A leading cause of
By Usha Perera
Tuberculosis (TB) is the leading cause of
death in the world from a bacterial infectious
disease. The disease affects 1.8 billion people/year
which is equal to one-third of the entire world
Mycobacterium tuberculosis is the etiologic agent of
tuberculosis in humans. Humans are the only
reservoir for the bacterium.
Mycobacterium bovis is the etiologic agent of TB in
cows and rarely in humans. Both cows and humans can
serve as reservoirs. Humans can also be infected by
the consumption of unpasteurised milk. This route of
transmission can lead to the development of
extrapulmonary TB, exemplified in history by bone
infections that led to hunched backs.
Other human pathogens belonging to the Mycobacterium
genus include Mycobacterium avium which causes a
TB-like disease especially prevalent in AIDS
patients, and Mycobacterium leprae, the causative
agent of leprosy.
Mycobacterium tuberculosis is an obligate aerobe.
For this reason, in the classic case of
tuberculosis, MTB complexes are always found in the
well-aerated upper lobes of the lung
The disease tuberculosis
TB infection means that MTB is in the body, but the
immune system is keeping the bacteria under control.
The immune system does this by producing macrophages
that surround the tubercle bacilli. The cells form a
hard shell that keeps the bacilli contained and
under control. Most people with TB infection have a
positive reaction to the tuberculin skin test.
People who have TB infection but not TB disease are
NOT infectious, i.e., they cannot spread the
infection to other people. These people usually have
a normal chest x-ray. TB infection is not considered
a case of TB disease. Major similarities and
differences between TB infection and TB disease are
given in the table below.
Predisposing factors for TB infection include
l Close contact with large populations of people,
i.e., schools, nursing homes, dormitories, prisons,
l Poor nutrition
l Iv drug use
l HIV infection is the 1 predisposing factor for MTB
infection. 10 percent of all HIV-positive
individuals harbour MTB. This is 400-times the rate
associated with the general public
Because administration of a single drug often leads
to the development of a bacterial population
resistant to that drug, effective regimens for the
treatment of TB must contain multiple drugs to which
the organisms are susceptible. When two or more
drugs are used simultaneously, each helps prevent
the emergence of tubercle bacilli resistant to the
others. However, when the in vitro susceptibility of
a patient’s isolate is not known, which is generally
the case at the beginning of therapy, selecting two
agents to which the patient’s isolate is likely to
be susceptible can be difficult, and improper
selection of drugs may subsequently result in the
development of additional drug-resistant organisms.
A vaccine against MTB is available. It is called BCG
(Bacillus of Calmette and Guerin, named after the
two Frenchmen that developed it). BCG consists of a
live attenuated strain derived from Mycobacterium
bovis. This strain of Mycobacterium has remained
avirulent for over 60 years. The vaccine is not 100%
effective. Studies suggest a 60-80% effective rate
Tuberculosis (MDR TB) and Extensively Drug-Resistant
Tuberculosis (XDR TB)
Resistance to anti-TB drugs can occur when these
drugs are misused or mismanaged. Examples include
when patients do not complete their full course of
treatment; when health-care providers prescribe the
wrong treatment, the wrong dose, or length of time
for taking the drugs; when the supply of drugs is
not always available, or when the drugs are of poor
Multidrug-resistant tuberculosis (MDR TB) is TB that
is resistant to at least two of the best anti-TB
drugs, isoniazid and rifampicin. These drugs are
considered first-line drugs and are used to treat
all persons with TB.
Extensively drug resistant TB (XDR TB) is a
relatively rare type of MDR TB. XDR TB is defined as
TB which is resistant to isoniazid and rifampin,
plus resistant to any fluoroquinolone and at least
one of three injectable second-line drugs (i.e.,
amikacin, kanamycin, or capreomycin). Because XDR TB
is resistant to first-line and second-line drugs,
patients are left with less effective treatment
options, and cases often have worse treatment
Both MDR TB and XDR TB are more common in TB
patients that do not take their medicines regularly
or as prescribed, or who experience reactivation of
TB disease after having taken TB medicine in the
|A landmark happening in Sri
The DOTS treatment method has
been successfully implemented in Sri Lanka for the
past decade but it was limited to the government
health sector. But as a land mark happening in Sri
Lanka, two DOTS treatment centres were opened at two
private hospitals in Sri Lanka, namely Asiri Medical
Hospital at Narahenpita and Hemas Hospital at
According to the officials of the National Programme
for the Control of Tuberculosis and Chest Diseases,
this will be expanded to the private sector
hospitals in all the districts in Colombo in the
future. This was a need to cater to a sector of the
population who patronize the private sector health
services rather than the public sector.
According to the District TB Control Medical
Officers of Colombo and Gampaha, the services at
both hospitals will be completely free for the
patients and the centre will be open for twenty four
hours of the day. This is to enable people to take
their treatment after working hours.
Speaking at the opening of the DOTS centre at Asiri
Hospital, Health Minister Maithripala Sirisena said
that every year around 11,000 new Tuberculosis (TB)
patients are discovered and 2,000 of them are from
Colombo. Out of this number, 1,000 are detected from
the Colombo Municipality. The Minister further
mentioned the rapidly increasing population in the
Colombo city, environmental pollution, and similar
reasons are behind the increasing number of TB
patients in the Colombo city. In the early nineties,
TB was a scary disease that could not be cured. But
now TB can be completely cured within six months
with proper treatment.
Minister Sirisena pointed out that private and
public sectors should join hands to deliver a better
service to the public. President Mahinda Rajapaksa’s
Government always promotes the partnership between
State and private sector. A healthy society can be
created with the participation of both the State and
People like to visit private hospitals when they are
concerned about their privacy and the
confidentiality. Therefore they like to get
treatment for TB from private hospitals than State
|What is DOT
Directly Observed Treatment (DOT) and the method is
that a trained health care worker or other
designated individual (excluding a family member)
provides the prescribed TB drugs and watches the
patient swallow every dose.
Why use DOT’S?
We cannot predict who will take medications as
directed, and who will not. People from all social
classes, educational backgrounds, ages, genders, and
ethnicities can have problems taking medications
Studies show that 86-90% of patients receiving DOT
complete therapy, compared to 61% for those on
DOT helps patients finish TB therapy as quickly as
possible, without unnecessary gaps.
DOT helps prevent TB from spreading to others.
DOT decreases the risk of drug-resistance resulting
from erratic or incomplete treatment.
DOT decreases the chances of treatment failure and
Who can deliver DOT’S?
A nurse or supervised outreach worker from the
patient’s county public health department normally
In some situations, it works best for clinics, home
care agencies, correctional facilities, treatment
centers, schools, employers, and other facilities to
provide DOT, under the guidance of the local health
Family members should not be used for DOT. DOT
providers must remain objective.
How is DOT’S administered?
delivering the prescribed medication
checking for side effects
watching the patient swallow the medication
documenting the visit
DOT should be initiated when TB treatment starts. Do
not allow the patient to try self-administering
medications and missing doses before providing DOT.
If the patient views DOT as a punitive measure,
there is less chance of successfully completing
The prescribing physician should show support for
DOT by explaining to the patient that DOT is widely
used and very effective. The DOT provider should
reinforce this message.
DOT works best when used with a patient-centered
case management approach, including such things as:
helping patients keep medical appointments
providing ongoing patient education
offering incentives and/or enablers
connecting patients with social services or
Patients taking daily therapy can usually
self-administer their weekend doses.
How can a DOT’S provider build rapport and trust?
1. “Start where the patient is.”
2. Protect confidentiality.
3. Communicate clearly.
4. Avoid criticizing the patient’s behavior;
respectfully offer helpful suggestions for change.
5. Be on time and be consistent.
6. Adopt and reflect a nonjudgmental attitude.
|Tuberculosis: Infection vs
TB Infection TB disease in lungs
MTB present MTB present
Tuberculin skin test positive Tuberculin skin test
Chest X-ray normal Chest X-ray usually reveals
Sputum smears and cultures negative Sputum smears
and cultures positive
No symptoms Symptoms such as cough, fever, weight
Not infectious Often infectious before treatment
Not defined as a case of TB Defined as a case of TB
|Drug relapse brain region
Scientists in the US have
identified an area of the brain which makes
heroin-addicted rats relapse.
The study, published in Nature Neuroscience, showed
that part of the medial prefrontal cortex was
When the researchers blocked nerve cells in the
region, there were fewer relapses.
Experts in the UK said the study was a technical
‘tour de force’; however, it did not promise new
treatments in humans.
The study worked on the idea that when addicts
stopped taking drugs, but then returned to the place
they were taking drugs, they were likely to relapse.
Rats were trained to take drugs in one environment,
where they were delivered a dose of heroin.
The rodents then “went to rehab” in another
environment where the feel of the floor, lights and
sounds were different and there was no access to
Once the rats were “clean” they were returned to the
drug-taking environment, where they demonstrated
By examining the rats’ brains, the researchers
showed increased activity in some neurons in the
medial prefrontal cortex.
They then used drugs, muscimol and baclofen, to
selectively inhibit this region. Heroin-seeking
activity was then decreased.
Dr Jennifer Bossert, from the National Institute on
Drugs Abuse in the US, told the BBC: “There are two
main implications, at a research level we’ve
demonstrated this cause/effect relationship in a
specific set of activated neurons.
“In the clinical setting, heroin relapse is
different to cocaine relapse so drug relapse is
probably caused by different circuits for different
drugs, which would have consequences for
She also warned about transferring the findings into
humans, saying: “You have to be very careful, you
can’t. Human addicts are very different to rat
models, they’re often multi-drug users, they’re
Ian Stolerman, Emeritus Professor of Behavioural
Pharmacology at King’s College London, said: “It’s a
considerable achievement, it’s a research tour de
force, which sheds new insight into the nerve cells
in the brain which are important for drug-seeking
behaviour in animal models.”
“It doesn’t, however, suggest a route for new
treatments in the near future.”
|Key breast cancer ‘driver’
Cancer experts have
identified a gene which can cause a particularly
aggressive form of breast cancer to develop.
ZNF703 is the first “oncogene” to be discovered in
It is overactive in around one in 12 breast cancers.
Cancer Research UK, whose scientists carried out the
work, said the gene was a “prime candidate” for the
development of new breast cancer drugs.
An oncogene is one which would normally help
instruct healthy cells to divide but if it becomes
overactive, it upsets the normal checks and balances
that control that process.
That damage is described as being “like a car’s
accelerator becoming stuck down”, and the cell and
all its daughter cells are permanently instructed to
Her2 – another oncogene – is already tested for. The
drug Herceptin was developed to treat Her2 positive
In two patients studied, ZNF703 was the only gene
shown to be overactive, showing it was driving the
development of the cancer.
Professor Carlos Caldas, of the Cambridge Research
Institute, who led the research, said: “Scientists
first discovered this region of DNA may be
harbouring genes linked to the development of breast
cancer 20 years ago.
“But it’s only with the technology we have today
that we’ve been able to narrow down the search
sufficiently to pinpoint the gene responsible.”
He added: “Crucially, testing whether this gene is
overactive in a patient’s tumour could help
highlight those more likely to be resistant to
standard hormone therapies, helping to make sure the
right drugs are matched to the right patient.”
Dr Lesley Walker, director of cancer information at
Cancer Research UK, said: “This is the first gene of
its kind to be discovered in breast cancer for five
“This is exciting because it’s a prime candidate for
the development of new breast cancer drugs designed
specifically to target tumours in which this gene is
“Hopefully this will lead to more effective cancer
treatments in the future.”
Dr Rachel Greig, of Breakthrough Breast Cancer said
the research was “a vital step in understanding the
genes that drive the growth of some types of breast