Microbio Exam 1

acellular infectious agents

prions, viruses, viroids

cellular microorganisms

prokaryotes and eukaryotes

prokaryotes

archaea, bacteria

eukaryotes

algae, fungi, protozoa

sp.

one unspecified species in a genus

spp.

multiple species in a genus

microbe when not harmful is a

nonpathogen

microbe when harmful is a

pathogen

pathogen in the host is a

infectious disease

pathogen when consumed is a

toxin -> microbial intoxification

Leeuwenhoek

first described living microorganisms using simple microscopes

microbiology moved from

observation to experimentation to linking organisms with disease

Pateur

provided experimental support for germ theory

Koch

developed a systematic framework for linking specific microorganisms to specific diseases

Infection

involves the microorganism in the host, may be asymptomatic

Intoxificiation

results from exposure to a microbial toxin

Infectious disease

- pathogen establishes itself in a person's body

- the pathogen causes a disease

Microbial Intoxification

- a pathogen produces a toxin in vitro (outside living host)

- a person ingests the toxin. the toxin causes a disease

- ex. food poisoning

Resident microbiota

Indigenous microbiota -> coexist with host -> may cause disease when conditions change

What conditions support indigenous microbiota becoming opportunistic?

- Different or normally sterile body site

- Disrupted protective barrier (e.g., skin breakdown)

- Altered microbiota or overgrowth

- Weakened host defenses (e.g., immunocompromised patient)

What resident microbiota would you normally expect: ears and eyes, mouth and upper respiratory tract, skin, GI tract, geniourinary tract

ears and eyes: skin-like microbiota, few microbes

mouth and upper respiratory tract: many microbes; oral strep and anaerobes

skin: bacteria and fungi, staph. spp. common

GI tract: colon has the most # and variety of microbes

genitourinary tract: distal urethra and vagina contain microbiota, bladder and kidney's usually sterile

Can microbes normally present here sometimes cause infection?

Yes, some members of the normal microbiota can become opportunistic and cause infection when conditions change

What might create an opportunity for infection?

wrong body site, disrupted barrier, altered microbiota, weakend host defense

Ms. Rivera's admission MRSA nasal screen is positive. She has no signs or symptoms of infection. What does this result most likely indicate?

Colonization

Why might Ms. Rivera be screened for MRSA even though she has no symptoms?

To identify colonization for infection-prevention measures

Specimen quality matters

collect from the correct site, use the correct technique, and transport according to lab instructions

Roles of Microbes

Ecosystems: decomposition, nutrient cycling, food webs

Human body: microbiota, digestion, colonization resistance

Food and industry: fermentation, biotechnology

Medicine: antibiotics, vaccines, models of cells

Microbes can be

beneficial, harmful, or neutral depending on context

Why study microbiology in nursing?

Specimen collection, transmission prevention, antimicrobial use, aseptic technique, infection control

Staph. spp. from intact skin swab

expected microbiota: usually on skin

E. coli in colon microbiota

expected microbiota: colon has most microbes

E. coli in urine with dysuria and fever

concerning for infection: e. coli should not be in urine and signs and symptoms

Common skin bacteria found in only one of two blood culture sets

Possible contamination: only in one of two

S. aureus in blood culture

Concerning for infection: blood should be sterile

Ms. Rivera's urine culture grows E. coli. Which findings increase concern for an active UTI?

Dysuria, new urinary frequency/urgency, new suprapubic pain or pressure, fever or chills

Microbes are

microscopic (nanometer)

1 meter

100 centimeters, 1,000 millimeters, 1 million micrometers, 1 billion nanometers

magnification

how much larger the image appears, makes the image bigger

resolution

how clearly two close objects can be seen as seperate, makes fine details clearer

Modern compound light microscope

view specimen not viewable to human eye in color

Electron microscopy

TEM vs SEM (good for looking at microbes)

Transmission Electron Microscope

T = Through (internal detail)

Scanning Electron Microscope

S = surface (external detail)

Prokaryotic vs Eurkaryotic

True nucleus

P: No

E: Yes

Membrane-bound organelle

P: absent

E: present

Ribosomes

P: present (smaller)

E: present (larger)

Examples

P: bacteria, archaea

E: fungi, protozoa, human cells

DNA

P: present, not in true nucleus

E: present in nucleus

Reproduction

P: binary fission

E: mitosis/meiosis

Prokaryotic cell: cell membrane

- selective barrier (homeostasis)

- many bacteria generate ATP across the cell membrane

- some antimicrobials disrupt the bacterial cell membrane (e.g., daptomycin)

Prokaryotic cell: bacterial cell wall

Shape and protection

contain peptidoglycan

Antibiotic target

Gram + vs. gram - differ

Cell walls

present in plants, algae, fungi, and most bacteria

peptidoglycan

A protein-carbohydrate compound that makes the cell walls of bacteria rigid

gram-positive structure

inner cell membrane with membrane proteins, thicker peptidoglycan, lipoteichoic acid and teichoic acid

gram-negative structure

inner and outer cell membrane with membrane proteins, thinner cell wall, lipopolysaccharides

Prokaryotic cell: capsule

- highly organized glycocalyx

- some capsules resist phagocytosis

- help bacteria evade host defenses

Prokaryotic cell: chromosome

- DNA molecule contains genetic info

- prokaryotic DNA has no nucleus

Prokaryotic cell: plasmid

- Extrachromosomal DNA

- Plasmids may carry antimicrobial-resistance genes (why they can't be treated with certain antibiotics

Prokaryotic cell: flagella

for motility -> colonization and pathogenesis

Types of flagellar arrangement

- peritrichous bacterium (all over bacteria)

- lophotrichous bacterium (multiple but only on one end)

- amphitrichous bacterium (two - one on each end)

- monotrichous bacterium (one - on one end)

Prokaryotic cell: fimbriae

- allows bacteria to attach to surfaces (adhesion)

- not used for motility

- adhesion -> colonization

Prokaryotic cell: sex pilus/pili

- enable DNA transfer btwn bacteria during conjugation

- may spread antimicrobial-resistance genes

Prokaryotic endospores

- highly resistant survival structure

- resist harsh environmental conditions + many disinfectants

- SURVIVAL STRUCTURE not a reproductive structure

- helps some bacteria persist in the enviornment

ex. bacillus, clostridium

Prokaryotic cell: slime layer

loosely attached glycocalyx (capsule = more organized and firmly attached to cell surface)

can promote surface attachment and contribute to biofilm formation -> persistence on tissues and devices (e.g., endotracheal tubes, catheters)

Biofilms

help microbes persist on tissues and devices

Binary fission: bacterial reproduction

dna replicates -> cell divides -> two daughter cells

A hospitalized patient develops watery diarrhea after antibiotic therapy. The nurse is preparing the room and patient care plan

relevant cues: after antibiotic therapy, watery diarhhea

likely concern: infection, dehydration, opportunistic pathogen

mechanism: signs of c. diff, antibiotic therapy, in hospital

priority actions: contact ppe, soap and water on hands to remove endospores, alert DR. (IV for rehydration, test for bactera), stool sample, give antibiotics

Microbial identity and location: why it matters clinically?

presence alone does not establish disease

Microscopy: why it matters clinically?

determines what can be seen and how clearly

Cell organization: why it matters clinically?

influences identification, virulence, treatment, and prevention

Microbes include

cellular organisms and acellular agents

Not all microbes

are pathogens

Microbiota vary by

body site

Microbial presence

does not automatically mean infection

Microbiota

Microorganisms normally present at a body site

Colonization

Microorganisms establish/grow without causing disease

Contamination

Microorganisms are unintentionally introduced into a

specimen, surface, or product

Infection

Microorganisms enter and multiply in the host; may or may not cause disease

Viron

complete virus particle, contains a genome surrounded by capsid, some have envelopes

nucleocapsid

genome + capsid

genome in virus

rna or dna -> helps determine viral classification and replication strategy

capsid

protein coat -> protects the viral genome; may participate in attachment/entry

envelope

outer lipid layer in some viruses -> affects release, survival, disinfection

virus vs cell

viruses have DNA or RNA (cells have both), lack energy production capacity, use host-cell ribosomes, do not divide - assemble inside host

enveloped virus

have an outer lipid membrane, often results from budding from host cell, can help virus attach to host, generally more vulnerable to disruption by detergents and disinfectants

Viruses must use

host-cell machinery to make more virus particle

Viral envelopes

influence survival and susceptibility to detergents and disinfectants

virus structure: genome

single-stranded RNA

virus structure: capsid

protein coat

virus structure: envelope

host-derived lipid membrane

virus structure: attachment

surface proteins

Not all viruses have _____, but all viruses contain

envelopes; a genome surrounded by a protein capsid.

How Are Viruses Classified?

• Genome: DNA or RNA

• Strand: single- or double-stranded

• Envelope: present or absent

• Capsid structure/shape

• Host or target cells

Animal Virus Multiplication: Overview

attachment, entry, uncoating, biosynthesis, assembly, release

nonenveloped virus enter host by

endocytosis

enveloped virus enter by

membrane fusion

Animal virus multiplication: release

Lysis

• Host cell breaks open

• Newly formed virions are released

Budding

• Virus exits through a host-cell membrane

• Some viruses acquire a lipid envelope during this process

Mr. Chen has influenza A. After the virus enters a respiratory epithelial cell, which statement best explains how new virus particles are produced?

It uses host-cell machinery to make and assemble new virions

latency

virus remains in host cells and may reactivate later (ex. chicken pox -> shingles)

oncogenic potential

some viruses are associated with cancer development (ex. hpv -> cervical, anal, vaginal, throat cancer)

Mr. Chen has a positive influenza A test and asks for antibiotics. Which response is most accurate?

Antibiotics are not effective against viral infections

Which structure is found in all viruses?

capsid

bacteriophage

virus that infects bacteria

Virulent phages

can cause lysis (lytic cycle)

temperate phages

can integrate viral genetic material into bacterial DNA (lysogenic cycle)