Bacteriology Flashcards

Question

Bacterial Stains

Answer 1

1. Gram stain – Gram negative (red) and positive (blue) – describe morphology --- Crystal violet – primary stain --- Gram’s iodine – mordant - -- Acetone/Alcohol – decolorizer\* --- Safranin – counterstain  How to judge quality of a gram stain- are the polys blue? If so, slide is under-decolorized.  Are the polys washed out? If so, the slide is overdecolorized  Poor quality stains must be repeated

Answer 2

Cause of diarrhea  Major reservoir – swine  Human usually infected by non pasteurized milk  Septicemia in iron overload syndromes  Mesenteric adenitis – RLQ pain mimics apy  Grows well at 4\*C (like Listeria)  CIN agar (Cefsulodin-irgasan-novobiocin)  Has been associated with banked blood infections – Transfusion related infection

Answer 3

Gram + bacillus ## Footnote Bacillus species – boxcar shaped gram positive rods catalase enzyme + spores B. Anthracis cause of Anthrax Infection of herbivores bioterrorism - due to highly resistant spores easily disseminated into the environment Infections – skin, pulmonary and GI black eschar skin lesions Culture: medusa head colonies on BAP, non-hemolytic, non-motile, Pen SS B. cereus – food poisoning rapid onset (1 – 6 hr) (cereulide = emetic exotoxin) Fried rice, beta hemolytic and motile

Answer 4

Expectorated sputum specimens are rejected for bacterial culture based on this criteria:  Cells observed on 10X objective (low power field)  \>= 25 epithelial cells /field  Sputum is judged to be spit / not sputum  This is not an acceptable specimen for bacterial culture  Can accept for AFB , fungus, etc.

Answer 5

@ 15 species in humans  Staph epidermidis –  major skin normal flora,  major cause of subacute bacterial endocarditis.  Pathogenicity from cell adhesion factors forming biofilms on biologics and plastic  Staph saprophyticus –  urinary tract infections in the child bearing age female,  this species adheres in greater #’s to epithelial cells than other SCNG.  Novobiocin resistant by KB disk test  Staph hemolyticus –  line related sepsis,  this CNS is hemolytic on blood agar, do not confuse with Staph aureus (which is coagulase positive)

Answer 6

 Branching gram positive bacilli that do not form spores, capable of forming sulfur granules in tissue – often found on normal tonsil  Actinomyces israelii – associated with oral, thoracic, and abdominal infections, IUD infections.  Bread crumb colonies in broth, molar tooth colony on agar plates.  Penicillin susceptible.

Answer 7

E. coli Klebsiella oxytoca (pneumoniiae is negative) Citrobacter koseri (freundii is negative) Plesiomonas shigelloides most Aeromonas spp Proteus vulgaris Pasteurella spp Cardiobacterium spp.

Answer 8

Gram positive cocci in clusters Positive for Catalase Enzyme Two main groups: Staphylococcus aureus (coagulase +) AND Coagulase Negative Staph (S. epidermidis, S. saprophyticus, S. hemolyticus) Coagulase test = Rabbit plasma + organism incubated at 35\*C and checked at 4 hr and 24 hr

Answer 9

 Bacteroides fragilis group –  growth in the presence or bile,  esculin positive,  main organism in human bowel,  pleomorphic gram negative rod  B. fragilis B. ovatus  B. thetaiotamicron – indole positive  B. uniformis  B. vulgatus

Answer 10

Gram - diplococci  Acute urethritis, endocervix, ocular, rectal, oropharynx  10 – 20 % female ascend to PID 0.5% disseminate  Direct Gram stain useful for males  Transport important – charcoal swabs  Amplification methods increases detection  PPNG = treat with ceftriaxone or quinolones

Answer 11

Psuedomonas aeruginosa  fluorescent pigment and blue green pigment (pyocyanin)  Grape like odor  Growth at 42\*C (Ps fluorescens/putida – no growth at 42\*)  Major pathogen in cystic fibrosis – in combination with Burkholderia cepacia can cause major lung damage  Nosocomial pathogen – associate with water

Answer 12

Negative test means no clot Must check at 4 hours and 24 hours If positive at 4 hours, no need to look at it again in 24 hours Can become negative after initial positive at 4 hours because the isolate produces fibrinolysin later which dissolves the clot. This is why it is important to look at it at 4 hours.

Answer 13

 Burkholderia cepacia  Dry , yellow colony , oxidase negative  Problem organism in cystic fibrosis  Alkaligenes species  sweet fruity odor  Nosocomial / environment  Flavobacterium (Chryseobacterium)  F. meningosepticum is associated with fatal septicemia in the neonate

Answer 14

Fusiform shaped gram negative rods – very pleomorphic  Oxidase negative, Catalase negative  Gliding motility, fingerlike projections from colonies  C. canimorsus – dog bites and bacteremia  Other Capnocytophyaga spp in the human mouth cause bacteremia in cancer patients on chemotherapy

Answer 15

Virulence factors  M protein – resistance to phagocytosis  Capsule – hyaluronic acid – resists complement dependent killing  Streptolysin O and Streptolysin S – cell toxins O is oxygen labile S is oxygen stable  Streptococcal pyrogenic exotoxins  Diseases –  Pharyngitis Impetigo Erysipelas  Cellulitis Puerperal sepsis Toxic Shock  Sequelae: Rheumatic fever and Glomerulonephritis

Answer 16

 Anaerobic diphtheroid – pleomorphic gram positive rod, does not branch  Can be pathogen in cerebral shunt infections – can cause shunt nephritis

Answer 17

Lag Phase - slowing down- not good for biochemical or susceptibility testing, \> 24 hours on agar plate Exponential or Log phase - good for all testing, usually 16-24 hr on agar Stationary phase - good for transporting specimens, ie. Boric acid in urine for culture

Answer 18

 Small curved bacilli  Cause of acute gastritis  Rapidly!! And strongly urease positive – this test is used for identification from antral biopsy tissue  Difficult to grow  Stool antigen and serum antibody can aid in diagnosis and avoid biopsy

Answer 19

detect fermentation of glucose, lactose and Or Sucrose and the production of hydrogen sulfide

Answer 20

catalase negative, gram + rods alpha hemolytic colony only G+R that produces H2S (TSI) Skin infection acquired from swine - erysipeloid Isolated in blood cultures – strongly associated with endocarditis in drug addicts - extensive damage to valve

Answer 21

Group B - Beta Hemolytic (faintly) Gram positive cocci in short chains Catalase negative Camp test positive – Staph aureus strain with camp factor perpendicular to group B Strep – intensifies toxin production of group B Strep (old don't use much)  Bacitracin resistant  Rapid hippurate hydrolysis (4 hr) = positive  Serology to demonstrate group B carbohydrate  Pathogen of neonate – assoc with in utero or perinatal organism acquisition during birth (early onset – 7 days) or late (7 – 28 days) from birth process. Pregnant women screened at 35 – 37 weeks using enrichment methods for GBS.  Pathogen of the elderly – bacteremia, urinary tract , etc.  GBS is susceptible to Penicillin.

Answer 22

Gram positive cocci in chains and or pairs Catalase enzyme negative (important! for differentiating from Staph)  Identified by hemolytic pattern on sheep’s blood agar  Alpha – greening of agar, partial hemolysis of rbc  Viridans Strep, Strep pneumoniae, Abiotrophia  Beta – clearing of agar, complete hemolysis of rbc  Beta hemolytic Strep groups A - G  Gamma – no clearing of agar  Enterococci and Streptococcus Group D

Answer 23

Non lactose fermenters – clear on MAC  Proteus – swarming colonies  Indole positive – P. vulgaris  Indole negative – P. mirabilis  Serratia marcescens – has red pigment/ infection in immune suppressed

Answer 24

require increased CO2 and reduced oxygen to grow

Answer 25

 More than 30 species, L. pneumophila most important  Requires cysteine for growth – media of choice “Buffered Charcoal Yeast Extract agar”  Does not gram stain in direct specimens, use silver impregnation stains in tissue  Pulmonary disease associated with water, cooling towers, shower heads, etc.  Urinary antigen test to detect L. pneumophila type I infection only  Treatment: Erythromycin

Answer 26

 Oral flora – pathogens of endocarditis, can require 2-4 days to grow in blood cultures  Haemophilus aphrophilus = oxidase neg, catalase neg  Actinobacillus actinomycetom-comitans = oxidase neg, catalase pos  Cardiobacterium hominis = oxidase pos  Eikinella corrodens = oxidase pos, pits BAP  Kingella kingii = oxidase pos, hemolytic on BAP

Answer 27

Gram positive bacilli Chinese letter arrangement Corynebacterium species  Catalase +,  diphtheroid morphology,  no spores  C. diphtheriae – cause of Diphtheria  Disease is caused by a phage mediated toxin  Detected by Elek immunoprecipitation procedure  Diphtheritic pseudo membrane adherent in throat  Culture  Cysteine tellurite agar (modified Tinsdale) for isolation –  black colonies with brown halos  Grow on egg containing Loeffler slant then stain with methylene blue to look for metachromatic granules

Answer 28

Enterobacteriaceae  Glucose fermented,  Oxidase = negative  Nitrate is reduced to nitrite  Lactose fermentation on MacConkey Agar  1. E.coli – Lactose positive and indole positive (green sheen on EMB agar)\*  2. Klebsiella pneumoniae – mucoid colony /currant jelly sputum\*  3. Enterobacter

Answer 29

 Mycoplasma and Ureaplasma – have cell membrane only!  Media and transport must contain sterols to protect the membrane.  Do not form discreet colonies – read plates under microscope  M. pneumoniae –  community acquired pneumonia  PPLO = pleuropneumonia-like organism  Genital mycoplasmas  M. hominis – fried egg colony, vaginitis, cervicitis, postpartum sepsis, neonatal infections , pre rupture of membranes  U. urealyticum – rapid urea hydrolysis in broth, NGU, upper genital tract infection, spontaneous abortion, neonatal infections

Answer 30

 Direct detection or ID by Fluorescent antibody stain  PCR for diagnosis  Charcoal containing media for transport and culture – Regan Lowe Charcoal agar  Tiny gram negative coccobacillus  3 stages of disease –(1)Prodromal (2) Catarrhal (3) Paroxysmal Prodromal most contagious  Cough caused by toxin adhering to bronchial epithelial cells, can last for months, esp deadly to young children  Nasopharyngeal swab for culture  Reservoir - adult

Answer 31

gram + rods beta hemolytic, catalase negative causes pharyngitis\* trick - could be confused with Strep pyogenes

Answer 32

will not grow in the presence of oxygen, oxygen is toxic

Answer 33

Neisseria species and Moraxella catarrhalis  Small kidney bean shaped - pairs  Oxidase positive  CTA sugar fermentations for identification  N. gonorrhoeae Gluc + Mal - Lac - Suc -  N. meningitidis Gluc + Mal + Lac - Suc -  N. lactamica Gluc + Mal + Lac+ Suc-  M. catarrhalis all negative, Dna’ase + Don't confuse with Acinetobacter species, have very similar morphology. This is why you must culture for women, do you don't tell them they have gonorrhea with all they have is Acinetobacter (normal flora of female genital tract). Don't need to culture for men.

Answer 34

 Possible agent of bioterrorism, hazard in lab  Fastidious small gram negative cocco bacillus  Reservoir – rabbits, rodents… infected by ticks and flies.  Humans infected by bites or directly from animal blood  Strongly associated with skinning rabbits with bare hands.  Bacteria can penetrate small breaks in skin/intracellular pathogen  Can cause painful skin lesions – lymph nodes - leading to bacteremia (ulcerogladular tularemia) Pneumatic  Culture media must have cysteine\*

Answer 35

ChromAgar - S aureus is mauve Mannitol salt agar S aureus tolerates the high % of Salt (7.5%) and ferments mannitol and turns yellow

Answer 36

requires oxygen to grow

Answer 37

Gram positive cocci in tetrads  Bright yellow pigment  Bacitracin susceptible by KB disk test  Furazolidone resistant (S. aureus is susceptible)  Modified oxidase reaction positive- Microdase test is positive (main test)  Does not ferment Glucose (Staph ferments glucose)  Normal flora & in the environment  Rare!! Infection in immune compromised

Answer 38

 Fusiform gram negative bacilli, spindle shaped with pointed ends  Associated with mouth and respiratory tract abscess  Fusobacterium necrophorum is the type species

Answer 39

MacConkey agar – Differential and Selective Pink = lactose fermentation Clear = lactose non fermentation Differential Only Gram negative bacilli will grow

Answer 40

What requires special transport conditions;  Anaerobes – eSwab or vial (port o cult)/ no oxygen N. gonorrhoeae– Charcoal swab, DO NOT refrigerate (charcoal - protects from harsh environment)  Swabs – Stuart’s or Aimes transport – buffers with peptones etc – preserve viability but not promote growth  Urine – boric acid to promote stationary phase / or refrigerate within one hour, do not culture \>24 hr  CSF – sterile container – keep at room temp or incubate at 35\* C for bacterial culture (for pcr then refrigerate)  Usually refrigerate if can

Answer 41

 Bartonella henselae –  cat scratch disease,  bacillary angiomatosis  Bartonella quintana – trench fever  Chlamydiae trachomatis –  trachoma  STD- spin down shell vial culture, probe, amplification  C trachomatis Serovars L1,L2,& L3 =  Lymphogranuloma venereum  C. pneumoniae (TWAR)- PCR, cell culture  C. psittaci- psittacosis, pneumonia, parrots

Answer 42

Francisella tularensis – tularemia  Bordetella pertussis – whopping cough  Haemophilus ducreyi – chancroid  Pasteurella multocida – dog bite  Capnocytophaga canimorsus – dog bite  Legionella pneumophila – Legionnaire’s  Gardnerella vaginalis – Bacterial vaginosis, can use human blood to culture, hemolytic colonies  Helicobacter pylori – gastritis, ulcer  Calymmatobacterium granulomatis – granuloma inguinale  Streptobacillus moniliformis –rat bite fever  Bartonella henselae– cat scratch, bacillary angiomatosis  Borrelia burgdorferi – Lyme disease  B. recurrentis - Borreliosis Treponema pallidum – syphilis  T. whippelii – Whipple’s disease  Bacillus anthracis – anthrax  Erysipelothrix rhusiopathiae – erysipeloid  Beta Strep group A - erysipelas

Answer 43

Enterococcus and Group D Strep not enterococcus Enterococcus (major spp = E. faecium and E. faecalis)  Bile esculin positive  6.5% salt positive  PYR positive (Gp. A beta Strep also)\*  E. faecium = arabinose fermentation pos E. faecalis = arabinose neg  No well defined virulence factors  Natural resistance to cephalosporins  Ampicillin/Vancomycin drugs of choice  Acquired resistance to vancomycin – VRE  Faecium - resistant to ampicillin, more resistant to vancomycin  Faecalis - resistant to synercid, less resistant to vancomycin  Can use bile esculin agar with vancomycin to screen for VRE  Variety of infections – pathogen of opportunity, NF in intestine, cause UTI, bacteremia, abdominal infections

Answer 44

Vitamin B6 deficient – pyridoxal dependent  Will grow in a blood culture bottle – but not on the blood agar plate sub – needs Staph aureus streak to grow “satellite” or media supplemented with vit B6  Speciated:  Abiotrophia  Granulacatilla  Can cause endocarditis –  more resistant to antibiotics than “normal” viridans strep

Answer 45

Streptococcus bovis  Bile esculin - positive  6.5% NaCl - negative (Enterococcus = +)  PYR - negative  When found in blood associated with Bowel carcinoma. Increased % in bowel due to higher levels of bile or underlying colonic disease  Always susceptible to Penicillin

Answer 46

 To determine if a gram negative rod ferments, assimilates or oxidizes a sugar  Two tubes containing glucose (green indicator) one tube layered with oil/ one tube without oil  It both tubes turn yellow = fermentation  If only tube w/o oil turns yellow = assimilation  If no tubes yellow = oxidizer

Answer 47

Vibrio parahemolyticus  Sucrose negative – green on TCBS  Diarrhea from ingestion of raw fish and shellfish  Vibrio vulnificus – highly virulent  Causes painful skin lesions with muscle necrosis on lower extremities and septicemia in patients with pre existing liver disease  50% fatality rate  Ingestion of raw oysters and shellfish from coastal waters  Lactose positive Vibrio – Green or yellow on TCBS

Answer 48

Streptococcus spp. Clostridium spp. Erysipelothrix spp. Arcanobacterium haemolyticum Anaerobic Gram positive cocci

Answer 49

Acinetobacter – hospital environment and human skin  Major nosocomial pathogen  Acquires antibiotic resistance with pressure  Gram negative cocco baccilli – big diplococci  Acinetobacter baumannii – glucose oxidizer  Acinetobacter lwoffi – glucose non oxidizer  Stenotrophomonas maltophilia  rapid maltose oxidizer  Gram negative bacillus  Resistant to many antibiotics  Nosocomial pathogen – super-colonizer when on long term Imipenem therapy Steno is naturally resistant to Imp

Answer 50

Neisseria meningitidis – meningitis in young adult hallmark petechiae, Gram negative cocci in pairs  Capsular polysaccharide  Complement deficiencies in 7,8,and 9 can predispose to chronic type disease  Adrenal necrosis is referred to Waterhouse Friedrichsen syndrome  Type C is the current endemic strain in the USA – problem in college Freshmen living in dorms recommend immunization  prophylaxis = rifampin carriage in human NP  Therapy = penicillin

Answer 51

Group of alpha hemolytic Strep found as NF in mouth and upper respiratory tract S. mutans S. salivarius S. sanguis S. mitis  Bile esculin negative  Not bile soluble  Optochin resistant - \<=13 mm  cause 30 – 40% sub acute endocarditis in pre-exisitng native valve disease  Variable susceptibility patterns

Answer 52

Streptococcus pneumonia vs. viridans Streptococcus Streptococcus pneumoniae Gram stain = gram positive lancet shaped cocci with a capsul (polysaccharide capsule is virulence factor)  Bile soluble (autolytic in sodium deoxycholate)  Optochin sensitive – 14mm or greater zone around the 6mm disk,  optochin = ethyl hydrocupreine hydrochloride  Pathogen of pneumonia, sepsis & CSF. Vaccinate to prevent  Acquired Resistance to Pen by Pen binding proteins (PBP) I  Quellung reaction to type the 80+ serotypes

Answer 53

 Ehrlichia – intracellular pathogen, tick  fever, leukopenia, thrombocytopenia, elevated serum aminotransferases, no rash (differs from Rocky Mountain Spotted Fever)  E. chaffeensis – human monocytes  Ehrlichia spp. – human granulocytes  found in the midwest, PCR and serology for diagnosis,

Answer 54

Test CSF (containing bacterial antigen) to a battery of latex coated antibodies provided in the test kit . Designed to look for bacterial antigens in CSF. Most useful in patients partially treated with antibiotics with suspected meningitis – so the culture and even gram stain might be negative. Always do culture for confirmation of a negative or positive result.  Neisseria meningitidis B, C, Y, W135 serotypes  Haemophilus influenzae B (best one, but not needed much because of immunization)  Streptococcus pneumoniae  Group B Streptococcus  Lost popularity - expensive, low sensitivity and specificity

Answer 55

Diarrhea +/- fever – polys in the stool  Associated with food – large #’s of organisms to make you ill  Can become bacteremic in immune suppressed (HIV)  Selective media – Hektoen and SS  Does not ferment lactose/ produces H2S  Identification based on biochemical reactions and serologic typing “Kaufman White typing scheme”  O Somatic antigen – cell wall  H flagellar antigens – 2 phases h1 h2  Vi capsular antigen –Found in S. typhi only