Nosocomial Infections

Nosocomial infections also known as hospital acquired infections are infections not present and without evidence of incubation at the time of admission to a healthcare setting. They become evident 48 hours after admission or 48 hours after patient is discharged.

The most common types of nosocomial infections are respiratory, genitourinary, gastrointestinal and surgical infections. They are usually caused by breaches of infection control practices and procedures, non-sterile and unclean environment and also ill staff.

Definition of nosocomial infections

 * NI - not an infection contracted by health care personnel in the course of their profession - professional infection.
 * Basic feature of NI - hospital strains have higher resistance to antimicrobials and disinfection.
 * Cause of higher morbidity and mortality.

Classification of nosocomial infections
By agent:
 * Exogenous - the agent is introduced into the organism from outside;
 * endogenous - own infectious agent from the colonized site into another system, into a wound, into serosal cavities (Blood, during surgery, invasive procedures, immunosuppressive treatment); the etiologic agent is the microflora present in the body, which is normally non-pathogenic.

According to the epidemiological point of view:
 * non-specific - reflect the epidemiological situation in the catchment area of the health facility or are an indicator of the hygiene level of the facility;
 * specific - a consequence of diagnostic and therapeutic procedures, their occurrence can be influenced by asepsis, sterilization, disinfection, hygiene-epidemiological regime.

According to the affected system:
 * respiratory;
 * catheter - from the bloodstream;
 * uroinfection;
 * gastrointestinal;
 * wound infections;
 * genital tract;

Process of spreading nosocomial infections

 * Existence of a source of the causative agent - Transmission of the causative agent by NI - Presence of a susceptible individual - Transmission of the causative agent by NI - Presence of a susceptible individual.

Source - Nosocomial agent

 * Patient - his own microflora, another patient (his microflora is in saliva, on hands, in air, dust, tools, etc.).
 * Health care worker - does not appreciate his own disease.
 * Visitor - least serious source, control of visitors.

Forms of nosocomial infections

 * Manifest - less dangerous, easily diagnosed and treatable.
 * Carriage - carriers harbor and excrete infectious agents without obvious signs of disease.

Nosocomial transmission

 * Direct transmission:
 * presence of a source of infection and a susceptible individual;
 * contact (e.g., kissing/sexual contact);
 * essentially transmission by the hands of health care personnel;
 * in newborns - ocular infection (direct contact with the mucous membrane of the vagina);
 * droplet infection;
 * alimentary route - preparation of milk food in the neonatal unit.
 * Indirect transmission depends on:
 * the ability of the microorganism to survive outside the host body;
 * the existence of a suitable medium in which the aetiological agent multiplies and with the help of which the infection is transmitted.

Most common bacterial agents of nosocomial infections

 * Staphylococcus,
 * Enterococcus,
 * Streptococcus pneumoniae,
 * Clostridium difficile,
 * Enterobacteriaceae,
 * Pseudomonas aeruginosa,
 * Helicobacter pylori,
 * Mycobacterium species,
 * mycotic agents.

Mechanism of bacterial resistance

 * ATBs have been used for more than 50 years.
 * ATBs are a substantial part of all drug costs.
 * Adequate application of ATBs - economics and spread of resistance.
 * Emergence of resistance - most in ICU and ARO settings - multiple ATB applications.

Most important microorganisms: gram-positive bacteria

 * MRSA - methicillin-resistant Staphylococcus aureus.
 * MRCNS - methicillin-resistant coagulase-negative staphylococcus aureus.
 * VISA - Staphylococcus aureus with reduced susceptibility to vancomycin.
 * PRSP - Streptococcus pneumoniae resistant to PNC.
 * VRE - vancomycin-resistant enterococci.
 * Enterococci with high resistance to aminoglycosides.

Most important microorganisms: gram-negative bacteria

 * With production of broad-spectrum &beta;-lactamases encoded plasmidvertically and chromosomelaterally (ESBL).
 * With resistance to carbapenems.
 * With resistance to fluoroquinolones.
 * With resistance to aminoglycosides.

Resistant strains of MRSA

 * Identified in 1961.
 * In the US, incidence increased from 2.4% in 1975 to 30-60% after 1990.
 * Scandinavia - still 1% in 1990.
 * Spain and France - more than 30%.
 * 1990 in Central Europe - prevalence from 1.7% to 8.7%'.
 * England - from 3% in 1989 to 34% in 1998.
 * Measures - isolation and compliance with a hygiene and epidemiological regime, including hand washing.

MRSA resistance in the Czech Republic

 * Exact figures are not available;
 * 70 hospitals have investigated invasive isolates under the EARSS (European Antimicrobial Resistance Surveillance System) project;
 * MRSA incidence - 3.8% in 2000 increased to 8.8% in 2004.

Resistance is caused by

 * The production of bacterial enzymes' that disrupt or modify the structure of the ATB;
 * Alteration of the bacterial wall' - reduction of its permeability;
 * modification of the target sites of ATBs;
 * increased excretion of ATB from bacterial cells to prevent its intracellular accumulation.

Suppression of nosocomial infections

 * Knowledge of all data and information on the emergence and spread of NN is a prerequisite;
 * Data collection is integrated into the "Surveillance" programme;
 * Decree 195/2005 Coll. - lists infectious diseases for which isolation in inpatient facilities is ordered and treatment is mandatory;
 * Act on the Protection of Public Health and on Amendments to Certain Related Acts - 258/2000 Coll., last amended - Act No. 274/2003 Coll.

Repressive measures

 * Tasks:
 * eradication of an outbreak of an already established disease;
 * reporting of an outbreak of NI;
 * treatment of a patient with NI, isolation;
 * barrier nursing care;
 * search for contacts and source of infection;
 * disinfection - in the outbreak area;
 * increasing the immunity of susceptible patients;
 * control of the measures ordered, including thorough documentation.

Nosocomial urinary tract infections

 * Account for 30-40% of UTIs;
 * 60-90% - association with indwelling urinary catheter;
 * 10% - urological-endoscopic intervention;
 * Less costly NI, but prolonged hospitalization increases cost of treatment.

Surgical site infection

 * Third most common NI - 14-20% CDC:


 * superficial IMCHV;
 * deep incisional IMCHV;
 * Organ/space IMCHV.

Clinical picture of IMCHV

 * Redness,
 * serous secretions;
 * purulent secretion from a small area of the wound;
 * purulent secretion from the whole wound area, eventually its disintegration - dehiscence.

Prevention in the preoperative period

 * The shortest possible hospitalization before surgery;
 * Thorough bath and shower;
 * for elective procedures, overtreat other infections;
 * attention to shaving the surgical site;
 * antibiotic prophylaxis.

Intraoperative prophylaxis

 * Principles of asepsis and barrier nursing techniques;
 * use of protective equipment by theatre staff;
 * disposable drapes;
 * disinfection of the surgical field site with proper exposure to disinfectant;
 * precise surgical technique;
 * minimizing the number of staff in the operating room;
 * efficient ventilation and air conditioning in the operating room.

Postoperative interventions

 * Cover the incision with a sterile dressing for 24-48 hours;
 * principles of asepsis during dressings;
 * Educate family and patient about proper wound care and symptoms of wound infection.

Respiratory tract - pneumonia

 * 10-20% of all nosocomial infections;
 * incidence in ICUs can be as high as 65% with mortalitys above 25%;
 * prolong hospitalization;
 * persons at risk are over 70 years of age.

Specific risk factors

 * Internal- age, smoking, alcoholism, malnutrition, obesity, lung disease, severe general illness, and microbial flora of the oropharynx.
 * External - length of hospitalization, immunosuppression, drug administration, thoracic and abdominal surgery, tracheotomy, ET, bronchoscopy, ventilators, nebulizers.

Prevention:

 * maintaining proper personal hygiene and hand washing
 * sterilisation of hospital equipment
 * providing clean and sanitary environment
 * existence of infection control team
 * regular,close observation of high-risk units .e.g intensive care
 * development of policies on areas such as isolation,disinfection and antibiotic usage

Treatment:

 * remove source of microorganism e.g. catheter or iv line
 * some microorganisms involved are-S.aureus,P.aeruginosa,E.coli,Legionella,C.difficile,Klebsiella etc
 * broad spectrum antibiotics such as penicillins are the drugs of choice in most cases except multiresistant infections caused by multiresistant gram negative bacilli (e.g Pseudomonas,Acinetobacter)-sensitive to synergistic action of a combination of beta lactams and aminoglycosides.MRSA- sensitive to co-trimoxazole,tetracyclines,clindamycin.Vancomycin-resistant enterococci- streptogrammins are effective