Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
167 Cards in this Set
- Front
- Back
|
Discuss characteristics used in identification of organisms:
|
Lab ident is phenotypic.
╌ Macro and Microscopic morphology ╌ staining characteristics ╌ environmental and nutrient requirements ╌ resistance profiles ╌ antigentic properties ╌ subcellular properties |
|
|
Gram postive cell wall
|
80 nm thick
layered peptidoglycan teichoic acid (holds cell wall and space together so dye is trapped in gram stain) |
|
|
Gram negative cell wall
|
thinner but more complex than G+
periplasmic space allows dye to escape. peptidoglycan--one layer lipopolysaccharides--o antigens or somatic antigens responsible for endotoxins |
|
|
Acid fast cell walls
|
modification of G+
contains mycolic instead of teichoic acids |
|
|
Endospores
|
dormant or resting stage in growth cycle. Formed in responce to nutritional deprivation
Seen only in Bacillus and Clostridium spec. |
|
|
Capsules
|
slime layer external to outer layer of cell wall
|
|
|
Flagella
|
responsible for motility
most common in g- rods, but alls in g+ rods (Listeria) and cocci (Enterococus) |
|
|
Fimbrae or pili
|
adherance and/or genetic exchange
|
|
|
Pathogenicity
|
ability of organism to cause disease
Organism must be able to enter host and cause disease some release toxins that cause pathologic process Must cause host reaction |
|
|
Virulence
|
degree of pathogenicity of species
|
|
|
virulence factors
|
adhesins/receptors
Agressins |
|
|
Functions of virulence factors
|
Extracellular adherance
Impair complement function Lytic effects on neutrophils bind to immunoglobulins |
|
|
Adhesins
|
allow microorganism to bind to cell surface via receptors
|
|
|
Agressins
|
substances that allow organisms to override host defense mechanisms:
surface proteins and carbohydrates enzymes endo- and exotoxins other small molecules |
|
|
Capsules
|
avoid phagocytosis by covering up antigenic compounds
facilitates colonization |
|
|
Surface proteins
|
adherence and virulence
vary by organism |
|
|
catalase and superoxide dismutase
|
ihibit organis destruction by myeloperoxidase system of phagocitic cells
|
|
|
Leukocidins
|
causes degranulation, swelling and lysis of neutrophils
|
|
|
Hyaluronidase
|
depolymerizes hyaluronic acid (responsible for cell-cell adhesion)
|
|
|
streptokinase and staphylokinase
|
hydrolyze fibrin clots to facilitate invasion
|
|
|
collagenase
|
breaks down collagen matrix of muscle and connective tissue
causes necrotizing fascitis and gas gangrene |
|
|
Exotoxins
|
most potent
produced mostly by g+ tetanus diphtheria, botulism and cholera are examples organism must be alive to exude |
|
|
endotoxins
|
produced only by G- organisms
low in toxicity worse when organism is dead. low dose: fever High dose: hypotension, DIC, hemorrhage |
|
|
Siderophores
|
scavenge iron from host
protect against killing effect of normal human serum |
|
|
R factors
|
R factors code for resistance to antimicrobial agents
|
|
|
Plasmids
|
code for sex pili, chromosome mobilization, colonization antigens, serum resistance, iron chelation and transport, toxin and hemolysin production
|
|
|
Primary defenses
Anatomic barriers |
intact skin
nasal hairs cilia in resp tract mucous layer lining gut flow of liquids in resp and intestinal tracts Normal flora |
|
|
Primary defenses
Physiologic factors |
high or low pH or oxygen tensions
chemical inhibitors to bacterial growth prssence of bile acids, lysozymes, fatty acids |
|
|
Secondary defenses
|
humoral substances: complement, lysozyme, opsonins
Phagocytosis: neutrophils and macrophages humoral antibodies: IgG, IgA Cell mediated immune responses |
|
|
other factors affecting host resistance
|
age (young & old very susceptible)
Chronic or debilitating disease short or long term therapy toxc ingestion of alcohol and drugs trauma, stress, foreign materals at site of infection |
|
|
Specimen collection
|
avoid exposures to extreme heat and cold, rapid pressure changes or excessive drying.
deliver to lab within 30 minutes |
|
|
specimen transport
|
transport media:designed to preserve viability of bacteria without allowing multiplication. Anticoagulants
|
|
|
rejection of specimens
|
mismatched label and requisition
late delivery to lab QNS-quantity not sufficient |
|
|
Nutritive media
|
Support growth of wide range of organisms. Nonselective because of growth of most organisms is supported
|
|
|
Differential media
|
nutritive, allow organisms to be distinguished based upon growth characteristics
Blood is nutritive and differential because allows to see hemolysis |
|
|
Selective media
|
Supports growth of one group over another.
|
|
|
MacConkey agar:
|
Crystal violet inhibit growth of Gram positive organisms, so select for Gram negative
|
|
|
Columbia CNA agar:
|
adds colistin and naladixic acid to Columbia agar to inhibit growth of Gram negative organisms and so selects for Gram positive organisms
|
|
|
Ambient conditions
|
21% O, 0.03% CO₂
|
|
|
Anaerobic conditions
|
5-10% H₂, 5-1-% CO₂, 80-90% N₂ and NO O₂
|
|
|
Capnophilic conditions
|
5-10% CO₂, 15% O₂
|
|
|
Microaerophilic
|
5-10% O₂, 8-10% CO₂
|
|
|
Methods available for Lab ID of organisms
Microscopy |
Wet preps and various stains
|
|
|
Methods available for Lab ID of organisms
Cultivation on solid and in liquid media |
Enrichment, supportive, selective, and differential
|
|
|
Methods available for Lab ID of organisms
Conventional biochemical methods |
single enzyme screening
substrate utilization metabolic activity tube vs. commercial ID panel |
|
|
Methods available for Lab ID of organisms
Molecular methods |
DNA probes, PCR-based methods
|
|
|
Methods available for Lab ID of organisms
Chromatography |
GLC, HPLC
|
|
|
Methods available for Lab ID of organisms
Protein Electrophoresis |
Western blotting
|
|
|
Methods available for Lab ID of organisms
Immunochemical electrophoresis |
Agglutination, precipitation, IFA, EIA, ELISA, SPIA
Serologic diagnosis |
|
|
Methods available for Lab ID of organisms
Antimicrobial resistance |
Kirby-Bauer, MIC, E-test, Novabiacin
|
|
|
Genera in family Micrococcaceae
|
Staphylococcus
Micrococcus |
|
|
Epidemiology of Staph infections
|
usually normal flora
Infection caused when enters normally sterile site. Only needs tiny breaks to enter skin or mucosa |
|
|
Transmission of Staph infections
|
transmitted from person to person
also during surgery catheters (UTIs) serious cause of nosocomial infections |
|
|
Pathogenesis of S. aureus
Localized skin infections: |
minor: impetigo
serious: boils, carbuncles spread from exotoxins and enzymes may cause deeper tissue infection, bacteremia, and spread to internal organs |
|
|
Pathogenesis of S. aureus
Toxin mediated diseases Scalded skin syndrome: |
neonates, caused by exfoliatin toxins
extensive sloughing of skin to cause burnlike effect |
|
|
Pathogenesis of S. aureus
Toxin mediated diseases Toxic shock syndrome |
organisms localized, but toxic effects systemic: fever, desquamation, hypotension can lead to shock and death
|
|
|
Pathogenesis of S. aureus
Toxin mediated diseases food poisoning |
Elaboration of exotoxins during growth in contaminated foods
common |
|
|
Pathogenesis of S. aureus
Toxin mediated diseases Bacteremias |
bacteria in blood. Seen mostly in immunocompromised people
|
|
|
Pathogenesis of S. aureus
Toxin mediated diseases community acquired bronchopneumonia |
usually in elderly
associated with viral pneumonia |
|
|
Pathogenesis of S. aureus
Toxin mediated diseases nosocomial infections |
usually occurs as result of obstructive pulmonary disease, intubation, and aspiration
|
|
|
Pathogenesis of S. aureus
Toxin mediated diseases Stapylococcal meningitis |
patients with CNS abnormalities related to trauma, surgery, malignancy, and hydrocephalus
second most common cause of ventriculoperitoneal shunt-associated meningitis |
|
|
Pathogenesis of S. aureus
Virulence factors Capsule formation |
Exopolysccharide to evade immune system and prevent ingestion by neutrophils
promotes adherence to host cells and prosthetic devices |
|
|
Pathogenesis of S. aureus
Virulence factors Hemolysins |
α-hemolysin: lyse neurtophils and RBCs, potent neurotoxin, dermonecrotic (takes out RBCS, WBCs, nerve cells & skin cells)
β-hemolysin: biphasic, lyse RBCs exposed to cold. responsible for Camp test positive with Group B Strep. |
|
|
Pathogenesis of S. aureus
Virulence factors Protein A |
binds Fc portion of immunoglobulins
shed into medium during growth interferes with opsonizations, activates complement, and elicits both immediate and delayed type hypersensitivity reactions. Coagglutination tests specific for this protein |
|
|
Pathogenesis of S. aureus
Virulence factors cell wall constituents |
teichoic acids for adherence to mucosal surfaces
rigidity and structure activate complement, inhibit chemotaxis, stimulate antibody production |
|
|
Pathogenesis of S. aureus
Virulence factors Toxins-Leukocidin |
degranulates, swells and lyses neutrophils
|
|
|
Pathogenesis of S. aureus
Virulence factors Toxins-Exfoliatins |
dissolve mucopolysaccharide matrix of skin to cause scalded skin syndrome
|
|
|
Pathogenesis of S. aureus
Virulence factors Toxins-TSS toxins |
potentiates lethal response to minute amounts of gram negative endotoxin
superantigens (bind directly to monocytes and lymphocytes) resulting in release of cytokines causes rapid multisystem involvement |
|
|
Pathogenesis of S. aureus
Virulence factors Enzymes-Catalase |
inactivates toxic hydrogen peroxide and free radicals formed by myeloperoxidase system of phagocytic cells
|
|
|
Pathogenesis of S. aureus
Virulence factors Enzymes-Coagulase |
coats bacteral cells with fibrin, rendering them resistant to opsonization and phagocytosis
|
|
|
Pathogenesis of S. aureus
Virulence factors Enzymes-Hyaluronidase and fibrinolysins |
spread bacteria through host by breakdown of tissues
|
|
|
Pathogenesis of S. aureus
Virulence factors Enzymes-beta-lactamases |
3 different types
render penicillin useless |
|
|
Staphylococcus aureus
|
Gram positive cocci
– sheep blood agar • ß hemolytic • mannitol fermentation (yellow halo) • Golden pigmented (aureus) • coagulase-positive • catalase-positive Deoxyribonuclease (DNase)-positive thermostabile endonuclease-positive |
|
|
Coagulase negative staphylococci
|
S. epidermidis is the most commonly encountered
Also includes S. haemolyticus, and S. saprophyticus |
|
|
Coagulase negative staphylococci
Nosocomial infections |
related to medical procedure and organisms ability to colonize
Their ability to produce a slime layer and attach to medical devices and their ability to acquire antibiotic resistance enhance the likelihood of infection S. epidermidis, S. haemolyticus |
|
|
Coagulase negative staphylococci
Urinary tract infections |
UTI’s caused by S. saprophyticus most commonly associated with young, sexually active females
2nd only after E. coli Primary virulence factor allows for adherence to epithelial cells of the urinary tract, but not to skin or the mucosal surfaces Also produces urease to improve tissue invasion |
|
|
Coagulase negative staphylococci
Pathogenesis |
Infections of indwelling devices
Due to production of extracellular slime substance Bacteremia in compromised hosts Native and prosthetic valve endocarditis Postsurgical or trauma-associated wound infections Most frequently found as contaminants in clinical specimens |
|
|
Gram Positive Cocci
Media selection |
Mannitol Salt agar isolate staphylococci from normal flora Has a high salt concentration of 10%, the sugar mannitol, and phenol red as a pH indicator
grow in the presence of salt and ferment mannitol, colonies surrounded by a yellow halo Yellow halo is characteristic of S. aureus, but other staphylococci, especially S. saprophyticus, can look the same on MSA |
|
|
Catalase test
|
Catalase test
Differentiates the Micrococcaceae from the Streptococcaceae Detects the presence of cytochrome oxidase enzymes. Bubbling indicates the conversion of the hydrogen peroxide to water and oxygen gas. |
|
|
Glucose fermentation test
|
Detects acid production from the utilization of glucose under anaerobic conditions
Species of Staphylococcus are positive while other species such as Micrococcus are negative |
|
|
Lysostaphin susceptibility
|
An endopeptidase that cleaves the glycine-rich pentapeptide cross-bridges in the staphylococcal cell wall peptidoglycan Renders the cells susceptible to osmotic lysis
Micrococcus is negative, Staphylococcus is positive |
|
|
Furazolidone test
|
Antibiotic sensitivity test
Staphylococci are inhibited by furazolidone and show zones of inhibition of 15 mm or more, while Micrococci are resistant and may show zones of 6 to 9 mm |
|
|
Modified oxidase test (microdase)
|
Filter paper disks impregnated with tetramethyl-p-phenylenediamine dihydrochloride (oxidase reagent) in dimethyl sulfoxide (DMSO) are used
Most strains of Staphylococci (with few exceptions) are oxidase negative while Micrococci and related species are oxidase positive |
|
|
Bacitracin susceptibility
|
Antibiotic susceptibility
Staphylococci are resistant and grow to the edge of the disk, while micrococci are susceptible with zones of 10 mm or larger |
|
|
Coagulase Test
|
Enzyme binds plasma fibrinogen and causes plasma to clot, two types of coagulase, either bound or free
|
|
|
Desferroxamine susceptibility
|
S. epidermidis and S. hominus are susceptible while all other strains are resistant
|
|
|
Novobiocin susceptibility
|
Novobiocin resistant species other than S. saprophyticus are rarely encountered in human specimens
Resistance to this antibiotic is considered a presumptive diagnosis for S. saprophyticus |
|
|
TMPA agar (trehalose-mannitol-phosphatase)
|
Acid production is indicated by a color change from purple to yellow and phosphatase activity is detected by spotting a colony from the medium onto filter paper moistened with 1N ammonium hydroxide
Phosphatase positive colonies produce a pink color. |
|
|
organisms in the family Streptococcaceae that most commonly cause human infections
|
S. pyogenes
S. agalactiae S. pneumoniae Viridans streptococci Enterococci (usually E. faecalis or E. faecium) |
|
|
Catalase negative Gram Positive Cocci
General Characteristics |
facultative anaerobes capnophilic
homofermentative (produce lactic acid) Oxidase negative gram positive cocci that grow in chains some classified by Lancefield groupings |
|
|
Catalase negative Gram Positive Cocci
Epidemiology |
normal flora
Opportunistic pathogens S. pneumoniae-normal upper respiratory flora, leading cause of bacterial pneumonia and meningitis S. pyogenes-rarely considered normal flora |
|
|
Catalase negative Gram Positive Cocci
Epidemiology-Transmission |
Spread person to person by various means and establish colonization
Infections when organism is in sterile sites Access gained during trauma to skin or mucosal surfaces or aspiration into the lungs from the upper respiratory tract--Seen with S. pneumoniae |
|
|
Catalase Negative Gram Positive Cocci
Virulence factors |
M proteins
Opacity factor Streptolysin O Streptolysin S Extracellular toxins Type specific cell surface antigens |
|
|
M proteins
|
major virulence factor of the group A streptococci, Difficult to destroy, Causes resistance to phagocytosis and intracellular killing by neutrophils
|
|
|
Opacity factor
|
Another M protein-associated cell surface antigen of Group A Strep that is a probable virulence factorOnly associated with certain M types (about 29 of the 80)
|
|
|
Streptolysin O
|
Responsible for the β-hemolysis of the Group A Strep under anaerobic conditions (very sensitive to oxygen)
Also produced by some group C and G strep ASO titers measure antibodies against this protein and are useful to diagnose recent pharyngeal Strep infections (after recovery) |
|
|
Streptolysin S
|
Oxygen-stable and actively participates in both aerobic and anaerobic hemolysis by the Group A Strep, probably responsible for destroying the WBC's that ingest the Group A Strep
|
|
|
Extracellular toxins
|
Streptococcal pyrogenic exotoxins
Responsible for the rash of scarlet fever Also likely to be responsible for toxic shock-like syndrome |
|
|
Catalase negative Gram Positive Cocci
Enzymes |
DNAse
Hyaluronidase breaks down connective tissue and allows spreading) Streptokinase hydrolyzes fibrin clots and allows for spreading) |
|
|
S. pneumoniae
virulence factors |
adhesins, an α-hemolysin, pneumolysin, autolysin and pneumococcal surface protein
resistance=polysaccharide capsule (84 types, 23 cause pneumococcal bacteremia and meningitis) vaccine is against those 23 |
|
|
Group B Strep
|
Surface antigens prevent phagocytosis
Increase virulence and survival of the organisms |
|
|
Beta-hemolytic Streptococci Group A (S. pyogenes)
|
person to person-respiratory
streptococcal pharyngitis skin infections-impetigo |
|
|
Beta-hemolytic Streptococci Group A (S. pyogenes)
Suppurative complications |
Peritonsillar abscess
Retropharyngeal abscess Cervical adenitis Otitis media Sinusitis Mastoiditis Bacteremia |
|
|
Beta-hemolytic Streptococci Group A (S. pyogenes)
non-suppurative complications |
Acute rheumatic fever
Glomerulonephritis Toxic shock like syndrome |
|
|
ARF (acute rheumatic fever)
Secondary infection after pharyngitis |
Usually presents with a migratory arthritis, characteristic heart murmurs, cardiac enlargement, CHF or rarely, intractable cardiac arrest and death
|
|
|
ARF (acute rheumatic fever)
Lab Findings |
Lab findings
Increased ESR, increased CRP, previous Strep infection, increased or rising Strep antibody titers (ASO, anti-DNase B, anti-hyaluronidase |
|
|
Glomerulonephritis
Secondary infection after pharyngeal or skin infection |
Presents as glomerular inflammation with glomerular lesions, hypertension, hematuria and proteinuria
Symptoms include malaise, weakness, anorexia, headache, edema and circulatory congestion (hypertension and encephalopathy) |
|
|
Glomerulonephritis
Lab findings |
Anemia, increased ESR, decreased C3 and total complement, hematuria and proteinuria
UA reveals RBC’s, WBC’s and casts ASO is unreliable so anti-DNase B or anti-hyaluronidase should be performed |
|
|
TSLS (Toxic Shock-like Syndrome)
Associated with Exotoxin A produced during scarlet fever |
Promote rapid systemic invasion
Precipitate the multi-organ system involvement severe with high mortality rate |
|
|
Beta-hemolytic Streptococci Group B (S. agalactiae)
Major cause of disease in neonatal and perinatal periods |
Newborn colonized either in utero or during delivery (sometimes nosocomial exposure)
Onset: first 5 days, but most within the first 12 to 24 hours Symptoms include bacteremia, pneumonia, meningitis, septic shock and neutropenia |
|
|
Beta-hemolytic Streptococci Group C
|
Produce hemolysins similar to those of the Group A Strep
S. dysgalactiae also carries the group C antigen, but is alpha or non-hemolytic Most patients infected with these organisms have underlying diseases |
|
|
Beta-hemolytic Streptococci
Group D (S. bovis and S. equinus) |
Usually alpha or nonhemolytic on sheep blood agar, but beta hemolytic on rabbit blood agar
Usually infects patients with underlying diseases or malignancies |
|
|
Beta-hemolytic Streptococci
Group F |
May be beta, alpha or non-hemolytic
Can cause severe suppurative infections, but again, most patients infected with these organisms have significant underlying disease |
|
|
Beta-hemolytic Streptococci
Group G |
Normal human gastrointestinal, vaginal, oropharyngeal, and skin flora
Can cause severe infection of bone and joint prostheses Also can cause pharyngitis, otitis media, cellulitis, etc |
|
|
Alpha-hemolytic Streptococci
S. pneumoniae Major cause of community acquired bacterial pneumonia |
Serious infections: infants and children under 2, late middle-aged and elderly adults
|
|
|
Alpha-hemolytic Streptococci
S. pneumoniae Principle virulence factor |
polysaccharide capsule
Antimicrobial resistance is becoming a serious concern especially to penicillin and related drugs |
|
|
Viridans streptococci
alpha and nonhemolytic Strep, most of which are part of the normal upper respiratory tract and urogenital tract flora |
subacute bacterial endocarditis (valvular disease, or prosthetic valves) Circulating immune complexes: paravalvular abscesses and glomerulonephritis, dental caries
Resistance to antibiotics makes these organisms difficult to treat |
|
|
Enterococci
Normal flora: GI and biliary tracts, the vagina and urethra of males |
UTI’s, bacteremia, endocarditis, intra-abdominal and pelvic infections, wound and soft tissue infections, neonatal sepsis and rarely, meningitis
antibiotic resistance to penicillins and cephalosporins, and even to vancomycin |
|
|
Enterococci
Virulence factors |
cytolysin that acts as a hemolysin against human, rabbit, equine and bovine RBC’s, but not sheep RBC’s, aggregation substance, pheromones(nymphobacteria), bacteriocidin, gelatinase and/or hyaluronidase
|
|
|
Enterococci
Lab Findings |
10°C to 45C, can grow in the presence of 6.5% NaCl, grow at a pH of 9.6, are bile esculin positive and PYR positive
|
|
|
Catalase Negative GPC
Identification Process |
Gram positive cocci in pairs (pneumococci) and chains (most others)
Groups ABCFG-beta hemolytic enterococci, group D, occasional group B-alpha or nonhemolytic All are catalase negative |
|
|
Catalase Negative GPC
Bacitracin sensitivity in conjunction with SXT |
presumptive identification of Group A Strep Any zone of inhibition is considered positive--some Group CG and B Strep are also susceptible, so perform with the SXT susceptibility test because Groups C and G are usually susceptible to SXT and Groups A and B are resistant. Always report as “presumptive” Group A Strep
|
|
|
Catalase Negative GPC
Sulfamethoxazole-trimethoprim sensitivity (SXT) |
Group A and B are resistant, Groups CF and G are susceptible
Any zone of inhibition is considered positive: (A/SXT) S/R = presumptive Group A Strep R/R = Presumptive Group B Strep Var/S = Non Group A or B |
|
|
Optochin sensitivity
|
Ethyl hydrocupreine hydrochloride used to differentiate S. pneumoniae from other Viridans Strep
14 mm or more indicates susceptibility=pneumococci |
|
|
CAMP test
|
Named for Christie, Atkins and Munch-Petersen
Presumptive identification of Group B Strep use with S. aureus |
|
|
Sodium hippurate hydrolysis
|
Group B strep can hydrolyze hippurate to glycine and benzoic acid
Ninhydrin can also be added to detect glycine Under these circumstances a deep blue color is positive |
|
|
Bile esculin test
|
presumptive ID of Group D Strep and Enterococci
positive can grow in the presence of 40% bile and hydrolyze esculin production of esculetin (from esculin hydrolysis) turns the agar black |
|
|
Growth in 6.5% NaCl
|
separate the Enterococci from the Group D Strep
Species of Enterococci are salt tolerant, while the Group D Strep are not |
|
|
Pyrrolidonyl arylamidase test (PYR)
|
presumptive test for Group A strep and Group D Enterococcal species
replaces bacitracin for Group A and salt tolerance for Enterococci |
|
|
Leucine aminopeptidase test
|
Production of LAP along with PYR can help identify Strep, Enterococci and some of the Strep-like organisms
All Strep and Enterococci are positive, separating them from the other Strep-like organisms |
|
|
Spore-forming, aerobic or facultatively anaerobic rods
|
Bacillus sp
|
|
|
Morphologically regular, non-spore-forming bacilli
|
Erysipelothrix sp
Gardnerella sp Lactobacillus sp Listeria sp |
|
|
Irregular or coryneform, non-spore-forming bacilli
|
Dermabacter sp
Corynebacterium sp. Microbacterium sp |
|
|
Bacillus species
General |
Usually grow well on blood agar, producing large spreading, gray white colonies with irregular margins
many are beta-hemolytic most are catalase positive sporulation is not inhibited by aerobic incubation helps distinguish from Clostridium, an anaerobe GPB spore-former Ubiquitous, inhabiting soil, water and dust Thermophilic members can grow at extreme temperatures (58-75C) Psychrophilic members can live in extremes of acidity and alkalinity (pH 2-10) |
|
|
Bacillus species
Disease Processes - Anthrax |
Very rare in the US, but is seen in some other countries.
It has 3 cycles: multiplication of spores in the soil, animal infection and human infection Anthrax spores can remain infectious for decades skin infections inhalation anthrax-almost always fatal Penicillin, ciproflaxacin, tetracycline,and a vaccine |
|
|
B. anthracis
exotoxin |
Edema factor (EF): the extracellular form of adenylate cyclase
Protective Antigen (PA): Promotes entry of EF into phagocytes Lethal Factor (LF): Causes pulmonary edema and death in rats |
|
|
B. cereus
food poisoning |
Toxin mediated disease, not an infection
2 toxins: Emetic toxin that causes vomiting Enterotoxin that causes diarrhea |
|
|
Anthrax identification
|
Large Gram positive bacilli with square or concave ends
non-hemolytic on SBA motility negative API strips sensitive to penicillins and cephalosporins |
|
|
B. cereus identification
|
SBA-usually beta hemolytic
API strips Motile resistant to penicillins and cephalosporins |
|
|
Regular, Non-spore Forming Rods – Listeria Species
General |
Gram positive, motile rod
endotoxin neonates-under 3 months elderly stinky mexican cheese, ice cream fetal death facultative intracellular pathogens (live in monocytes-macrophages) cold enrichment (transport) |
|
|
Regular, Non-spore Forming Rods – Listeria Species
Identification |
Non-spore-forming, short, Gram positive rod
intracellularly or extracellularly, and sometimes as pairs blood agar or CNA colonies: small, translucent VERY narrow zone of beta-hemolysis Catalase positive tumbling motility and umbrella CAMP positive sodium hippurate positive grows at 4°C ferments glucose, trehalose salicin, esculin positive H2S negative |
|
|
Regular, Non-spore Forming Rods--Erysipelothrix
E. rhusiopathiae |
Short, slim Gram positive rod
Erysipeloid, a skin disease blood agar nonmotile catalase negative alpha- or non-hemolytic Produces H2S in TSI or KIA resistant to vancomycin |
|
|
Regular, Non-spore Forming Rods-- Lactobacillus
|
Non-spore-forming Gram positive rods,chains
homofermentative-lactic acid from glucose fermentation resistant to vancomycin nonmotile blood or chocolate agar growth on tomato juice agar Non-hemolytic catalase negative H2S in TSI--negative esculin-negative |
|
|
Irregular Non-spore Forming Rods
|
Many V and L shapes are present on Gram stains
“Chinese letter" forms or "diphtheroid" appearance |
|
|
Irregular Non-spore Forming Rods - Corynebacterium
|
Gram positive
non-branching non acid-fast all but one are non-motile catalase positive ferment glucose and other sugars aerobes or facultative anaerobes |
|
|
C. diphtheriae
|
acute, contagious, febrile illness
exotoxin-necrosis of heart pseudomembrane-oropharynx Potassium tellurite-isolate from normal flora grayish-black after 24-48 hours Tinsdale medium and cystine-tellurite (CT) blood agar-differentiate C. diphtheriae from other corynebacteria Erythromycin and penicillin |
|
|
Gardnerella vaginalis
|
Gram variable (Gram negative to weakly Gram positive)
bacterial vaginosis, asymptomatic in many women Clue cells (epi’s colonized with surface bacteria) offer presumptive diagnosis Addition of 10% KOH releases strong fishy odor and aids in presumptive diagnosis sexually transmitted organism |
|
|
Gram Negative Cocci
General |
nonmotile
non-spore-forming grow best at 35-37°C Capnophilic moist environments produce acid from carbohydrates Oxidase and catalase positive |
|
|
Gram Negative Cocci
Virulence Factors |
lipooligosaccharides--no O surface antigen..allows for antigen variablity to fool immune system
|
|
|
Gram Negative Cocci
Virulence Factors Pili N. gonorrhoeae N. meningitidis |
Long hairlike proteins
mediate attachment to host cells and probably to each other for the purpose of exchanging genetic material between organisms prevent phagocytosis by neutrophils |
|
|
Gram Negative Cocci
Virulence Factors Outer membrane proteins (Omp)N. gonorrhoeae |
Protein I-controls in and out of the cell
Opacity proteins (Opa)-mucosal adherence Protein III--prevent binding of antibodies |
|
|
Gram Negative Cocci
Virulence Factors N. meningitidis |
Polysaccharide capsules-resistant to phagocytosis
looks just like human neuraminic acid |
|
|
Gram Negative Cocci
Virulence Factors N. gonorrhoeae N. meningitidis |
Proteases
Nutritional requirements Beta-lactamases |
|
|
N. gonorrhoeae
|
Sexually transmitted
Acute urethritis-males Endocervical infection-females Ocular infections-primarily neonates |
|
|
Disseminated gonococcal infection (DGI
|
bloodstream infection
Usually characterized by fever, hemorrhagic skin lesions, and various forms of arthritis |
|
|
N. meningitidis
General |
Humans are the only natural host
Spread by respiratory droplets young adults living in close quarters asymptomatically in the oropharynx or nasopharynx Second leading cause of community acquired meningitis in the US confusion, headache, fever and nuccal rigidity, but seen in only half of the patients 30% of cases are fatal 10% of survivors-sensorineural deafness |
|
|
N. meningitidis
Petechiae |
Small hemorrhagic skin lesions indicitave of meningococcemia
development of coagulopathies because of infection |
|
|
N. meningitidis
Meningococcemia |
Can also occur without meningitis, but is usually not fatal
|
|
|
N. meningitidis
Conjunctivitis |
Secondary complication to meningitis
Primary conjunctivitis has also been reported Can lead to corneal ulcers, keratitis, subconjunctival hemorrhage and iritis |
|
|
N. meningitidis
Purpura fulminans |
Extensive areas of tissue necrosis secondary to coagulopathy
Shock, low WBC count, rash and altered mental status are associated with a poor outcome DIC may cause death |
|
|
N. lactamica
|
Very rarely causes meningitis, but has been associated with recurrent otitis media
May be the source of antimicrobial resistance genes among the meningococci |
|
|
Moraxella catarrhalis
|
Seen at higher rates in children with asthma
otitis media and acute sinusitis of children bronchitis and pneumonia of older adults |
|
|
Neisseria gonorrhoeae
Specimen collection |
Dacron or rayon swabs
Nutritive transport systems have the capability to produce CO2 rich environments JEMBEC plates Gono-Pak |
|
|
N. meningitidis
Transport |
No special handling is required except for the occasional genital specimen and blood specimens
Handle like GC specimens |
|
|
Gram Negative Cocci
Isolation of pathogenic Neisseria |
Thayer-Martin (MTM), Martin-Lewis, New York City, and GC-Lect
Grow best at 35-37C in 3-7% CO2 Oxidase positive Gram neg diplococci |
|
|
Superoxol test
|
30% hydrogen peroxide (not 3%) used
N. gonorrhea produces immediate vigorous bubbling while other species produce delayed bubbling |
|
|
Carbohydrate Utilization
main identification method |
N. Gon=+ for Glucose
N. Men=+ Glu, Mal N. Lact=+, Glu, Mal, Lac N. sicca=+ Glu, Mal, Lac, Suc |
