Medically Important Species of Bacteria PDF

**MEDICALLY IMPORTANT SPECIES** - **BACTERIA** There are many different bacteria that exist and can cause infection in humans. However, we shall concentrate on only some of the commonly met forms. Staphylococcus - **Staphylococcus aureus** - - - - - - **Non-bullous impetigo -...

**MEDICALLY IMPORTANT SPECIES** - **BACTERIA** There are many different bacteria that exist and can cause infection in humans. However, we shall concentrate on only some of the commonly met forms. Staphylococcus - **Staphylococcus aureus** - - - - - - **Non-bullous impetigo -- pus/fluid forming, itchy, not painful, honey coloured crusts** Streptococci - Like staphylococci, there are many species of streptococci found normally in the human body. - Gram positive - Certain strains of streptococci cause some of the most serious diseases in humans. - **Streptococcus pyogenes** (strep group A) is the main cause of bacterial pharyngitis (strep throat) in people. Untreated strep throat can lead to serious sequelae like rheumatic fever (heart valves) and glomerulonephritis (kidneys). - Other infections include impetigo and the devastating \"flesh eating bacteria\" otherwise known as necrotizing fasciitis. In necrotizing fasciitis, there is rapid destruction of the soft tissues and muscle. This is a frequently fatal disease and rapid treatment is necessary. - Pharyngitis **THE GRAM-NEGATIVE BACILLI\ ** - There are dozens of different species of gram-negative bacilli, with many species normally found in the intestinal tract. - In the intestinal tract they have a beneficial effect on the body by preventing overgrowth of potential pathogens. However, if by surgery or trauma these bacteria get out of the intestine, they can cause serious, life-threatening disease. - One of the more common gram-negative bacilli that cause disease in humans is **Escherichia coli.** - E. coli is by far the most common cause of uncomplicated community acquired urinary tract infections and is frequently seen in wound infections. - Main cause of gastroenteritis.\ \ Salmonella and Shigella are two gram-negative bacilli well known for being causes of food poisoning and dysentery, respectively.\ \ The gram-negative bacilli have been implicated in infections as diverse as pneumonia to ear infections. Escherichia Coli  Signs and symptoms include: - Diarrhea, which may range from mild and watery to severe and bloody - Abdominal cramping, pain or tenderness - Nausea and vomiting, in some people - Children present with symptoms more than adults - The bacteria can also spread from one person to another, usually when an infected person does not wash his or her hands well after a bowel movement. *E. coli* can spread from an infected person\'s hands to other people or to objects. Treatment - Most people get better in about a week. They often don\'t see a doctor and don\'t know that *E. coli* caused their problems. **Neisseria -- gram negative bacteria\ ** - The majority of Neisseria species are found normally in the mouth and female genital tract. However, there are two species that can cause very serious disease in humans.\ \ **Neisseria gonorrhoeae** is the cause of the sexually transmitted infection gonorrhea. This is a major public health issue in the United States and worldwide. Untreated infections of gonorrhea can lead to more serious disease like gonococcal arthritis and pelvic inflammatory disease (PID). \ \ **Neisseria meningitis** is the causative agent of meningococcal meningitis, a serious, potentially life-threatening disease of the spinal fluid and meninges. **Neisseria -- diplococci bacteris** - Herpesvirus - Adenovirus - Poxvirus - Papovavirus \- Parvovirus \- Hepadnavirus **Examples of RNA Viruses** - Orthomyxovirus - Paramyxovirus - Rhabdovirus - Togavirus - Flavivirus - Bunyavirus - Reovirus - Picornavirus - Coronavirus - Calicivurus - Retrovirus - Arenavirus Influenza virus -- a RNA virus **HIV- RNA VIRUS** FUNGI -- The Pathogens CUTANEOUS MYCOSES\ -DERMATOPHYTOSES EPIDEMIOLOGY - Three genera-Trichophyton, Epidermophyton, Microsporum - ***Anthropophilic***-reside on the human skin - ***Zoophilic***-reside on the skin of domestic and farm animals - ***Geophilic***-reside in the soil - Transmission from humans or animals is by infected skin scales CLINICAL SIGNIFICANCE - DERMATOPHYTOSES - Characterized by itching,scaling skin patches that can become inflamed and weeping - Infection in different sites may be due to different organisms but is given one name Tinea pedis(Athlete\`s foot) - Common organisms are Trichophyton rubrum , Trichophyton mentagrophytes and Epidermophyton floccosum. - Initially between the toes spreads to nails, yellow and brittle - Secondary bacterial infection - Id Reaction (rash spreads to other parts of the body, often the hands and chest.) Tinea corporis( Ringworm) - Epidermophyton floccosum, Trichophyton, Microsporum - Advancing annular rings with scaly center - Periphery of ring area of active fungal growth, usually inflammed and vesiculated - Non-Hairy areas of trunks mostly Tinea capitis( scalp ringworm) - Trichophyton and Microsporum species - Depends on area - Small scaling patches to involvement of entire hair with hairloss - Microsporum infects hair shafts , Wood\`s lamp - More common in children due to medium chain fatty acids Treatment - Samples to be sent for fungal staining and culture - Infected skin may be treated with topical application of antifungal agents miconazole,nystatin and clotrimazole - Refractory lesions oral griseofulvin and itraconazole, terbinafine - Infections of hair and nails usually require systemic ( oral) therapy SUBCUTANEOUS MYCOSES(dermis, subcutaneous tissues and Bone) - Causative organisms reside in the soil and in decaying or live vegetation - Almost always acquired through traumatic lacerations or puncture wounds - Common among those who work with soil and vegetation and have little protective clothing - Not usually transmitted humans to humans - Usually confined to tropics and subtropics with exception of Sporotrichosis in USA **Systemic infections** -   These occur when fungi get into the bloodstream and generally cause more serious diseases. Systemic fungal infections may be caused either by an opportunistic organism that attacks a person with a weakened immune system, or by an invasive organism that is common in a specific geographic area, such as cocci and histoplasma. Unlike superficial infections, systemic fungal infections can be life-threatening. CANDIDIASIS(candidiosis) - *Candida albicans* and other candida species which are normal flora in the mouth, skin , vagina and intestines - *C.albicans* is dimorphic - May occur as a result of overgrowth as suppression of bacteria by antibiotics - Manifestations depend on the site e.g. oral candidiasis and vaginal candidiasis and disseminated candidiasis in cancer patients, post GI surgery and AB\`s, systemic corticosteroids PROTOZOA - *Entamoeba histolytica*  which causes **amoebic dysentery**. The organism produces protective cysts which pass out of the intestines of the infected host and are ingested by the next host (fecal-oral route). - *Acanthamoeba* can infect the **eye, blood, spinal cord, and brain **and is transmitted by waterborne cysts picked up while swimming in contaminated water, crossing the mucous membranes. - *Giardia lamblia* can cause a gastrointestinal infection called **giardiasis**. Cysts pass out of the intestines of the infected host and are ingested by the next host (fecal-oral route). - *Trichomonas vaginalis* infects the **vagina and the male urinary tract**. It does not produce a cysts stage and is usually transmitted by sexual contact. **Emerging micro-organisms** - New microorganisms capable of causing disease in humans continue to be detected. Whether an emerging microorganism develops into a public health threat depends on factors related to the **microorganism** **and its environment**, or the **infected human and his/her environment.** - Such factors include ease of transmission between animals and people and among people, potential for spread beyond the immediate outbreak site, severity of illness, availability of effective tools to prevent and control the outbreak, and ability to treat the disease. SARS - Severe acute respiratory syndrome (SARS) is a viral respiratory illness caused by a coronavirus **(SARS CoV).** - SARS was first reported in Asia in February 2003. The illness spread to more than two dozen countries in North America, South America, Europe, and Asia before the SARS global outbreak of 2003 was contained. - **SARS is a contagious disease that typically leads to a potentially fatal form of pneumonia.** - Experts say that a coronavirus strain which used to only affect small mammals mutated, and then started to infect humans and became human-transmissible (passed from person-to-person). - The pandemic was brought under control in July 2003, thanks to close cooperation between affected countries, according to WHO. During that year, all airline passengers travelling from the affected countries were screened at airports. - In 2004, a small SARS outbreak was reported in China. However, it was not caused by person-to-person transmission, but as a result of contact with a laboratory virus sample. - Unlike smallpox, SARS cannot be eradicated, because it could still be present in animal populations where it could mutate and infect humans. Signs & Symptoms - SARS symptoms usually start off like those of the common cold, and gradually become more flu-like. - Extreme  fatigue (tiredness), malaise (general feeling of being unwell) - Headaches - Fever - above 38 °C (100.4 °F). According to WHO, this is the only symptom that is common to all patients with SARS - Lethargy - Confusion - Rash - Loss of appetite - Myalgia - pain in the muscles. Many describe it as an overall feeling of discomfort, and body aches - Chills - Diarrhea  may affect 10% to 20% of patients - **From 3 to 7 days after exposure, respiratory symptoms develop as infection spreads to the airways and lungs, and may include:** - Dry cough - Runny nose (less common) - Sore throat (less common) - Shortness of breath (breathing problems) - Gradual fall in blood-oxygen level (fatal) - Nearly all patients develop pneumonia after about day 7 **How does SARS spread?** - **An airborne virus** - like influenza (flu) and the common cold, SARS is an airborne virus. It spreads in small droplets of water that infected people sneeze or cough into the air. Others breathe the droplets in and become infected themselves. Those most at risk need to be within three feet of somebody who coughs and sneezes. - **Touching contaminated surfaces** - you can also become infected if you touch a surface that an infected person had previously touched, such as a door handle, elevator button or telephone. Infected people who do not wash their hands after going to the toilet (passing stools) can also spread the disease by touch. Good hand hygiene is extremely important in stemming the spread of SARS. - **Close proximity** - people who care for or live with somebody who is infected with SARS are at very high risk of developing the infection.\ \ Experts believe that SARS also spreads by other ways that are not yet known.  **How is SARS diagnosed?\ ** - There are no rapid screening tests for SARS. - In areas where a SARS outbreak is known, the doctor will order lab tests to be done. - In areas where there is no known SARS outbreak, the doctor may consider the possibility of SARS if the patient has pneumonia which is confirmed by an X-ray, as well as some other details: \- Has the patient recently travelled to an area where there is a SARS outbreak, or known cases of SARS have been reported? \- Does the patient work in a place where there might be a risk of exposure to viruses that cause SARS, such as a laboratory -Does the patient have atypical pneumonia without another diagnosis and is part of a cluster of cases? **Diagnostic laboratory tests for SARS** - There are currently three possible diagnostic tests for SARS, however, each has its limitations: **-ELISA (enzyme-linked immunosorbent assay)** - this test detects SARS antibodies. It is a reliable test, but can only be used 21 days after symptoms started. **-Immunofluorescence assay** - this test can identify antibodies 10 days after symptoms first appear. However, it is time- and labor-intensive and requires an immunofluorescence microscope and people who know how to use the equipment. **-PCR (polymerase chain reaction) test** - this test can detect SARS virus genetic material in samples of stools, tissue, sputum and blood. It is a specific but not very sensitive test. Positive test results nearly certainly mean the person has SARS, while a negative test does not completely rule it out. **\ \ What are the treatment options for SARS?** - **There are no medications which target the SARS coronavirus directly**. - Supportive - helping the patient breathe and keeping the fever under control with supplemental oxygen and ventilation support as well as antipyretics (medications for fever). - Isolation of patient H7N9 - A bird flu strain of the Influenza virus A. - can infect and replicate in a variety of mammals, including humans. - first reported to have infected humans in 2013 in China. - most of the reported cases of human infection have resulted in severe respiratory illness. - does not kill poultry, but can kill humans - information is still limited about the full spectrum of illness that infection with avian influenza A(H7N9) virus might cause. Signs & Symptoms - Fever - cough - shortness of breath, which may progress to severe pneumonia - Blood poisoning - Organ failure **How does H7N9 spread?** - At this point it is not known how persons are becoming infected. Some of the confirmed cases had contact with animals or with environments where animals are housed. - The virus has now been found in chickens, ducks, and captive-bred pigeons at live bird markets near locations where cases have been reported. The possibility of an animal source of the infection is being investigated, as is the possibility of person-to-person transmission. - The eating of well-cooked poultry and eggs does not transmit the virus **\ \ \ How is H7N9 diagnosed?\ ** - real-time reverse-transcriptase--polymerase chain reaction assay - viral isolation - H7N9 serologic testing using modified hemagglutination-inhibition assays. - THANK YOU