learning outcomes the student should be able to list the medically important genera and species of...
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Learning outcomesThe student should be able tolist the medically important genera and species of negative non-fermentative gram-negative rodsdescribe their microscobic appearanceList their most important propertiesFor Pseudomonas:-list the important biochemical properties -list the important virulance factors(toxins and enzymes)-list the main routes of transmission-list the important clinical manifestations and describe the pathogenesis-list the important properties used in laboratory diagnosis-list the most important antibiotic resistance properties
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Non-fermentative Gram-negative bacilli
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Enterobacteriacea Grow rapidlyHave simple nutritional requirementsFerment glucoseOxidase negativeDistinguish them from nonfermentative gram-negative rods
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Pseudomonas and related organismsaerobic-nonfermenter-gram-negative bacilliPseudomonas aeruginosaBurkholderia cepaciaStenotrophomonas maltophiliaAcinetobacter baumanniiAcinotobacter lwoffiiMoraxella catarrhalis
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Pseudomonas and related organisms
opportunistic pathogensimportant cause of hospital infectionsresistance to antibiotics
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Pseudomonas Ubiquitous Soil, decaying organic matter, vegetation, waterHospital environmentMoist reservoirs, food, cut flowers, sinks, toilets, floor mops, respiratory therapy & dialysis equipmentEVEN disinfectant solutions
Simple growth requirements(can even grow in distilled water!!!!!!!)
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Pseudomonas Can transiently colonize the respiratory and gastrointestinal tracts of hospitalized patients, particularly those treated with broad-spectrum antibiotics, exposed to respiratory therapy equipment, or hospitalized for extended periods
can cause hospital infections
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Pseudomonas /Physiology & structureSmall gram-negative bacilliStrict aerobeNonfermenterSimple nutritional requirementsMucoid capsuleOxidase positive = enterobactericeae> 10 speciesP. aeruginosamost common
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Pseudomonas /Pathogenesis & immunityMultiple virulence factorsStructural components:Toxins & enzymespyocyaninAntibiotic resistance
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Pseudomonas /Pathogenesis & immunityMultiple virulence factorsStructural components:adhesins (e.g., flagella, pili, LPS, alginate capsule)Toxins & enzymesexotoxin A, pyocyanin, pyoverdin, elastases, proteases, phospholipase C, exoenzymes S and TAntibiotic resistanceis inherently resistant to many antibioticsCan mutate to more resistant straines
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Pseudomonas /clinical diseasesPulmonary infections (cystic fibrosis)Burn wound & other skin & soft tissue inf.UTI(Urinary tract infections)External otitisEye inf. (contaminated contact lens cleaning fluids)Bacteremia & endocarditis
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Pseudomonas /diagnosis & identificationCultureSimpleIdentificationColonial morphology colony size, hemolysis, pigmentation, odorBiochemical testsPositive oxidase test
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Pseudomonas /diagnosis & identificationCulture:beta hemolysis, green pigment, grapelike odorand simple biochemical tests (e.g., positive oxidase reaction; oxidative utilization of carbohydrates)
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Pseudomonas /Combined use of effective antibiotics (e.g., aminoglycoside and -lactam antibiotics) frequently required; monotherapy is generally ineffective and can select for resistant strains
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Pseudomonas /Hospital infection-control efforts should concentrate on preventing contamination of sterile medical equipment and nosocomial transmission; unnecessary use of broad-spectrum antibiotics can select for resistant organisms
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Pseudomonas /
P. aeruginosa also produces a number of different -lactamases that can inactivate many -lactam antibiotics (e.g., penicillins, cephalosporins, and carbapenems).
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P.aeruginosa
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Burn wound infected with Pseudomonas
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P.aeruginosa
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Burkholderia(Formerly classified as Pseudomonas)B. cepacia, B. pseudomalleiImportant human pathogens
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Burkholderia cepaciaLike P. aeruginosais commonly associated with nosocomial infectionsrelatively low level of virulence, rarely cause deathis susceptible to trimetoprim-sulfamethoxazole
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Burkholderia pseudomalleifound in soil, water, vegetationopportunisticmelioidosishighly infectious , careful isolation
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Stenotrophomonas maltophiliamy favorite (the person or animal most people expect to win a race or competition) bacteria
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Stenotrophomonas maltophiliaone of the most commonly isolated nonfermentative, gram-negative bacilliformerly classified as Pseudomonas, Xanthomonasinfections in patients with impaired host defense mechanismsis resistant to commonly used b-lactams & aminoglycosidestrimetoprim-sulfamethoxazole, is the agent most active
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Acinetobacter
oxidase-negativegram-negative coccobacilli
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AcinetobacterA. baumannii, A. lwoffii, A. haemolyticusare recovered in nature & hospitalsurvive on moist and dry surfaces (!skin!)resistant to antibiotics (carbepenems)!!!!!!!!!
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Acinetobacter
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Downloaded from: StudentConsult (on 9 May 2011 07:42 PM) 2005 Elsevier
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Moraxella
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MoraxellaM.catarrhalisAn important pathogenStrict aerobicOxidase positiveGram negative diplococci
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MoraxellaMoraxella catarrhalis is the most important human pathogencommon cause of bronchitis and bronchopneumonia, sinusitis, otitismost isolates are resistant to penicillin (produce b-lactamase)
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