenem-resistant K. pneumniae.
Name some diseases caused by K. pneumoniae.
- Pneumonia - usually patients with impaired pulmonary defense such as diabetes, alcoholism, malignancy or COPD. The symptoms include bloody, mucoid sputum.
- UTI
- Sepsis
How is Proteus mirabilis classified?
Aerobic, gram-neg rods.
Name some characteristics of P. mirabilis.
- Urease positive
- motile - can be seen on bacterial plates
- makes urine alkaline leading to struvite crystals in kidneys (kidney stones) - urease hydrolyzes urea to ammonia
What disease does P mirabilis cause?
UTI with crystal formation.
How is Serratia marcesens classified?
Aerobic, gram-neg rods.