Introduction.Important factsImportant STDsDiscussion about common & important STDs.
STDs, once called venereal diseases, also known asSexually transmitted infections or STI.Defined as the infections that can betransferred from one person to anotherthrough sexual contactMore than 20 STDs have now been identified.Introduction
1. They affect men & women of all backgrounds &economic levels, being most prevalent amongteenagers & young adults, nearly two-thirdsoccur in people <25 yrs.2. The incidence is rising- young people becomesexually active earlier, have multiple sex partners.3. STDs may be asymptomatic, even then infectedperson is capable of transmitting the disease to partner.Important Facts about STDs
4. Some STD can spreadinto the uterus, tubes& ovaries to causePID,which in turn is amajor cause ofinfertility & ectopicpregnancy.5. In female some STDmay be associatedwith cervical cancer.e.g.HPV6. STD can be transmitted verticallyfrom mother to baby before, duringor immediately after birth.7. When diagnosed & treated early, manySTD can be treated effectively.8. Having STD increases the risk forinfection with HIV.5Facts (contd….)
Chlamydia are very small bacteria , obligateintracellular bacteria that grow within cytoplasmicvacuoles, stain poorly with Gram-stain but have thetypical LPS of Gram – ve bact.
Three species for Chlamydia- C. trachomatis.Resp. Tnew genus- C. psittacichlamydophila- C. pneumoniae
Enter through minute abrasions in the mucosal surface.Specific receptors endocytosis C. t vesicle inhibiteLysozyme fusion ( unknown mechanism ) After formation ofmetabolically RBs (binary fission ) 10 hs fresh progeny (within20hs ) release of new EBs to the extracellular environment.Pathogenesis
The lifecycle of Chlamydia. (EB, elementary body; RB, reticulate body.)
Clinical syndromes and complications caused by C.trachomatis, serotypes D-K.
Chlamydial inclusion bodies stained dark brownwith iodine
Direct fluorescent antibody test for Chlamydia trachomatis.Elementary bodies can be seen as bright yellow-green dotsunder the ultraviolet microscope
- The genus Neisseria contains twoimportant human pathogens.N . meningitides(meningococus )N .gonorrhoeae(gonococcus )
They are Gram – ve diplococciObligate human pathogen .Found inside polymorph or pusof the inflammatory exudates.- It is exclusively a humanpathogen
Gonos(seed )Rhoie( flow )- It is classical venereal dis .- Spread almost by sexual contact.- Having a short incubation period.- Easy to diagnose and treat.- It is the 2nd infection in UK , with highest ratesare seen in ♂ ( 20 – 24 ys) and ♀ ( 16 – 19 ys ).
• Cervix• Urethra• Rectum• Pharynx• ConjunctivaInfection is generally limited to ;superficial mucosal surface ẃ is lines écolumnar epith.
Squamous epith . ẃ lines theadult vagina is not susceptible .The prepubertal vaginal epith. ẃhas not been keratinized under theinfluenz of estrogen may beinfected. → as vulvovaginitisNB.
The spread of Neisseria gonorrhoeae isfacilitated by various virulence factors. Changesin the surface structure of the gonococcusrender the organism avirulent
Local and systemic spread of gonococcal infectionand complications
- Gram staining of a smear ( 95% sensitive ).- It is a fastidious microbe ,- Requiring humidity ( 5-7% co2 )and- Complex media for growth……….combination of oxidase + ve coloniesand Gram- ve diplococci provides apresumptive diagnosis .Fluorescent – antibody stainingNB.
-Co – agglutination-Specific biochemical tests ,glucose.oxidase-DNA probes may be used for confirmation- PCR based methods are available in somespecified lab-Blood culture for DGI
- Rapid diagnosis.- Use of effective antibiotics.- Tracing , examination and treatment ofcontacts.– No vaccine till now ;-antigenic variation of the pilli.- outer memb. Ptns are antigenicallyvariable.- lack of suitable animal models.NB.
- Over 120 different types of papilloma viruscan infect humans .- Widely distributed in nature .-papilloma viruses are 55 nm diameter, icosahedral , ds DNA viruses and cause skinpapillomas (warts ) and tumors .- species specific , can be distinct from animalpapilloma viruses .
- They show adaptation to definite sites on thebody ,- At least 40 types including HPV6 , 11 , 16 and18 can infect the anogenital tract and othermucosal areas ( sexually transmitted ).- HPV1 and 4 tend to cause plantar warts.- HPV2 , 3 and 10 to cause warts on the kneesand fingers.- Direct and indirect transmission .- DELETE
HPV2 , HPV3&HPV10 causewarts on theknees andfingers.HPV1 &HPV4tend to causeplantar warts40 types( HPV6,11,16&18)infect the anogenitaltract and othermucosal areas(sexually transmitted)They showadaptationto definitesites on thebody .
- Diagnosis: viruses cannot be cultivatedin the lab. , and at present serologictests are neither useful nor available- DNA detection methods
Types of genital herpes:Herpes simplex virus type 1 (oral herpes)Characterized by lesions or blisters foundon the mouth or lips.Herpes simplex virus 2 (genital herpes)Characterized by lesions found on andaround the genital area.Viral Infections
Genital herpes is generally transmitted by sexualcontact. Direct contact with infected genitals can causetransmission via sexual intercourse, oral-genitalcontact, anal intercourse, Other protected areas of skincan become infected if there is a cut, rash, or sore so thatinfections of the fingers, thighs, or other areas of thebody are also possible.Viral Infections: Genital Herpes
The risk of developing genital herpes in a womanexposed to a symptomatic man is between 80-90%.A man’s risk of developing genital herpes from asingle sexual encounter with an infected woman isabout 50%.Problem: Herpes can spread when aninfected individual displays no symptoms!Viral Infections: Genital Herpes
The treponemas that infect man areobligate human parasitesNo other natural hosts are known .
Non – venereal diseases ( yaws , bejel and pinta )Venereal disease( Syphilis )
-Intimate physical contact- contact é infectious body fluids or- in same instances by fomites
-are slender unicellular helical a spiral rods,motile,é several flagella which do notprotrude into the surrounding medium butenclosed within bacterial outer membrane .-Treponemal flagella are complex ,comprising a sheath and core .
-It has a worldwide distribution.It is the 3rd most frequent STDs in USAIn UK ↑ed 15 – 20 %-Very sensitive to dryning , heat and disinfectants i–ethe organism does not survive well outside the body .-Sexual contact .-Most active age group 15-30 y olds .-Congenital S ( vertical ) in utero or during delivery .-S has been rarely acquired by transfusion of infectedfresh human blood .
- Outer memb. Ptns are associated é adherence tothe surface of host cells.-Produce hyaluronidase ẃ may facilitate perivascularinfiltration .-Spirochetes are coated é host cell fibronectin ẃ canprotect against phagocytosis .-The cell surface rich in lipid and the antigen arecovered , therefore T.P. can survive in the body formany years despite avagorous immune response .- Tissue damage is mostly due to the host response.
-Penetration of intact mucosa or through abraded skin→ local multiplication( very slow by av.3w )infiltration of plasma cells ,polymorph and macrophage.é endarteritis .Spread by lymphatics and blood to any organ .NB.
Adv. Screening.Low cost ,Technical simplicity ,Monitor the efficacy of thetreatment.Disadv. False + ve ( acuteviral , bacterial infection...)VDRLRPRCardiolipin (Ag) + sera → floccultion1st (70%) 2nd ( 100%) late ( 0% )
Fluorescent treponemal antibody absorption ( FTA –Abs ) test.Heated treated serum is 1st absorbed é a suspension ofa non-pathogenic treponema ( ẃ removes non-specific cross-reactive Abs that may be detectedagainst commensal spirochates .1st ( 80% ) 2nd ( 100% ) late ( 95% )Remains + ve following successful therapy.NB.
- T.P. haemagglutination assay ( TPHA )Sera are pre-absorbed.Remain + ve for life .Important for neuro S.1st ( 65 ) 2nd ( 100 ) late ( 95 ) .- T.P. particle agglutination test ( TPPA ).use colored gelatin particles.- ELISA or western blot for IgM in cong.syphilis .- Recently available kits for rapid detection.