Welcome to the Microbiology Information

Here is some interesting news where a group of first year medical students from the American University of Antigua, College of Medicine decided to isolate and identify bacterium in ice-cream from various manufacturers. The group’s project was titled “Bacterial Contamination of Ice Cream from Vendors in Antigua”

Hmmm, although not exactly ground breaking they did conclude (as expected) that better food handling techniques needs to be practiced by those manufacturing and serving ice cream in Antigua & Barbuda.

The students in the groups were Brook Helmer, Victor Ashbey, Nalima Nandapala, Solomon Nchinda, Edwin Cohen Azarkian and Angela Echeverria, who did the verbal presentation in front of staff, students and invited guests.

They write: “At several points during its production, transportation, storage, and merchandising, it can be contaminated by biological organisms. These can be from ingredients added after pasteurization, air exposure, contaminated containers or unsanitary vendors,”

Samples of chocolate flavored ice cream without added ingredients were purchased from three local vendors over two consecutive weekends and analyzed. Two were purchased from roadside vendors and one locally manufactured brand from the supermarket.

All specimens tested positive for bacterial growth (Total plate Count) as well as food borne pathogens such as Listeria monocytongenes, Staphylococcus aureus, Candida albicans (clinical) and E. Coli were isolated. This indicates post process contamination of local ice cream due to improper handling and processing of the food. As a comparison they also tested two internationally recognized ice cream brands which were negative.

In summary the group believes better food handling education is needed to prevent food-borne diseases. This includes all people involved in every step of the ice cream preparation, handling, dispensing, manufacturing as well as vendors who sell the final products.

In addition, they suggested that all cooking utensils that come in contact with the ice cream be completely washed and sanitized, practice good hygiene and wash hands thoroughly when in contact with food, and to wear disposable gloves when serving customers. The most important is to refrigerate milk and ice cream products at acceptable refrigeration temperatures.

The group placed third in the competition for the best presented paper for research conducted between January and April 2007 at the university.

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New Zealand Dairy Giant, FONTERRA says a salmonella outbreak at its Cobden plant in Australia has been resolved without affecting any of its milk powder products.

The Cobden factory was closed for four days at the end of January after the pathogen was detected in an “environment sample” during routine monitoring. Both the manufacturer and the local Dairy Authority (Dairy Food Safety Victoria) has been working closely to rectify the problem.

Due to intensive testing, none of the company’s products were affected by the outbreak and milk destined for Cobden was likely to have been distributed to its Dennington plant.

Further information was not available last night. United Dairy Farmers of Victoria president Doug Chant said he had not been notified of any problem in Cobden.

“I’m certainly unaware of it,” Mr Chant said. “It probably doesn’t really have to be brought to our attention.”It’s an issue for the factory and I’m quite sure they’ll be dealing with it adequately.”

He said salmonella outbreaks were fairly uncommon in the dairy industry. “The practices of our factories are world class. We have very, very few problems as a rule and whatever the cause I imagine it was fairly isolated.” Mr Chant said the fact Fonterra had detected the pathogen in the environment rather than in the product demonstrated the company is being proactive in its approach to eliminate the source of the problem before it is escalated further.

On the December 21, 2006 in Albany NY, the New York State Agriculture Commissioner Patrick H. Brennan issued a warning to consumers in the Allegany County, New York area not to consume “unpasteurized” raw farm milk from the Gerald E. Snyder farm due to possible Listeria Monocytogenes contamination. Due to potential pathogenic concerns, pasteurization of raw milk is mandatory in 99% all milk sold.

The Snyder farm located at RD #1 1444 Randolph Rd., Alfred Station, New York 14803 holds a Department permit to legally sell raw milk at the farm. Although sample are taken monthly and tested by the Department to determine if the raw milk is free of pathogenic bacteria, it is still inadequate and the frequency should be increase to at least weekly testing.

A routine sample of the milk, taken by an inspector from the Division of Milk Control and Dairy Services on December 11, 2006, was subsequently tested by the Department’s Food Laboratory and discovered to be contaminated with Listeria monocytogenes.

On December 15, 2006, the producer was notified of a preliminary positive test result and volunteered to suspend raw milk sales until the sample results were confirmed.

Test results were confirmed on December 20, 2006 and the producer is prohibited from selling raw milk until subsequent sampling of the environment as well as packaged product indicates it is free of pathogens.

Listeria contaminated product could cause Listeriosis, a disease that usually causes mild flu-like symptoms in healthy individuals; however in weakened immuno-compromised individuals, meningitis and blood poisoning can occur. Pregnant women are also considered a high-risk group, as Listeriosis can also result in stillbirths.

It is important to note that raw milk does not provide the protection of pasteurization, which eliminates all pathogenic bacteria, including Listeria, salmonella, E.coli and so forth. Producers who sell raw milk to consumers must have a permit to do so from the Department, must sell directly to consumers on the farm where the milk is produced and must post a notice at the point of sale indicating that raw milk does not provide the protection of pasteurization. Farms with permits to sell raw milk are inspected by the Department monthly.

So far there has been no illnesses reported by the Department to be associated with product from the Snyder Farm.

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On the 07/12/2006, one of Australia’s Largest Dairy Manufacturer – National Foods has recalled several thousand litres of its Pura brand milk, citing fears that it could be contaminated with the E.coli bacteria.

The voluntary recall on Tuesday of 14 of its brands in New South Wales and Australian Capital Territory was announced after tests showed variable low levels of the bacteria.

“Retention samples indicated low but inconsistent levels so we sent them outside for further testing. When results came back they were still inconclusive but we decided to pull the whole lot just to be safe,” said spokesman Ian Greenshields.

E. coli can be fatal but typically causes abdominal pain, cramps and diarrhoea. A recent outbreak of E. coli from contaminated packaged spinach in the US led to 183 cases of illness and one death.

But when contamination is at low levels in a test sample, the bacteria may not occur in every batch of product, leading to inconsistent results and making it difficult to assess the risk. However food companies are increasingly cautious about microbiological contamination.

The Food Standards Australia New Zealand said this is the second most common reason for a product recall, after mislabelling.

“It is a growing trend and we commend them [food companies] for that,” said Lydia Buchtman, spokeswoman for the agency.

National Foods says the product contamination likely happened in the plant during manufacturing but the exact source is still being investigated. Pasteurisation is designed to kill this kind of bacteria.

It is not yet known how much the recall will cost the company but Greenshields said it involved ‘a whole day’s supply, a lot of product’ which could cost millions.

It included Pura whole milk, Pura Light Start and Woolworths and Homebrand whole milk which were manufactured on November 24 and have a best-used-before date of December 13.

Earlier this week Nestlé Australia also launched a voluntary recall of its Nan 2 HA Gold infant formula in 900g cans following the discovery of metal fragments in some cans. It is believed the contamination occurred during the production process.

This biofilm-producing terrorist is the bane of all industrial microbiologists. Industry can be humming along quite happily and then up pops Listeria and its panic stations. The micro response team rushes to the site armed with gauzes, swabs, sampling and HACCP (Hazard Analysis and Control of Critical Points) plans to do combat.

As we all know the genus Listeria is a gram positive rod, psychrotrophic, and displays a peculiar tumbling motility caused by a low number of peritrichous flagella which beat in a clockwise motion due to a defective CheY gene (Dons et al, 2004). This organism is ubiquitous and is found primarily in soil (Sutherland et al, 2003). The only species that is truly a human opportunistic infector is Listeria monocytogenes, public enemy number one. Its sibling Listeria ivanovii is attempting to cause confusion in the ranks of those over-worked industrial microbiologists. L. ivanovii has shown similar pathogenicity as seen by L. monocytogenes, in mice and other animals, but is rarely seen in humans (FDA/CFSAM, 2003). Are these two species protected or masked by Listeria innocula the harmless one? With the perceived threat of Listeriosis, the government bodies are debating the move towards zero tolerance for the genus. The federal government food body FSANZ standard only states that L. monocytogenes absence is required in ready-to-eat products and the FAO/WHO risk assessment concluded that levels of L. monocytogenes <100 cells per gram has the same risk as zero cells per gram (FAO/WHO, 2001). To complicate matters, Dussarget (2004) stated that of the 13 known serovars of L. monocytogenes, only 1/2a, 1/2b and 4b are responsible for 98% of reported human Listeriosis cases. The serovar 4b is associated with the majority of food borne outbreaks and sporadic cases. This single genus has been responsible for more product recalls and media hype than any other micro-organism. We all have heard of Conroy’s and the two deaths from ham in Adelaide in the last few months. Industries that produce ready-to-eat products all have great concern for this ubiquitous terrorist.

Industry has spent millions on the combat, control and the eradication of this organism. As with all terrorist organizations, the sleeper cells are very hard to find and the fact that Listeria produce a fatty acid biofilm on solid surfaces makes it very difficult to treat with standard chloride based surface sanitizers. This biofilm aids the survival of Listeria due to its lipid composition which is hydrophobic and thus prevents the entrance of water-based sanitizers; it also acts as a food reserve and selects for the survival of other symbiotic organisms that aid in the survival and proliferation of Listeria (Sutherland et al, 2003) (Somers & Wong, 2004). The destruction of one biofilm may lead to the establishment of others from that original source and to product contamination. Biofilms are living entities and thus, when critical mass is achieved, cells detach and contaminate the product. This is known to the industrial microbiologist as ‘spitting’. There is reported resistance developing in the standard chemicals used in the eradication of biofilms (Chavant, 2004). The only effective way to clean down contaminated areas is by high-pressure (area needs to be sealed) acid washes as well as physical scrubbing followed by contact sanitization (quats, chlorine, acid and peroxide sanitizer) – the chemical equivalent of hunting down terrorist cells with thermonuclear warheads. Listeria has also displayed an ability to survive and thrive in some of the most extreme environments found in industry such as saturated brine. Listeria has been associated with many of our most loved and highly consumed foods. These include: ice cream, soft cheeses, smoked salmon, pate, fermented meats, cooked further processed chicken meats and fresh leaf produce (Sutherland et al, 2003). This cowardly bacterium attack the elderly, infirmed and the defenseless fetus with relatively low infective doses, 2 to 3 log less than is required to infect healthy adults (CFSAN, 2003). To complicate matters further, this organism presents to the treating clinician as flu -like systems and initial diagnosis may be difficult.

The total number of victims recorded in Australia is 3 cases in 1,000,000 and is steadily decreasing as the industrial microbiologist is slowly eradicating all known niches. The consumers demand for ‘fresh’ products with minimal preservatives and additives results in additional pressures on the industrial microbiologist to discover strategies to meet the consumer demand without endangering the public. This has resulted in the steady development of non-thermal treatments such as microwave and radio frequency, ohmic and inductive heating, high pressure processing, pulsed electrical field and pulsed light, just to name a few that are in development or have been used in commercial food manufacturing (FDA/CFSAN, 2000). These intervention strategies amplify nature’s only controls in controlling these terrorists. For example, high pressure processing uses water pressures to burst the cell. There is a plethora of methods available for the industrial microbiologist to screen and identify this organism. The selection of methods is primarily based on quality and turnaround time. The longer a company’s product takes to reach the market the more it costs the company. Therefore, there is always pressure to find faster methods to screen out negatives. Some of the most common rapid methods are based either on ELISA type tests (BioMerieux VIDAS, TECRA Unique) or PCR (Oxoid’s BAX and Roche’s real-time PCR protocol). These methods are all automated and have the required regulatory approvals. The covert battle between the industrial microbiologist and Listeria is ongoing with no definite exit time. As long as the consumer enjoys the convenience of ready to eat food, Listeria will be waiting to strike; however, the industrial microbiologist will be there to contain, prevent and eliminate any danger to the public.

Now here is some interesting news about a new way to eliminate listeria in foods. It uses bacteriophage (viruses) to attack and destroy listeria monocytogenes cells in cheese.

Here’s what they say in the press release:

EBI Food Safety of the Netherlands announced that its bacteriophage P100 preparation, marketed as LISTEX(TM), has been approved as GRAS (Generally Recognized As Safe) by the US FDA, to control Listeria monocytogenes (LM) in cheese. This acknowledgement by the FDA is based on a thorough safety review, and is recognized by food companies and national governments worldwide. GRAS affirmation is an essential step in the commercialization of LISTEX(TM). LISTEX(TM) is the first bacteriophage product to receive GRAS recognition by the FDA. Listeria monocytogenes is generally viewed as the most dangerous food pathogen. It can cause Listeriosis, a fatal disease in roughly 30% of the cases, especially dangerous for newborns, the elderly and persons with weakened immune systems. Listeriosis is also a major concern to pregnant
women, causing spontaneous abortion. In the US, the costs of acute illness from food borne Listeria poisoning alone are estimated at $2.3 billion per year. Expenses for food processing companies to combat Listeria likewise run into the billions.

“In January of this year an independent expert panel of internationally recognized scientists unanimously concluded that LISTEX(TM) meets the GRAS safety requirements. Now that the FDA has given its formal approval, we will make our product available to the US market. The high end market, requesting ‘green’ and organic products, has been asking for LISTEX(TM), but we wanted an official endorsement by the FDA first.” says Mark Offerhaus, CEO of EBI Food Safety. “We are presently negotiating with prospective partners in North America and Europe to find the fastest way to market”. Prevention of food safety defects results in considerable gains of profitability and productivity. Offerhaus: “Food safety and quality systems are not only good corporate policy, they are simply good business. Appropriate use of LISTEX(TM) in food processing as an integral part of HACCP and GMP/GHP programs fits that concept perfectly”.

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Now here is an interesting question, can you eat moldy cheese? Well it depends on the type of cheese and the type of mould that’s on it. You see, soft cheeses such as camembert, Brie, Blue Vein and so forth are mould ripen cheese so it normal for the mould to be present.

On the other hand, cheeses such as cheddar, mozzarella, and parmesan are cheese that is not normal to have moulds. So the question remains, can you eat moldy cheese? Of course you can as long as the mould is limited to a small area and it is removed. You will need to be able to cut away at least a 1 cm chunk under and around the mould because it may have penetrated farther in than you can see.

Always throw any cheese that’s very very moldy. It’s safest to chuck them, as some moulds can produce toxins that can damage your liver, kidneys and immune system.

Bacillus licheniformis is a Gram-positive motile spore-forming rod, facultative anaerobic and belongs to the Bacillus subtilus group of Bacilli. It is an apathogenic soil organism that is mainly associated with plant and plant materials in nature but can be isolated from nearly everywhere in natures such soil, water, food manufacturing plant and so forth. Although its spores are highly heat resistant (100.C for 30 minutes), it is not as resistant as Bacillus stearothermophilus.

Although very very rare, Bacillus licheniformis has been associated in food poisoning in humans with foods such as cooked meat, poultry and vegetable dishes (particularly stews and curries which have been served with rice). Again this is a rare occurrence and not a major concern. Food poisoning by Bacillus licheniformis is characterized by diarrhea, although vomiting occurs in half of reported cases.

Bacillus licheniformis produce proteases and amylases which at high levels can cause the breakdown of short shelf-life foods with starch such as custards, rice puddings, sauces and so forth. Industrially the enzymes produced by Bacillus licheniformis have been extracted for use in household detergents. In the U.S. about 50% of liquid detergents, 25% of powder detergents, and almost all powdered bleach additives now contain enzymes to help break down stains that are otherwise hard to remove with conventional surfactants alone.

Bacillus licheniformis produce also produces penicillinase, pentosanases, bacitracin, proticin, 5′inosinic acid and inosine, citric acid, and substituted Ltryptophan.

Bacillus licheniformis is also a common dairy contaminant being present in raw milk. Monitoring of incoming raw milk for spores is an effective method of determining whether bacillus spores are present in the milk supply. The species has been isolated in pasteurized milk and cream where it can cause bitterness due to the protease enzymes breaking down the milk protein. It has also been reported as a contaminant in UHT milk as well. Although it is very unlikely to survive the UHT sterilization process, it may reside in the environment within the manufacturing plant and therefore Good Manufacturing Practice (GMP) will ensure its prevalence is the environment is reduced. Areas may include dirty valves, seals, heating plates, air vents and so forth.

Bacillus licheniformis also causes ropiness in bread and again monitoring the spore levels in flour may be an effective method of determining whether bacillus spores are present in flour used.

Bacillus licheniformis optimum growth temperature is 30.C; however it will not grow at low pH.

Bacillus No Synopsis Available

Yersinia enterocolitica is a gram -ve bacterium that belongs to a family of rod-shaped bacteria. Other species of bacteria in this family include Yersinia pseudotuberculosis, which causes an illness similar to Yersinia enterocolitica and Yersinia pestis, which causes plague.

Yersinia enterocolitica can cause illness in humans, however only a few strains are implicated. These strains are usually found in animals with the majority in pigs. Other strains are also found in many other animals with lower frequency and they include rodents, rabbits, sheep, cattle, horses, dogs, and cats. In pigs, the bacteria are most likely to be found on the tonsils.

Yersinia enterocolitica is commonly present in foods but with the exception of pork, most isolates do not cause disease. Similarly to Listeria this organism is psychrotrophic meaning it can grow at refrigeration temperatures. Although rare, contamination in pasteurized milk has been documented and I’m surprised that it has not been included as an organism of interest in dairy companies around the world. The organism is sensitive to heat (5%) and acidity (pH 4.6), and will normally be inactivated by environmental conditions that will kill coliforms.

The illness caused by Yersinia entercolitica is called Yersiniosis and is common in children. Symptoms are similar to salmonella infection and include fever, abdominal pain, and diarrhea, which is often bloody. The symptoms appear 3 to 7 days after ingestion of the implicated food or exposure and may last up to 3 – 4 weeks.

In older children and adults, abdominal pain may occur predominantly on the right hand side and may be confused with appendicitis. In rare occurrences and in small proportion of cases, complications such as skin rash, joint pains or bacteria infection of the bloodstream can occur (sepecemia).

Did you know that among the E. coli human pathogens, Verotoxin (Shiga-like toxin) forming strains (VTEC) have gained in importance in recent years. The group of enterohaemorrhagic E. coli (EHEC) with its highly pathogenic serovars 0157:H7, 026, 0103, 0111, 0145, and other strains are of particular concern.

Verotoxins can be classified into two main categories Verotoxin 1 (VT1, SLT1, Stx1) and Verotoxin 2 (VT2, SLT2, Stx2). EHEC strains may produce either VT1 or VT2 only or both VT1 and VT2 simultaneously. EHEC are capable of initiating life threatening illnesses, particularly in those with immune deficiency, young children and the elderly.

Detection of verotoxin is the easist way in which you can determine if the E.coli of interest is a pathogen of real concern.

E.coli is common everywhere with the main sources of infection being contaminated, raw or insufficiently heated foods of animal origin, e.g. meat and dairy products.

The reservoir for EHEC is the feces of cattle, sheep and goats. These microorganisms can enter food during the processing of meat and dairy products if hygienic conditions are inadequate. The drastic increase in the incidence of food infection caused by E. coli 0157 demands reliable and rapid methods of detection. In addition to traditional culture methods, immunological techniques are becoming more useful due to their improved specificity and sensitivity.

Duopath® Verotoxins is an immunological screening test based on the immune flow principle. The Duopath® Verotoxins GLISA test is an immunochromatographic rapid test intended to be used in food-analysing laboratories for the qualitative detection of Verotoxins (Shiga-like toxins) 1 and 2 from Verotoxinogenic E. coli (including E. coli O157:H7) isolated from food enrichments using FDA, USDA or other food enrichment methods.

This test has been validated and received AOAC approval for detection of Verotoxins 1 and 2 from isolated Verotoxin-producing E.coli (including E. coli O157:H7). Duopath® Verotoxin is also intended to be used in clinical laboratories for the qualitative identification of Verotoxins 1 and 2 (Shiga-like toxins 1 and 2) produced by E. coli isolated in cultures derived from clinical stool specimens. The identification aids in the diagnosis of diseases caused by enterohemorrhagic E. coli infections.