Welcome to the Microbiology Information

Bacillus stearothermophilus or Geobacillus stearothermophilus is one of the most common spoilage bacterium in commercially sterile heat processed foods. Although most bacterium cannot survive the high temperature, Bacillus stearothermophilus has a highly heat resistant spores that has enabled this bacterium to spoil canned foods, UHT milk, and other commercially sterile foods.

So what temperature is required to kill this bacterium? How long must it be held at this temperature?

A measure used to determine the effective kill rate is called the D or D’ Value. Basically, the D Value measures the time in minutes required at a given temperature for destruction of 90% of the cells.

Although it sounds simple, it’s not. It also depends on the nature of the food product, the pH, the salt level and so forth. For example, the lower the pH, the lower the temperature required. The higher the pH or close to a neutral pH of 7, the higher the temperature is required to kill this bacterium.

Below is a graph showing the thermal inactivation of Bacillus stearothermophilus spores (ATCC 12980).

For more detailed information you can download the pdf file here on the Thermal Inactivation and Injury of Bacillus Stearothermophilus Spores.

There is an interesting study by the National Food Centre in Dublin, Ireland where the objectives were to investigate the incidence or levels of bacterial contamination at key sites in domestic kitchens. In the study, the key sites were assessed for the potential of Staphylococcus aureus growth during chilled storage. In addition, domestic kitchen surfaces were also examined for a range of bacterium. They include total viable counts as well as indicators of cross contamination such as enterobacteriacae and coliforms. Specific pathogens such as salmonella, listeria, campylobacter, yersinia, staphylococcus aureus, E.coli 0157 were also tested.

What they found was the dish cloth used to clean up spillage’s in the kitchen had the highest levels of bacteria on a surface and were a major source of E.coli, listeria and staphylococcus. I’m sure this was expected.

As for the potential of Staphylococcus aureus growth during chilled storage, it writes:

“A domestic refrigerator even if capable of maintaining a safe working temperature is only effective as consumer adjustment dictates. To preserve food effectively and minimise/prevent the growth of many foodborne pathogens, the refrigerator must operate with a suitable temperature range and the food must be correctly positioned.”

Basically, my interpretation of the study concludes the need for more information regarding effective cleaning, prevention of cross contamination and the correct temperature to be maintained in the refrigerator to minimise bacterial growth.

Now here is some interesting news, a food recall in Australia due to oysters being contaminated with a virus rather than a bacterial pathogen. The recall is due to the norovirus in oyster imported into Australia from Asia.

Interestingly, the testing of food product for norovirus is not common and is technically very difficult. For a public recall to occur due to this virus, it must have come about due to many gastro cases and an intensive investigation. Could there be future lawsuits from this? Who knows?

A similar incident did occur in 2003 when frozen oysters from Japan were implicated. For more information click here

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The American Type Culture collection (ATCC), has today announced the addition of the Luxembourg-based microbiology firm Mecconti s.a.r.l. to the ATCC Licensed Derivative(R) program. This initiative is aimed at improving the quality of microbiology products and protecting consumers impacted by them.

The license agreement between ATCC and Mecconti represents a major expansion of ATCC’s Licensed Derivative (LD) program for European quality control professionals and consumers.

The LD program assures QC microbiologists that commercial products bearing the LD emblem contain microorganisms with confirmed identity, viability and purity.

For-profit companies who claim to incorporate ATCC biomaterials into their own commercial products but are not part of the LD program do not comply with ATCC’s quality controls and often violate ATCC’s material transfer agreement. Any claims made by the companies about the equivalence of the microorganisms in their products directly to ATCC strains are unsubstantiated because ATCC does not test them.

ATCC VP for Licensing, Contracts and Compliance Dr. Jesus Soriano said “Quality control professionals need to know with certainty that the materials at the foundation of their testing are viable, pure and correctly identified. By purchasing materials that carry the Licensed Derivative emblem, customers can trust that the characteristics of the ATCC-derived microorganisms have been maintained and confirmed until they reach the end users.”

“As a public science organization, ATCC takes very seriously our responsibility to try to ensure the safety and quality of the materials we provide,” Soriano added.

“In joining ATCC’s effort and passing their rigorous evaluation of our quality control process, our customers can be assured that our family of microorganisms is derived directly from ATCC cultures and is controlled to maintain its identity, purity and viability in products used in the industrial, clinical or environmental setting,” Mecconti President Dr. Gerhard Huecker said.

ATCC is the world’s largest biological resource center and the most comprehensive source of standard reference cultures and reagents used by life science researchers in academic, government and industrial laboratories.

Mecconti develops freeze-dried microorganism products and dehydrated culture media for use in quality control testing of pharmaceutical, biotech and food/beverage products manufactured around the world.

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Norovirus
When the word “food pathogens” is mentioned, most will people will associate it with salmonella, E.coli or listeria. Although they are true pathogens, the symptoms they produce are initially similar to a common gastro virus called the norovirus. Viruses are very different from bacteria and parasites. They are not affected by treatment with antibiotics, and they cannot grow outside of a person’s body.

You see, the norovirus is a very common virus that causes nausea, vomiting, diarrhea, and some stomach cramping. Sometimes people also have a low-grade fever, chills, headache, muscle aches, and a general sense of tiredness. The illness often begins suddenly, and the infected person may feel very sick. The illness is usually brief, with symptoms lasting only about 1 or 2 days. In general, children experience more vomiting than do adults. Most people with norovirus illness experience both diarrhea and vomiting.

The main concern is that sometimes people become dehydrated due to vomiting and diarrhea and may need special medical attention. Dehydration problems are usually only seen among the very young, the elderly, and persons with weakened immune systems.

Infection with noroviruses
Noroviruses are found in the stool or vomit of infected people. People can become infected with the virus in several ways, including:

• Eating food or drinking liquids that are contaminated with norovirus;
• Touching surfaces or objects contaminated with norovirus, and then placing their hand in their mouth;
• Having direct contact with another person who is infected and showing symptoms

Persons working in day-care centers or nursing homes should pay special attention to children or residents who have norovirus illness. This virus is very contagious and can spread rapidly throughout such environments. Particular care should be taken with young children in diapers who may have diarrhea or who have vomited as both stool and vomit can carry the virus.

People infected with norovirus are contagious from the moment they begin feeling ill to at least 3 days after recovery. Some people may be contagious for as long as 2 weeks after recovery. Therefore, it is very important to use good hand washing and other hygienic practices.

Treatment for people with norovirus infection?
Currently, there is no antiviral medication that works against norovirus and there is no vaccine to prevent infection. Norovirus infection cannot be treated with antibiotics because antibiotics work to fight bacteria and not viruses.

Pseudomonas aeruginosa is a gram -ve rod shaped bacterium that is naturally found in many types of drinking water. According to European water regulations, it is a requirement to have Pseudomonas aeruginosa absent in a 250 ml sample of bottled water. Unfortunately no such regulation exists in the United States and other developed countries. Apparently, the Pseudomonas aeruginosa regulation in Europe originated as a quality control issue and not as a health effects issue.

Interestingly during the last 10 years, there have been an increase in the number of papers appearing indicating that Pseudomonas aeruginosa from drinking water is a health threat. This can only happen if the levels are high.

Being psychrotrophic, a food microbiologist will think it’s more a food spoilage issue than a health threat. The clinical microbiologist will think it is an opportunistic bacterium and can lead to a health threat. So where does this bacterium come from?

Pseudomonas aeruginosa is a ubiquitous environmental bacterium. It can be recovered, often in high numbers, in common food, especially vegetables. Moreover, it can be recovered in low numbers in drinking water. A small percentage of clones of Pseudomonas aeruginosa possess the required number of virulence factors to cause infection. As an opportunistic bacterium, Pseudomonas aeruginosa will not proliferate on normal tissue but requires previously damaged organs.

By further narrowing down the risk to human health, only certain specific hosts are at risk. They include patients with profound neutropenia, cystic fibrosis, severe burns, and those subject to foreign device installation. Other than these very well defined groups, the general population is normally immune to infection with Pseudomonas aeruginosa.

Although it is ubiquitous nature, there are ways to eliminate Pseudomonas aeruginosa from our food and drinking water. They include cooking foods properly, filtering or boiling drinking water.

If you are interesting in finding out the levels of Pseudomonmas aeruginosa in your water supply for food, I suggest you contact a reputable water microbiology laboratory.

Severe Infections Caused by Pseudomonas Aeruginosa. Perspectives on Critical Care Infectious Diseases, Band 7 Severe Infections Caused by Pseudomonas aeruginosa emphasizes controversies worldwide in the diagnosis, treatment, prevention and pathogenesis of pseudomonas aeruginosa infections. By including both chapters written by European authors and chapters written by North American experts, the reader is ensured of receiving a broad spectrum of opinions on controversial topics. Special attention is paid to such topics as the diagnosis of hospital-acquired pneumonia caused by p. aeruginosa, scheduled antibiotic therapy for patients with cystic fibrosis, empiric therapy for febrile neurotropenic patients, combination vs. single agent antibiotic therapy for severely ill patients, and alternatives to conventional antibiotic therapies. This excellent overview of our current understanding of pseudomonas aeruginosa pathogenesis will prove useful to clinicians and microbiologists around the globe. TOC:Contributors.- Preface.- Series Preface.- 1. Pseudomonas aeruginosa Infections in Specific Types of Patients and Clinical Set, Medical / Nursing ; infectious & contagious diseases ; medical microbiology & virology ; Infectious Diseases ; Microbiology, Severe Infections Caused by Pseudomonas Aeruginosa. Perspectives on Critical Care Infectious Diseases, Band 7

Did you know that truffles are a hypogeous fungi or mushroom which live underground in symbiosis with the plant host roots so that they can accomplish their life cycle. The plant host roots provides the sugars and vitamins need for growth. Some species, such as Tuber magnatum Pico, the ‘white truffle’, and Tuber melanosporum Vittad., the ‘black truffle’, are highly prized in many countries because of their special unique taste and smell. This is due to the spores which when ripe emits a very intense aroma indicating it is ready for picking.

Due to the huge demand and short supply of the black and white truffles, there has been increased attention towards other species of local interest for the rural economy such as Tuber aestivum. As such, new scientific projects have been initiated started to gain a better understanding of the ecology of truffles. This will involve gaining a better understanding of the truffle and exploiting new approaches of environmental microbiology and molecular ecology so that truffles may one day be farmed to yield higher productivity leading to greater supply. In some of these projects specific primers have been developed to identify many morphologically similar species, the distribution of Tuber magnatum has been followed in a selected truffle-ground, the phylogeography of Tuber melanosporum and Tuber magnatum has been traced, and the microorganisms associated with the truffles and their habitats have been identified.

Source: Mello A et al …
FEMS Microbiol Lett. 2006 Jul;260(1):1-8.
Istituto per la Protezione delle Piante del CNR, Sezione di Torino,
Torino, Italy.