Thistle QA is a SANAS accredited organisation, No: PTS0001 P.O. Box 131375, Bryanston, 2074 Ground Floor, Block 5 Bryanston Gate, 170 Curzon Road Bryanston, Johannesburg, South Africa 804 Flatrock, Buiten Street, Cape Town, 8001 www.thistle.co.za Tel: +27 (011) 463 3260 Fax: +27 (011) 463 3036 Fax to Email: + 27 (0) 865384484 email : [email protected]Please read this section first The HPCSA and the Med Tech Society have confirmed that this clinical case study, plus your routine review of your EQA reports from Thistle QA, should be documented as a “Journal Club” activity. This means that you must record those attending for CEU purposes. Thistle will not issue a certificate to cover these activities, nor send out “correct” answers to the CEU questions at the end of this case study. The Thistle QA CEU No is: MT-11/00142. Each attendee should claim THREE CEU points for completing this Quality Control Journal Club exercise, and retain a copy of the relevant Thistle QA Participation Certificate as proof of registration on a Thistle QA EQA. MICROBIOLOGY LEGEND CYCLE 30 ORGANISM 6 SALMONELLA Salmonella (S.) is the genus name for a large number (over 2,500) of types of bacteria. Each type is distinctly identifiable by its specific protein coating. The types are otherwise closely related. Salmonella bacteria are rod-shaped, flagellated, Gram negative, and are known to cause disease in humans, animals, and birds (especially poultry) worldwide. The two major diseases caused by Salmonella spp. are gastroenteritis and typhoid fever (typhoid and paratyphoid fevers) in humans. The terminology that identifies the particular protein coats, or serovars, is not well settled, and what previously were thought to be various species of the genus Salmonella are now thought to be serovars of only two species, S. enterica and S. bongori, by many researchers. However, these designations are not always accepted in the scientific literature and so common serovars that have been named in the past are still used (for example, S. typhi, S. typhimurium, S. paratyphi, S. enteritidis, S. cholerasuis, S. saintpaul). Minor variations in some serovars are termed subspecies and assigned a number. The serovars are identified by the Kauffman-White classification that uses two major types of antigens (somatic O, along with envelope antigens that may mask O antigens, and flagellar or H antigens) to distinguish the over 2,500 types of Salmonella bacteria. Sometimes laboratories or other reporting agencies identify isolates simply as Salmonella spp. (species) and do not identify the serovars. Microbiology Like other members of the bacterial family Enterobacteriaceae, species of Salmonella are gram-negative and rod-shaped. Salmonella do not require oxygen and their main habitat is the intestinal tract of animals. Salmonella species are motile and produce hydrogen sulfide. They generally do not ferment lactose. In a clinical laboratory, Salmonella is usually isolated on MacConkey agar, XLD agar, XLT agar, or DCA agar. Because they cause intestinal infections and are greatly outnumbered by the bacteria normally found in the healthy bowel, primary isolation requires the use of a selective medium, so use of a relatively non-selective
Transcript
Thistle QA is a SANAS accredited organisation, No: PTS0001 Accredited to ISO guide 43 and ILAC G13 Certificate available on request or at www.sanas.co.za
Please read this section first The HPCSA and the Med Tech Society have confirmed that this clinical case study, plus your routine review of your EQA reports from Thistle QA, should be documented as a “Journal Club” activity. This means that you must record those attending for CEU purposes. Thistle will not issue a certificate to cover these activities, nor send out “correct” answers to the CEU questions at the end of this case study. The Thistle QA CEU No is: MT-11/00142. Each attendee should claim THREE CEU points for completing this Quality Control Journal Club exercise, and retain a copy of the relevant Thistle QA Participation Certificate as proof of registration on a Thistle QA EQA.
MICROBIOLOGY LEGEND
CYCLE 30 ORGANISM 6
SALMONELLA
Salmonella (S.) is the genus name for a large number (over 2,500) of types of bacteria. Each type is distinctly identifiable by its specific protein coating. The types are otherwise closely related. Salmonella bacteria are rod-shaped, flagellated, Gram negative, and are known to cause disease in humans, animals, and birds (especially poultry) worldwide. The two major diseases caused by Salmonella spp. are gastroenteritis and typhoid fever (typhoid and paratyphoid fevers) in humans.
The terminology that identifies the particular protein coats, or serovars, is not well settled, and what previously were thought to be various species of the genus Salmonella are now thought to be serovars of only two species, S. enterica and S. bongori, by many researchers. However, these designations are not always accepted in the scientific literature and so common serovars that have been named in the past are still used (for example, S. typhi, S. typhimurium, S. paratyphi, S. enteritidis, S. cholerasuis, S. saintpaul).
Minor variations in some serovars are termed subspecies and assigned a number. The serovars are identified by the Kauffman-White classification that uses two major types of antigens (somatic O, along with envelope antigens that may mask O antigens, and flagellar or H antigens) to distinguish the over 2,500 types of Salmonella bacteria. Sometimes laboratories or other reporting agencies identify isolates simply as Salmonella spp. (species) and do not identify the serovars.
Microbiology
Like other members of the bacterial family Enterobacteriaceae, species of Salmonella are gram-negative and rod-shaped. Salmonella do not require oxygen and their main habitat is the intestinal tract of animals. Salmonella species are motile and produce hydrogen sulfide. They generally do not ferment lactose.
In a clinical laboratory, Salmonella is usually isolated on MacConkey agar, XLD agar, XLT agar, or DCA agar. Because they cause intestinal infections and are greatly outnumbered by the bacteria normally found in the healthy bowel, primary isolation requires the use of a selective medium, so use of a relatively non-selective
Thistle QA is a SANAS accredited organisation, No: PTS0001 Accredited to ISO guide 43 and ILAC G13 Certificate available on request or at www.sanas.co.za
medium such as CLED agar is not often practiced. Numbers of salmonella may be so low in clinical samples that stools are routinely also subjected to "enrichment culture" where a small volume of stool is incubated in a selective broth medium, such as selenite broth or Rappaport Vassiliadis soya peptone broth overnight.
These media are inhibitory to the growth of the microbes normally found in the healthy human bowel, while allowing salmonellae to become enriched in numbers. Salmonellae may then be recovered by inoculating the enrichment broth on one or more of the primary selective media. On blood agar, they form moist colonies about 2 to 3 millimeters in diameter. Serological techniques play a key role in classifying Salmonella. Suspect colonies further analyzed by triple sugar iron agar/ or lysine-iron agar and confirmed by antigenic analysis of O (somatic) and H (flagellar) antigens.
Salmonella growing on XLD agar Gram Stain of Salmonella enteritidis
Salmonella-associated diseases
Disease-causing Salmonella species have recently been re-classified into a single species, Salmonella enterica, which has numerous serovars. Salmonella Typhi causes typhoid fever. Other Salmonellae are frequent causes of food borne illness, especially from poultry and raw eggs and more generally from food that has been cooked or frozen, and not eaten straight away. Refrigeration does not kill the bacteria, although it can stop their reproduction.
While these infections would normally only require a treatment of antibiotics, the overuse of antibiotics in both the poultry and beef industries have created a strain of Salmonella that is potentially resistant to antibiotics. Salmonellosis can also be caught by handling reptiles, such as iguanas or terrapins. A CDC study also noted cases of Salmonellosis in 2003 and 2004 associated with handling commercially distributed pet rodents (CDC 2005).
The prevention of Salmonellosis as a food illness involves effective sanitizing of food contact surfaces. Alcohol has proven to be an effective topical sanitizer against Salmonella. Quaternary ammonium can be used in conjunction with alcohol as a food contact safe sanitizer with increased duration of the sanitizing action. Nonflammable Alcohol Vapor in carbon dioxide NAV-CO2 systems or sodium hypochlorite are frequently used to sanitize surfaces to prevent Salmonella
Thistle QA is a SANAS accredited organisation, No: PTS0001 Accredited to ISO guide 43 and ILAC G13 Certificate available on request or at www.sanas.co.za
Treatment 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. References http://www.newworldencyclopedia.org/entry/Salmonella Questions
1. Discuss the treatment of salmonella 2. Discuss the role of Salmonella in disease. 3. Discuss the lab diagnosis of Salmonella.
