(6) Examples of bacterial pathogen communicable diseases

(6a) Gonorrhoea is a bacterium that is classed as a sexually transmitted disease (STD)

(Neisseria gonorrhoeae or gonococcus bacteria, causes a sexually transmitted infection, STI)

(A sexually transmitted infection can be defined as an infection that is transmitted via body fluids through sexual contact.)

Sexually transmitted diseases are passed on by sexual contact e.g. having unprotected sex when the bacteria can be transferred from one person to another.

A person infected with gonorrhoea bacteria will experience pain on urination and other symptoms include a thick yellow or green discharge from the penis or the vagina.

Gonorrhoea was, and still is, treated with the antibiotic penicillin, but unfortunately, strains of bacteria have evolved that resist this treatment, making it less effective

The best strategy to reduce the spread of gonorrhoea is to treat patients with new antibiotics that the bacteria are not as resistant too AND to use barrier methods of contraception like condoms to prevent infection and spreading by contact.

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(6b) Chlamydia is a kind bacterium that is also classed as a sexually transmitted disease (STD)

(Chlamydia is also described as sexually transmitted infection, STI)

(An STI can be caused by a bacteria, fungus, protist or virus)

(A sexually transmitted infection can be defined as an infection that is transmitted via body fluids through sexual contact.)

Chlamydia bacteria behave like a virus, because they can only reproduce inside a living host cell.

Sexually transmitted diseases are passed on by sexual contact e.g. having unprotected sexual intercourse.

For 70% of women, chlamydia doesn't always produce symptoms BUT it can cause infertility in men and women.

Observed symptoms of chlamydia include: pain when urinating, unusual vaginal, discharge, pain in the tummy or pelvis, pain during sex, bleeding after sex and bleeding between periods

It is possible for chlamydia to be passed on from an infected mother to her child during childbirth.

The spread of chlamydia can be reduced by ...

(i) wearing a condom during sexual intercourse,

(ii) screening individuals, so that if diagnosed, they can be treated with oral antibiotics, and this reduces the time frame in which the infected person could unknowingly pass on the infection.

(iii) refraining from sexual contact.

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Key points Source of information is based on textbooks and syllabus-specifications for students taking the AQA GCSE, Edexcel GCSE and OCR GCSE level biology examinations (~US grades 9-10).

Key points about gonorrhoea and chlamydia

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 Sexually Transmitted Bacterial Infections: Gonorrhoea and Chlamydia

1. What Are STIs?

• Sexually Transmitted Infections (STIs) are diseases passed from person to person through sexual contact (vaginal, oral, or anal).

• Caused by bacteria, viruses, or other pathogens.

• Two common bacterial STIs are gonorrhoea and chlamydia.

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Gonorrhoea

Pathogen: Neisseria gonorrhoeae (a bacterium)

Transmission:

• Through unprotected sexual contact.

• Can also be passed from mother to baby during childbirth.

Symptoms:

• Pain when urinating

• Thick yellow or green discharge from the penis or vagina

• Pelvic pain (in women)

• Swollen testicles (in men)

• Some people may have no symptoms at all.

Complications if Untreated:

• Infertility

• Pelvic Inflammatory Disease (PID) in women

• Increased risk of HIV transmission

• Eye infections in newborns

Treatment:

• Antibiotics (e.g. ceftriaxone)

• However, antibiotic resistance is becoming a serious issue.

Prevention:

• Use of barrier contraception (e.g. condoms)

• Regular STI screening

• Informing partners if diagnosed

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Chlamydia

Pathogen: Chlamydia trachomatis (a bacterium)

Transmission:

• Through genital contact or unprotected sex

• Can also be passed from mother to baby during birth

Symptoms:

• Often no symptoms (especially in women)

• Pain when urinating

• Unusual discharge

• Pain in the lower abdomen

• Bleeding between periods or after sex (in women)

• Swollen testicles (in men)

Complications if Untreated:

• Infertility in both men and women

• Ectopic pregnancy

• PID (Pelvic Inflammatory Disease)

Treatment:

• Antibiotics (e.g. azithromycin or doxycycline)

• Early treatment is highly effective

Prevention:

• Condom use

• Regular screening, especially for sexually active people under 25

• Avoiding sexual contact until treatment is complete

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Why Is This Important in Human Biology?

• Highlights how bacteria can be transmitted through sexual contact.

• Reinforces the importance of early diagnosis and treatment to prevent long-term damage.

• Links to antibiotic resistance, a growing global health concern.

• Encourages understanding of public health strategies like screening and education.

• Supports knowledge of reproductive health, immune response, and disease prevention.

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Quick Comparison Table

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Keywords, phrases and learning objectives for this part on sexually transmitted diseases of  gonorrhoea and chlamydia bacterial infections

Be able to describe the bacterial pathogens gonorrhoea and chlamydia in terms of sexually transmitted communicable diseases.

Be able to describe their characteristic symptoms and effects on the body, and how gonorrhoea and chlamydia infections can be treated.

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