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Module: Infection and Immunity
Date: Thursday 28th March
Time: 2 pm - 3 pm
This lecture will look at STDs, then will move onto urinary tract infections and skin infections.
There is some host related information and a focus on the dominant infective agent.
Sexually Transmitted Diseases
Recent incidence 2022 in the UK.
Increases in, chlamydia, syphilis, genital warts.
STDS are a class of infectious diseases spread by contact between individuals. These are non-
gonococcal urethritis, genital herpes, syphilis etc..
Defences – the vagina is protected by:
The understanding or the influence of the microbiome is important in these areas. We will
discuss this in terms of the UTI, skin, and male and female reproductive systems.
1) Combination of host and microbiota surveillance. – A normal symbiotic interaction
between microorganisms and host. Dominated in female reproduction by lactobacilli.
This changes with age, which can affect the presence or absence of lactobacilli. These
produce antimicrobial compounds, lactic acid decreasing the Ph of the vagina.
2) Production of antimicrobial peptides
3) Mannose bonding lectins – bind to inhibit proliferation pathogens.
4) Hormonal effect on vaginal secretion
5) Secretary antibodies especially IgA.
A dysbiosis state releases short term fatty acids, leading to a proinflammatory environment,
causing a breakdown of symbiotic state to dysbiosis state. This leads to breakdown of
cellular structure and upregulation of proinflammatory cytokines. There are a range of
factors that contribute to a dysbiosis state in the vagina. On month to month, your biotic
state fluctuates.
Normal flora
Adult male:
- Skin flora in urethra
- Genital tract is kept clean by secretion from prostate gland and washing action of
urine.
Adult female:
- Lactobacilli
- Diphtheroid
- Anaerobes
- Yeast
Symbiotic state and contamination states, the perineum, the distance between anus and
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, entrance to vagina is different spatially. As they are located close together, women are more
likely to develop an infection.
Normal Flora
Hormones can influence the commensal flora of the reproductive tract. Maternal hormones
are responsible for elevated levels of glycogen in the vagina. Glycogen levels drop and flora
dominated by enterococci and coliform bacteria develops. At puberty glycogen returns with
the lactobacilli. At menopause, glycogen returns to prepubescent state. The vaginal flora is
also in constant flux throughout the menstrual cycle.
Uterine microbiota into reproductive tract
According to some studies the reproductive tract has a microbiota 3-4 community types
(species) of vaginal microbiota. Lactic acid produced by microbiota helps maintain low Ph.
Up until recently the urethra was thought to be sterile.
Recent studies have identified uterine microbiota are different from the vaginal microbiota.
We can cultivate 2% bacteria, if we were to cultivate in this environment you would have
variations. It is now thought in the microbiome, that using culture independent analysis, you
can take the sample, extract DNA, and identify what DNA of what organisms are in that
niche. The microbiota in the uterus can grow in different sources and migrate to the uterus.
Displacement and intro of non-endogenous species can cause infection.
- Lower third of vagina
- Circle mucus
- Posterior Fornax
These are dominated by lactobacilli.
- Fallopian tubes
- Endometrium
These are dominated by non-lactobacilli.
Male genital mucosa microbiome
- Very different to female
- Like skin surface, looking at the variation on site, it is not as marked as the female
microbiome.
- No major role for the protection compared with vagina.
- Not dominated by lactobacilli
- Largely skin microflora.
STDs – dysbiosis is caused by the introduction of an infective agent.
- Viral – Herpes simplex,
- Bacterial – Treponema pallidum
- Fungal- candida albicans (thrush)
- Parasites – scabies, trichomoniases.
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