Bacterial Pathogens Part II Flashcards
Anaerobic bacteria
Gram-negative
Rods/bacilli
Bacteroides species
Porphyromonas species
Prevotella species
Fusobacterium species
Anaerobic bacteria
Gram-negative
Cocci/spheres
Veillonella species
Anaerobic bacteria
Gram-positive
Rods/bacilli
Clostridium species
Actinomyces species
Propionibacterium species
Lactobacillus species
Anaerobic bacteria
Gram-positive
Cocci/spheres
Finegoldia species
Anaerococcus species
Peptostreptococcus species
Anaerobic bacteria
Definition
bacteria that grow in the absence of free oxygen but fail to multiply in the presence of oxygen
• Obligate or aerotolerant
• Do not use oxygen as a terminal electron acceptor with varying ability to tolerate the presence of oxygen
• Natural habitats: widespread in the environment but, in humans, found in the mouth, GI tract, GU tract, and on the skin
• Often have infections of “mixed anaerobes” due to the bacteria entering a breach of a mucosal or cutaneous barrier
Bacteroides species
infection
Gram-negative Rods/bacilli
• Make up ~20-30% of bacterial gut flora
• Members of the B. fragilis group are most clinically important
• Usually contribute to polymicrobial infections
- Escape from the gut:
- Abscess formation (abdomen, brain, liver, pelvis, lungs)
- Bacteremia
- Virulence factors:
- Capsule, extracellular enzymes, lipopolysaccharide, pili
- Enterotoxin (some B. fragilis group strains only)
Porphyromonas species
infection
Gram-negative Rods/bacilli
• Porphyromonas gingivalis is a well-known pathogen
• All species produce pigment
• Implicated in dental disease
• Periodontitis, necrotizing ulcerative gingivitis, infected root canals, periimplant lesions, and acute apical abscesses
• Also can form abscesses in multiple body areas
• Bacteremia
• Virulence factors:
• Capsule, extracellular enzymes, LPS, pili
Prevotella species
infection
Gram-negative Rods/bacilli
• Found predominantly in the oral cavity
• Fluoresce brick-red under UV light
• Involved in all types of dental infections
• Often isolated from human bite wound infections
• Abscesses
• Bacteremia
Fusobacterium species
infection
Gram-negative Rods/bacilli
Fusobacterium necrophorum is the most clinically
significant
• Pleomorphic, coccoid to long, curled forms
• Dental infections
• Tonsillitis
• Abscesses (periotonsillar, deep neck spaces, brain, lung, bone, joint, soft tissue, and others)
• Bacteremia
• Lemierre’s Syndrome:
Actinomyces species
infection
- Aerotolerant Gram-positive rods
- Over 40 species identified
- Found in oral, GI, and GU body sites
- Often grow as filamentous, branching rods
- “Molar-tooth” morphology
- Actinomycosis
- Slow, chronic infection
- Abscesses
- Crosses tissue boundaries
- Sinus tract formation
Propionibacterium species
Gram-positive Rods/bacilli • Propionibacterium acnes is the most significant (now has a new name: “Cutibacterium acnes”) • Aerotolerant, Grampositive rod • Found naturally on the skin • Good at forming biofilms • Prosthetic joint infections
Clostridium species
4 species
- Gram-positive rods, spore formers
- > 200 species
- Toxin-producing pathogens
C. tetani
C. botulinum
C. difficile
C. perfringens
C. tetani
C. botulinum
C. difficile
C. perfringens
C. tetani: Soil, penetrating injuries
- Tetanus toxin Tetanus
C. botulinum: Soil/dust, homecanned foods, raw
honey
- Botulinum toxin Botulism difficile
C. difficile; Antibiotic use, carriage in other patients
Toxin A (enterotoxin)
Toxin B (cytotoxin)
- Diarrhea +/- complications
C. perfringens: Foodborne, normal GI flora
- C. perfringens enterotoxin
- Alpha and theta toxins
- Diarrhea
- Gas gangrene
Clostridium tetani
symptoms
- Severe muscle spasms following a penetrating injury
- Trismus (lockjaw)
- Stiff neck
- Arched back
- Periods of apnea
- Rigid abdomen
Clostridium botulinum
symptoms
• Bilateral cranial nerve dysfunction • Blurred or double vision • Ptosis (eyelid drooping) • Dysphagia • Dysarthria • Facial weakness • Symmetric, descending weakness/paralysis
Clostridioides difficile
symptoms
- Antibiotic-associated diarrhea
- Watery diarrhea
- Severe colitis
- Pseudomembranous colitis
- Toxic megacolon
Clostridium perfringens
symptoms
Gas gangrene (clostridial myonecrosis)
• C. perfringens related gas gangrene often due
to trauma with deep penetrating injuries
Grow in deep tissue that grows toxin and need ICU support
Tissue devitalized
spiral/curve-shaped bacteria
Systemic disease
treponema pallidum
Borrelia burgdorferi
Leptospira species
spiral/curve-shaped bacteria
Gastrointestinal disease
helicobacter pylori
Campylobacter jejuni
Vibrio cholerae
Treponema pallidum
Spirochete (spiral-shaped) bacterium
• Causes syphilis
• Sexually-transmitted infection with a long, controversial history treatment withheld from male patients with syphilis in order to
study the natural history of the disease
Syphilis primary secondary latent tertiary congential stages
see slide 21
Primary: Chancre, lymphadenopathy ~3 weeks
Secondary: Rash, fever, malaise, lymphadenopathy,
mucosal lesions, condyloma lata, alopecia,
meningitis, headaches
2-12 weeks
Latent: Asymptomatic <1 year = early
>1 year = late
Tertiary: Cardiovascular, Neurosyphilis, Gummatous
Congenital: Mucocutaneous lesions, osteochondritis,
anemia, hepatosplenomegaly,
neurosyphilis
caused by Treponema pallidum
Borrelia burgdorferi
- Another spirochete
- Causative agent of Lyme disease
- Transmitted through tick bites
see slide 26 for Lyme disease
k
Leptospira species
- Another spirochete
- 22 Leptospira species described
- Rodents are the most important reservoir
- Gains entry into humans via cuts, mucous membranes, ingestion, or inhalation
- Wide range of severity (mild → death)
- Fever, chills, headache, myalgias (>80%)
- Nausea, vomiting, diarrhea (~30%)
- Conjunctival suffusion (~50%)
- Respiratory symptoms (~30%)
- Kidney failure (40-70%)
- Liver dysfunction (>50%)
- Meningitis (50-85%)
Helicobacter pylori
Gram-negative, curved bacterium
• Found almost exclusively in humans
• Its discovery and an atypical experiment showing its
relationship to gastritis led to Barry Marshall winning the Nobel Prize
• Peptic ulcer disease
• Gastritis
• Gastric adenocarcinoma
• Gastric mucosa associated lymphoid tissue
lymphoma
Bacteria with “different” cell walls
Mycoplasma, Ureaplasma, and Chlamydia species
Mycobacterium species
- M. pneumoniae
- M. hominis
- M. genitalium
- U. urealyticum and U. parvum
General characteristics
Mycoplasma, Ureaplasma, and Chlamydia species
• Mycobacterium species
- Small (~0.5 µm)
- Coccoid-shaped to tapered rods
- Fastidious
- No cell wall and therefore cannot be Gram stained
- Classic colony appearance: “fried egg” shape
Mycoplasma pneumoniae
• Nothing seen on Gram stain
• First called the Eaton agent
• Inhibited by antibiotics
• Main clinical syndromes
- Tracheobronchitis
- URTI – coryza, pharyngitis, otitis media
- Atypical pneumonia (up to 20% of CAP)
- Others
- Skin/MMs, heart, CNS, hematologic disease, kidneys, MSK
- Atypical pneumonia
- Bilateral patchy opacities
Mycoplasma genitalium
Discovered in 1981 from urethral swabs of men with non-gonococcal urethritis
• Extremely slow-growing and fastidious
• Sexually transmitted
• Females: cervicitis and pelvic inflammatory disease
• Males: urethritis
The other “genital mycoplasmas”
- M. hominis, U. parvum, U. urealyticum
- Believed for many years to be causative agents of genital tract disease
- Role now is less clear
- Often colonizing the female genital tract without causing symptoms (ie, normal flora)
- Some studies only implicate U. urealyticum as causing urethritis in males
Chlamydia species
• C. trachomatis, C. pneumoniae, and C. psittaci
• Lack a cell wall
• Intracellular pathogens
• Lifecycle includes the infective elementary bodies and reticulate bodi
Multiple serotypes with different
disease associations
A, B, C Trachoma: • Leading cause of blindness worldwide
D-K Urethritis, cervicitis, and others: STI, 40-95% ASYMPTOMATIC
Males: urethritis, urethral discharge, dysuria, testicular pain, conjunctivitis
• Females: cervicitis, vaginal discharge, dysuria, dyspareunia, conjunctivitis
• Newborns: conjunctivitis and pneumonia
L1, L2, L3 Lymphogranuloma venereum
• Primary: painless small papule/ulcer
• Secondary: painful enlarged lymph nodes (inguinal/anorectal)
• Tertiary: anogenital fibrosis, strictures, with elephantiasis and extensive ulceration
Chlamydia pneumoniae and C. psittaci
- Similar to M. pneumoniae, cause atypical pneumonia
- C. pneumonia: transmitted between humans via respiratory secretions
- Causes 0-44% of community-acquired pneumonia
- C. psittaci: causes ornithosis or psittacosis
- Found in the feces, urine, and respiratory secretions of birds
- Psittacine birds at highest risk
Mycobacteria
describe them
- A large group of organisms that do not Gram stain well due to a high content of complex lipids in their cell wall
- Require special staining methods (eg, Ziehl-Neelsen staining) and are referred to as “acid fast bacilli” (AFB)
- Long generation times (~20 hours vs 30 minutes for E. coli)
Mycobacterium tuberculosis
• Actually a complex of organisms (made up of 10 species)
• Causes a chronic, highly infectious pulmonary disease
• Referred to as the “white plague” or “consumption”
• Prior to the use of antibiotics, open air and sunshine were the cornerstones of therapy (in a sanatorium)
Pulmonary disease
• Inhalation of bacteria into the alveoli, establish infection, form granulomas
• Chronic fever, cough, dyspnea, anorexia, wasting
Extra-pulmonary disease
• Lymph nodes, bones, vertebra, joints, GI, GU, eyes, skin, pericarditis,
meningitis
• Tuberculosis remains one of the world’s deadliest communicable
diseases
Mycobacterium leprae
Extremely slow-growing AFB (generation time ~12.5 days)
• Causes leprosy: a chronic, granulomatous, debilitating disease
• Cannot be cultured in the laboratory
• Skin lesions: hypopigmented or erythematous
• Reduced sensation, weakness, peripheral nerve thickening
• Peripheral sensory nerve damage
Non-tuberculous mycobacteria
Mycobacterial species that do not cause tuberculosis
• Most are widespread in the environment
• Six main syndromes
Chronic pulmonary disease Lymphadenitis Soft tissue infection bone and joint infection Disseminated infection Catheter related infection
New emerging pathogen: M. chimaera
• A pathogen transmitted during
open heart surgery
• Found to contaminate heatercooler units for keeping
cardioplegia and patient blood at
optimal temperatures
• Aerosolized organism lands in the surgical field
Normal flora – skin/mucus membranes
Nose
nose: S. aureus S. epidermidis Diphtheroids Streptococci
skin/groin/perineum: S. epidermidis S. aureus Diphtheroids Streptococci Pseudomonas Anaerobes Candida
urethra and vagina: S. epidermidis Diphtheroids Streptococci Gram-negative rods
Normal flora – GI tract
Mouth:
Streptococci
Candida
Gingiva:
Prevotella
Porphyromonas
Teeth: S. mutans Prevotella Porphyromonas Fusobacterium Streptococci Actinomyces
Stomach/esophagous:
Lactobacilli
Normal flora – intestine
Duodenum:
Lactobacilli
Streptococci
Jejunum/ileum:
Enterobacteriaceae
Bacteroides
Large bowel; Bacteroides Fusobacterium E. faecalis E. coli Enterobacteriaceae Clostridium Pseudomonas
