Micro Lab

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clinically important spore forming bacilli

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bacilli and clostridium

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bacillus

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-aerobic (mostly)
-faculatative
-catalase +
-motile
-large GP rods
-spore forming under aerobic conditions

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Clostridium

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-anaerobic
-catalase -
-motility variable
-GP rods
-spore forming under anaerobic conditions

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most clinically important bacillus

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-B. anthracis (encapsulated and causes herbivore disease)
-B. cereus

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media where bacillus grows

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-SBA, Chocolate agars
- incubated at 37 degrees
-aerobic conditions for 1-2 days

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identification of bacillus

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-may appear as gram negative when gram-stained smears are prepared from broth media like blood culture
-gram positive nature is revealed after a few hours of growth on those media
-singly or in chains (b.cereus)
-squared-off or concave ends (b.cereus)
-oval spores may be seen centrally or subterminally and the cells are not swollen in these areas

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B. cereus

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-large, with a matte or granular texture, butyrous
-b hemolytic
-BA
-gastroenteritis/food poisoning
-tx: aminoglycosides, erythromycin, clindamycin and vancomycin

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B. anthracis

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-smaller, gray-white, flat, rough-surfaced
-non hemolytic
-tenacious consistency (standing peaks like beaten egg whites are formed if touched with a loop)
-irregular margins bc filamentous chains of rods surround the colony
-"medusa head" appearance
-non motile
-food poisoning
-tx: resistant to cephalosporins
-tx: penicillin, quinolones, erythromycin, tetracyclines

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bacillus rarely cause ______, but commonly do in heroin drug abusers.

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endocarditis

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Corynebacteria

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-"diptheroids"
-thinGPB
-nonmotile
-catalase and oxidase-positive
-facultative (mostly) or
-aerobic
-pleomorphic
-non-spore forming
-club shaped
-stain unevenly and show "letter arrangements", "birds in flight formations" or V formation after snapping division of cells
-have mycolic acid, arabinose and galactose in their cell wall

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the most isolated corynebacteria

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-c. amycolatum....
-followed by C. jeikeium, C. pseudodiptheriticum, and C. urealyticum (these last 3 mostly cause disease in IC patients.
-c.diptheriae

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there are 4 biotypes of c.diptheriae

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gravis
mitis
belfanti
intermedius
-they differ in certain biochemical rxns, severity of the disease and colony morphology

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media where corynebacteria grow

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-SBA
-Columbia colistin-nalidixic acid (CNA)
-Loeffler medium
-media having cystine and potassium tellurite like Tinsdale's agar

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identification of corynebacteria

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-gram stain
-methylene blue stain
-catalase +
-urea-- variable
-pyrazinamidase (PYZ)
-isolated on SBA, CNA, Tinsdale medium
-gram positive diptheroid rods with metachromatic granules from colonies recovered on Loeffler...this media stimulates the growth of C. diptheriae and the production of deep blue granules

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although some streptococci, S. aureus and other corynebacteria may be isolated with C. diphtheriae on Tinsdale medium, releasing black colonies, only C. diptheriae group (C.diptheriae, C. ulcerans, C. pseudotuberculosis) produce _____. So colonies isolated on SBA, CNA, and Loeffler must be subcultured to Tinsdale.

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black colonies surrounded by brown halos

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C. diptheriae group releases small to medium, gray to white colonies on SBA while colonies of C. diptheriae gravis and mitis are _______.

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-large
-convex with entire edges
-mostly b hemolytic

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C. amycolatum's colonies are

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-flat
-dry
-whitish-gray on SBA

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C. amycolatum diseases

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-catheter-related infections
-surgical wound infections
-endocarditis
-septicemia

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C. diptheriae (toxigenic strains)...and C.ulcerans diseases

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Diptheria

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C. diptheriae (all strains) diseases

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-septic arthritis
-endocarditis

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C. jeikeium diseases

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-cutaneous/soft tissue infections
-otitis media
-pneumonia
-osteomyelitis
-peritonitis
-nosocomial sepsis
-endocarditis and meningitis mostly in IC patienst w/ malignancies

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C. minutissimum disease

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erythrasma (skin infection)

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C. pseudodiptheriticum disease

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-exudative pharyngitis, bronchitis, pneumonia, lung abscess, conjunctivitis, keratitis and endocarditis (pts with preexisting valve damage

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C. urealyticum

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UTIs like pyelonephritis and alkaline encrusted cystitis (IC hosts w/ bladder injury) and urolithiasis. ocassionally osteomyelitis, pericarditis and endocarditis

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transmission and treatment for corynebacteria

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transmission: direct contact or by sneezing or coughin (diptheria); or after close contact w/ animals or by introduction of intravenous catheters
Antiobiotics: penicilin or erythromycin

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Listeria

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-small, short, regular, catalase-oxidase positive
-fermenter (probably facultative)
-intracellular, non-spore forming GPB w/ rounded ends

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most clinically important Listeria

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L. monocytogenes

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Diseases of Listeria

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-listeriosis or granulomatosis infantiseptica in pregnant women (uterine infection that disseminates and causes stillbirth)
-acute sepsis, subacute meningitis and meningoencephalitis in non-pregnant adults and liver abscess, peritonitis, cholecystitis, osteomyelitis, febrile gastroenteritis, and endocarditis in IC hosts

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transmission and treatment of Listeria

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transmission: animals thru environment and vegetation; human by ingestion of contaminated food; by placenta or from GI tract to blood and meninges
treatment: ampicillin w/ or w/o gentamycin usually. penicillin, erythromycin or TMP-SMZ

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What media do Listeria grow in

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SBA and CA

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Identification of Listeria

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-gram stain
-catalase
-motility
-grow at 35 degrees in air incubator or CO2 during 2 days

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L.monocytogenes produce:

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small, gray-white, narrow b hemolytic colonies on BA and in semisolid agar displays a characteristic "umbrella" of motility near the surface of media having .2-.4% agar, after incubation at 25 degrees C.
-this is called "tumbling"

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Most clinically important Aracanobacterium and characteristics

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A. haemolyticum
-slender, fermenter, irregular rods.
-chinese letter and V forms
-they may show rudimentary branching and may be slightly curved

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Habitat of Arcanobacterium

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human skin and nasopharynx

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diseases and transmission of Arcanobacterium

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acute pharyngitis (10-30yrs mostly), chronic skin ulcers, soft-tissue infections, deep tissue abscesses, pneumonia and sinusitis
-transmission: person's endogenous strain or by abrasion or undetected wound during exposure to animals

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Erysipeloid rhusiopathiae description, habitat, disease and transmission

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-slender, weak fermenter, regular, short rod
-habitat: nature, and animals mainly pig and cattle, fish, birds
-diseases: erysipeloid (local, painful, skin infection), septicemia and endocarditis (particularly left-sided)
transmission: contact w/ tissues of infected animals or animal products...
-thus infection is usually found in veterinarians, farmers and fisherman

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Gardnerella vaginalis description, habitat, diseases, and transmission

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-small, fermenter, gram variable coccobacillus
-habitat: vagina and distal urethra of males
-diseases: bacterial vaginosis, genital infections associated w/ complications of pregnancy, neonatal infections related to those complications (amnionitis, bacteremia, meningitis, and conjunctivitis) and UTIs in males and females
transmission: person's endogenous strain

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Rothia dentocariosa description, habitat, diseases, and transmission

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slow-growing, fermenter, irregular rod with rudimentary branchin
-habitat: oropharynx and gingival flora
-diseases: dental infections (periodontal and abscesses)
transmission: person's endogenous strain

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biochemical characteristics of GPC

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-modified oxidase test NEGATIVE (except S.sciuri group, R. mucilaginosa, micrococci and some related bacteria)
-Catalase NEGATIVE (except staph excluding S.sciuri group and 2 anaerobic ones Alloiococcus and R. mucilaginosa which is variable weak)
-motility negative (except 2 enterococci and Lactococcus like-bacteria called Vagococcus)

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Habitat of GPC

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-skin and mucous membranes of humans and animals (micrococci, S.pyogenes)
-female genital tract (S.agalactiae, S. viridans, other strep)
-female genitourinary tract (S. saprophyticus, S. viridans, enterococci)
-GI tract (mostly S. viridans and enterococci)
-URT (streptococci including few B hemolytic ones, R. mucilaginosa and Gemella)
-others like dairy products (Macrococcus) and food and vegetation (aerococci)

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Media where GPC grow

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BA, CA, TSB, MSA (staphylococci), BHI (brain heart infusion) and thioglycollate

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most isolated GPC?

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staphylococci, streptococci...followed by Enterobacteriaceae

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specimens, diseases transmission of GPC

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they are mostly recovered from: wounds, eye, ear, throat and sputum, urine, CSF, Blood

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GPC may be treated with

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penicillin G, PRP, cephalosporins, vancomycin, linezolid and macrolides

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S. aureus

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-most imp staph
-inhabits anterior nares of 20-40% of adults; the intertriginous skin folds in the perineum, the axillae, vagina and environment
-some of its virulence factors are enzymes (catalase, coagulase) and exotoxins
-responsible for food poisoning, toxic shock syndrome and scalded skin syndrome(SSS) (epidermolytic toxins)
-the only coagulase POSITIVE staph

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S. aureus may cause a variety of infections such as:

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-skin infections (furuncles/boils, folliculitis, impetigo, SSS)
-eye infections (its the most common pathogen for this)
-wound infections (particularly post surgical wounds, serving as a nidus for the development of systemic diseases)
-meningitis (related to local trauma due to surgery or injury
-food poisoning (usually occur after the ingestion of preformed enterotoxins found in food like bakery goods, ice cream and potatoe salad
-Toxic shock syndrome
-bronchopneumonia related w/ viral pneumonia in elderely...and bacteremia that can be related to malignant diseases that can lead to pyoarthritis, endocarditis and osteomyelitis (in vertebral column in 60% of adults)

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what may predispose a person to acquire an infection caused by S. aureus?

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malignancy, skin injuries like BURNS, and surgical incisions, foreign bodies like sutures, prosthetic devices, viral infections and defects in leukocyte chemotaxis

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Describe the coagulase-negative Staphylococci

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had little clinical significance and were considered contaminants. but they are already recognized as human pathogens. the most imp. are S. epidermidis, S. saprophyticus, S. haemolyticus, and S. lugdenensis

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S. epidermidis (describe..virulence factors, etc)

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-the most common coagulase-negative staph
-virulence factors are polysaccharide-adhesin (PS/A) and polysaccharide intercellular-adhesin (PIA)
-most infections caused by this staph are nosocomial (except endocarditis)

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In S. epidermidis, what is the purpose of PS/A and PIA?

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PS/A promotes adherence to plastic surfaces of foreign bodies to form a biofilm and PIA promtes adhesion b/n those cells

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S. epidermidis is the most comon cause of:

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-prosthetic valve endocarditis
-indwelling CFS, CFS shunt and intrathecal pump infections.
-postsurgical endophthalmitis (culture of vitreous fluid)
-catheter related -infections, particularly continous ambulatory peritoneal dialysis (CAPD)- associated peritonitis and intravenous catheter infections
-bacteremia in IC patients with malignancy and neutropenia; in premature babies and neonates and in elderly w/ underlying diseases
-catheter related UTIs in elderly w/ urolithiasis, renal transplantation or prior urinary tract surgery or implantation

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describe S. saprophyticus (include virulence factors)

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-highly implicated in acute UTIs, particulary in young sexually active WOMEN
-virulence factor is a surface associated protein, which adheres to uroepithelial cells
-it is the 2ndary most common cause of UNCOMPLICATED CYSTITIS after E. Coli in younng females
-also causes pyelonephritis, urethritis in men and women, catheter associated-UTIs, prostatitis in elderely and RARELY SEPTICEMIA

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S. haemolyticus and S. lugdunensis (describe)

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-coagulase negative Staph
-opportunistic in IC pts and usuallly cause wound infections, UTIs, osteromyelitis and catheter-related sepsis

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describe streptococci

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-grow in chains of diplococci
-ferment glucose just by making lactic acid (homofermentative)
-most species grow better in an environment w/ increased CO2

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the beta hemolytic group of streptococci

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-s.pyogens
-s. agalactiae
-they inhabit the female genital tract, GI tract, nasopharynx and skin

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S. pyogenes (group A) virulence factors, reservoir, transmission?

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-humans are its natural reservoir
-transmitted by resp. route
-virulence factors: capsule of hyaluronic acid, enzymes like streptolysin O (SLO) and S (SLS) which are responsible for b hemolysis on BA, M protein (MAJOR VIRULENCE FACTOR) and streptococcal pyroge-exotoxins (SPEs), which are responsible for the rash of scarlet fever

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S.pyogenes mostly cause the diseases:

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-acute pharyngitis
-complications of pharyngitis like peritonsillar abscess, otitis media

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S. agalactiae (group B) virulence, habitat, etc...

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-few strains are non-hemolytic
-inhabits female genital tract and rectum
-vaginal colinization occurs in 10-35% of pregnant women; so its presence at the time of birth can lead to neonatal infections
-some of its virulence factors are: hyaluronic acid and capsule (9 types)
-type III capsule accounts for 60% of neonatal sepsis and over 80% of meningitis in infants

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other b hemolytic streptococci besides S.pyogenes and S. agalactacia (the most implicated in human infections)....habitat and diseases caused

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S. dysgalactiae subspecies equisimilis (group C and G).
-inhabits skin, pharynx, vagina, GI tract
-mostly causes exudative pharyngitis, tonsillitis, puerperal sepsis, sepsis in neutropenic hosts, cellulitis, necrotizing fasciitis, pneumonia, meningitis, empyema, and bacteremia

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Name the alpha hemolytic streptococci

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-S.pneumonia
-S.viridans

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S.pneumonia characteristics, virulence, diseases?

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-lancet-shaped diplococcus that may inhabit the URT
-main virulence factor is a polysaccharide capsule, which avoids phagocytosis and opsonization by neutrophils
-most serious pneumococcal's infections occur in infants younger than 3 yrs old and adults >65.
-Pneumococcus is the major cause of community-acquired bacterial lobar pneumonia
-leading cause of bacterial meningitis in adults

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S.viridans characteristic, diseases?

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alpha and non hemolytic species, most of which constitute part of the normal URT and urogenital tract (UGT) flora
-they mostly cause sub-acute bacterial endocarditis (SBE), and mostly w/ persons w/ preexisting native-valve disease

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enterococci habitat, characteristics?

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-inhabit GI and biliary tracts, and in lower numbers the vagina and male urethra
-they are important agents of human disease largely because of their RESISTANCE TO ANTIBIOTICS
-alpha or non hemolytic on BA usually
-the 2nd most common cause of nosocomial UTIs
-3rd most common cause of nosocomial bacteremias
-E. faecalis is the most isolated (80-90% of cases)

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Other gram positive cocci besides staph and strep

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-Aerococcus and Gemella
-Abiotrophia, Alloiococcus otitidis, Globicatella, and R. mucilaginosa (large and encapsulated)

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once a bacterium has been identified as gram +, catalase positive, what test must be done to confirm if S. aureus?

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Coagulase test +
(although 2 other staph are positive...S.scheleiferi subsp schleiferi and subsp coagulans...they don't produce acid from maltose and rarely cause human infections

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If coagulase test shows negative or equivocal results after the bacterium has been identified as GP catalase positive cocci, what test must be done to check for S.aureus? if still comes out negative, what test should be done to seperate S. epidermidis from S. saprophyticus? And ornithine decarboxylase test confirms what bacteria and why?

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1. DNase
2. novobiocin susceptibility test (epidermidis and all other staph is S, saprophyticus is R)
3. S. lugdunensis, bc it is the only one that is consistently positive

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colonies of staph (all species) are?

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-medium to large, smooth and butyrous (creamy)
-s.aureus ones are usually large, white, or yellow and sometimes b hemolytic on BA.
-On MSA they are surrounded by a yellow halo, due to the fermentation of mannitol
-s.epidermidis produce small to medium, generally gray-white, STICKY and non-hemolytic colonies on BA....no yellow halo on MSA
-S. saprophyticus releases smooth, large, butyrous and generally white (orange or yellow sometimes) colonies on BA...on MSA they MAY be surrounded by the yellow halo

Front 68

If small to medium, smooth, non-pigmented (yellow, orange or pink-red) colonies appear on BA what may be suspected?

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Micrococcus

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how are micrococcus seperated from staph?

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bc they are S to bacitracin and R to furazolidone and staph react the opposite of that
-also on gram stained smears, micrococci appear slightly larger than staph and mostly arranged in pairs, tetrads or irregular clusters

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steps in identifying staphy:

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1. gram positive
2. catalase +
3. coagulas (positive=s.aureus)
4. DNAse (+ for S.aureus)
5. Novobiocin (S.sapro..is the only one R...epidermis is S and so are the others)

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all enterococci have what in common?

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-all hydrolyze PYR
-all are LAP + (leucine aminopeptidas)
-grow at 10 degrees C and in 6.5% NaCl

Front 72

what is the test used for the preliminary identification of enterococci and group D streptocci. entorococci are commonly recovered from where?

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1. Bile esculin
2. blood and urine

Front 73

describe swarming motility and what bacteria exhibits it

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a wavelike spreading of the bacterium across the entire surface of a non-inhibitory agar
-proteus