Welcome to the Microbiology Information

Did you know that approximately four million cases of food borne infectious disease occur annually in Australia; new food borne pathogens, such as enterohaemorrhagic Escherichia coli, are emerging. Climate change, combined with changes in how we produce and distribute food and how we behave as consumers, have the potential to affect food borne disease in the coming century. Food borne disease outbreaks are now more far-reaching (and sometimes global) due to modern mass food production and widespread food distribution. There are strong seasonal patterns for Salmonella and Campylobacter infection in Australia. Global warming may increase the incidence of infections, such as salmonellosis, and diseases caused by toxins, such as ciguatera.

Let’s hope all the world leaders take climate change seriously.

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.

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

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

There were five fatal cases of listerosis cases in Sydney Australia between 1998 occurring in one particular area North of Sydney. The area is the Hunter which is about 2 hours drive North of Sydney.

Four of the cases had either resided in a nursing home or had periods in hospital with all patient being elderly or immuno compromised.

During an investigative study, Listeria monocytogenes was found in fresh fruit salad at a catering facility in two different batches (opened and unopened) as well as in fruit salad in the processing plant. Environmental swabs were taken in and around the surrounding area and there were some positive results. They included the drains and the food processing trolleys indicating the present of listeria within the environment as well as insufficient or poor hygiene practices to control the pathogen. The strains were then serotype and they matched those from the fruit salad implicated.

Due to the low pH, fruit salad is not a common medium for the growth of listeria and has not been implicated in any outbreak in the past. However unlike other industry such as Dairy where pasteurization is applied to remove pathogen, the processing of fruit salad relies on Good manufacturing Practices (GMP) and hygiene to ensure it’s absent. Poor GMP was evident at both the processing plant and poor hygiene at the catering facility. Rock melon was one of the main ingredients used in the preparation of the fruit salad and it is suspected the source was from dirty rock melons. Rocks melons also have higher pH than other fruits adding to the evidence.

Along with the 5 days shelf-life, any presence of listeria will grow if conditions are favorable. This may occur if the ratio of rock melon is higher as well as poor storage of the fruit salad. Now when you feed this to a high risk group to the equation, you’re asking for trouble.

One question remains unanswered and this was considering the wide geographical area where the fruit salad was delivered why was there not more cases implicated?

Anyhow the investigation received wide publicity and interest from the State Coroner. Interventions following the outbreak have been successful in controlling further cases in the Hunter. They include training and education program and increased regulatory monitoring programs of high risk plants.

Bacillus cereus is a gram positive rod that produces spores and has been recognized as an agent of food poisoning since 1955. There were 52 food poisoning outbreaks between 1972 and 1986 associated with Bacillus cereus were reported, however this is thought to only represent 2% of the total cases which have occurred during that time.

Bacillus cereus causes two types of food poisoning compared to bacterial infections. The first is characterized by nausea and vomiting and abdominal cramps and has an incubation period of 1 to 6 hours. This closely resembles Staphylococcus aureus enterotoxin food poisoning in its symptoms and incubation period and is called emetic toxin and or the “short-incubation”. This is caused by a preformed heat-stable enterotoxin of molecular weight less than 5,000 daltons. The mechanism and site of action of this toxin are unknown. The long-incubation form of illness is mediated by a heat-labile enterotoxin (molecular weight of approximately 50,000 daltons) which activates intestinal adenylate cyclase and causes intestinal fluid secretion.

The short-incubation form is most often associated with fried rice or starchy foods that has been cooked and then held at warm temperatures for several hours. The disease is often associated with Chinese restaurants. In one reported outbreak, macaroni and cheese made from powdered milk turned out to be the source of the bacterium.

The second type of food poisoning results primarily in abdominal cramps and diarrhea with an incubation period of 8 to 16 hours. Diarrhea may be a small volume or profuse and watery. This type is referred to as the “long-incubation” or diarrheal form of the disease, and it resembles more food poisoning caused by Clostridium perfringens. This type of food poisoning is frequently associated with meat or vegetable-containing foods after cooking. The bacterium has been isolated from 50% of dried beans and cereals and from 25% of dried foods such as spices, seasoning mixes and potatoes. One outbreak of the long-incubation form was traced to a “meals-on-wheels” program in which food was held above room temperature for a prolonged period.

The short-incubation or emetic form of the disease is diagnosed by the isolation of Bacillus cereus from the incriminated food. The long-incubation or diarrheal form is diagnosed by isolation of the organism from stool and food as well as the toxin using ELISA based kits such as TECRA.

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).

An unsatisfactory level of Bacillus cereus in cooked foods generally occurs as a result of inadequate temperature control.

As for Clostridium perfringens, cooked foods should be held at or above 60ºC or at or below 5ºC to prevent growth, or held outside this temperature range for a limited time. Foods associated with Bacillus cereus food poisoning include cooked rice dishes, other cereal based foods such as pasta/noodles, dairy based deserts and meat or vegetable dishes incorporating spices. The detection of high levels (>1000 cfu per gram) of Bacillus cereus should result in an investigation of the food handling controls used by the food business.

Levels of ≥10000 cfu per gram are considered potentially hazardous as consumption foods with this level of contamination may result in food borne illness. Other Bacillus species, such as Bacillus subtilis and Bacillus licheniformis, have also been associated with food borne illness and may also be tested for using microbiology consulting labs.

Campylobacter should not be present in ready-to-eat foods as consumption of food containing this pathogen may result in food borne illness.

The detection of Campylobacter indicates poor food handling controls, particularly cross contamination (especially where raw poultry is handled) or inadequate cooking (e.g. raw or undercooked meat and poultry). The use of raw milk or of contaminated water may be alternative sources of Campylobacter that should be considered.

Campylobacter Progress in Research No Synopsis Available