Fastidious Gram Negative Rods PDF

Fastidious Gram Negative Rods RAQUEL M. FERNANDEZ, RMT, MSPH General Characteristics Do not grow readily on routinely used lab media Facultative anaerobes, others are aerobic or microaerophilic Human infection with these bacteria is relatively uncommon Haemophilus, Francisell...

Fastidious Gram Negative Rods RAQUEL M. FERNANDEZ, RMT, MSPH General Characteristics Do not grow readily on routinely used lab media Facultative anaerobes, others are aerobic or microaerophilic Human infection with these bacteria is relatively uncommon Haemophilus, Francisella, Legionella, Bordetella and Brucella HACEK (Haemophilus parainfluenza, Aggregatibacter, Cardiobacterium, Eikenella and Kingella) causing SBE Haemophilus Facultative anaerobes that require enriched medium that contains fresh blood or some of its components (heme and/or NAD) for isolation and growth “hemophilic” requires X (heme) and V factor (NAD) present in fresh blood Multiply slowly in culture and requires 5-10% CO2 Relatively short, pleomorphic, non-motile gram negative rods often assuming coccobacillary forms Haemophilus A polysaccharide capsule is frequently present on isolates from clinical specimens Serotyping of capsular antigens is important because of the clinical significance of type b capsule Useful Tests ALA or Porphyrin Test: some Haemophilus are able to use delta- aminolevulenic acid as a substrate to synthesize heme factor, in the process porphyrins are created Porphyrins produce a pink fluorescence under UV light Much more accurate means of determining X factor requirement compared to X and V factor disks Horse Blood Agar Hemolysis is determined on HBA since it cannot hemolyze sheep’s blood Hemolysis is subtle and best viewed with light originating from behind the agar plate Stabbing the area of inoculation enhances the hemolytic reaction X and V factor requirement X factor is known as heme, hemin or hematin used in the synthesis of catalase, peroxidase and in the cytochrome electron transport system V factor is NAD, a co-enzyme that transfers electrons from one reaction to another Both are found inside RBCs X and V factors test H. influenzae and H. aegyptius Appear as coccobacilli, thread- like rods and high pleomorphism is evident A capsule is frequently present on initial isolation but can be rapidly lost on subculture Colonies are round, small, and convex, non-hemolytic Most H. influenza produces acid from glucose and xylose but not lactose or sucrose H. Influenzae and H. aegyptius Variable reaction for urease and indole H. aegyptius can be distinguished from H. influenzae by a negative xylose reaction All H. influenza from clinical samples should be serotyped esp. for patients < 15 years of age The organism can produce 6 different antigenic types of capsule: a-e Latex agglutination test is a rapid test for detection of these capsular antigens Clinical Significance Also known as Pfeiffer bacillus named after Richard Friedrich Johannes Pfeiffer who discovered it in the great influenza pandemic in 1892 It does not cause influenza although it was originally believed to be the cause since most of the victims had flu It is often a secondary invader in individuals infected with Influenza A Adherence is mediated by pili, Hib being notorious Organism is transmitted person to person via respiratory droplets resulting in sinusitis and infection of the middle ear Clinical Significance Hib can also cause pneumonia, empyema, epiglottitis, cellulitis, septic arthritis The most common manifestations of illness in elderly and debilitated adults are bronchitis and pneumonia Treatment with β-lactam antibiotics can be useful if the organism does not produce β-lactamase. Ceftriaxone, Fluroquinolones may be required The original vaccine consisted only of the type b polysaccharide. Today, 4 conjugated vaccines for type b are available Clinical significance May be carried in the URT by approximately 2-4% of healthy individuals The carrier rate is much higher (up to 80%) for non-typable forms that do not have a capsule The non-encapsulated strains are usually non-invasive. They tend to cause problems only in patients who have chronic underlying conditions such as bronchitis, emphysema, or COPD H. aegyptius is relatively a common cause of conjunctivitis and is often isolated from blood cultures Antibiogram pattern Most strains are susceptible to ampicillin 25-30% are β-lactamase positive Most strains are susceptible to newer cephalosphorins (Cefotaxime and Ceftriaxone) H. parainfluenzae Resemble H. influenza in both microscopic and colonial morphology In blood cultures, the organisms may appear as large clumps of filamentous rods ALA+ and require only NAD Non-hemolytic on HBA Produce acid and gas from glucose and sucrose but not lactose or xylose Variable for urease and catalase and negative for indole Clinical Significance Part of the normal microbiota of the human respiratory tract Etiologic agent of endocarditis, urethritis and URT They are capable of colonizing the GIT tract and have been implicated in sporadic cases of peritonitis and cholecystitis H. ducreyi Small gram negative coccobacilli that tend to grow in short chains, clumps or whorls within lesions They can be seen in railroad track, school of fish or fingerprint arrangements Individual bacteria exhibit bipolar staining H. ducreyi Organism is very difficult to culture Scrapings of an ulcer is best accomplished on CAP containing Isovitalex and Va, incubation at 33°C in 10% CO2 Plates must be incubated for 10 days Yellowish to gray, dome-shaped, smooth colonies H. ducreyi Requires heme factor but not NAD Unable to synthesize porphyrin and does not cause hemolysis on HBA Most are catalase negative, urease -, indole -, acid is produced from lactose, sucrose and xylose Clinical Significance Causes “chancroid” , swelling of inguinal lymph nodes Bacteria are transmitted by direct sexual contact Unlike syphilis chancre, the lesion is painful Virulence factors include hemolytic cytotoxin, a cytolethal distending toxin, pili, hemoglobin binding protein and lipooligosaccharide Immunity to the organism does not develop after infection Treatment with Ceftriaxone, TMP-SXT, E Condom use Francisella 2 species: F. tularensis and F. philomiragia but only tularensis is pathogenic for humans F. tularensis has 4 subspecies or biovars: subsp. tularensis (type A), subsp holarctica (type B), subsp. mediasiatica and subsp. novicida F. tularensis is Category A biological agents by CDC Appear as non-motile, non-spore forming, strictly aerobic, gram negative bacilli or coccoid bacteria Facultative intracellular pathogens Fastidious and may require supplementation with cysteine, cystine or thiosulfate Francisella tularensis Does not grow on most routinely used lab media Very small transparent colonies will generally appear on cysteine- supplemented agar when incubated for 3 days at 37°C aerobically Best growth is obtained on blood-cysteine-glucose agar, enriched chocolate agar or Thayer Martin agar or BCYE or other media that contain cysteine Organism is highly infectious and should be handled on BSL 3 Organisms are extremely small, intracellular GNCB that stains poorly on Gram’s stain and highly pleiomorphic Identification Relatively inert biochemically Biochemical tests are not used for ID and not recommended Organisms are usually missed in smears from tissue specimens because of their small size and intracellular nature, high pleomorphism and pale staining with Gram’s stain The organisms have a thin capsule that consists of lipid, proteins and carbohydrates Francisella Choc agar, MTM, BCYE, MH and TSB broth can be used Mc and EMB will not support growth Grow after 48 hours Oxi-, urease-, satellite -, X and V factors -, weak catalase + As few as 50 organisms can cause infection through the cutaneous or inhalational routes BSL 3 precautions should be used with this organism Francisella Should be bagged and examined only under a BSC Colonies appear small, transparent after extended incubation Pinpoint colonies may appear after 24h of incubation oxidase, urease, indole and ornithine negative Weaky positive for catalase and produce beta-lactamase Facultative anaerobes Amino acid cysteine is required F. tularensis Direct FAT are used for the identification of the organisms in tissue and sputum specimens An antibody titer of 160 in a single specimen is highly suggestive of infection A four-fold increase in antibody titer in paired serum samples taken 2 weeks apart is strongly indicative of active disease Clinical Significance Agent of tularemia or glandular fever or tick fever and occasionally as deer fly fever or rabbit fever The genus name was given in honor of Edward Francis who studied the organism extensively The specie name is based on the location where the organisms were discovered (Tulare county, CA) Tularemia Zoonotic disease aka lemming and water rat trapper’s disease Can be transmitted through ingestion, inhalation, or arthropod-bite Can occur in pneumonic, glandular, oropharyngeal, oculoglandular and typhoidal forms The most common clinical form is ulceroglandular F. tularensis Present in wide variety of wild animals, birds and even some fish and amphibians Common reservoir are rabbits, muskrats and squirrels Infection can occur by direct contact with a dog or cat that has had contact with an infected animal Ticks and deerflies are the most common arthropod vectors 3 routes of transmission: Bite of an arthropod Direct contact with infected animal Ingestion of contaminated meat or water F. tularensis Males and children under the age of 10 years have the highest incidence of tularemia Hunters, vets and taxidermist are at increased risk for infection There are 2 biotypes: Biotype A is found in the US and North America. It is highly virulent. Transmission is via the bite of a tick that has acquired the organism from infected wild rabbits Biotype B is more widespread found in Western and Eastern hemispheres and is associated with water and rodents Manifestations are highly dependent on the route of transmission F. tularensis Fever, malaise, headache, and pain in the involved region are noted Infection occurs most often through minute abrasions in the skin resulting in greatly enlarged regional lymph nodes that sometimes drain for weeks and become necrotic Streptomycin is the drug of choice or Gentamicin over a period of 10 days. Ceftriaxone is not effective. Vaccine provides partial immunity The organism is Category A Legionella pneumophila Discovered after an outbreak of severe respiratory illness at an American Legion convention that took place in 1976 in Philadelphia Can cause Pontiac fever, an influenza like illness that initially occurred during an outbreak in Michigan Ubiquitous in the environment where warm and moist conditions prevail Have been recovered from lakes, streams, mud and soil No known animal reservoir Of more than 40 species, L. pneumophila is by far the most common cause of disease in humans Legionella pneumophila There are at least 10 serogroups with serogroup 1 being the cause of the 1976 outbreak Aerobic, gram negative rods that can be isolated on BCYE supplemented with 1% α-ketoglutarate The organism requires iron salts, cysteine and high humidity for growth Best growth is obtained at a pH of 6.9, 37°C and 90% humidity Antibiotics are sometimes added to the medium to prevent overgrowth by other bacteria Growth in blood cultures usually requires at least 2 weeks of incubation Legionella pneumophila In Grams stained smears, the organisms are small, pleomorphic GNB Usually detected in clinical specimens by direct FAT Catalase+, gelatinase+ and produces beta-lactamase Produces metalloprotease, lipase, DNAse, RNAse Legionella pneumophila Can be distinguished from other members of the genus by its production of the oxidase enzyme and its ability to hydrolyze hippurate On Grams stain the bacteria appear as relatively thin (0.5-1.0 µm in width) rods but can range from 2- 50 µm in length but they do not stain well with Grams stain Basic fuchsin is often used as a counterstain for 3 minutes Legionella pneumophila Visible colonies usually appear within about 3-4 days of incubation on an appropriate medium Colonies may be round or flat with entire edges, glistening, and convex They appear to have ground glass speckling like a shattered windshield Pigmentation can vary from colorless, grayish, pale green to indescent pink or blue Colonies may be translucent Legionella pneumophila Specimens for culture include bronchial washings, lung biopsies, pleural fluid, and blood Sputum is not an optimal choice for culture bec of abundance of URT microbiota Fluoresces under long-wave fluorescent light (Wood’s lamp) exhibiting a pale yellow green fluorescence Many patients are diagnosed retrospectively by an indirect FAT a 4- fold rise in anti-Legionella antibody to a titer of 128 or greater is considered positive Clinical Significance Agent of Legionnaire’s disease most common in males over 35 years who have risk factors of smoking, emphysema and other chronic respiratory conditions Organisms are acquired through inhalation of aerosols created by contaminated air conditioners, showerheads, humidifiers The organisms infiltrate the lungs and survive in alveolar macrophages They are relatively resistant to destruction by PMNs Inhibit fusion of phagosomes with lysosomes Disease ranges from a mild, short-term febrile illness to an acute purulent pneumonia with an intra alveolar exudate Pontiac fever Characterized by sore throat, cough, headache, fever, chills, malaise, myalgia, dizziness, confusion, photophobia and stiffness of the neck Erythromycin is the drug of choice because it can penetrate WBCs to reach the intracellular organism Rifampin also occasionally used Bordetella pertussis Strict aerobe Gram negative Small coccobacillus -singly or in pairs Transmission by aerosolized droplets Non-invasive Strictly human pathogen Bordetella pertussis Best culture on media containing charcoal to neutralize inhibitory effects Bordet-gengou (potato-sheep- blood- glycerol) medium that includes Pen G Regan-Lowe is often used as transport medium Incubation is 3-7 days at 35°C in a moist enclosure such as sealed plastic bag Diagnosis Based on symptoms Culture of respiratory secretions on Bordet-Gengou medium Direct fluorescent antibody testing PCR Slide agglutination Bordetella pertussis Biochemical reactions are DFA must be used in tandem generally not used for ID with culture due to its low A saline nasal wash and sensitivity nasopharyngeal swab are the Serologic tests for antibodies are most common specimens not very useful for rapid DFA and slide agglutination tests diagnosis bec agglutinating and are performed to detect the precipitating properties do not bacteria in nasopharyngeal appear until the 3rd week of aspirate specimens as well as illness colonies on culture  DIFFERENTIATION OF BORDETELLA SPECIES Growth on Growth on common lab Bordet- media Urease Oxidase Motility Gengou agar (SBA, MacConkey) B. pertussis - + - + - B. parapertussis + + - - B. bronchiseptica + + + +  B. pertussis Small, transparent hemolytic colonies on Bordet-Gengou medium Clinical Significance Humans are the only known source Whooping cough Most cases occur in children under 5 years of age Most deaths occur in infants Transmission occurs by inhalation of contaminated aerosols from individuals who have the early stage of disease Pertussis Pathogenesis Two-stage process of disease Respiratory colonization 7-10 days NO symptoms Positive cultures toward the end of this stage Toxin-mediated disease Stages of Whooping Cough INCUBATION STAGE. At least 2 weeks CATARRHAL STAGE. Manifested by a mild cough and sneezing. Patient is highly infectious with large numbers of organisms in the respiratory droplets PAROXYSMAL STAGE. Severe cough and a whooping sound during inhalation. Cyanosis, vomiting, and convulsions may also occur along with rapid exhaustion CONVALESCENT STAGE Colonization Fimbriae are NOT involved. Attachment requires 2 factors Pertussis Toxin Filamentous hemagglutinin  Pertussis Toxin AB-toxin (6 protein subunits) Pertussis- Disease Primarily a toxin-mediated disease Exotoxins are controlled by central locus BvgAS two-component signal transduction system to sense the environment and regulate gene expression Pertussis- Disease Inflammation interferes with clearance of pulmonary secretions Cough progresses from mild (catarrhal stage) to severe (paroxysmal stage) Resolves slowly Evasion of host defenses lymphocytosis Bordetella pertussis Toxins FIVE DIFFERENT TOXINS Systemic effects of Pertussis Toxin Systemic effects T cell Lymphocytosis with ↓ mitogenicity ↑ insulin and histamine production ↑ IgE production Impaired phagocyte functions Adenylate cyclase Toxin Both adenylate cyclase and hemolysin Secreted invasive toxin Adenylate B. cyclase toxin pertussis ↑ calmodulin cAMP  Other Toxins: 1. Dermonecrotic toxin (lethal toxin) – Strong vasoconstrictor 2. Tracheal cytotoxin – Prevents ciliated epithelial cells from beating 3. Lipopolysaccharide - endotoxin  Treatment Erythromycin Vaccine killed bacterial cell suspension -DPTvaccine Vaccine- induced immunity wanes after five to ten years acellular vaccines Multicomponent acellular vaccines Brucella Intracellular bacteria that are usually found in animals with humans being accidental hosts First isolated by Sir David Bruce on the island of Malta Based on DNA analyses, there is only one species B. melitensis however bacteria are often still referred by their original species or designations B. melitensis (goat and sheeps), B. suis (swine), B. abortus (cattle) and B. canis (dogs) Causes Brucellosis or also known as Malta fever or undulant fever General characteristics Strictly aerobic, intracellular bacteria that have a complex growth requirements They will grow on well-defined media containing amino acids, vitamins, salts and glucose Grow slowly on sheep’s BAP or CAP with 5-10% CO2 Organisms are non-motile, gram negative rods that stain irregularly and pale with Gram’s stain Inactive metabolically Catalase+, Oxidase+, do not produce acid or gas in significant amounts, reduce nitrates to nitrite Brucella Small gram negative, aerobic, non-motile, non-spore forming unencapsulated coccobacilli or bacilli Can be transmitted through aerosols Should be handled under BSL-3 conditions Oxi+, cat+, urease+ Infection can be laboratory acquired Brucella Zoonotic disease Category B (select biological agents) by CDC Reportable disease because it is a potential bioterrorist agent Infection is acquired through aerosol, percutaneous and oral routes of exposure Species: B. melitensis, B. abortus, B. suis, B. canis, B. ovis, B. neotomae Brucella identification Short, coccobacillary forms bipolar staining sometimes evident Colonies appear after 3-5 days of incubation on enriched media as small, smooth, convex, transparent, non-hemolytic On subculture colonies tend to become rough because of loss of the capsule Pathogenesis Different biovars express different amounts of LPS antigens A, M and L Biovars are differentiated in the ability to produce H2S and susceptibility to certain dyes In the animals Brucella localize in the pregnant uterus because of the presence of Erythritol in allantoic and amniotic fluids Abortion is a major manifestation of the disease in animals Bacteria remain viable in dry soil for up to 60 days The bacteria localize in mammary glands of animals and can be shed in milk or cheeses or other products Stages of Brucellosis 3 clinical stage of Brucellosis: acute, sub-chronic and chronic Non- specific symptoms of acute infection appear within 8 weeks after exposure Subchronic or undulant form appear after a year of exposure with undulating fevers, arthritis and epididymoorchitis Chronic form presents after 1 year of exposure with symptoms of depression, arthritis and chronic fatigue Pathogenesis Farmers, vets and abattoir or slaughterhouse workers are at greatest risk for infection Incubation period ranges from 1-6 weeks Onset is slow and insidious and disseminated via the lymphatics and the blood stream Proliferation of mononuclear cells is a major histologic findings Fever may have a daily periodicity, rising in the afternoon and falling at night, malaise, weakness and non-specific aches and pains Immunity is good after recovery although reinfection is possible Pathogenesis Brucella is usually susceptible to Te, Streptomycin and Amp. The organisms are hard to eradicate because of their intracellular nature Administration of Streptomycin and Tetracycline for an extended period of time may be required Rifampin prophylaxis may be required for close contact below 4 years of age HACEK Group and Capnocytophaga HACEK is an acronym of the first initial of each genus that belong in the group: Haemophilus spp. Aggregatibacter aphrophilus and paraphrophilus Aggregatibacter actinomycetemcomitans formerly Actinobacillus actinomycetemcomitans Cardiobacterium hominis Eikenella corrodens Kingella species Capnocytophaga sp. Has similar requirements as the HACEK group HACEK Group and Capnocytophaga: General Characteristics Gram-negative bacilli Require an increased CO2 (5%-10%) environment Considered to be more dysgonic (slower or poorer growing) Significant cause of endocarditis Usual flora of the oral cavity All organisms are opportunists in immunocompromised hosts Include both fermentative and non-fermentative gram negative bacilli Aggregatibacter aphrophilus Aphros “foam loving” or needing high concentration of CO2 Found in dental plaque and gingival scrapings Most prevalent cause of endocarditis Clinical features of infection: fever, heart murmur, CHF, and embolism Colonies are convex, granular and yellow with opaque zone near the center on CAP HACEK Group H. aphrophilus growing on blood agar Gram stain morphology of H. aphrophilus Aggregatibacter actinomycetemcomitans Formerly Actinobacillus 6 species have been recovered in humans Produce small bacilli to coccoid gram negative bacilli that are non- motile Composed of 6 serotypes (a-f) based on its surface polysaccharides Normal oral microbiota of humans Has been isolated from blood, lung tissue, abscesses of the mouth and brain and sinuses Causes SBE and periodontitis Aggregatibacter actinomycetemcomitans Virulence factors include collagenase, leukotoxin Fermenter when serum is added to the carbohydrate Growth is star-shape with 4-6 points at the center of the colonies after 48 hours Isolates are catalase+, negative for X and V factors Do not grow in McConkey, oxidase variable Urease -, Indole -, esculin - and citrate -, ferments glucose but not lactose or sucrose P, aminoglycosides, 3rd gen Cephalosphorins, quinolones, C and Te sensitive HACEK Group A. actinomycetemcomitans on blood agar. Note the star- shaped centers of the colonies. Microscopic morphology of A. actinomycetemcomitans (Gram stain). Cardiobacterium hominis is a pleomorphic, non-motile, fastidious GNB Normal microbiota of the nose, mouth and throat May be present in the GIT Usual manifestation is endocarditis often presenting with large vegetations and no demonstrable fever Infects the aortic valve Associated with meningitis Gram stains of the bacilli often show false Gram positive reactions in parts of the cells Cardiobacterium hominis On Grams stain organisms tend to form rosette swellings, long filaments, or stick like structures in yeast extract Grow slowly on SBA and CHOC agar but not at all on McConkey agar Incubation with 5% CO2 enhances growth Fermenter when serum is added Ferments glu, mannitol, suc and maltose Isolates are OXI +, CATALASE -, INDOLE + Negative for urease, nitrate, gelatin and esculin Usual therapy includes P and aminoglycoside HACEK Group The 48-hour growth of colonies of C. hominis Gram stain of C. hominis showing typical “rosettes” Eikenella corrodens Normal microbiota of the oral and bowel cavities “human bites or fights” infection Associated with poor dental hygiene or oral surgery Reported as a cause of meningitis, empyema, pneumonia, osteomyelitis, arthritis and post-op infections Shows least predilection for attachment to heart valves among HACEK Isolates are fastidious, gram negative coccobacilli Non-motile, oxidase+ and assacharolytic Catalase – and often produce a yellow pigment Eikenella corrodens Corrodes (pits) the surface of agar Non-hemolytic but may show greening around the colonies on SBA A bleach-like odor from the agar surface may be obvious Isolates do not grow on Mc or EMB In broths, may adhere to the sides of the tube and produce granules Lysine and ornithine decarboxylase + Arginine dihydrolase – R to Clindamycin, and aminoglycosides In vitro, S to P, Am, Cefoxitin, C, Carbenicillin and Imipenem HACEK Group E. corrodens on chocolate agar Gram stain morphology of E. corrodens Kingella 3 species: K. kingae, K. denitrificans and K. oralis Coccobacillary to short bacilli with squared ends that occur in pairs or short chains Tend to resist decolorization in the Grams stain May grow on MTM, resemble colonies of Neisseria when they do not pit agars which many usually do Non-motile, oxi+, catalase -, fermenters of glu with no gas Colonize the URT, associated with poor dental hygiene or oral surgery Kingella denitrificans is positive for glucose fermentation and nitrate reduction Catalase - and superoxol – Negative for urease, indole, esculin, gelatin and citrate Kingella kingae Recognized as an important pathogen in pediatric population Weakly ferments glu and maltose but not suc May produce a yellow pigment Has 2 types of colonies: spreading or corroding or a smooth, convex β-hemolytic colonies Isolates have been obtained clinically from blood, bone, joint fluid, urine and wounds Major gram negative bacterium isolated from degenerative joint and bone infections in children < 3years Kingella kingae Causes endocarditis in adults and school-age children Most isolates are susceptible to most antibiotics HACEK group Gram stain of Kingella kingae showing plump rods in chains. Compare this morphology with other members of the HACEK group.  HACEK Group and Capnocytophaga Growth of Capnocytophaga colonies Gram stain of Capnocytophaga on chocolate agar. Compare this species growth with Eikenella Capnocytophaga Belongs to the family Flavobacteriaceae and includes dysgonic fermenters called DF-1 and DF-2 Genus consists of 7 species, 5 of which are normal microbiota of the oral cavity Are not commonly involved in endocarditis but is associated in septicemia in patients with neutropenia Fastidious, facultatively anaerobic, GNB Thin and often fusiform (pointed ends) resembling Fusobacterium Flagella are absent but produce gliding motility on solid surfaces Capnocytophaga Colonies are adherent and produce a yellow-orange pigment mostly are non-hemolytic Ferment suc, glu, malt, lac although TSI is negative, indole - Negative for most biochemical reactions Reduce nitrates and hydrolyzes esculin Oxi-, catalase- Most are isolated from dental plaque C. ochracea is the most common clinical isolate Capnocytophaga C. canimorsus can cause a fulminant, life-threatening infection in humans following a dog or cat bite S to Imipenem, E, Clindamycin, Te, C, Quinolones, and β-lactams R to aminoglycosides P is the drug of choice Pasteurella species 17 species have been identified based on DNA hybridization P. canis is associated with dogs P. stomatis and P. dagmatis are associated with dogs and cats and also isolated from humans P. multocida has 3 subspecies: multocida, septica and gallicida P. multocida consists of 5-serogroups (A-F) Pasteurella species General characteristics Colonizes mucous membranes of the upper respiratory tract and gastrointestinal tracts of mammals and birds Human infections occur from bites and scratches inflicted by animals Most common isolated species is Pasteurella multocida Pasteurella species Gram negative coccobacilli appearing ovoid, filamentous or as bacilli, exhibiting safety pin appearance or bipolar staining non-motile, facultative anaerobe, oxi+, cat+ Ferment glu without gas All will grow on SBA (non-hemolytic) and CAP producing grayish colonies but not on McConkey Colonies on SBA may appear mucoid with with narrow green to brown halo Pasteurella multocida Clinical manifestations: systemic, pneumonic or cutaneous form of infections Localized infection after a bite or scratch Respiratory tract infection Life-threatening systemic diseases (e.g., meningitis, bacteremia) Pasteurella multocida Culture characteristics Growth on 5% blood or chocolate shows small, smooth, convex colonies “Musty” odor No growth on MacConkey agar; oxidase positive Microscopic examination Very small gram-negative rods Bipolar staining with Giemsa or methylene blue “Safety-pin” appearance Pasteurella multocida P. multocida growing on blood agar and chocolate agar. No growth on MacConkey agar plate. Gram stain morphology of P. multocida showing bipolar staining Pasteurella bettyae Has been isolated from placenta, amniotic fluid, blood, rectal sites, abscesses and urogenital specimens Isolates are fastidious, capnophilic coccobacilli Facultative anaerobe, non-motile Ferment glu and fruc Cat+, indole+ and oxidase variable They may grow on McConkey