Chlamydia, Chlamydiophila, and Obligate Bacteria

• Chlamydia and Chlamydiophila are obligate intracellular parasites without peptidoglycan
• Borrelia is a Gram-negative spirochete
• Zoonoses are human diseases transmitted from animals

Chlamydia and Chlamydiophila

• Cause eye and lung infections, along with some sexually transmitted diseases
• Differ from Rickettsia as they are not closely related
• Lack normal peptidoglycan
• Chlamydia trachomatis: A bacteria that has LOS and is a gram-negative rod

Obligate Intracellular Bacteria

• Rickettsia, Chlamydia, and Chlamydiophila are obligate intracellular bacteria
• Rickettsia has a peptidoglycan cell wall while Chlamydia and Chlamydiophila do not

Chlamydia trachomatis

• Can make proteins and DNA
• Cannot produce its own ATP and must get it from human cells.
• Does not contain normal peptidoglycan, but has a cell wall somewhat sensitive to beta-lactams
• Causes urethritis, which is the most common sexually transmitted disease in the U.S.
  • Can lead to neonatal conjunctivitis and infant pneumonia in infants born to infected mothers
• Trachoma, an eye infection that can cause blindness
  • Urethritis can spread from mother to neonate
  • Infection can lead to conjunctivitis and infant pneumonia in neonates

C.trachomatis Urethritis

• About 2 million new cases in the US per year
• Infection of the urethra in both males and females causes pain and small discharge
  • Females are often asymptomatic but can still transmit the disease, acting as carriers
• Prevention: No unprotected sex and having a trustworthy partner
• Treatment: One dose of azithromycin (1 g oral), or 7 days of tetracycline, erythromycin, or fluoroquinolone

Trachoma

• Caused in part by C. trachomatis serovar trachoma strain

• About 2 million people in the Middle East and North Africa are blind from the infection

• Chronic disease that typically infects as a child develops scars on eyes and causes progressive eye damage

• Conjunctivitis also occurs due to trachoma

• Infection causes conjunctivitis first, leading to small scars on the conjunctiva (inside of the eyelid)

• Scars scratching the eye surface may cause further eye damage and scarring

• Further damage to the conjunctiva leads to a turning in of the eyelashes, causing much more damage to the eye every time a person blinks

• Scarring of the cornea leads to blindness

• Dusty, sandy areas tend to develop the disease

  • There is increased grit in the eyes in these areas

• Spread by a variety of routes from infected children: droplets, hands, nose, clothing, towels, and flies

Trachoma: Prevention and Treatment

• Transmission can be reduced by washing the face and hands frequently, using clean towels and clothing, treatment of carriers, and lowering the amount of flies around
• Treat early with antibiotics before damage to the eye occurs, both topically and orally
• Effective antibiotics include azithromycin, tetracyclines, and fluoroquinolones

Zoonoses

• Animal diseases that can be transmitted to humans
• Both wild and domestic animals are living reservoirs of microorganisms that can cause human diseases
• Diseases that occur primarily in animals and can be transmitted to humans are zoonoses
• Examples: influenza, West Nile virus, rabies, Ebola, bubonic plague (vector of fleas), anthrax, salmonellosis, Rocky Mountain Spotted Fever, Typhus, malaria, and toxoplasmosis
• Zoonotic Coronaviruses:
  • SARS-CoV-1: Transmitted from civet cats to humans; ecological origin is bat
  • MERS-CoV: Camels transmit it to humans
  • SARS-CoV-2: Believed to have originated in bats, but the intermediate animal host or zoonotic source has not yet been identified

Lyme Disease

• A zoonotic disease that is explored within the lecture

• Borrelia bergdorferi is the infectious agent

• Borrelia is a Gram-negative spirochete, similar to a spirillum shape with more tight turns

• Mice and deer act as reservoir hosts, but the transmission occurs through Ixodes tick bites

• Found in Northeast U.S., Upper Midwest, Pacific West, and Texas

• 15,000 cases reported per year in US

• Disease symptoms: vary and difficult to diagnose

  • Erythema migrans develop 3 to 30 days after the bite with a flat red border, central clearing, with or without bull's eye, 5 to 50 cm diameter

• First phase: malaise, severe fatigue, fever, chills, and a body ache for several weeks

• Second phase: arthritis, meningitis, and heart problems; decreased concentration & irritability are possible when patients are untreated

• Neurological complications: varying degrees of permeant joint or nervous system damage, but long term effects are controversial

• Lyme disease: Can be prevented by avoiding ticks by using insect repellents, wearing long pants, and using socks as well as making frequent body pest checks

• Reduce tick numbers in your yard with the correct insecticide in areas with lots of ticks

• Prevents more serious late symptoms by early treatment

• Can be treated with amoxycillin, tetracycline or cephalosporins

Rickettsia, Ehrlichia, & Coxiella

• Very small Gram-negative rods and intracellular parasites
• RMSF incidence rates is highest in certain areas, according to the CDC of 2002
• Are Gram-negative rods
• Bacteria are obligate intracellular parasites able to grow in mammalian and arthropod cells
• Rickettsia &ehrlichia make protein on their own
• Make ATP via the TCA cycle, but use cellular ATP if available
• Rickettsia & Ehrlichia die quick outside of host cells
  • Coxiella can survive desiccated for moths to years

Rickettsia

• The spotted fever group can be from RMSF and is the most common in the United States
• The typhus group comes from Rickettsia
  • It does no come from Salmonella Typhi (typhoid)

Rocky Mountain Spotted Fever (RMSF)

• The common disease comes from rickettestia,
• Caused by Rickettsia rickettsii
• Disease is caused by blood leaking vessels, hypovolemia & organ failure
• Death rate as high as 20% (untreated).
• A host is a organism supporting growth of pathogen
• Vector: aids int transmission of pathogen from the reservoir to the host (eg. tick in RMSF)
• RMSF =400 to 2,000 cases per year in US mostly in Atlantic states and Oklahoma, Missouri and Arkansas
  • The reservoir and water are ticks:to infect a person the trick has to remain attached for >6 hours symtoms appear 10 days later
  • Fever , Chills, headache, myalgia, A rash that usually develops on extremities and spreads to trunk
• Diagnosed by symtom history: IFA antibody presence test is best if you can wait 2-3 weeks Treated wiuth tetracyclines
• There is non spesific symptons with RMSF as well as a rash that may not appear Patients may for get to mention tick exposure. Pharmasits can play a big part in treat,eat by keeping track or rashes No vaccine but prevent by avoiding ticks

Typhus

• Typhus =headache, joint pain, fever, cough epidemic (Rickettsia prowazekii; lice are vector, humans are reservoir) Endemic (Rickettsia typhi; rat flea, mouse flea is vector, rodents, opossums and cats are reservoir) About 10 to 70 cases of Murine Typhus per year in South Texas, also in S. California which comes from fleas.

Ehrlichiosis

• Caused by Ehrlichia from vector is tick, Bacterium grows in phagocytes, Reservoir: rodents, deer & dogs, similiar to RMSF

Q Fever

• Caused by Coxiella burnetii; not really closely related to *Rickettsia
• But, Gram-neg rod, obligate intracellular parasite, associated with ticks Spreads to humans generally by inhalation of particles, not tick bite - From birth of cats, dogs, goats, sheep (in placenta and fluid) diagnosed by history

Learning objective

• understands bacterial peptidoglycan cell wall layer synthesis
• Understands how antibiotics work by inhibiting the bacterial peptidoglycan cell wall layer synthesis

Antibiotics

• either killing bacteria (bactericidal) or stopping bacteria from growing & reproducing (bacteriostatic) by one of the following mechanisms:
• Inhibiting cell wall (peptidoglycan) synthesis, Inhibiting protein synthesis, Inhibiting nucleic acid synthesis, Injuring the plasma cell membrane (phospholipid bilayer) , Inhibiting synthesis of essential metabolites

Peptidoglycan Layer

• thick peptidoglycan layer in a gram positive layer The cross-linked peptidoglycan layer: Maintains bacterial cell shape and integrity ,Prevents cell lysis from high osmotic pressure
• or its synthesis inhibited, cell lysis occurs or cell unable to replicate

Synthesis of Peptidoglycan Cell Wall Chains

• Chains are synthesized in 3 main steps

1. Precursor Formation Step (takes place in cytoplasm)

• Formation of NAG0NAM precursor 2 .Trans glycosylation Step (takes place in periplasm by crossing the inner cytoplasmic cell membrane by a 55 carbon lipid carrier molecule

3. Transpeptidation Step (takes place In periasm, linking NAG0NAM to eachother

Peptidoglycan (PD) Layer Synthesis

Before PG cross-linking, PG chains feature NAM moieties connected to 5-amino-acid peptides ordered . During PG cross-linking, transpeptidase removes the A and links to neighboring L, thus forming a connected a latticework After PG cross-linking, the resultant scaffold provides structural to bacterial cell integrity β-lactams bind to the active site to block its activity loosing cell wall .

Antibiotics

• inhibits enolpyruvate transferase (MurA) 2 = inhibits L-alanine racemase and D-alanylalanine synthetase and inhibits dephosphorylation of C55-bactopreno

Inhibiting Cell Wall synthesis

B-Lactam Antibiotics: Transpeptidase , cell wall synthesis, leading to loss and cell death Non-B-Lactam Antibiotics: Terminal D-Ala , cell wall synthesis, leading to cell death

• Lactam Antibiotics primary action by suicide inhibition with Glycopeptide transpeptidase Structural of B-lactam ring resembles the Ala-Ala dipeptide sequence of the native bacterial glycopeptide

Antibiotics Selection

Dilution Test: Commonly test to determine the lowest concentration of antibiotic that inhibits visible bacterial growth known and 3 log 10 (MIC) for the minimum inhibitory concentration Bacteriocidal= log 10 CFU/mL reduction in growth. Bacteriostatic=reduction (MIC) – defined as <

Antibacterial Targets

• Outer Cell Membrane = Polymyxin B, Colistin
• Cytoplasmic membrane = Daptomycin,

Antibacterial Targets For Antibiotic categories

• nucleic acids
• RNA- Polyermase: Rifampin folate synthesis; Sulafonamides damage-Metronidazole
• Inhibit cell wall .B Lactams
• Inhibiting the formation of peptide bonds that connect the bacteria

- B-Lactam Antibiotics:

Monobactams cephalosporins carbapenems

• There is also non-B-Lactam antibotics like glycopeptide like vancomycin

• cell membrane =Polymyxin B and Colistin protein synthesis

Resistance

• Bacteria evolve resistance to antibiotics. . B Lactams binds and allows the peptide bond to be formed, because they are competive inhibition can overcome by increases in concentration Overuse of antibiotics allows for bacteria to evolve resistance quickly so antibiotics are generally reserved for serious bacterial issues

Antibiotics and protein targets

• Bacteria protein are targeted, macrolides bind reversibly to rRNA on the

B-Lactam Antibiotics:

Monobactams, cephalosporins,carbapenems function and also bind in other location with the 3s , this action occurs in cell death

Membrane-active agents

membranes, by forming complexes (pores) in the cell membrane causing rapid loss Daptomosin = of cellular K+ and membrane depolarization, this can effect DNA etc Polymyxins: used and binds to a Lipid portion

Antibacterial

Tetracyclines and Aminoglycosides have Antibiotics with sugar and amino groups. they reversibly bond protein . They interfer with the translocated riobsomes resulting in cell Bactericidal

RNA Polymerase

• Antibiotics used to to block transcription which lead to cell dealth
• The nitro group of metronidazole is able to serve as electron (in anarobic environments

Inhibitors of bacterial protein

• Tetracyiclines* and Aminoglycosides- Antibotics with sugar with

B-

• Lactate Transpeptidase: The transpeptidase B can also cause inhibition that is resistant to bacterial activity.