Now we're onto a different body system, or rather body systems: the urinary and reproductive systems! This post will be in a similar format to my last post (on the skin and soft tissue). As before, if an organism's name is in red, that means that it's on the game Microbe Invader (http://microbeinvader.com/).
Describe anatomy of the urogenital tract
In case you wanted wayyyyy more detail than necessary:
For this unit, all we need to know is that the upper urinary tract refers to the ureters and kidneys, whereas the lower urinary tract refers to the bladder and urethra. That's it. Seriously.
Outline major urinary tract infections and
causative organisms
I'm going to use a different format for describing UTIs. Instead of describing one organism at a time, I'm just going to discuss UTIs in general. Firstly, I'll define what we're normally talking about when we're talking about UTIs: usually cystitis, or infection of the bladder. There are other places of the urinary tract where infection can occur, but cystitis is generally what we are referring to when we mention UTIs. (Urethritis, which affects the urethra, is usually associated with STDs, prostatitis, or inflammation of the prostate, can cause chronic UTIs in males, and pyelonephritis, or inflammation of the kidneys, can occur if a UTI ascends up the ureters.)
UTIs start off with a pathogen colonising the urethra and moving upwards. In the bladder, the fimbriae of the pathogen can allow the bacteria to attach to the epithelial cells. Usually, the infection stops there. If you're not lucky, the infection can ascend up the ureters, causing pyelonephritis.
There are several main causes of UTIs, including faecal soiling or contamination, urethrovesical reflux (reflux of urine from the urethra to the bladder), prostate seeding (prostatitis causing intermittent UTIs in males), instrumentation (e.g. insertion of a catheter), haematogenous spread (organisms enter via foci- such as tumours or cysts- in the kidney), and incomplete emptying of the bladder. Risk factors include being female (due to the relatively short urethra), sexual activity, altered immunity, abnormalities within the urinary tract (e.g. congenital problems, calculi in the urinary tract), and catheterisation.
E. coli causes the overwhelming majority of UTIs. S. sapro is also quite common in young females, but we're not quite sure why. Other causes of UTIs are Klebsiella, Proteus, Citrobacter, Enterococcus faecalis, S. epidermidis, and S. aureus. (That's a lot of names that I recognise from Microbe Invader!)
Describe genital tract infections and
causative organisms
Neisseria gonorrhoea
N. gonorrhoea causes gonorrhoea, as you've probably already guessed by the name. It causes purulent infection of mucous membranes, with symptoms that manifest differently in males and females. In males, it usually manifests as acute urethritis, followed by discharge. In females, the endocervix is usually infected, and if untreated, upper genital tract infection or pelvic inflammatory disease can occur. Rectal and oropharyngeal gonorrhoea can also occur in both sexes. Gonorrhoea is mostly confined to the genital tract, but a small percentage of patients can get disseminated (blood-borne) infection.
Gonorrhoea, as you probably already know, can be transmitted via sexual contact. It can also be transmitted from mother to child during childbirth. Perinatal gonorrhoea can cause gonococcal ophthalmia (eye disease due to gonorrhoea), especially in developing countries.
Just like so many other bacteria these days, gonorrhoea is starting to develop resistance. Some strains are resistant to β-lactams, which as I've mentioned in PHAR2210, are antibiotics containing the β-lactam ring (penicillins, cephalosporins, and carbapenems).
Gonorrhoea can be diagnosed by direct examination of pus, including a Gram stain. The Gram stain is more accurate in males than in females, and is not recommended for oropharyngeal or rectal specimens (as these specimens may naturally contain other similar-looking species).
Treponema pallidum
T. pallidum is the causative agent of syphilis. Syphilis cannot be cultured in the lab as of yet, so diagnosis is usually made via serology (looking at the blood). Syphilis progresses in three stages: primary, secondary, and tertiary. In the primary stage, there are hard chancres or sores, which are highly infectious. The bacteria then enter the blood and lymph, allowing for systemic distribution. In the secondary stage, circulating immune complexes cause rashes in the mucous membranes of the mouth, throat, and cervix, which are very infectious. Between the secondary and tertiary stage there is often a long latent stage (10-30 years), in which symptoms don't occur. The tertiary stage, usually caused by the body's immune reactions, is pretty nasty. Untreated patients can develop neurosyphilis, which is characterised by a lot of fun symptoms such as personality changes, dementia, seizures, paralysis, and so on.
T. pallidum can be transmitted by sexual contact, though it only has a 20% transmission rate. It can also be transmitted across the placenta to the unborn foetus, often with disastrous effects. If the mother becomes pregnant during the primary or secondary stage of syphilis, stillbirth is likely to occur. If the mother becomes pregnant during the latent stage, the child is likely to have problems with mental development.
Gardnerella vaginalis
Gardnerella, a cocco-bacillus (an oval-shaped bacteria), is one of several different anaerobes that can cause bacterial vaginosis. Symptoms include loose, fishy discharge, and mild irritation. Other diagnostic signs include a high vaginal pH and positive amines test. The presence of clue cells (vaginal cells with bacteria stuck to them) on a wet mount is also diagnostic of bacterial vaginosis. Treatments include metronidazole and tinidazole.
Herpes simplex virus type 2 (HSV2)
HSV2 is the form of herpes most associated with genital warts. Like HSV1, it can enter a latent state in nerve cells and cause recurrent symptoms if activated. HSV2 can cross the placenta, causing abortion, developmental delay, and deafness. There is no cure for HSV2, but acyclovir can alleviate symptoms.
Human Papillomavirus (HPV)
There are more than 60 serotypes of HPV, some of which can cause genital warts and/or certain types of cancer (such as cervical cancer). Warts can be diagnosed by appearance, biopsy, pelvic exam, Pap test, or HPV DNA test. They can be treated with cryotherapy or topical gels. There is now a vaccine that prevents against four strains of HPV, and a newer vaccine that prevents against nine strains is on the way.
Candida
C. albicans and C. glabrata do not just cause paronychia and intertrigo- they are also the second most common cause of vaginitis! Their main symptoms are pruritis and discharge. Candida can be treated by using antifungal pessaries or creams and/or oral antifungals. It is not sexually transmitted, but if relapses are frequent, it might be a good idea to treat any sexual partners as well.
As mentioned in previous post, Candida infections are mainly opportunistic. Risk factors include recent antibiotic use, high oestrogen levels, uncontrolled diabetes, and immune system dysfunction. It can be diagnosed by culturing or examination of wet mount. In contrast to bacterial vaginalis caused by Gardnerella, pH remains normal, and the Amines test is negative.
Trichomonas
Trichomonas vaginalis is an anaerobic protozoan. It causes trichomoniasis, characterised by frothy yellow-green discharge, vaginal soreness, dysuria (pain when urinating), and elevated vaginal pH. It can be diagnosed via wet mount or culture. Treatments include metronidazole and tinidazole, as for Gardnerella.
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