Major Pathogens: Bacteria

Bacterial Pathogens

Pathogens = disease-causing bacteria

• Gram-positive cocci• Gram-negative cocci• Gram-positive rods• Gram-negative rods• Mycobacteria

• Walls too thick to stain for gram• Mycoplasma• Spirochetes• Obligate intracellular parasites

Gram-Positive CocciStaphylococcus

(grape-like clusters)Genus includes 33 species mostly harmlessLikes high osmotic pressure, low moisture

Staphylococcus aureusFacultative anaerobe, golden yellow pigmented colonies

Skin infections (abscesses), impetigoConjunctivitis

Food poisoningToxic shock syndrome

Staphylococcal scalded skin syndrome (SSSS)Nosocomial sepsis

Staphylococcus aureus

MOT and Pathology

Normal habitat: Skin, nose, vagina

33% are carriers

Exotoxins:

Enterotoxins: Food poisoning

Toxic shock syndrome toxin

Scalded skin syndrome toxin

Food poisoning1-6 hoursIntoxication: infection by digestion

ImpetigoSkin infection caused by Staphylococcus aureus

Scalded Skin SyndromeStaphylococcus aureus

Usually in babies

Diagnosis, Prevention, Treatment

Coagulase-positive; Catalase-positive

MSA plate

Hand-washing; proper food storage; frequent tampon changes

Penicillin (80% resistant)

Oxacillin; (methicillin)

Vancomycin

Rabbit plasma

Streptococcus = cocci that grow in chains

Streptococcus pyogenes (Group A - GAS)

Pharyngitis (Strep. throat)Scarlet feverRheumatic feverNecrotizing fasciitis (flesh-eating disease)Puerperal sepsis.

MOT and Pathology

Droplet infection: Pharyngitis/ Strep throat

Exotoxins:

Scarlet fever

Erythematous rash over body

Hemolytic enzymes: necrotizing fasciitis

Capsule

Composed of hyaluronic acid

Evades phagocytosis

Streptococcal Pharyngitis

Scarlet Fever Rash caused byStreptococcus pyogenes

Streptococcus epidemitis: normal flora (non pathogenic) on the body that is opportunistic, can cause UTI’s.

Necrotizing Fasciitis due to Streptococcus pyogenes

http://emedical-help.com/necrotizing-fasciitis-flesh-eating-disease/

Puerperal Sepsis: “Child Fever”

Diagnosis, Prevention, Treatment

Culture swabs from lesions

Beta-hemolytic on Blood Agar plates

Antibody titer

Proper hygiene during wound care

Prolonged treatment with penicillin (Rheumatic fever patients)

Penicillin

Debridement of infected tissues

Streptococcus agalactiae/dysgalactiae (Group B)Neonatal meningitis and sepsis

Streptococcus mutansDental caries

Streptococcus viridansBacterial endocarditis

Streptococcus pneumoniaePneumoniaAdult bacterial meningitis

Streptococcus agalactiae/dysgalactiae (Group B)Neonatal meningitis and sepsis

MOT and Pathology

Normal vaginal flora: Can colonize genital tract and cause neonatal meningitis and sepsis

Prevention

Prophylactic Ampicillin (mother)

And Treatment

Penicillin (newborn)

Streptococcus mutans = facultative anaerobeDental caries (cavities)

• Metabolizes sugars to lactic acid decays enamel• Excretes a sticky polysaccharide for adhesion to

surfaces and each other plaque

• Biofilm protects from extreme and changing environment of the mouth

• Biofilm plaque best removed mechanically (floss)• Oral Hygiene is important• Treatment: Fill cavities

Streptococcus viridansBacterial endocarditis

PreventionProphylactic

amoxicillin

Streptococcus pneumoniaePneumonia, meningitis

MOTDroplet

DiagnosisDirect sputum culture

PreventionVaccination

TreatmentPenicillin or erythromycin

Gram-Negative Cocci

Neisseria: aerobic, found in mucous membranes, release endotoxins

• Neisseria gonorrheaOphthalmic gonorrhea

Genital gonorrhea

• Neisseria meningitidis:Adult bacterial meningitis (Meningococcal

meningitis)

Pus Discharge in Gonorrhea

N. gonorrheaMOT & PathologySTD/STIPID (pelvic infl.

Disease)

DiagnosisCulture (Gram-

negative intracellular diplococci

PreventionSafe sex

TreatmentCeftriaxone

Neisseria meningitidisMOT & Pathology

Droplet: meningitisStiff neck, fever, headache,

vomiting

DiagnosisCSF Culture

PreventionVaccine

Treatment: Penicillin, Rifampicin

Gram-Positive Bacilli

• Spore-forming Gram-positive Bacilli

Bacillus anthracis: AnthraxBacillus cereus: Food poisoningClostridium botulinum: BotulismClostridium tetani: Tetanus (lockjaw)Clostridium perfringens: Gas gangreneClostridium difficile: Pseudomembranousenterocolitis

B. anthracisMOT & PathologySpores (facultative anaerobe)

DiagnosisCulture

PreventionPPEProphylaxisVaccine (only for risk groups)

TreatmentCiprofloxacin

Bacillus cereus: soil dwelling aerobe

MOT and PathologySpores ingested: food

poisoningEnterotoxin

PreventionProper food handling

Treatmentself-limiting

Clostridium botulinum: anaerobe

MOT and PathologyFood contaminated with spores

Vegetables, HoneyNeurotoxin: very toxic

Acetylcholine blocked: paralysis of face/limbs

PreventionProper sterilization of food

before canning

Treatment: Antitoxin

Clostridium tetani

C. tetani: anaerobe

MOT and PathologySpores enter woundExotoxins

Muscle spasms, lockjaw

DiagnosisDirect observation

PreventionVaccine: DTaP/ Tdap

Treatment: Tetanus immune globulin; antibiotics

Clostridium perfringens: anerobe

C. perfringensMOT & Pathology

Spores enter wound after traumaToxins and gasTissue necrosis

DiagnosticsFoul smellCrepitation

PreventionClean wound thoroughly

Treatment: Penicillin & Wound debridement

Clostridium difficilePseudomembranous enterocolitis

MOT & PathologyFecal-Oral – usually nosocomialBroad-spectrum antibiotics allow C. difficile to

flourishExotoxins: severe diarrhea

TreatmentStop the antibioticRe-hydration therapy

PreventionAseptic technique

Non-spore-forming Gram-positive Bacilli

Corynebacterium diphtheriaeDiphtheria

Listeria monocytogenesGastroenteritis

Corynebacterium diphtheriae• MOT & Pathology

• Sore Throat, fever, trouble breathing

• Droplet infection

• Toxin: heart/ kidney damage

• Diagnosis

• Throat exam• pseudomembrane

• Prevention

• DTaP contains toxoid

• Treatment: Antitoxin, Penicillin

Listeria monocytogenes• MOT & Pathology

• Ingestion of contaminated food

• Psychrophilic

• Spontaneous abortion

• Prevention

• Proper food handling

• Pasteurization

• Treatment

• Ampicillin

Gram-Negative BacilliEnteric Gram-negative Bacilli: facultative anaerobesEscherichia coli: UTI, gastroenteritis(Traveler’s diarrhea), hemolytic-uremicsyndrome.

Salmonella enteritidis: Gastroenteritis

Salmonella typhi: Typhoid fever

Shigella dysenteriae: Gastroenteritis

Campylobacter jejuni: Gastroenteritis

Helicobacter pylori: Gastric ulcer,carcinoma of the stomach

Vibrio cholerae: Cholera

Vibrio parahemolyticus: Food toxicity

Enterobacteriaceae

• Large family of gram-negative rods

• Found primarily in colon

• Common features

• Facultative anaerobe, non-spore forming

Escherichia coli• MOT & Pathology

• Normal Flora of human colon

• UTI (most common cause)

• Fecal-oral

• O157:H7 toxin: hemolytic-uremic syndrome

• Treatment

• Quinolones

• Self limiting

• Prevention

• Remove urinary catheters, ♀ wipe front to back, water and food handling, handwashing

Salmonella enteritidis• MOT & Pathology

• Fecal-oral (human and animal)

• Eggs and poultry

• Reptiles

• Treatment

• Self-limiting

• Rehydration therapy

• Prevention

• Public health

• Personal hygiene

Salmonella typhi

• MOT & Pathology

• Fecal-oral (human only)

• Typhoid fever

• Treatment

• Ciprofloxacin

• Prevention

• Personal hygiene

• Vaccine available (for travelers only)

Shigella dysenteriae

• MOT & Pathology

• Fecal-oral (human only)

• ID50 =10

• The four Fs: fingers, flies, food, and feces

• Treatment

• Rehydration/Ciprofloxacin

• Prevention

• Public health

• Personal hygiene

Campylobacter jejuni

• MOT & Pathology

• Fecal-oral (human and animal)

• Food or water contamination

• Treatment

• Ciprofloxacin

• Prevention

• Public health

• Personal hygiene

pH – Neutrophiles & Acidophiles

As with temperature, bacteria have minimum, optimum and maximum pH ranges.

Neutrophiles

• Protozoans and most bacteria have an optimum pH range of 6.5 to 7.5.

• pH range of human organs and tissues.

Acidophiles• Most fungi & some bacteria grow best in acid niches.

• Example: Chemoautotrophic bacteria that live in mines and in water that runs off from waste rock around mines.

• Obligate acidophiles have to live in an acidic environment.

• Acid-tolerant Microbes will survive in an acid environment, but do not prefer that.

Images: HelicobacterPylori : Electron micrograph of H. pylori possessing multiple flagella. Yutaka Tsutsumi, M.D. Professor Department of Pathology Fujita Health University School of Medicine

Helicobacter pylori

• Gram-negative, microaerophilic, and acidophilic bacterium.

• Infects various areas of the stomach and duodenum.

• Many cases of peptic ulcers, gastritis, duodenitis, and perhaps some cancers are caused by H. pylori infections.

• However, many who are infected do not show any symptoms.

• Helicobacter spp. only known microorganisms to thrive in highly acidic environment of stomach.

Helicobacter pylori• MOT and Pathology

– Ingestion, produce ammonia

– Gastric ulcer

– Carcinoma

• Treatment

– Antibiotics

• Prevention

– None

pH : Cholera (Alkalinophiles)

Alkilinophiles• Can live in water as well as soil with pH’s around

11.5 (14 is max alkilinity)!

• Example: Vibrio cholera (Cholera) will grow outside the body at a pH of 9.0.

• Infectious gastroenteritis caused by the bacterium Vibrio cholerae.

• Transmission occurs through ingesting contaminated water or food.

• Major reservoir for cholera long assumed to be humans, but considerable evidence exists that aquatic environments can serve as reservoirs of the bacteria.

• Gram-negative bacterium that produces cholera Alkilinophiles

• Action on mucosal epithelium lining of the small intestine responsible for the characteristic massive diarrhea.

• One of the most rapidly fatal illnesses known. Progresses from first liquid stool to shock in 4 to 12 hours, with death quickly following without rehydration treatment.

Vibrio cholerae• MOT and Pathology

– Fecal-oral

– Contaminated H2O

– Enterotoxin– Watery stools

• Treatment

– Rehydration therapy

• Prevention

– Public health

– Personal hygiene

Vibrio parahemolyticus

• MOT and Pathology

– Lives in warm seawater

– Ingestion of raw/undercooked seafood

• Treatment

– Self limiting (three days)

• Prevention

– Proper refrigeration and cooking of seafood

Nosocomial Gram-negative Bacilli

Klebsiella pneumoniae: Pneumonia and UTI

Proteus vulgaris: UTI especially hospital acquired

Pseudomonas aeruginosa: Burn sepsis and UTI and more

Serratia marcescens: Burn sepsis

Klebsiella pneumoniae

• MOT & Pathology

– Respiratory tract and intestinal tract

– Droplet

– Catheter

• Treatment

– Antibiotics

• Prevention

– Prompt removal of urinary catheter

Proteus vulgaris

• MOT & Pathology

– Human colon

– Soil and H2O

– Highly motile, colonizes urethra, leads to ascending infection

• Treatment/Prevention

– Antibiotics

– Prompt removal of catheters

Nail Infection with Pseudomonas aeruginosa

Psuedomonas aeruginosa• MOT & Pathology

– Soil, H2O, NF colon/skin

– Aqueous solutions

– Withstand disinfectants

– Burn wounds

– Purulent blue-green discharge/fruity odor

• Treatment/Prevention

– Antibiotics

– Highly resistant

– Sterilization

Burn Infection with Pseudomonas aeruginosa

Respiratory Gram-negative Bacilli

Bordetella pertussis: Whooping cough

Haemophilus influenza: Pediatric meningitis,

Otitis media, sinusitis, and epiglottitis

Legionella pneumophilia: Pneumonia

Bordetella pertussis

• MOT & Pathology

– Whooping cough

– Droplet infection

– Complications: pneumonia or CNS

• Treatment

– Erythromycin

• Prevention

– DTaP

Haemophilus influenza

• MOT & Pathology

– Droplet infection

– Type B encapsulated (Hib)

– Meningitis, otitis media, sinusitis, epiglottitis

• Treatment/Prevention

– Ceftriaxone

– Hib vaccine (Hemophilus influenza type B)

Legionella pneumophilia

• MOT & Pathology

– Inhalation of aerosols from infected H2O

– Grows best in warm waters

– Air conditioners, water-cooling towers

– Legionnaire’s disease: Pneumonia

• Treatment/Prevention

– Erythromycin

– Reduce aerosols

– Water treatment

Arthropod-borne disease:

Yersinia pestis: Plague

Borelia burgdorferi: Lyme disease (Spirochete)

Rickettsia rickettsii: Rocky mountain spotted fever(Obligate intracellular parasite)

Yersinia pestis

• Plague (black death)

• Killed one quarter of the population of Europe in the middle ages

• Fleas transmit

• Bubos: inflammed

lymphnodes

• Droplet = pneumonic plague

Lyme disease

Causative agent:

Borrelia burgdorferi

• Reservoir: Deer

• Vector: Ticks

• First symptom:

Bull's-eye rash

• Second phase:

Irregular heartbeat,

encephalitis

• Third phase: Arthritis

Obligate Intracellular Parasites

• Chlamydia trachomatis: NGU, pelvic

inflammatory disease (PID), eye infection

• Rickettsia rickettsii: Rocky mountain spotted

fever (RMSF)

• Rickettsia prowazeki: Typhus

• Lack ability to produce enough ATP to grow independently

Chlamydia trachomatis• Most common bacterial STI in USA

• Eye infection, fomites, birth canal

• PID

• Infertility

• Erythromycin

Rickettsia rickettsii: Rocky mountain Spotted Fever

• Dogs and rodents are reservoir

• Tick-borne transmission

• Tetracycline

• Insect repellent/tick inspection

Rickettsia prowazeki• Typhus

– Fever, chills, rash, meningitis, death

• Louse-borne

• Disease of poverty and wartime

• Control of body lice

Syphilis: Spirochaete Infection

Treponema pallidum

• STI

• Chancres

• Neurosyphilis: 10%; dementia

• Penicillin to treat; safe sex to prevent

Mycobacteria

• Aerobic acid-fast bacilli

• Mycobacterium tuberculosis:

• Pulmonary TB

– Droplet

– 90% asymptomatic: Skin Test

– Hemoptysis

• Mycobacterium avium: indistinguishable from TB

– Widespread in environment

Mycobacterium leprae

• Leprosy

• Direct contact

• Nasal or skin secretions

• Replicates in skin

• Anesthesia, bone re-absorption

• Loss of digits or tip of nose

• Antibiotics

• Isolation of patients

Mycoplasma

• Smallest bacteria

• Lack cell wall

• Fluorescent stains to visualize

• Mycoplasma pneumoniae: walking pneumonia

– Droplet infection

– Common on campuses

– May be self-limiting or require antibiotics

Question

Staphylococcus and Streptococcus can be easily differentiated in a lab by which of the following?

a)Cell shape

b)Gram stain reaction

c)Growth in high salt concentration

d)Ability to cause disease

e)Glucose fermentation