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

Non-fermentative Gram-negative bacilli

Enterobacteriacea Grow rapidlyHave simple nutritional requirementsFerment glucoseOxidase negativeDistinguish them from nonfermentative gram-negative rods

Pseudomonas and related organismsaerobic-nonfermenter-gram-negative bacilliPseudomonas aeruginosaBurkholderia cepaciaStenotrophomonas maltophiliaAcinetobacter baumanniiAcinotobacter lwoffiiMoraxella catarrhalis

Pseudomonas and related organisms

opportunistic pathogensimportant cause of hospital infectionsresistance to antibiotics

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!!!!!!!)

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

Pseudomonas /Physiology & structureSmall gram-negative bacilliStrict aerobeNonfermenterSimple nutritional requirementsMucoid capsuleOxidase positive = enterobactericeae> 10 speciesP. aeruginosamost common

Pseudomonas /Pathogenesis & immunityMultiple virulence factorsStructural components:Toxins & enzymespyocyaninAntibiotic resistance

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

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

Pseudomonas /diagnosis & identificationCultureSimpleIdentificationColonial morphology colony size, hemolysis, pigmentation, odorBiochemical testsPositive oxidase test

Pseudomonas /diagnosis & identificationCulture:beta hemolysis, green pigment, grapelike odorand simple biochemical tests (e.g., positive oxidase reaction; oxidative utilization of carbohydrates)

Pseudomonas /Combined use of effective antibiotics (e.g., aminoglycoside and -lactam antibiotics) frequently required; monotherapy is generally ineffective and can select for resistant strains

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

Pseudomonas /

P. aeruginosa also produces a number of different -lactamases that can inactivate many -lactam antibiotics (e.g., penicillins, cephalosporins, and carbapenems).

P.aeruginosa

Burn wound infected with Pseudomonas

P.aeruginosa

Burkholderia(Formerly classified as Pseudomonas)B. cepacia, B. pseudomalleiImportant human pathogens

Burkholderia cepaciaLike P. aeruginosais commonly associated with nosocomial infectionsrelatively low level of virulence, rarely cause deathis susceptible to trimetoprim-sulfamethoxazole

Burkholderia pseudomalleifound in soil, water, vegetationopportunisticmelioidosishighly infectious , careful isolation

Stenotrophomonas maltophiliamy favorite (the person or animal most people expect to win a race or competition) bacteria

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

Acinetobacter

oxidase-negativegram-negative coccobacilli

AcinetobacterA. baumannii, A. lwoffii, A. haemolyticusare recovered in nature & hospitalsurvive on moist and dry surfaces (!skin!)resistant to antibiotics (carbepenems)!!!!!!!!!

Acinetobacter

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Moraxella

MoraxellaM.catarrhalisAn important pathogenStrict aerobicOxidase positiveGram negative diplococci

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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