BIOL 2421 Microbiology Lecture Notes: Gram Neg Diseases (Major Groups)Dr

BIOL 2421 Microbiology Lecture Notes: Gram Neg Diseases (Major Groups) Dr. Weis

ENTEROBACTERIACEAE [part of the gamma proteobacteria phylum]

G (-)

F.A.

Non sporeformers

Mesophiles

Oxidase (-); Catalase (+); Reduce nitrates to nitrites

Escherichia

5 species

mixed acid fermentors

Indole (+); H2S (-); Urease (-); Citrate (-)

Motile

Species further subdivided by O-cell wall Antigens and H flagellar Antigens

E. coli

Normal GI flora for colon, urethra, vagina for humans and animals

Reservoir: feces, water

Clinical Disease Course: Enteric à watery, bloody diarrhea

Urinaryà UTI, Renal failure

Can spread to liver, skin, lungs (especially in indiv. decreased immunity)

Diseases

Enteropathogenicà infant diarrhea, adult traveler’s diarrhea

Enterotoxicà infant diarrhea, adult traveler’s diarrhea

Enterohemorrhagicà undercooked meat à hemorrhagic colitis

Enteroaggregativeà diarrhea in immunocompromised individuals

Virulence Factors

· Enterotoxin: Heat Stable Toxin (ST); Heat Labile Toxin (LT)

· Hemolysins [alpha, beta, enterhemolysin]

· Fimbria à adhesions

· Cytotoxins à causing necrosis

· Flagella à motility

DX: separate out pathogens from commensals with Biochemistries

TX: AB [penicllin, cephalosporins, TMPS]

Supportive: fluid and electrolyte replacement

Prevention: cook meat, pasteurize dairy products

Personal hygiene

Salmonella

Some debate over speciation: some think one major with subtypes

Classified based on O cell wall Antigens and H flagellar Antigens

Human Pathogens

S. typhi, S. paratyphi, S. cholerasuis, S. enteritidis

Salmonella typhi :

motile

Normal flora in cold blooded animals

Carrier state in colon of humans acts as a reservoir

Transmission: fecal à oral via water, food (direct) or flies (indirect)

Incubation: 8-14 days

Clinical course: fever à abdominal pain [prostration due to tissue necrosis]

Ulceration à hemorrhage à rose rash, prominent diarrhea à

Perforation of gut wall

Septicemiaà heart, lungs, bone, brain

Disease Presentations

· Gastroenteritis/colitis

· Septecemia

· Typhoid Fever

Virulence factors:

Motility

Enterotoxin : Heat Labile Toxin [LT]

Cholera-like toxin

Cytotoxin [like Shiga toxin]à cell destruction

Adhesions

+/- capsule

DX: ID organism from fluids

Ab titer for O - H antigens

TX: AB [cephalosporins]

Supportive care to replace electrolytes and fluid

Prevention: clean water, hygiene

Non typhoidal Salmonella

S. enteritidis, serotype: S. typhimurium

Transmission: direct and indirect via meat, eggs, milk

Clinical course:

Enteric fever: fever and septicemia

Focal: GI organs [liver, gall bladder], heart, lungs, joints, bones

Bacteremia à septic arthritis

DX: BICH

TX: AB and supportive care

Prevention: proper cooking and food preparation

Personal hygiene

SHIGELLA

4 species: S. dysenteriae, S.flexneri, S. boydii, S. sonnei

Related to E.coli

nonmotile

weak fermentation, no gas

citrate (-)

serotypes divided according to O cell wall antigens

Not part of normal flora, will be human carriers as sources/reservoirs

Incubation 1-4 days

Transmission: fecal à oral via contaminated food or mechanical vectors (flies)

Clinical Course: penetrate mucosa of lower intestine to cause inflammatory

Dysentery resulting in mucus à edema à ulceration à tenesmus

Vomiting and Diarrhea with rice-water stools, mucus, blood, and pus

Resulting in a hemorrhagic colitis

Other diseases: Uremia à renal failure

Hemolytic anemia

Thrombocytopenia

Virulence factors:

Shiga toxin (A*B toxin) that binds to human 60S ribosomes

Hemolysin

Adhesin, Invasin

Toxins: neurotoxin, cytoxins, enterotoxins

Certain species have NAD glycohydrolase which decreases NAD of

the WBC phagocyte in order to block cell metabolism, killing WBC.

Actin tail à used to propel in and through cells

DX: Id organism in stool

TX: supportive to replace fluids and electrolytes

AB [TMPS]

Prevention: hygiene

Clean water

? vaccine – still at trial phase

YERSINIA

G (-) coccobacillus

+/- motile [temperature dependant]

psychotrophic

Yersinia enterocolitica

Ferments glucose, no gas

Oxidase (-), urease (+)

Serotypes based on O –cell wall antigens

Not part of normal flora of humans; normally in frogs, birds, fish, fleas, flies, oysters

Transmission: Fecal à oral

Clinical course: adherence to mucosa epithelial cells of intestine à diarrhea and

Appendicitis. Can progress to L.N. causing abscess and arthritis

DX: Culture on special iron media

ELISA

TX: AB

Prevention: proper cooking of meet, hygiene

Yersinia pestis [Formally Pasteurella pestis]

G (-) short bacillus with bipolar staining (looks like safety pin)

Non motile, non sporeformer

Causative agent of Bubonic plague or Black death

Plague is endemic in wild rodents

Tranmitted via flea vector bite or direct by respiratory droplets

Incubation is 2-5 days

Clinical Course: Enlarged LN (buboes) à fever à lymphatic organ size increase

Can progress to tachycardia, tachypnea with cough and raspberry syrup sputum and pneumonia and eventual CNS dementia

Disease course: Bubonic Plague [70% mortality]

Pnemonic Plague [100% mortality]

Black Death (due to DIC) [100% mortality]

Virulence Factors: LPS, Plasmids

DX: culture organism from fluids, LN aspirate; CF ; IFA

TX: AB [streptomycin, tetracycline]

Prevention: Rodent control, flea control

Haemophilus

Genera: H. influenza, H. parainfluenza, H. aphrophilus, H. ducreyi, H aegyptius

G (-) coccobacillus

Nonmotile

Non-sporeformer

Haemophilus influenza

(haemo = blood requirement to synthesize parts of cytochrome system for resp.)

6 serotypes {A-F} B is worst

Normal flora : URT, oropharynx, conjunctiva, vagina, intestinal tract

Transmission: respiratory droplet

Clinical course: diseases primarily affect children

Infantile meningitis

Septic arthritis

Sinusitis

Bronchitis

Pneumonia

Cellulitis

Virulence factors:

LPS [Lipid A]

Protease (IgA)

Adhesins

Capsule

DX: ELISA

Culture on chocolate agar

X factor [heme of hemoglobin]

V factor [NAD+ or NADP+]

TX: AB [cephalosporins]

Prevention: Vaccination

Haemophilus ducreyi

Causative agent of STD chancroid

Seen primarily with HIV patients

VIBRIONACEAE Family, part of the gamma proteobacteria phylum group

Vibrio

Aeromonas [see other notes]

Plesiomonas [see other notes]

G (-) rods that can be straight or curved

Non-sporeforming

Motile with polar flagella in liquid media and peritrichous in solid media

Aerobic or anaerobic

Catalase (-) and oxidase (+)

May produce acid and or gas from carbohydrate fermentation

Vibrio genus

V. cholerae, V. alginolyticus, V. damsela, V. fluvialis, V. furnissii, V. hollisae,

V. metschnikovii, V. mimicus, V. parahemolyticus, and V. vulnificus

Vibrio cholerae

Serotyping is based on the cell wall O antigen

VP +; Indole +; decarboxylate lysine; reduce nitrate to nitrite

Reservoir: seafood and seawater; coastal waters; human carrier state

Transmission: fecal à oral

Incubation 1-3 days

Various strains: [01 and 039] more virulent than [non-01]

Clinical course:

Mild, uncomplicatedà generalized gastroenteritis

Fulminant, lethalà profuse rice-water diarrheas

Small intestines affected à profuse watery diarrhea rich in electrolytes à

Vomiting, cramps à dehydration à oliguria à collapse

Virulence factor

Enterotoxin [Cholera toxin]: AB toxin that binds to ganglioside and affects

Adenylate cyclase to increase cAMP which induces a hypersecretion of an isotonic electrolyte solution thereby causing a massive water and electrolyte depletion

(People with blood group “O” seem to be more susceptible)

Some strains produce a hemolysin

Some strains produce a heat stable (ST) enterotoxn and other toxins

DX: Isolation of organism in stool via rectal swabs

Special media (TCBS) will show sucrose fermentation and yellow colonies

TX: AB [TMPS, tetracyclines, norfloxacin]

Supportive care [fluids, electrolyte replacement]

Prevention: proper disposal of human excrement

Purify water supplies

Cook fish

Vaccine available (not in US)

PSEUDMONADACEAE family, part of the gamma proteobacteria phylum group

G (-) rods that are straight to slightly curved

Motile with polar flagella

Non sporeformer

4 genera: Pseudomonas, Zoogloea, Xanthomonas, Fraturia

Pseudomonas genera

Species: P. aeruginosa, P. cepacia, P. chlororaphis, P. cichori, P. flourescens,

P. mallei, P. pseudomalleii, P. putida, P. solanacearum, P. stutzeri,

P. syringae, P. testosterone, P. acidovorans, P. paucimobilis

Pseudomonas aeruginosa

Favors a moist environment

Aerobic

Nosocomial, opportunistic

Serology of subspecies based on cell wall O antigens

Normal flora in axillary & anogenital regions and other open body cavities (eyes, ears)

Transmission: infected soil and water

Clinical course: Purulent drainage à ulceration, maceratioin

Clinical areas: Skin of burn patients

Corneal ulceration

UTI

Osteomyelitis

Valvular endocarditis [primarily after heart surgery]

Bacteremia via contaminated materialsà memingitis

Respiratory: sinusitis, oropharyngitis, tracheitis, pneumonia

Also associated with CF infections

S.C. à cellulitis

Virulence factors:

LPS

Exotoxin A: attacks one of the elongation factors in translation,

therefore inhibits protein synthesis

Pili

Slime layer

Oxidase (+); catalase (+); gelatinase (+)

Some strains produce hemolysins àbeta hemolysis on BAP

Plasmids

Proteases, Elastases

Some strains produce excessive amounts of extracellular polysaccharides

DX: Id organism on culture

Has water soluble blue-green pigment

TX: Debride necrotic tissue

AB [aminoglycosides] à resistance is developing

Prevention: aseptic technique

LEGIONELLALES order, part of the gamma proteobacteria phylum

Legionella genera, 14 species

Coxiella genera

Legionella

G (-) with increased amounts of branched Fatty acid chains

Obligate aerobes

Motile with 1-3 polar flagella

Non capsulated

Non fermentors à use certain AA as primary carbon source

Catalase (+), oxidase (+)

Beta lactamase +

Legionella pneumophilia

14 serovars

Not part of normal human or animal flora

Reservoir: found in amoebae, soil, lukewarm water

Transmission: inhale aerosols of infectious organism

intracellular pathogen

will multiply in phagolysomal vesicle of alveolar macrophages

Clinical course: causative agent of Legionnaire’s disease [Legionellosis]

Atypical pneumonia à high fever, headache, nonproductive cough

Other infections à wounds, pericarditis, GI (V/D)

Virulence Factors

Cytotoxin: metalloprotease

Iron scavenging system

Pili

Macrophage infectivity protein [ability to multiply in macrophages]

Motile

DX: culture specimen on selective media (charcoal yeast agar)

IFA
Ab titers to determine serotypes

TX: AB [tetracyclines, erythromycin, ciprofloxacin]

Prevention: chlorinate water (humidifiers, spas, whirlpools, showers, water lines)

BRUCELLOSIS [Bang’s Disease]

Brucella genera (part of the alpha proteobacteria phylum and the Rhizobiales order)

G(-) small pleomorphic coccobacillus

Non motile, non sporeforming

Strict aerobes, some require CO2

capsule

Slow growth on media [days to weeks]

BICH tests

Oxidase (+) and catalase (+)

Reduce nitrate to nitrite

Urease (+)

Citrate (-)

MR (-)

6 species

B. abortus, B. canis, B. melitensis, B. neotomate, B. ovis, B. suis

Not part of normal human flora

Reservoir: animal carriers = Zoonotic disease

Transmission: direct contact with secretions / excretions of infected animals

(i.e raw milk, unpasteurized cheese, aborted placentas)

Incubation: 2 weeks [+/- 1 week]

Clinical course: general malaise, fever headache

Recurring [undulant] fever

Increased size of lymphatic organs [splenomegaly, hepatomegaly]

Eventually leading to anorexia à weight loss à abd pain, joint pain

Animals with disease = à abortion

Virulence Factors:

Phage transduction

Can survive in macrophages for monthsà granulomatous nodules

DX: Serology of biovars (Ab titer)

Culture organism from fluid on special blood enriched media and CO2 environ

ELISA

TX: AB [doxycycline, TMPS]

Prevention: protection when handling carcasses

Test and eliminate (destroy) infected animal carriers

Vaccination for livestock