IID 02: Disease-causing Pathogens Flashcards
What are the 4 types of infectious pathogens?
- bacteria
- virus
- fungi
- protozoa
What are the different classifications of disease-causing pathogens? (2)
- cell wall
- shape
What are the 3 main groups of disease-causing pathogens based on cell wall characteristics?
- gram-positive
- gram-negative
- unique cell wall/no cell wall
What are the 7 shapes of disease-causing pathogens?
- cocci
- coccobacilli
- bacilli
- vibrios
- spirilla
- spirochetes
- actinomycetes
Describe the cocci shape.
spherical/oval
Describe the coccobacilli shape.
elongated oval shaped
Describe the bacilli shape.
rod shaped
Describe the vibrios shape.
comma shaped
Describe the spirilla shape.
rigid spiral forms
Describe the spirochetes shape.
flexible spiral forms
Describe the actinomycetes shape.
branching filamentous
Describe gram-positive stains.
purplish-blue
Describe gram-negative stains.
pinkish-red
Gram-positive
What are the two main shapes of gram-positive bacteria?
- cocci
- bacilli
Gram-positive Cocci
What are the two types of cocci bacteria?
What test is done to determine the type?
catalase test
- streptococci (chains) – negative, no bubbles
- staphylococci (clusters) – positive, bubbles
What is the catalase test?
enzyme produced by microorganisms that rapidly converts hydrogen peroxide to water and free oxygen
- positive reaction: immediate effervescence (bubble formation)
- negative reaction: no bubble formation
Gram-positive Cocci
What are the 3 types of streptococci (chains)?
What test is done to determine the type?
hemolytic test
- alpha-hemolytic – green zone
- beta-hemolytic – clear/yellowish zone
- gamma-hemolytic – no hemolysis
Gram-positive Cocci
What is alpha-hemolysis?
alpha-hemolysin partially breaks down RBCs, resulting in a ‘green zone’ surrounding the bacterial colonies
Gram-positive Cocci
What is beta-hemolysis?
beta-hemolysin completely breaks down red blood cells and hemoglobin, leaving a ‘clear/yellowish zone’ around the bacterial colonies
Gram-positive Cocci
What is gamma-hemolysis?
no hemolysis
Gram-positive Cocci
What are alpha-hemolytic bacteria?
- normal flora of nasopharynx
- possible pathogen in: pneumonia, otitis media, sinusitis, meningitis
- ie. streptococcus pneumoniae, viridans streptococci
Gram-positive Cocci
What are beta-hemolytic bacteria?
- normal flora of oropharynx, colonizer of skin
- possible pathogen in: pharyngitis, tonsillitis, cellulitis
- ie. group A streptococci (S. pyogenes), group B streptococci (S. agalactiae)
Gram-positive Cocci
What are gamma-hemolytic bacteria?
- normal flora of GI/GU tract
- possible pathogen in: UTI, intra-abdominal infection, endocarditis
- human pathogens (E. facaelis and E. faecium)
- ie. enterococcus
What is minimum inhibitory concentration (MIC)?
lowest concentration of antibiotic which prevents visible growth of a bacteria
- used in antimicrobial susceptibility testing – ie. E-test, broth dilution method
Gram-positive Cocci
Describe the resistance of streptococcus.
- drug-resistant streptococcus pneumonia emerging
- vaccination with pneumococcal conjugate vaccine associated with decreased rates of resistance
Gram-positive Cocci
Describe the resistance of enterococcus.
- vancomycin-resistant enterococci (VRE)
- 30% resistance rate in US
- associated with healthcare or long-term care exposure
Gram-positive Cocci
What are the 2 types of staphylococci (clusters)?
What test is done to determine the type?
coagulase test
- coagulase (+)
- coagulase (-)
What is the coagulase test?
enzyme produced by some bacteria that forms clots when applied to plasma
- coagulase positive: presence of coagulase converts fibrinogen to fibrin (clot)
- coagulase negative: no clot formation
Gram-positive Cocci
What are coagulase positive bacteria?
- normal flora on skin
- invasive pathogen
- possible pathogen in: cellulitis, osteomyelitis, septic arthritis, endocarditis
- ie. staphylococcus aureus
Gram-positive Cocci
What are coagulase negative bacteria?
- normal flora on skin
- less pathogenic than S. aureus
- common contaminant
- possible pathogen in: osteomyelitis with prosthetic device, infection in immunocompromised host
- ie. coagulase-negative staphylococci/CoNS (staphylococcus epidermidis)
Gram-positive Cocci
What is methicillin resistant staphylococcus aureus (MRSA)?
- spread in healthcare settings and community
- more common (16x) in those who inject illicit drugs
Gram-positive Bacilli
What are the 2 types of bacilli?
What test is done to determine the type?
oxygen test
- aerobic – require oxygen for growth/survival
- anaerobic – do not require oxygen for growth/survival, oxygen may negatively impact growth
Gram-positive Bacilli
What are some examples of aerobic bacteria? (2)
- listeria
- corynebacterium
Gram-positive Bacilli
What are some examples of anaerobic bacteria? (1)
- peptostreptococcus
Gram-positive Bacilli
What is the listeria species?
- found in unpasteurized milk
- cause of listeriosis: severe sepsis, meningitis, encephalitis
Gram-positive Bacilli
What is the corynebacterium species?
- causes diphtheria (C. diptheriae)
- vaccination: 2, 4, 6 months (DTaP-HB-IPV-Hib), 18 months (DTaP-IPV-Hib)
Gram-positive Bacilli
What are the 2 types of anaerobic bacteria?
- spore-forming – ie. clostridium
- non-spore forming – ie. lactobacillus
Gram-positive Bacilli
What is the clostridium species?
- C. difficile – pseudomembranous colitis
- C. tetani – tetanus (vaccination at 2, 4, 6 months (DTaP-HB-IPV-Hib), 18 months (DTaP-IPV-Hib))
- C. botulinum – botulism
Gram-positive Bacilli
What are C. difficile infections associated with?
associated with those who have taken antibiotics for other purposes
- most common healthcare-associated infection
Gram-positive Bacilli
What are some strategies to reduce C. difficile infections?
- improving antibiotic use
- infection control
- healthcare facility cleaning and disinfection
- personal hygiene
Gram-negative
What are the two main shapes of gram-negative bacteria?
- cocci
- bacilli
Gram-negative Cocci
What are the two types of cocci bacteria?
What determines the type?
arrangement/shape
- diplococci
- coccibacci
Gram-negative Cocci
What are some examples of diplococci shaped bacteria? (2)
- neisseria species
- moraxella species
Gram-negative Cocci
What are some examples of coccobacilli shaped bacteria? (2)
- haemophilus influenzae
- bordetella pertussis
Gram-negative Cocci
What is neisseria meningitidis?
- found in nasopharynx
- possible pathogen in: meningitis, bacteremia
Gram-negative Cocci
What is neisseria gonorrheae?
- possible pathogen in: urethritis/cervicitis, pelvic inflammatory disease, neonatal conjunctivitis
- causes gonorrhea (STI)
- can result in life-threatening ectopic pregnancy and infertility
- increases risk of contracting HIV
Gram-negative Cocci
What is moraxella catarrhalis?
- found in nasopharynx
- possible pathogen in: pneumonia, otitis media, sinusitis, bronchitis
Gram-negative Cocci
What is haemophilus influenzae?
- colonized in nasopharynx
- possible pathogen in: bronchitis, otitis media, sinusitis, pneumonia, meningitis
- vaccination: 2, 4, 6 months (DTaP-HB-IPV-Hib), 18 months (DTaP-IPV-Hib)
Gram-negative Cocci
What is bordetella pertussis?
- pathogen in: pertussis (whooping cough)
- vaccination: 2, 4, 6 months (DTaP-HB-IPV-Hib), 18 months (DTaP-IPV-Hib)
Gram-negative Cocci
Describe the resistance of neisseria gonorrheae.
half of all infections resistant to at least one antibiotic
Gram-negative Bacilli
What are the two types of bacilli bacteria?
What test is done to determine the type?
oxygen test
- aerobic – require oxygen for growth/survival
- anaerobic – do not require oxygen for growth/survival, oxygen may negatively impact growth
Gram-negative Bacilli
What are the two types of aerobic bacteria?
What test is done to determine the type?
lactose fermentation test
- lactose fermenter
- lactose non-fermenter
What is the lactose fermentation test?
when microorganisms ferment carbohydrate (ie. lactose), an acid or acid with gas are produced
- positive – liquid turns yellow which indicates a drop in pH due to acid production (fermentation), gas production may occur
- negative – liquid remains red as a result of no fermentation, no gas production will occur
Gram-negative Bacilli
What are some examples of lactose fermenters?
- proteus
- serratia
- escherichia coli
- citrobacter
- klebsiella
- enterobacter
Gram-negative Bacilli
What are some examples of non-lactose fermenters?
- pseudomonas
- acinetobacter
- salmonella
- shigella
Gram-negative Bacilli
What is enterobacteriaceae?
- many species live within normal flora of intestine
- some species possess high rates of resistance to commonly used antibiotics
- ie. E. coli, Klebsiella, Enterobacter, Citrobacter, Salmonella, Shigella
Gram-negative Bacilli (Aerobic)
What is ‘easy’ GNB?
- non-beta lactamase producing
- ie. H. influenzae, E.coli, Klebsiella
Gram-negative Bacilli (Aerobic)
What is ‘hard’ GNB?
- ESBL – extended spectrum beta-lactamases
- HECK YES – Hafnia alvei, Enterobacter cloacae, Citrobacter, Klebsiella, YErSinia
Gram-negative Bacilli
What are 3 types of resistance?
- broad spectrum beta-lactamases (BSBL)
- extended spectrum beta-lactamases (ESBL)
- carbapenemases
Gram-negative Bacilli
What are broad spectrum beta-lactamases (BSBL)?
enzymes which rapidly break down commonly used beta-lactam structured antibiotics
- confer resistance to many penicillins and first-generation cephalosporins
- second, third and fourth gen. cephalosporins, carbapenems still considered active
Gram-negative Bacilli
What are extended spectrum beta-lactamases (ESBL)?
- confer resistance to third, and sometimes fourth generation cephalosporins
- ESBL producing enterbacteriaceae often cause infection in otherwise healthy patients
- limited antibiotic choices for treatment
Gram-negative Bacilli
What are carbapenemases?
- confer resistance to the same antimicrobials as ESBL plus second generation cephalosporins and carbapenems
- nearly resistant to all available antibiotics
- new antibiotics/combinations being investigated for activity
Gram-negative Bacilli
What are some examples of anaerobic bacteria? (1)
- bacteroides species
What are anaerobic bacteria?
- infections commonly associated with: abscess, foul odour or discharge, tissue necrosis, gangrene
- possible pathogen in: intra-abdominal infections, aspiration pneumonia, abscess
Unique Cell Wall/No Cell Wall (Atypicals)
Describe this type of bacteria.
- chemically unique cell wall or no cell wall present
- colour not apparent on gram stain
- possible pathogens in: respiratory infections, pelvic inflammatory disease, sexually transmitted infections
- consider antibiotics with mechanisms other than cell wall disruption – ie. macrolides (ribosomal interactions), tetracyclines, fluoroquinolones
- ie. chlamydia, mycobacterium species (tuberculosis, leprosy), mycoplasma
Pathogenic Viruses
Describe pathogenic viruses.
- structurally unique as carry little other than information in the form of nucleic acid – use living host cells for replication
- possible pathogen in almost all forms of infectious diseases
Pathogenic Viruses
Describe drug treatment.
identifying effective antiviral targets is difficult as viral replication uses host cell machinery
Pathogenic Viruses
Describe vaccinations.
vaccination programs can be effective for control/eradication (ie. smallpox, polio)
What are some examples of pathogenic fungi? (4)
- candida species
- cryptococcus species
- aspergillus species
- pneumocystis species
Pathogenic Fungi
What is the candida species?
- yeast
- normal flora in gut
- possible pathogen in: oropharyngeal candidiasis, vulvovaginal candidiasis, fungemia
Pathogenic Fungi
What is the cryptococcus species?
- yeast
- possible pathogen in: immunocompromised patients
Pathogenic Fungi
What is the aspergillus species?
- commonly found in soil
- possible pathogen in: immunocompromised patients
Pathogenic Fungi
What is the pneumocystis species?
- possible pathogen in: immunocompromised patients (pneumonia)
What are some examples of pathogenic protozoa? (4)
- giardia duodenalis
- plasmodium species
- trichomonas vaginalis
- toxoplasma gondii
Pathogenic Protozoa
What is giardia duodenalis?
- cause of giardiasis (beaver fever) – diarrhea, abdominal pain, weight loss
- source: water contamination
Pathogenic Protozoa
What is plasmodium species?
- cause of malaria – fever, fatigue, vomiting, yellow skin, seizure
- source: mosquito
Pathogenic Protozoa
What is trichomonas vaginalis?
- cause of trichomoniasis – genital itching, burning
- source: sexual contact
Pathogenic Protozoa
What is toxoplasma gondii?
- cause of toxoplasmosis – flu-like symptoms (severe if immunocomprpmised), congenital toxoplasmosis
- source: undercooked meat, cate feces
