Microbial Diseases Flashcards
S. pyogenes
Upper respiratory tract
Gram positive
Beta hemolytic (virulence factor–cytotoxin)
Causes strep throat, middle ear, mammary, impetigo, erysipelas
Opportunistic pathogens
Can cause lethal secondary disease
May carry a lysogenic bacteriophage that encodes strep pyrogenic exotoxins (Spe ABCF)
Act as super antigens
Also contains hylauronidase which can delocalize the pathogen
Can cause scarlet fever, rheumatic fever, glomerulonephritis
Diagnosis and treatment of streptococcal disease
Culture–more sensitive but delay in results
Antigen detection–rapid test
Diphtheria (corneybacterium Diptheriae)
Spreads by airborne droplets
Gram positive rod (acrinobacteria)
Immunization or previous infection provides resistance
Pathogenic strains are lysogens–prophage encodes for powerful exotoxins that inhibits protein synthesis (AB toxin)
Culture: isolated using throat swabs and grown on blood agar with telluride which inhibits other pathogens
Prevented by vaccines, treated with antibiotics–also diphtheria antitoxin
Pertussis (bordetella pertussis)
Gram negative, aerobic
Produces AB toxin exotoxins
Induces cAMP which can lead to tissue damage
Produces endotoxins
Prevented by immunization
Prevention-DTaP vaccine,
Treatment-antibiotics–takes time for antibiotics to “kick in” which may indicate that the immune response is as important as antibiotics
S. Pneumoniae
Virulence factor is its capsule Treated with penicillin Invades lower respiratory tract Alpha hemolytic Gram positive
Gonorrhea
Gram negative, obligately aerobic, parasitic diplococcus
Virulence factors: pili
Diagnosis:
1. Microscopy: sensitive and specific for symptomatic men with urethral discharge; less sensitive for asymptomatic men and endocervical infections; therefore not definitive
Culture: growth on T-M medium, oxidase positive (contains cytochrome c?) other biochem tests
- Nuclei acid amplification tests
Pili of gonorrhea are highly variable and being reinfected with the same strain twice is unlikely; also immune response may not be efficient in general (antibodies are strain specific)
Oral contraceptives raise vaginal pH making it tough for micro flora to outcompete gonorrhea
Antibiotics have been used to treat it but it is highly resistant
Most specimens are not tested for anti microbial resistance because AMR requires culture and gon is usually diagnosed by NAAT (gonorrhea is not testing by automated MIC tests)
Mycobacterium tuberculosis
Gram positive
Takes a long time to culture so dna amplification is used to diagnose
Co-infection with HIV
C-MI playa critical role is prevention of disease after infection
Classified as primary and post-primary infection
Primary infection-hypersensitizes the host to the bacteria and alters individuals response to reinfection–hypersensitivity measured by diagnostic skin test (TB test)
Reinfection from dormant bacteria in lung
Chronic reinfection causes gradual spread of lesions in the lung (aggravates of macrophages wherein TB resides)
Treatment
Anti microbial therapy using 2 major antibiotics
Mycobacterium leprae
Can only be grown on tissue cultures of armadillo (makes it difficult to diagnose)
Pathogenicity caused by DTH and invasiveness
Transmitted by direct contact and airborne droplets
Incubation timers on weeks to years
Treatment
Need to use several antibiotics simultaneously
Neisseria menigitidis
Airborne
Gram negative, nonsporulating, encapsulated, obligately aerobic, oxidase-positive (alpha hemolytic??) diplococcus
Diagnosis similar to gonorrhea–Thayer Martin medium
Isolated from nasopharyngeal swabs, blood, or cerebrospinal fluid
13 strains are based on their antigenic differences in capsules
Treatment: penicillin
Syphilis (treponema pallidum)
May be transmitted with other STIs (gonorrhea)
Increases chances of HIV infection 3-5X
People with HIV and syphilis can transfer HIV easier
Three stages:
1. Chancre, appears at site where infection entered body a few weeks later
2. Patchy hair loss, rash, fever, swollen glands, muscle and joint pain. Syphilis may go into latent or dormant state
3. Affects the brain, blood vessels, heart or bones.
Cannot be cultivated on artificial media; needs rabbit tissue
Identify from lesions (chancre) using microscopy, direct fluorescence antibody test, or NAAT
Blood tests:
Serology–most commonly: agglutination, EIAs, also POC tests
Treated with penicillin in the primary or secondary stages
Chlamydia trachomatis
Non motile. Gram negative, obligate parasite,
Infectious during only one life stage: elementary body for extraceullular survival; reticulate body for intracellular growth and replication (so the stage that causes disease)
Symptoms:
Infection and inflammation of the reproductive tract, urethritis, proctitis, epididymitis–men
Urethritis, endometritis, cervicitis can lead to cervical cancer–woman (although infections may be symptomatic)
Diagnosis:
Must be grown in host tissue, so isolation and identification not straightforward; NAAT recommended
Treatment: antibiotics–no culture=no AMR testing= treatment failure
HSv 1
ds DNA virus
Infects epithelial cells around mouth and lips
May infect other sites
Spread via direct contact and lesions or throat saliva
Increases risk of HIV transmission
Often will lie dormant in host cell and will “reawaken” when host cell because infected by another pathogen or due to bodily stress (think about how cold sores come about when a person is stressed)
HSV2
Infections usually within the anogenital region
Causes painful blisters
Typically transmitted through sex; may be spread when host is symptomatic or asymptomatic
Genital heroes presently incurable, but a number of drugs are successful in controlling the infectious blister stage
Diagnosis:
Clinical, maybe use staining microscopy or direct immunofluoresence, or viral ANTIGEN detection (direct EIAs)
Trichomoniasis (trichomonas vaginalis)
Transmitted via sex, also contaminated toilet seats, paper towels, etc
Localized to the genitourniary tract by the hosts immune system
Increased risk of immune deficiency in both sexes
Males tend to be asymptomatic
Females–vaginal discharge, vaginitis, painful urination,
Diagnosis:
Direct microscopy observation, cell culture, immunoassays, NAAT
Treatment: metronidazole
HIV
Retrovirus
Infects CD4 T lymphocytes and macrophages; eventually prevents cells from dividing, and they diminish, thus lowering immune efficiency
Cytokines production falls,
Diagnosis:
HIV-EIA, confirmed by HIV-immunoblot, or rapid test–however, these fail to detect a person who’s recently been infected
RT-PCR can be used to detect HIV-RNA directly from blood and estimate the viral load; good for early detection and monitoring the progress
Treatment: Reverse transcriptase inhibitors Protease inhibitors Fusion inhibitors Integrate inhibitors
