BACT TEST 1 AND 2 RATIONALE PDF

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BACT Pre-test Week 1 Which of the following characteristics of bacteria is/are used as criteria for classification? 1- Possession of plasmid 2- Possession of DNA 3- Biochemical reactivity 4- Structural components Which of the following statements is not consistent with the growth curve of bacteria? ...

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BACT Pre-test Week 1 Which of the following characteristics of bacteria is/are used as criteria for classification? 1- Possession of plasmid 2- Possession of DNA 3- Biochemical reactivity 4- Structural components 2. Which of the following statements is not consistent with the growth curve of bacteria? I. The growth rate in stationary phase is zero II. New bacterial material is produced constantly during exponential phase. III. The metabolites of bacteria are depleted during the lag phase IV. The decrease in viability of bacteria in death phase occurs rapidly. a. 2 only b. 4 only c. 1 & 3 d. 2 & 4 e. 2,3, & 4

e.

It won’t be specific as which tube will remain green or turn to yellow

1.

Discussion: ➢ ➢ ➢ ➢

OFBM:

5. ➢ ➢

3.

Discussion: ➢

Discussion:

➢

➢ ➢ ➢

➢

4.

Non sterile stool needs to trim down Enrichment enhance growth Enriched: support growth not affecting other organisms; for fastidious ➢ Lactose: differential MacConkey - pH indicator neutral red (+) pink; (-) colorless ➢ General purpose for non-fastidious (no growth requirements) Which of the following results will most likely to appear when S. aureus is inoculated in OFBM? (1st tube is overlaid with mineral oil) a. 1st tube will turn to yellow; 2nd tube will remain green b. 1st tube will remain green; 2nd tube will turn to yellow c. d.

Both tubes will turn to yellow Both tubes will remain green

Tube A: with mineral oil – promote anaerobic environment Tube B: without mineral oil – aerobic pH indicator: bromothymol blue turns to yellow (+) fermentation Tube 1 yellow, Tube 2 remain green = fermenter (strict anaerobe) • Tube 1 remain green, tube 2 turns yellow = oxidizer • Both turns to yellow = fermenter • Both tubes remain green = non fermenter Which of the following organisms doesn’t have the capability to evade phagocytosis? I. Staphylococcus aureus II. Neisseria gonorrhoeae III. Streptococcus pyogenes IV. Enterococcus faecalis a. 1 & 2 b. 1 & 3 c. 2 & 3 d. 2 & 4 e. 1, 2, & 3 • • • •

Discussion: Lag phase no growth; unfavorable; decreased metabolites Log/ exponential presence of growth; synthesis of cell organelles ➢ Plateau no growth ➢ Death no nutrients; stop or inhibit growth A rectal swab specimen is inoculated in a medium containing select nutrients chosen because few bacteria, other than the organism of interest, can use them. The medium described is ____. a. Enriched b. Enrichment c. Selective d. Differential e. General purpose

OFBM (oxidation fermentation basal medium) - identify who are capable for oxidation and fermentation Fermentation – organisms can metabolize carbon with or without oxygen Oxidation presence of oxygen Check first the characteristic of staphylococcus aureus (facultative anaerobe) – capable of fermentation

➢ ➢ 6.

Identify first the structure of bacteria which are evading phagocytosis Staphylococcus aureus – has protein A (cell wall protein inhibit phagocytosis Neisseria gonorrhea – unencapsulated; has pili (evade phagocytosis) Streptococcus pyogenes & pneumoniae – has polysaccharide capsule and protein M Enterococcus faecalis – none A stool sample was received in microbiology laboratory. The medical laboratory scientist skipped the used Selenite F and directly plated it on BAP. After 18 hours of incubation, majority of the colonies were non-hemolytic and was observed using gram stain technique. It appeared as gram positive cocci. Which of the following organisms most likely was isolated? a. Staphylococcus aureus b. Streptococcus pneumonia c. Enterococcus faecalis d. Staphylococcus schleiferi e. Both A and D

Discussion:

-

➢ ➢ ➢

7.

Stool specimen needs enrichment broth for normal flora Skipped selenite F = more normal flora growth GI tract normal flora – small amounts of S. aureus (majority in skin); non hemolytic and hemolytic strep; gram negative bacilli (major flora) Staphylococcus strains possessing mecA genes has resistance to which of the following antibiotics> a. Methicillin b. Penicillin c. Nafcillin d. Vancomycin e. Methicillin and Nafcillin

Discussion: ➢

8.

2 genes encode PBG (penicillin binding protein) – mecA and mecC - Organism with PBG develop resistance with penicillin - Methicillin, oxacillin and nafcillin: MRSA - to detect MRSA via AST by cefoxitin ➢ other MRSA: HA (hospital acquired), CA (community acquired), LA (livestock) ➢ SCCmec – 15 types of gene o HA MRSA type 1,2,3,6,8 o CA MRSA type 4 o LA MRSA type 9,10 ➢ Beta lactamase resistance of S. aureus – not gene associated; plasmid associated (for mutation or development resistance) - Resitant with penicillin like penicillin G, amphicilin ➢ Responsible gene vanA – acquired from enterococcus conjugation with staph aureus • VISA (vancomycin intermediate staphylococcus aureus) • VRSA (vancomycin resistant staphylococcus aureus Clostridium spp. are most sensitive to oxygen during their ____ of growth. a. Lag phase b. Log phase c. Stationary phase d. Death phase e. Log and stationary phase

Discussion: ➢ Clostridium anaerobic – nilagay sa oxygen dun nag adjust Which of the following gas compositions can be found in anaerobic jars? a. 5% H, 5-10% CO2, & 85-90% N b. 0-2% O2, 5-10% CO2 & 85-90% N c. 5% N, 0-2% O2, 5-10% CO2 & 85-90% H d. 0-2% H, 5-10% CO2 & 85-90% H e. 5% H, 0-2% O2, 5-10% CO2 & 85-90% N 10. The following are the preliminary results of bacterial identification: - Specimen: wound swab - BAP: non-hemolytic colonies

9.

Gram stain: Gram (+) cocci in pairs or clusters Catalase (-)

Which of the following test is the most likely correct to perform? a. PYR and bile esculin b. Bacitracin and CAMP c. Hippurate hydrolysis and CAMP d. Bacitracin and PYR e. Optochin test and LAP Discussion: ➢ ➢

Gram positive cocci; negative catalase = streptococci There are enterococcus that demonstrate beta or none hemolytic; must need to perform bile esculin to confirm presence group D or enterococcus ➢ Positive bile esculin perform PYR to confirm enterococci 11. Which of the following specimens for bacterial culture should not be refrigerated? I. Stool II. Sputum III. Vaginal Swabs IV. Catheter tips V. Synovial fluids a. 4 only b. 3 only c. 1 & 3 d. 3 & 5 e. 2,3,4, & 5 Discussion: ➢ ➢ ➢ ➢

Refrigerated – unpreserved, non-sterile specimens (urine, stool, swab) Room temperature – sterile body fluids (genital specimen, aspirates) CSF stored at RT for 6 hours; >6hrs 37C Freezer temperature - serologic typing for specimen

Specimen priorities • Level 1 most prioritized – invasive collection • Level 4 preserved 12. Which of the following is not a virulence factor of S. aureus? a. Lipase b. Beta-lactamase c. Pyrogenic toxin d. Hemolysin e. Both B and C Discussion: Pyrogenic: • •

Staph does not cause fever Caused by streptococcus

13. Neisseria spp. can be differentiated from its other family members by performing: I. Catalase II. DNase III. Butyrate hydrolysis test IV. Carbohydrate fermentation a. 1 only b. 4 only c. 1 & 4 d. 3 & 4 e. 2 & 3 Discussion: ➢ ➢

Neisseria only catalase positive; all are oxidase positive DNase and butyrate – differentiate Moraxella from neiserria ➢ Carbohydrate- differentiate Neisseria specie 14. Which of the following characteristics is associated with endotoxins? I. May be used as to develop vaccine II. Mostly found in gram negative bacteria III. Has specificity to host cells IV. Part of bacteria produced during growth a. 1 & 3 b. 1 & 4 c. 2 & 3 d. 2 & 4 e. 2,3, & 4

3 types of CAMP Camp test Perpendicular streak (unknown factor) – staph agalactiae linear streak (known factor) = beta hemolysin from s. aureus - (+) arrow head hemolysis • Reverse camp - known– CAMP factor - unknown – alpha toxin and lecithinase from clostridium perfringens • CAMP inhibition - Known: beta hemolysisn (s. aureus) - Unknown: phospholipase D (Arcanobacterium hemolyticum) 16. What is the minimal acceptable amount of CSF that is submitted in the laboratory? a. Greater than or equal to 1mL b. Greater than or equal to 2mL c. Greater than or equal to 3mL d. Greater than or equal to 4mL e. Greater than or equal to 5mL • -

Discussion: CSF tubes 1. 2. 3.

Chemistry or serology section Hematology section Microbiology section - >1ml specimen

Discussion:

Usually, syringed CSF

Exotoxin – secreted by bacteria

- Reverse manner - 1st drop to 3rd tube • Bacterial and viral >1ml • Fungal and mycobacterium >2ml • 1st to perform microbiology 17. Which of the following terminologies related to microbial control has the capability to revert the growth of bacteria when the agent is removed? a. Disinfection b. Bacteriostatic c. Aseptic d. Sanitation e. Pasteurization

o o o o o o

Both gram positive and negative Protein Unstable Highly Immunogenic – used for vaccines Highly toxic Most specific – has specific binding receptors

Endotoxin – integral part of bacteria Only in gram negative bacteria Lipopolysaccharide specifically lipid A - for toxicity (part of structure) o Stable – since part of bacteria o Weakly immunogenic o Low toxicity o Caused fever by gram negative (non-specific) 15. Beta hemolysin is used as the known factor in reverse CAMP inhibition test to detect which unknown factor? a. Lecithinase b. Alpha toxin c. Phospholipase D d. Alpha hemolysin e. Lipopolysaccharide A o o

Discusion

Discussion: Bacteriostatic – inhibit growth; if removed growth will still continue 18. The medical laboratory scientist received and processed a wound abscess. The following microbial test profile was recorded: - Macroscopic examination: yellow colonies in BAP - Microscopic examination: gram positive cocci in tetrads - Biochemical test results: o Catalase test: (+)

Bacitracin susceptibility test : (+) zone of inhibition o Novobiocin susceptibility test: (-) zone of inhibition Which of the following should the medical laboratory scientist do? a. Check the hemolytic pattern and use that as basis for the next step b. Perform coagulase test c. Perform oxidase test d. Subculture colony of interest, the specimen may be contaminated e. Release the result as a normal flora of the skin ➢ Yellow colonies; tetrads = micrococcus ➢ Staph appears in cluster ➢ Streptococcus appears in pair Which of the following anticoagulants may be acceptable in microbiology for blood culture? a. EDTA b. Oxalate c. Citrate d. Heparin e. None of this is considered acceptable ➢ SPS – 0.025% concentration (inhibit antimicrobial) ➢ EDTA, citrate and oxalate – are non-acceptable ➢ Heparin – least choice Mutans group of streptococci can be differentiated from other members of streptococci by: I. Carbohydrate fermentation II. Hemolytic pattern III. Urease IV. Antigen testing a. 1 only b. 4 only c. 2 & 3 d. 3 & 4 e. 1, 2, 3, & 4 ➢ All are not capable to ferment carbohydrates except mutans Which of the following microbial control agents is considered as bactericidal and not sporicidal? a. 2% aldehyde b. X-ray c. Iodine d. QACs e. Both A and D ➢ All are sterilant causing sporicidal ➢ Aldehyde 2% - sporicidal ➢ Xray – ionizing radiation Which of the following characteristics is not consistent with staphylococci? I. Causes pyogenic infections II. Part of normal biota of mucous membranes of human III. Can hemolyze blood IV. Possesses heat stable enterotoxin a. 1 & 2 o

19.

20.

21.

22.

23.

24.

➢ 25.

➢ 26.

b. 2 & 3 c. 1 & 4 d. 1, 2, & 4 e. 1,2,3, & ,4 These are cocci possessing pyrroglutamylaminopeptidase. I. Neisseria gonorrhoeae II. Staphylococcus aureus III. Streptococcus pneumonia IV. Enterococcus faecalis a. 2 only b. 4 only c. 2 & 4 d. 2 & 3 e. 1,2, & 4 ➢ These are positive to PYR = enterococcus ➢ Gram positive PYR (+) = strep pyogenes and enterococcus This organism colonies are lysed directly by applying sodium desoxycholate. a. Staphylococcus aureus b. Neisseria mucosa c. Enterococcus faecium d. Moraxella catarrhalis e. Streptococcus pneumoniae Sodium desoxycholate used in gram (+) for bile solubility = strep pneumoniae Neisseria flavescens can be differentiated from other Neisseria spp. by the use of ___. a. Oxidase b. Catalase c. Carbohydrate fermentation d. ONPG e. Nitrate reduction Carbohydrate fermentation since flavescens is assaccharolytic commensal The following are the preliminary results of bacterial identification: Specimen = urine BAP: non haemolytic colonies Motility (+) Gram stain: Gram (+) cocci in chains Bile esculin (+) Catalase (-) Mannitol fermentation Bacitracin susceptibility: R (+) Optochin susceptibility: R

a. Enterococcus faecalis b. Enterococcus durans c. Enterococcus gallinarum d. Enterococcus raffinosus e. This is not an Enterococcus ➢ 2 motile = flavus and galinarum 27. Which if the following components of cell wall is not found in gram positive cell wall? I. Lipoprotein II. Teichoic acid III. Lipid A IV. Forssman antigen a. 1 & 3 b. 1 & 4

c. 2 & 3 d. 2 & 4 e. 2,3, & 4 ➢ Gram positive – teichoic acid and polysaccharide ➢ Gram negative – lipopolysaccharide, periplasmic space ➢ Lipopolysaccharide – lipid A ➢ Forssman – found in streptococcus pneumonia (teichoic acid example) 28. What will be the color of the end product in PYR test of the suspected organism is Staphylococcus aureus? a. Yellow b. Orange c. Blue d. Red - positive e. Purple ➢ Staphylococcus aureus negative PYR ➢ Staph aureus VP positive 29. Which of the following specimens does not require direct microscopic examination as part of identification workflow? I. Vaginal swabs II. Blood III. Nasopharyngeal swab IV. CSF a. 1 only b. 2 only c. 1 and 3 d. 2 and 4 e. 1, 2, and 3 ➢ Not required for direct: many normal flora (non sterile) and genital specimens 30. The colonies were sub-cultured from NA to BAP, CAP, and MAC. After 24 hours of incubation at 37oC, there were only colonies observed on 1st and 2nd quadrant. Which of the following should be done by the medical laboratory scientist? a. Perform gram staining b. Extend the incubation period of the cultures c. Continue with the biochemical tests d. Suggest for repeat collection of specimen since these are only contaminants e. Both C and A ➢ Lag phase of bacteria are still adjusting to unfavorable environment

BACT Week 2 Pre Test 1.

3.

Which of the following species of Clostridium has the following characteristics: • Motility (+) • Glucose fermentation (-) • Lecithinase (-) • Lipase (-) a. b. c. d. e.

C. difficile C. perfringens C. botulinum C. tetani C. septicum

Explanation:

a. b. c. d. e.

2.

Clostridium spp are o Anaerobes o All are motile (+) except C. perfringens o All are lecithinase (-) except C. perfringens o All are lipase (-) except C. botulinum o All are lactose (-) except C. perfringens o All are glucose (+) except C. tetani and C. septicum Which of the following sugar oxidation will differentiate Pseudomonas putida from the rest of the fluorescent pseudomonads? a. Glucose b. Mannitol c. Sucrose d. Xylose e. Lactose

3 only 4 only 1&2 2&3 3&4

Explanation: -

4.

-

Which of the following Eschericia coli strains produces the enzyme 𝛽 -glucoronidase? I. EIEC II. ETEC III. EPEC IV. EHEC

MUG assay (4-Methylumbelliferyl- ß-D-glucoronidase) o Test to differentiate EHEC from the rest of the E. coli o O157:H7 stain = (+) in MUG assay o O157:NM – non-motile and can ferment sorbitol within 48 hours o Cleaved color blue positive MUG test Which of the following Corynebacterium spp. Has the capability to exhibit cystinase and urease activity? I. C. diptheriae II. C. pseudotuberculosis III. C. ulcerans a. b. c. d. e.

1 only 2 only 1&2 2&3 1,2, & 3

Explanation:

Explanation: -

Flourescent pseudomonads can produce pyoverdin; P. aeruginosa (pyocyanin), P. mosselii, P. monteilii, P. putida, P. veronii, P. fluorescens. o Xylose will differentiate P. putida from the rest of the group o GELATIN HYDROLYSIS: putida (-) to fluorescence (+) o Putida cant reduce nitrate to nitrogen

-

I, II, III are positive for cystine Urease

C. diptheriae C. pseudotuberculosis C. ulcerans

(-) (+) (+)

Nitrate reduction test (+)

Gel/ Starch hydrolysis (+) (+)

5.

Which of the following is not true regarding Klebsiella pneumonia? I. Produces large amount of acids in MRVP broth II. Ferments trehalose and xylose III. Utilizes ammonium salt in Simmon’s citrate medium IV. motile a. 1 only b. 3 only c. 1 & 3 d. 1 & 4 e. 2 & 4

-

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Explanation Production of acid = Methyl Red; Production of acetoin = Voges Proskauer o I = means MR (+) = FALSE - Klebsiella is a lactose fermenter which means all other carbohydrates (xylose, sucrose) can be fermented - RLF: IMVC o Escherichia = ++ -o Klebsiella = -- ++ o Eneterobacter = -- ++ - Klebsiella is NONMOTILE. IV = FALSE What are the expected growth characteristics of Salmonella spp. In XLD, MAC, and HEA? a. Red; colorless; colorless colonies respectively b. Colorless with black center; pink; colorless respectively c. Colorless; colorless; green colonies respectively d. Red with black center; colorless; green colonies respectively -

6.

-

-

-

Explanation: -

-

MAC: Salmonella = NLF – Colorless. XLD: capable of detecting H2S gas production NLF: o E - Erwinia o Y - Yersinia o E - Edwardsiella o S - Serratia o P – Proteus o P - Providencia o M – Morganella o S – Salmonella o S – Shigella PPM characteristics: o Motile, PAD (+), LIA (R/A) – Lysine Deaminase (+), Urease (+) = RUP o Proteus = H2S (+) o Providencia = Citrate (+) o Morganella

Salmonella Shigella -

Motility (+) (-)

H2S (+) (-)

7.

VP (+) o K - Klebsiella o E - Enterobacter o S – Serratia o H – Hafnia Indole (+) = Mor PEKPEC Ples o Morganella o Proteus vulgaris o E. coli o Klebsiella oxytoca o Providencia o Edwardsiella o Citrobacter koseri o Plesiomonas Urease(+) - slow o Citrobacter o Klebsiella o Enterobacter o Yersinia o Serratia Citrate (+) = Pro CHEKS o Providencia o Citrobacter o Hafnia o Enterobacter o Klebsiella o Salmonella entiritidis H2S positive. H2S gas is colorless. H2S indicator (Ferric Citrate/ Ferric Ammonium Citrate) combines with the sulfur source (Sodium Thiosulfate) producing black medium o Salmonella o Proteus o Arizona (Salmonella) o Citrobacter o Edwardsiella LIA = SACE

Which of the following organisms can produce a burgundy colored compound after lysine deamination product combined with ferric ammonium citrate, motile produce green color in phenylalanine deaminase test and utilize citrate as source of nitrogen? a. Providencia spp. b. Salmonella spp. c. Klebsiella spp. d. Citrobacter spp. e. Proteus spp. - PAD (+) = green color. Citrate (+) = Providencia - Lysine Iron Agar o Purpose: detects activity of lysine deamination, lysine decarboxylation, H2S production o The environment should be acidic before deamination or decarboxylation. Hence, presence of glucose. ▪ pH indicator = Bromcresol purple ▪ yellow = production of acid

o

LDA occurs in the slant and LDC occurs in the butt

8.

Which of the following organisms is serologically tested using animal virulence test known as Roemer’s? a. Corynebacterium diphtheria b. Clostridium perfringens c. Bacillus anthracis d. Listeria monocytogenes e. Salmonella entiritidis

Explanation: -

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Characteristic of PPM = R/A o H2S positive ▪ yellow will not be seen anymore ▪ black butt ▪ should be in acidic environment LIA only contains glucose. Little sugar to ferment = low ac...