2Large, diverse group of non-spore-forming bacteria Wide range of habitats – large intestines (enteric), zoonotic, respiratory, soil, waterMost are not medically important; some are true pathogens, some are opportunists.All have a lipopolysaccharide outer membrane of cell wall – endotoxin.
4Aerobic Gram-Negative Nonenteric Bacilli Pseudomonas and Burkholderia – an opportunistic pathogenBrucella and Francisella – zoonotic pathogensBordetella and Legionella – mainly human pathogensAlcaligenes – opportunistic pathogen
5Pseudomonas: The Pseudomonads Small Gram-negative rods with a single polar flagellumFree livingprimarily in soil, sea water, and fresh water; also colonize plants and animalsImportant decomposers and bioremediatorsFrequent contaminants in homes and clinical settingsUse aerobic respiration; do not ferment carbohydratesProduce oxidase and catalaseMany produce water soluble pigments.
7Pseudomonas aeruginosa Common inhabitant of soil and waterIntestinal resident in 10% normal peopleResistant to soaps, dyes, quaternary ammonium disinfectants, drugs, dryingFrequent contaminant of ventilators, IV solutions, anesthesia equipmentOpportunistic pathogen
8Pseudomonas aeruginosa Common cause of nosocomial infections in hosts with burns, neoplastic disease, cystic fibrosisComplications include pneumonia, UTI, abscesses, otitis, and corneal diseaseEndocarditis, meningitis, bronchopneumoniaGrapelike odorGreenish-blue pigment (pyocyanin)Multidrug resistantCephalosporins, aminoglycosides, carbenicillin, polymixin, quinolones, and monobactams
10Other Gram-Negative Aerobic Rods Genera Burkholderia, Acinetobacter,StenotrophomonasSimilar to pseudomonadsWide variety of habitats in soil, water, and related environmentsObligate aerobes; do not ferment sugarsMotile, oxidase positiveOpportunistic
11BurkholderiaBurkholderia cepacia – active in biodegradation of a variety of substances; opportunistic agent in respiratory tract, urinary tract, and occasionally skin infections; drug resistantB. pseudomallei – generally acquired through penetrating injury or inhalation from environmental reservoir; wound infections, bronchitis and pneumonia, septicemia
12Acinetobacter and Stenotrophomonas Acinetobacter baumanii – nosocomial and community acquired infections; wounds, lungs, urinary tract, burns, blood; extremely resistant – treatment with combination antimicrobialsStenotrophomonas maltophilia – forms biofilms; contaminant of disinfectants dialysis equipment, respiratory equipment, water dispensers, and catheters; clinical isolate in respiratory soft tissue, blood ,CSF; high resistance to multidrugs
13Brucella and Brucellosis Tiny Gram-negative coccobacilli2 species:Brucella abortus (cattle)Brucella suis (pigs)Brucellosis, malta fever, undulant fever, and Bang disease – a zoonosis transmitted to humans from infected animalsFluctuating pattern of fever –weeks to a yearCombination of tetracycline and rifampin or streptomycinAnimal vaccine availablePotential bioweapon
14Francisella tularensis and Tularemia Causes tularemia, a zoonotic disease of mammals endemic to the northern hemisphere, particularly rabbitsTransmitted by contact with infected animals, water and dust or bites by vectorsHeadache, backache, fever, chills, malaise and weakness10% death rate in systemic and pulmonic formsIntracellular persistence can lead to relapsegentamicin or tetracyclineAttenuated vaccinePotential bioterrorism agent
15Bordetella pertussis Minute, encapsulated coccobacillus Causes pertussis or whooping cough, a communicable childhood afflictionAcute respiratory syndromeOften severe, life-threatening complications in babiesReservoir – apparently healthy carriersTransmission by direct contact or inhalation of aerosols
16Bordetella pertussis Virulence factors receptors that recognize and bind to ciliated respiratory epithelial cellstoxins that destroy and dislodge ciliated cellsLoss of ciliary mechanism leads to buildup of mucus and blockage of the airways.Vaccine – DTaP- acellular vaccine contains toxoid and other Ags
18Alcaligenes Live primarily in soil and water May become normal flora A. faecalis – most common clinical speciesisolated from feces, sputum, and urineoccasionally associated with opportunistic infections – pneumonia, septicemia, and meningitis
19Legionella pneumophila and Legionellosis Widely distributed in waterLive in close association with amebas1976 epidemic of pneumonia afflicted 200 American Legion members attending a convention in Philadelphia and killed 29Legionnaires disease and Pontiac feverPrevalent in males over 50Nosocomial disease in elderly patientsFever, cough, diarrhea, abdominal pain, pneumonia fatality rate of 3-30%Azithromycin
21Enterobacteriaceae Family EntericsLarge family of small, non-spore-forming Gram-negative rodsMany members inhabit soil, water, decaying matter, and are common occupants of large bowel of animals including humans.Most frequent cause of diarrhea through enterotoxinsEnterics, along with Pseudomonas sp., account for almost 50% of nosocomial infections.
23Facultative anaerobes, grow best in air All ferment glucose, reduce nitrates to nitrites, oxidase negative, and catalase positive.Divided into coliforms (lactose fermenters) and non-coliforms (non-lactose fermenters)Enrichment, selective and differential media utilized for screening samples for pathogens
26Antigenic Structures and Virulence Factors Complex surface antigens contribute to pathogenicity and trigger immune response:H – flagellar AgK – capsule and/or fimbrial AgO – somatic or cell wall Ag – all haveEndotoxinExotoxins
29Escherichia coli: The Most Prevalent Enteric Bacillus Most common aerobic and non-fastidious bacterium in gut150 strainsSome have developed virulence through plasmid transfer, others are opportunists.
30Pathogenic Strains of E. coli Enterotoxigenic E. coli causes severe diarrhea due to heat-labile toxin and heat-stable toxin – stimulate secretion and fluid loss; also has fimbriaeEnteroinvasive E. coli causes inflammatory disease of the large intestine.Enteropathogenic E. coli linked to wasting form infantile diarrheaEnterohemorrhagic E. coli, O157:H7 strain, causes hemorrhagic syndrome and kidney damage; ID 100 cells
31Escherichia coliPathogenic strains frequent agents of infantile diarrhea – greatest cause of mortality among babiesCauses ~70% of traveler’s diarrheaCauses 50-80% UTIColiform count - indicator of fecal contamination in water
32Other Coliforms Clinically important mainly as opportunists Klebsiella pneumoniae– normal inhabitant of respiratory tract, has large capsule, cause of nosocomial pneumonia, meningitis, bacteremia, wound infections and UTIsEnterobacter sp. – UTIs, surgical woundsSerratia marcescens – produces a red pigment; causes pneumonia, burn and wound infections, septicemia and meningitisCitrobacter sp. – opportunistic UTIs and bacteremia
33Noncoliform Lactose-Negative Enterics Proteus, Morganella, ProvidenciaSalmonella and Shigella
34Opportunists: Proteus and Its Relatives Proteus, Morganella, Providencia – ordinarily harmless saprobes in soil, manure, sewage, polluted water, commensals of humans and animalsProteus sp. - swarm on surface of moist agar in a concentric patterninvolved in UTI, wound infections, pneumonia, septicemia, and infant diarrheaMorganella morganii and Providencia sp. involved in similar infectionsAll demonstrate resistance to several antimicrobials.
36Salmonella and Shigella Well-developed virulence factors, primary pathogens, not normal human floraSalmonelloses and Shigellosessome gastrointestinal involvement and diarrhea but often affect other systems
37Typhoid Fever and Other Salmonelloses Salmonella typhi – most serious pathogen of the genus; cause of typhoid fever; human hostS. cholerae-suis – zoonosis of swineS. enteritidis – includes 1,700 different serotypes based on variation on O, H, and capsular antigenFlagellated; ferments glucoseResistant to chemicals –bile and dyes
38Typhoid FeverBacillus enters with ingestion of fecally contaminated food or water; occasionally spread by close personal contact; ID 1,000-10,000 cellsAsymptomatic carriers; some chronic carriers shed bacilli from gallbladderBacilli adhere to small intestine, cause invasive diarrhea that leads to septicemiaTreat chronic infections with chloramphenicol or sulfa-trimethoprim2 vaccines for temporary protection
40Animal SalmonellosesSalmonelloses other than typhoid fever are called enteric fevers, Salmonella food poisoning, and gastroenteritis.Usually less severe than typhoid fever but more prevalentCaused by one of many serotypes of Salmonella enteritidis; all zoonotic in origin but humans can become carrierscattle, poultry, rodents, reptiles, animal and dairy productsfomites contaminated with animal intestinal flora
41Shigella and Bacillary Dysentery Shigellosis – incapacitating dysenteryS. dysenteriae, S. sonnei, S. flexneri and S. boydiiHuman parasitesInvades villus of large intestine, can perforate intestine or invade bloodEnters Peyer’s patches instigate inflammatory response; endotoxin and exotoxinsTreatment – fluid replacement and ciprofloxacin and sulfa-trimethoprim
43The Enteric Yersinia Pathogens Yersinia enterocolitica – domestic and wild animals, fish, fruits, vegetables, and waterbacteria enter small intestinal mucosa, some enter lymphatic and survive in phagocytes; inflammation of ileum can mimic appendicitisY. pseudotuberculosis – infection similar toY. enterocolitica, more lymph node inflammation
44Nonenteric Yersinia pestis and Plague Tiny, Gram-negative rod, unusual bipolar staining and capsulesVirulence factors – capsular and envelope proteins protect against phagocytosis and foster intracellular growthcoagulase, endotoxin, murine toxin
46Yersinia pestisHumans develop plague through contact with wild animals (sylvatic plague) or domestic or semidomestic animals (urban plague) or infected humans.Found in 200 species of mammals – rodents, without causing diseaseFlea vectors – bacteria replicates in gut, coagulase causes blood clotting that blocks the esophagus; flea becomes ravenous
48Pathology of Plague ID 3-50 bacilli Bubonic – bacillus multiplies in flea bite, enters lymph, causes necrosis and swelling called a bubo in groin or axillaSepticemic – progression to massive bacterial growth; virulence factors cause intravascular coagulation subcutaneous hemorrhage and purpura – black plaguePneumonic – infection localized to lungs, highly contagious; fatal without treatment
49Diagnosis depends on history, symptoms, and lab findings from aspiration of buboes. Treatment: streptomycin, tetracycline or chloramphenicolKilled or attenuated vaccine availablePrevention by quarantine and control of rodent population in human habitats
51Pasteruella multocida Zoonotic genus; normal flora in animalsOpportunistic infectionsAnimal bites or scratches cause local abscess that can spread to joints, bones, and lymph nodes.Immunocompromised are at risk for septicemia and complications.Treatment: penicillin and tetracycline
52Haemophilus Tiny Gram-negative pleomorphic rods Fastidious, sensitive to drying, temperature extremes, and disinfectantsNone can grow on blood agar without special techniques – chocolate agar.Require hemin, NAD or NADPSome species are normal colonists of upper respiratory tract or vagina (H. aegyptius, H. parainfluenzae, H ducreyi).Others are virulent species responsible for conjunctivitis, childhood meningitis, and chancroid.
53HaemophilusH. influenzae – acute bacterial meningitis, epiglottitis, otitis media, sinusitis, pneumonia, and bronchitissubunit vaccine HibH. aegyptius –conjunctivitis, pink eyeH. ducreyi – chancroid STDH. parainfluenzae and H. aphrophilus – normal oral and nasopharyngeal flora; infective endocarditis