Patient 4: Ng Ming En
Diagnosis: Food Poisoning
Complaints: Severe vomiting, diarrhea, abdominal cramps

Findings:
Foodborne illness (food poisoning) results from eating food contaminated with bacteria (or their toxins) or other pathogens such as parasites or viruses.
After they are swallowed, there is a delay, called the incubation period, before the symptoms of illness begin. This delay may range from hours to days, depending on the organism, and on how many of them were swallowed. During the incubation period, the microbes pass through the stomach into the intestine, attach to the cells lining the intestinal walls, and begin to multiply there. Some types of microbes stay in the intestine, some produce a toxin that is absorbed into the bloodstream, and some can directly invade the deeper body tissues. The symptoms produced depend greatly on the type of microbe. Numerous organisms cause similar symptoms, especially diarrhea, abdominal cramps, and nausea.

Culture

To find out what is the organism, the specimen (stools) is send for culturing using agar plates.
Inoculated places are O2 incubated unless otherwise indicated.

All faeces are inoculated onto the following media: BAP, MAC, SS, Selenite broth and Campylobacter selective agar for the isolation of salmonella, Shigella and Campylobacter spp.

In addition to the above:
· Bloody faeces are also inoculated onto Sorbitol MAC plate.
· Watery faeces are plated on TCBS and inoculated onto APW to culture for Vibrio spp.

Common Bacteria found in Bacterial gastroenteritis

Then gram staining is performed to determine whether organism is gram positive or negative. Following that, the organism shape (cocci or bacilli) is also determined and biochemical test is determined.the biochemical testsare used to detect the presence of enzymes (eg. Catalase, oxidase etc) and metabolic end-products (eg. Methyl red, etc). Lastly, an antibiotic sensitivity test is performed.

The above steps are performed to determine the organism and the organism I suspected is:Bacillus cereus
Some info about Bacillus Cereus
Bacillus Cereus food poisoning is a gastrointestinal intoxication caused by toxins produced by the Bacillus Cereus bacteria. It is a gram-positive spore-forming organism found in soil and dust. It is frequently found in rice dishes, occasionally pasta, meat or vegetable dishes, dairy products, soups, sauces and sweet pastry products where these have not been cooled quickly and effectively after cooking and during storage. It causes two different forms of food poisoning: an emetic illness and a diarrhoeal illness. The emetic illness ismediated by a highly stable toxin that survives high temperatures and exposure to trypsin, pepsin and pH extremes. The diarrhoeal illness is mediated by a heat- and acid-labile enterotoxin.

B. cereus-associated foodborne illness occurs as 2 distinct syndromes: emetic and diarrhoeal.
Incubation: Emetic; 1-6 hours after eating contaminated food.
Diarrhoeal; 10-12 hours.
Symptoms: The symptoms of the emetic syndrome result from ingestion of pre-formed toxin: nausea and vomiting, occasionally followed by diarrhoea. Diarrhoeal symptoms results from ingestion of vegetative organisms or spores and their subsequent multiplication and toxin production within the intestinal tract: abdominal pain, watery diarrhoea and occasional nausea

a picture of bacillus cereus

Adapted from: http://textbookofbacteriology.net/B.cereus.html

Another organism that i suspect in this patient is: Vibrio cholerae

References
http://www.foodlink.org.uk/factfile_c.asp?file=1&chapter=9
http://www.cdc.gov/ncidod/dbmd/diseaseinfo/foodborneinfections_g.htm
http://www.nzfsa.govt.nz/science/data-sheets/bacillus-cereus.pdf

posted by Huiling

ENTEROCOLITIS

Patient 2: Kwan Siew Lan
Age: 28
Complaints: Diarrhea
Diagnosis: Enterocolitis
Antibiotic treatment (if any): Nil
Specimen: Stool


Enterocolitis

Enterocolitis is the inflammation of the large and small intestines. Enteritis specifically refers to an inflammation of the small intestine and colitis specifically refers to inflammation of the large intestine.


Investigations

Cultures
Cultures are to be done on Macconkey, Salmonella Shigella and Campylobacter agar plates. An additional test will be the Selenite Broth (enrichment medium for Salmonella and Shigella).

MacConkey agar is a medium recommended for use in the isolation and differentiation of lactose-fermenting organisms from non-fermenting Gram-negative enteric bacteria.

Salmonella Shigella and Campylobacter agars are selective mediums that only permit the growth of Salmonella, Shigella and microaerophillic Campylobacter species respectively.

Microscopy
1) Gram Stain - To be done when culture is ready. It is to determine the type of bacteria (Gram-positive or gram-negative) that has grown and decide on the number of biochemical tests to do and also the type of antibiotic sensitivity tests to do.
2) Ova and Cysts – To look for ova and cysts in the specimen that could be a possible cause of diarrhea.

Biochemical Tests
From the microscopy results, decide on the type of tests to do. If the gram stain shows gram negative bacilli, do an oxidase test. For oxidase-negative gram-negative bacilli, proceed to 5 tubes test (KG, SC, Urea, MOT, IND) if it is a lactose fermenter and 7 tubes test (KG, SC, Urea, MOT, IND, PPA, MAL) if it is a non-lactose fermenter.


Possible microorgainisms

Salmonella typhi – Gram-negative bacilli
Vibrio parahaemolyticus
Campylobacter species
Giardia lamblia


Posted by Melva Lim

URINARY TRACT INFECTION

Patient 3
Name: Maisy Wong
Sex: Female
Age: 66 yrs
Complaints: Fever, chills, bladder distension, on indwelling catheter
Diagnosis: Urinary tract infection
Antibiotic treatment: Nil

DEFINITION
A urinary tract infection, or UTI, is an infection that can happen anywhere along the urinary tract -- the kidneys, the ureters (the tubes that take urine from each kidney to the bladder), the bladder, or the urethra (the tube that empties urine from the bladder to the outside).

CAUSES, INCIDENCE AND RISK FACTORS
Cystitis, a common condition, is usually caused by a bacterium from the anus entering the urethra and then the bladder. This leads to inflammation and infection in the lower urinary tract.
Certain people are more likely to get UTIs. Women tend to get them more often because their urethra is shorter and closer to the anus. Elderly people (especially those in nursing homes) and people with diabetes also get more UTIs.

BACTERIAL CULTURE
The most common cause of urinary tract infection is E coli. In hospital practice, other bacterial species commonly seen include enterobacter, klebsiella, proteus, pseudomonas, enterococci, and staphylococci. Staphylococcus saprophyticus is a common cause of infection in young sexually active women. The laboratory must also quantify culture results to determine the clinical relevance of an isolate.

CULTURE METHODS
Before culturing the urine should be mixed by inverting the container.
Choice of media:The media chosen must be able to support the growth of urinary pathogens and possible contaminants, inhibit Proteus spp from swarming, and distinguish lactose and non-lactose fermenters. Cysteine lactose electrolyte deficient medium (CLED) fulfils these criteria. Culture plates should be incubated overnight at 35–37°C in air. More recently, a new chromogenic agar has been described for the detection of urinary tract pathogens that may provide better differentiation of bacteria than conventional media. Anaerobes rarely cause UTI but culture should be considered in a selected group of patients, such as those with persistent pyuria or foul urine and symptoms of UTI. In immunosuppressed patients (including those on intensive care or neonatal units), culture for Candida spp should be performed because the urine may be positive before, or may indicate, the development of fungaemia. Screening for methicillin resistant Staphylococcus aureus should include urine samples from catheterised patients. An appropriate selective medium, such as mannitol salt agar with oxacillin (2 mg/litre), should be used.

Media and culture conditions to aid the isolation of more fastidious organisms such as lactobacilli, corynebacteria, Gardnerella vaginalis, Mycoplasma spp, and Haemophilus spp may be worth pursuing for symptomatic patients with pyuria and negative routine culture. The use of multipoint inoculation to perform routine anaerobic culture has been suggested by some authors as being clinically valuable.A microtitre method may be used in the identification of enterobacteriaceae, and this technique may also be applied to sensitivity testing using an automated reader.

IDENTIFICATION OF BACTERIA
Clear protocols for the identification of bacteria and fungi should be in place. In general, it is adequate to report coliforms as such without full identification. Proteus spp are urease positive and resistant to nitrofurantoin. Pseudomonas aeruginosa is an oxidase positive lactose non-fermenter, resistant to most first line antibiotics. If clinical details suggest that a non-lactose fermenting coliform may be a Salmonella spp and the urease and oxidase tests are negative then slide agglutinations with "O" and "H" antisera should be performed from cultures on blood (or other non-selective) agar plates. Any positive results should be followed up with biochemical confirmation. If typhoid fever is suspected, 5–10 ml of uncentrifuged urine should be inoculated into double strength selenite, incubated overnight at 37°C in air, then subcultured on to deoxycholate citrate agar, which in turn is incubated overnight at 37°C in air. Any suspect isolate should be dealt with in containment level 3 accommodation.
One advantage of using blood agar alongside CLED is that Gram positive bacteria are more easily characterised. If uncertainty exists, a catalase test will distinguish streptococci (negative) from staphylococci (positive). Staphylococcus aureus is DNase, slide, and tube coagulase positive. Staphylococcus saprophyticus can be identified by its resistance to novobiocin and this makes a useful distinction from other coagulase negative staphylococci, which are usually only important in specific situations such as instrumented or catheterised patients. If the appearance of the colony is typical of Enterococcus faecalis report the organism as such; if uncertain, perform a bile aesculin test. ß-Haemolytic streptococci can be readily identified by Lancefield group testing.
Other isolates are identified using standard laboratory techniques, all multiply antibiotic resistant organisms need to be fully identified.
Fungi need only be identified if there is evidence to suggest that the isolate is clinically relevant. Because cut off values vary from author to author, we recommend that repeat sampling is performed to determine that there is persistent funguria (catheters should be changed). Candida albicans is germ tube positive and usually sensitive to fluconazole, itraconazole, and amphotericin. Sensitivity testing and the identification of other candida and fungal species are only necessary in selected patients, such as those who are severely immunocompromised.
The detection of antimicrobial substances is not routinely recommended but should be incorporated in the multipoint set to exclude false negative culture results. The detection of antibody coated bacteria in urine is not recommended in the routine diagnostic laboratory but may be useful to distinguish between upper and lower urinary tract infection in selected patients.

SENSITIVITY TESTING
The choice of agents to test will depend upon local antibiotic policies and resistance patterns. In general, the primary agents tested target coliforms and enterococci, and second line sensitivities need only to be performed if less common bacteria or resistant isolates are encountered. The suggested first line agents include amoxicillin, trimethoprim, cefalexin (or other oral cephalosporins), nitrofurantoin, co-amoxiclav, and ciprofloxacin. Urine is used as the primary inoculum when there is evidence of infection (pyuria and/or bacteriuria) so as to permit rapid reporting. This method may be more representative than picking individual colonies for subculture, particularly given the heterogenous nature of urinary tract infection.The degree of pyuria that triggers the performance of direct sensitivity testing should be decided locally depending on the patient group examined. It is suggested that all urines that show bacteria on microscopy and those with pyuria > 100 white cells/mm3 should be tested. Recent recommendations for disc content and zone size interpretation have been published by the British Society for Antimicrobial Chemotherapy.
Each sensitivity report is tailored to guide clinicians to the most appropriate agents and it is often necessary to suppress antibiotics if the isolate is not deemed to be clinically relevant. Suppressing antibiotic sensitivities on the results of positive specimens may be a particularly useful way of educating users that treatment of a positive catheter urine is not normally warranted. In addition, the presence or absence of pyuria may be used to decide which sensitivities are reported. However because the definition of UTI is based on bacterial counts and not on the presence or absence of pyuria, performing sensitivities should be related to the number of bacteria present and the relevant clinical situation. Specific agents may be unsuitable in particular situations—for example, the reporting of intravenous antibiotics to general practitioners—and certain antibiotics are relatively contraindicated in pregnancy. If sensitivity testing is not performed (for example, on mixed cultures) then culture plates should be kept for five days so that further testing may be performed if necessary.

References:
http://jcp.bmj.com/cgi/content/full/54/12/SEC3
http://www.nlm.nih.gov/medlineplus/ency/article/000521.htm

Posted by Xiu hui