Resistant types and basic mechanisms and epidemiology of key resistant pathogens in Africa

Hello, my name is Dr. Kenneth Iregbu. I’m a consultant clinical microbiologist, National Hospital Abuja. I’m giving a lecture on Introduction to Clinical Microbiology.

First, we ask, what are bacteria? Bacteria are a group of germs that cause infections in humans. They are found in many places in nature, including the environment, especially the hospital environment, the human body, and plants. Bacteria cause different types of infectious diseases in different parts of the body. Some of these infections are mild, while some of them are life threatening. Some of the infections that you are familiar with include boils, wound infection, cholera, meningitis, pneumonia, bloodstream infections, urine tract infection, etcetera. Now, there are different types of bacteria.

They are usually grouped according to certain properties, which are common to members of the group. One of the commonest ways of grouping them is their appearance when stained by certain dyes which are commonly used in the laboratory. Usually bacteria are not visible with the naked eye. And so it must be stained to be well visualised under the microscope.

Now, the Gram stain, which is a very common stain used in the laboratory, and, as matter of fact, is the commonest stain used in the laboratory in microbiology. Now, this stain separates most bacteria into two major groups called the Gram-positive and the Gram-negative bacteria. When the Gram stain is used, the Gram-positive bacteria will appear purple while the Gram-negative ones will appear pink or red. How do we classify bacteria? One, bacteria may be classified based on their shape.

Some of them are spherical, and they are called cocci. Some are cylindrical in shape while some are rod-shaped. These are usually called the bacilli.

These are the two commonest shapes found among bacteria. A few others may be comma-shaped. Some are spiral-shaped. Some are spindle-shaped, while some other ones too are s-shaped. Now, some bacteria are motile, while others are not. Disease-causing bacteria– now, not all bacteria cause diseases in humans. Those that cause disease, are described as pathogenic, while those that do not cause disease, are described as non-pathogenic. Some will not ordinarily cause disease, but when the body is– the body’s protection is weak, as is found in HIV/AIDS patients, patients with diabetes mellitus, cancer patients, or poor people who are poorly fed, or in some cases when the skin is cut as in surgery or injury, these bacteria can now cause disease.

Now, this group we describe as opportunistic pathogens, which means they cause disease when given the opportunity to do so. Some bacteria are more common in infections than others. Now, among the cocci bacteria, the common ones are Staphylococcus aureus. This will cause infections such as wound infections, boils, whitlow, skin infections, breast infections. Streptococcus pneumonia, which causes community-acquired pneumonia– it can also cause ear infections, bloodstream infections, meningitis. Neisseria meningitidis, which causes meningitis, particularly in the African Zone, associated with outbreaks, including Nigeria– Neisseria gonorrhoea will cause gonorrhoea disease. Streptococcus pyogenes is the commonest bacterial cause of sore throat. And disease may sometimes result in heart disease or kidney disease. Then we have Enterococcus faecalis, which is a common cause of urine tract infection.

It can also cause heart infections, and abdominal infections, et cetera. Now, all these cocci mentioned above are Gram-positive except the Neisseria meningitidis and Neisseria gonorrhoea, which are Gram-negative cocci. Now, for the bacillus, there are many that cause disease. Examples include Escherichia coli and Klebsiella pneumoniae, which are noted for causing most of urinary tract infection, meningitis in the newborn, bloodstream infections, and others. Vibrio cholera is an agent of the common disease known as cholera. Salmonella typhi causes typhoid disease. Shigella dysenteriae causes bacillary dysentery. Now, treatment of bacterial infections– these infections are treated with a group of drugs called antibiotics. Antibiotics do not treat viral diseases.

In the past, most of the bacteria were killed by available antibiotics and patients got well quick with only few deaths occurring. Presently, many of the bacteria can no longer be killed by most available antibiotics. This makes treatment of bacterial infections very difficult, resulting in long hospital admissions, more serious sicknesses, more deaths, more spending in drugs, and greater costs on health care. This ability of bacteria to withstand drugs that initially killed them is called resistance. Now, for these resistant bacteria, more expensive and more toxic drugs are required for their treatment. Even at least some of them still are difficult to treat. So using expensive and toxic drug does not guarantee a cure.

There are some bacteria that cannot be treated with any of the available antibiotics today. In some of these resistant bacteria, the drugs cannot even penetrate into the bacteria. In some others, they produce substances called enzymes that can destroy the drugs before they have the chance of acting on the bacteria. Some bacteria are able to pump the drugs out of their bodies if they ever penetrate. One very common and most prominent enzymes are collectively called beta lactamases. There are different types of beta lactamases. Penicillinases– these ones act against penicillins such as ampicillin, amoxicillin, and others. Cephalosprinases, these ones act against drugs called cephalosporins, such as cefuroxime, ceftriaxone. And they also act against penicillins. Carbapenemases, they act against drugs called carbapenems.

Examples include imipenem, meropenem, and also act against cephalosporins and penicillins. What are reasons for resistance? One of the things that make bacteria to develop resistance is inappropriate use of the antibiotics. When bacteria are exposed to insufficient dose of antibiotics or exposed to them for too long a time, that will make them to develop resistance with time.

Therefore, using antibiotics when it is not necessary or indulging in self-medication may be helping resistance to develop. Some of these resistant bacteria are carried in the human bodies, such as skin and intestine, especially those who have been on admission in hospital or cared for patients in the hospital. Even visitors to patients in hospital can carry these bacteria home and spread to other members of their families. Why are resistant bacteria more in hospitals? Resistant bacteria are mostly found in the hospitals because of high use of antibiotics. They are commonly spread from the environment to patients, health workers to patients, especially through their hands, and from patients to patients. They can also spread from patients and environments to health workers and visitors.

It is therefore necessary that we have clean environments, engage in hand hygiene and appropriate behaviour while in hospitals by patients, health care workers and visitors. All are required to minimise transmission of resistant bacteria– thank you.