Bug Parade: Gram Negatives

Moraxella catarrhalis reservoir

upper respiratory tract

high colonization rates in children

Moraxella catarrhalis virulence

disease strains have greater b-lactamase production than commensals

Able to "survive" b-lactam Rx for other upper respiratory pathogens

Moraxella catarrhalis diseases

lower respiratory tract

otitis media

sinusitis

ocular infections

Moraxella catarrhalis growth/screens

-Growth on blood, chocolate

-Does NOT grow on MacConkey

-Colony moves like hockey puck

Moraxella catarrhalis identification

Oxidase positive

Catalase positive

b-lactamase positive

butyrate esterase positive

doesn't eat sugar

Neisseria gonorrhoeae reservoir

Humans are only reservoir

(Mucosa of urethra, cervix, rectum, pharynx, eyes)

Neisseria gonorrhoeae virulence

Lipooligosaccharide (LOS) antigenic variation increases adherance and decreases humoral immunity

pili and opacity proteins modulate attachment

Neisseria gonorrhoeae diseases

Gonorrhea (urethritis, cervicitis, disseminated)

Complications of epididymitis and pelvic inflammatory disease

Ophthalmia neonatorum (eyes in newborns)

Rectal, pharyngeal infection often asymptomatic

Neisseria gonorrhoeae growth/screens

-Grows on chocolate

-Grows on Thayer Martin

-Does NOT grow on blood

-Intracellular (neutrophil) -gram negative diplococci (GNDC), male swab in urethra and identify right away

Neisseria gonorrhoeae identification

Oxidase positive

Catalase positive

Gamma-glutamyl-aminopeptidase-negative

Glucose positive

Neisseria meningitidis reservoir

Humans are only reservoir

Normal flora and pathogen

Neisseria meningitidis virulence

Droplet secretions (repeated close contact)

Anti-phagocytic capsule (13+ types)

Neisseria meningitidis diseases

Invasive disease: meningitis, acute sepsis (high mortality having both)

Complement deficiency, asplenia risk factors

Sequelae may occur

Rare: pneumonia, septic arthritis

Neisseria meningitidis growth/screens

Growth on blood, chocolate, Thayer Martin

Neisseria meningitidis identification

Oxidase positive

Catalase positive

Gamma-glutamyl-aminopeptidase positive

Glucose positive

Maltose positive

gram negative diplococci

Moraxella catarrhalis

Neisseria gonorrhoeae

Neisseria meningitidis

Haemophilus influenzae reservoir

Commensal in mucous membrane (upper RT)

Non-typeable: colonize 90% of people

Type B: colonization has been reduced (type based on capsule)

Haemophilus influenzae virulence

-Antecedent virus infection causes inflammation and damage to mucosa

-Enters bloodstream

-Type B capsule is resistant to phagocytosis

Haemophilus influenzae diseases

Invasive: bacteremia, meningitis, epiglottis due to Type B

Nontypeable: conjunctivitis, otitis media, pneumonia, acute exacerbation of chronic bronchitis (often secondary to a viral infection)

Haemophilus influenzae growth/screens

-Growth on chocolate

-No growth on blood or MacConkey

-Can satellite around staphylococci to grow on blood

Haemophilus influenzae identification

X and V growth requirement

Negative porphyrin test

Gardnerella vaginalis reservoir

Anorectal microbiome of both genders

Normal vaginal flora in women of reproductive age

Loves pH between 6-7

Gardnerella vaginalis diseases

Bacterial vaginosis: cascade of events relative to lactobacillus depletion

Can complicate pregnancy: chorioamnionitis, premature rupture of membranes, pre-term birth

Gardnerella vaginalis growth/screens

-very tiny on blood agar

-Gram-negative (variable) coccobacilli

-Hippurate hydrolysis

Gardnerella vaginalis identification

Be careful on culture:

Should not use culture to identify bacterial vaginosis

Clue cells

Molecular diagnostics

Pasteurella reservoir

P. multocida: nasopharynx and gingiva of cats

P. canis: nasopharynx and gingiva of dogs

Pasteurella diseases

Bite wound infections very rapid spread of erythema and/or inflammation

Less common: pneumonia or systemic disease

Pasteurella growth/screens

-Growth on blood and chocolate

-No growth MacConkey

-Can satellite around staphylococci

Pasteurella identification

Oxidase-negative

"sick TSI"

Penicillin susceptibility

Gram negative coccobacilli

Haemophilus influenzae

Gardnerella vaginalis

Pasteurella

Enteric gram-negative bacilli virulence

Endotoxin (LPS)

Adhesion, invasion molecules

Many with urease production

ESBL: extended-spectrum b-lactamase

CRE: carbapenem-resistant Enterobacterales

SPICE bugs: inducible AmpC B-lactamase

Enteric gram-negative bacilli diseases

-UTIs

-Intra-abdominal infections

-Skin and soft tissue infections

-Pneumonia

-Bloodstream infections

-Gastroenteritis

Enteric gram-negative bacilli therapy

Most drug classes with activity

NOT:

Macrolides

Vancomycin

Clindamycin

Penicillin

Metronidazole

Enteric gram-negative bacilli identification/characteristics

-Gram negative

-Ferment glucose

-Facultative

-Growth on routine media

-Non-spore forming bacilli

-Reduce nitrate to nitrites

-Oxidase negative

Enteric gram-negative bacilli

Escherichia coli

Klebsiella

Proteus

Serratia

Providencia

Morganella

Citrobacter

Enterobacter

Escherichia coli characteristics

Lactose fermentation

Voges Proskauer negative

Many beta- hemolytic

Indole positive

Klebsiella characteristics

Lactose fermentation

Vogues Proskauer positive

Nonmotile

Capsule

Ornithine-negative

Proteus characteristics

No lactose fermentation

Phenylalanine-positive

May swarm

H2S positive

Urease positive

Serratia characteristics

Citrate only C source

Gelatin hydrolysis

DNAse positive

Providencia characteristics

No lactose fermentation

Phenylalanine-positive

Citrate positive

H2S negative

Morganella characteristics

No lactose fermentation

Phenylalanine-positive

Indole-positive

Citrate negative

H2S negative

Citrobacter characteristics

Late lactose fermentation

Citrate sole carbon source

Indole or H2S; Odor

Enterobacter characteristics

Lactose fermentation

Oxidase negative

Vogues Proskauer-positive

Cefazolin resistant

Ornithine-positive

Motile

Enterobacterales that are lactose fermenters

Escherichia

Klebsiella

Enterobacter

Enterobacterales that are non-lactose fermentative

Citrobacter

Serratia

Proteus

Providencia

Morganella

non-typhoidal salmonella characteristics

-Non-lactose fermentation

-Growth on highly selective agar

-H2S-positive (black colonies)

-Urease-negative

-Phenylalanine-negative

-Can decarboxylate lysine, arginine, and ornithine

-Co #1 bacterial pathogen

-motile

salmonella serotype typhi characteristics

-Non-lactose fermentation

-Growth on highly selective agar

-H2S-positive (crescent ring)

-Urease-negative

-Phenylalanine-negative

-can decarboxylate lysine (NOT arginine or ornithine)

-typhoid fever

-motile

shigella characteristics

-Non-lactose fermentation

-Growth on selective agar

-H2S-negative

-Urease-negative

-non-motile

-#3 bacterial GI pathogen

-transmission: fomites, fingers, fleas, feces

campylobacter jejuni

-Oxidase-positive

-Microaerophilic (5% O2)

-Hippurate-positive

-42°C (warmer than body temp)

-Selective medium

-found in poorly stored food

-gull-winged bacilli

-watery colonies

-Co #1 bacterial GI pathogen

vibrio characteristics

-Oxidase-positive

-Tolerates 6% NaCl

-Thiosulfate citrate bile salts sucrose (TCBS) agar

-curved bacilli

V. cholerae: pandemics; munches on sucrose (yellow)

V. parahaemolyticus: #1 Vibrio in US (seafood)

V. vulnificus: #1 Vibrio cause of death in US

Heliobacter pylori characteristics

-Screening: serology (IgG)

-Diagnosis: surgical pathology, CLO test, urea breath test

-Test of cure: stool antigen test, urea breath test

-Mega urease-producer (CLO test hot pink)

-can cause gastritis, peptic ulcer disease, gastric cancer, and gastric MALT lymphoma which can be treated with antibiotics

GI pathogens

Salmonella (non-typhoidal and typhi)

Shigella

Campylobacter jejuni

Vibrio

Heliobacter pylori

non-fermentative bacilli

Pseudomonas aeruginosa

Stenotrophomonas maltophilia

Acinetobacter

Pseudomonas aeruginosa reservoir

Broad range of habitats

Most grow as biofilms on surfaces

Pseudomonas aeruginosa virulence

LPS, exotoxin, biofilm

Transform to mucoid isolates (CF patients)

Survive with minimal nutrients

Pseudomonas aeruginosa diseases

Invasive disease in neutropenic patients

Ventilator-associated pneumonia

Burn and diabetic wounds

Otitis externa (swimmer’s ear)

Keratitis

Pseudomonas aeruginosa growth

Can be B-hemolytic

Can be mucoid

Can be metallic

Grow on blood, chocolate, MacConkey

Grape Kool-Aid odor

Maybe corn tortilla chips

Pseudomonas aeruginosa identification

Oxidase-positive

Indole-negative

Grows at 42C

Stenotrophomonas maltophilia reservoir

Environment (soil and water - problematic for hospitals)

Stenotrophomonas maltophilia virulence

Opportunist

Risk factors for S. maltophilia mortality:

-ICU

-age >40

-pulmonary source

-resistance to anti-Pseudomonas therapeutic options

Stenotrophomonas maltophilia diseases

Trauma secondary to farm accidents

Immunocompromised and ventilator patients in ICU

Neutropenic patients

Bacteremia

#2 in CF pneumonia

Stenotrophomonas maltophilia growth

Yellow pigment

Grow on blood, chocolate, MacConkey

Odor - grandma's basement

Stenotrophomonas maltophilia identification

Oxidase-negative

Acid from oxidative utilization of maltose, glucose

DNAse-positive

Biochemical battery

Acinetobacter reservoir

Soil and water, sewage, food

Human specimens

Acinetobacter virulence

Can form biofilms

Many strains are highly resistant to antimicrobial agents

Acinetobacter diseases

Colonization believed to occur more than disease

A baumannii complex:

-VAP, BSI with high morbidity and mortality in ICU

-Iraqibacter (skin and soft tissue infections)

Acinetobacter growth

Non-motile "A-cineto"

Growth on blood, chocolate, MacConkey

Acinetobacter identification

Oxidase negative

Biochemical profiling

Non-glucose fermenter

Fastidious bacteria

Legionella pneumophila

Bordetella pertussis

Chlamydia trachomatis

Chlamydia pneumoniae

Chlamydia psittaci

Mollicutes

Legionella pneumophila reservoir

Natural bodies of water

Higher concentrations in stagnant water

Symbiosis and multiplication within amoeba

Legionella pneumophila virulence

Infection acquired by aerosol inhalation of contaminated water

Infects macrophages and resides in phagosomes

Affect host cell death and release of organisms

Legionella pneumophila diseases

Unusual case of pneumonia (10,000 to 20,000 in US)

Underestimated incidence

Risk factors:

-suppression of CMI

-smoking

-corticosteroids

Legionella pneumophila growth

Specimen treatment to reduce contaminants

Growth on Buffered Charcoal Yeast Extract (BCYE)

No growth on blood

Carbolfuchsin counterstain

We’re bad at growing this

Legionella pneumophila identification

Ground glass (opal-like) colonies

Suspect colonies are subculture to BCYE and blood

Urine antigen testing in severe illness

Stains faintly

Bordetella pertussis reservoir

Humans (carry)

Kids often get it from patents

Teenagers (due for boosters)

Bordetella pertussis virulence

ID: 100 organisms (low!!)

90% transmission rate to susceptible hosts

Toxin destroys cells of mucociliary escalator (hard for cells to regenerate: takes a while)

“100-day cough”

Bordetella pertussis diseases

Pertussis (vaccine-preventable illness; runs in 2–5-year cycles)

Three Stages of Pertussis:

Catarrhal phase (runny nose, sneezing, cough)

Paroxysmal phase (spasmodic cough/whoop, post-tussive vomiting)

Convalescent phase (may last months)

Bordetella pertussis growth

Must use nasopharyngeal swab

Cultivation on Bordet-Gengou; Regan-Lowe

Bordetella pertussis identification

Molecular diagnostics in test of choice

May try to culture for typing/epidemiology studies

Chlamydia trachomatis reservoir

Humans

(More common STD than gonorrhea)

Chlamydia trachomatis virulence

“wedding crasher”

Drives its own replication and release (reticulate, elementary bodies) and its own protection (persistence in means of evading immunity)

Chlamydia trachomatis diseases

Diseases based on 18 different MOMPs:

4 MOMPs: trachoma (blindness)

10 MOMPs: genital (cervicitis, urethritis, PID, endometritis, salpingitis, epididymitis)

4 MOMPs: lymphogranuloma venereum (ulcerative form; systemic STD)

Chlamydia trachomatis growth

Old: cell cultures (host cells) with mAb; staining of CPE: cytopathic effect

-takes a while, expensive

Now: shell vial culture with "blind" mAb staining

-takes 2 days

Chlamydia trachomatis identification

Molecular diagnostics (look for nametags)

Chlamydia pneumoniae reservoir

humans

Chlamydia pneumoniae virulence

Associated with community-acquired pneumonia (10-15%)

Symptoms non-specific (like virus)

Chlamydia pneumoniae diseases

Shell vial culture

Serology should be acute and convalescent (due to seroprevalence)

Molecular not ready for prime time

Chlamydia psittaci reservoir

Psittacine birds (parrots)

Poultry (ducks, turkeys)

Chlamydia psittaci virulence

Infectious forms shed: remain viable for months

Inhalation of aerosols

Direct contact with infected bird, fecal, or feather dust

Chlamydia psittaci diseases

Mild illness to severe pneumonia

Endocarditis

10 in US per year

Practice hygiene and quarantine birds

Mollicutes characteristics

Smallest free-living microbes capable of replication

Small genome

no cell wall

tri-layer cell membrane, making it not sucesptible to many antibiotics

Mollicutes diseases

M. pneumoniae: walking pneumonia

M. genitalium: STD

Mollicutes growth

Don't grow on blood

Very SLOW growers

Serology can be cross-reactive between species