micro sheet # 16 -wafa'a s3aid

View previous topic View next topic Go down

micro sheet # 16 -wafa'a s3aid

Post by Shadi Jarrar on 27/10/2010, 1:24 am

بسم الله الرحمن الرحيم

______________________________________
http://www.mediafire.com/?d23b33bbdjr5ot4
______________________________________
Microbiology

*Contents:
- Neisseria gonorrhea
- Neisseria Meningitidis
-Moraxella, Kingella &Eikenella


Neisseria gonorrhea

-There're two important pathogens: N.gonorrhea & N.meningitides.
-N.gonorrhea is a common of human disease which's rarely associated with mortality, whereas N.meningitides rarely causes disease but it has a high mortality.
-N.gonorrhea is non-encapsulated but it's similar in arrangement to gram –ve diplococci that's usually arranged within or associated with WBCs. And they cause infection of non-ciliated columnar epithelium utilizing its fimbria and outer membrane proteins for attachment; it reaches the sub-epithelium causing neutrophils infiltration and acute infection that stimulate neutrophils.
-Clinical manifestations of N.gonorrhea infection is usually limited to the superficial mucosal surfaces lined with the infected cells non-ciliated columnar epithelium).
-The most important and susceptible areas for infection involve cervix and urethra rectum, pharynx and conjunctiva in females, whereas in males, it causes infection of urethra in particular but it may spread- especially in homosexuals- to the rectum causing proctitis.
-In neonates, it may cause infection of conjunctiva and it may cause pharyngeal infection which can be a focus for the Gonococcemic spread where it causes Gonococcemic infection (the organism spreads to the blood stream).
-Because epithelium that lines the vagina in adult females is resistant (not susceptible to infection by N.gonorrhea but cervicitis may develop instead of vulvovaginitis), vaginitis doesn't occur. Whereas in young females, N.gonorrhea may cause vulvovaginitis because the epithelium is not resistant. >>The epithelium in young females is non-squamous (not resistant) while in adult females it turns into squamous (resistant).
-The mucosal infections are usually characterized by marked neutrophilic responses and purulent discharge.
-The remarkable representation of urethritis and cervicitis is usually resulting from the discharge.
-So the most important presentative feature is urethral discharge and in this discharge organisms can be demonstrated by a gram stain to be within or associated with WBCs (white blood cells).
-The most common symptoms of uncomplicated gonorrhea is the discharge that may range from a very few amount of scanty clear fluid to copious large amount of pus (thick pus), and if the causes are not treated they will cause obstruction of the urinary canal because of the adhesion that results.
-Dysuria is also often present.
-Endocervical infection is the most common form of uncomplicated gonorrhea in women. Manifestations include vaginal discharge and dysuria, but it's very important to point that 50% or more of females don’t show any symptoms unlike males where most cases are symptomatic, the majority of cases in females don’t seek treatment unlike the cases in men which are almost always symptomatic and they seek care but this sometimes can be delayed because of many factors (social or other factors that play a role in this regard).
-Rectal infection is common in about 1/3 of women with cervical infection resulting from autoinoculation with cervical discharge and it is rarely symptomatic.
-Rectal infection in homosexual men is common and of severe symptoms.
-Pharyngeal infection in men or women maybe a focal source of Gonococcemic spread of infection to blood stream.
-Ocular infection is a serious infection that has consequences to the eye (damage to the eyeball and that's why it should be prevented by silver nitrate or other eye drops).
-Disseminated infection results from gonococcus bacteremia; bacteremia spreads the infection to distal sites and the most important complication is dermatitis-arthritis syndrome. Inflammation of the skin and joints which is characterized by chills, fever (fever and chills occur due to bacteremic spread; symptomatic bacteremia).
-Skin lesions involve macular, pustular, necrotic or hemorrhagic lesions and arthralgia that involve hands, feet, elbow due to periarticular inflammation of the tendon sheath so tendonitis or synovial tendonitis may develop in such individuals.
-Patients may develop septic joint with effusion in the infection of the organism in the base of the joint where diffusion can result in a total destruction of the joint as a consequence of such infection. Rarely the organism disseminates the blood stream to the heart which results in endocarditis or meningitis.

Q: But how does it reach the skin in this case?
A: The blood stream can spread to any site of the body, infection start in the columnar non-ciliated epithelium but in most of the cases, infection is limited to that epithelium and it's usually treated but if not, it may cause dissemination to the blood stream and this can lead to the involvement of the skin.

-Gonococci can ascend from the endocervical canal especially in untreated females. The lack of symptoms may lead to neglection and as a consequence, organisms develop resistance and ascend from the cervix to the endometrium and from the endometrium it can pass through fallopian tubes to the ovaries and peritoneum which results in pelvic endometiritis that leads to salpingitis and finally peritonitis.>>SO this can result in a very serious case which is pelvic inflammatory disease(PID). Women has pelvic and abdominal pain, fever, chills and cervical motion tenderness upon examination>> these symptoms are known as PID which results subsequent to untreated gonorrhea and this leads to infertility. The fallopian tube could be obstructed completely and this is one of the causes of infertility.
-Other important cause of infertility is Chlamydia trachomatis, but fortunately it's not very common in our communities; this is because of the conservativeness towards pre-sexuality.
* Complications of PID -if the organism spreads- involve:
-Abscess around ovaries and tubes; production of pus in the peritoneal cavity results in tubo-ovarian abscess which can result in pelvic peritonitis or what's known Fitz – Hugh and Curtis syndrome (an inflammation of Glisson's capsule of the liver).
-As many as 15% of women with complicated cervical infection may develop PID which may cause serious consequences including increase probability of infection and ectopic pregnancy>> this infection needs to be seriously reported. Estimated cases of gonorrhea are actually double or triple the number of reported cases; because of many social factors, fear to be discovered, and fear of blame. Many of those who are infected don't seek medical care, they aren't diagnosed even in the developed countries>> so underreported cases are very common.
-In the states in 1998>>>350,000 cases are reported down from 700,000 cases in 1990
-The spread is increasing NOT decreasing; however, the reported cases are decreasing!
-When Chlamydia or sexually transmitting infections are modernized in the development, reporting is seriously compromised.
>>SO there were drop by 50% of reporting cases of gonorrhea.
-Humans are the only reservoir of infections. The major reservoir is asymptomatic carriers (Females).Females are asymptomatic whereas males are symptomatic; they can't withstand symptoms because these symptoms are serious and severe and that's why they seek medical care.
-Therefore, upon discovery of cases among females, both partners should be treated.
*Transmission is usually done by:
1. Direct sexual contact.
2. Lack of protective immunity; this leads to re-infection due to antigen diversity of strains>> SO there's no long lasting immunity develops through gonorrhea. Individuals might be infected and those with complement deficiency affecting C5-C9 are at high risk for developing gonorrhea.
-This is a very common infection; it's believed that there're two unreported cases for each reported case.
High risks among women 15-19 years and males 20-24 years of age.
-It's usually contracted from a sex partner who is asymptomatic or has minimal symptoms (usually females).
It's estimated that the rate of transmission (efficiency of transmission) after one exposure is about 35% from an infected woman to an uninfected man>> so infection can spread easily among sex partners.
-More than 90% of men with urethral gonorrhea will develop symptoms; however, more than 50% of women will not show that symptoms>> that's why they don't seek medical care.
>>SO gonorrhea has different presentations in women as compared to men. In men; most commonly develops in the form of Urethritis or Epididymitis.
-Most infections among men are acute, annoying and symptomatic usually evident in the form of disuria and urethral discharge (purulent discharge) and this takes place after 2-5 days of incubations>>so most men will seek medical treatment early which prevent the development of obstructed lesions like stenosis of urinary canal, but usually the treatment is Not early enough to prevent transmission of infection to females. Females are infected from males early in the course of the disease (when symptoms are mild or absent).
-The two bacterial agents primarily responsible for urethritis among men are N. gonorrhea and Chlamydia trachomatis that's why it's easy to make diagnosis.
-In women, it causes cervicitis (infection of the cervix), vaginitis (especially in young females), PID>> all these can develop with no symptoms or have atypical indications (subtle, unrecognized sign & symptoms). Often untreated until PID complications develop>> that's why females develop PID before having any manifestations (asymptomatic).
*Pelvic inflammatory disease (PID):
-It may also be asymptomatic, but it's difficult to diagnose because of many false negatives.
-It could be confused with many entities including: abortions, pregnancy, and low abdominal pain.
-It can cause scarring of fallopian tubes leading to infertility or ectopic pregnancy.

*Disseminated Gonococcal Infection (DGI):
- Petechiae & small purplish hemorrhagic spots.
- Pustules on extremities.
- Arthralgias.
- Tenosynovitis.
- Septic arthritis.
- And occasional complications: Hepatitis, Rarely endocarditis or meningitis.
>>SO most complications occur in females due to the delay of treatment.


*Treatment of N.gonorrhea:
-Penicillin is no longer the drug of choice due to:
1. Continuing rise in the MIC.
2. Plasmid-encoded beta- lactamase production.
3. Chromosomally-mediated resistance.
-Some organisms may still susceptible but N.gonorrhea is becoming more & more resistant.
-Uncomplicated infections can be treated with Cephalosporins like Ceftriaxone & Cefixime or maybe treated with Fluoroquinolone.
-And it should be combined with doxycycline or azithromycin for dual infections with Chlamydia; Chlamydia causes urethritis in males & females and that's why it's sometimes wise to use treatments for N.gonorrhea with those for Chlamydia like Tetracycline & Azithromycin.
-Chemoprophylaxis -especially of newborns- is important to prevent development of Ophthalmia neonatorum with 1% tetracycline or 0.5% erythromycin eye ointments.
-Treatment of newborns with opthalmia neonatorum is achieved by ceftriaxone and it should be given very early because damage to eyeball can develop rapidly.
-Measures to limit epidemic N.gonorrhea include education, aggressive detection of cases in these groups among women who sell-up sex or follow-up screening of sexual partners, use of condoms or spermicides with nonoxynol 9 method that can control the spread sperms >>so the only way to spread it by case-finding and treatment of such cases. There're many factors that contribute to persistence of sexually transmitting disease and their spread, ex. Social factors…etc.

** The picture in slide # 26 shows N.gonorrhea being associated within or associated near neutrophils. There're small gram –ve diplococci within neutrophils>>by this characteristic treatment can be initiated.


Neisseria Meningitidis

-It's encapsulated, small gram –ve diplococci.
-It's the 2nd most common cause of meningitis while streptococcus pneumonia is the most common cause within all range groups, it infects previously healthy individuals & the disease progresses rapidly into large threatening condition, death can result within 24 hours of development of meningitis.
- Pathogenicity: its attachment is pili-mediated & also the non-ciliated epithelium of the oropharynx & nasopharynx.
-It usually colonizes the epithelium of nasopharynx & oropharynx & uses pili to attach with receptor-specific colonization.
- Its capsule is antiphagocytic that allows for systematic spread in the absence of specific immunity.
- Toxic effects are mediated by hyperproduction of lipooligosaccarides which is the endotoxin for organisms. They also preduce blebs>>SO meningiococcal polysaccharides provide the basis for grouping of the organism.
- There're 13 serotypes that have been identified & include: A, B, C, H, I, J, K, L, 29E, X , Z, Y & W135.
- Serogroups A, B, C, Y & W135 are responsible for more than 90% of infections. (responsible for the majority of infections).
- Actually, groups A&C are responsible for most epidemics Unlike N.gonorrhea, which has a common spread in forms of epidemic, especially in crowding conditions like schools, military barracks & pilgrimage. This is why pilgrims should be vaccinated against Neisseria. Epidemics are still spread in Africa.

**Diseases Associated with Neisseria meningitides:
*Following dissemination of virulent organisms from the nasopharynx:
-Meningitis
-Septicemia (meningococcemia) with or without meningitis
-Meningoencephalitis
-Pneumonia
-Arthritis
-Urethritis
>>SO its diseases are not limited for the development of meningitis; however, other illnesses may develop.

-The human nasopharnx is the only known reservoir of N.meningitidis; it colonizes the nasopharynx & from there it spreads most commonly near the blood stream or it goes directly to the CNS if the nasopharyngeal structure is compromised but most commonly it spreads to the blood stream.
But it's acquired for individuals who shed the virus in respiratory disease>>so respiratory droplets for those who carry the virus in their nasopharynx or oropharynx (the source of the spread) & then they attach to the non-ciliated columnar epithelial cells of the nasopharynx via pili & they reach the blood stream then the events after the blood stream invasion are not clear.
The integrity of the pharyngeal and respiratory epithelium may be important in protection from invasive disease.
The presence of serum bactericidal IgG and IgM is probably the most important host factor in preventing invasive disease. But deficiencies in the complement system can predispose for the infection with N.meningitidis. Deficiencies in the complement system C5-C8 may lead to 6000 fold increase the risk of predisposing of N.meningitidis.
-The risk among families due to intimate contact may reach 600 times than that of the community>> SO intimate contact is another important factor.

*Pathogenesis of Meningococcal Disease:
- meningococci utilize gangliosides (GD1) and they bind to pili .Organisms are internalized into phagocytic vacuoles, avoid intracellular killing in absence of humoral immunity and complement system IgM or IgG (patients with late complement deficiencies are particularly at risk)>> because of lacking humoral immunity & IgM or IgG in patients with complement deficiency. This is also promoting; because of the antiphagocytic activity. IgM or IgG are required for opsonization and killing for the organism. They can replicate inside cells and they migrate to sub-epithelial space where excess membrane fragments are released; the blebs of the outer membrane are released and the DIC (disseminated intravascular coagulation) causes bleeding and shock.
>> The endotoxin mediates most manifestations which involve hemorrhagic manifestations; this is an example of hyperproduction of endotoxin.

** The picture in slide#33 shows petechiae which are developed subsequent to disseminated intravascular coagulation>> these were pinpoint lesions at the beginning and later on petechiae will be formed.

-Following colonization of the nasopharynx, protective immunity in individuals start to produce antibodies against vaccines that cause infection and this can result in antibodies production which can destroy the organism and cross immunity may develop to the similar polysaccharides and even to other gram –ve bacteria. This results finally in control of infection.
-In those who have a defective immunity and who fail to develop an effective immune response, the organisms can spread near the blood stream to reach meningiococcemia or that can reach meninges causing meningitis, also can reach lungs causing pneumonia & the joints causing arthritis.
-Carriage of N.meningitidis is present in 5-10% of normal individuals and this percentage increases during epidemic periods.
- Nasopharyngeal carriage increases significantly; however, few of those carriers develop disease that's because it produces protective immunity and if individuals fail to develop protective immunity, serious invasions diseases can develop due to N.meningitidis.
-The mildest form is a transient bacteremic illness characterized by fever and malaise that resolves in 1-2 days and immunity will develop causing clearing of infection.
-Acute meningococcemia is more serious and is often complicated by meningitis. Meningococcemia is known to develop:
-Adrenal gland disease
- Hypotension
- Death that's known as (Waterhouse – Friderichsen syndrome).


*Manifestations of meningiococcal meningitis are similar to acute bacteriomeningitis that are caused by other organisms like streptococcus pneumonia, H-influenza and E.coli. >> These Manifestations result from both infection and increased intracranial pressure. Infection promotes inflammatory response, inflammatory response will cause intracranial edema>> intravascular edema will increase intracranial pressure and this leads to severe headache, photophobia, vomiting, papilledema…etc.
-These are the manifestations that are associated with intracranial pressure: chills, fever, and malaise.
- Signs of meningeal inflammation are also present. The onset of meningitis may be abrupt or insidious.
-In contrast, those who are under the age of 2 months they will develop hypothermia instead of having fever; the body temperature drops.
- Neurologic signs are common; convulsions, or signs of meningeal irritation such as cervical rigidity (Brudzinski sign) thoracolumbar rigidity, hamstring spasm (Kerning sign) and exaggerated reflexes are common>>> cervical rigidity is the inability to move the neck; i.e. the neck and the body resist movement. Kerning sign; if you raise your body, you'll flex the knee because of meningeal or exaggerated reflexes.

-The picture in slide#38 shows pinpoint, small perforated lesions called Purpura, then they start to enlarge and they can coalescence together to show this appearance which's called Petechiae>> the whole skin will be involved.

-Fulminant meningococcemia (Waterhouse – Friderichsen syndrome) occurs in 5-15% of patients with meningococcal disease and has a high mortality rate>> mortality in more than 70% of cases.
- It begins suddenly with high fever, chills, myalgias,
Weakness, nausea, vomiting and headache.
- Apprehension, restlessness, and frequently delirium occur within the next few hours.
-Then they develop the skin manifestations, hemorrhagic manifestations, widespread purpuric and ecchymotic skin lesions appear suddenly.
- The meningitis occurs with no signs present.
-Pulmonary insufficiency develops within a few hours and many patients die within 24 hours of being hospitalized despite appropriate antibiotic therapy and intensive care>> This is a very serious complication of meningiococcal infection, meningiococcemia and following it the Waterhouse – Friderichsen syndrome.

-The picture in slide#41 shows bullae or the involvement of skin with hemorrhagic infection.

** Diagnosis of meningiococcal disease:
-It's achieved by obtaining CSF by lumbar puncture from those who are suspected to have this lesion.
-This CSF induced for examination by smears, culture, & antigen detection.
-There are very important changes that occur to the CSF:

1. CSF would be turbid or bloody. Bloody indicates the hemorrhagic lesions, necrotic lesions like those who are associated with Herpetic infection>> SO it's not meningiococcus bacteria in this case.

2. Pressure>> when lumbar punctures are achieved, it's usually released either with high pressure or low pressure. Pressure is very important in this regard plus the turbidity.
>>So this CSF should be tested for bacteria by gram stain and culture. We do gram stain and culture and if gram stain trusted or without waiting for the infection to be trusted, we should initiate treatment imperacly (Imperical therapy) to avoid development of serious forms of the disease like meningitis>> SO treatment should be aggressive, immediate & in the hospital not at homes.

*Antigens: we look for antigens of N. meningitidis by serological test for more than one bacterial type like haemophilus influenza, streptococcus pneumonia, E.coli & Listeria some times.
>> So we look for antigens for more than one type. We also test CSF for cells and chemical substances. Normally the CSF should NOT contain more than five cells per microliter.
-If the number of cells is more than five>> this is an indication for inflammation especially if there're neutrophils. In severe cases the number of neutrophils in the CSF becomes thousands>> SO the presence of neutrophils is another indication.

3. Biochemical test: we test for sugar, proteins & chlor in the CSF.
-Sugar is the most important in all types of meningitis.
-Protein increases in all forms of meningitis whether bacterial or viral.
- Sugar decreases in bacterial infection. But it's Not influenced in viral infections; because bacteria uses sugar to produce energy by glycolysis and that's why normally the sugar (glucose) in the CSF counts for 2/3s of that of blood (ex. If the sugar in the blood is 100, the sugar in the CSF is 70).
- Any decrease in the sugar below 2/3s of blood indicates bacterial infection whereas viruses don't cause decrease in the sugar.
>>So we test for gram stain, culture, antigen detection, blood hematology (test for blood cells in the CSF) & finally biochemical test.
Depending on the result of these tests, we can confirm or exclude the possibility of bacterial infection & treatment should be given accordingly.

**The picture in slide#43 shows stain smear with gram
–ve diplococci associated with WBCs & neutrophils. These neutrophils have engulfed gram –ve diplococci. This is a characteristic to establish diagnosis.

** Slide#44: this is another smear. Culture in selective media, these organisms is very fragile. If the CSF that's collected is kept at room temperature, these organisms can lyse & die>> So diagnosis won't be accurate and that's why it shouldn't be left at room temperature. When CSF is collected, it should be incubated immediately so that the organism can survive and it's better to examine CSF immediately; because it's an emergency situation.

** Chocolate agar media>> the best for isolation of N.meningitidis and by this can start prevention & treatment.

** Penicillin is the drug of choice. There're no strains that are resistant to penicillin among Neisseria. So Neisseria is still susceptible to for penicillin & so increasing the MIC.

** Chloramphenicol is used depending on the area. Now they give Ceftriaxone as an Imperial therapy before availability of results, the treatment based on administration of Ceftriaxone.

- Chemoprophylaxis of close contacts with Rifampin or Sulfadiazine >>if organism is susceptible.


-Polyvalent vaccine containing serogroups A, C, Y, and W135 is effective in people older than 2 years of age for immunoprophylaxis as an adjunct to chemoprophylaxis.
-Serogroup B is only weakly immunogenic and protection must be acquired naturally from exposure to cross-reacting antigens>> Serotype B is not immunogenic, so it's not included in the vaccine. Unfortunately, we can't vaccinate with serotype B because it's a homopolymer that's no-immunogenic that's related to the capsule.
- Humans are the only natural hosts. With vaccination we aim to eradicate the disease.
-Person to person transmission by aerosolization. Those contacts predispose for infection.
- Highest incidence in children younger than five years and particularly those younger than one year of age are commonly colonize nasopharynx of healthy individuals at a rate 5-10% in the inter-epidemic periods outside epidemic itself but during epidemic periods, it reaches 50% or more and diseases occur sporadically or in epidemics.
-Most epidemics are caused by group A strains, less so with B and C strains.

-Group A, C, Y and W132 capsular polysaccharide vaccines are available and can be used to control outbreaks.
- The group B capsular polysaccharide is a homopolymer of sialic acid and is not immunogenic in humans>> That's why it's not antigenic (not immunogenic), it doesn't cause production of antibodies.
- House hold contacts of cases are of increased risk of a disease more than 500-800 in a condition of meningitis due to N.meningitidis among house holder while they should be given chemoprophylaxis until vaccinated with Meningio-Vaccine.

*Kingella and Eikenella are included in the family Neisseria.

*Read slides#49 & 50 (the Dr. read them). But in slide# 50 >> last point…explanation: because it presents in the oral cavity.

**Note: The Dr. didn't read or explain slide# 10 at all.





The End


*Wafa'a Isaid
*Lec#16
*Date of the lec. 24.10.2010
avatar
Shadi Jarrar
مشرف عام

عدد المساهمات : 997
النشاط : 12
تاريخ التسجيل : 2009-08-28
العمر : 26
الموقع : Amman-Jordan

http://jude.my-rpg.com

Back to top Go down

View previous topic View next topic Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum