Klebsiella pneumoniae- Lab Diagnosis, Treatment, Prevention
Klebsiella pneumoniae is a gram-negative rod-shaped bacterium that can cause various infections, such as pneumonia, urinary tract infections, septicemia, and wound infections. It is often associated with hospital-acquired infections and antibiotic resistance. To diagnose Klebsiella pneumoniae infection, different types of specimens may be collected depending on the site and nature of the infection. These include:
- Sputum: This is the most common specimen for diagnosing pneumonia caused by Klebsiella pneumoniae. Sputum is the mucus that is coughed up from the lungs. It may contain bacteria, blood, pus, or other materials.
- Blood: This is used to detect bacteremia or septicemia, which are serious conditions where bacteria enter the bloodstream and cause systemic infection. Blood samples are usually drawn from a vein using a sterile needle and syringe.
- Urine: This is used to diagnose urinary tract infections (UTIs) caused by Klebsiella pneumoniae. Urine samples are usually obtained by midstream collection, which means that the first and last portions of urine are discarded and only the middle portion is collected in a sterile container.
- Wound swabs: These are used to identify the bacteria that cause wound infections. Wound swabs are sterile cotton-tipped applicators that are gently rubbed over the infected area and then placed in a transport medium.
The specimens are then sent to a microbiology laboratory for analysis. The laboratory diagnosis of Klebsiella pneumoniae involves two main steps: culture and identification.
Culture is the process of growing bacteria in artificial media under controlled conditions. The purpose of culture is to isolate and identify the causative agent of infection. The specimens are inoculated onto different types of agar plates and incubated at 37°C for 18 to 24 hours. The most commonly used agar plates for Klebsiella pneumoniae are:
- Blood agar: This is a nutrient-rich medium that contains 5% sheep blood. It allows the growth of most bacteria and shows their hemolytic activity, which is the ability to break down red blood cells. Klebsiella pneumoniae usually produces non-hemolytic (gamma-hemolytic) colonies on blood agar, which means that they do not change the color of the medium around them.
- MacConkey agar: This is a selective and differential medium that inhibits the growth of gram-positive bacteria and distinguishes between lactose-fermenting and non-lactose-fermenting gram-negative bacteria. Lactose-fermenting bacteria produce acid from lactose, which lowers the pH of the medium and turns it pink. Non-lactose-fermenting bacteria do not change the color of the medium. Klebsiella pneumoniae is a lactose-fermenting bacterium that produces mucoid (slimy) pink colonies on MacConkey agar.
Identification is the process of confirming the identity of the isolated bacterium by performing various biochemical tests and reactions. The purpose of identification is to determine the species and strain of the bacterium and its susceptibility to antibiotics. Some of the tests and reactions used for identifying Klebsiella pneumoniae are:
- Gram stain: This is a differential staining technique that divides bacteria into two groups based on their cell wall structure: gram-positive (purple) and gram-negative (pink). Klebsiella pneumoniae is a gram-negative bacterium that appears as rod-shaped cells in pairs or short chains under the microscope.
- Capsule stain: This is a special staining technique that detects the presence of a capsule, which is a polysaccharide layer that surrounds some bacteria and protects them from phagocytosis and desiccation. Klebsiella pneumoniae has a prominent capsule that appears as a clear halo around the cells when stained with India ink or crystal violet.
- Indole test: This is a biochemical test that detects the ability of bacteria to produce indole, which is a breakdown product of tryptophan. Indole production is indicated by a red color change when Kovac`s reagent is added to the culture broth. Klebsiella pneumoniae is indole-negative, which means that it does not produce indole.
- Methyl red test: This is a biochemical test that detects the ability of bacteria to produce mixed acids from glucose fermentation. Acid production is indicated by a red color change when methyl red indicator is added to the culture broth. Klebsiella pneumoniae is methyl red-negative, which means that it does not produce enough acid to lower the pH below 4.4.
- Voges-Proskauer test: This is a biochemical test that detects the ability of bacteria to produce acetoin, which is an intermediate product of glucose fermentation. Acetoin production is indicated by a red color change when Barritt`s reagent A and B are added to the culture broth. Klebsiella pneumoniae is Voges-Proskauer-positive, which means that it produces acetoin.
- Citrate test: This is a biochemical test that detects the ability of bacteria to use citrate as their sole carbon source. Citrate utilization is indicated by a blue color change when bromothymol blue indicator is added to Simmons citrate agar. Klebsiella pneumoniae is citrate-positive, which means that it can use citrate as its sole carbon source.
- Urease test: This is a biochemical test that detects the ability of bacteria to produce urease, which is an enzyme that hydrolyzes urea into ammonia and carbon dioxide. Urease production is indicated by a pink color change when phenol red indicator is added to urea broth or agar. Klebsiella pneumoniae is urease-positive, which means that it produces urease.
These tests and reactions can be performed individually or in combination using commercial kits such as API 20E or Enterotube II.
The laboratory diagnosis of Klebsiella pneumoniae infection helps in guiding appropriate treatment and prevention strategies for patients and health care workers.
Blood agar and MacConkey agar are two types of culture media that are commonly used to isolate and identify Klebsiella pneumoniae from clinical specimens. Both media are solid, nutrient-rich and support the growth of a wide range of bacteria. However, they also have some distinctive features that help to differentiate Klebsiella pneumoniae from other organisms.
Blood agar is a medium that contains 5% sheep blood, which provides hemin and other growth factors for bacteria. Blood agar also allows the detection of hemolysis, which is the lysis of red blood cells by some bacteria. Hemolysis can be observed as a clear zone around the bacterial colonies on the agar surface. Depending on the degree and pattern of hemolysis, bacteria can be classified as alpha-hemolytic (partial hemolysis), beta-hemolytic (complete hemolysis) or gamma-hemolytic (no hemolysis). Klebsiella pneumoniae is usually gamma-hemolytic, meaning that it does not cause any hemolysis on blood agar. However, some strains may produce a weak alpha-hemolysis due to the production of a pigment called enterobactin. Klebsiella pneumoniae colonies on blood agar are typically large, smooth, moist and mucoid, due to the presence of a polysaccharide capsule that protects the bacteria from phagocytosis and complement-mediated killing.
MacConkey agar is a medium that contains bile salts, crystal violet and lactose, which inhibit the growth of gram-positive bacteria and select for gram-negative bacteria. MacConkey agar also allows the detection of lactose fermentation, which is the ability of some bacteria to use lactose as a carbon source and produce acid and gas as by-products. Lactose fermentation can be observed as a color change of the medium from red to yellow (due to the lowering of pH by acid production) and/or the formation of gas bubbles in or around the colonies. Depending on their lactose fermentation ability, bacteria can be classified as lactose-fermenters (LF) or non-lactose-fermenters (NLF). Klebsiella pneumoniae is a lactose-fermenter, meaning that it can use lactose as a carbon source and produce acid and gas. Klebsiella pneumoniae colonies on MacConkey agar are typically pink or red, due to the production of acid that neutralizes the crystal violet dye in the medium. They are also large, smooth, moist and mucoid, due to the presence of a capsule.
Therefore, blood agar and MacConkey agar are useful media for isolating and identifying Klebsiella pneumoniae from clinical specimens. By observing the colony morphology, hemolysis pattern and lactose fermentation ability of the bacteria on these media, one can distinguish Klebsiella pneumoniae from other gram-negative bacilli that may cause similar infections. However, these media are not sufficient to confirm the identification of Klebsiella pneumoniae, as some other bacteria may share similar characteristics on these media. Therefore, further tests and reactions are needed to verify the identity of Klebsiella pneumoniae. These tests will be discussed in point 3.
After obtaining pure cultures of Klebsiella pneumoniae from blood agar or MacConkey agar, several biochemical tests and reactions can be performed to confirm the identification of the organism. Some of the commonly used tests are:
- Indole test: Klebsiella pneumoniae is indole negative, meaning that it does not produce indole from tryptophan. This can be detected by adding Kovac`s reagent to the culture medium and observing the color change. A red ring indicates a positive result, while a yellow ring indicates a negative result.
- Methyl red test: Klebsiella pneumoniae is methyl red negative, meaning that it does not produce stable acidic end products from glucose fermentation. This can be detected by adding methyl red indicator to the culture medium and observing the color change. A red color indicates a positive result, while a yellow color indicates a negative result.
- Voges-Proskauer test: Klebsiella pneumoniae is Voges-Proskauer positive, meaning that it produces acetoin from glucose fermentation. This can be detected by adding Barritt`s reagents A and B to the culture medium and observing the color change. A red color indicates a positive result, while a yellow or brown color indicates a negative result.
- Citrate utilization test: Klebsiella pneumoniae is citrate positive, meaning that it can use citrate as a sole carbon source. This can be detected by inoculating the organism on Simmons citrate agar and observing the color change. A blue color indicates a positive result, while a green color indicates a negative result.
- Urease test: Klebsiella pneumoniae is urease positive, meaning that it can hydrolyze urea to ammonia and carbon dioxide. This can be detected by inoculating the organism on urea agar or broth and observing the color change. A pink color indicates a positive result, while an orange or yellow color indicates a negative result.
Other tests that can be used to identify Klebsiella pneumoniae include:
- Lysine decarboxylase test: Klebsiella pneumoniae is lysine decarboxylase positive, meaning that it can decarboxylate lysine to cadaverine. This can be detected by inoculating the organism on lysine decarboxylase broth and observing the color change. A purple color indicates a positive result, while a yellow color indicates a negative result.
- Ornithine decarboxylase test: Klebsiella pneumoniae is ornithine decarboxylase positive, meaning that it can decarboxylate ornithine to putrescine. This can be detected by inoculating the organism on ornithine decarboxylase broth and observing the color change. A purple color indicates a positive result, while a yellow color indicates a negative result.
- Motility test: Klebsiella pneumoniae is non-motile, meaning that it does not have flagella or other structures for movement. This can be detected by inoculating the organism on motility agar or broth and observing the growth pattern. A diffuse growth indicates a positive result, while a confined growth indicates a negative result.
These tests and reactions can help differentiate Klebsiella pneumoniae from other closely related bacteria such as Escherichia coli, Enterobacter aerogenes, Proteus mirabilis, and Serratia marcescens.
Klebsiella pneumoniae is a gram-negative bacterium that can cause serious infections such as pneumonia, urinary tract infections, bloodstream infections, wound infections, and meningitis. These infections can be life-threatening and require prompt and appropriate antibiotic treatment.
However, choosing the right antibiotic for Klebsiella pneumoniae is not always easy, as this bacterium has developed resistance to many commonly used antibiotics. Resistance means that the bacteria can survive or grow despite the presence of the antibiotic. This makes the infection harder to treat and increases the risk of complications and death.
The resistance of Klebsiella pneumoniae can vary depending on the geographic region, the type of infection, and the source of the infection (community or hospital). Therefore, it is important to perform laboratory tests to identify the specific strain of Klebsiella pneumoniae and its susceptibility to different antibiotics. This can help guide the selection of the most effective antibiotic for each case.
In general, the following principles apply to the treatment of Klebsiella pneumoniae infections:
- For community-acquired infections, such as pneumonia or urinary tract infections, the recommended antibiotics are usually third or fourth generation cephalosporins (such as ceftriaxone, cefotaxime, or cefepime) or respiratory quinolones (such as levofloxacin or moxifloxacin). These antibiotics can be given alone or in combination with an aminoglycoside (such as gentamicin or amikacin) for more severe infections.
- For hospital-acquired infections, such as bloodstream infections or wound infections, the recommended antibiotics are usually carbapenems (such as meropenem, imipenem, or ertapenem). These antibiotics are effective against most strains of Klebsiella pneumoniae, including those that produce extended-spectrum beta-lactamases (ESBLs) or carbapenemases. These are enzymes that can break down cephalosporins and carbapenems and make them ineffective. Carbapenems can be given alone or in combination with other antibiotics (such as colistin, tigecycline, or fosfomycin) for more resistant strains.
- The duration of antibiotic treatment depends on the type and severity of the infection, the response to therapy, and the presence of any complications. In general, the treatment should last for at least 7 to 14 days for most infections. However, some infections may require longer courses of treatment (such as 4 to 6 weeks for endocarditis or osteomyelitis).
- The dose and route of administration of the antibiotics depend on the patient`s age, weight, kidney function, and other medical conditions. The antibiotics can be given orally or intravenously depending on the availability and severity of the infection. The dose and frequency may need to be adjusted based on the blood levels of the antibiotics and the clinical response.
- The side effects and interactions of the antibiotics should be monitored closely and reported to the doctor if they occur. Some common side effects include nausea, vomiting, diarrhea, rash, allergic reactions, kidney damage, liver damage, nerve damage, and hearing loss. Some common interactions include antacids, iron supplements, oral contraceptives, warfarin, and probenecid.
- The patient should follow the doctor`s instructions carefully and complete the full course of antibiotic treatment even if they feel better. Stopping the treatment too soon or skipping doses can lead to treatment failure and increase the risk of resistance development.
- The patient should also take measures to prevent reinfection or transmission of Klebsiella pneumoniae to others. These include practicing good hygiene (such as washing hands frequently), avoiding contact with infected people or contaminated objects (such as catheters or ventilators), drinking plenty of fluids (especially for urinary tract infections), and seeking medical attention if symptoms recur or worsen.
Some patients with Klebsiella pneumoniae infection may develop serious complications that require surgical intervention. These include:
- Empyema: This is a condition where pus accumulates in the pleural space, the area between the lungs and the chest wall. Empyema can cause chest pain, fever, shortness of breath, and cough. It can also lead to sepsis, a life-threatening infection of the bloodstream. Empyema is usually treated with antibiotics and drainage of the pus through a chest tube or surgery .
- Lung abscess: This is a condition where a cavity filled with pus forms in the lung tissue. Lung abscess can cause fever, cough, weight loss, and chest pain. It can also lead to respiratory failure, bleeding, or spread of infection to other organs. Lung abscess is usually treated with antibiotics and drainage of the pus through a needle or surgery .
- Pulmonary gangrene: This is a rare condition where a part of the lung tissue dies due to lack of blood supply or infection. Pulmonary gangrene can cause fever, cough, chest pain, and bloody sputum. It can also lead to shock, respiratory failure, or death. Pulmonary gangrene is usually treated with antibiotics and removal of the dead tissue through surgery .
- Respiratory tract obstruction: This is a condition where the airway is blocked by a foreign body, tumor, or inflammation. Respiratory tract obstruction can cause difficulty breathing, wheezing, stridor, or cyanosis. It can also lead to respiratory failure or cardiac arrest. Respiratory tract obstruction is usually treated with removal of the obstruction through bronchoscopy or surgery .
Surgery for Klebsiella pneumoniae infection is usually performed by a thoracic surgeon, a specialist who deals with diseases of the chest. The type and extent of surgery depends on the location and severity of the complication. Surgery may involve removing part or all of the affected lung (lobectomy or pneumonectomy), opening the chest wall (thoracotomy), or inserting a camera and instruments through small incisions (video-assisted thoracoscopic surgery).
Surgery for Klebsiella pneumoniae infection carries some risks and complications, such as bleeding, infection, pain, scarring, lung collapse, air leak, or reduced lung function. The recovery time and outcome vary depending on the patient`s condition and the type of surgery. Patients may need to stay in the hospital for several days or weeks after surgery and may require oxygen therapy, chest physiotherapy, pain medication, antibiotics, or other treatments.
Surgery for Klebsiella pneumoniae infection is not always necessary or possible. Some patients may respond well to medical treatment alone or may have contraindications for surgery, such as advanced age, poor general health, or other medical conditions. The decision to perform surgery should be based on a careful evaluation of the benefits and risks by the patient and the medical team.
One of the major challenges in treating Klebsiella pneumoniae infections is the increasing antimicrobial resistance of this bacterium. Klebsiella pneumoniae can acquire various resistance elements, such as plasmids and transposons, that encode different types of β-lactamases, carbapenemases, aminoglycoside-modifying enzymes, and efflux pumps. These mechanisms can confer resistance to multiple classes of antibiotics, such as penicillins, cephalosporins, carbapenems, aminoglycosides, quinolones, and tetracyclines .
Some strains of Klebsiella pneumoniae have become highly resistant to carbapenems, which are considered as last-resort antibiotics for treating Gram-negative infections. These strains are known as carbapenem-resistant Enterobacteriaceae (CRE) or Klebsiella pneumoniae carbapenemase (KPC)-producing bacteria . Infections caused by these strains are associated with high mortality rates and limited treatment options .
The emergence and spread of antimicrobial resistance in Klebsiella pneumoniae is influenced by several factors, such as the overuse and misuse of antibiotics, the horizontal gene transfer among bacteria, the selective pressure exerted by the host immune system and the environment, and the genetic diversity and adaptability of the bacterium .
Therefore, it is essential to monitor the antibiotic susceptibility patterns of Klebsiella pneumoniae isolates and to implement appropriate infection control measures to prevent the transmission of resistant strains. Moreover, new strategies are needed to develop novel antibiotics or alternative therapies that can overcome the resistance mechanisms of Klebsiella pneumoniae .
Klebsiella pneumoniae infections can be prevented by reducing the exposure to the bacteria and enhancing the host immunity. Some of the preventive measures are:
- Hand washing: This is the most effective way to prevent the transmission of Klebsiella pneumoniae from person to person or from contaminated surfaces or devices. Hand washing should be done before and after contact with patients, after using the bathroom, and before eating or preparing food. Hand washing should be done with soap and water or alcohol-based hand rubs for at least 20 seconds.
- Infection control protocols: In hospitals and other health care settings, infection control protocols should be followed strictly to prevent the spread of Klebsiella pneumoniae among patients and staff. These protocols include wearing gloves, gowns, masks, and eye protection when handling infected patients or specimens, isolating infected patients in single rooms or cohorts, disinfecting equipment and surfaces, and using sterile techniques for invasive procedures.
- Antibiotic stewardship: Antibiotic stewardship is the rational use of antibiotics to optimize clinical outcomes and minimize adverse effects and resistance. Antibiotic stewardship programs should be implemented in hospitals and other health care settings to ensure that antibiotics are prescribed only when necessary, appropriate, and effective. Antibiotic stewardship can help reduce the emergence and spread of multidrug-resistant Klebsiella pneumoniae strains.
- Vaccination: There is currently no vaccine available for Klebsiella pneumoniae infection, but research is ongoing to develop one. Vaccination can potentially prevent or reduce the severity of Klebsiella pneumoniae infection by stimulating the immune system to produce antibodies against the bacteria. Vaccination can also reduce the need for antibiotics and the risk of resistance.
- Immunization: Immunization is the administration of vaccines or other agents that boost the immune system against specific diseases. Immunization can help prevent or reduce the severity of Klebsiella pneumoniae infection by protecting against other respiratory pathogens that may predispose to Klebsiella pneumoniae infection, such as influenza, pneumococcus, and Haemophilus influenzae. Immunization can also reduce the need for antibiotics and the risk of resistance.
- Nutrition and hygiene: Nutrition and hygiene are important factors that affect the immune system and the susceptibility to infections. Nutrition and hygiene can help prevent or reduce the severity of Klebsiella pneumoniae infection by providing adequate nutrients and vitamins that support the immune system, maintaining a healthy weight and body mass index, avoiding smoking and alcohol consumption, drinking enough water and fluids, and practicing good oral and dental hygiene.
By following these preventive measures, Klebsiella pneumoniae infections can be reduced or avoided, improving the health and quality of life of individuals and communities.
Hand washing and infection control protocols are essential measures to prevent the transmission of Klebsiella pneumoniae and other pathogens in healthcare settings. Hand hygiene, which means cleaning your hands by washing with soap and water or using an alcohol-based hand sanitizer, is one of the best ways to avoid getting sick and prevent spreading germs to others. CDC recommends the use of alcohol-based hand sanitizers as the primary method for hand hygiene in most healthcare situations.
Healthcare personnel should use an alcohol-based hand rub or wash with soap and water for the following clinical indications:
- Immediately before touching a patient
- Before performing an aseptic task (e.g., placing an indwelling device) or handling invasive medical devices
- Before moving from work on a soiled body site to a clean body site on the same patient
- After touching a patient or the patient’s immediate environment
- After contact with blood, body fluids, or contaminated surfaces
- Immediately after glove removal
Healthcare personnel should wash their hands with soap and water when hands are visibly soiled or dirty, before eating, after using the restroom, and after caring for patients with vomiting or diarrhoeal illnesses or a suspected or known gastrointestinal infection, such as norovirus or a spore-forming organism such as Clostridioides difficile .
Healthcare facilities should ensure that supplies necessary for adherence to hand hygiene are readily accessible in all areas where patient care is being delivered and that healthcare personnel perform hand hygiene in accordance with CDC recommendations. Healthcare facilities should also implement standard infection control precautions (SICPs) to prevent cross-transmission of microorganisms between patients, staff, and the environment. SICPs include the use of personal protective equipment (PPE), environmental cleaning and disinfection, safe management of waste and linen, and appropriate handling of sharps.
Hand washing and infection control protocols are not only important for healthcare personnel but also for patients and visitors. Patients and visitors should be educated about the importance of hand hygiene and how to perform it correctly. They should also be encouraged to ask healthcare personnel if they have cleaned their hands before providing care. By following these simple steps, everyone can contribute to reducing the risk of Klebsiella pneumoniae infection and improving patient safety.
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