Archive for the “Bacteriology” Category

It is something like a dream, Marijuana, which is known in Egypt as “Hashish “, is used now as an antibiotic.

Marijuana is a herb planted in many countries as middle east eastern, Europe & Africa.

It is ingested by smoking, which quickly delivers active ingredients to the blood system. Marijuana has analgesic, anti-emetic, anti-inflammatory, sedative, anti-convulsive, and laxative actions.

Also, it is used in chemotherapy to relieve nausea & vomiting and for AIDS patients as stomachic.

Scientists tested five major active ingredients called cannabinoids on Different strains of MRSAmethicillin resistant Staphylococcus aureus“.

Both natural & synthetic cannabinoids show germ killing activity against MRSA.

These active ingredients exhibit antibacterial activity in a different way, meaning that they might be able to bypass bacterial resistance.

At least two cannabinoids “out of 5″ can be used safely without causing mood alteration.

MRSA like other Staphylococcus spread by contact, so people of close contact are of high danger.

Finally, researchers in the Journal of Natural Products call for the further study of antibacterial uses of marijuana as it is too difficult to find new antibacterials since unfortunately, bacteria became resistant to them.

Source : Web MD

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29 cases of listeriosis have been confirmed in Canada plus 31 suspected cases caused by an outbreak from contaminated meat. A local meat processing plant in Toronto has been blamed. Surely lawsuits have been pouring in after the plant was shut down & a massive recall of the meat products was done with an estimated price toll of 20 million dollars.

Listeria monocytogenes, a gram positive bacterium, penetrates the gastrointestinal epithelium & is engulfed by the host’s leukocytes. Its pathogenesis lays in the ability of the bacterium to grow and multiply within the host’s phagocytic cells. It is considered an important hazard in food industry.

Source: The Vancouver Sun

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The concept of self-sacrifice was discovered within the colonies of the Salmonella bacteria. Merely, a survival strategy. In normal cases, whenever the human body becomes infected by Salmonella, the body’s innate immunity represented in the gastrointestinal tissue barriers and normal commensal intestinal flora, literally fights back.

Fortunately enough for the bacteria, they have a way to tackle down this problem. Basically, they divide themselves in two groups, one ready to sacrifice itself for the well-being & the survival of the other. To elaborate more about this, the 1st group has the job of invading the tissues and thus triggering an inflammatory response which is basically a suicide. The 2nd group awaits for the chance of the inactivation of the normal flora & strikes an attack to find a paved smooth way for host infection.

Nothing in the genome dictates the fate of each specific bacterium since they are all members of the same bacterial colony. The difference in the bacterium’s behaviour within the host tissues is due to the random distribution of the cellular components between the two daughter cells.

This same scenario might also apply on a number of different of pathogenic bacteria. This might give us a closer look on the mechanism of bacterial infection & probably provide us with new ideas on how to tackle it.

Source: ScienceDaily

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Scientists have found out that alligator blood is able to fight different kinds of bacteria including even MRSA “Methicillin-Resistant Staphylococcus aureus“. This is due to the presence of several peptides within the alligator’s blood which pose as a natural barrier against bacterial infection. This particularly comes in handy since alligators are known to live in conditions very preferrable for the growth of microorganisms, mainly in swamps to be exact.

The idea first struck Dr. Mark Merchant when he noticed that despite of their habitat, alligators seem to strive quite normally with scratches & bruises in their skin. Researchers then isolated an alligator’s serum & did a comparative analysis against human serum. Out of 23 strains of bacteria, human serum was able to conquer only eight, while that of the alligator’s stood undefeated against all 23. Not just that, but the serum was also tested on HIV & surprisingly, a great amount of the virus was also destroyed.

Surely, the benefit of this discovery would arise once those peptides are sequenced & their exact chemical structure identified to manufacture them in labs as it would be pretty unreasonable in terms of animal rights AND cost-wise to slaughter alligators for their blood.

Drugs containing these peptides are expected to become available within the next 8-10 years & would definitely prove very useful for patients highly vulnerable to infections as in certain autoimmune diseases, diabetes, burn victims and those with open surgical wounds.

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GBS (purple) invading BBB (red)Many drugs can’t do it, but GBS can!

Bacterial meningitis is one of the leading causes of death and disability among childrens.  Meningits occurs when bacteria cross blood brain barrier  (BBB) after interacting with human Brain microvascular endothelial cells (hBMECs) . Although these cells are exhibiting tight junctions and lacking pinocytosis, some bacteria could cross it and this demonstrates an interplay between host cells and some bacterial factors.

Scientists at USCD school of medicine used a process involving generating and screening of many group B streptococcus (GBS)  in tissue culture model of human BBB (consisting of immortalised hBMECs) . This culture maintained the normal function of human BBB.

 They identified a gene called iagA gene encoding for a glycosyltransferase. A predicted product of the iagA glycosyltransferase is the glycolipid  diglycosyldiacylglycerol involved in anchoring lipoteichoic acid (LTA) and consequently, enhances BBB invasion.

Allelic replacement of the iagA gene,so that the resulting mutants are lacking the gene, shed LTA into the media. As a result, mice infected with mutant gene exhibited less mortality rate -up to 90 percent- compared to wild-type infected mice. Mutant-type infected mice developed bacteremia  as WT which proves the fact that iagA gene plays the central role in BBB invasion without significantly affecting adhesion or blood survival.

Since bacterial meningitis may cause infected children death or many complications as permanent cognitive deficits, blindness, deafness or seizures, an early treatment may help reduce high rates of death and disability.

This early treatment may be much more easily designed after these findings by blocking LTA anchoring on bacterial cell surface.This will help preventing meningitis even though bacteriemia has taken place.

The journal of clinical investigation has the full story.

 

 

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I have to admit that it is pretty odd “or at least for me” to learn the countless aspects of life itself that we, as human beings, share with primitive organsims “as in bacteria”…& yet add another to the growing pile: The Concept of Hand-in-Hand

Helmholtz Centre for Infection Research

Rarely do bacteria grow as single cells, they rather prefer to grow as colonies which adhere to all kinds of surfaces forming “biofilms“. These biofilms have proved to be pretty effective in maintaining the well-being of the bacteria growing within them and needless to say, this possess a serious threat. Nothing seems to work with them, ranging from disinfectants and antibiotics all the way to our very own immune system.

Scientists, now, have identified a mechanism which is thought to be used by the bacteria, within the biofilm, to protect themselves. Pushing star wars aside, these biofilm bacteria are using chemical weapons as their defense.

Taking a model for this study, researchers compared marine bacteria getting attacked by amoebae to these biofilm bacteria getting attacked by phagocytes.

To take a closer look, these bacteria are easily attacked when they are swimming separately in the water, but once they are attached to a surface, the amoebae can no longer harm them. Not only that, but the amoebae were sometimes de-activated or even killed. A classic example of FIGHTING BACK!!
How do they do it?? Through chemical weapons.

Marine bacteria contain the pigment violacein. If the enemy attacks just a single cell, the pigment is released paralyzing and triggering a suicide mechanism in the amoebae.

Amoebae are thought to be the ancestors of some types of pathogens. So, instead of thinking of biofilms as a problem, they may be source of highly effective agents which can only be produced in a biofilm and can help us fight aganist some of these pathogens.

After all, it IS a small world

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To be frank, I was really underestimating these bacteria. Streptococcus iniae, bacteria bothering fish, what’s the big deal? But when I read that it cause them meningoencephalitis due to systemic dissemination resulting in death, it made me sad. They’re fish, you know, they don’t deserve such destiny. (We can’t say that about eating them, right?) Back to scientific details, S. iniae was isolated from Amazon dolphins (Inia) but it has a very wide host range, it can infect fresh & saltwater species like salmon, yellowtail & hybrid striped bass (HSB). It also can infect immunocompromised as well as elders from humans.Fish - Cartoon

S. iniae are beta-hemolytic streptococci, they have M protein (present in cell membrane) then the capsular polysaccharide which interfere with phagocytosis. They also have phosphoglucomutase which make their cell wall rigid & resistant to peptide antimicrobials, besides their streptolysin S. I’ve to tell you this, this iniae is a walking disaster, just like the human version S. pyogenes.

So what scientists tell us this time? Thanks to 454 pyrosequencing & bioinformatics, they identified extra virulence factors of S. iniae. Regulations in S. iniae are done through a Mga-like Mgx loci (multiple gene regulator of group A streptococci). It regulates the virulence factors. It’s used to be known that M-protein is a component of that Mga. This time, discovery of extra components takes place, the M-like surface protein (simA) & C5a peptidase (scpI). A word about scpI, its role is to inactivate C5a (the complement component) to hinder the complement reaction & also has a role in adhesion to epithelial cells.

Actually they’re looking forward to using the mutant delta-simA as a live attenuated vaccine against S. iniae. (Vaccine for fish?) They made mutations in both C5a-like peptidase & simA, apparently simA had the leading role in the virulence of the studied strain of S. iniae. So a new approach of vaccination will be developed instead of the old M protein vaccination strategy which requires multimeric vaccination (to provide protection against several serotypes) & showes autoimmune response. Unlike the ordinary M protein vaccination, vaccination with the mutant delta-simA will result in development of humoral as well as cell-mediated immunity.

Image credits:
Fish – Cartoon: http://www.robdoyle.co.uk/

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Center for Disease Control and Prevention
Recently, it has been all over the news in the United States…warning americans about buying tomatoes, pepper, and different kinds of vegetables “They even suggested some pretty clever alternatives” due to a Salmonella outbreak, which made over 1,200 people sick throughout the nation.

Now “after two months of the intial discovery”, the outbreak has been linked to irrigation water contaminating a certain type of pepper at a Mexican farm, stored in a warehouse in Texas. Officials are being blamed now for putting too much spot-light over tomatoes when in fact they did not significantly contribute to the arousal of the problem in the first place. Their hope now would be to discover that the same irrigation water was also used on tomatoes and not just the pepper.

The FDA declares that it IS safe to eat tomatoes and pepper grown in the US, urging consumers to be open and ask their local grocery stores & restaurants about the source of these vegetables. 
For the time being, I would strongly avoid any Mexian salsa 🙂 

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Nature, mother nature & the famous journal, taught us that every organism has its own defense mechanisms against various predators. For example, the famous antifungal agent (cyclohexamide) is obtained from the bacteria Streptomyces, on the other hand (Penicillin), the antibiotic, comes from the fungus Penicillium.

We all know phages, the nick name of Bacteriophages, the virus-like agents that infect bacteria making it sick.. Well not sick, but only degrade it like any other virus on the planet. As a matter of fact, Bacteria have to develop defense mechanisms against these phages:

1)They can cut their genome with restriction enzymes (endonucleases)

2)They can also undergo changes in their receptors, so the phage goes blind & never find it

3)They can act on the phage itself by making DNA modifications or even repression of their gene expression.

But now we’ll talk about a different defense mechanism (they love to call it: Special Forces). To know it, you’ve to meet CRISPR sequences (clustered, regularly interspaced, short, palindromic repeats). Not crispy, it’s CRISPR. Actually when I first read it, I was totally lost. I knew the meaning of every word separated from the very next. So I checked more & got this from the amazing blog of Tim “Phage Hunter“.

As you’ve read before, they are sequences found in almost 40% of sequenced bacteria & 90% of sequenced archaea. There are already identical repeats which form RNA stem-loops. Between those repeats, researchers found DNA which is similar to that of phages. That means that the bacteria use the RNA interference mechanism (an inhibitory gene expression mechanism).
CRISPR sequences are first transcribed, and then spliced to form small interfering RNA (siRNA), which are complementary to the target mRNA (the phage’s). Once binding achieved, no translation occurs, because they simply cleave it into little pieces.

Bacterial CRISPR is modeled to work as iRNA in eukaryotes

So the array of these sequences is highly useful in determining the bacterial resistance to different phages. Y. pestis (aka Black death) has three CRISPR sequences in its genome. It’s something like acquired immunity, bacteria develop it after the infection of the phage, the survivors of course.

For people On The Run: Bacteria have a complementary sequence of their phages, to capture their RNA, stop the translation process.

Image credits:
Figure shows the role of siRNA in degradation of phage nucleic acids: http://www.phagehunter.org

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