MM Midterm 2 Part 2 (10/23-11/02)

How is the gram negative outer membrane a contributor to host inflammatory responses?

Gram negative bacteria has a thin peptidoglycan layer protected by a thick lipopolysaccharide layer (LPS). That LPS is recognized by host defenses and caused inflammatory responses

What’s neisseria meningitidis?

A gram (-) diplococcus bacteria that colonizes the human nasopharynx. It’s contracted by inhalation or throat secretions

What’s the critical event that could lead to N. menigitidis causing disease sinc it can be commonly carried without symptoms in the nasopharynx?

The transition from colonization to the bloodstream invasion is the critical event that can lead to severe disease. This bacteria can attach to epithelial cells and penetrate the epithelial surface

How are N. menigitidis able to survive in the host?

They make capsules that reduce effective complement clearance

Describe N. gonorrhoeae (NG)

It is a gram (-) diplococcus in the same group as menigitdis and it infects the mucosal surfaces of the reproductive tract, rectum and phraynx. It can cause localized or disseminated infection. Contracted from sexual contact

What are the virulence strategies for NG?

Adhesion to mucosal cells, antigen variation and immune evasion

What’s the difference between local and dissemination infection?

Local = most common and its associated with pain one region, like infection in the throat

Dissemination = less common and can occur in the entire body, leading to things like arthritis

What’s haemophilus influenzae (HI)?

Small gram (-) coccobacilus that can colonize the upper respiratory tract. It has both encapsulated and non-encapsulated strains

What are capsuled and non capsuled strands of HI?

Encapsulated = Bacteria that has a capsule virulence factor and it can cause invasive disease like meningitis, bacteremia and epiglottis

Non-encapsulated = Bacteria that uses adhesion and mucosal persistence as a virulence factor and it often causes localized respiratory disease like ottis media, sinusitis and other respiratory infections

There are ___ that are capsule-targeting and they stimulate protective antibody responses that promote opsonization and phagocytic clearance

conjugate vaccines

What parts of the immune system are important for conjugate vaccines?

There are T-dependent activation of B cells and that allows for protein antigen and high affinity antibodies

T-independent activation = polysaccharide antigen and low affinity antibodies

What’s Bordetella pertussis?

A bacteria that attaches to ciliated respiratory epithelium and produces toxins that impair mucociliary defenses

What toxins do BP produce?

Pertersuasis toxin (PT), Adenylate cyclase toxin (ACT), and trachea cytotoxin (TCT)

What diseases can BP cause?

Disease without deep tissue invasion like whooping cough or kennel cough in dogs

Explain legionella pneumophilia

It’s a microbe that can invade water systems (like cooling towers, showers, hot tubs, etc) and cause severe respiratory infections

What’s a way that LP survive?

They can survive and replicate within macrophages because they are intracellular pathogens. While in the macrophage they modify phagosome which prevents fusion with the lysosome

What’s the useful specimen and diagnostic approach for all the bacteria?

Meningococcal meningitis: CSF and blood/ Gram stain, culture, PCR

Gonorrhea: Genital, rectal, or pharyngeal specimen/ NAAT, culture when indicated

HI: Blood or CSF/ Culture, PCR

Pertussis: Nasopharyngeal specimen/ PCR, culture

LP: Lower respiratory specimen (urine)/ PCR and/or culture, urinary antigen testing

How can bacteria associated with the intestinal tract cause diseases ranging from mild diarrhea to severe systemic infections?

Different virulence strategies, tissue interactions and host responses can lead to very different clinical outcomes

What are the types of enteric gram (-) bacteria?

E. coli, salmonella, shigella, and V. cholerae

What are the types of E.coli?

Commerisal E. coli = normal intestinal colonization

Diarrheagenic E. coli = gastrointestinal disease

Extraintestinal pathogenic E. coli = UTI, bloodstream infection and other invasive infections

What is the virulence of enterotoxigenic E. coli?

It attaches to the intestinal epithelium and produces enterotoxins (LT/ST). It then alters ion transport, causing increased intestinal fluid secretion, resulting in watery diarrhea

How is Shiga Toxin producing E. coli virulent?

It produces a shiga toxin after colonization of the intestinal epithelium and once it enters the bloodstream, it damages the endothelial cells causing microvascular injury

Causes bloody diarrhea and sometimes hemolytic uremic syndrome

How is salmonella enterica virulent?

It’s an intracellular pathogen that can survive in macrophages, promoting persistence and dissemination

Exposed through eating contaminated food

What are the two clinical patterns of salmonella?

Nontyphoidal salmonella - gastroenteritis (inflammation and diarrhea)

Typhoidal salmonella - systemic disease (enteric fever)

How is the shigella species spread?

Through fecal or oral route

What’s the difference between watery and inflammatory diarrhea?

Watery = altered fluid transport increased in intestinal secretion. Bacteria that cause it include enterotoxic e. coli and V. cholerae

Inflammation = mucosal injury and host inflammatory response, it can contain blood or mucous. Bacteria that cause it include shigella and nonytophodal salmonella

How is v. cholerae virulent?

It’s a bacteria that causes extreme fluid loss without extensive invasion, it creates the toxin cololera (CT) disrupting the intestinal ion transport

How is klebsiella pneumoniae virulent?

It has a polysaccharide capsule that allows it to be resistant

Why does mycobacteria require specialized staining methods?

It is rod shaped and has a complex lipid rich cell envelope containing mycolic acids that make the conventional gram staining less useful

How does the mycobacteria lipid envelope influence bacterial physiology?

It limits permeability to many antimicrobial drugs, contributes to persistence and resistance to host defenses and influences how the bacteria interact with the immune system

T or F: Acid-fast staining is useful for detecting mycobacteria and M. tuberculosis

False, it identifies only mycobacteria