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GRAM NEGATIVES ONLY
Big picture then details; focus on differentiation
| Question | Answer |
|---|---|
| Why is Moraxella catarrhalis included in the Neisseria chapter? | It has similar morphology |
| Are Neisseria spp (esp those of main focus) and Moraxella cytochrome oxidase and catalse pos or neg? | All are positive except N. elongata and N. bacilliformis |
| Describe the cellular morphology of Neisseria and Moraxella | intracellular (and extracellular?) gram negative diplococci |
| How can Moraxella be differentiated from Neisseria spp? esp since it is also catalase and oxidase positive and is a gram neg diplococcus? | M. catarrhalis is DNAse positive and butyrate esterase positive in contrast to Neisseria spp. |
| Are Neisseria aerobic or anaerobic, motile, and how do they respond to CO2? | they are aerobic, non-motile, and many are capnophilic requiring CO2 for growth |
| What mineral do both N. meningitidis and gonorrheae require for growth and what virulence factor is associated? | Iron: they have transferrin receptors and compete with host for iron |
| Which morphologically distinct colony types of N. gonorrheae are virulent and why? what happens with subsequent subculture? | Types T1 and T2, because they have pili for attachment to tissues; pili are lost in subculturing. |
| How should specimens to be tested for N. gonorrheae be collected and transported? | Always use rayon or dacron swabs not cotton or Ca alginate; ; should be directly plated to gonococcal-selective media such as JEMBEC plates. A "Z-pattern" is used. If cannot plate directly, transport in something like Amies with charcoal. |
| What media is best for cultivation of N. gonorrhoeae and what is needed in addition, explain why | CHOC, does not grow on SBA (bc it is fastidious); also use a selective media such as MTM bc CHOC will also grow commensal organisms from the sample site. |
| What are some selective media for isolation of Neisseria gonorrhoeae and meningitidis, explain the components | Thayer Martin and modified Thayer-Martin (MTM): both have Vanco (vs gram positives), colistin (vs other gram negs) and nystatin (vs yeast; MTM also has TMP to inhibit proteus |
| In addition to Thayer-Martin and MTM, what are two more selective media and what are the differences in their components? | Martin-Lewis which has Vanc, Colistin, and TMP but also anisomycin a diff anti-fungal. NYC agar has the same first 3, but its anti-fungal is Amphotericin B. |
| How are N. gono plates incubated and how would specimens be held prior to plating? | Must be held at room temp, then incubate in 35 to 37 C in a 3 to 5% CO2 atmosphere, humid. |
| Because some gram-neg rods such as Kingella and Acinetobacter can also grow on the selective media, what can be done to differentiate? | Use a penicillin disk: then stain organisms from the edge of the zone of inhibition to examine microscopically: Kingella will be boxy chains of rods, Acinetobacter will be elongated rods, almost filamentous; N. gono is diplococci! |
| What carbohydrate(s) do N. gono vs N. meningitidis utilizes? | N.gono ONLY uses glucose; The latter uses glucose AND maltose |
| Name some test methods that can definitively ID N. gonorrhoeae, aside from the now-outdated Cystine trypticase agar w/ 1% carbs... | 1. detection of enzyme production using chromogenic substrate 2. Coagglutination using monoclonal antibodies 3. Multitest systems using enzyme substrate plus other biochem tests 4. Nucleic acid hybridization and Nucleic acid amplification tests |
| What other pathogenic organism(s) may be detected in some test methods that are used to detect N. gonorrhoeae? | Haemophilus and M. catarrhalis (in culture based tests); Chlamydia trachomatis (in mainly nucleic acid type tests) |
| Which Neisseria spp of concern (major pathogen) may be commensal and in who is risk increased of invasive disease? | N. meningitidis ; asplenic ppl or with complement deficiencies |
| What virulence factor is only found in N. meningitidis; what are found in both (gonorrhoeae as well)? | capsule. Both have Lipooligosaccharide (LOS) which is endotoxin: a lipid A moiety and core LOS (diff from the lipopolysaccharide of most gram-neg bacilli). IgA PROTEASE |
| What media do N. meningitidis grow on (compare to gono); how do encapsulated strains appear? | they grow on CHOC and SBA, gono does not normally grow on SBA. mucoid! |
| What test is always done on suspected isolates of Neisseria? | oxidase- all are positive |
| If an isolate is identified as N. meningitidis, what else needs to be determined? | The serogroup- there are 12 |
| List the most common disease-causing serogroups of N. meningitidis | A, B, C, Y, W-135 |
| Two main diseases that can occur if Neisseria meningitidis enters the bloodstream; | meningococcemia (sepsis), meningitis, or both. |
| What are some possible results/symptoms/sequelae of meningococcemia? | petechiae, purpura, thrombosis , and in fulminant cases can become DIC/septic shock/or hemorrhage in adrenals |
| What is Waterhouse-Friderichsen syndrome? | potential complication of meningococcal sepsis, it is hemorrhage in the adrenal glands |
| N. lactamica can mimic N. meningitidis. What test can diff them and why? | ONPG: o-nitrophenyl-B-D-galactopyranoside; it detects lactose utilization usu within 30 mins. Only lactamica is positive. |
| Where do other Neisseria spp reside as commensals? | the upper respiratory tract |
| What are the HACEK group known for being and name them | unusual causes of endocarditis; Haemophilus, Aggregatibacter (formerly Actinobacillus), Cardiobacter hominis, Eikenella, and Kingella |
| The HACEK group is not based on taxonomic relationships but on the organisms’ propensity to cause__________. All HACEK organisms are commensals of the human ___________. | endocarditis; oropharynx |
| Most endocarditis is caused by what? (non-HACEK) | gram-positives such as Staph aureus and Streptococci |
| What differs in requirements of growth media between H. influenzae and parainfluenzae? | H. parainfluenzae only requires factor V/ NAD; H. influenzae requires both |
| What two Haemophilus organisms require both X and V factor (hemin and NAD) and how do you tell those apart? | H. influenzae and H. haemolyticus; H. haemolyticus will cause beta hemolysis on horse or RABBIT blood agar; influenzae will not |
| What factor do the Haemophilus spp with "para" in the species name require, and don't require? | They only need NAD (V factor), not X. |
| If a haemophilus spp requires both X factor and V factor, will it grow on SBA? what if it needs only V factor or only X factor? | No- SBA only has X factor which is directly available from blood cells; V factor can only be obtained on lysed blood media, so use CHOC, bc will NOT grow on SBA; To get X factor only, SBA is suffiicient. |
| How is suspected H. influenzae isolated? What can be added to reduce overgrowth of normal respiratory organisms? | On CHOC agar, at 33 to 37 C, in a 5 to 10 % CO2 atmosphere. Bacitracin |
| Because of low specificity and sensitivity of gram stain in id'ing Haemophilus, what other stains may help? | acridine orange or methylene blue |
| What does N. gonorrhoeae produce in much greater abundance than meningitidis, and how is it tested for? | Catalase- the superoxol test uses 30% h2O2 vs the usual 3% used for catalase tests; N. gono should begin bubbling in less than 1 second |
| What is the serotype of Haemophilus influenzae based on? | The polysaccharide of the capsule |
| Do encapsulated Haemophilus species tend to cause invasive or localized disease? | Encapsulated species can travel farther thus causing more invasive disease; non-encapsulated species have more adherent abilities that enable them to cling to tissues, causing localized disease |
| Can nonencapsulated species of Haemophilus be serotyped? | No – they are considered non-typable Haemophilus influenzae, NTHi |
| What Haemophilus serotype used to cause the most invasive disease, especially in children, causing meningitis? Why has this changed? | Serotype b, a vaccine is now available in most Western countries |
| What two species of Haemophilus are difficult to differentiate from H. influenzae? Describe the diseases that they cause | Haemophilus aegyptius, and Haemophilus influenzae biogroup aegyptus; the former causes conjunctivitis (pinkeye), the latter causes conjunctivitis followed by Brazilian purpuric fever with symptoms of fever, purpura, leading to septicemia; high mortality |
| What does Haemophilus ducreyi cause a is it a normal flora of the body? | Chancroid a.k.a. genital ulcer disease; no it is not |
| What specialized media is used to isolate Haemophilus aegyptius? | Enriched chocolate agar with IsoVitaleX |
| What specialized media is often used to isolate Haemophilus ducreyi? | Enriched chocolate agar or Nairobi biplate: one half is GC agar plus 2% bovine hemoglobin and 5% fetal calf serum; an on the other side Mueller Hinton agar w/ 5% chocolatized horse blood |
| What three types of media are often used for suspected Haemophilus, and what would indicate this is likely a Haemophilus species? | SBA, CHOC, MAC. Growth of a gram-negative pleomorphic diplococcus only on CHOC is a clue that you are dealing with Haemophilus species . |
| Haemophilus has what kind of odor? | Bleachy |
| If a Haemophilus species requires factor X, what will it produce in the porphyrin test? | It will be negative (no fluorescence) because it does not have factor X which is required to produce porphyrins (cannot synthesize heme, need hemin, which is factor X) |
| What is the principle of the porphyrin test in determining factor requirements (heme production capability) of Haemophilus spp? What is added to detect porphobilinogen, the product ? | Based on whether the organism can convert ALA (d-aminolevulinic acid) into porphyrins which are intermediates in synthesis of X factor. Kovac's reagent, which is p-dimethylaminobenzaldehyde. |
| What is the most prevalent HACEK involved in endocarditis? It does not require but grow better with? | Aggregatibacter aphrophilus, (formerly Haemophilus and parahaemophilus aphrophilus); CO2; yellowish colonies!! |
| What species of Aggregatibacter is found as normal microbiota in humans , has been found as a cause of subacute bacterial endocarditis and in juvenile periodontal disease? what may its very small colonies present after 48 hours? | A. actinomycetemcomitans; the colonies may require over 24 hours and form distinctive star shapes in their center with 4 to 6 points |
| WHat spp of the HACEK group is normal flora of nose/mouth throat and oral infections or dental procedures usu precede endocarditis often having large vegetations of the aortic valve and no fever? WHat are its growth requirements? | Cardiobacterium hominis; MUST have 5% CO2 in a humid environs |
| What traits are helpful in diff'ing Aggregatibacter from Cardiobacter? | C. hominis is catalase negative and indole positive; also C. hominis may cause agar pitting |
| This HACEK organism is the least likely of the group to cause endocarditis and is similar to Moraxella except in what biochem test? How are other infections often caused? | Eikenella corrodens; can cause agar pitting; It is catalase negative in contrast; Infection form trauma especially from fist fight wounds and human bites, is an opportunistic bacteria |
| What can Cardiobacterium hominis display on gram stain? | rosettes of bacterial cells, swellings, filaments, and can be falsely-gram positive |
| What is unique about Kingella in gram stain, and how do they appear, and what test diffs them from Moraxella and Neisseria | They resist decolorizing; rods with squared ends in chains; Kingella is catalase negative usually, in contrast. |
| what kind of infections does Pasteurella cause and how is it transmitted; What is the primary species isolated? | zoonotic; can cause systemic infection such as pneumonia, sepsis, arthritis, meningitis, endocarditis, BUT mostly causes CUTANEOUS from bites. Often from feline bites. P. multocida |
| What is a unique staining characteristic of Pasteurella multocida? | frequently observe bipolar staining (like Y. pestis, safety pin appearance); appear ovoid, filamentous or as bacilli |
| What may help diff Pasteurella from Haemophilus? | growth on SBA (not as satellitism!) and bipolar staining |
| What are the three clinical stages of Brucellosis? How is it acquired? | A zoonotic disease found in ppl working with animals and animal products transmitted by aerosol, percutaneously, or orally. Acute, subchronic (undulant fever!), and chronic |
| What is undulant fever characterized by? | normal morning temps and high afternoon/evening temps plus arthritis and in males epididymoorchitis. |
| What are the four main spp of Brucella known to cause human disease? | B. melitensis, B. abortus, B. suis, and B. canis. |
| Why can it be difficult to diagnose Brucellosis with direct clinical examination of specimen? WHat is used to diagnose? | It is a facultative intracellular pathogen, can reside in phagocytic cells and samples are from blood or bone marrow and isolation is difficult esp in chronic disease. Serologic testing plus pt history and perhaps x-ray (arthritis) |
| What differs between Capnoctyophaga species biochemically for those found as normal flora of the human mouth versus of cats AND dogs' oral cavities.... | The species found in humans are negative for most biochemical reactions including indole although they may reduce nitrates and hydrolyze esculin; the latter are oxidase and catalase positive |
| Differentiate disease states and Capnocytophaga species they correlate with | C. ochracea, C. gingivalis and C. sputigena of human source are indicated in diseases such as periodontitis, oral ulcers, sometimes endocarditis, septicemia in neutropenic patients. C. canimorsus or cynodegmi in fulminant disease aft dog/cat bite |
| Francisella: which species most implicated and describe oxygen requirements and media for growth | F. tularensis; are strictly aerobic, and like Brucella species are facultatively intracellular. Require supplementation with cystine, cysteine, or thiosulfate- can be CHOC, MTM, or BCYE. They Do not grow on MAC or EMB. |
| Francisella: most common type of infections and source | Zoonotic from rabbits, deer fly, rats, ticks etc, ; can be ingested, inhaled, bug bites or contact with tissues. Most infection is ulceroglandular: ulcer at site & regional node swelling; also pneumonia, eye, typhoidal (intestinal inflammation) |
| Francisella is a biosafety level III agent. Give main biochemical features and methods of ID | Oxidase, urease, factor X, V and satellite negative; weakly catalase and B-lactamase positive; DFA, monoclonal antibody immunohistologic staining, PC, slide agglutination, or single serologic test. |
| Legionella: primary transmission method and range of infection types | Inhalation; asymptomatic, or mild upper respiratory tract infections up to pneumonia. Specifically, febrile disease with pneumonia (Legionnaires), and febrile disease without pulmonary involvement (Pontiac fever) |
| Legionella: where where can they be found in human and natural environments? | Aquatic sources such as lakes, springs, etc. L. longbeachae in soil, mud, etc.; human water systems as well because they resist chlorine treatment, including hot water or cold water systems, cooling towers, resp equioment, humidifiers, AC systems... |
| Capnocytophaga gram stain and colonies on agar, brief description | Thin often FUSIFORM Graham negatives resembling Fusobacterium species; can be spindle shaped, coccoid, or curved filaments. Can produce gliding motility on solid surfaces, on agar often adherent yellow orange pigment. similar to Eikenella appearance |
| What species of Capnocytophaga are normal inhabitants of the oral cavities of dogs and cats? | C. canimorsus and C. cynodegmi |
| Differentiate the appearance of colonies of Capnocytophaga and Eikenella on CHOC | The former exhibits more spreading away from colony centers than does Eikenella corrodens |
| According to one source, Legionella are nondetectable on gram stain; however textbook states is a lightly staining gram negative Bacillus; what can be done to enhance the staining intensity? | Extend the Safranin counterstain to at least 10 minutes |
| What is the best media to isolate Legionella and what is required for growth | Buffered charcoal yeast extract, BCYE with L-cysteine; legionella do not grow on SBA but may appear on chocolate agar containing L-cysteine. |
| Describe the colony appearance of Legionella species on BCYE; | Grayish white or blue-green; under a dissecting microscope have a central ground glass appearance with a pink , bottle green or light blue periphery. |
| What is the usefulness of exposing Legionella colonies to long wave UV light at 366 nm? | Clinically significant species can be grouped according to auto fluorescence color; L. pneumophila , for example, will auto fluoresce as a pale yellow green. |
| What rapid assays are useful for detection of Legionella species; what should be used in conjunction with these rapid tests due to sensitivity and specificity issues? | Urine antigen detection, and direct fluorescent antibody test; culture on BCYE supplemented with L-cysteine |
| What Bordatella species are primary and of what body site? | Bordetella pertussis and Bordetella parapertussis, which causewhooping cough although para-pertussis is milder |
| This Bordetella spp is not the cause of whooping cough but is an opportunistic pathogen causing respiratory and wound infections; What newer spp are found in immunocomped bacteremia and wound or ear infection? | B. bronchiseptica' B. holmesii, B. trematum |
| What does B. Pertussis possesses which facilitate attachment to ciliated epithelial cells? What toxins does it also possess? Both of these are virulence factors. | 1. Filamentous hemagglutinin, FHA 2. Pertussis toxin, PT 3. Adenylate cyclase toxin 4. Tracheal cytotoxin |
| When the main capacity of pertussis toxin? | Modification of host proteins, by adenosine diphosphate-ribosyl transferase which interferes with signal transduction |
| What Bordetella species possess the gene for pertussis toxin but do not express the complete operon? | B. parapertussis and B. bronchisepta |
| Of all childhood diseases for which vaccination is recommended, which is the only with increased incident in recent decades? Why? | Pertussis; infants below six months are too young to be vaccinated & are greatest risk; the vaccine gives short-lived immunity ,requires boosters. Also, the increase of reporting adolescents and adult cases as well as additional tools such as PCR |
| What is involved in contemporary laboratory diagnosis of pertussis? | Culture isolation with or without PCR or DFA testing |
| How are specimens for suspected Bordetella pertussis appropriately collected? | Nasopharyngeal swabs or aspirate, throat not recommended. Plate directly to culture media or transfer to an appropriate transport system at bedside such as Regan-Lowe or Amies with charcoal |
| How should transport systems for Bordetella pertussis be chosen? | at RT. Based on transport time and testing to be done: a transit time<2 hrs and DFA to be done, express into 1% casein hydrolysate sol'n. OR, Amies w/ charcoal for up to 24 hours. When is Regan-Lowe used? |
| What is Regan-lowe transport medium and when is it used? | In situations requiring overnight transport or over several days half strength charcoal agar with 10% horse blood and 40 mg/L cephalexin |
| What is a primary diagnostic strategy for rapid detection of Bordetella spp? | PCR using at least two DNA targets such as IS481 and pxtS1 |
| Clinical specimens can be examined for Bordetella species microscopically using only what kind of staining? How do they appear? | DFA stainng ONLY along with CULTURE; small fat bacilli or coccobacilli with intense peripheral yellow-green fluorescence and darker centers |
| What has been the most successful media formulation for isolation of Bordetella spp and what is the most successful alternative often used now///and what other agar should be inoculated? | Bordet-Gengou potato infusion agar; Charcoal agar supplemented with 10% horse blood and 40% cephalexin (like Regan-Lowe except full strength charcoal); use a non-cephalexin plate additionally, in case the strain is inhibited by it |
| How do B. pertussis appear on charcoal-horse blood/Regan Lowe vs Bordet-Gengou? | smooth shiny silver, like mercury vs. hemolytic on Bordet-Gengou |
| Suspicious colonies for B. pertussis/parapertussis should be screened further using one of what two types of antisera? If these are clear, how are results confirmed? | fluorescein-labeled (fluorescetn staining) or agglutinating. No confirmation is needed. |
| What Bordetella spp is sometimes a normal flora of dogs and cats and infects humans after being bitten? | B. bronchisepta |
| Although there are notable exceptions, are most enterobactericeae oxidase positive or negative? what else is GENERALLY true? | NEGATIVE; most reduce nitrate to nitrite and all are glucose fermenters. |
| What Enterobacteriaceae are NOT motile at body temp? | Klebsiella, Shigella, Yersinia |
| What are Enterobacteriaceae as far as aerobic or anaerobic metabolism? | FACULTATIVELY ANAEROBIC (so aerobic but can do without oxygen) |
| Why is colony morphology on nonselective media not helpful in id of Enterobacteriaceae ? | They look very similar to one another: large, moist gray colonies although many E. coli strains are B-hemolytic |
| What media are useful in presumptive ID of enteric pathogens? | MAC and EMB (differential for lactose fermentation and selective for gram-negs); HE and XLD highly selective for Salmonella nd SHigella |
| What are the 7 "tribes" of Enterobacteriaceae based on biochemical characteristics? | Escherichieae; Edwardsielleae; Salmonelleae; Citrobacteriaceae; Klebsielleae; Proteeae; Yersinieae |
| What tribe are Proteus, Morganella, and Providencia contained in? What differentiates this tribe? | Proteeae; ability to deaminate phenylalanine- have enzyme phenylalanine deaminase |
| What genus other than Escherichia is in the same tribe? What can all species of this genus cause? | Shigella; bacillary dysentery |
| What characterizes dysentery? | blood, mucus, and pus in the stool. |
| What are some differences between E. coli and Shigella spp? | E. coli are mostly motile, Shigella nonmotile; IN contrast to E. coli, Shigella don't use acetate or mucate, if there is trouble discerning. Generally SHigella ferments lactose after 48 hours, a delayed reaction |
| What SHigella spp is the most virulent and what does it produce that is also produced in enterohemorrhagic E. coli strains such as O157:H7 | S. dysenteriae; Shiga toxin (verotoxin I, a phage-encoded toxin identical to Shiga) |
| What is the recognized most common cause of UTI? What is the primary associated virulence factor? | E. coli; pili/fimbriae that allow adherence to epithelial cells and avoid being washed out with urine flow |
| What is a main diff btw enteropathogenic E. coli and enterohemorrhagic or enteroinvasive? | the first mainly causes only diarrheal illness, without the invasiveness or toxins |
| What is the EHEC strain O157:H7 associated with, disease-wise/clinically? | hemorrhagic diarrhea, colitis, and HUS: hemolytic uremic syndrome |
| What characterizes HUS and what E. coli strain is a cause? | low platelet count, hemolytic anemia, kidney failure O157:H7 |
| What distinguishes E. coli O157:H7 from Shigella or EIEC infections? | lack of leukocytes in stool |
| What is another acronym for EHEC? | STEC: Shiga toxin- producing E. coli |
| What kind of media is useful for culturing E. coli O157 and why? describe | SMAC, MAC w/ sorbitol instead of lactose: This strain doesn't ferment it in 48 hours (remain colorless), whereas other strains do and produce pink colonies within that time frame |
| What is the MUG assay used to screen for and how | 4-methylumbelliferyl-B-D-glucuronide assay which screens for O157:H7 bc the strain does not produce B-glucuronidase and will not cleave the substrate, giving a negative. Then the strain can be serotyped |
| what species of Yersinia grows better in a cold-enrichment and at what temp is motility better? | Y. enterocolitica |
| What is CIN media and what is it used to isolate? | Cesulodin-Irgasan-Novobiocin, to detect Yersinia enterocolitica. it inhibits normal colon flora better than MAC! |
| What is done with fecal samples suspected of containing Yersinia enterocolitica? | 1st: inoculate into isotonic saline at 4 C for 3 to 4 weeks (COLD ENRICHMENT!!!!) ; do weekly subculturing on CIN agar |
| If CIN media contains mannitol and a pH indicator, what does Y. enterocolitica look like, colony-wise? What other bacteria looks similar? | BUllseye, with red center. Aeromonas also, pink to red center ( a bacterium in the Vibrio and similar groups of miscellaneous gram negatives) |
| Yersinia pseudotuberculosis rarely infects humans but can occur with close contact with rodents, causing a self-limiting infection with spread to mesenteric lymph nodes; how would you diff it from other Yersnia spp? | It is motile at 18 to 22 C; versus Y. pestis which is nonmotile and Y. enterocolitica which is motile 25 to 35 C |
| Y. enterocolitica causes enterocolitis . What are its reactions on MAC at 18 hours, on TSI, and ONPG? | It is a delayed lactose fermenter so...at 18 hours are colorless on MAC but are A/A (Yellow/yellow) in TSI; ONPG positive |
| What does the ONPG test tell about an organism and why? | ID's delayed lactose fermenters - proves they have beta-galactosidase; They do not have permease or are slow to begin making it. The test substrate subs O-nitrophenyl for the glucose of lactose and when cleaved turns yellow. |
| What group of bacteria has these general characteristics: fail to acidify OF overlaid w/ mineral oil or TSI butts; most are oxidase positive (in contrast to ?), prefer aerobic environments some obligate, some oxidize carbs and some assacharolytic | The nonfermenters such as Pseudomonas, Acinetobacter, Burkholderia, Stenotrophomonas |
| Nonfermenters are mainly found ubiquitously in moist environments; where the hospitals may be isolated and what is important regarding commonly used antiseptics/cleaners used? | may be isolated from nebulizers, dialysate fluids, saline, catheters etc.; They can survive chlorhexidine and quaternary ammonium cleaners |
| What is the decision to identify a non-fermenting gram-negative based upon in the clinical setting? | The site of the body in which organism is found for example in normally sterile site such as CSF; whether patient is immunocompromised who are more likely to be infected |
| Name the four Genera most routinely isolated in clinical labs from the non-fermenting miscellaneous gram-negative group | Pseudomonas aeruginosa, Acinetobacter spp; Stenotrophomonas maltophilia, and Burkholderia species |
| Of the 4 genera of non-fermenting miscellaneous gram-negative bacteria most often isolated, which are oxidase negative whereas the other two are positive or weakly positive? | Acinetobacter species and stenotrophomonas maltophilia |
| Is Acinetobacter strictly aerobic or facultatively anaerobic? | Strictly aerobic |
| What two species of Acinetobacter are most commonly isolated and which is more virulent? What differentiates them? | A. baumannii, and A. lwoffi; A. baumannii is more virulent. Both are non-hemolytic but the former oxidizes glucose and the latter does not |
| What are the common characteristics of the Pseudomonas species? | Gram-negative bacilli or coccobacilli; strictly aerobic and usually mobile polar flagella, oxidase and catalase positive, growth on MAC and usually oxidizes carbohydrate |
| What is the leading cause of nosocomial respiratory infection among the nonfermenters? What differentiates it from the less virulent species? | Pseudomonas aeruginosa especially in ventilated patients; in contrast to the other fluorescent pseudomonas spp, it can reduce nitrates, grow at 42°C, and used acetamide. It also produces pyocyanin, a blue pigment. Appears blue-green colonies |
| How do most Pseudomonas aeruginosa colonies appear on SBA? | Most are beta hemolytic with a flat spreading colony and a metallic sheen |
| Name the non-fluorescent Pseudomonas species and tell which two are oxidase negative | P. stutzeri, P. pseudoalcaligenes and P. alcaligenes, P. luteola, and P. oryzihabitans; the last two are oxidase negative |
| Of the nonfermenter clin sig species, which two form wrinkled colonies on SBA agar that look similar and how can you differentiate? | Pseudomonas stutzeri with light yellow or brown wrinkly colonies, and Burkholderia pseudomallei; P. stutzeri is lactose negative, |
| Name the two Pseudomonas species that are oxidase negative and how you would tell them apart | P. luteola and P. oryzihabitans; P. luteola is ONPG and esculin hydrolysis positive, oryz is negative |
| What is unique about Acinetobacter baumanni on Gram stain and on MAC? | It can appear as a gram-positive and as a coccobacillus, and can appear as a lactose fermenter on MAC agar although it is not |
| What two non-fluorescent Pseudomonas species are usually considered contaminants and how do you differentiate? | Pseudomonas pseudoalcaligenes and Pseudomonas alcaligenes: The former is ADH positive and weakly ferments glucose. |
| What kind of media is differential and selective for Pseudomonas aeruginosa | cetrimide agar; it enhances the pigments and inhibit most other bacteria |
| What nonfermenters species of gram-negative causes "glanders" and what is this disease? | Burkholderia mallei; a respiratory disease in livestock which can, although rare, be transmitted to humans causing suppurative acute lung infection |
| What is the cause of melioidosis and what is this disease? | Burkholderia pseudomallei; this is an aggressive granulomatous pulmonary disease with metastatic abscesses in lungs and other viscera; most commonly causes pneumonia but also septicemia cellulitis or draining abscesses |
| Where is Burkholderia pseudomallei more likely to be found, and when should it be considered as the potential isolate? | The aquatic and mud/soil of Southeast Asia, N. Australia, and Mexico. If a nonfermenting wrinkled colony grows on MAC, with bipolar staining on Gram stain, especially in patients who have traveled to those areas |
| What selective media is useful for isolating Burkholderia pseudomallei if it is suspected, and how would these colonies appear compared to on MAC? | Ashdown media which is supplemented with colistin or gentamicin and a red indicator; colonies will be deep pink/red |
| What species of Burkholderia most commonly causes nosocomial infections, especially in people with cystic fibrosis or chronic granulomatous disease? On what medias does it grow well and what increases recovery if there is potential contamination | Burkholderia cepacia ; grows well on MAC but better isolated on BCSA (B. cepaia selective), PC (pseudomonas cepacia, inhibits pseudo), and OFPBL: ox-ferm, poly B, bacitracin, lactose |
| B. cepacia is one of only two clinically encountered species that is positive for what? | Lysine decarboxylase |
| What tests help differentiate Acinetobacter baumannii and Pseudomonas aeruginosa? | P. aeruginosa is oxidase POS, motile, and able to reduce nitrate to nitrite; A. baumannii is oxidase negative, nonmotile and often coccobacillary, and cannot reduce nitrate |
| What non-fermenting miscellaneous gram-negative is CRAB, and what can be treated with? | Carbapenem Resistant Acinetobacter Baumanni; tigecycline or colistin |
| What kind of colonies does Pseudomonas stutzeri produce? | Dry wrinkle light yellow /tan or brown colonies that are adhered to the media and difficult to remove |
| What are some differentiating characteristics between Pseudomonas aeruginosa and Stenotrophomonas maltophilia? | The former is oxidase positive, grows at 42°C and has polar monotrichous flagella vs polar tufts (multiple, lophotrichous) on Stenotrophomonas |
| Differentiate Acinetobacter spp from Chryseobacterium spp; which is highly pathogenic for premature infants? | both often yellow on blood agar but former is oxidase neg and grows on MAC; latter is ox pos and does not grow on MAC; Chryseobacterium |
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