BIOL 2421 Microbiology Lecture Notes: Bacterial Diseases
Dr. Weis Alpha, Beta Proteobacteria and other Phyla
Domain Bacteria
Proteobacteria
Largest taxonomic group of bacteria
Most of the gram negative, chemoheterotroph bacteria are in this phyla
Consists of Alpha, Beta, Gamma, Delta, Epsilon
Firmicutes [Low G + C Gram Positive Bacteria]
Clostridia (Clostrida)
Mycoplasma (Mycoplasmas)
Bacillales (Bacillus, Listeria, Staph)
Lactobacillales (Enterococcus, Strep, Lactobacillus)
Actinobacteriae [High G + C Gram Positive Bacteria]
Actinomycetales (Coryne, Actinomycetes, Mycobacteria, Nocardia)
Other Phyla:
Chlamydiae
Spirochaetes
Bacteriodetes
Fusobacteria
Beta Proteobacteria
Genus Neisseria
Gram negative kidney shaped cocci arranged as pairs, sometimes chains
Aerobic, but may prefer higher CO2 environment
Oxidase +, Catalase +
Nonmotile
Nonhemoytic, no enterotoxins, require blood or ascetic fluid for growth
Capsule
Normal flora for mammalian mucous membranes of the oro-naso pharynx
Four different groups (Group 1, 2, 3, and undefined)
Serotyping is used to identify the different strains based on the O- antigenic subunits of the LPS.
Human Neisseria Pathogens: Belong to group 1, translucent colonies
Virulence factors
O- subunits (endotoxin) à antigenic
Pili/Fimbria for attachment
Protease à splits human IgA
Accumulate free iron and have receptors for lactoferrin
Capsule
Beta lactamase
Neisseria gonorrheoeae
5-7 day incubation
Susceptible to most antibiotics and disinfectants
STD infections à pus à scarring à sterility if reproductive
Causative agent of Gonorrhea of the urethra, cervix
Other sites for sexual contact can infect the rectum & pharynx
Urethritis, Cercicitis, proctitis, salpingitis, epididymitis
Bacteremia can cause: arthritis, meningitis, endocarditis
PID [30% of cases]
Neonatal conjunctivitisà blindness if not treated
DX: ELISA
Stained organism in pus sample
Culture using selective media
TX: AB [cephalosporin, 3rd generation, quinolones]
Prevention: use
condom, treat partners, treat exposed new borns
Neisseria menigitidis
Meningitis (Epidemics with serotype A.
Transmission: Respiratory droplets
Throat infection à bacteremiaà meningitis, headache, rash
Endotoxin causes severe tissue destruction
50% of cases can be fatal
Affects:
Young children (under 2)
People in crowded areas: dormitories, barracks
DX: organism in CSF
Culture using selective media
TX: AB [penicillin, cephalosporins]
Prevention: Vaccine available for serotype A
OTHER PHYLA (Atypical "G-")
Spirochaetaceae
Gram neg spiral rods
Nonspore former
Low oxygen environment (1-5% O2, 5% CO2 and the rest N2)
Motile with polar flagellae that lie in the preplasmic space between inner and outer membranes
Two Genuses: Treponema and Borrelia
Treponema
Associated with the oral, genital and intestinal tracts
Many species within genus
Pathogens
: Treponema pallidum, Treponema pertenue
Treponema pallidum
Causative agent of syphilis
Endemic in arid countries
Reservoir: human genital tract [STD]
Transmission: Direct: mouth to mouth, sharing of eating/drinking utensils
Clinical signs: papulosquamous erosive lesions that are indurated
Progresses in 6-12 weeks to invade the eyes, skin, blood, CSF
Latent stage: no lesions, but can reappear 1-2 years later
Final stage: affects bones and nervous system (neurosphilis)
Can also be congential : transmitted after
3 months causing abnormalities
Treponema pertenue
Causative agent of yaws
Humid equatorial countries
Transmission: by poor hygiene, skin trauma
Incubation: several weeks
Clinical signs: granulomatous lesion at site of infectionà ulcerate
Can affect bones (periostitis, exostoses)
DX: lesions
IFA
TX: AB {penicillin with doxycycline}
Prevention: safe sex
Borrelia burgdorferi
Causative agent of Lyme Disease
Transmission: Insect vector [Ixodes tick sp.]
Incubation: 6-8 weeks
Clinical signs: Bullseye Rash that expands à Arthritis à Heart, Nervous
DX: clinical signs, history of tick exposure, dark field microscopy
TX : AB [penicillin and tetracyclines]
Prevention: Vaccine,
limit tick exposure
Borrelia recurrentis
Causative agent of Relapsing Fever
Transmission: Insect Vector [Ornithodoros tick sp from rodents., lice]
Incubation: 3-11 days
Clinical signs:
Rashàfever/chills/sweat à headache à hepatomegalyà
Splenomegaly à tachycardia à cardiac failure
Illness ranges from 1-60 days, then asymptomatic. Relapse
Occurs due to cyclic nature of organsim. Will repeat
Several times (2-10 times)
Leptospirosis
Zoonotic diseases [dogs, rats are reservoirs]
Causative agent of Infectious Spirochete Jaundice
Transmission: Direct contact with animal urine or tissue
Indirect exposure to infected soil or water
Portal of entry: abraded skin, mucous membranes
Incubation 1-2 weeks
Disease occurs in phases
Phase 1: headache, fever, chills, muscle aches
Phase 2: fever, meningitis, peripheral neuropathy/ neuritis,
Jaundice, renal abnormalities, blood dyschrasias
DX: culture of blood, urine, or CSF
ELISA
TX: AB [doxycycline]
Spirullum minus
Causative agent of Rat Bite fever
Transmission: Rodent bite
Incubation: 2-3 weeks
Clinical signs: relapsing fever à lymphadentitisà roseolar rashà
endocarditis
DX: ID organism in blood or tissue smears
TX: AB [penicillin with tetracycline]
CHLAMYDIA
“Gram neg” since their cell walls are similar to cell walls of gram neg bacteria
spherical bacteria with both small and large cell types that represent developmental forms of the organism : Small type invades, Large cell divides
Nonmotile, noncapsular
Obligate intracellular parasites of epithelial cells, require use of cell ATP since
They lack cytochromes and flavoproteins
Two main ecological groups
Subgroup A: mammalian parasites of eye and genitourinary tract [STD]
Subgroup B: zoonotic disease for humans (lungs), primarily bird parasites
Virulence factor: surface peptide that resembles heart myosin causing an autoimmune reaction that attacks the heart and helps in formation of arterial plaque
DX: Isolation of organism
IFA
Serum Ab titer
TX: AB [doxycycline,
erythromycin]
Chlamydia trachomonas [Group A]
Causative agent of
Trachoma, conjunctivitis, urethritis,
PID, myocarditis, atherosclerois
Chlamydia pneumoniae [Group B]
Causative agent of bronchitis, sinusitis, pneumonia,
atherosclerosis
Chlamydia psittaci [Group B]
Causative agent of meningopneumonitis, conjunctivitis, abortion,
Endocarditis, hepatic and renal dysfunction
RICKETTSIA
Gram neg (have typical bacterial wall) pleomorphic short rods (dependent on nutrients)
Non motile (except one)
Aerobes, but many require higher CO2 environments
Obligate intracellular parasites
a) need exogenous cofactors: albumin, ATP
b) higly permeable cell membrane
Infect vascular endothelial cells
Vasculitis à capillary dilation à tissue edema & necrosis à organ failure
Transmission: arthropod vectors [lice, fleas, ticks, mites]
Organism multiplies in gut and is shed in feces of vector
Can multiply in salivary gland and are spread in vector saliva during bite
Virulence factor: Endotoxin
DX: ID organism in tissue or blood using special stains
IFA to detect IgM or IgG antibodies
ELISA
CF test called Weil-Felix test
TX : AB [tetracycline]
Prevention: Vaccination for some of the Ricketsia genus
Family of Ricketsia are divided into Genera:
Rickettsia – 11 species, 3 subtypes (Typhus, Spotted Fever, Scrub typhus)
Ehrlichia – 2 species
Coxiella – 1 species
Bartonella –
3 species
Ricketsia ricketsii [Tick vector]
Causative agent of RMSF: fever, headache, chills à rash
Ricketsia prowazekii [louse vector]
Causative agent of
louse-borne typhus fever: fever à maculopapular rash
Ricketsia typhi [Flea vector]
Causative agent of
endemic typhus: fever, myalgia à macopapular rash
Ricketsia akari [Mite vector]
Causative agent of rickettsial pox:
fever à papulovesicular rash
Ricketsia tsutsugamushi [Mite vector]
Causative agent of
scrub typhus: fever à rash
Ehrlichia sp. [Tick vector]
Causative agent of Ehrlichiosis:
thrombocytopenia in animals
Coxiella [No arthropod vector, spread by respiratory droplets, inhale tick feces]
Causative agent of
Q fever: atypical interstitial pneumonia à cardiac
Bartonella henselae
Causative agent of
cat scratch fever : lymphadenopathy
bacillary angiomatosis: angiomas that resemble Kaposi’s sarcoma
MYCOPLASMAS
Small bacteria that lack a rigid cell wall, therefore they do not gram stain
Genetically related to gram positive bacteria, hence their placement in this group.
Pleomorphic, can produce filaments that resemble fungi
Smallest known free living organisms
DX: IFA
Organism culture (takes 3 weeks)
CF
TX: AB [Macrolides: erythromycin, azithromycin; tetracyclines]
Human diseases:
Mycoplasma pneumoniae
Transmission: respiratory droplet
Primary atypical interstitial pneuomonia
Fever, fatigue, dry/hacking cough
Otitis media in adults
Virulence factor: Neuramindase-like adherence
Cytotoxic enzymes
Beta lactam resistance
Mycoplasma hominis [STD]
Colonize the placenta to cause:
Infertility,
spontaneous abortion, still birth
Ureaplasma urealyticum [STD]
Non-gonococcal urethritis, epididymitis
Urinary tract infections