Module 9 - Specific Bacterial & Protozoan Pathogen

Question 1

Neisseria Spp. (meningicocal):

Answer 1

-neisseria are gram-negative diplococci bacteria that contain endotoxin in their outer membrane

Question 2

(syphilis):

Answer 2

Treponema pallidum
-gram negative spirochete, motile bacteria
-sexually transmitte
-stage 1 = one or more sores where bacteria entered body
-stage 2 = skin rashes/sores on body
-latent or late stage = can go latent for years and then progress to death
-casue miscariage, abnomalies, premature birth
-antibiotics

Question 3

Streptococcus spp.:

Answer 3

-gram positive
-catalase negative
-subtyped by ability to lyse RBC in blood agar:
-alpha-hemolytic = green zone, incomplete lysis
-beta hemolytic = clear zone, complete lysis
-gamma hemolytic = no reaction

Question 4

Streptococcus pyogenes:

Answer 4

gram postive

-acute rheumatic fever (heart issue)
-pharyngitis (strep throat)
-scarlet fever = subtype of GABHS with exotoxin that causes skin blood vessels to open, with RBC entering skin - red rash

Question 5

S. pyogenes - perinatal infection:

Answer 5

-puerperal sepsis (postpartum infection):
-frequently causes GABHS, but other bacteria as well (s.aureus or e.coli)
-infection of the genital tract 24-48 hours after vaginal birth

-necrotizing fasciitis - flesh eating disease (rare):
-progressive GABHS infection that spreads rapidly between the fascia covering muscles and the fat
-women in the postpartum period (often surgical scars) and newborns are at risk (especially at the point of detachment from umbilical cord)

Question 6

Streptococcus agalactiae:

Answer 6

-group b bacteria (GBS)
-beta hemolytic
-major manifestations are congenital pneumonia, sepsis, meningitis

Question 7

Staphylococcus spp.:

Answer 7

-gram positive cocci usually arranged in grape clusters
-three main species of clinical importance: staphylococcus aureus, staphylococcus epidermidis, staphylococcus saprophyticus
-catalase positive (enzyme that neutralises hydrogen peroxide)

Question 8

Staphylococcus aureus:

Answer 8

-coagulase positive: cause clotting of plasma, walls off the infection from immune response
-beta hemolytic
-capable of aerobic and anaerobic metabolismepi
-the nose is the main site of colonisation of S. aureus

Question 9

S. aureus

Answer 9

-toxic shock syndrome
-due to release of TSS toxin (an exotoxin)
-high fever, vomiting, diarrhoea, myalgias, a scarlatiniform rash, and hypotension with cardiac and renal failure in most severe cases
-post surgical wound infections
-treated with vancomycin

Question 10

Staphylococcus Epidermidis:

Answer 10

-normal human flora on the skin and mucous membranes
-major cause of sepsis in neonates
-cause opportunistic infections when the skin is cut or scraped

Question 11

Staphylococcus saprophyticus:

Answer 11

-common urinary tract infection for women following intercourse

Question 12

(e.coli):

Answer 12

-Escherichia coli
-gram negate, rod shaped, motile bacteria
-facultative anaerobe, in normal gut flora
-virulence: (typically an intestinal pathogen)
-adherence of the organism to the cells of the jejunum and ileum by means of pili

-pregnancy and newborn issues:
-uti during pregnancy, most common infection and mothers uti can result in postnatal infection in newborn

Question 13

Clostridium spp.:

Answer 13

-mostly anaerobic
-gram positive, spore forming rods (spores are very resistant to environmental conditions)
-produce exotoxins which cause tetanus, botulism, gas gangrene
-found in soil and in the gut
-many types:
-clostridium tetani - causes tetanus, vaccine available
-clostridium botulinum - causes botulism a type of food poisoning
-clostridium perfringens - gas gangrene
-clostridium difficile -nosocomial diarrhoea

Question 14

Clostridium difficile:

Answer 14

-c. Difficile is the most common nosocomial (disease originating in a hospital) cause of diarrhoea
-usually presents as unexplained diarrhoea after extensive antibiotic therapy
-anaerbe garm positive
-can be fatal in the immunocompromised
-vancomycin and metronidazole might be effective to treat diarrhoea

Question 15

Mycoplasma/ureaplasma infection:

Answer 15

-usually difficult to differentiate the symptoms of infection from chlamydia
-has a cell membrane but no cell wall - therefore it is not penicillin sensitive
-facultative anaerobes
-common cause urethra inflammation
-common species:
-mycoplasma hominis: 20% have this organism → pelvic inflammatory disease
-mycoplasma genitalium: pathology is likely urethritis
-ureaplasma urealyticum: 45-75% have this organisms → may cause urethritis

-pregnancy and fetal issues
-pelvic inflammatory disease
-postpartum endometritis (inflammation of endometrial tissues)
-chorioamnionitis (inflammation of fetal membranes

-can infect in utero or perinatal = speis, pneumonia, cns infection

-treatment = doxycycline or erythromycin

Question 16

Listeria monocytogenes:

Answer 16

-gram negative rod, motile

-contact with infected animals/faeces
-eating unpasteurized milk/soft cheeses or vegetables that are contaminated -pregnancy and fetla/newborn issues:
-in a healthy pregnant women infection is either asymptomatic or mild influenza-like symptoms
-infection of the foetus can occur can lead to death, septicaemia, pneumonia, meningitis
-treatment with ampicillin and/or gentamicin

Question 17

Trichomoniasis:

Answer 17

protozoa trichomonas vaginalis
sexually transmitted
-causes vaginitis (inflammation): foul smelling discharge of shed epithelium
-treatment: metronidazole
-in pregnancy: small risk of preterm delivery, low birth rate, may be acquired by infant during birth (5% of cases)

Question 18

Toxoplasmosis

Answer 18

-caused by toxoplasma gondii
-normally asymptomatic or mild illness
-transmission: ingesting cysts in faeces or poorly cooked meats
-pregnancy and foetal issues
-can be transmitted to foetus in utero
-incidence of foetal infection occurred (higher rate of infection in 3rd trimester, but more severe infection if occurs in 1st trimester)
-may lead to foetal death, convulsions, microcephaly, , jaundice, hydrocephalus, eye infections with symptoms that don’t appear until later in life
-baby can be given medicine

Question 19

Infection of Female Urogenital Tract:

Answer 19

-the urogenital tract is a site of entry for microbes as its a continuous surface so microbes can spread easily from one part to another
-the vagina has no particular cleaning mechanism -> repetitive microtrauma (intercourse, foreign bodies) increase chances for infection
-vaginal epithelial cells contain and secrete glycogen due to the action of circulating estrogens → facilitating lactobacilli to colonise the vagina
-the commensal lactobacilli metabolise they glycogen and produce lactic acid → results in low vaginal pH around 5.0, this inhibits colonisation by all bacteria besides lactobacilli and some streptococci
-normal vaginal secretions contain 10^8 ml of commensal bacteria
-if other microbes attempt to colonise the vagina, they must:
-have specific mechanisms for attaching to vaginal or cervical mucus
-take advantage of tiny local injuries in vaginal tissue
-take advantage of impaired defences: altered immune function in menstrual cycle, or with certain contraceptive hormones (progesterone analogues)

-because of pelvic anatomy, women have more UTIs than men
-short length of female urethra allows for easier access by bacteria to bladder
-proximity of vulva and rectum increases potential for rectal bacteria to colonisation vagina or urethra
-sexual intercourse increases bladder inoculation

Question 20

UTIs in pregnancy:

Answer 20

-urinary bacterial infection is the most common infection during pregnancy
-microbiology lab urinalysis: a colony count = over 100,000 is indicative if infection
-predisposing factors:
-there is significant urethral dilation or reduced urine flow during the second and third trimesters of gestation
-this reduced urine flow and residual urine in the bladder increase risk for bacterial infection

Question 21

Urinary infections during pregnancy:

Answer 21

can lead to kidney infection
-most common bacteria: e.coli

-potential serious outcomes
-maternal sepsis, maternal renal failure
-preterm labour
-systemic sepsis in newborn can cause meningitis, must be treated urgently

Question 22

Our Microbiome:

Answer 22

-we all have a unique microbiome
-Recent research suggests that our microbiome, in particular our gut microbiome, plays a role in our health (ex. Cancer, mental health, autism, obesity, allergy)

Question 23

Chlamydia

Answer 23

-chlamydia trochomatis
-most common sti
-perinatal transmission
-asymptomatic or vaginal discharge, spotting, dysuria
-can cause preterm labour
-eye or lung infection in baby
-antibitoc treatment
-may lead to pelvic inflammatory disease and affect ability to get pregnant

Question 24

Gonnorhea

Answer 24

Neisseria Gonorrhea
-diplococci gram negative
-sti
-perinatal transmission
-asymp or vaginal dischage, dysuria, spotting, pain
-premature labour from
-premature rupture of membranes chorioamnionitis (inflammation of foetal membranes)
-newborn eye infection
-antibiotics