Nosocomial Infections

Microorganisms in the Hospital

Nosocomial infections can cause severe pneumonia and infections of the urinary tract, bloodstream, and other parts of the body.

Learning Objectives

Give examples of hospital-acquired infections (HAI) or nosocomial infections

Key Takeaways

Key Points

  • Some well known nosocomial infections include: ventilator-associated pneumonia, Methicillin resistant Staphylococcus aureus, Candida albicans, Acinetobacter baumannii, Clostridium difficile, Tuberculosis, Urinary tract infection, Vancomycin-resistant Enterococcus and Legionnaires’ disease.
  • Methicillin-resistant Staphylococcus aureus ( MRSA ) is a bacterium responsible for several difficult-to-treat infections in humans.
  • Hospital acquired pneumonia is the second most common nosocomial infection (urinary tract infection is the most common) and accounts for 15-20% of the total.

Key Terms

  • nosocomial infection: an infection whose development is favoured by a hospital environment, such as one acquired by a patient during a hospital visit or one developing among hospital staff
  • MRSA: Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium responsible for several difficult-to-treat infections in humans. It is also called multidrug-resistant Staphylococcus aureus and oxacillin-resistant Staphylococcus aureus (ORSA).
  • pneumonia: An acute or chronic inflammation of the lungs caused by viruses, bacteria or other microorganisms, or sometimes by physical or chemical irritants.
  • nosocomial: A nosocomial infection, also known as a hospital-acquired infection or HAI, is an infection whose development is favoured by a hospital environment, such as one acquired by a patient during a hospital visit or one developing among hospital staff.

A nosocomial infection, also known as a hospital-acquired infection or HAI, is an infection whose development is favoured by a hospital environment, such as one acquired by a patient during a hospital visit, or one developed among hospital staff. Such infections include fungal and bacterial infections, and are aggravated by the reduced resistance of individual patients.

In the United States, the Centers for Disease Control and Prevention estimated roughly 1.7 million hospital-associated infections, from all types of microorganisms (including bacteria), cause or contribute to 99,000 deaths each year. In Europe, where hospital surveys have been conducted, the category of Gram-negative infections are estimated to account for two-thirds of the 25,000 deaths each year. Nosocomial infections can cause severe pneumonia and infections of the urinary tract, bloodstream, and other parts of the body. Many types are difficult to attack with antibiotics, and antibiotic resistance is spreading to Gram-negative bacteria that can infect people outside the hospital.

Known nosocomial infections include:

  • Ventilator-associated pneumonia
  • Staphylococcus aureus
  • Methicillin resistant Staphylococcus aureus
  • Candida albicans
  • Pseudomonas aeruginosa
  • Acinetobacter baumannii
  • Stenotrophomonas maltophilia
  • Clostridium difficile
  • Tuberculosis
  • Urinary tract infection
  • Hospital-acquired pneumonia
  • Gastroenteritis
  • Vancomycin-resistant Enterococcus
  • Legionnaires’ disease.

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium responsible for several difficult-to-treat infections in humans. It is also called multidrug-resistant Staphylococcus aureus and oxacillin-resistant Staphylococcus aureus (ORSA). MRSA is any strain of Staphylococcus aureus that has developed resistance to beta-lactam antibiotics, which include the penicillins (methicillin, dicloxacillin, nafcillin, oxacillin, etc.) and the cephalosporins. Strains unable to resist these antibiotics are classified as methicillin-sensitive Staphylococcus aureus, or MSSA. The development of such resistance does not cause the organism to be more intrinsically virulent than strains of Staphylococcus aureus that have no antibiotic resistance, but resistance does make MRSA infection more difficult to treat with standard types of antibiotics, and thus more dangerous.

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Resistant bacterial strain: Methicillin-resistant Staphylococcus aureus.

Hospital-acquired pneumonia (HAP), or nosocomial pneumonia, refers to any pneumonia contracted by a patient in a hospital at least 48-72 hours after being admitted. It is usually caused by a bacterial infection, rather than a virus. HAP is the second most common nosocomial infection (urinary tract infection is the most common), and accounts for 15-20% of the total. It is the most common cause of death among nosocomial infections, and is the primary cause of death in intensive care units.

Compromised Host

Numerous risk factors in the hospital setting can predispose a patient to infection.

Learning Objectives

Discuss the risk factors that contribute to the acquiring of nosocomial infections or hospital-acquired infections

Key Takeaways

Key Points

  • People in hospitals are usually already in a “poor state of health,” impairing their defense against bacteria.
  • Invasive devices bypass the body’s natural lines of defense against pathogens and provide an easy route for infection.
  • Patients’ treatments can leave them vulnerable to infection.

Key Terms

  • infection: An uncontrolled growth of harmful microorganisms in a host.
  • defense: The action of defending or protecting from attack, danger, or injury.
  • Invasive: Invasive species, also called invasive exotics or simply exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions.

Susceptible Hosts

A nosocomial infection, also known as a hospital-acquired infection or HAI, is an infection whose development is favoured by a hospital environment, such as one acquired by a patient during a hospital visit or one developing among hospital staff. Such infections include fungal and bacterial infections. They are aggravated by the reduced resistance of individual patients. Numerous risk factors in the hospital setting predispose a patient to infection. These risk factors can broadly be divided into three areas.

  • People in hospitals are usually already in a ‘poor state of health’, impairing their defense against bacteria. Advanced age or premature birth, along with immunodeficiency (due to drugs, illness, or irradiation) present a general risk, while other diseases can present specific risks; for instance, chronic obstructive pulmonary disease can increase chances of respiratory tract infection.
  • Invasive devices, for instance intubation tubes, catheters, surgical drains, and tracheostomy tubes all bypass the body’s natural lines of defense against pathogens and provide an easy route for infection. Patients already colonized at the time of admission are instantly put at greater risk when they undergo invasive procedures.
  • Patients’ treatments can leave them vulnerable to infection: immunosuppression and antacid treatment undermine the body’s defences, while antimicrobial therapy (removing competitive flora and only leaving resistant organisms) and recurrent blood transfusions have also been identified as risk factors.

Prevention

Hospitals have sanitation protocols regarding uniforms, equipment sterilization, washing, and other preventive measures. Thorough hand washing and/or use of alcohol rubs by all medical personnel before and after each patient contact is one of the most effective ways to combat nosocomial infections. More careful use of antimicrobial agents, such as antibiotics, is also considered vital. Despite sanitation protocol, patients cannot be entirely isolated from infectious agents. Furthermore, patients are often prescribed antibiotics and other antimicrobial drugs to help treat illness; this can increase the selection pressure for the emergence of resistant strains.

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Surgical drain: Surgical drain on the left hand after surgery of Bennet’s fracture basis MTC primi manus 1. sin (S62.20) which was treated by alignment of a fracture and inside fixation by two titanium screws MS.

Chain of Transmission

The most important and frequent mode of transmission of nosocomial infections is by direct contact.

Learning Objectives

Differentiate between the various types of transmission: air-borne, common vehicle, vector borne, direct and indirect contact transmission

Key Takeaways

Key Points

  • Contact transmission is divided into two subgroups: direct-contact transmission and indirect-contact transmission.
  • Direct-contact transmission involves a direct body surface-to-body surface contact and physical transfer of microorganisms.
  • Indirect-contact transmission involves contact of a susceptible host with a contaminated intermediate object, usually inanimate.

Key Terms

  • microorganisms: A microorganism or microbe is a microscopic organism that comprises either a single cell (unicellular), cell clusters, or multicellular relatively complex organisms.
  • susceptible: likely to be affected by something; here, sensitive to growth inhibition by an antimicrobial drug.
  • transmission: Transmission is the passing of a communicable disease from an infected host individual or group to a conspecific individual or group, regardless of whether the other individual was previously infected.

The drug-resistant Gram-negative bacteria, for the most part, threaten only hospitalized patients whose immune systems are weak. They can survive for a long time on surfaces in the hospital and they enter the body through wounds, catheters, and ventilators.

The most important and frequent mode of transmission of nosocomial infections is by direct contact.

Transmission occurs when droplets containing microbes from the infected person are propelled a short distance through the air and deposited on the host’s body; droplets are generated from the source person mainly by coughing, sneezing, and talking, and during the performance of certain procedures, such as bronchoscopy.

Dissemination can be either airborne droplet nuclei (small-particle residue {5 µm or smaller in size} of evaporated droplets containing microorganisms that remain suspended in the air for long periods of time) or dust particles containing the infectious agent. Microorganisms carried in this manner can be dispersed widely by air currents and may become inhaled by a susceptible host within the same room or over a longer distance from the source patient, depending on environmental factors; therefore, special air-handling and ventilation are required to prevent airborne transmission. Microorganisms transmitted by airborne transmission include Legionella, Mycobacterium tuberculosis and the rubeola and varicella viruses.

Common vehicle transmission applies to microorganisms transmitted to the host by contaminated items, such as food, water, medications, devices, and equipment.

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Cross-transmission: Contaminated surfaces increase cross-transmission.

Vector borne transmission occurs when vectors such as mosquitoes, flies, rats, and other vermin transmit microorganisms.

Contact transmission is divided into two subgroups: direct-contact transmission and indirect-contact transmission.

Direct-contact transmission involves a direct body surface-to-body surface contact and physical transfer of microorganisms between a susceptible host and an infected or colonized person, such as when a person turns a patient, gives a patient a bath, or performs other patient-care activities that require direct personal contact. Direct-contact transmission can also occur between two patients, with one serving as the source of the infectious microorganisms and the other as a susceptible host.

Indirect-contact transmission involves contact of a susceptible host with a contaminated intermediate object, usually inanimate, such as contaminated instruments, needles, or dressings, or contaminated gloves that are not changed between patients. In addition, the improper use of saline flush syringes, vials, and bags has been implicated in disease transmission in the US, even when healthcare workers had access to gloves, disposable needles, intravenous devices, and flushes.

Control of Nosocomial Infections

Hospitals have sanitation protocols regarding uniforms, equipment sterilization, washing, and other preventive measures.

Learning Objectives

Give examples of ways nosocomial infections can be controlled or prevented

Key Takeaways

Key Points

  • Handwashing frequently is called the single most important measure to reduce the risks of transmitting skin microorganisms from one person to another or from one site to another on the same patient.
  • Thorough hand washing and/or use of alcohol rubs by all medical personnel before and after each patient contact is one of the most effective ways to combat nosocomial infections.
  • Sanitizing surfaces is an often overlooked, yet crucial, component of breaking the cycle of infection in health care environments.

Key Terms

  • sterilization: Any process that eliminates or kills all forms of microbial life present on a surface, solution, or solid compound.
  • nosocomial: contracted in a hospital, or arising from hospital treatment
  • sanitation: The policy and practice of protecting health through hygienic measures.

Diligence and Strategic Behaviors

Hospitals have sanitation protocols regarding uniforms, equipment sterilization, washing, and other preventive measures. Thorough hand washing and/or the use of alcohol rubs by all medical personnel before and after each patient contact is one of the most effective ways to combat nosocomial infections. More careful use of antimicrobial agents, such as antibiotics, is also considered vital.

Despite sanitation protocol, patients cannot be entirely isolated from infectious agents. Furthermore, patients are often prescribed antibiotics and other antimicrobial drugs to help treat illness; this may increase the selection pressure for the emergence of resistant strains.

Sterilization goes further than just sanitizing. It kills all microorganisms on equipment and surfaces through exposure to chemicals, ionizing radiation, dry heat, or steam under pressure.

Isolation precautions are designed to prevent transmission of microorganisms by common routes in hospitals. Because agent and host factors are more difficult to control, interruption of transfer of microorganisms is directed primarily at transmission.

The Importance of Handwashing

Handwashing is the single most important measure to reduce the risks of transmitting skin microorganisms from one person to another or from one site to another on the same patient. Washing hands as promptly and thoroughly as possible between patient contacts and after contact with blood, body fluids, secretions, excretions, and equipment or articles contaminated by them is an important component of infection control and isolation precautions.

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Hand washing with soap: Handwashing is the single most important measure to reduce the risks of transmitting skin microorganisms from one person to another or from one site to another on the same patient.

The spread of nosocomial infections among immunocompromised patients is connected with health care workers’ hand contamination in almost 40% of cases. This presents a challenging problem in the modern hospitals. The best way for workers to overcome this problem is by conducting correct hand- hygiene procedures; this is why in 2005 the WHO launched the GLOBAL Patient Safety Challenge.

Two categories of micro-organisms can be present on health care workers’ hands: transient flora and resident flora. The first is represented by the micro-organisms taken by workers from the environment, and the bacteria in it. These are often capable of surviving on the human skin and sometimes to grow. The second group is represented by the permanent micro-organisms living on the skin surface, on the stratum corneum or immediately under it. They are capable of surviving on the human skin and of growing freely on it. They have low pathogenicity and infection rate, and they create a kind of protection from the colonization from other more pathogenic bacteria.

The skin of workers is colonized by 3.9 x 104 – 4.6 x 106 cfu/cm2. The microbes comprising the resident flora are: Staphylococcus epidermidis, S. hominis, and Microccocus, Propionibacterium, Corynebacterium, Dermobacterium, and Pitosporum spp., while in the transitional could be found S. aureus, and Klebsiella pneumoniae, and Acinetobacter, Enterobacter and Candida spp. The goal of hand hygiene is to eliminate the transient flora with a careful and proper performance of hand washing, using different kinds of soap, both normal and antiseptic, and alcohol-based gels. The main problems found in the practice of hand hygiene are connected with the lack of available sinks and the time-consuming performance of hand washing. An easy way to resolve this problem could be the use of alcohol-based hand rubs, because of faster application compared to correct hand washing.

The Second Line of Defense: Gloves

Gloves play an important role in reducing the risks of transmission of microorganisms. Gloves are worn for three important reasons in hospitals.

  • They are worn to provide a protective barrier and to prevent gross contamination of the hands when touching blood, body fluids, secretions, excretions, mucous membranes, and non-intact skin. In the USA, the Occupational Safety and Health Administration (OSHA) has mandated wearing gloves to reduce the risk of blood-borne pathogen infections.
  • Gloves are worn to reduce the likelihood microorganisms present on the hands of personnel will be transmitted to patients during invasive or other patient-care procedures that involve touching a patient’s mucous membranes and nonintact skin.
  • They are worn to reduce the likelihood the hands of personnel contaminated with micro-organisms from a patient or a fomite (contaminated object) can be transmitted to another patient. In this situation, gloves must be changed between patient contacts, and hands should be washed after gloves are removed.

Surfaces

Sanitizing surfaces is an often overlooked, yet crucial, component of the strategy for the cycle of infection in health care environments. Modern sanitizing methods such as NAV-CO2 have been effective against gastroenteritis, MRSA, and influenza agents. Use of hydrogen peroxide vapor has been clinically proven to reduce infection rates and risk of acquisition. Hydrogen peroxide is effective against endospore-forming bacteria, such as Clostridium difficile, where alcohol has been shown to be ineffective.

Microorganisms are known to survive on inanimate “touch” surfaces for extended periods of time. This can be especially troublesome in hospital environments, where patients with immunodeficiencies are at enhanced risk for contracting nosocomial infections.

Wearing an apron during patient care reduces the risk of infection. The apron should either be disposable or be used only when caring for a specific patient.