Clinical Bacteriology Review Notes PDF

CLINICAL BACTERIOLOGY REVIEW NOTES Table of Specification # Topics # of Questions 1 Bacteriology Collection, Transport, and Processing Culture Media Ae...

CLINICAL BACTERIOLOGY REVIEW NOTES Table of Specification # Topics # of Questions 1 Bacteriology Collection, Transport, and Processing Culture Media Aerobic Bacteria (Morphology, Staining and Cultural Characteristics, Work-up for identification, Susceptibility tests) Anaerobic Bacteria (Morphology, Staining and Cultural Characteristics, Work- 47 up for identification, Susceptibility tests) Mycobacteria (Morphology, Staining and Cultural Characteristics, Work-up for identification, Susceptibility tests) Atypical Bacteria (Bacteria with unusual physiology and growth requirements) Bacteriologic examination of water and milk 2 Mycology Collection, transport and examination of clinical specimens Culture and Identification General Characteristics, Transmission and Diseases 4 3 Virology General Characteristics, transmission, and diseases Collection, transport and examination of clinical specimens 8 4 Molecular Tests Equipment’s, Instrumentation 5 Manual and Automation 5 Microbial Control, Quality Assurance and Control, and Laboratory Biosafety 6 6 Parasitology Parasites (Nematodes Trematodes, Cestodes and Protozoa)- life cycle, morphological characteristics, epidemiology, prevention and control, manner of reporting, 30 and counting Parasitology techniques, Special Procedures, and Quality Assurance Total 100 SPECIMEN COLLECTION, TRANSPORT, AND PROCESSING Specimens for Clinical Bacteriology 1. Abscess g. Pleural fluid washing, brush, a. Superficial Abscess 4. Bone Bronchoalveolar lavage) b. Deep Abscess 5. Cerebrospinal fluid 12. Gastric aspirate 2. Blood 6. Ear 13. Gastric biopsy 3. Body Fluids a. Inner ear 14. Rectal swab a. Amniotic fluid b. Outer ear 15. Urine b. Abdominal fluid 7. Eye a. Midstream Clean c. Peritoneal fluid/ 8. Nasal Specimen Catch Ascites 9. Nasopharyngeal Specimen b. Catheter d. Bile 10. Pharyngeal c. Suprapubic aspirate e. Synovial fluid/ Joint Specimen/Throat 16. Feces fluid 11. Lower-respiratory tract 17. Tissue Samples f. Pericardial fluid specimen (Bronchial Considerations during sample collection and transport If possible, collect the specimen in the ACUTE PHASE OF THE INFECTION and BEFORE ANTIBIOTICS ARE ADMINISTERED. Select the CORRECT ANATOMIC SITE FOR COLLECTION of the specimen. Collect the specimen using the PROPER TECHNIQUE and SUPPLIES WITH MINIMAL CONTAMINATION from normal biota. Collect the APPROPRIATE QUANTITY of a specimen. 1 By: NAD  CLINICAL BACTERIOLOGY REVIEW NOTES PACKAGE THE SPECIMEN in a container or transport medium designed to maintain the viability of the organisms and avoid hazards that result from leakage. LABEL the specimen with: SPECIFIC ANATOMIC SITE, DATE AND TIME OF COLLECTION, PATIENT’S NAME and a UNIQUE ID NUMBER. TRANSPORT the specimen to the laboratory PROMPTLY or make provisions to STORE THE SPECIMEN in an environment that will not degrade the suspected organism/s. NOTIFY the laboratory in advance if unusual pathogens or agents of bioterrorism are suspected. TRANSPORT specimens immediately or with in 30 mins of collection not more than 2 hours. - Anaerobic organisms, transport specimen with in 10 minutes. - If transport is delayed, the specimen can be maintained by storage under certain conditions or with the use of PRESERVATIVES, ANTICOAGULANTS, TRANSPORT or HOLDING MEDIUM, or CULTURE MEDIUM. TRANSPORT CONDITION SPECIMENS Immediately at Room Temperature Body Fluids, Bone, Inner ear, Corneal Scrapings, Foreign bodies, Gastric Aspirates, Suprapubic aspirate for urine, Prostatic samples Within 15 minutes at Room Temperature Cerebrospinal Fluid (CSF) Within 2 hours at Room Temperature Blood and Bone Marrow specimen Within 24 hours at Room Temperature Abscess, Outer ear, Conjunctiva specimen, GI tract specimen, Hair, Nail and skin scrapings, RT specimens, and Tissue specimens Immediately at 4OC Gastric Biopsy Within 2 hours at 4OC Indwelling catheter (urine sample) and Straight catheter (urine sample) Within 24 hours at 4OC Rectal swab, stool culture, and Midstream clean catch urine COLLECTION PROCEDURES 1. Containers for specimens should be STERILE except for stool, which can be collected in CLEAN, LEAKPROOF CONTAINERS. 2. SWABS are NOT RECOMMENDED for collection. - appropriate for specimens from the UPPER RESPIRATORY TRACT, EXTERNAL EAR, EYE and GENITAL TRACT - tips of swab may contain COTTON, DACRON or CALCIUM ALGINATE - SWAB COLLECTION SYSTEMS are available that provide TRANSPORT MEDIA and protect the specimen from drying. 3. For LESIONS, WOUNDS and ABSCESSES: - area should be CLEANSED to eliminate as much of the commensal flora s possible - collect from the ADVANCING MARGIN of the lesion and should be collected by NEEDLE ASPIRATION rather than by swab aspirated material should be placed into a STERILE TUBE or TRANSPORT VIAL A. URINE - CLEAN-CATCH MIDSTREAM URINE SPECIMEN - FIRST MORNING is preferred. - First, cleanse the external genitalia. - Container: Sterile, wide-mouth glass or plastic jar with tight-fitting lids. - Processing: within 2 HOURS AFTER COLLECTION 2 By: NAD  CLINICAL BACTERIOLOGY REVIEW NOTES - Preservation: BORIC ACID or POLYVINYL ALCOHOL: maintain accurate urine colony counts at RT for 24 hours and useful for collection at distant locations B. SPUTUM - -Often collected for the diagnosis of BACTERIAL PNEUMONIA -FIRST EARLY MORNING SPECIMEN is preferred. - Patient should rinse mouth with WATER and expectorate with the aid of a DEEP COUGH directly into a STERILE CONTAINER (expectorated sputum). - 1 specimen: for BACTERIAL LOWER RESPIRATORY TRACT INFECTION - 3 separate early morning specimens: if FUNGAL or MYCOBACTERIAL INFECTIONS are suspected. - Induced sputum: specimens collected through aerosol induction -Laboratory should be informed of whether the specimen is EXPECTORATED or INDUCED. - Gram stain of EXPECTORATED SPUTUM should reveal >10 EPITHELIAL CELLS and >25 WHITE BLOOD CELLS per low power field C. STOOL - Detection of GASTROINTESTINAL PATHOGENS - RECTAL SWAB can be submitted as long as fecal material is visible. -Bacterial infection: 3 specimens- one a day for 3 days - Parasite infection: 3 specimens within 10 days - Excrete DIRECTLY INTO THE COLLECTION DEVICE - STOOL to PRESERVATIVE RATIO- 1:3 - Container: Clean, wide mouth with tight fitting leak-proof lid - Primary goal in the TRANSPORTATION of specimens to the laboratory: MAINTAIN THE SPECIMEN AS NEAR TO ITS ORIGINAL STATE AS POSSIBLE WITH MINIMAL DETERIORATION AND TO PREVENT RISK TO THE SPECIMEN HANDLER - Preservation: If not transported IMMEDIATELY, it can be REFRIGERATED (if the delay is longer than 2 hours, specimen can be added to CARY-BLAIR TRANSPORT MEDIA) Stools for C. difficile toxin assay should be collected WITHOUT PRESERVATIVE & can be REFRIGERATED; if the delay is longer than 48 hours, the specimen should be FROZEN at -70°C ANTICOAGULANTS - used to prevent clotting of specimens, including blood, bone marrow and synovial fluid - SODIUM POLYANETHOL SULFONATE (SPS): most common anticoagulant used for microbiologic specimens; concentration must not exceed 0.025% wt/vol (preferred concentration 0.025%-0.050% wt/vol) - HEPARIN: often used for viral cultures and for isolation of Mycobacterium spp. from blood - CITRATE- diminishes activity of gram-positive cocci. - Sodium Amylosulfate (SAS)- similar with SPS but less effective and inhibits some gram-negative bacteria. HOLDING or TRANSPORT MEDIA - these usually contain substances that do not promote multiplication of microorganisms but ensure their preservation - STUART’s or AMIE’s TRANSPORT MEDIA: commonly used - JEMBEC SYSTEM (contains selective agar and a CO₂-generating tablet): specimens for N. gonorrhoeae - VTM- for viral and bacterial (Mycoplasma, Ureaplasma and Chlamydia) isolation. SPECIMEN PRIORITIZATION LEVEL DESCRIPTION SPECIMENS 1 Critical/ Invasive Amniotic fluid, blood, brain, CSF, heart valves, pericardial fluid 2 Unpreserved Bone, feces, sputum, tissue, other body fluids not listed in level 1 3 Quantitation required Catheter tip, urine, tissue 3 By: NAD  CLINICAL BACTERIOLOGY REVIEW NOTES 4 Preserved Urine, feces, and swabs in transport media STAINING - imparts an artificial coloration to the smear materials that allows them to be inspected using the magnification provided by a microscope. - categories: SIMPLE STAINS, DIFFERENTIAL STAINS and PROBE-MEDIATED STAINS SIMPLE STAINS - directed toward coloring the FORMS and SHAPES present. DIFFERENTIAL STAINS - coloring specific components of the elements present PROBE-MEDIATED STAINS - directed specifically at identification of an organism. GRAM STAINING Gram (+) Cell wall Composes of thick layer of peptidoglycan Consists of glycan chains of alternating N-acetyl-D-muramic acid and N-acetyl-D-glucosamine Teichoic acid [found only on G(+) cell wall] - contributes to the negative charge of the G(+) cell wall; regulates cation Contains exotoxin Gram (-) cell wall Composes of thin layer of peptidoglycan (can be found on the inner part of the cell envelope) protein, phospholipids, LPS (outer membrane) *LPS - Lipopolysaccharide 4 By: NAD  CLINICAL BACTERIOLOGY REVIEW NOTES A. lipid A – major constituent, toxic B. core polysaccharide C. antigenic O – specific polysaccharide for serologic identification LPS [found only on G(-) cell wall] - contributes to the negative charge of the G(-) cell wall; regulates cation Contains endotoxin The periplasm is the specific area for transpeptidation Comparison of a Gram (+) and Gram (-) Bacterial Cell Wall CELL WALL GRAM POSITIVE GRAM NEGATIVE COMPONENT Peptidoglycan Thick Layer Thin Layer Periplasmic Space/Area Absent Present Outer Membrane Absent Present Teichoic Acid Present Absent Lipoteichoic Acid Present Absent Lipoproteins Absent Present Lipopolysaccharide Absent Present Layer All Cocci are Gram(+), EXCEPT: ü Neisseria ü Moraxella / Branhamella ü Veilonella ü Megasphera ü Acidaaminococcus All bacilli are Gram (-), EXCEPT: (BBMACCPELLN) ü Bacillus ü Bifidobacillus ü Mycobacteria ü Actinomyces ü Clostridium ü Corynebacterium ü Proipionebacterium ü Erysipelothrix rhusiopathiae ü Listeria monocytogenes ü Lactobacillus ü Nocardia All spiral organisms are Gram (-) All yeasts are Gram (+) ACID-FAST STAINING STAINING METHODS: 1. Ziehl-Neelsen- Hot Method 5 By: NAD  CLINICAL BACTERIOLOGY REVIEW NOTES 2. Kinyoun- Cold Method Modified Acid-Fast: Modified Kinyuon Method) § Useful for the identification of intestinal coccidian oocyst § Ideal for detetion of Cryptosoridia and Cyclospora parasites in STOOL § Alcohol used (decolorizer) – 1% H2SO4 § Counter stain: Either methylene blue or malachite green § QUALITY CONTROL: Cyrptoporidium spp 3. Pappenheim Method- Differentiates Mycobacterium smegmatis from Mycobacterium tuberculosis 4. Baumgarten Method- Differentiates Mycobacterium leprae from Mycobacterium tuberculosis 5. Auramine-Rhodamine Method- Fluorescent stain, selective for Cell wall of AFB SPECIAL STAINS STAINING STAIN STRUCTURE/BACTERIA TECHNIQUE Albert Malachite green and toluidine blue Metachromatic granules Anthony, Hiss, and Crystal Violet Capsule Gin Dyar Congo Red Cell Wall Dorner Carbolfuchsin and Nigrosin dye Endospore Feulgen Carbol fuchsin DNA Fontana-Tribondeau Ammoniacal silver nitrate and tannic acid Spirochetes Gray Carbol fuchsin and tannic acid Flagella Leifson Carbol fuchsin, methylene blue, and tannic acid Flagella Levaditi Silver nitrate Spirochetes Neisser Methylene blue and crystal violet Metachromatic granules Nigrosin Nigrosin dye capsule Shaeffer-Fulton Malachite green and safranin red Endospore CULTURE MEDIA - any material containing the necessary nutritional and environmental requirements for bacterial growth - CLASSIFICATION according to: PHYSICAL STATE/ CONSISTENCY, COMPOSITION, HOW THE MEDIUM IS DISPENSED AND USE. According to PHYSICAL STATE/ CONSISTENCY: a. LIQUID- without any trace of agar or solidifying substances (e.g. nutrient broth) b. SEMISOLID- contains 0.5-1.5% of agar (e.g. SIM) c. SOLID- contains 2-3% of agar (e.g. BAP, TSI) According to COMPOSITION: a. SYNTHETIC- exact chemical composition of the ingredients are known (e.g. commercially prepared culture media) b. NON-SYNTHETIC- precise composition of some or all of the nutritive substances used are known (e.g. meat extract broth) c. TISSUE CULTURE MEDIA- contains living tissue (e.g. embryonated egg for viruses) According to HOW THE MEDIUM IS DISPENSED: a. PLATED- distributed in sterile petri dishes b. TUBED- distributed in sterile test tubes types: SLANT, BUTT, BUTT/SLANT According to USE: 6 By: NAD  CLINICAL BACTERIOLOGY REVIEW NOTES a. NONSELECTIVE- growth of most non-fastidious microbes (e.g. SHEEP BLOOD AGAR) b. SELECTIVE- growth of 1 type/group of microbes; it may contain certain inhibitory substances c. DIFFERENTIAL- allow grouping of microbes based on different characteristics demonstrated on the medium c.1 DIFFERENTIAL & NONSELECTIVE- e.g. SHEEP BLOOD AGAR c.2 DIFFERENTIAL & SELECTIVE- e.g. MacConkey AGAR d. ENRICHED- contain growth enhancers that are added to non-selective agar to allow fastidious organisms to flourish (e.g. CAP) e. SPECIAL- used to isolate bacteria with specific growth requirements. (e.g LJ medium, TCBS) f. TRANSPORT- these usually contain substances that do not promote multiplication of microorganisms but ensure their preservation g. Mueller Hinton Agar (MHA)- Culture Media for antimicrobial susceptibility testing (AST). CULTURE MEDIA STORAGE - the following are the shelf life or prepared media when stored in a cool, dark place: TUBE with COTTON-WOOL PLUG: 3 WEEKS TUBE with LOOSE CAP: 2 WEEKS CONTAINER with SCREW CAP: 3 MONTHS PETRI DISHES, if sealed in PLASTIC BAGS: 4 WEEKS CULTURE INCUBATION - Most bacteria cultures are incubated at 35°C- 37°C - Some bacteria are CAPNOPHILES: uses CANDLE JAR, CO2 INCUBATOR - Some bacteria are MICROAEROPHILES: uses JARS or BAGS INCUBATION TIME - Most bacterial cultures are held for 48-72 HOURS - Culture for ANAEROBES and BROTH CULTURES may be held for 5-7 DAYS GROWTH GRADING IN CULTURE MEDIA PLATES GRADE DESCRIPTION 4+ Signifies many, heavy growth, if growth is up to the 4th quadrant 3+ Signifies a moderate growth, if growth is up to 3rd quadrant 2+ Signifies a few or light growth, if growth is in the 2nd quadrant 1+ Signifies a rare growth, if growth is in the 1st quadrant only. MICROBIAL GROWTH REQUIREMENTS & NUTRITION Physiologic Requirements of Bacteria: A. According to Oxygen Requirement 1. Aerobes- air contains 15-21 % O2 and 1% CO2 2. Anaerobes 2.1 Obligate anaerobes- does not require O2. Dies after prolonged exposure to air. 2.2 Facultative anaerobes- Most clinically significant bacteria. Considered as aerobes but can grow anaerobically. 2.3 Aerotolerant anaerobes- can survive in the presence of O2 but unable to perform processes unless placed in anaerobic conditions. 3. Microaerophiles- 2-10% O2 for growth. ENVIRONMENT GROUP AEROBIC ANAEROBIC O2 EFFECT Obligate aerobes Growth No Growth Required (utilized for aerobic respiration) Obligate anaerobes No Growth Growth Toxic 7 By: NAD  CLINICAL BACTERIOLOGY REVIEW NOTES Facultative anaerobes Growth Growth Required for growth but can grow in its absence Facultative aerobes Growth Growth Not required for growth but utilized when available Aerotolerant anaerobes Growth Growth Not required & not utilized Microaerophiles Growth if level not too No Growth Required but at levels 16mm § Resistant: zone is 10 mm (susceptible) (-) = no ZOI (resistant) 2. PYR Test: Principle: L-pyrrolidonyl arylamidase hydrolyzes the L-pyrrolidonyl- β-naphthylamide substrate to produce a β-naphthylamine. The β- naphthylamine can be detected in the presence of N,N- methylaminocinnamaldehyde reagent by the production of a bright red precipitate. - More specific than Bacitracin - Results: (+) = bright cherry red color (-) = no color change/ light orange 3. Sulfamethoxazole and Trimethoprim (SXT) Test - Presumptive test for the identification of GAS SCARLET FEVER SUSCEPTIBILITY TESTS 1. Dick’s Test: ✓ 0.1ml toxin (test arm) & 0.1ml toxoid (control arm) ✓ Observe for 24 hrs. ✓ (+) redness in test arm 2. Schultz-Charlton Test ✓ Inject anti-toxin into test arm ✓ (+) fading of rashes ✓ Neutralization of erythrogenic toxin GROUP B: S. agalactiae 1. CAMP Test (Christie-Atkins-Munch-Peterson) in BAP Principle: Certain organisms (including group B streptococci) produce a diffusible extracellular hemolytic protein (CAMP factor) that acts synergistically with the beta-lysin of Staphylococcus aureus to cause enhanced lysis of red blood cells. The group B streptococci are streaked perpendicular to a streak of S. aureus on sheep blood agar. Results: (+) = arrowhead hemolysis (-) = no enhancement of hemolysis 2. Na Hippurate Hydrolysis Principle: The end products of hydrolysis of hippuric acid by hippuricase include glycine and benzoic acid. Glycine is deaminated by the oxidizing agent ninhydrin, which is reduced during the process. Procedure: 16 By: NAD  CLINICAL BACTERIOLOGY REVIEW NOTES Results: (+) = Deep purple color (-) = Colorless or slightly yellow pink color GROUP C,D,&G 1. Bile Esculin Test Streptococci Principle: Gram-positive bacteria other than some streptococci and enterococci are inhibited by the bile salts in this medium. Organisms capable of growth in the presence of 4% bile and able to hydrolyze esculin to esculetin. Esculetin reacts with Fe3+ and forms a dark brown to black precipitate. Results: (+) = Growth and blackening of the agar slant (-) = Growth and no blackening of medium/ No growth 2. 6.5% NaCl Test/ Salt Tolerance Test Principle: The salt tolerance test is a selective and differential medium. Enterococci are resistant to high salt concentration. A heart infusion broth containing 6.5% NaCl is used as the test medium. This broth also contains a small amount of glucose and bromcresol purple as the indicator for acid production. Results: (+) = turbidity (-) = no turbidity 3. LAP (Leucine Aminopeptidase) Test Incubation: room temperature for 5 minutes (+) result: red (-) result: yellow / no color change (+) for: E. faecalis and Pediococcus (-) for: Leuconostoc 4. Pyruvate Broth Test Incubation: 35◦C for 48 hours (+) result: yellow (-) result: green (+) for: E. faecalis (-) for: E. faecium S. pneumoniae 1. Mouse Virulence Test 2. Inulin Fermentation Test 3. Bile Solubility Test Principle: Bile or a solution of bile salt (e.g. sodium desoxycholate) rapidly lyses pneumococcal colonies. Results: (+): Broth clearing (-): Turbid 4. Optochin Test Principle: Optochin is an antibiotic that interferes with the ATPase and production of adenosine triphosphate (ATP) in microorganisms. The Optochin-impregnated disk (TaxoP) is placed on a lawn of organism on a sheep blood agar plate, allowing the antibiotic to diffuse into the medium. The antibiotic inhibits the growth of a susceptible organism, creating a clearing, or zone of inhibition, around the disk. Results: 17 By: NAD  CLINICAL BACTERIOLOGY REVIEW NOTES (+) = susceptible (-) = resistant Equivocal = any zone of inhibition 100 species within the genus Motile metabolically diverse; some species grow best Catalase (+), ferments glucose, hydrolyzes at 55 deg C or higher starch Aerobic/ facultative anaerobes Most grow well on SBA Spores = aid in survival Bacillus anthracis: General Characteristics Anthrax bacillus Catalase (+) Causative agent of anthrax Ferments glucose Grows aerobically/ anaerobically Produces lecithinase Non-motile Growth factor: thiamine (vit. B1) Halophilic (7% NaCl) VIRULENCE FACTORS: D-glutamic Acid Capsule = prevents organism from phagocytosis Anthrax toxin/ Protein Exotoxins (EA, PA, LF) = nontoxic but act collectively to produce damaging effects Anthrax toxin consists of three proteins: 1. Protective antigen (PA) - serves as a necessary binding molecule for EF and LF 2. Edema factor (EF) - an adenylate cyclase that increases the concentration of cAMP in host cells; PA + EF = Edema 3. Lethal factor (LF) – protease; PA + LF = Death INFECTIONS RELATED TO B. anthracis: 18 By: NAD  CLINICAL BACTERIOLOGY REVIEW NOTES 1. Cutaneous Anthrax a small pimple (2 to 3 days after exposure)→ring of vesicles develops→merge→small dark area appears →ulcerates and dries→eschar or black eschar 2. Inhalation Anthrax Woolsorter’s disease/ Ragpicker’s disease acquired when spores are inhaled into the pulmonary parenchyma 3. Gastrointestinal anthrax Via ingestion of the spores Symptoms: abdominal pain, nausea, anorexia, and vomiting, bloody diarrhea (can also occur) 4. Injectional Anthrax Characterized by soft tissue infection associated with “skin popping” Lack of eschar, severity of disease, and increased mortality rate make this form clinically distinct from the cutaneous form Bacillus cereus: General Characteristics: Fried rice bacillus Causes food poisoning due to ingestion of contaminated rice/ other food products Most commonly encountered sp. in opportunistic infections Can be part of the normal fecal biota Motile Penicillin (R) 2 forms of food poisoning: diarrheal and emetic VIRULENCE FACTORS: enterotoxins (heat stable & heat labile) cerelysin, phospholipase C. pyogenic toxin INFECTIONS: Types of Food Poisoning: 1. Diarrheal type = associated w/ ingestion of contaminated meat/ poultry & vegetables 2. Emetic type = associated w/ ingestion of improperly stored fried rice/ reheated rice Bacillus anthracis Bacillus cereus Laboratory Diagnosis: Laboratory Diagnosis: 1. Microscopy >105 cells per gram of food = food poisoning by large (1.0 to 1.5 μm × 3.0 to 5.0 μm) this square-ended (bamboo rod/ bamboo fishing rod organism is confirmed appearance) At least 105 cells per gram of stool = organism as gram-positive or gram-variable rod found singly or the in chains cause of the disease is confirmed unstained central spore BAP: large, feathery, frosted glass colonies, beta 2. Cultural Characteristics hemolytic BAP: non-hemolytic, large (2-5 mm), gray and flat Biochemical tests: ferments salicin; lecithinase w/ irregular margin (+) Medusa head colonies beaten egg white appearance Treatment: String of pearl appearance on agar w/ penicillin Resistant to penicillin and all of the other β-lactam (0.05-0.5 U/mL) antibiotics except for the carbapenems 3. Diagnostic Tests Vancomycin or Clindamycin w/ or w/o an 1. Ascoli test (precipitin test): skin test aminoglycoside Detects thermostable anthrax antigen Uses rabbit antiserum to observe precipitin formation Sample soln: 2g of sample in 5 ml saline placed in 1/100 final concentration of acetic acid 19 By: NAD  CLINICAL BACTERIOLOGY REVIEW NOTES (+) result: precipitin band formation (