Non-Fermenting GNR PDF

Non-Fermenting GNR RAQUEL M. FERNANDEZ, RMT, MSPH General Characteristics Prefer wet environments such as sinks, respiratory equipment, flower vases Usually not part of healthy human microbiota Considered opportunistic and can colonize and infect immunocompromised individuals Often fo...

Non-Fermenting GNR RAQUEL M. FERNANDEZ, RMT, MSPH General Characteristics Prefer wet environments such as sinks, respiratory equipment, flower vases Usually not part of healthy human microbiota Considered opportunistic and can colonize and infect immunocompromised individuals Often found as transient or colonizing microbiota of hospitalized individuals and can become nosocomial pathogens General Characteristics Aerobic, gram negative rods Do not use carbohydrates as a source of energy or degrade them through metabolic pathways other than fermentation Most are obligate aerobes and grow poorly if at all under anaerobic conditions Oxidizers and non-fermenters Asaccharolytic, do not degrade carbohydrate at all Usually display abundant growth on sheep BAP and CAP within 24- 48h Clues that suggest the isolation of a NF The organism does not ferment carbohydrates Alkaline slant/No change deep butt reaction in TSI and KIA Require oxygen for the metabolism of carbohydrates if they are able to use them at all They fail to ferment carbohydrates Clues that suggest the isolation of a NF NF can be oxidase positive May fail to grow or show poor growth on McConkey agar Some have fruity, sweet or unique odors They may display unique colony morphologies and pigmentation Often MDR Biochemical tests for ID Hugh-Leifson OF medium Pigments Oxidase Colony morphologies Decarboxylation of amino acids Distinct odors Motility Nitrate reduction Acetamide Growth at 42°C Characteristic of Pseudomonas Gram-negative bacilli belonging to Pseudomonadaceae Motile by means of a single polar flagellum. Non spore forming Capsulated "Polysaccharide capsule" Aerobic Breakdown glucose by oxidation i.e. Oxidative Oxidase and catalase positive Characteristic of Pseudomonas It has very simple nutritional requirements i.e. non fastidious The most important pathogenic organism is Ps. aeruginosa Optimum temperature is 37 C, and it is able to grow at 42 C It is resistant to high concentrations of salts, dyes, weak antiseptics, and many antibiotics Common inhabitants of soil, water, GIT Ps. Fluorescens, putida and stutzeri Pseudomonas aeruginosa GNR that may be encapsulated Most strains are motile by means of single polar flagellum Common inhabitant of the environment such as soil, water and plants Survives well in wet environments Metabolism is oxidative and requires the presence of oxygen Pseudomonas aeruginosa Will grow in the absence of oxygen if nitrate is available as a respiratory electron acceptor Rarely part of human microbiota Opportunistic pathogen Often beta-hemolytic, with rough spreading flat colonies with a ground glass consistency with serrated or jagged edges Pseudomonas aeruginosa Colonies often display metallic sheen and blue-green pigment Pigmentation can also be red or brown Often beta-hemolytic with a sweet fruity odor (grape-like or taco-shell like) Colonies can be of 2 types: large and smooth with flat edges and an elevated appearance and the other mucoid appearance Pseudomonas aeruginosa mucoid colony consistency is attributed to the production of alginate slime Pigments: pyoverdin or fluorescein that is yellow and seen only as fluorescence under a UV light; pyocyanin, a blue pigment produced abundantly in media of low iron content When combined the 2 pigments produce the characteristic blue- green pigment often seen in cultures Pseudomonas aeruginosa ID grows well on most lab media oxidizes glu, fruc, xyl but not lac or suc deaminates acetamide grows at 42°C reduces nitrate decarboxylates arginine Pseudomonas aeruginosa requires a break in the body’s Infection consists of 3 stages: defenses for an infection to Bacterial attachment and begin colonization Local invasion Has a natural resistance to many antibiotics produced by bacteria Dissemination by means of blood and systemic disease and fungi Most often found in hospitalized It is invasive and toxigenic individuals Pseudomonas aeruginosa the ability to invade tissue is usually due to toxins and enzymes that break down physical barriers, damage host cells and help the organism evade host defenses Extracellular protease: elastase and alkaline protease Produces cytotoxins and hemolysins such as phospholipase and lecithinase The blue pigment appears to impair the ability of the upper respiratory cilia to sweep out mucous and debris Kills the cells of lung epithelium by preventing catalase activity within the cell It causes apoptosis of WBCs. Pseudomonas aeruginosa Other virulence factors: LPS or endotoxin, Exoenzyme S, Exotoxin A Pseudomonas is involved in respiratory infections, prevalent in ICU patients on ventilators and receiving long-term therapy with broad spectrum antibiotics Individuals with cystic fibrosis are often colonized by a unique mucoid strain that is difficult to eradicate Associated with bacteremia and septicemia Causes endocarditis in intravenous drug users and those with prosthetic heart valves Pseudomonas aeruginosa Well known cause of swimmer’s ear Major cause of bacterial keratitis often due to extended contact wear or poor contact lens hygiene Prefers cartilages and joints of the bones of the skull and trunk causing chronic osteomyelitis UTI caused by catheterization, instrumentation or surgery can produce disease in the GIT in immunocompromised and necrotizing enterocolitis in infants Produces skin and soft tissue infections (burn wound, pyoderma and dermatitis, folliculitis) Prevention and Treatment Observation of proper isolation procedures, aseptic techniques and careful cleaning and monitoring of respirators, catheters and other instruments Treatment with anti-pseudomonal beta-lactam, fluoroquinolones and aminoglycosides, carbapenem (imipenem) Current standard is combination of anti-pseudomonal beta-lactam and aminoglycoside Pseudomonas fluorescens and P. putida Often described together Motile, aerobic, oxi + GNB Produces pyoverdin or fluorescein but not pyocyanin P. fluorescens Is an environmental organism found in soil, water, plants, and contaminated food such as milk Rarely isolated from clinical specimens bec they grow poorly at 35°C Optimum growth temp: 25-30°C Motile, oxi+ Same typical colonies on BAP, wet and gray. NLF on McConkey Can grow at 4°C and hydrolyze gelatin Biochemical Differentiation fluorescent Pseudomonad group Test P. aeruginosa P. fluorescens P. putida Pyocyanin production + - - Pyoverdin production + + + Growth at 42°C + - - Acetamide + - - deamination Gelatin hydrolysis + + - Nitrate reduction + - - P. putida Also an environmental organism found in soil and water Known for its ability for bioremediation such as breakdown of oil and toluene Has been isolated from lizards, insects, and mammals Optimum temp. for growth: 25°C, NLF on Mc Motile, oxi +, fails to grow at 42°C Pseudomonas stutzeri Non-fluorescent GNB that is widely distributed in the environment Rare opportunistic pathogen best known as a soil denitrifier Often recognized by its unusual colony on BAP: adherent, wrinkled or leathery, hard and dry with either a yellow or brown pigment It is difficult to mix into suspension, colonies resemble B. pseudomallei, NLF on Mc Can grow at temp. 4-45°C; optimum 35°C Motile, oxi+, no pigment is produced Pseudomonas stutzeri Arginine decarboxylase negative Oxidizes maltose and hydrolyze starch Has been associated with bacteremia and septicemia, bone infection, endocarditis, eye infection, meningitis, skin infections and UTIs Demonstrates at least 2 antibiotic resistance mechanisms: alteration of OM proteins and LPS profiles and presence of beta-lactamases Treatment include the use of aminoglycosides, tmp-sxt, Te, fluoroquinolones and third gen Ceph. Acinetobacter Member of the family Moraxellaceae Consists of 25 DNA homology groups, 11 species have been officially named A. baumanii , A. iwoffi and A. haemolyticus Ubiquitous in the environment, in soil, water and foodstuffs, in the hospital environment Associated with ventilators, humidifiers, catheters and other devices About 25% of adults carry the organisms on the skin, 7% carry the organisms in their pharynx Acinetobacter Hospitalized patients may become easily colonized Opportunistic pathogens, second to P. aeruginosa in isolation frequency A. baumanii have been associated with UTI, pneumonia, tracheobronchitis, or both, endocarditis, septicemia, meningitis, cellulitis, trauma, burns, introduction of foreign body A. baumanii has been reported in eye infections A. iwoffi is much less virulent and when isolated indicates contamination or colonization rather than infection Identifying Characteristics Strictly aerobic, gram negative coccobacilli Oxidase negative, catalase +, non-motile Can appear as gram positive cocci in smears made from blood cultures The purplish hue produced on McConkey may resemble a lactose fermenting bacterium pH 5.5 -6.0, temperature 30-35°C are preferred A. baumanii is saccharolytic, A. iwoffi is assaccharolytic Identifying Characteristics Produces a K/NC reaction Majority of beta-hemolytic organisms are called Acinetobacter haemolyticus Clinical Significance Able to form biofilms on inanimate objects Presence of pili allows the organisms to adhere to epithelial cells Once it adheres, it is able to create proteins that can cause cell death It possesses LPS as part of its cell wall Tends to be resistant to disinfectants Can survive in moist and dry surfaces Best known for its multi-drug resistance Clinical Significance Has the ability to acquire resistance to many major classes of antibiotics including newer beta-lactams The presence of resistance plasmids is a significant virulence feature A. baumanii has been named “gram negative MRSA” The digestive tract, skin surface and mucous membranes of patients in ICU are reservoir sites for this organism Transmission occurs due to contact from hands of healthcare workers or from environmental reservoirs A. baumanii infections outside the hospital are very rare Prevention and Treatment Standard and Contact precautions Careful use of antibiotics Treatment should be based on susceptibility test results Most A. baumanii is susceptible to the carbapenems (Imipenem and Meropenem) Piperacillin-Tazobactam, most third generation Cephalosphorins, aminoglycosides Colistin is one of the few antimicrobials that can be used on MDR strains but is potentially nephrotoxic and neurotoxic Tigecyline, a tetracycline is a promising agent Stenotrophomonas maltophilia A motile, gram negative, oxi – rod Found in soil, plants and water as well as a nosocomial pathogen Orginally included in the Pseudomonas, then Xanthomonas, now it is the only species in the genus Stenotrophomonas Identifying Characteristics Appears as non-distinct, straight or slightly curved rod in singles or pairs BAP colonies are non-hemolytic, large, smooth and shiny, can be gray-white but may have a slightly yellow pigment with a distinctive ammonia- like odor when the agar plate lid is initially removed Colonies may exhibit a lavender-green discoloration of the agar in areas of heavy growth NLF, may exhibit a brownish discoloration of McConkey agar Identifying Characteristics Oxidase negative Strong rapid oxidation of maltose Weaker oxidation of glucose Lysine decarboxylase + DNAse + TSI: K/NC Clinical Significance Important nosocomial pathogen in debilitated and immunosuppressed individuals Produces proteases and elastases, and has LPS being a GNB a part of its cell wall Difficult to distinguish between colonization and infection Its presence is a marker that the patient is deteriorating Commonly present in medical devices such as IV/CV and urinary catheters Pneumonia is the most common infection Clinical Significance Cystic fibrosis patients can be colonized with S. maltophilia in addition to other fermenters Its presence in urine is usually due to colonization of the urinary catheter or manipulation of the urinary tract It can be isolated in wounds. Unless there is a presence of WBCs in the form of a pus, it may only be a colonizer Prevention and Treatment Standard and Contact precaution S. maltophilia is intrinsically resistant to many antibiotics due to production of beta-lactamases and carbapenemases, plasmids, alteration of OM proteins and an efflux mechanisms It is well known for developing resistance to new antibiotics quickly Susceptible to TMP-SXT, Colistin and Polymyxin B Therapy usually requires a rifampin plus a fluoroquinolone or a beta- lactam Broth dilution is the method recommended for susceptibility tests Burkholderia cepacia Complex A complex of 9 subspecies not usually differentiated Very significant motile GNB often associate with a specific patient population esp. patients with cystic fibrosis Formerly Pseudomonas Inhabits soil and water, not part of normal human microbiota Well known as a plant pathogen but not as nosocomial pathogen and does not cause harm to healthy individuals Can be found in the hospital environment, tap water, disinfectants, soaps and lotions Identifying Characeristics Able to grow on sheep’s BAP, CAP and McConkey NLF but after 4-7days, they may become dark pink or red due to oxidation of lactose BCSA selects and differentiates the organism based on the presence of CV, polymyxin B, Gm and Va. OFPBL is also selective and differential. Colonies are yellow due to oxidation of lactose Burkholderia cepacia Commercial ID system may have difficulty in identifying B. cepacia Molecular methods are now recommended Weakly Oxi + TSI: K/NC Able to decarboxylate lysine Able to oxidize glu, maltose and lactose Burkholderia cepacia B. cepacia is able to oxidize mannitol while S. maltophilia is DNAse positive The negative arginine reaction of B. cepacia will differentiate it from B. pseudomallei and B. gladioli is unable to oxidize maltose and lactose Clinical Significance Extremely pathogenic for those with cystic fibrosis Possesses few virulence factors LPS and ability to adhere to mucin, resistance to multiple antibiotics Studies show the presence of B. cepacia prior to lung transplant often results in death after transplantation Treatment and Prevention Requires isolation of patient when hospitalized Antibiotic therapy rarely eradicates the organism from the CF respiratory tract Resistant to aminoglycosides Multiple antibiotics are necessary for treatment like Minocycline, Meropenem, Ceftazidime, Fluoroquinolones, Chloramphenicol It is susceptible to TMP-SXT Burkholderia pseudomallei Oxi +, motile, aerobic GNB that is straight or slightly curved Grows on standard lab media at 35°C in a CO2 atmosphere Has a smooth and mucoid colony or a dry wrinkled colony similar to P. stutzeri on BAP A characteristic musty or earthy odor Burkholderia pseudomallei Colonies appear pink on Mc due to oxidation of lactose Decarboxylates arginine whereas P. stutzeri, B. cepacia and B. gladioli is negative Organism is resistant to colistin and Polymyxin B Motile, GNB found in soil and water Burkholderia pseudomallei Associated with rice paddy surface waters It can be transmitted person to person via aerosols Causes melioidosis Known as “Vietnamese time bomb” The organism can survive in phagocytes and can reactivate decades after the initial infection when individuals become immunocompromised Reactivation often appears as multiple abscesses throughout the body and skin Alcaligenes faecalis Inhabits the environment and not part of human microbiota Can be found in hospital environment such as respiratory equipment and disinfectants Oxi+, motile, GNB produces a thin, spreading colony with irregular edges on sheep’s BAP It can produce a green discoloration of the agar It smells green apple, NLF on McConkey Assaccharolytic, tends to create a strong alkaline reaction on OF medium which appears as a blue color Alcaligenes faecalis reduces nitrate to nitrite Can cause opportunistic infections in immunocompromised individuals and those with underlying disease Has the ability to colonize cystic fibrosis patient who are intubated Achromobacter xylosoxidans Aerobic, motile, oxi+, NLF GNB Found in moist environments It can oxidize glucose and xylose Opportunistic pathogen capable of causing bacteremia, meningitis, pneumonia and peritonitis Capable of colonizing the respiratory tract of persons with CF, medical equipment and solutions Elizabethkingia meningoseptica (Chryseobacterium meningosepticum) Formerly Flavobacterium meningosepticum Found in soil, plants, water, food and hospital water sources including incubators, sinks, faucets, saline solutions and respiratory equipment Not part of normal human flora Can survive in chlorinated water It is an oxi+, non-motile, slightly filamentous or thread-like GNB Elizabethkingia meningoseptica (Chryseobacterium meningosepticum) BAP colonies are circular, smooth, and glistening with a light yellow pigment May not grow well on McConkey Positive indole using an Ehrlich’s reagent Often associated with meningitis and bacteremia in premature infants Also implicated in pneumonia, cellulitis and abscesses in immunocompromised patients