bacterial infections...penicillins oldest class of antibiotics inhibits formation of bacterial cell...

BACTERIAL INFECTIONS

INTRODUCTIONDefining bacteria and bacterial infections

▹ prokaryotes that are everywhere

▹ microscopic, very small

▹ single-cell organisms with no true

nucleus, no membrane-bound

organelles

▹ commonly known as dangerous as

some cause disease...

WHAT IS BACTERIA?

WHAT IS BACTERIA?

▹ but is very important, especially with regards to global

ecology▸ Chemical changes include organic decay and nitrogen fixation

▸ biochemical and biotechnological advancements acquired with

the use of bacteria

▸ Helpful bacteria reside in the gastrointestinal tract and aid in

digestion & immunity

▹ only a few bacteria are actually bad (disease causing)

BACTERIA VS VIRUSES

▹ both bacteria and viruses are types of pathogens

▹ Size of bacteria > size of virus▹ Bacteria are capable of self-

reproduction, whereas viruses rely on host’s DNA

▹ May have similar symptoms

WHAT ARE BACTERIAL INFECTIONS?

▹ proliferation of harmful bacteria in the body

▹ can infect any part of the body, wide variety of diseases

▹ 3 different shapes of bacteria:▸ Helical (spirilla)▸ Spherical (cocci)▸ Rod-shaped (bacilli)

WHAT ARE BACTERIAL INFECTIONS?

▹ 2 kinds of classifications:▸ Gram-positive: thick cell wall▸ Gram-negative: thin cell wall

▹ usually treated within the immune system or with antibiotics

COMMON CASES OF BACTERIAL INFECTIONS

▹ Bacterial Skin Infections▸ Mostly caused by gram-positive

strains of bacteria such as streptococcus and staphylococcus

▸ Treated with different forms of antibiotics (oral/topical) varying on infection

▸ Common symptoms include: skin rashes, red areas, blisters, sores, bumps


▹ Foodborne Bacterial Infections▸ Bacteria present in food caused by

improper/unsanitary handling –> food poisoning

▸ Risk products: fish, poultry, eggs, meat, dairy

▸ Common symptoms include: vomiting, nausea, fever, diarrhea, abdominal pain


▹ Sexually Transmitted Bacterial Infections▸ STDs associated with harmful bacteria▸ Damage the reproductive system,

sexual organs, and some other parts of the body

▸ Potentially fatal if untreated

DEALING WITH BACTERIAL INFECTIONS

DIAGNOSISHow doctors figure out the cause of your sickness

DIAGNOSIS

▹ Symptoms and Medical History▹ Microbial Cultures

▸ Letting bacteria reproduce under controlled conditions

▸ size, shape, colony size, and color as factors to determine the specific bacterial species

▹ Urine Tests▹ Blood Tests

HOW GRAM STAINING WORKS

DIAGNOSIS

▹ Polymerase Chain Reaction (PCR)▸ fast and efficient way to make

multiple copies of a specific DNA region

▸ Method to search for specific genes to identify bacterial species

TREATMENTHow to fight that pesky bacterial infection

ANTIBIOTICSAnti (against) + Bio (life)

Drugs used against bacteria

HOW DO ANTIBIOTICS WORK?

▹ Generally, antibiotics work by affecting things that bacterial cells have but human cells do not have

▹ Ex: the beta-lactam side chain of penicillin (an antibiotic) hinders the bacteria from building a cell wall

HOW ARE ANTIBIOTICS PRODUCED?

Classifications of antibiotics

PENICILLINS

▹ Oldest class of antibiotics▹ Inhibits formation of bacterial cell wall▹ Used to treat skin infections, dental infections, respiratory

tract infections, UTIs, and gonorrhea▹ They are generally very safe drugs (not very toxic)▹ Some side effects include nausea, vomiting, and diarrhea.

CEPHALOSPORINS

▹ Similar drug action with penicillin▹ Used to treat pneumonia, strep throat, staph infections,

tonsillitis, bronchitis, skin infections, UTIs, and gonorrhea▹ very safe▹ Some side effects include diarrhea, nausea, and mild

stomach cramps

FLUOROQUINOLONES

▹ Inhibits the bacterial enzyme DNA gyrase▸ DNA gyrase relieves the stress produced by the helicase when

unwinding the DNA, making it necessary for cell replication

▹ Synthetic products▹ Used to treat UTIs, skin infections, respiratory infections,

and pulmonary infections in cystic fibrosis▹ Generally has an accepted level of safety, causing a few

side effects that affect the central nervous system▹ Unadvisable for children and pregnant women

TETRACYCLINES

▹ Old class of antibiotics, obtained from Streptomyces ▹ Inhibits the bacterial protein synthesis through the

interaction with 30S subunit of bacterial ribosome▹ Used to treat spirochetes, atypical bacteria, rickettsia, and

amebic parasites▹ Should not be used in children younger than 8 years old,

or during periods of tooth development▹ Side effects include stomach cramps, diarrhea, nausea,

vomiting, esophageal ulceration, and sore mouth.

MACROLIDES

▹ Obtained from Streptomyces▹ Targets bacterial ribosomes to prevent protein production▹ Used to treat respiratory tract infections such as

pharyngitis, sinusitis, and bronchitis, as well as genital, gastrointestinal tract, and skin infections.

▹ Considered fairly safe, but some side effects may arise such as nausea, vomiting, and diarrhea.

AMINOGLYCOSIDES

▹ Obtained from Streptomyces▹ Binds to the 30S subunit of the bacterial ribosome.▹ Used to treat infections caused by gram-negative bacteria▹ Must be injected since it can easily be broken down in the

stomach▹ Major concerns

▸ Ototoxicity- could damage hearing▸ Nephrotoxicity- can result to kidney damage▸ The damages that may arise are irreversible

Antibiotic Resistance

PHAGE THERAPYAn alternative to antibiotics

WHAT IS PHAGE THERAPY?

▹ Using bacteriophages to treat bacterial infections

▹ Lytic phages disrupt bacterial metabolism and cause the bacterium to lyse▸ Lysis - disintegration of a cell by

rupture of the cell wall or membrane

▹ Highly specific and faces regulatory issues like patenting

EXAMPLES OF BACTERIAL INFECTIONS

TETANUS

▹ Caused by Clostridium tetani▹ Enters body via open wound▹ Releases powerful toxins (tetanospasmin)▹ Incubation period: 2 days to several weeks▹ Fever, pain, neck and jaw spasms▹ Treatments include sedation, muscle relaxing chemicals,

antibiotics, antitoxins▹ Prevention: vaccine immunity for 5 years

TYPHOID FEVER

▹ Caused by Salmonella enterica▹ Spreads through contaminated food and water▹ 20 million victims from 1914 - present▹ Incubation: 7 to 14 days▹ Symptoms include fever, headaches, constipation,

diarrhea▹ Treatment: antibiotics▹ Prevention: processed food, hygiene, vaccine

CHOLERA

▹ Caused by Vibrio cholerae▹ Spreads through water infested with human feces▹ Incubation: 1-7 days▹ Symptoms include chronic diarrhea, dehydration, loss of

liquids and salts▹ Treatment: replace loss salt and water▹ Prevention: vaccine, hygiene

PLAGUE

▹ Caused by Yersinia pestis▹ Known for causing The Black Death▹ Incubation: 2 to 10 days▹ Symptoms include fever, swelling of lymphatic ganglions

and skin▹ Treatment: antibiotics▹ Prevention: vaccine

TUBERCULOSIS

▹ Caused by Mycobacterium tuberculosis▹ Spreads through air and milk from infected cows▹ Was present even in Ancient Egypt and Peru mummies▹ 8 million new cases per year▹ 2 million die annually▹ 150 million died since 1914▹ Symptoms include coughing, fever, shivering, bloody

expectoration, weight loss, sweating, tiredness, glossy eyes

TUBERCULOSIS

▹ More aggressive in women and persons between 15 and 45 years old

▹ Mutant strains resistant to almost all drugs, kill 50% patients

▹ Treatment: isoniazid, ethambutol, Rifapentin▹ Long and costly treatment, 6 months, resting, clean air,

proper diet, medication▹ Prevention: Bacillus Calmette-Guerin vaccine, milk

pasteurization▹ Vaccine effective in children, useless in adults

DIPHTHERIA

▹ Caused by Corynebacterium diphtheriae▹ Can spread from person to person via sneezing, coughing▹ Commonly found in the nose, throat, airway area, tongue▹ Symptoms include fever, chills, swollen glands in the neck,

sore throat, bad cough, drooling, difficulty in breathing or swallowing

▹ Treatment: antitoxin injection, erythromycin▹ Prevention: pediatric pipit hernia and tetanus vaccine

GONORRHEA

▹ Caused by Neisseria gonorrhoeae▹ Sexually transmitted disease▹ Having gonorrhea increases the risk of having pelvic

inflammatory disease for women▹ Symptoms include inflammatory discharge from sexual

organs, pain in pelvis or lower abdomen, painful urination (dysuria), bleeding between periods, painful or swollen testicles

GONORRHEA

▹ The Primary treatment is Rocephin, an antibiotic taken via injection

▹ Other antibiotics such as azithromycin and doxycycline are also used before Rocephin

SYPHILIS

▹ Caused by Treponema pallidum▹ Sexually transmitted disease▹ Challenging to diagnose, can be infected without

symptoms for years▹ Treated by penicillin injection. If it is allergic, antibiotics

such as doxycycline or azithromycin are used

SYPHILIS

▹ Primary stage: lymph nodes enlarge 2 weeks after exposure to bacteria

▹ Secondary stage: Skin rashes start to show after 6 weeks, enlargement of lymph nodes, headaches & fever

▹ Tertiary stage: cardiovascular and nervous system are frequently involved, life-threatening

RECENT PROGRESS AND ISSUES

Issues regarding Bacterial Infections

▹ Antibiotic Resistance▸ occurs naturally, but misuse of antibiotics in humans

and animals is accelerating the process.▸ A growing number of infections – such as pneumonia,

tuberculosis, and gonorrhoea – are becoming harder to treat as the antibiotics used to treat them become less effective.


▹ How it occurs:▸ Can occur naturally, but bacteria also change in

response to the use of antibiotic medicines. Bacteria can mutate to become antibiotic-resistant meaning when these resistant bacteria infect humans and animals, the antibiotics which could once be used to treat these infections are now less effective.


▹ Possible Causes:▸ Where antibiotics can be bought for human or

animal use without a prescription, the emergence and spread of resistance is made worse. In the same way, countries which do not have standard treatment guidelines, antibiotics are often over-prescribed by health workers and veterinarians and over-used by the public.


▹ Implications:▸ When first-line antibiotics becomes more

ineffective, more expensive medicines must be used. Higher healthcare costs can be a burden to the financially challenged. Aside from this, surgeries and other treatments become more dangerouswithout effective antibiotics for the treatment of infections.

Recent Progress/Research on Bacterial Infections

1. Discovery of genetic markers which can distinguish between viral and bacterial infections.

1. Medical scientists develop imaging agent that could be used to identify most bacterial infections.

1. HDT - Host-directed therapeutic strategies

Discovery of genetic markers which can distinguish between viral and bacterial infections.

▹ Scientists from the University's National Institutes of Health-funded Respiratory Pathogens Research Center identified 11 genetic markers in blood that accurately distinguished between viral and bacterial infections.

Discovery of genetic markers which can distinguish between viral and bacterial infections.

▹ Implication:▸ Physicians don't have a good way to confirm bacterial

infections like pneumonia and more often than not resort to prescribing an antibiotic. This discovery allows for more accurate issuance of antibiotics so as to avoid prescribing to those who don’t really need it. This reduces the chance of building up antibiotic resistance.

Medical scientists develop imaging agent that could be used to identify most bacterial infections.

▹ The traditional way of diagnosing bacterial infection involves biopsy of the infected tissue and/or blood and culture tests.

▹ A new positron emission tomography (PET) tracer, 6"-18^F-fluoromaltotriose, was developed by scientists that offers a non-invasive means of detection.

▹ was taken up in both gram-positive and gram-negative bacterial strains, and it was able to detect Pseudomonas aeruginosa in a clinically relevant mouse model of wound infection.

Medical scientists develop imaging agent that could be used to identify most bacterial infections.

▹ Implication:▸ Although this type of technology is relatively new and

experimental, the hope is that with it, it becomes easier to detect bacterial strains and determine whether prescription of antibiotic is necessary, or whether the antibiotic treatment is working thereby also reducing the chances of building up antibiotic resistance.

Host-directed therapeutic strategies (HDT)

▹ The strategy behind HDT is to interfere with host cell factors that are required by a pathogen for replication or persistence, to enhance protective immune responses against a pathogen, to reduce exacerbated inflammation and to balance immune reactivity at sites of pathology.


▹ In chronic bacterial infections, such as tuberculosis, HDT strategies aim to enhance the antimicrobial activities of phagocytes and to curtail inflammation through interference with soluble factors (such as eicosanoids and cytokines) or cellular factors (such as co-stimulatory molecules).


▹ Benefit:▸ HDT-based approaches are less prone to therapy

resistance than antibiotics that directly target pathogens, because resistance would require the pathogen to use an alternative host factor to replicate, to become less dependent on the targeted host factor or to evade activated host defence mechanisms.

bacterial infections...penicillins oldest class of antibiotics inhibits formation of bacterial cell...

Documents