prep4md: August 2008

August 31, 2008

Stephen Hawking on Charlie Rose Answering Questions on Survival

Listen to Stephen Hawking answering these questions:

What worries you most about the future of the universe?
Is humanities ultimate survival depending on colonizing the solar system?
Do we need to do that (colonize the solar system) by the end of this century?
What are we not doing to prevent these disasters that we absolutely should be doing?
Do you think we will survive climate change?

August 30, 2008

How to Study Microbiology --- "Microbiology Basics"

As with any other subject, when you start studying Microbiology you need to learn the basics and then little by little you can add more details, facts, examples, etc. And that is what Ill be taking about in this series of posts. "Microbiology Basics"

First of all I recommend you read your Professors book, hand-out, or whatever materials your school's microbiology depatment will provide. Then, go ahead and read Clinical Microbiology Made Ridiculously Simple by Mark Gladwin (Author), Bill Trattler (Author). I have read this book two times till now. It is one of my favorite medical review books. If you do not yet have this book yet, be sure to have a look at it becuase you will love it.

In the upcoming posts I will follow the organization that this book uses.

Lets start:

Bacterial Classification:

Because there are many bugs that you will be studying in this subject you will probably find it easier to study and remember the bugs if you put them in clusters.

As long as medically important bacteria are concerned, put in your mind that we have 6 Gram +ve bugs and all the others are Gram -ve.

Of all the Gram +ve bugs only two are cocci and the other 4 are rods. The two cocci are Streptococcus and Staphylococci. Now two of the 4 rods are capable of forming spors, namely, Bacillus and Clostridium. Last two Gram +ve cannot form spores, namely, Corynbacterium and Listeria (this is the only Gram +ve bug has endotoxin).

On the other hand we have one Gram -ve cocci (actually a diplococci), namely, Neisseria, one spiral: Spirochetes and the rest are Gram -ve rods or pleomorphic.

Some odd bugs that you will need to remember:

Mycobacterium--->acid fast stain
Spirochete--->dark field microscopy
Mycoplasma--->no cell wall

Bacterial Virulence:

Virulence depends on the presence of certain cell structures and on bacteria exotoxin and endotoxin, etc.

Simple examples you should have in mind:

Vibrio Cholera--->one flagella
Eschericia coli--->many flagella
Shigella--->no flagella

Flagella are used for movement (chemotaxis) while Pili are used for adhesion and such which are considered virulence factors too. E. coli for instance cannot cause diarrhea without its pili.

Bacterial Toxins:

Exotoxin is produced by both Gram +ve and Gram -ve and they couse stuff like botulism, tetanus, and cholera.
Enterotoxins act on the GIT causing infectious diarrhea (V. cholera, E. coli, ...) or food poisoning (diarrhea and vomiting) as caused by S. aureus.
Pyrogenic exotoxin causes rash, fever, toxic shock syndrome (S. aureus, S. pyogenes)

Treatment:

the most important principle for treatment is to figure out the site of the infection and the causative bug so you can then eradicate it.

*Next time we will have a look at the most medically important bacteria.

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Where will the web go in the next 5,000 days? --- TED --- Video

At the 2007 EG conference, Kevin Kelly shares a fun stat: The World Wide Web, as we know it, is only 5,000 days old. Now, Kelly asks, how can we predict what's coming in the next 5,000 days?

According to him the web will become:

Smarter
More personalized
More ubiquitous

"Kevin Kelly: Predicting the next 5,000 days of the web"

Web 2.0 is a term describing changing trends in the use of World Wide Web technology and web design that aim to enhance creativity, information sharing, and collaboration among users. These concepts have led to the development and evolution of web-based communities and hosted services, such as social-networking sites, video sharing sites, wikis, blogs, and folksonomies. Although the term suggests a new version of the World Wide Web, it does not refer to an update to any technical specifications, but to changes in the ways software developers and end-users utilize the Web.

Web 3.0 is one of the terms used to describe the evolutionary stage of the Web that follows Web 2.0.

Following the introduction of the phrase "Web 2.0" as a description of the recent evolution of the Web, the term "Web 3.0" has been introduced to hypothesize about a future wave of Internet innovation. Views on the next stage of the World Wide Web's evolution vary greatly, from the concept of emerging technologies such as the Semantic Web transforming the way the Web is used (and leading to new possibilities in artificial intelligence) to the observation that increases in Internet connection speeds, modular web applications, and advances in computer graphics will play the key role in the evolution of the World Wide Web.

The Semantic Web is an evolving extension of the World Wide Web in which the semantics of information and services on the web is defined, making it possible for the web to understand and satisfy the requests of people and machines to use the web content. It derives from World Wide Web Consortium director Sir Tim Berners-Lee's vision of the Web as a universal medium for data, information, and knowledge exchange. At its core, the semantic web comprises a set of design principles, collaborative working groups, and a variety of enabling technologies. Some elements of the semantic web are expressed as prospective future possibilities that are yet to be implemented or realized.

August 28, 2008

Squamous Cell Carcinoma --- NEJM --- Image of the week

A healthy 84-year-old woman presented with a 6-month history of a slowly growing asymptomatic lesion on the dorsum of her right hand. Physical examination revealed a keratotic cutaneous horn — approximately 6 to 7 cm in length and yellow-gray in color, with a firm consistency — on the dorsoulnar aspect of the base of the right index finger (also involving the web between the index and middle fingers), without associated lymphadenopathy. The lesion was completely excised surgically. Read full story

August 25, 2008

What ever happened to Patch Adams?

"Dr. Hunter Campbell "Patch" Adams, M.D. (born May 28, 1945 in Washington, D.C.) is an American medical physician, social activist, citizen diplomat, professional clown, performer, and author. He founded the Gesundheit! Institute in 1972. Each year he organizes a group of volunteers from around the world to travel to various countries where they dress as clowns, to bring hope and joy to orphans, patients, and the people. In 1998 he also visited Bosnia, one of the Balkan Peninsula countries torn apart by the war that started after the break-up of Yugoslavia. His life was the template for the plot of the film Patch Adams, starring Robin Williams. Adams is currently based in Arlington, Virginia, where he promotes a different health care model (i.e. one not funded by insurance policies) in collaboration with the institute."

Tonight I watched Patch Adams for the third time (first time as a medical student). I must say it is one of my favorite movies. A great plot, good cause, compassion, a pure love story, excellent acting, and a medical twist. What more could you ask for?

Anyhow, thank God we live in the Internet age, with a click of a button I can look up and see what happened with this guy called Patch Adams and see whether he fulfilled his dream or not. Here are a few links to what I found:

August 19, 2008

Starting Medical School at the age of 52 --- Video

A guy in Canada enrolling in medical school at the age of 52!

Medically Important Parasites + FREE Images (Part IV)

Medically Important Parasites + FREE Images (Part IV)

I am sorry for publishing all these bugs and parasites images all at once but I have a final exam in a couple of days and I could not resist sharing these excellent images with everyone.

Dracunculus medinensis larvae

Female Guinea worm, Dracunculus medinensis, being removed from a sufferer

Again D. medinensis being removed from a patient

Wuchereria bancrofti microfilaria in a thick blood smear

Elephantiasis of leg due to filariasis

Here we see jars of rain water containing larvae of Culex pipiens (the vector of this disease)

Tin cans in open dumps containing water may also contain larvae of any of the three domestic species including Culex quinquefasciatus, Culex pipiens, and Aedes aegypti.

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All images are in the public domain or licensed under a creative commons. Thanks to cdc.gov and wikipedia.org

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August 18, 2008

Medically Important Parasites (nematoda) + FREE Images (Part III)

Medically Important Parasites ( nematoda ) + good quality FREE Images

Ascaris lumbricoids egg

Ascaris lumbricoids adult

Trichuris trichuri adult female

Trichuri trichuri egg

Enterobius vermicularis head

Enterobius vermicularis egg

Ancylostoma caninum attached to intestinal mucosa

Ancylostoma duodenale hookworm's mouth parts

Ancylostoma duodenale or Necator americanus hookworm egg (both eggs are indistinguishable)

Trichostrongylus colubribormis egg

Capillaria species egg

Trichinella spiralis cyst in muscle tissue

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All images are in the public domain and thus are free of any copyright restrictions.
All credit is to cdc.gov
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August 17, 2008

Medically Important Viruses + Images (Part III)

HAV

Hepatitis A, (formerly known as infectious hepatitis), is an acute infectious disease of the liver caused by Hepatitis A virus, which is most commonly transmitted by the fecal-oral route via contaminated food or drinking water. Every year, approximately 10 million people worldwide are infected with the virus. The time between infection and the appearance of the symptoms, (the incubation period), is between two and six weeks and the average incubation period is 28 days. In developing countries, and in regions with poor hygiene standards, the incidence of infection with this virus approaches 100% and the illness is usually contracted in early childhood.

Hepatitis A infection causes no clinical signs and symptoms in over 90% of these children and since the infection confers lifelong immunity, the disease is of no special significance to the indigenous population. In Europe, the United States and other industrialised countries, on the other hand, the infection is contracted primarily by susceptible young adults, most of whom are infected with the virus during trips to countries with a high incidence of the disease. Hepatitis A does not have a chronic stage and does not cause permanent liver damage.

Following infection, the immune system makes antibodies against the hepatitis A virus that confer immunity against future infection. The disease can be prevented by vaccination and hepatitis A vaccine has been proved effective in controlling outbreaks worldwide.

HBV

Hepatitis B virus infects the liver of hominoidae, including humans, and causes an inflammation called hepatitis. It is a DNA virus and one of many unrelated viruses that cause viral hepatitis. The disease, originally known as "serum hepatitis", has caused epidemics in parts of Asia and Africa. Hepatitis B is endemic in China and various other parts of Asia. The proportion of the world's population currently infected with the virus is estimated at 3 to 6%, but up to a third have been exposed. Symptoms of the acute illness caused by the virus include liver inflammation, vomiting, jaundice, and rarely, death. Chronic hepatitis B may eventually cause liver cirrhosis and liver cancer, a fatal disease with very poor response to current chemotherapy. The infection is preventable by vaccination.

HBV

This female Cambodian patient presented with a distended abdomen due to a hepatoma resulting from chronic hepatitis B infection.The incidence of hepatocellular carcinoma (HCC) in patients with a hepatitis-B infection is 12-300 times greater. The HBV DNA is incorporated into the hepatocytic DNA during the disease pathogenic process.

HCV

Hepatitis C virus (HCV) is a small (50 nm in size), enveloped, positive sense single strand RNA virus in the family Flaviviridae. Although Hepatitis A virus, Hepatitis B virus, and Hepatitis C virus have similar names (because they all cause liver inflammation), these are distinctly different viruses both genetically and clinically.

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Summery of hepatitis viruses:

Hepatitis A is a liver disease caused by the hepatitis A virus (HAV), and can affect anyone. In the U. S., hepatitis A occurs in situations ranging from isolated cases, to widespread epidemics.

Hepatitis B is a serious disease caused by a virus that attacks the liver. Known as hepatitis B virus (HBV), it can cause lifelong infection, cirrhosis (scarring) of the liver, liver cancer, liver failure, and death.

Hepatitis C is a liver disease caused by the hepatitis C virus (HCV), which is found in the blood of persons who have the disease. HCV is spread by contact with the blood of an infected person.

Hepatitis D is a liver disease caused by the hepatitis D virus (HDV), a defective virus that needs the HBV virus to exist. HDV is found in the blood of persons infected with the virus.

Hepatitis E is a liver disease caused by the hepatitis E virus (HEV), transmitted in much the same way as hepatitis A virus. Hepatitis E, however, does not occur often in the United States.

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All images are either in the public domain or licensed under a creative commons. Thanks to cdc.gov and wikipedia.org
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August 16, 2008

Medically Important Viruses + Images (Part II)

Rabies

This transmission electron micrograph (TEM) revealed the presence of numerous dark, bullet-shaped rabies virions within an infected tissue sample. Rabies is a preventable viral disease of mammals most often transmitted through the bite of a rabid animal. The vast majority of rabies cases reported to the Centers for Disease Control and Prevention (CDC) each year occur in wild animals like raccoons, skunks, bats, and foxes. Domestic animals account for less than 10% of the reported rabies cases, with cats, cattle, and dogs most often reported rabid.

In non-vaccinated humans, rabies is almost invariably fatal after neurological symptoms have developed, but prompt post-exposure vaccination may prevent the virus from progressing. There are only six known cases of a person surviving symptomatic rabies, and only one known case of survival in which the patient received no rabies-specific treatment either before or after illness onset!

HIV

Scanning electron micrograph of HIV-1 budding from cultured lymphocyte. Multiple round bumps on cell surface represent sites of assembly and budding of virions.

Infection with HIV occurs by the transfer of blood, semen, vaginal fluid, pre-ejaculate, or breast milk. Within these bodily fluids, HIV is present as both free virus particles and virus within infected immune cells. The four major routes of transmission are unprotected sexual intercourse, contaminated needles, breast milk, and transmission from an infected mother to her baby at birth.

Screening of blood products for HIV has largely eliminated transmission through blood transfusions or infected blood products in the developed world. HIV infection in humans is now pandemic. As of January 2006, the Joint United Nations Programme on HIV/AIDS (UNAIDS) and the World Health Organization (WHO) estimate that AIDS has killed more than 25 million people since it was first recognized on December 1, 1981, making it one of the most destructive pandemics in recorded history! In 2005 alone, AIDS claimed an estimated 2.4–3.3 million lives, of which more than 570,000 were children. A third of these deaths are occurring in sub-Saharan Africa, retarding economic growth and increasing poverty.

According to current estimates, HIV is set to infect 90 million people in Africa, resulting in a minimum estimate of 18 million orphans. Antiretroviral treatment reduces both the mortality and the morbidity of HIV infection, but routine access to antiretroviral medication is not available in all countries.

HIV primarily infects vital cells in the human immune system such as helper T cells (specifically CD4+ T cells), macrophages and dendritic cells. HIV infection leads to low levels of CD4+ T cells through three main mechanisms: firstly, direct viral killing of infected cells; secondly, increased rates of apoptosis in infected cells; and thirdly, killing of infected CD4+ T cells by CD8 cytotoxic lymphocytes that recognize infected cells. When CD4+ T cell numbers decline below a critical level, cell-mediated immunity is lost, and the body becomes progressively more susceptible to opportunistic infections.

AIDS

This highly magnified transmission electron micrographic (TEM) image revealed the presence of mature forms of the human immunodeficiency virus (HIV) in a tissue sample under investigation.

The symptoms of AIDS are primarily the result of conditions that do not normally develop in individuals with healthy immune systems. Most of these conditions are infections caused by bacteria, viruses, fungi and parasites that are normally controlled by the elements of the immune system that HIV damages. Opportunistic infections are common in people with AIDS. HIV affects nearly every organ system. People with AIDS also have an increased risk of developing various cancers such as Kaposi's sarcoma, cervical cancer and cancers of the immune system known as lymphomas. Additionally, people with AIDS often have systemic symptoms of infection like fevers, sweats (particularly at night), swollen glands, chills, weakness, and weight loss. The specific opportunistic infections that AIDS patients develop depend in part on the prevalence of these infections in the geographic area in which the patient lives.

Poliovirus

Images like this were used to encourage individuals to receive polio vaccinations, which were made available in April, 1955. Thanks to the successful nationwide immunization program, parents today can rest easy knowing that polio is a preventable viral infection that is only rarely seen today.

Poliovirus

This transmission electron micrograph (TEM) revealed the presence of coxsackie B3 virus particles, which were found within a specimen of muscle tissue. coxsackie B3 virus is a member of the Picornaviridae family of viruses, and the genus, Enterovirus, as is the well-known, nearly eliminated, Poliovirus.

The enteroviruses possess a positive-sense, single-stranded RNA ((+) ssRNA) genome. This virus, as is its brethren the Poliovirus and echovirus, are transmitted via the fecal-oral route, usually due to poor bathroom hygiene, i.e., not wash ones hands after deficating. The enteroviruses, therefore, are known to reside in the carrier’s gut. The coxsackie B viruses is a serotypic group of enteroviruses which can cause mild gastrointestinal maladies, to frank myocarditis and, pericarditis which involves the heart, and the sac in which the heart resides within the chest.

Poliomyelitis

Poliomyelitis, often called polio or infantile paralysis, is an acute viral infectious disease spread from person to person, primarily via the fecal-oral route. Although around 90% of polio infections have no symptoms at all, affected individuals can exhibit a range of symptoms if the virus enters the blood stream. In fewer than 1% of cases the virus enters the central nervous system, preferentially infecting and destroying motor neurons, leading to muscle weakness and acute flaccid paralysis. Different types of paralysis may occur, depending on the nerves involved.

Spinal polio is the most common form, characterized by asymmetric paralysis that most often involves the legs. Bulbar polio leads to weakness of muscles innervated by cranial nerves. Bulbospinal polio is a combination of bulbar and spinal paralysis. Poliomyelitis was first recognized as a distinct condition by Jakob Heine in 1840. Its causative agent, poliovirus, was identified in 1908 by Karl Landsteiner. Although major polio epidemics were unknown before the 20th century, polio was one of the most dreaded childhood diseases of the 20th century in the United States.

Rotavirus

This electron micrograph reveals a number of RNA rotavirus virions, and a number of unknown, 29nm virion particles. A rotavirus has a characteristic wheel-like appearance when viewed by electron microscopy, i.e., rotavirus is derived from the Latin rota, meaning "wheel". Rotaviruses are nonenveloped, double-shelled viruses, making the virus stable in the environment.

Rotavirus is transmitted by the faecal-oral route. It infects cells that line the small intestine and produces an enterotoxin, which induces gastroenteritis, leading to severe diarrhoea and sometimes death through dehydration. Although rotavirus was discovered in 1973 and accounts for up to 50% of hospitalisations for severe diarrhoea in infants and children, its importance is still not widely known within the public health community, particularly in developing countries.

More than 500,000 children under five years of age die from rotavirus infection each year, and almost two million more become severely ill. In the United States, rotavirus causes about 2.7 million cases of severe gastroenteritis in children, almost 60,000 hospitalisations, and around 37 deaths each year.

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All images are in the public domain or licensed under a creative commons. Thanks to wikipedia.org and cdc.gov
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Related posts:

Medically Important Viruses + Images

Warning: this posts contains unpleasant images.

HSV

This 7yr. old child with a history of recurrent herpes labialis presented with a periocular herpes simplex vesicular outbreak.Herpes simplex virus, otherwise known as “Herpesvirus hominis” is a member of a group of viruses including those which cause oral herpes (herpes labialis), i.e., usually HSV-1, and genital herpes, i.e., usually HSV-2.

VZV

This pustulovesicular rash represents a generalized herpes outbreak due to the Varicella-zoster virus (VZV) pathogen.The VZV pathogen may lay dormant in the spinal nerve roots through a chickenpox infected individual’s life, only manifesting its presence through outbreaks as Shingles, or herpes zoster. It is caused by the Herpesviridae chickenpoxvirus.

Influenza virus

This transmission electron micrograph (TEM) of an ultra-thin specimen revealed some of the ultrastructural morphologic features seen in 1918 influenza virus virions. The prominent surface projections on the virions are composed of either the hemagglutinin, or neuraminidase type of glycoproteins. Composed of what looked like dots or tubules, was a dense envelope known as a “capsid”, which surrounded each virion’s nucleic acid constituents.

The flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent this illness is by getting a flu vaccination each fall. Every year in the United States, on average:- 5% to 20% of the population gets the flu;- more than 200,000 people are hospitalized from flu complications, and;- about 36,000 people die from flu. Some people, such as older people, young children, and people with certain health conditions, are at high risk for serious flu complications.

Common cold

This transmission electron micrograph (TEM) revealed the presence of the human parainfluenza type 4A virus (HPIV-4A), which like the mumps virus, is also a Paramyxoviridae family member, and a member of the genus, Rubulavirus. The parainfluenze virus is the cause of a flu-like respiratory infection in humans, very similar to, but not as severe as the flu. Once seen by a physician, a diagnosis of parainfluenza requires treatment of the symptoms, without the requisite antibiotics, which will have no direct affect upon the virus. Symptoms can include mild flu-like symptoms such as a sore throat, cough, upper and/or lower respiratory tract illness, and bronchitis.

Mumps

This child’s face is displaying diffuse lymphedema of the neck due to a mumps virus infection of the parotid salivary glands. Prior to vaccine licensure in 1967, 100,000 to 200,000 mumps cases are estimated to have occurred in the United States each year. Incidence declined to approximately 5,000 cases per year during the period from 1980 to 1990.

Painful swelling of the salivary glands (classically the parotid gland) is the most typical presentation. Painful testicular swelling and rash may also occur. While symptoms are generally not severe in children, the symptoms in teenagers and adults can be more severe and complications such as infertility or subfertility are relatively common, although still rare in absolute terms. The disease is generally self-limited, running its course before receding, with no specific treatment apart from controlling the symptoms with painkillers.

Rubella

The young boy pictured here, displayed the characteristic maculopapular rash indicative of rubella, otherwise known as German measles, or 3-day measles. Rubella is a respiratory viral infection characterized by mild respiratory symptoms and low-grade fever, followed by a maculopapular rash lasting about 3 days. In children there may be no significant respiratory prodrome and the illness may not be diagnosed since the rash may be mild and mimic other conditions. It is estimated that 20-50% of infections are subclinical. Complications occur more frequently in adult women, who may experience arthritis or arthralgia, often affecting the fingers, wrists and knees. These joint symptoms rarely last for more than a month after appearance of the rash.

The rubella vaccine is a live attenuated (weakened) virus. Although it is available as a single preparation, it is recommended that in most cases rubella vaccine be given as part of the MMR vaccine (protecting against measles, mumps, and rubella). MMR is recommended at 12-15 months (not earlier) and a second dose when the child is 4-6 years old (before kindergarten or 1st grade). Rubella vaccination is particularly important for non-immune women who may become pregnant because of the risk for serious birth defects if they acquire the disease during pregnancy. Birth defects if acquired by a pregnant woman: deafness, cataracts, heart defects, mental retardation, and liver and spleen damage (at least a 20% chance of damage to the fetus if a woman is infected early in pregnancy).

Measles

Measles is a disease caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. 'German measles' is an unrelated condition caused by the rubella virus. Measles is spread through respiration (contact with fluids from an infected person's nose and mouth, either directly or through aerosol transmission), and is highly contagious. Airborne precautions should be taken for all suspected cases of measles. The incubation period usually lasts for 4–12 days (during which there are no symptoms). Infected people remain contagious from the appearance of the first symptoms until 3–5 days after the rash appears. In roughly the last 150 years, measles has been estimated to have killed about 200 million people worldwide. In 1954, the virus causing the disease was isolated from an 11-year old boy from the US, David Edmonston, and adapted and propagated on chick embryo tissue culture. To date, 21 strains of the measles virus have been identified. Licensed vaccines to prevent the disease became available in 1963.

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All images are in the public domain or licensed under a creative commons. Thanks to cdc.gov and wikipedia.org

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August 14, 2008

Medically Important Bacteria + Images (part two)

Warning: This post contains unpleasant images.

E coli

Enterotoxigenic Escherichia coli, or ETEC, is an important cause of bacterial diarrheal illness. Infection with ETEC is the leading cause of travelers' diarrhea and a major cause of diarrheal disease in underdeveloped nations, especially among children. ETEC is transmitted by food or water contaminated with animal or human feces. Although ETEC causes a significant amount of illness worldwide, the infection will end on its own and is rarely life-threatening.

Salmonella

Salmonella infections usually resolve in 5-7 days and often do not require treatment other than oral fluids. Persons with severe diarrhea may require rehydration with intravenous fluids. Antibiotics, such as ampicillin, trimethoprim-sulfamethoxazole, or ciprofloxacin, are not usually necessary unless the infection spreads from the intestines. Some Salmonella bacteria have become resistant to antibiotics, largely as a result of the use of antibiotics to promote the growth of food animals.

Salmonella

This 2005 photograph depicted a young boy holding a box turtle, portraying a look of wonderment mixed with curiosity, as the turtle looks on with almost a sense of the nonchalance. The importance of this image lies in the reality that turtles carry germs known as Salmonella, which are potentially dangerous to children. In fact, the sale of turtles less than 4 inches in length has been banned in the United States since 1975. The ban by the U.S. Food and Drug Administration (FDA) has prevented an estimated 100,000 cases of salmonellosis annually in children.

V cholera

This Gram-stain depicts flagellated Vibrio comma bacteria, a strain of V. cholerae; the cause of Asiatic cholera.A person may get cholera by drinking water or eating food contaminated with the cholera bacterium, therefore, inadequate sewerage treatment can facilitate the spread of the disease during epidemics.

V cholera

Here, a cup of typical "rice-water" stool from a cholera patient shows flecks of mucus that have settled to the bottom.These stools are inoffensive, with a faint fishy odor. They are isotonic with plasma, and contain high levels of sodium, potassium and bicarbonate. They also contain extraordinary quantities of Vibrio cholerae bacterial organisms.

Clostridium

This micrograph depicts Gram-positive C. difficile bacteria from a stool sample culture obtained using a .1µm filter. See PHIL 6260 for a black and white version of this image.People can become infected if they touch items or surfaces that are contaminated with feces and then touch their mouth or mucous membranes. Healthcare workers can spread the bacteria to other patients or contaminate surfaces through hand contact.

Clostridium

This neonate is displaying a bodily rigidity produced by Clostridium tetani exotoxin, called “neonatal tetanus”.Neonatal tetanus occurs in infants born without protective passive immunity, because the mother is not immune. It usually occurs through infection of the unhealed umbilical stump, particularly when the stump is cut with an unsterile instrument.

Spirochetes

Using a “darkfield” microscopy technique, this photomicrograph revealed the presence of Treponema pallidum spirochetes, which are the bacterial agents responsible for causing syphilis.“A diagnosis of syphilis is confirmed by using darkfield microscopy to demonstrate T. pallidum in material from suspected lesions, or regional lymph nodes (Creighton, 1990). A positive darkfield result is an almost certain diagnosis of primary, secondary, or early congenital syphilis. In primary syphilis, the darkfield examination may provide a means by which to identify the etiologic agent of syphilis and diagnose the disease before antibodies to T. pallidum can be detected.”

Spirochetes

This patient presented with a penile chancre located on the proximal penile shaft, which was diagnosed as a primary syphilitic infection. Syphilis is an infectious disease caused by the spirochete Treponema pallidum. Primary syphilitic chancres are usually firm, round, small, and painless, and develop at the spot where the T. pallidum bacteria enter the body. The chancre lasts 3 to 6 weeks, and it heals without treatment. However, if adequate treatment is not administered, the infection progresses to the secondary stage.

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All images are in the public domain or licensed under a creative commons. Thanks to cdc.gov and wikipedia.org

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August 31, 2008

August 30, 2008

August 29, 2008

August 28, 2008

August 25, 2008

August 19, 2008

August 18, 2008

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August 16, 2008

August 14, 2008

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