Clinically Encountered Bacteria

Suthan Srisangkaew, MD.

Review: Classification

• Gram-positive • Gram-negative

• Cocci- Chain- Cluster

• Bacilli- Spore forming- Non-spore forming

- Branching- Non-branching

• Aerobic• Anaerobic

– Bacilli predominate

Aerobic Gram-positive Cocci• In chain

Streptococcus (Lancefield group)Enterococcus

• In clusterStaphylococcus (Coagulase)(Micrococcus, Leuconostoc)

Aerobic Gram-positive Bacilli

• Spore formingBacillus

• Non-spore forming- Non-branching

CorynebacteriumListeriaLactobacillus

- BranchingNocardia

Aerobic Gram-negative Cocci

Always in pair! Coffee bean shape

Neisseria

Moraxella

Aerobic Gram-negative bacilli

LARGE GROUP….

• Enterobacteriaceae– E. coli, Klebsiella,

Enterobacter– Salmonella, Shigella– Yersinia– Proteus, Providencia,

Serratia, Morganella

• Vibrionaceae– Vibrio, Aeromonas,

Plesiomonas

• Non-fermentativePseudomonas AcinetobacterBurkholdderia

• Curve, MicroaerophilicCampylobacter jejuniHelicobacter pyroli

• Fastidious, Coccobacilli

Haemophilus

Bordetella

• Fastidious, Zoonosis

Brucella

Pasteurella

Anaerobic Gram-positive Bacilli

Spore forming– Clostridium

Non-spore forming

Branching– Actinomyces

Non-branching– Proprionibacterium– Bifidobacterium

Anaerobic Gram-negative bacilli

• Bacteroides• Fusobacterium• Prevotella

Special groups

• Mycobacterium

• Rickettsia

• Chlamydia

• Mycoplasma

• Spirochetes

Treponema

Leptospira

Systemic Orientation

• Skin, Wound, Soft tissue• Bone, Joint• Eye, Ear, Sinus• Respiratory tract• Gastrointestinal tract• Urinary tract, Sexual transmitted infection• Central nervous system• Blood stream, Endocarditis

Skin infection

• Primary infection– S. aureus, group A strep., P. acne

• Blood-borne – Syphilis, rickettsia, virus– Bacterial toxin: gr. A strep, S. aureus

• Scarlet fever: gr. A strep• Staphylococcal scalded skin syndrome: S. aureus

Scarlet fever

Staphylococcal scalded skin syndrome

Skin infection• Folliculitis: S. aureus

– Hair follicle

• Acne: P. acne– Sebaceous gland

• Impetigo: gr. A strep.– Superficial dermis

• Erysipelas: gr. A strep.– Deep dermis

• Cellulitis: S. aureus, gr. A strep., GNB, Clostridium– Subcutaneous connective tissue

Folliculitis

Impetigo

Erysipelas

Cellulitis

Wound Infection

• S. aureus: most common• GNB: immunocompromized

host

• Human bites: anaerobic bacteria : Bacteroides

• Dog, cat bites: Pasteurella multocida

• Burn wound, necrosis: P. aeruginosa

• Tetanus: Clostridium tetani• Gas gangrene: Clostridium

pefringen

Gas Gangrene

Bone & Joint Infection

• Osteomyelitis: S. aureus– Both blood-borne and direct trauma

Gr. A strep, GNB, anaerobes

• Septic arthritis: – S. aureus– Neisseria gonorrhea (young adult)

Eye, Ear, Sinus Infection

• Conjuctivitis: S. aureus, Chlamydia trachomatis, N. gonorrhea

• EarOtitis externa: P. aeruginosaOtitis media: S. pneumoniae, H. influenzae

• SinusAcute sinusitis: S. pneumoniae, H. influenzae, Moraxella catarrhalisChronic sinusitis: + anaerobes

Upper Respiratory Tract Infection

• Rhinitis: mostly virus• Pharyngitis & Tonsillitis:

– Exudate & hemorrhage: Bacteria

• Gr. A strep.

(S. pyogenes)– Vesicle & ulcerative lesion:

Virus– Psuedomembranous

pharyngitis (Diphtheria) • Corynebacterium

diphtheria

Middle Respiratory Tract Infection

• Epiglottitis– 90% bacteria: H. influenzae, S. pneumoniae

• Laryngitis (Croup)– 90% virus

• Bronchitis– 80% virus– 20% bacteria: H. influenzae, M. pneumoniae,

C. pneumoniae, Bordetella pertussis

Lower Respiratory Tract Infection• Acute pneumonia: days to hours

– Children: 80% Virus– Adults: 80% Bacteria

• S. pneumoniae, S. aureus, H. influenzae

M. pneumoniae, C. pneumoniae• Enterobacteriaceae, P. aeruginosa

• Chronic pneumonia: weeks to months• M. tuberculosis, Nocardia• Fungus

• Lung abscess & Empyema• S. aureus• Anaerobes

Enteric Infection• Watery diarrhea: proximal

small intestine– Vibrio cholerae– Vibrio parahaemolyticus– Enterotoxigenic E. coli (ETEC)– Food poisoning

• S. aureus, B. cereus

– Many viruses

• Dysentery: colon– Salmonella, Shigella– Campylobacter jejuni– Enteroinvasive E. coli (EIEC)– Plesiomonas spp.– Yersinia enterocolitica– C. difficile (ATB associated)– Entamoeba histolytica

Food PoisoningNo infection, Vomiting

prodominate• S. aureus 5-25%• Bacillus cereus 1-2%

(Fried rice)• Clostridium botulinum

– Neuromuscular paralysis

• Chemical 20-25%

Recurrent Peptic Ulcer: Helicobacter pyroli

Foods and Germs• Dairy

– Campylobacter, Salmonella, Listeria, and Staphylococcus species

• Eggs– Salmonella species

• Meats– C perfringens and Salmonella,

Aeromonas, Campylobacter, and Staphylococcus species

• Ground beef – Enterohemorrhagic E coli

• Poultry– Campylobacter species

• Pork– C perfringens and Y

enterocolitica

• Seafood– Aeromonas, Plesiomonas, and

 Vibrio species and astrovirus• Oysters

– Plesiomonas and Vibrio species and calicivirus

• Vegetables– Aeromonas species and C

perfringens• Alfalfa sprouts

– Enterohemorrhagic E coli and Salmonella species

• Fried rice– Bacillus species

• Custards, mayonnaise– Staphylococcus species

Urinary Tract Infection• Cystitis: lower UTI• Pyelonephritis: upper

UTI, systemic symptoms

• 90-95% E. coli• Other enterobacteriaceae

K. pneumoniae, Enterobacter

• Staphylococcus saprophyticus (coag. Neg.)

• Candida

Sexual Transmitted Infection

• Neisseria gonorrhea– Urethritis,

Cervicitis(phyryngitis, conjunctivitis)

• Chlamydia trachomatis– Non-gonococcal

urethritis– Lymphogranuloma

venerum• Treponema pallidum

– Syphilis (Chancre)• Haemophilus ducreyi

– Chancroid

Infection of fetus and newborn

• Transplacental: – Listeria monocytogenes– Treponema pallidum

• Perinatal:– Gr. B streptococci– E. coli– C. trachomatis– N. gonorrhea

Central Nervous System Infection

• Acute Meningitis– Newborn: Gr. B Strep., E. coli, Listeria

monocytogenes, – Children: S. pneumo., H. influenzae, N.

meningitidis, Salmonella– Adults: N. meningitidis, S. suis, S. pneumo.,

S. agalactiae

• Chronic Meningitis– Mycobacteria – Fungi

Bacteremia & Septicemia

• Bacteremia: occur normally

• Septicemia: bacteremia + clinical symptoms

• Most common from:– Urinary tract infection– Respiratory tract infection– Infection of skin and soft tissue

Endocarditis

• Native valve– Viridans streptococci 30-50%– S. aureus 15-40%– Other strep 15-25%– Enterococci 5-18%– Coag. Neg. Staph. 4-30%– Gram-negative bacilli 2-13%

• Intravenous drug abuse– S. aureus

• Prosthetic valve– Coag. Neg. Staph.

Systemic Zoonosis

• Leptospirosis: Leptospira interrogans– Rats, Rodents

• Brucellosis: Brucella abortus– Goats, Sheeps

• Plaque: Yersinia pestis– Rats > Flea

• Anthrax: Bacillus antrasis– Cow, Horse > Spore

Thailand Endemic

• Leptospirosis– Dirty water contact

• Mellioidosis: Burkholderia pseudomallei– NE Thailand, soil contact

• Scrub typhus: Orientia tsutsugamushi– Chigger > bush contact, “Eschar”

• Murine typhus: Rickettsia typhi– Mouse > flea bites

Hospital Acquired Infection

• Pseudomonas aeruginosa

• Acinetobacter baumanii, A. lwoffii

• Sternotrophomonas maltophilia