Bacteriology exam 1- 1

agents of the throat

-Viruses-Streptococcus pyogenes (Group A Streptococcus)-Other bacterial causes, though not as common as group A-Candida albicans

specimen collection of the throat

-Posterior pharynx-Avoid normal oropharyngeal flora-Collect two swabsoInoculate blood agar plateoRapid testing for GAS antigen

agents of the nasopharyngeal

-Bordetella pertussis, Influenza virus, Coronavirus

carrier state of the nasopharngeal

-Staphylococcus aureus-Neisseria meningitidis

specimen collection of the nasopharyngeal

-Flexible thin wire swab guided into nares to posterior pharynx

specimen of oral cavity

-Gingivitis and dental caries

specimen of middle ear

-Otitis media-Predictable pathogens, rarely cultured-S. pneumoniae and H. influenzae most common

specimen of sinuses

-Direct sinus aspirations, washes-Predictable pathogens, rarely cultured

lower respiratory tract specimens

§Bronchitis or pneumonia

agents of lower respiratory tract

-Viruses-Streptococcus pneumoniae, Klebsiella pneumonia, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, anaerobes-Mycoplasma pneumoniae (walking pneumonia)

specimen collection of lower respiratory tract

-Expectorated sputum, endotracheal specimens, translaryngeal aspirates, bronchoalveolar lavage

What is used to evaluate sputum samples?


What plates are used for sputum?


What agents are in the gastrointestinal tract?

-Rotavirus, Norovirus-Parasites-BacteriaoVerotoxic E. coli, Salmonella, Shigella, Campylobacter, Vibrio, Yersinia enterocolitica

What samples are taken from the gastrointestinal tract?

stool and rectal swab

How is stool sample processed?

-Usually contains many species of facultative and anaerobic normal flora-Wide mouth container with tight fitting lid-Commercial transport media available to preserve specimen

Is a gram stain for white cells used in stool samples?


How are stool samples plated?

-Blood, MAC, Xylose-lysine-desoxycholate (XLD), selenite (enrichment) broth-No anaerobic media

What agents are in urine?

-E. coli and other Enterobacteriaceae (Proteus, Enterobacter, Klebsiella); Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus aureus, S. saprophyticus

How are urine samples collected?

-Transport tube with preservative (boric acid-glycerol) is available if delivery delayed-Clean catch midstream preferred

What plates are used for urine samples?

to blood and MAC

What agents are in blood?

-Staphylococcus aureus, S. epidermidis, Enterococcus, E.coli and other Enterobacteriaceae-Candida albicans and other species

How is the skin protected when collecting blood?

-First scrub with 70% alcohol for at least 60 seconds-Second apply 2% chlorhexidine (preferred) or 2% tincture of iodine in concentric circles-Culture bottle tops cleaned with alcohol before inoculation with blood specimen

How often is blood collected?

§Collect two sites at least one hour apart because number of bacteria per mL may be low-Collect at least 20 mL of blood per set-Usually no more than 3 sets per 24 hours

What do the blood collection bottles contain?

-polyanethol sulfonate (SPS) anticoagulant

What do the set of blood containers consist of??

§A set of bottles consists of one aerobic and one anaerobic bottle, though at least one aerobic bottle is necessary

What agents are in CSF?

-Neisseria meningitidis, Haemophilus influenzae, Streptococcus agalactiae-Viruses-Fungi

What are the collection of CSF?

-Needle aspirate from third or fourth lumbar vertebra-Three to four tubesSTAT

What plate should CSF go on?

blood, CHOC andinoculate a thioglycolate broth

What agents are in the genital tract?

-Neisseria gonorrhoeae, Treponema pallidum (syphilis) Herpes Simplex Virus type 2, Chlamydia trachomatis, Trichomonas vaginalis

What is the collection of genital tract for females?

oLower genital tract: swaboUpper genital tract: aspiration or biopsy

What is the collection method of genital tract for males?

oLower genital tract: swaboUpper genital tract: aspiration or biopsy

What plate is gonorrhea plated on>

oMartin Lewis or Modified Thayer Martin media

Agents in wounds

-Staphylococcus aureus, Enterococcus, gram-negative bacilli, anaerobes, fungi

What is the collection method of wounds?

-Need exact anatomic site where specimen was taken-Aspirates, purulent drainage, tissue-Recommend needle aspirates over swabs

What do wounds get plates on?

with blood, MAC, CHOC, and thio broth

What is the goal of specim trasport?

-Two-hour limit to specimen receipt-Transport media such as Stuart's, Amies, and JEMBEC may be used to maintain viable cells

What can cause a specimen to be rejected?

-improperly labeled-in unsuitable container-accompanied by improper request-of insufficient quantity-received more than two hours after collection

What can neutrophils and epitheliel cells mean?

-Neutrophils ~ infection-Epithelial cells ~ contamination

What is brightfield microscope?

all methods

What is phase contrast microscopy?

unstained slides, motlity

What does saline mount identify?

-Observe bacterial motility-Observe Trichomonas vaginalis in urine

What does iodine mount indentify?

ova and parasites in stool

What does KOH identify?

skin and nails

What does the India ink stain?

Cryptococcus neoformans

What is the simple stain of a mount?

methylene blue

Blood agar plates

-Trypticase soy agar with 5% defibrinated red blood cells-SourceoPrefer sheep blood agar (SBA)oHorse or rabbit blood give different results-Grows most significant pathogens


-Observe at surface and also "stab" agar to observe subsurface hemolysis.-AlphaoIncomplete or greening or browning-BetaoComplete clearing-Non hemolyticoNo change to red blood cells

Chocolate agar

-Red cells are hemolyzed by enzyme or heat to release NAD and hematin-Enriched with IsoVitaleX and other nutrients-Isolates fastidious bacteria, such as Haemophilus-Will grow nearly all bacteria

§Thioglycollate broth

-Growth and differentiation of aerobes and anaerobes

§MacConkey Agar

-Isolates gram-negative bacteria-Differentiates fermentersoLactose fermenters§PinkoNonlactose fermenters§Clear

§Eosin methylene blue plate

-Isolates gram-negative bacteria-Differentiates fermenterssoStrong lactose fermenters such as E. coli§Green metallic sheeno Lactose fermenters§PurpleoNonlactose fermenters§Clear

§Hektoen Enteric (HE) and xylose lysine deoxycholate (XLD)

-Inhibit normal microbiota of colon-Enhance isolation of stool pathogens-Differentiate based on ability to ferment carbohydrates, production of H2S

§Colistin nalidixic acid (CNA) and phenyl ethyl alcohol (PEA) agars

-Blood agar with antibiotics added-Selects for gram-positive bacteria and inhibits gram-negative bacteria

§Modified Thayer Martin (MTM) and Martin Lewis

-Chocolate agar base with antibiotics added-Selects for Neisseria gonorrhoeae and inhibits gram-positive bacteria, other gram-negative bacteria, and yeast

What is the Order of Inoculation?

oSpecimens that require immediate attention include cerebrospinal fluid, body fluids, and blood-Media OrderoLeast selective media inoculated first - blood or chocolate firstoSolid media inoculated before broth

How is a urine count conducted?q

blood agar plate10uLincubate 24 hoursmultiplying by 1000 or 100 to find CFU/mL§Values > 1.0 X 105/mL indicate infection

What is the -Mesophilic temperature needs?

oHuman bacterial pathogens grow best at 35 + 2oCoFungal cultures usually incubated at 25 - 30oC

What should the humidity be?


What are the methods for microorganism identification?

phenotype, immunologic,genotype

When is colony microscopy examined/

18-24 hours after incubation