Clinical Microbiology

Prokaryotic Cell

Bacteria and Archaea

No Nuclear membrane

cell wall present

Asexual reproduction

1 Circular chromosome

70 s ribosomes

No organelles

Eukaryotic Cell

Membrane bound

No cell wall

Sexual/asexual reproduction

Linear chromosomes

80s chromosomes

Organelles (mitochondria, Golgi bodies, Rough/smooth ER)

Virus

Neither pro nor euk

Obligate intercellular parasites that are inert outside living host

Cellular tropism (cell type specific)

Bacterium

Reproduce Asexually by binary fission

80-90% water

Need carbon, nitrogen, and energy source

Halophilic bacteria

Need salt for growth

Fungus

Cell walls made of chitin

Uni-multicellular

Uni- Yeasts

Most typical multi - Molds

Some do both (Yeast → Mold)

Parasite

Multicellular - Helminths

Protozoa - Uniicellular

Helminths

Nematodes

Cestodes

Trematodes

Protozoa

Amoebas

Flagellates

Sporozoa

Ciliates

Obligate Aerobe

Require O2

Facultative Anaerobe

Grow with or without O2

Better with O2

Capnophile/microaerophile

Grow better when atmosphere enriched with extra CO2

Obligate anaerobes

O2 = toxic

Will not grow in presence of O2

Gram +

Stain purple

Thick Peptidoglycan

Teichoic acid present

Gram -

Stain Pink/red

Thin peptidoglycan

Outer lipopolysaccharide (LPS)

• Lipid A (endotoxin)

Acid-fast

AFB = Acid fast bacilli

Waxy layer over gram positive bacilli structure

Describe Staphylococcus spp.

Gram+ Cocci in clusters

Catalase Positive

THE Coag-positive staphylococcus

Staphylococcus aureus

Coag Negative Staphylococcus

Staphylococcus epidermidis

Staphylococcus saprophylicus

Streptococcus and Enterococcus

Gram+ cocci in chains

Catalase negative

Types of hemolysis

Alpha : green/brown zone due to partial RBC lysis

beta: clear/colorless zone due to complete RBC lysis

Gamma: no hemolysis

Beta-hemolytic Streptococci

Streptococcus pyogenes (Group A Strep)

Streptococcus galactiae (Group B strep)

Alpha-hemolytic Streptococci

Viridans group Streptococcus spp.

• Viridans means green

Streptococcus pneumoniae

Significant Enterococcus Species

Historically, group D streptococci

Enterococcus faecalis

Enterococcus faecium

Anaerobic Gram+ Cocci

Obligate anaerobes

• Finegoldia magna

• Peptostreptococcus spp.

Spore Forming Aerobic Bram+ Bacilli

Bacillus cereus

Bacillus anthracis (Anthrax)

Spore Forming Anaerobic GPB

Clostridium perfringens

Cl. Botulinum

Cl. Tetani

Clostridioides difficile

Non-spore Forming Aerobic GPB

Listeria monocytogenes

Corynebacterium diphtheriae

Gardnerella vaginalis

Novartis spp.

Non-spore Forming anaerobic GPB

Cultibacterium acnes

Actinomyces spp.

Lactobacillus spp.

GNDC (Gram- diplococci) means what?

Neisseria spp.

Significant GNDC

Neisseria gonorrhoeae

Neisseria meningitidis

Moraxella catarrhalis

Characteristics of the Enterics

Non-sporeulating, facultative anaerobic, Gram- rods

Ferment Glucose

Reduce nitrates to nitrites

Do no produce cytochrome oxidase

What is Oxidase

A test for the cytochrome c oxidase enzyme.

10-15 sec deep purple is a positive test

Two categories of Enteric Pathogens

Opportunistic pathogens

Primary or “true” pathogens

Opportunistic pathogen examples

Escherichia spp.

Klebsiella spp

Enterobacter spp.

Citrobacter spp.

Serratia spp.

Proteus spp.

Primary pathogen examples

Escherichia coil O157:H7

Salmonella spp.

Shigella

• Dirty - dysenteriae

• Fingers - flexneri

• Bring - boydii

• Shigella - sonnei

Yersinia pestis

Yersinia entereocolitica

Genus Vibrio characteristics

Facultative anaerobes

Curved Gram- bacillus

Oxidase positive

Significant Vibrio Spp.

Vibrio cholera

Vibrio vulnificus

Vibrio Parahaemolyticus

Curved GNRs

Campylobacter jejuni

Helicobacter pylori

Non-Fermenter Characteristics

obligate aerobes

High intrinsic resistance to antibiotics

Significant non-fermenters

Pseudomonas aeruginosa

• oxidase positive

Acinetobacter spp.

• Gram- coccobacilli

• Oxidase. Negative

Strenotrophomonas maltophilia

Burkholderia spp.

Fastidious GNB characteristics

Hard to grow

Won’t grow on MacConkey agar

Haemophilus (common fastidious genus) characteristics

Pleomorphic coccobacilli or bacilli

Only grows on chocolate agar

Significant Haemophilus species

Haemophilus influenzae

Haemophilus parainfluenzae

Haemophilus ducreyi

Important fastidious GNBs

Bordetella pertussis

Bordetella parapertussis

Legionella pneumophila

Brucella spp.

Francisella tularensis

Pasteurella multocida

Significant Anaerobic GNB

Bactericides fragilis group

Prevotella spp.

Porphyromonas spp.

Fusbacterium spp.

• Fusiform: tapered at each end

Genus Chlamydia is

Significant Chlamydia spp.

Chlamydia trachomatis

Chlamydia Psittaci

Chlamydia Pneumoniae

Other Intracellular Bacteria sig spp.

Rickettsia rickettsii

Rickettsia typhi

Rickettsia prowazekii

Ehrlicia spp.

Anaplasma spp

Coxiella burnetii

Cell Wall lacking bacteria genera

Mycoplasma

Ureaplasma

Lacking a cell wall prevents Mycoplasma and Ureaplasma from ___ and provides ___ resistance

Staining

Cell wall active antibiotics

Spirochete Characteristics

Spiral shaped

Gram-

Periplasmic flagella (axial filaments)

Spirochete Characteristics

Spiral shaped

Gram-

Periplasmic flagella (axial filaments)

Significant spirochete Genera

Borrelia

Leptospira

Treponema

Borrelia characteristics

Can be seen in light microscopy

• not visualized via gram stain

Borrelia sig spp.

Borrelia burgdorferi

Borrelia recurrentis

Leptospira Characteristics

Cannot be seen with light microscopy

Most common zoonosis

Leptospira Sig spp

Leptospira interrogans

Treponema characteristics

Very thin

Can be seen with dark field microscopy

Treponema sig spp.

Treponema pallidum

Acid Fast Bacilli Mycobacteria Characteristics

Does not gram stain

Obligate aerobes

Slow growing in culture

Acid-fast (waxy outer cell wall layer made of mycolic acid)

Acid fast bacilli mycobacteria categories

Tuberculosis

Non-tuberculosis

Leprosy causing

Tuberculosis spp

Mycobacterium tuberculosis

Mycobacterium bovis

Non Tuberculous Mycobacteria spp.

Mycobacterium Adium-intracellulare complex

Mycobacterium kansasii

Mycobacterium marinum

Mycobacterium scrofulaceum

Leprosy Causer

Mycobacterium leprae