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Organism Information and Courses from MediaLab, Inc.

These are the MediaLab courses that cover Organism and links to relevant pages within the course.

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Laboratories Individuals

Cerebrospinal Fluid
Specimen Handling and Storage

The stability of the CSF sample varies depending on the procedures ordered. Cell counts are ALWAYS STAT and should be performed within 30 - 60 minutes for best results. Samples should be left at room temperature for no longer than one hour and refrigerated following testing. Refrigeration is not recommended for culture specimens since fastidious organisms such as Haemophilus influenzae and Neisseria meningitidis may not survive the cold temperature.

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Chemical Screening of Urine by Reagent Strip
Urine Specimen

The urine specimen should be freshly voided. Urine is an ideal medium for the proliferation of bacteria due to the large amount of urea present. These bacteria metabolize urea, producing ammonia that increases the urine pH. If there is a delay before performance of the test, the sample should be refrigerated. This will: Prevent urease-producing organisms, such as Proteus and Pseudomonas, from converting urine urea to ammonia, which results in an increased pH. Prevent loss of CO2 which increases pH to the alkaline range.The "run-over" phenomenon may occur if excess urine remains on the strip. The protein area, adjacent to the pH area, contains an acid buffer which may "run-over" the pH portion resulting in an acid reading on a neutral or alkaline urine.

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Test Sensitivity

This test is sensitive to 0.06-0.1 mg/dL nitrite ion in urines with a low specific gravity and ascorbic acid concentrations of less than 25 mg/dL. Pink spots or pink edges should not be interpreted as a positive result because some medications can color urine red or turn red in an acid environment. Any degree of uniform pink color should be considered positive, suggesting the presence of 105 organisms/mL. Detection of low levels of nitrite ion may be enhanced by comparing the activated test strip to a white background. It is important to note that color development is NOT proportional to the number of bacteria present. The test is specific for nitrites and does not react with any other substances normally present in urine. Negative results do not necessarily rule out a urinary tract infection because yeasts or gram-positive bacteria unable to reduce nitrites may be the causative agent.

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CLIA General Laboratory Review
What is the purpose of using methyl alcohol in the gram stain procedure:View Page
A definitive diagnosis of malaria can be made by:View Page

CLIA Microbiology / Serology Review
This suspicious form, shown below at both low (10X) and high dry (40X) power, measures 90 micro meters by 42 micro meters. It was seen in a stool sample.View Page
This parasite is found in blood.View Page
This suspicious form, found in urine, measures 120 micro meters by 50 micro meters.View Page
I reside inside red blood cells, where I grow and grow until the cells are eventually destroyed.View Page
Which of the following statements about Rickettsia is false:View Page
Which of the following organisms is the most common cause of acute cystitis:View Page
The capsular material used to identify capsular subtypes of Pneumococci consists of:View Page
The most frequent cause of bacterial meningitis in older adults is:View Page
Which of the following organisms in most frequently associated with endocarditis:View Page
Which one of the following statements about Coxiella burnetii is not true:View Page
Match the Streptococcal organism with the appropriate group.View Page
Which of the following organisms will give a positive coagulase test:View Page
Which of the following organisms is an obligate intracellular parasite:View Page
VDRL is an example of which of the following types of tests:View Page
The Quelling test is useful for which of the following :View Page
Which of the following is used as the indicator in the rapid carbohydrate utilization tests:View Page
Which two of the following organisms are gram positive:View Page
Which of the following organisms are gram negative:View Page
Which of the following organisms are gram positive:View Page
Which of the following organisms are gram positive:View Page
Which of the following substances produced by Group A Streptococci is responsible for producing type specific immunity:View Page
Gram positive organismsView Page
The slide coagulase test is a rapid method for identifying which of the following organisms.View Page
Which one of the following organisms is typically urease negative:View Page
The oxidase test is used to presumptively identify:View Page
Which one of the following tests would be positive in the presence of Klebsiella:View Page
Which of the following organisms is best visualized by use of a darkfield microscope:View Page
With regard to blood cultures, which blood to broth ratio is most conducive to growth:View Page
On sheep blood agar Haemophilus influenzae may exhibit satellite formation around all but which of the following organisms:View Page
Which one of the following organisms do not usually stain with an acid-fast stain, or one of its variants:View Page
Match type of media on the right with best description:View Page
Which of the following organisms is not an aerobic organism:View Page
Which of the following tests would be used to directly document the presence of a specific organism in a clinical specimen:View Page
MacConkey agar contains all of the following except :View Page
Which of the following specimens would not be considered suitable for anaerobic culture:View Page
Match the organisms on the right with culture medium:View Page
Match the culture media on the right with possible organism on the left:View Page
Match the organism on the right with the most suitable culture media on the left:View Page
Koch's postulates include all of the following except:View Page
Which of the following media is a selective medium for Campylobacter jejuni:View Page
Which of the following organisms is most likely to be associated with gas gangrene:View Page
Which of the following is not true about members of the Enterobacteriaceae:View Page
Match the organisms on the left with their appropriate type on the right:View Page
Match organism on right to common name on the left.View Page
Sheep blood agar contains inhibitors to which of the following organisms:View Page
What is the purpose of using alcohol in the gram stain procedure:View Page
Which of the following best describes the organisms seen in this illustration:View Page
Which of the following best describes the organisms seen in this illustration:View Page
The Thayer-Martin agar plate seen in this illustration exhibits marked growth. The most likely organism found here would be:View Page
Which one of the following organisms is sensitive to bacitracin:View Page
The most likely organism to be cultured on the Lowenstein-Jensen agar slant illustrated here would be:View Page
The McFarland Comparison Card shown in the illustration is used to:View Page

Current Topics in Clinical Microbiology
A 25 year-old female presented in the emergency room with an acute urethral discharge of 2 days duration. A smear for gram stain was obtained (see accompanying image). Many polymorphonuclear leukocytes and intracellular and extracellular gram negative diplococci were observed. Based on the clinical history and the gram stain observation, a diagnosis of gonorrhea can be made.View Page
The positive oxidase reaction as shown in the photograph (yellow arrow) rules out the following two look-alike organisms of N. gonorrhoeae:View Page
ESBL Activity

Illustrated is the picture of the surface of a disk diffusion test including a ceftazidime disk (left) and a combintation ceftazidime/clavulanic acid disk (right).Observe in the photograph that the zone of inhibition around the the combination ceftazidime/clavulanic acid disk (right) is at least 5 mm larger than around the clavulanic acid disk (left).This observation that the presence of clavulanic acid, a beta-lactamase inhibitor, has resulted in such a large increase in the zone of inhibition indicates that an extended spectrum beta lactamase (ESBL)is being produced.When an organism is producing an ESBL, the susceptibility to individual cephalosporins cannot be predicted, thus requiring that each drug must be tested individually.It may be important to detect ESBL-producing stains of K. pneumoniae and E. coli as treatment failure may occur if the wrong cephalosporin is selected.

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Review 1

Garbutt JM. Littenberg B. Evanoff BA. Sahm D. Mundy LM. Enteric carriage of vancomycin-resistant Enterococcus faecium in patients tested for Clostridium difficile. Infection Control & Hospital Epidemiology. 20(10):664-70, 1999OBJECTIVE: To identify independent risk factors for enteric carriage of vancomycin-resistant Enterococcus faecium (VREF) in hospitalized patients tested for Clostridium difficile toxin.PATIENTS: Convenience sample of 215 adult inpatients who had stool tested for C. difficile between January 29 and February 25, 1996.RESULTS: 41 (19%) of 215 patients had enteric carriage of VREF. Five independent risk factors for enteric VREF were identified: (1) history of prior C. difficile infection, (2) parenteral treatment with vancomycin for > or = 5 days, (3) treatment with antimicrobials effective against gram-negative organisms, (4) admission from another institution, and (5) age > 60 years. These risk factors for enteric VREF were independent of the patient's current C. difficile status.CONCLUSIONS: Antimicrobial exposures are the most important modifiable independent risk factors for enteric carriage of VREF in hospitalized patients tested for C. difficile.

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Review 2

Suppola JP. Kuikka A. Vaara M. Valtonen VV. Comparison of risk factors and outcome in patients with Enterococcus faecalis vs Enterococcus faecium bacteremia. Scandinavian Journal of Infectious Diseases. 30(2):153-7, 1998.The purpose of our study was to determine retrospectively the risk factors for the acquisition of Enterococcus faecalis vs E. faecium bacteremia, as well as the clinical outcomes of these patients.62 patients with Enterococcus faecalis bacteremia were compared to 31 patients with E. faecium bacteremia. Haematologic malignancies, neutropenia, high-risk source and previous use of aminoglycosides, carbapenems, cephalosporins and clindamycin were significantly associated with E. faecium bacteremia. Instead, urinary catheterization was found to be related to Enterococcus faecalis bacteremia. The mortality rates within 7 d and 30 d were 13% and 27%, respectively, in patients with E. faecalis bacteremia and 6% and 29%, respectively, in patients with E. faecium bacteremia.There was no difference in mortality between E. faecalis and E. faecium bacteremia, nor was there a difference in seriousness of disease at the time of bacteremia. In the subgroups of patients with monomicrobial or clinically significant E. faecalis vs E. faecium bacteremia, the mortality rates were similar to the results of all subjects.Our results do not support the theory that E. faecium would be a more virulent organism than E. faecalis

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The most important modifiable risk factor for enteric colonization with vancomycin-resistant Enterococcus faecium is:View Page
Review 1

Lorimer JW. Eidus LB.: Invasive Clostridium septicum infection in association with colorectal carcinoma. Canadian Journal of Surgery. 37:245-9, 1994The association between invasive Clostridium septicum infection and colorectal carcinoma is examined by the presentation of three cases and a review of the literature.In the first two cases the patients presented with nontraumatic metastatic clostridial gas gangrene.In the third case a patient with chemotherapy-induced myelosuppression from concomitant multiple myeloma had a necrotizing transmural infection of the right colon.The apparent portal of entry of Clostridium septicum was an occult carcinoma of the ascending colon. The increasing evidence for a strong link between this organism and some cases of neutropenic enterocolitis is reviewed.

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Review 2

Citron DM. Appelbaum PC.: How far should a clinical laboratory go in identifying anaerobic isolates, and who should pay? Clinical Infectious Diseases. 16 Suppl 4:S435-8, 1993Identification of anaerobic bacteria in specimens from sites of infection due to mixed organisms can be time-consuming and expensive. Laboratories should limit anaerobic workups by testing only those specimens that have been properly collected and transported to the laboratory.Use of selective and differential media for initial processing can provide rapid and relevant information to the clinician. Anaerobes isolated from normally sterile sites and sites of serious infection should always be completely identified. Group-or genus-level identifications may suffice in other instances.The Bacteroides fragilis group of organisms should always be identified because of their virulence and resistance to many antimicrobial agents.Some of the other organisms that warrant identification include Clostridium septicum (associated with gastrointestinal malignancy); Clostridium ramosum, Clostridium innocuum, and Clostridium clostridioforme (which are resistant to antibiotics); Clostridium perfringens (a cause of myonecrosis and gas gangrene,potentially serious infection); anaerobic cocci (which may be resistant to metronidazole and clindamycin); and fusobacteria (which may be virulent and resistant to clindamycin and penicillin).

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A clinical condition often associated with Streptococcus milleri (anginosus) is:View Page
Review 1

Piscitelli SC., Shwed J., Schreckenberger P., Danziger LH. Streptococcus milleri group: renewed interest in an elusive pathogen. European Journal of Clinical Microbiology & Infectious Diseases.11:491-8, 1992The following review examines the bacteriological characteristics, epidemiology, pathogenicity and antimicrobial susceptibility of the "Streptococcus milleri group". "Streptococcus milleri group" is a term for a large group of streptococci which includes Streptococcus intermedius, Streptococcus constellatus and Streptococcus anginosus.Usually considered commensals, these organisms are often associated with various pyogenic infections including cardiac, intra-abdominal, subcutaneous and central nervous system infections, particularly with the formation of abscesses.Organisms of the "Streptococcus milleri group" are often unrecognized pathogens due to the lack of uniformity in classifications and difficulties in microbiological identification. Penicillin G, cephalosporins, clindamycin and vancomycin all possess activity against these streptococci.Use of agents with poor activity may promote infections with "Streptococcus milleri group" and allow it to exhibit its pathogenicity. An understanding of these organisms may aid in their recognition and proper treatment.

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Review 1

Spencer RC.: Invasive streptococcEuropean Journal of Clinical Microbiology & Infectious Diseases. 14 Suppl. 1:S26-32, 1995.Before the introduction of antibiotics, serious infections caused by Streptococcus pyogenes (Lancefield Group A streptococci) were common. Before World War II, this bacterium was responsible for as many as 50% of postpartum deaths and was the major cause of death in patients with burns. Also common were the sequelae of streptococcal infections-rheumatic fever and post-streptococcal glomerulonephritis.With the use of penicillin, however, Streptococcus pyogenes was believed to be virtually eliminated as a pathogen. The organism was consigned to the history books, but not for long.In the mid-1980s, focal resurgences of rheumatic fever began to be reported from different areas in the USA, such as Salt Lake City, Utah. In such communities, where increases in cases of rheumatic fever had been reported, the serotypes M-1, 3, 5, 6 and 18 were isolated which, on culture, produced characteristic mucoid colonies. At the same time, reports of increases in invasive streptococcal disease began to surface in both the USA and Europe.Two syndromes were described; invasive streptococcal infection, occurring in previously healthy children and adults, commonly associated with septicaemia resulting from a deep focus of infection such as bone or lung; and streptococcal toxic shock syndrome, involving a cutaneous focus, accompanied by necrotizing or bullous soft tissue changes. Septicaemia is rare in streptococcal toxic shock syndrome, but the most characteristic feature is one of rapidly progressing multi-organ failure. A high proportion of the strains of Streptococcus pyogenes associated with this condition are serotype M-1, and fatality rates approaching 50% have been reported.

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Clinical History

The prototype history for this organism is either a still birth or a neonate with death ensuing within 2 or 3 days post-partem due to high fever, sepsis, and respiratory distress. The mother usually experienced a flu-like illness late in the third trimester of pregnancy, characterized by low-grade fever, myalgias, malaise and backache. In this case, biopsy material of brain tissue obtained at autopsy was submitted to the pathology laboratory for tissue diagnosis and fluid from the pia-arachnoid was sent to the microbiology laboratory for culture.

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A Brown and Brenn gram stain was performed on one of the tissue biopsy specimens. Organisms were seen as shown in the photograph. Based on the history and the appearance of the bacteria, the most likely identification is:View Page
Listeria gram stain

Photomicrograph of a gram stain prepared from an 18 hour old broth culture.The organism is a small, non-spore-forming bacillus measuring between 0.4 to 0.5um by 1.0 to 3.5um.Coccobacillary forms, diplobacilli, and bacilli in short chains or in diphtheroidal clusters (upper right in photograph) may all be observed in gram stain preparations.When found in the CSF, the organism may be found both intracellularly and extracellulary.

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Each of the following is related to the virulence of Listeria monocytogenes except:View Page
Each of the following factors has led to the current increase in incidence of listeriosis except:View Page
In view of the feedback to the previous question, the clinical correlation does not seem to fit in this case. Most likely:View Page
Review 2

Griego RD. Rosen T. Orengo IF. Wolf JE.: Dog, cat, and human bites: a review. Journal of the American Academy of Dermatology. 33:1019-29, 1995It is estimated that half of all Americans will be bitten by an animal or another human being during their lifetimes. The vast majority of the estimated 2 million annual mammalian bite wounds are minor, and the victims never seek medical attention. Nonetheless, bite wounds account for approximately 1% of all emergency department visits and more than $30 million in annual health care costs.Infection is the most common bite-associated complication; the relative risk is determined by the species of the inflicting animal, bite location, host factors, and local wound care. Most infections caused by mammalian bites are polymicrobial, with mixed aerobic and anaerobic species.The clinical presentation and appropriate treatment of infected bite wounds vary according to the causative organisms. Human bite wounds have long had a bad reputation for severe infection and frequent complication. However, recent data demonstrate that human bites occurring anywhere other than the hand present no more of a risk for infection than any other type of mammalian bite.The increased incidence of serious infections and complications associated with human bites to the hand warrants their consideration and management in three different categories: occlusional/simple, clenched fist injuries, and occlusional bites to the hand. This article reviews dogs, cat, and human bite wounds, risk factors for complications, evaluation components, bacteriology, antimicrobial susceptibility patterns, and recommended treatments. Epidemiology, clinical presentation, and treatment of infections caused by Pasteurella multocida, Capnocytophaga canimorsus, Eikenella corrodens, and rhabdovirus (rabies only) receive particular emphasis.

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HIPAA Privacy and Security Regulations
Case Study: De-identified Health Information. You work in a laboratory microbiology department which provides a local nursing home with information about the effectiveness of various antibiotics it uses to treat infections. You print the requested information, including complete patient identification, bacterial organisms identified, and their sensitivity to various antibiotics. What information should you provide to the nursing home?View Page

Introduction to Bioterrorism
Biological Agents

Biological agents are organisms or toxins that can kill or incapacitate people, live stock, and crops. The three basic groups of biological agents that would likely be used as weapons are bacteria, viruses, and toxins. Biological agents can be dispersed as aerosols or airborne particles.

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Agent: Pneumonic plague (Bacterium)

Most likely means of dissemination: AerosolPrimary route of entry: InhalationGeneral signs and symptoms: High fever, chills, headache, coughing up of blood (hemoptysis), and toxemia, progressing rapidly to difficulty in breathing (dyspnea), and bluish discoloration of the skin and mucous membranes (cyanosis).There is another form of the disease called “bubonic plague”. While it is caused by the same organism, it is not transmissible through human contact. Pneumonic plague is transmissible through human contact.

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Laws and Rules of the Florida Board of Clinical Laboratory Personnel
Description of Specialties (1)

Specialists in microbiology perform testing to diagnose and stop the spread of infectious organisms, including bacteria, viruses, and parasites. Specialists should be able to isolate and identify a wide variety of these organisms. Testing procedures include direction examination and antigen detection methods. Specialists in serology and immunology measure antibodies to infectious organisms. Specialists should be familiar with all serology techniques (except those specific to immunohematology). This specialty includes all lab procedures performed in the specialty of histocompatibility. Specialists in hematology must be able to identify and evaluate cells in blood and bone marrow and identify disorders of these cell. Specialists should be familiar with routine and special tests to determine the number, morphology, and function of cells in body fluid.

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Mycology: Yeasts and Dimorphic Pathogens
Arrange the fungal species that are listed in the drop-down box according to length of time of recovery in primary culture; from most rapid to the slowest.View Page
Match the complications that are most likely to be associated with each of the two yeast diseases that are listed in the drop-down box:View Page
The growth of the yeast-like colonies shown in the upper image was obtained on blood agar from a skin culture only in the area overlaid by virgin olive oil. The lower image is a photomicrograph of a lactophenol blue mount made from a portion of the colony. The disease associated with this fungus is:View Page
This photomicrograph is an acid-fast stained smear prepared from a yeast colony growing on ascospore agar. A helmet-shaped, red-staining, acid fast yeast cell is seen in the center of view at the tip of the arrow, against the background, blue-staining blastoconidia. The presumptive identification of Hansenula anomala was made. Predisposing conditions that may indicate that this isolate is more than a contaminant include:View Page
The ability of Candida albicans to alternate between two phenotypes, which may be related to the virulence of this species, is called:View Page
Each of the following is considered to be a virulence factor in Cryptococcus neoformans except:View Page

Normal Peripheral Blood Cells
Cellular Immunity

Cellular immunity includes delayed hypersentivity reactions, graft rejection, graft-versus-host reactions, defense against intracellular organisms, and probably defense against neoplasms.Cellular immunity is mediated by lymphocytes which we call T-cells.T-cells are so named because they are dependent on the thymus for their production and development.The majority of T-cells are long-lived with an average lifespan of 4.4 years, but it is known that some survive for as long as 20 years or more.T-cells are capable of leaving and re-entering the circulation many times during their long life.T and B cells cannot be differentiated when viewing blood films.They are identified through the use of immunologic cell markers.

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OSHA Bloodborne Pathogens
You Are At Risk!

As a healthcare worker, you come into contact with bloodborne pathogens. These are infectious organisms, usually viruses, which live in human blood and other potentially infectious body fluids.The most important ones are... Hepatitis B Virus (HBV) Human Immunodeficiency Virus (HIV)

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Phlebotomy
Discussion

This phlebotomist violated hospital procedures in several ways that could adversely impact patient care: Cleaning the site only with alcohol, not iodine, could result in a false-positive contaminated blood culture. This might result in the patient receiving unnecessary intravenous antibiotics, and could prolong the patients hospital stay unnecessarily. Drawing both cultures at the same time lessens the chance of recovering a bloodstream organism.Drawing both cultures from the same site might result in both of them being contaminated, making it very difficult for the physician to distinguish contamination from a “real” bloodstream infection.Relevant topics:Blood cultures: introduction, Avoid skin contamination, Blood culture site preparation 1, Blood culture site preparation 2

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Blood culture bottles

Are used to collect sterile blood samples from patients who may be septic (have bacteria or other organisms growing in their bloodstream). Different blood culture bottles are used for aerobic, anaerobic, and pediatric collections.

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Introduction

Blood is normally sterile. Any bacterial growth in the bloodstream is abnormal, and is an important cause of fever.Blood culture means the incubation of blood in appropriate media to allow growth and identification of bacteria or other organisms that may be present in a patient’s bloodstream. Blood cultures are performed on febrile patients to identify and treat bloodborne organisms with the most appropriate antibiotic.

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Reading Gram Stained Direct Smears
Recording Bacterial Characteristics

The Gram stain reaction, shape, and arrangement of bacteria, and the presence or absence of intracellular organisms must be noted on the worksheet.Examples:Gram positive cocci in chains are present.Gram negative diplococci, intracellular, are present within white blood cells.Quantitate by approximating the average number of each cell type seen in 10 oil immersion fields, and record as:Many = More than 15/fieldModerate = 4-15/fieldFew = 1-3/fieldOccasional = 2-10/10 fieldsRare = 0-2/10 fields

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Significance of Specific Findings:

Epithelial cells in large numbers within sputum smears means that the specimen is predominantly oral saliva, rather than true sputum from the lung. Epithelial cells in urine smears indicate that the sample has been contaminated by organisms found on the vulva or distal urethra. Bacteria found near or on epithelial cells are usually normal contaminating bacterial flora.White blood cells indicate inflammation and possible infection. The direct smear examination should focus within and around these cells.Red blood cells in a direct smear are not usually significant.Yeast may be present as normal flora in upper respiratory tract or genital tract. They may be significant if they predominate, or if budding yeast forms are seen.Hyphae are more likely to indicate the presence of fungal infection, but this determination requires correlation with clinical findings.Bacteria found in spinal fluid, blood, tissue and specimens from other sterile sites are always significant.Body fluids which are normally sterile must be examined carefully. If only one organism per oil immersion field is identified, then there are about 105 organisms per mL present in the sample! Bacteria observed in specimens from the throat, genital tract and other areas containing normal flora suggest infection only if their composition and type varies significantly from the norm.

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Contaminated Gram Stain Solution

Contamination of the staining solutions rarely occurs, but should be suspected when smears repeatedly contain the same organisms, and these organisms do not grow or are inconsistent with the clinical picture. Yeast and gram negative rods can occur as stain contaminants.

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Special Considerations for Genital Smears

Gram negative cocci which occur in pairs with their adjacent sides flattened, giving them a coffee bean appearance, are typical of the genus Neisseria. Neisseria gonorrhea is commonly found within white blood cells; these organisms must be carefully sought within genital tract specimens, and their presence or absence should be specifically noted in the report.The presence of intracellular gram negative bacilli in a purulent male urethral smear is presumptive evidence of gonococci, but this assumption cannot be made in a female. Beware of other organisms which resemble gonococci but are found extracellularly, such as Acinetobacter lwoffi, which must be distinguished biochemically.

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Reading Gram Stained Smears From Cultures
Which of the following statements are TRUE for the Gram positive control smear?View Page
Cocci and Rods

Notice that Gram positive and Gram negative organisms can be either cocci (round) or bacilli (rod-shaped). A mixture Gram positive and Gram negative bacteria may be present in the same field.

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Variations in the Ends of Rods

The ends of rod-shaped organisms may be rounded or tapered.

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Gram Stain

The Gram stain provides a fundamental differentiation between types of bacteria. Gram positive bacteria retain the primary stain and are deep violet in color. Gram negative organisms are those that decolorize during the staining process and, after counterstaining, are pink in color. Bacteria have two basic shapes:cocci (round)bacilli (rod-shape)

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Information to be reported

The following information is reported:Gram stain reactionShapeThe cellular arrangement is not usually included in the report because it may vary, depending on the culture medium (liquid or solid) from which the organism was taken.

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Principle

The culture smear is used to determine the staining characteristic and shape of the unknown organism since this data helps the microbiologist to decide on additional culture and identification methods. By correlating the Gram stain reaction, colony morphology and growth requirements, the microbiologist may be able to tentatively identify the organism, which the physician may use to modify treatment, until definitive culture and antibiotic susceptibility results become available.

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Observations that can be of value to the microbiologist include:View Page
The process of microorganism identification includes: (Choose ALL of the correct answers)View Page

The Urine Microscopic: Microscopic Analysis of Urine Sediment
Bacteria

Bacteria may also be present, especially during a urinary tract infection. This view shows bacteria as solid gray rods or cocci. Since bacteria may also be a contaminant in specimens remaining at room temperature, or due to an unclean catch, caution must be observed in reporting bacteria. If 20 organisms per hpf are seen, the bacteria are considered to be clinically significant.

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Trichomonas under Phase-Contrast

Under phase contrast, Trichomonas organisms appear much darker than the surrounding white blood cells.

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Tuberculosis Awareness for Healthcare Workers
Tuberculosis infection

The natural history of TB infection is usually followed by an immune response and latency after exposure. In about 5-10% of cases, the latent period progresses to an active infection.The organism that causes TB infection is Mycobacterium tuberculosis. This organism is pictured in the photograph to the right as observed when stained with acridine orange stain. Infection occurs when a susceptible person inhales droplet nuclei containing Mycobacterium tuberculosis and the organism reaches the alveoli of the lungs.About 2-12 weeks after infection, the immune system limits multiplication of additional bacteria and the immunological test becomes positive.Latent tuberculosis infection (LTBI) is the stage when the viable organism remains in the body, and the patient has no symptoms and is non-infectious.Most infected persons do not experience clinical illness and are noninfectious. About 5-10% of persons infected with Mycobacterium tuberculosis who are not treated will develop TB during their lifetime. The risk for progression is highest during the first several years after infection.TB infects the lungs most often; however, it can infect almost any organ in the body, including bones and joints.

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How tuberculosis is spread

The Mycobacterium tuberculosis organism is spread through infectious droplet nuclei.When a person infected with pulmonary tuberculosis coughs, sneezes, shouts, or sings, the infectious particles are expelled into the air.The risk of infection is related to both concentration of infectious droplet nuclei and duration of exposure.

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