Simplified version of important Microbiology points that you need in Medical School.
Facultative
Intracellular |
Salmonella, Nesseria, Brucella, Mycobacterium, Listeria,
Francisella, Legionella, Yersinia. [Some Nasty Bugs May
Live FacultativeLY.] |
Obligate
Intracellular |
Rickettsia, Chlamydia. Can’t make own ATP [Stay inside (cells) when it is Really Cold.] |
Bacterial Growth |
Lag Phase Initial
Phase (only 1 lag phase) Detoxifying
medium Turning
on enzymes to utilize medium For
exam, number of cells at the beginning equals number or cells at the end of
lag phase. Log Phase Rapid
exponential growth Generation
time = time it takes one cell to divide into two. This is determined during
log phase. Stationary Phase Nutrients
used up. Toxic
products like acids and alkalies begin to accumulate Number
of new cells equals number of dying cells. |
Special stains |
Congo red : Amyloid; apple-green birefringence in
polarized light (because of ß-pleated sheets) Giemsa’s : Borrelia, Plasmodium, chlamydia,
Calymmatobacterium donovani & trypanosomes. PAS (periodic acid-Schiff) : Stains glycogen,
mucopolysaccharides; used to diagnose Whipple’s disease (malabsorption
syndrome caused by Tropheryma whippelii) Ziehl-Neelsen : Acid-fast bacteria (Nocardia is partially
acid fast!) India Ink : Cryptococcus neoformans. Silver Stain: Fungi, PCP (Pneumocystis carinii pneumonia),
Legionella |
Special culture
requirements |
H. influenzae -
Chocolate agar + factors V (NAD) & X (hematin) N. gonorrhea -
Thayer-Martin Medium B. pertussis -
Bordet-Gengou (potato) agar C. diphtheriae -
Tellurite plate, Loeffler’s medium, blood agar M. tuberculosis
- Lowenstein – Jensen agar Lactose fermenting
enterics - Pink colonies on MacConkey’s
agar (Klebsiella, Enterobacteriaceae & E. coli) Legionella -
Charcoal yeast extract agar buffered with increased iron and cysteine Fungi - Sabouraud’s
agar |
The four sisters
“Ella” worship in the “Cysteine” chapel |
Francisella, Brucella, Legionella, Pasteurella |
Bacterial spores |
Gram + soil bugs ≈ spore formers (Bacillus anthracis,
Clostridium perfringens , Clostridium tetani) Must autoclave to kill spores! |
Zoonotic organisms |
Brucella Bacillus anthracis Listeria monocytogenes Salmonella enteritidis Campylobacter Coxiella burnetii - Q-fever Chlamydia psittaci Francisella tularensis Yersinia pestis |
Enterobacteriaceae |
Toxins CALM: Cholera Anthrax E coLi Pertusis Lactose fermentation 1)
Non Lactose fermenters: a)Non-motile,
non-H2S producers: Shigella, Yersinia b)Motile,
H2S producers: Salmonella, Proteus 2)Lactose
fermenters: E. Coli, Klebsiella |
Staphylococcus |
S. epidermidis ◦Coagulase(-), gram (+) cocci ◦Novobiocinsensitive ◦Infections of catheters/shunts S. saprophyticus ◦Coagulase(-), gram (+) cocci ◦Novobiocinresistant ◦“Honeymoon cystitis” Urinary Tract Infections ◦E. coli, S. saprophyticus, K. pneumoniae, P. vulgaris. S. aureus ◦Coagulase(+), gram (+), catalase(+), ß-hemolytic of blood
agar, cocciin 'grape' clusters. ◦Gastroenteritis: 2-6 h onset, salty foods, custards. ◦Endocarditis: acute ◦Toxic Shock Syndrome: desquamating rash, fever,
hypotension ◦Impetigo: bullous+ honey crusted lesions ◦Pneumonia: nosocomial, typical, acute ◦Osteomyelitis: #1 cause unless HbS mentioned Treatment: ◦Gastroenteritis is self-limiting ◦Nafcillin/oxacillinare DOC ◦For MRSA: vancomycin ◦For VRSA: quinupristin/dalfopristin(Synercid®) |
Group A Streptococcus |
S. pyogenes ◦Catalase(-), ß hemolytic, bacitracinsensitive, gram (+)
cocci ◦Pharyngitis: abrupt onset, tonsillaranscesses ◦Scarlet fever: blanching, sandpaper rash, strawberry
tongue ◦Impetigo: honey-crusted lesions ◦Rheumatic fever: after streptococcal pharyngitis, ↑ ASO
titer ◦Acute glomerulonephritis (AGN): after streptococcal skin
or throat infection, hypertension, edema, smoky urine. Treatment: ◦ß lactamdrugs (macrolidesused in penicillin allergy) |
Group B
streptococcus |
S. agalactiae ◦Group B, ß-hemolytic, Bacitracinresistant, Hydrolyzes
hippurate ◦Gram (+), catalase(-), CAMP test (+) ◦Neonatal meningitis and septicemia: #1 cause, especially
in prolonged labors. Treatment: ◦Ampicillinor penicillin (DOC) ◦Clindamycinor erythromycin for penicillin allergies |
Streptococcus
pneumoniae |
◦Gram (+), catalase(-), αhemolytic, soluble in bile,
Optochinsensitive, + Quellung‟sreaction ◦Pneumonia: typical, most common cause, rusty sputum
(productive cough) & lobar pneumonia ◦Meningitis: many PMNs, ↓glucose, ↑ protein in CSF, most
common adult cause. ◦Otitismedia and sinusitis: most common cause. Typical pneumonia: ◦Bacterial pneumonia such as S. pneumoniaeelicits
neutrophils; arachidonicacid metabolites (acute inflammatory mediators) cause
pain & fever. Pneumococcusproduces lobar pneumonia with productive cough,
grows on blood agar, and usually responds well to penicillin treatment. Treatment: ◦Bacterial pneumonia à macrolides ◦Adult meningitis à ceftriaxoneor
cefotaxime ◦Otitismedia and sinusitis à amoxicillin,
erythromycin (for allergic) |
Viridans
streptococci |
(S. sanguis, S. mutans) ◦Gram (+), catalase(-), αhemolytic, Optochinresistant,
bile insoluble ◦Plaque and dental caries(S. mutans) ◦Subacutebacterial endocarditis:preexisting damage to
heart valves; follows dental work (S. sanguis) Tretment: ◦Penicillin G with aminoglycosidesfor endocarditis |
Enterococcus |
Enterococcus faecalis/faecium ◦Gram (+), catalase(-), variable hemolysis, hydrolyzes
esculin ◦Urinary/biliarytract infections –elderly males after
prostate treatment ◦Subacute bacterial endocarditis–elderly males, follows
GI/GU surgery, preexisting heart valve damage Treatment: ◦Some vancomycin-resistant strains have no reliable
effective treatment. ◦VanA strains have UDP-N-acetylmuramylpentapeptidewith the
terminal D-alanyl-D-alaninereplaced with D-alanyl-D-lactate (functions in
cell wall synthesis but does NOT bind to vancomycin) |
Bacillus |
Bacillus anthracis ◦Gram (+), spore forming aerobic rods ◦Contact with animal hides or postal worker; escharor
life-threatening pneumonia (wool sorter‟s disease) ◦Treatment : ciprofloxacin or doxycycline Bacillus cereus ◦Rapid onset gastroenteritis ◦Fried rice, Chinese restaurants ◦Treatment : self-limiting |
Clostridium |
Clostridium tetani ◦Dirty puncture wound ◦Rigid paralysis ◦Treatment: TIG + metronidazole/penicillin;
spasmolytic(diazepam) Clostridium botulinum ◦Home-canned alkaline vegetables ◦Floppy baby syndrome ◦Reversible flaccid paralysis Clostridium perfringens ◦Contaminated wound ◦Pain, edema, gas, fever, tachycardia ◦Food poisoning : reheated meats, noninflammatorydiarrhea ◦Treatment : Gangrene
à clindamycin, penicillin Food
poisoning Ã
self-limiting Clostridium difficile ◦Hospitalized patient on antibiotics (antibiotics
over-use) ◦Develops colitis, diarrhea ◦Treatment : metronidazole(vancomycin) Mnemonis: TETanus is TETanic paralysis BOTulinumis from bad BOTtles of food and honey PERFringens PERForates a gangrenous leg DIfficilecauses DIiarrhea(Treat with metronidazole) |
Listeria |
Listeriamonocytogenes ◦Gram (+) rods, ß-hemolytic ◦Facultative intracellular ◦Foodborne(deli foods) à unpasteurized
milk ◦Transplacental–granulomatosisinfantiseptica ◦Neonatal septicemia and meningitis(3rdmost common cause) ◦Meningitis in renal transplant or cancer patients(most
common cause) Treatment : ampicillin(+ gentamycinfor IC patients) |
Corynebacterium
diphtheriae |
◦Gram (+), aerobic, non-spore forming rods ◦BULL NECK, myocarditis, nerve palsies ◦Gray pseudomembraneà airway
obstruction ◦Toxin produced by lysogeny(ß-corynephage) ◦Toxin ribosylatesEF-2; heart, nerve damage ◦V-L shapes à tellurite ◦Metachromaticgranules à Loeffler‟s Treatment : ◦Erythromycin and antitoxin Mnemonic: (ABCDEFG) ADP-ribosylation; ß-corynephage;
CorynebacteriumDiphtheria; Elongation Factor-2; metachromatic Granules |
Actinomyces |
Actinomycesisraelii ◦Patient with mycetomaon jawline or spread from IUD ◦Causes oral/facial abscesses with YELLOW sulfur granules
that may drain through sinus tracts in skin (can cause 1 brain abscess) ◦Sulfur granules in pus grow anaerobic, gram (+), non-acid
fast branching rods (resembling fungi) Treatment : ◦Ampicillinor penicillin G and surgical drainage |
Nocardia |
Nocardiaasteoidsand Nocardiabrasiliensis ◦Gram (+) filamentous bacilli, aerobic, PARTIALLY acid
fast ◦Norcardiosis: Cavitarybronchopulmonarydisease,
mycetomas(can cause multiple foci brain abscesses) Treatment : ◦Sulfanomidesor TMP-SMZ Mnemonic: (SNAP) Sulfa for Nocardia; Actinomycesuse Penicillin |
Mycobacterium |
Mycobacterium Tuberculosis ◦High risk patient (Low SES, HIV+, IV drug user) ◦Chronic cough, weight loss ◦Auraminerhodaminestaining, acid fast bacilli in sputum ◦Produce niacin, heat sensitive catalase ◦Positive DTH test (PPD) ◦Facultative intracellular ◦Ghoncomplex: -TB
granulomas(Ghonfocus) + lobar & perihilarlymph node involvement -Reflects
1˚ infection/exposure Mycobacterium leprae(leprosy) ◦Acid fast bacilli in punch biopsy ◦Immigrant patient with sensory loss in extremities ◦+ leprominskin test in Tuberculoidtype (TL) BUT NOT
Lepromatousleprosy (LL) ◦NO CULTURES |
Neisseria |
Neisseria meningitidis ◦Young adults with meningitis ◦Abrupt onset with signs of endotoxintoxicity Oxidase(cytochromeC oxidase) test: ◦flood colony with phenylenediamine; in presence of
oxidase, phenylenediamineturns black. Rapid test. ◦Major oxidase-negative gram –group is Enterobacteriaceae Treatment : ◦Neonates & infants: Ampicillinand cefotaxime ◦Children & adults: cefotaximeor ceftriaxone Neisseria gonorrhoeae ◦Sexually active patient ◦Urethral/vaginal discharge (leukorrhea) ◦Arthritis possible ◦Neonatal ophthalmia ◦Gram –diploccocusin neutrophils Treatment : ceftriaxone |
Pseudomonas |
Pseudomonas aeruginosa ◦Oxidase(+), aerobic rod ◦Blue-greenpigments, fruity odor ◦Burn infections –blue-greenpus, fruity odor ◦Typical pneumonia –CGD or CF ◦UTI –catheterized patients Treatment : ◦Penicillin + aminoglycoside Drug resistance (very common): ◦Intrinsic resistance (missing high affinity porinsome
drugs enter through); ◦Plasmid mediated ß-lactamasesand acetylating enzymes. |
Legionella |
Legionella pneumophila ◦Elderly smoker, heavy drinker, or IC ◦Exposure to aerosols of water (air conditioning) ◦Atypical pneumonia (legionnaires disease), Pontiac fiver ◦Associated with hyponatremia Treatment : ◦Fluoroquinoloneor azithromycinor erythromycin with
rifampinfor IC patients |
Francisella |
Francisellatularensis ◦Patient with ulceroglandulardisease, atypical pneumonia,
or gastrointestinal disease ◦Arcansas/Missouri ◦Exposure to rabbits/ticks Treatment : ◦streptomycin |
Bordetella |
Bordetella Pertussis ◦Unvaccinated child (immigrant family or religious
objections) ◦Cough with inspiratory“whoop” (3 stages): (1-2
wks) catarrhal : CONTAGIOUS (2-4
wks) paroxysmal : organism begin disappearing (>3
wks) convalescence : secondary complications ◦Immunity: DTaPlasts
5 –10 years (IgA) Immunity
to actual pertussisis life long Treatment : ◦Supportive care & Erythromycin (14 days) |
Brucella |
Brucellaspecies ◦Patient with acute septicemia ◦Exposure to animals or unpasteurized dairy ◦California/Texas or travel to Mexico Treatment : ◦Adults : rifampin& doxycycline(6 wks) ◦Children : rifampin& cotrimoxazole |
Campylobacter |
Campylobacter jejuni ◦Patient with inflammatory diarrhea ◦Microaerophillic, oxidase+, grows at 42˚C ◦Ten or more stools/day, maybe frankly bloody ◦Complications à GBS
& reactive arthritis Treatment : ◦Mostly fluid and electrolyte replacement. ◦Erythromycin, fluoroquinolones, penicillin resistant. |
Helicobacter |
Helicobacter pylori ◦Patient with gastritis, ulcers, stomach cancer ◦Microaerophillic, oxidase+, urease+ ◦Reservoir - HUMANS Treatment : ◦Omeprazole+ amoxicillin + clarothromycin ◦Treat for 10 –14 days |
Escherichia |
Escherichia coli ◦Isolation of E. coli from stool is not significant. ◦Sorbito lMacConkey screen ◦Most E. coliferment sorbitol(Most EHEC do not –colorless) ◦Toxins ↑cAMP EPEC
= P (pediatric) ETEC
= T (traveller) EIEC
= I (inflammatory) EHEC
= H (hamburger; Hemolytic colitis and Hemolytic Uremic Syndrome) |
Shigella |
Shigellaspecies ◦patient with acute bloody diarrhea + fever ◦Non-motile, non-H2S producer and non-lactose fermenters ◦Shigellasonnei(most common in U.S) ◦Shigelladysenteriae(most severe disease) –SHIGA TOXIN
(neuro, cyto, entero) |
Klebsiella |
Klebsiella pneumonia ◦Elderly patient with typical pneumonia: currant jelly
sputum ◦UTI (catheterized associated) ◦Septicemia ◦IC or nosocomial ◦Oxidase(-), encapsulated, lactose fermenters ◦Treatment : 3rdgeneration cephalosporin Klebsiella Granulomatis ◦Patient from Caribbean or New Guinea with subcutaneous
genital nodules ◦Encapsulated, inside mononuclear cells ◦Treatment :TMP-SMX; tetracyclinesand erythromycin |
Salmonella |
Salmonella typhi ◦Patient with fever, abdominal pain, rose spots ◦Travel to endemic area ◦Encapsulated, nonlactosefermenter, produces H2S and is
motile. ◦Widaltest + Treatment: Fluoroquinolones or 3rd gen cephalosporins S. enteritidis, S. typhimurium ◦Enterocolitis–inflammatory, follows ingestion of poultry
products or handling pet reptiles. ◦Septicemia –very young or elderly ◦Osteomyelitis–sickle cell disease Treatment: ◦For gastroenteritis : self-limiting ◦For invasive disease : Ampicillin, TMP-SMX,
Fluoroquinolonesor 3rdgen cephalosporins. |
Yersinia |
Yersinia pestis–THE PLAGUE! ◦High fever, buboes (swelling of regional lymph nodes),
conjunctivitis and pneumonia ◦Exposure to small rodents, desert Southwest ◦Bipolar staining (“safety pin”) ◦Treatment : aminoglycosides Yersinia enterolitica ◦Patient with inflammatory diarrhea or pseudoappendicitis ◦Cold climates; Unpasteurized milk, pork ◦Non-lactose fermenters, non-H2S producers ◦Treatment: For IC - fluoroquinoloness or 3rd generation
cephalosporins. |
Proteus |
Proteus mirabilis/Proteus vulgaris ◦Patient with UTI or septicemia ◦Swarming motility on blood agar plate ◦Staghornrenal calculi (struvitestones) ◦Non-lactose fermenting, urease(+) ◦Treatment : fluoroquinolones, TMP-SMX, or 3rdgeneration
cephalosporinsfor uncomplicated cases. NOTE:Weil Felix test: Antigens of OX strains of Proteus
vulgariscross-react with rickettsial organisms. |
Gardnerella |
Gardnerella vaginalis: ◦Female patient with increased thin gray vaginal discharge
and a “fishy” amine odor. ◦Post antibiotic or menses ◦Clue cells ◦Whiff test + ◦Treatment : Metronidazoleor clindamycin |
Vibrio |
Vibrio Cholera: -Patient with non-inflammatory diarrhea -Rice water stool; Dehydration -Travel to endemic area -Curved rods, polar flagella, oxidase + -Treatment: 1.fluid
and electrolyte replacement 2.Doxycyclineor
ciprofloxacin shorten disease and reduce carriage. Vibrio parahaemolyticus -Consumption of undercooked or raw seafood -Watery diarrhea with abd cramps- self limiting Vibrio vulnificus -Swimming in brackish water; shucking oysters or consuming
undercooked or raw seafood -causes gastroenteritis or cellulitis(treat with
tetracycline) |
Rickettsia |
Rickettsiarickettsii ◦Patient with influenza-like symptoms and petechialrash
that begins on ankles and wrists and moves to trunk ◦Rocky mountain spotted fever (RMSF) ◦East coast mountainous areas (North Carolina) ◦Spring/Summer seasons ◦Outdoor exposure ◦Weil-Felix (+) Treatment : ◦doxycycline |
Coxiella |
Coxiellaburnetii ◦Patient with fever, pneumonia, granulomatoushepatitis ◦Q-fever and chronic Q-fever ◦Exposure to domestic animal breeding operation ◦Diagnosed serologically Treatment :Doxycycline& erythromycin |
Chlamydia |
Chlamydia trachomatis ◦Sexually active patient or neonate ◦Adult : urethritis, cervicitis, PID, inclusion
conjunctivitis ◦Neonate : inclusion conjunctivitis/pneumonia ◦Immigrant from Africa/Asia, swollen genital
lymphadenopathy ◦Cytoplasmicinclusion bodies in scrappings ◦Active reticulate bodies & inactive elementary bodies Treatment : ◦Doxycycline& azithromycin C. pneumonia ◦Atypical “walking” pneumonia ◦Sputum with intracytoplasmicinclusions ◦Prominent dry cough and hoarseness ◦Treatment : Macrolidesand tetracycline C. psittaci(psittacosis / ornithosis) ◦Atypical pneumonia with hepatitis ◦Cough may be absent and when present non-productive at
first then scant mucopurulent ◦Treatment : Doxycycline |
Mycoplasma |
Mycoplasma pneumoniae ◦Young adult with atypical pneumonia ◦Mulberry-shaped colonies on media containing sterols ◦Positive cold agglutinin test ◦Treatment: erythromycin, azithromycin, &
clarithromycin(NO CEPHALOSPORINS or PENICILLINS) Ureaplasma urealyticum ◦Adult with urethritis, prostatitis, renal calculi ◦Alkaline urine; urease(+) ◦Treatment: erythromycin or tetracycline |
Dimorphic Fungi |
Body Heat Changes Shape for the dimorphic fungi -Blastomyces -Histoplasma -Coccidioides -Sporothrix |
Pseudohyphae(Candida
albicans) |
•Hyphaewith constrictions at each septum |
Spore types |
Conidia -Asexual
spores; formed off hyphae; common; air-borne Blastoconidia -“Buds”
on yeasts (asexual budding daughter yeast cells) Arthroconidia -Asexual
spores formed by a “joint” Spherules and Endospores(Coccidioides) -Spores
inside the spherules in tissues |
Malassezia furfur |
Normal skin flora (lipophilicyeast) Patient with blotchy hypo-pigmentation of skin KOH scrapping shows “spaghetti and meatballs” or “bacon
and eggs” yeast clusters & short curved septate hyphae Treatment : Topical selenium sulfide; recurs |
Dermatophytes(group
of fungi) |
Filamentous (monomorphic) fungi Three genera: Trichophyton–skin,
hair and nails Mircrosporum–hair
and skin Epidermophyton–skin
and nails Patient with scaly, ringlikelesions (Tineas) of skin. May
involve hair shaft or nails. KOH scrapping shows athroconidiaand hyphae Treatment : Topical imidazoleor tolnafate ID reaction (dermatophytID) = allergic response to
circulating fungal antigens. |
Sporothrix schenckii |
Subcutaneous mycoses Patient with subcutaneous/lymphocutaneous mycetoma Gardener, florist, basket weaver, or alcoholic rose-garden
sleeper disease (homeless) Cigar-shaped yeast in pus Treatment : intraconazoleor amphotericinB |
Histoplasma
capsulatum |
Deep fungal infection; dimorphic fungi Normal patient with acute pulmonary; IC patient with
chronic pulmonary or disseminated infection (FUNGUS FLU) States following drainages of Great Lakes to Gulf of
Mexico Exposure to bird or bat excrement Sputum or blood cultures with mononuclear cells packed
with yeast cells (tiny yeast inside macrophages) Treatment: Ketoconazole, amphotericin B |
Coccidioides
immitis |
Deep fungal infection; dimorphic fungi Normal patient with erythemanodosumor self-resolving
pneumonia IC patient with calcifying chronic pulmonary or
disseminated infections Pregnant female in 3rdtrimester, disseminated infection Desert southwest Sputum has spherules with endospores Treatment : AmphotericinB |
Blastomyces
dermatitidis |
Deep fungal infection; dimorphic fungi Normal patient with acute pulmonary symptoms IC patient with chronic pulmonary or disseminated
infection North and South Carolina (otherwise coexists with
Histoplasma) Sputum has broad-based, budding yeasts with double,
refractilecell walls. Treatment : Amphotericin B |
Aspergillus
fumigatus |
Monomorphicfilamentous OPPORTUNISTICfungi Patient with asthma allergies –growing mucous plugs in
lung Patient with cavitarylung lesions –fungus ball Patient with burns –cellulitis, invasion IC patient –pneumonia, meningitis Septatehyphaebranch at acute angles Treatment : Itraconazole or Amphotericin B |
Candida albicans |
OPPORTUNISTICfungi Forms germ tubes at 37˚C; pseudohyphae& true
hyphaewhen invades tissues Germ tube test demonstrates pseudohyphaeand hyphae IC patient, overuse of antibiotics –thrush, spread down
GIT, septicemia IV drug abusers -endocarditis Treatment : topical
or oral imidazoles; nystatin Disseminated
: AmphotericinB or fluconazole |
Cryptococcus
neoformans |
Encapsulated (monomorphic) yeast; OPPORTUNISTIC fungi Pigeon breeder with acute pulmonary symptoms Hodgkins/AIDS patient with meningitis India Ink mount of CSF with encapsulated yeasts Treatment : AmphotericinB + flucytosineuntil
afebrile(minumum10 wks), then fluconazole |
Mucor, Rhizopus,
Absidia |
Ketoacidoticdiabetic or leukemic patient with
rhinocerebralinfection Biopsy with non-septateirregular-width hyphaebranching at
90˚ angles. Treatment : High
fatality rate (rapid growth and invasion) Debridenecrotic
tissue & start AmphotericinB fast. |
Pneumocystis
jiroveci |
Obligate extracellular parasite Premature infant or AIDS patient with atypical pneumonia Biopsy with honeycomb exudates and silver-staining cysts X-ray ground glass Treatment : TMP-SMX
for mild Dapsonefor
moderate to severe |
Meningitis |
|
Bacterial
Meningitis |
|
Vaginitis |
|
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