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78 Cards in this Set
- Front
- Back
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Fermentative GNR Genera
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Vibrio
Aeromonas Plesiomonas |
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Vibrio cholerae general characteristics
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0:1 and non-0:1
Intestinal infection Rice-water stool Contaminated food and water |
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Vibrio parahaemolyticus general characteristics
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Severe cramping and watery Diarrhea
Ingestion of raw shellfish, especially oysters |
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Vibrio vulnificus general characteristics
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Wound and GI infections
Bacteremia Ingestion of contaminated food |
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Vibrio alginolyticus general characteristics
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Least pathogenic for humans and most infrequently isolated
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Vibrio Habitat and Transmission
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Can be isolated from numerous sources. Good medical hx imperative. Good indicators: recent consumption of raw seafood (oysters), recent immigration or foreign travel, gastroenteritis w/rice-water stool, accidental trauma w/fresh or marine water or its products
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Vibrio Microscopic Morphology
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Asporogenous
Gram negative rods Polar sheathed flagella in broth Peritrichous, unsheathed flagella on solid media Highly pleomorphic (often "curved) |
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Vibrio physiology
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Facultative anaerobes
Oxidase positive Most reduce nitrate Most halophilic (not cholera or mimicus) Positive string test Susceptible to O/129 |
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Vibrio cholerae epidemiology
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V. cholerae 01 is causative agent of cholera, a disease of major public health significance. Most epidemics occur in developing countries. Prevalent in Bengal region of India and Bangladesh.
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Epidemic Cholera
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Caused by V. cholerae and V. cholerae El Tor. Portal entry is mouth. Incubates 8-48 hrs. Resides in small intestine and produces cholera toxin. Symptoms are severe, explosive, watery diarrhea leading to dehydration and electrolyte loss. Called "rice water stools."
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Clinical Manifestations of Cholera
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Acute diarrheal illness
Spread via contaminated water -improperly preserved and handled foods have caused outbreaks Acute case of severe gastroenteritis accompanied by vomiting then diarrhea Stools described as rice-water, 10-30/day Rapid fluid and electolyte loss leading to dehydration, hypovolemic shock, metabolic acidosis and death in hours |
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Treatment of Cholerae
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Administration of copious amounts of intravenous or oral fluids
Antimicrobial agents can shorten duration of diarrhea |
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Vibrio parahaemolyticus epidemiology
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2nd most commen Vibrio spp implicated in gastroenteritis
1st recongnized in 1950 by causing a large food-borne outbreak in Japan Serotype 03:K6 is most common Mostly found in aquatic env Halophilic Usually traced to recent consumption of raw, improperly cooked, or re-contaminated seafood Assoc w/at least 30 difft marine animal spp; oysters, clams, crabs, lobsters, scallops, sardines & shrimp |
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Clinical Manifestations of Vibrio parahaemolyticus
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Self-limited GI disease
Watery diarrhea, moderate cramps or vomiting, little or no fever 24-48 hr incubation Occ from wounds, ear/eye infections or pneumonia |
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Vibrio alginolyticus epidemiology
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Marine environments on Atlantic, Gulf and Pacific coasts of North America
2nd most serious Vibrio-associated infection Primary septicemia: GI illness after eating shellfish, pts w/liver disease are @ high risk Wound infections: hx of traumatic aquatic wound that usually presents as cellulitis |
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Vibrio alginolyticus epidemiology continued
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Least pathogenic Vibrio spp for humans
Common marine env inhabitant Strict halophile-requires at least 1% NaCl, can tolerate up to 10% NaCl Usually from eye/ear or burn infections, or wounds May be an occupational hazard for people in contact w/seawater like fishermen and sailors |
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Vibrionaceae Specimen Collection
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Vibrios are not fastidious
Swabs are acceptable if transported in Cairy-Blair to prevent desiccation Glycerol is toxic to Vibrios |
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Vibrionaceae Culture Media
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Salt concentration of commonly used media is sufficient to support growth of Vibrios
On SBA or CHOC: med-large smooth, opaque, greenish, irridescent colonies, some w/alpha or beta hemolysis On MacConkey: most are non-lactose fermenters, but vulnificus is lactose pos |
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Selective media for Vibrionaceae
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TCBS agar: thiosulfate citrate bile salts sucrose agar
Most widely used for suspected Vibrio Differentiates sucrose fermenting spp (yellow) such as cholerae, alginolyticus and other less common spp TCBS generally will inhibit most other organisms |
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Presumptive Identification of Vibrionaceae
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Susceptible to O/129
Cannot ferment inositol Oxidase positive Fermenter (vs Pseudomonas) |
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Definitive Identification of Vibrionaceae
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Biochem tests ID to spp level
8 tests divide 12 clinically significant spp into 6 groups Additional testing to ID 4 major clinical Vibrio spp |
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Aeromonas in general
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Ubiquitous
Oxidase postive Glucose fermenting Wide distribution in freshwater and marine environments worldwide Responsible for a diverse spectrum of disease among various animals such as fish, reptiles, amphibians, mammals and humans |
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Aeromonas general characteristics
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Gram negative rod
Motile via single polar flagellum All grow at 4C-42C Manifests as intestinal or extraintestinal infections |
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Intestinal Aeromonas Infections
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Enteric pathogens
Infection often involves aquatic exposure (untreated ground water, seafood consumption-esp raw oysters or clams) Infections have been linked to fresh produce and dairy products |
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Diarrheal Presentations of Aeromonas
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Acute, secretory diarrhea often accompanied by vomiting
Acute, dysenteric diarrhea Chronic diarrhea- 10+ days Rice-water stools |
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Intestinal Aeromonas
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Most cases are self-limiting
Pediatric and geriatric pts may require supportive therapy and antimicrobials A. caviae is most frequently assoc w/GI infections A.hydrophilia and A. veronii are associated w/complications such as HUS or kidney disease |
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Extraintestinal Aeromonas
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Septicemia and wounds most common
Also implicated in osteomyelitis, meningitis, cystitis, endocarditis and peritonitis Wound infections usually involve recent traumatic aquatic exposure Most wounds caused by A. hydrophilia |
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Culture Media for Aeromonads
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Grow on most media
Large, round, raised opaque colonies w/mucoid surface Pigmentation ranges from clear to white to buff colored Hemolysis is variable on SBA, most are beta-hemolytic Many ferment lactose A modified CIN plate yields high recovery of Aeromonas, it appears pink on CIN |
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Presumptive ID of Aeromonas
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Positive oxidase test distinguishes Aeromonas from Enterobacteriaceae
Most clinically isolated Aeromonads are indole positive Aeromonads are resistant to O/129 which distinguishes them from Vibrio The ability to ferment lucose distinguishes Aeromonas from Pseudomonas |
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Definitive ID of Aeromonas
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Accomplished biochemically and with antimicrobial markers via the Aerokey II
Antimicrobial Susceptibility -Most GI cases are self limited but wound infections and septicemia are always treated Aeromonads are resistant to penicillin, ampicillin and carbenecillin Generally susceptible to trimethoprimsulfamethoxazole, aminoglycosides and quinolones |
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Plesiomonas general characteristics
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Formerly in the Vibrionaceae family
Oxidase positive Glucose fermenting Facultative anaerobe Motile by polar flagella P. shigelloides is only species Gram negative rods arranged singly, in pairs or short chains or filamentous forms No spores or capsules Plesiomonas and Shigella share biochemical and antigenic features Plesiomonas can cross react with Shigella agglutination tests |
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Plesiomonas Epidemiology
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Found in soil and aquatic environments
Generally only found in fresh waters of tropical and subtropical climates Widely distributed among animals; dogs, cats, pigs, vultures, snakes, lizards, fish |
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Clinical Manifestations of Plesiomonas
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Gastroenteritis
Ingestion of contaminated water or food Symptoms: 25% to 40% present with fever and/or vomiting, abdominal pain Three major clinical types of gastroenteritis are watery or secretory diarrhea, subacute or chronic disease lasting 14 days to 2-3 months and invasive, dysenteric form resembling colitis Extraintestinal: an occupational exposure for veterinarians, fish handlers and water sport participants |
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Culture Media for Plesiomonas
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Grows on most media
Shiny, opaque, non-hemolytic colonies w/slightly raised center and smooth edge Ferments lactose Some strains are inhibited by EMB or MAC agars Inositol brilliant green bile salts agar enhances isolation of plesiomonads, they appear white to pink compared to coliforms which are green or pink |
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Identification of Plesiomonads
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P. shigelloides can be differentiated from similar genera with several key tests
Positive oxidase, distinguishes it from Enterobacteriaceae Sensitivity to O/129 separates it from Aeromonas Ability to ferment inositol differentiates it from Aeromonas and most Vibrio spp |
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Non-fermenting and Miscellaneous GNR
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Pseudomonads
Acinetobacter spp. Stenotrophomonas maltophilia Oxidase negtive oxidizers Asaccharolytic species |
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General Characteristics of Non-fermenting and Miscellaneous GNR
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Non-fermenting GNR fail to acidify oxidative-fermentative media overlaid with mineral oil or TSIA butts
Prefer aerobic environments Most are oxidase positive Two major groups: Oxidizers which oxidize carbohydrates to derive energy for metabolism and Non-oxidizers or asaccharolytic which do not break down carbohydrates at all and are biochemically inactive (inert) |
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Oxidation vs fermentation
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Bacteria utilize glucose and other carbohydrates using
certain metabolic pathways Some bacteria use oxidative routes, but others involve fermentation reaction Oxidative organisms can only metabolize glucose or other carbohydrates under aerobic conditions where oxygen is the ultimate hydrogen acceptor Fermentative organisms ferment glucose and the hydrogen acceptor is then another substance, such as sulphur This fermentative process is independent of oxygen and cultures of organisms may be aerobic or anaerobic The end product of metabolizing a carbohydrate is acid |
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O-F Media
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O-F media is sometimes referred to as the Hugh and Leifson test
O-F is a semi-solid medium in tubes, containing the carbohydrate (usually glucose) and a pH indicator Two tubes are inoculated and one tube is immediately sealed (overlaid with mineral oil) to produce anaerobic conditions Oxidizing organisms produce an acid reaction in the open tube only Fermenting organisms produce an acid reaction throughout the medium in both tubes Organisms that can not break down the carbohydrate aerobically or anaerobically produce an alkaline reaction in the open tube and no change in the covered tube |
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Habitat and transmission of Non-fermenting and Miscellaneous GNR
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Most NF-GNR are ubiquitous in most environments such as soil, water, on plants, and decaying vegetation
Prefer moist environments In hospitals they are commonly isolated from nebulizers, dialysate fluids, saline and catheters Can withstand disinfection, tend to resist antimicrobial agents Rarely part of normal flora, but will colonize opportunistically Common causes of nosocomial infections |
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Clinical Infections of Non-fermenting Miscellaneous GNR
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NF account for 15% of all GNR isolated from clinical specimens
Responsible for wide range of infections -Septicemia, meningitis, osteomyelitis, wound infections following trauma or surgery Common risk factors -Immunosuppression, foreign body implantation, trauma, fluid introduction Most infections occur in hospital patient or recently hospitalized patients |
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Biochemical Characteristics of Non-fermenting Miscellaneous GNR
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Fail to ferment carbohydrates
-Will not yield acid reaction in TSIA or Kligers iron agar (KIA)(K/K or K/NR) Classification systems exist for NF bacteria NF most commonly seen in clinical lab are: -Pseudomonas aeruginosa -Acinetobacter spp. -Stenotrophomonas maltophilia |
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Pseudomonads
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Largest percentage of all NF in clinical setting
Common characteristics: -GNR or coccobacillus -Motile except Burkholderia mallei -Oxidase and Catalase positive -Most will grow on MAC -Usually oxidizer of carbohydrates but some are asaccharolytic |
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Pseudomonas Fluorescent Group
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Pseudomonas aeruginosa
-Most clinically isolated species, not usually normal flora, accounts for 5 – 15% of all nosocomial infections P. fluorescens and P. putida - Low virulence, rarely causes clinical disease, have been isolated from respiratory specimens, contaminated blood products, urine, cosmetics, and hospital equipment, can grow at 4°C, produce pyoverdin but not pyocyanin |
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Pseudomonas aeruginosa
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Leading cause of nosocomial respiratory tract infections
Cause of many different diseases -Bacteriemia, wound infection, pulmonary disease (esp in CF patients), UTI’s, endocarditis, infection following trauma or burns and rarely meningitis |
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P. aeruginosa Virulence Factors
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Endotoxin
Motility Pili Inherently resistant to numerous antimicrobials Capsule: mucoid colonies isolated from respiratory tract of CF patients due to overproduction of alginate Exotoxins: proteases, hemolysins, lecithinase, elastase and DNase, exotoxin A – similar to diphtheria toxin, it blocks protein synthesis |
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Identifying characteristics of Pseudomonas aeruginosa
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Produce pigments:
*Pyoverdin: yellow-green or yellow-brown *Pyocyanin: blue Pyorubin: red Pyomelanin: brown or black Usually green in color due to combination of both * pigments Beta hemolytic on SBA Flat spreading colonies with metallic sheen Produce sweet, grapelike odor Growth at 42°C Citrate Positive Cetrimide agar – selective and differential, it inhibits most bacteria and enhances pigment production |
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Treatment of Pseudomonas
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Innately resistant to many antibiotics
Usually susceptible to aminoglycosides, 3rd and 4th generation cephalosporins, ceftazidime and cefepine, carbapenems and fluoroquinolones Resistance to any antibiotic may develop during therapy Resistance higher in nosocomial strains Treatment usually requires combination therapy |
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Pseudomonas Non-fluorescent Group
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P. stutzeri
-Rarely isolated in clinical setting -Wrinkled, leathery adherent colonies with light-yellow to brown pigment P. mendocina -Found in soil and water -May be a contaminant in clinical specimens P. pseudoalcaligenes and P. alcaligenes -Considered contaminants -Oxidase positive and biochemically inactive |
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Acinetobacter
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Member of the Moraxellaceae family
Most common species are A. baumannii and A. lwoffii -Ubiquitous in soil, water, foodstuffs - Associated with nosocomial infections via ventilators, humidifiers, and catheters - 25% adults carry the organism on skin and 7% in pharynx - Hospitalized patients easily become colonized - Often considered contaminants when isolated from urine, feces and vaginal secretions |
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Acinetobacter Infections
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Opportunistic bacteria
- 1% - 3% of all nosocomial infections - Second most frequently isolated NF-GNR after Pseudomonas aeruginosa A. baumanii: -UTIs, pneumonia, tracheobronchitis, endocartiditis, septicemia, meningitis, cellulitis, infection after trauma or burns, eye infections (endeophthalmitis, conjunctivitis and corneal ulceration) A. lwofii: - less virulent and usually a contaminant |
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Acinetobacter ID
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Coccobacilli
Oxidase NEGATIVE Catalase positive NON-motile Look like gram-pos cocci in smears from blood culture bottles Growth on most lab media, including MAC A. baumannii: -saccharolytic -Highly resistant to antimicrobials A. lwoffii: - Asaccharolytic - More susceptible to antimicrobials |
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Stenotrophomonas maltophilia
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Third most common NF-GNR Ubiquitous in environment
- Common in hospitals -Contaminants of blood-drawing equipment, disinfectants, transducers - Not part of normal flora but can colonize respiratory tract of hospitalized patients - Resistant to ephalosporins, penicillins, carbapenems, and aminoglycosides - Diseases include endocarditis (IVDU or heart surgery), wound infections, bacteremia, and rarely UTI's and meningitis - Isolated from 6.4% to 10% of CF patients |
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Stenotrophomonas ID
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Oxidase NEGATIVE
Positive: -Catalase -Esculin -DNase -Gelatin hydrolysis Susceptible to SXT |
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Burkholderia
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B. cepacia
- Complex of nine genomovars - Low-grade nosocomial pathogen most often associated with pneumonia in CF patinets - 3% of CF population infected B. gladioli - Plant pathogen that resembles B. cepacia B. mallei - Causes Glanders disease - Zoonotic infection of livestock (horses, mules and donkeys) - Potential bioterror agnet B. pseudomallei - Causes Melioidosis - Bioterror agent |
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Burkholderia cepacia
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Causes endocarditis (IVDU), pneumonitis, UTIs, osteomyelitis, dermatitis, wound infections
Isolated from irrigation fluids, anesthetics, nebulizers, detergents, and disinfectants Grows on most lab media, including MAC - Lose viability on SBA in 3 – 4 days Produces a weak, slow positive oxidase reaction Oxidizes glucose Motile May produce a nonfluorescing yellow or green pigment that may diffuse into media Non-wrinkled colonies Antibiotic resistance develops rapidly |
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Burkholderia pseudomallei
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Melioidosis is an aggressive granulomatous pulmonary disease
Ingestion, inhalation or inoculation of the organism Metastatic abscess formation in lungs Overwhelming septicemia Pneumonia is most common presentation Local infections such as orbital cellulitis and draining abscesses may occur Prolonged incubation period Endemic regions – Southeast Asia, Northern Australia and Mexico Found in water and muddy soil Non-fermentative Wrinkled colonies Bipolar staining on gram-stained smears Utilizes lactose Earthy odor – NO PLATE SNIFFING Work MUST be done in biosafety cabinet |
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Flavobacterium and Chryseobacterium
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Flavobacteriaceae family
Ubiquitous in soil and water Not part of human normal flora Usually associated with nosocomial infections Weakly fermentative - delayed reaction and will initially appear as non-fermenter Most disease caused by C. meningosepticum Meningitis or septicemia in pre-mature newborns Non-motile Yellow intracellular pigment Lavender green discoloration on blood-containing media Positive for DNase, oxidase, gelatin hydrolysis, weak indole |
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Moraxella and Oligella
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Strongly Oxidase Positive
Non-motile Coccobacilli to bacilli Biochemically inert Strictly aerobic Opportunists that reside on mucous membranes Commonly susceptible to penicillin Unlike most non-fermenting GNR |
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Moraxella spp.
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M. catarrhalis
-Frequently isolated from respiratory and ear -Closely resembles Neisseria M. nonliquefaciens - Most commonly isolated -Resides as normal flora in respiratory tract -Does not grow on MAC M. lacunata - Conjunctival isolate M. osloensis - Normal flora of genitourinary tract M. atlantaie - Can grow on MAC |
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Oligella spp.
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O. urethralis and O. urealytica
Small, paired GNR or coccobacilli Most isolated from urinary tract Non-oxidative Do not grow on MAC |
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Shewanella
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S. putrefaciens and S. algae Rarely pathogenic
-Obtained from abscesses and traumatic ulcers Usually colonizers Produce profuse H2S on TSIA S. algae is halophilic Oxidase positive |
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Less Common NF-GNR
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Alcaligenes
Achromobacter Balneatrix Brevundimonas CDC Groups EO-2, 3, 4 Psychrobacter Chromobacterium Chryseomonas Flavimonas Comamonas Groups EF-4a and 4b Methylobacterium Roseomonas Ochrobactrum Ralstonia Rhizobium Sphingobacterium Sphingomonas |
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NF-GNR Summary
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All NF-GNR fail to ferment carbohydrates
Most often found in the environment Prefer aerobic environments Most are opportunist that cause nosocomial infections in immunocompromised patients Of all GNR isolated in clinical setting, 30% will be non-fermenters Most commonly isolated organisms: -Pseudomonas aeruginosa, Acinetobacter baumanii, Stenotrophomonas maltophilia Although less likely to cause disease than fermentative GNR, they are highly resistant to antimicrobials – difficult to treat |
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Miscellaneous GNR
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Campylobacter and Helicobacter
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General Features of Miscellaneous GNR
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Asacchroloytic Microaerophilic and capnophilic
-Require oxygen but at lower concentrations -Ideal atmospheric environment contains mixture of 5% – 10% O2 and 10% CO2 |
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Campylobacter spp.
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Associated with human disease:
-C. fetus -C. jejuni -C. coli -C. sputorum -C. comcosis -C. curvus -C. rectus |
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Epidemiology of Campylobacter
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More recently established as human pathogen
Known to cause abortion in animals; cows, sheep, swine Transmission: directly via contact by exposure to infected animals or indirectly by consumption of contaminated water, dairy products and improperly cooked poultry -Person to person transmission can also occur Most often causes disease in children < 1 year old and adults between 20 – 40 years of age This is the age group when people are most likely to ingest undercooked food and after this age they probably have been exposed and gained resistance to disease |
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Campylobacter jejuni
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Leading causes of gastroenteritis
worldwide Diarrheal disease that begins with mild abdominal pain within 2 – 10 days after ingestion of contaminated product, followed by cramps and bloody diarrhea and possible fever and chills (rare vomiting) Usually self-limiting (2-6 days) Untreated patients can carry the organism for several months (like typhoid) |
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Campylobacter fetus
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Isolated most frequently from blood cultures
Rarely associated with GI disease Disease associated with immunocompromised and elderly |
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Laboratory Diagnosis of Campylobacter
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C. fetus may be recovered in blood culture media
C. jejuni isolated from stool -Cairy-Blair transport medium of stool Oxidase positive Motile Microscopic appearance C. jejuni is positive for hippurate hydrolysis |
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Culture Media for Campylobacter
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Enriched, Selective media
CAMPY-BAP most common -Brucella agar base, 10% sheep RBC and antibiotics CAMPY-CVA has better suppression of normal fecal flora |
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Incubation of Campylobacter
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Any suspected Campy specimen is incubated at 42°C
-C. jejuni optimally grows at this temperature -Colon organisms are inhibited C. fetus will not grow at 42°C, must be incubated at 35-37°C Campy pak used to get ideal environment |
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Campy colony morphology
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C. jejuni are moist, “runny looking” and spreading and are usually non-hemolytic
C. fetus produces smooth, convex,translucent colonies that are tan or slightly pink coloration may be observed |
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Microscopic Morphology of Campy
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Campylobacter spp. are curved, GNR
Non-spore forming May appear as long spirals, S-shapes or seagull wing shapes from enteric specimens Stains poorly -Carbolfuchsin recommended as counterstain -If safranin is used, it should be stained 2 – 3 minutes Darting motility using visualized hanging drop technique |
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Helicobacter spp
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H. pylori
H. cinaedi H. fennelliae H. canadensis H. canis H. pullorum H. winghamensis |
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Helicobacter pylori
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Primarily linked to gastric infections
Once acquired, can colonize stomach for a long time causing a low-grade inflammatory process Does not invade gastric epithelium, but initiates host antibody response -Antibodies are not protective Major cause of type B gastritis Possible association with peptic ulcers Long-term H. pylori infection has been associated with gastric cancer |
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Lab diagnosis of Helicobacter
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Recovered from gastric biopsy materials
Must be transported to lab quickly Stuart transport medium Microscopically similar to Campy Antibody tests (ELISA) Gastric biopsy stained samples Strong urease producer -Sample placed into Christensens urea medium and incubated at 37°C for 2 hours Urea Breath test |
