Microbiology Final Lect 10

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- most often encountered organisms
• can be found in almost all natural habitats.
• normal flora of the intestinal tract and are considered opportunistic pathogens.
• They act as opportunistic pathogens when they are introduced into body locations where they are not
normally found, especially if the host is debilitated or immunosuppressed. They all cause the same types of opportunistic infections, namely, urinary tract infections, wound infections, pneumonia, and septicemia
• Many are also possess R (resistance) plasmids. These plasmids are small pieces of circular nonchromosomal DNA that may code for multiple antibiotic resistance

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Gram Negative Rods: Enterobacteriaceae

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Biological Properties of Endotoxins

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- toxic to most mammals.
• The injection of living or killed Gram-negative cells, or purified LPS, into experimental animals causes a
wide spectrum of nonspecific pathophysiological reactions such as:
1.fever
2.changes in white blood cell counts
3.disseminated intravascular coagulation
4.tumor necrosis
5.hypotension
6.shock
7.lethality

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Gram Neg Rods on Macconkey Agar

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• They are grouped based on their ability to metabolize lactose.
• Non-utilizers are usually pathogenic while the lactose utilizers are pathogenic when outside of the GI tract such as in wounds or UTI.

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• Twenty-six genera and over 100 species
• Salmonella Citrobacter Morganella Shigella Enterobacter Yersinia Proteus Serratia Edwardsiella Escherichia Klebsiella Providencia
•cause over 100,000 deaths per year in the United States.

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Enterobacteriaceae

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The most common infection caused by these opportunistic Enterobacteriaceae is a

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UTI

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____ is a result of these opportunistic bacteria getting into the blood. They are usually introduced into the blood from some other infection site, such as an infected kidney, wound, or lung.

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Gram-negative septicemia

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Aerobic pathogens in wound infections

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- Staphylococcus aureus (17%)
- Enterococci (13%)
- Coagulase-negative staphylococci (12%)
- Escherichia coli (10%)
- Pseudomonas aeruginosa (8%)
- Enterobacter species (8%)
- Proteus mirabilis (4%)
- Klebsiella pneumoniae (3%)
- Candida species (2%)

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• pathogenic strains frequent agents of infantile diarrhea – greatest cause of mortality among babies
• causes ~70% of traveler’s diarrhea
• causes 50-80% UTI
• indicator of fecal contamination in water
• can be subdivided according to their somatic (cell-wall) or O antigens and their flagella or H antigens.
• Currently there are over 160 recognized O types and 55 recognized H types making over 8000 possible OH serotypes.
• There are also capsular and fimbrial antigens.

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E. coli

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• Uropathogenic E. coli causes 90% of the ____ in anatomically-normal, unobstructed urinary tracts. The bacteria colonize from the feces or perineal region and ascend the urinary tract to the bladder. Bladder infections are 14-times more common in females than males by virtue of the shortened urethra.
• The typical patient with uncomplicated cystitis is a sexually-active female who was first colonized in the intestine with a uropathogenic E. coli strain. The organisms are propelled into the bladder from the periurethral region during sexual intercourse. With the aid of specific adhesins they are able to colonize the bladder.

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Urinary tract infections

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• affects1/2,000-4,000 infants. Eighty percent of E. coli strains involved synthesize K-1 capsular antigens (K-1 is only present 20-40% of the time in intestinal isolates).
• E. coli strains invade the blood stream of infants from the nasopharynx or GI tract and are carried to the meninges.
• The K-1 antigen is considered the major determinant of virulence among strains of E. coli that cause neonatal eningitis.

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Neonatal Meningitis

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• most common aerobic & non-fastidious bacterium in gut – opportunistic pathogen

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Intestinal Diseases Caused by E. coli

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enterotoxigenic E. coli

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- causes severe diarrhea due to heat-labile toxin & heat-stable toxin – stimulate secretion & fluid loss; also has fimbrae
- Intestinal Diseases Caused by E. coli

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enteroinvasive E. coli

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- causes inflammatory disease of the large intestine
- Intestinal Diseases Caused by E. coli

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enteropathogenic E. coli

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- linked to wasting from infantile diarrhea; O157:H7 strain causes hemorrhagic syndrome & kidney damage
- Intestinal Diseases Caused by E. coli

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• are an important cause of diarrhea in infants and travelers in underdeveloped countries or regions of poor sanitation. The diseases vary from minor discomfort to a severe cholera-like syndrome.
• are acquired by ingestion of contaminated food and water,
• one or more enterotoxins
• Symptoms include diarrhea without fever

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Enterotoxigenic E. coli
ETEC

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• are represented by a single strain (serotype O157:H7), which causes a diarrheal syndrome.
• A frequent life-threatening situation is its toxic effects on the kidneys (hemolytic uremia). Which affects children under 5 years old.
• strains such as O157:H7 are fairly common in cattle. Humans are frequently infected through meat and raw milk, however, it is important to note that recent U.S. outbreaks have been traced to produce such as lettuce and apple juice.
– has recently been recognized as a cause of serious disease (e.g. the Jack-in-the-Box outbreak in the Northwest). Pediatric diarrhea caused by this strain can be fatal due to acute kidney failure (hemolytic uremic syndrome [HUS]).
- also considered to be "moderately invasive".
– produce a toxin that plays a role in the intense inflammatory response

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Enterohemorrhagic E. coli
EHEC

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- This large, non-motile bacterium produces large sticky colonies when plated on nutrient media.
- it's pathogenicity can be attributed to its production of a heat-stable enterotoxin.
- infections are common in hospitals where they cause pneumonia (characterized by emission of bloody sputum) and urinary tract infections in catheterized patients. antibiotic resistance properties.
- species may contain resistance plasmids(Rplasmids) which confer resistance to such antibiotics as ampicillin and carbenicillin.
- Gram neg rod
- Endotoxin- capsule- hard to get rid of

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KLEBSIELLA

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The most clinically important species of the Klebsiella genus

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KLEBSIELLA pneumoniae

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Pneumonia Signs & Symptoms

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- The course is generally rapid. In Klebsiella pneumonia, typical pneumonia are present and often include a cough productive ofreddish "currant jelly" sputum.
• Gram's stain of sputum shows multiple encapsulated gram-negative bacilli. Blood and sputum cultures should be obtained.
• CXR shows involvement of multiple lobes, especially the right upper lobe, with possible abscess formation.

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Klebsiella

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• a respiratory pathogen causing severe (often fatal) community-acquired pneumonia (especially in
alcocholics),
• K. pneumoniae is most commonly found in nosocomial extrapulmonary infections, including UTI's and septicemia and, in infants (rarely), enteritis and meningitis.
• Combination of cephalosporins and aminoglycosides are recommmended, but mortality rates may approach 50%.

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• eleven species of highly motile bacteria.
• Although this bacterium is part of the normal flora of the human intestinal tract, several species cause opportunistic infections of the urinary tract as well as other parts of the body.
• associated with urinary tract and respiratory tract infections.
• Frequently found in post-op wound infections

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Enterobacter spp.

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• red pigmented colonies
• Causes hospital aquired infections (nosocomial) like Enerobacter
• Urinary & respiratory tract infection
• Isolated from sterile saline solution, catheters
• have many antibiotic resistance properties which may become important if the incidence of Serratia infections dramatically increases.

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Serratia marcesens

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currently thought to be the cause of the miraculous blood.

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Prodigiosin-producing Serratia marcescens

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• The most important member of this genus is considered to be, a cause of wound and urinary tract infections.
- strong smell- spore forming

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Proteus & Morganella morganii

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of ___ are sensitive to ampicillin and cephalosporin.

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P. mirabilis

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produces urease& splits urea to CO2 and NH3 to increase pH & therefore facilitate renal stone formation & uroepithelium toxicity

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P. mirabilis-- urinary tract infection

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This bacterium is an invasive pathogen which can penetrate the gut lining and enter the lymphatic system and the blood. Infection, which is usually through ingestion of contaminated foods, can cause a
severe intestinal inflammation called yersiniosis.

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YERSINIA

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Three important species are included in the Yersinia genus

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- Y. enterocolitica and Y. pestis.
Y. enterocolitica is the most often encountered species of Yersinia in the lab.

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• Release of its enterotoxin can cause severe pain similar to that found in patients with appendicitis.
• is easy to identify because it is able to grow in cold temperatures and is motile at room temperature.
• Antibiotic treatment can consist of aminoglycosides, chloramphenicol, or tetracycline.

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Y. enterocolitica

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• Gram-negative, microaerophiles that cause 5- 11% of all diarrhea cases in the US
• Cell motility is achieved through polar flagella which emanate from a curved rod-shaped cell. The unique shape of the cell and flagella are extremely useful in Gram-stain identification.
• They have been isolated from contaminated water, unpasteurized milk and raw and undercooked poultry.
• They are thermophilic (loves temperatures in the range of 42C) , and exhibit a darting kind of motility in wet mounts.

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CAMPYLOBACTER

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gram negative rods that have a characteristic curved or Sshaped forms. They
sometimes look like seagulls wings.

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Campylobacter jejuni

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• Fever , headaches , muscle aches and diarrhea (sometimes with bloody stools) , stomach pain and nausea may be experienced 2 to 10 days after eating the contaminated foods.
• The bloody diarrhea indicates that Campylobacter is an invasive pathogen that infiltrates the lining of the small intestine and excretes toxins that destroy the gut mucosa. Erythromycin is the preferred antibiotic for treatment.
• To prevent this of type of food borne illness , clean hands , utensils and all surfaces that have been in
contact with raw poultry. Cook poultry thoroughly.
• Caused by a helical Gram-negative bacterium that inhabits intestinal tract and oral cavity of humans and animals.
• Animals (poultry and cattle are frequent carriers of the pathogenic form of C. Jejuni). It is transmitted by poorly cooked poultry products, milk and water.
• They survive for long periods in water. Results in diarrhea. A problem for wilderness campers.

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Campylobacteriosis

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• Reservoir: human carriers. Intermediate hosts are shellfish in environments contaminated by fecal
material.
• Frequency is increasing in some countries due to water pollution by fecal material and poor treatment facilities for sewerage drinking water. Found now in shellfish in Louisiana and Texas.
• Disease: Incubation period is hours to 3 or more days. Rapid loss of fluids and electrolytes (watery diarrhea), loss of 10-15 liters of fluids per day, severe abdominal cramps, vomiting, shock and circulatory failure.
• Mortality rate = 50% if untreated.

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Vibrio cholera

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• More commonly, the disease progresses from the first liquid stool to shock in 4-12 hours, with death
following in 18 hours to several days.
• The watery diarrhea is speckled with flakes of mucus and epithelial cells ("rice-water stool") and contains enormous numbers of vibrios.
• The loss of potassium ions may result in cardiac complications and circulatory failure. Untreated cholera frequently results in (50-60%) mortality rates.
• The clinical description of cholera begins with sudden onset of massive diarrhea. The patient may lose gallons of protein-free fluid and associated electrolytes, bicarbonates and ions within a day or two. This
results from the activity of the cholera enterotoxin which activates the adenylate cyclase enzyme in the intestinal cells, converting them into pumps which extract water and electrolytes from blood and tissues and pump it into the lumen of the intestine. This loss of fluid leads to dehydration, anuria, acidosis and shock.

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cholera

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• a halophilic (loves salt) bacterium found naturally in estuarine waters and animals. It was first described as the cause of gastroenteritis in Japan and United States in the estuarine waters of Puget Sound.
• It has a worldwide distribution in estuarine and coastal environments and has been isolated from many species of fish, shellfish, and crustaceans.
• implicated in numerous outbreaks of seafood-borne gastroenteritis in the United States. Between 1971 and 1978, crab, oyster, shrimp, and lobster were implicated in 14 outbreaks, which may have resulted from the consumption of raw or insufficiently heated seafood or properly cooked seafood contaminated after cooking.

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Vibrio parahaemolyticus

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• a rod-shaped, motile bacterium – nonmotile non-spore forming lactose negative.
• There is a widespread occurrence in animals, especially in poultry and swine. Environmental sources of the organism include water, soil, insects, factory surfaces, kitchen surfaces, animal feces, raw meats, raw poultry, and raw sea foods, raw eggs.
• can be subdivided according to their somatic (cell-wall) or O antigens and their flagella or H antigens.
• Currently there are recognized over 50 distinct O types
• There are also over 50 recognized H antigens
• There are also capsular and fimbrial antigens.
• strains may produce a Heat Labile enterotoxin related to the E. coli Heat Labile enterotoxin (LT) or Cholera Toxin (CT).
• Endotoxin – due to LPS layer.

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Salmonella

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• Acute symptoms -- Nausea, vomiting, abdominal cramps, diarrhea, fever, and headache.
• Infective dose -- As few as 15-20 cells; depends upon age and health of host
• 2 to 4 million cases occur in the U.S. annually.
• a demonstrating approximately a 3.6% mortality rate in hospital/nursing home outbreaks, with the elderly being particularly affected.
• All age groups are susceptible, but symptoms are most severe in the elderly, infants, and the infirm.
• AIDS patients suffer frequently (estimated 20-fold more than general population) and suffer from recurrent episodes.

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Salmonellosis

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Salmonellosis Cause of disease

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• Penetration and passage of Salmonella organisms from gut lumen into epithelium of small intestine where inflammation occurs; there is evidence that an enterotoxin may be produced
• Associated Foods:Raw meats, poultry, eggs, milk and dairy products, fish, shrimp, frog legs, yeast, coconut, sauces and salad dressing, cake mixes, cream-filled desserts and toppings, dried gelatin, peanut butter, cocoa, and chocolate.

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S. enteritidis outbreaks

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• The Centers for Disease Control (CDC) has recorded more than 120 outbreaks of S. enteritidis to date, many occurring in restaurants, and some in nursing homes, hospitals and prisons.
• In 1984, 186 cases of salmonellosis (S. enteritidis) were reported on 29 flights to the United States on a single international airline. An estimated 2,747 passengers were affected overall. No specific food item was implicated, but food ordered from the first class menu was strongly associated with disease.
• S. enteritidis outbreaks continue to occur in the U.S. The CDC estimates that 75% of those outbreaks are associated with the consumption of raw or inadequately cooked Grade A whole shell eggs.
• The U.S. Department of Agriculture published Regulations on February 16, 1990, in the Federal Register establishing a mandatory testing program for egg-producing breeder flocks and commercial flocks implicated in causing human illnesses. This testing should lead to a reduction in cases of gastroenteritis caused by the consumption of Grade A whole shell eggs.

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• Source: Water contaminated with feces of carriers
• Some severe epidemics. Now 400-500 cases per year 25% mortality untreated.
• Disease: 10-14 day incubation period. Bacteria attach to small intestinal mucosa and colonize. Penetrate
epithelium and spread to lymphatic system, blood and liver.
• Release endotoxin.

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Typhoid fever Salmonella typhii

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• S. typhi and S. paratyphi A, B, and C produce typhoid and typhoid-like fever in humans.

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Various organs may be infected, leading to lesions.

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S. Typhi

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• Symptoms: fever, headache, abdominal pain and malaise. Skin eruptions containing bacteria may occur. Lasts up to 3 months.
• Can become asymptomatic with bacteria in gallbladder.
• Diagnosis: Cultivation of bacteria from stools, urine or blood. (Widal serological test).
• Permanent immunity results from vaccination.
• Treatment: Antibiotics
• Prevention: Immunization, control of food handlers, Quarantine carriers.

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– pathology consists of mucosal edema, erythema, friability, superficial ulceration,
and focal mucosal hemorrhage
• There are about 25,000 cases per year in the United States and 50,000 deaths per year worldwide primarily in infants and young children. A problem in day care facilities.
• primarily from feces by unwashed hands, food, feces contaminated water and flies. The bacteria invade the colon where they are phagocytosed by macrophages.
• Endotoxins plus exotoxins cause destruction of the epithelium, and mucosal erosion with edema and
inflammation.
• Water stools often with blood and mucus are symptoms. The disease is self limiting and lasts 4-7 days.

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Shigella Dysentery
(Bacillary dysentery or Shigellosis )

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Salmonella S.Typhi

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Salmonella- epithelial cells lining intsetinal tract
1. Salmonella enters an epithelial cell
2. Salmonella multiplies inside the cell
3. Salmonella cross the epithelial cel membrane and enter the lympatic and cardiovascular circulatory systems.

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Shigella

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1. Shigella enters an epithelial cell
2. Shigella miltiplies inside the cell
3. Shigella invades neighboring epothelial cells
4. AN absecess forms as epithelial cells are killed by the infection