Hospital Acquired infections, also called nosocomial infections can be defined as the infections acquired by the patients in the hospital by a patient - 1. who was admitted for a reason other than that infection. 2. In whom infection was not present or incubated at the time of admission. 3. Symptoms should appear at least after 48 hours of admission. In these slides, microbes responsible for hospital acquired infections and preventive strategies are shared. 

1. Manita Paneri
PhD Scholar
Medical Microbiology
The Role of Microorganisms in Hospital Acquired Infections

2. overview
Hospital Acquired Infection
Factors affecting Hospital Acquired Infection
Sources of Infection
Microorganism involved in Hospital Acquired Infection
Modes of Transmission
Types of Hospital Acquired Infections
Prevention
Hospital Infection Control Committee
Functions of HICC

3. Definition:
• Hospital acquired infections also called nosocomial infections can be defined as the
infections acquired in the hospital by a patient:
• Who was admitted for a reason other than that infection
• In whom infection was not present or incubated at the time of admission
• Symptoms should appear at least after 48 hours of admission
• This include infections acquired in the hospital after discharge and also occupational
infections among staff of the hospital care facility.

4. Factors affecting Hospital Acquired Infections
Immune
status
Hospital
environment
Diagnostic or
therapeutic
interventions
Transfusions
Poor hospital
administration

5. Sources of
Infections
Exogenous
Environmental
Sources Health care
workers
Other Patients
Endogenous
Patient’s own
microbial Flora

6. Microorganisms involved in Hospital Acquired Infection
Enterococcus Faecium Staphylococcus aureus Klebsiella pneumoniae
• Acinetobacter baumannii Pseudomonas aeruginosa Enterobacter species

7. Enterococcus faecium
• It is Gram-positive, spherical shaped(coccus) opportunistic
bacteria.
• It can be commensal in the gastrointestinal tract of
humans and the animals.
• But it can be also pathogenic, causing diseases such as
neonatal meningitis or endocarditis.
• It has developed multidrug antibiotic resistance .
• The enterococcal surface protein allows the bacteria to
aggregate and form biofilms.

8. Staphylococcus aureus
• It is a Gram-positive, rounded shape opportunistic
bacteria.
• It is frequently found in the upper respiratory tract and on
the skin.
• It is also facultative anaerobes.
• It causes skin infections including abscesses, respiratory
infections such as sinusitis and food poisoning.
• The emergence of antibiotic resistance S. aureus is a
worldwide problem in clinical medicine.

9. Klebsiella pneumoniae
• It is a Gram-negative, non motile, encapsulated, facultative
anaerobic, rod shaped bacterium.
• It is found in the normal flora of the mouth, skin and intestine.
• In addition to pneumonia, Klebsiella can also cause urinary
tract infection, wound infection, meningitis, bacteraemia,
sepsis and cholecystitis.
• patients with invasive devises in their bodies, neonatal ward
devices, respiratory support equipment and urinary catheters,
the use of antibiotics can be a factor that increases the risk of
nosocomial infection.

10. Acinetobacter baumannii
• It is typically short, almost round, rod shaped Gram negative
bacterium.
• It can be an opportunistic pathogen in humans, affecting people
with compromised immune systems.
• A. baumannii been noted for its apparent ability to survive on
artificial surfaces for an extended period of time, therefore
allowing it to persist in the hospital environment.
• This is due to the its ability to form biofilms.
• It causes Pneumonia, bloodstream infections, meningitis, urinary
tract infections and wound and surgical infections.

11. Pseudomonas aeruginosa
• It is a common encapsulated , Gram-negative, rod shaped
bacterium.
• It is a facultative anaerobe as it is well adapted to proliferate
in conditions of partial or total oxygen depletion.
• It is found in soil, water, skin flora.
• It is a multidrug resistant pathogen, recognised for its ubiquity
and its association with serious illnesses like ventilator-
associated pneumonia and various sepsis syndromes.

12. Enterobacter species
• It is Gram negative, facultative anaerobe, rod shaped bacteria.
• Several strains of these bacteria pathogenic and cause
opportunistic infections in immunocompromised hosts and in
those who are on mechanical ventilation.
• The urinary and respiratory tract are the most common sites of
infection.
• The study concludes that Enterobacter cloacae may contribute
to obesity in its human hosts through an endotoxin-induced,
inflammation-mediated mechanism.

13. Other Microorganisms that can caused Hospital acquired Infections
E coli Mycobacterium
Tuberculosis
Candida albicans Clostridium difficile

14. Characteristics of ESKAPE pathogens
 Porin mediated
 Overexpression of efflux pump
 Plasmids with antibiotic resistance
genes
 Mutation
 Antibiotic-modifying enzyme
 Antibiotic hydrolysing enzyme

15. Modes of transmission of hospital acquired pathogen
Contact transmission Inhalation mode
Vector borne transmission Common Vehicle transmission
Mode of
Transmission

16. Direct contact transmission
• This is most common mode of transmission.
• Skin to Skin contact and thereby physically transfer of
microorganisms between a susceptible host and an infected
or colonized person .
• Usually involves health care workers rarely other patients.

17. Indirect contact transmission
It involves contact of susceptible host with contaminated
inanimate objects such as :
• Dressings or gloves, instruments (e.g. stethoscope)
• Parenteral transmission through : Needle, splashes of blood
or body fluids, contaminated saline flush, syringes, vials and
bags

18. Inhalation mode

19. Vector borne Transmission
It occurs via vectors such as mosquitoes, flies etc.
carrying the microorganisms.
This is rare mode of transmission in the hospital.

20. Common Vehicle Transmission

21. Types of Hospital Acquired Infection
Urinary Tract
Infections Pneumonia
Surgical site
Infections
Blood Stream
Infections

22. Urinary Tract Infections
Organisms:
1. E. coli
2. Klebsiella pneumoniae
3. Proteus mirabilis
4. Enterococcus faecalis
5. Staphylococcus saprophyticus
Risk factors:
1. Advanced age
2. Female gender
3. Severe underlying disease
4. Placement of a urinary catheter

23. Pneumonia
Lung infections are major cause of HAIs after UTI.
Microorganisms:
1. Streptococcus Pneumoniae
2. Gram-negative bacteria and Streptococcus aureus
3. Klebsiella pneumoniae
4. Enterobacter spp.
5. Haemophilus influenzae
Risk Factor:
1. Advanced age
2. Chronic lung disease
3. Aspiration of upper respiratory tract secretion into
the lungs
4. Semiconscious patient
5. Chest surgeries
6. Mechanical ventilation through intubation of
endotracheal tube

24. Surgical Site Infections
Microorganisms:
1. Staphylococcus aureus
2. Escherichia coli
3. Pseudomonas aeruginosa
4. Streptococcus and Enterococcus spp.
Risk Factors:
1. Advanced age, obesity, malnutrition, Diabetes etc.
2. Infections at a remote site that spread through the blood
stream
3. Time interval between pre-operative shaving of the site
and the surgery exceeds more than 12 hours
4. Inappropriate timing of prophylactic antimicrobial agent

25. Blood stream infections
Microorganisms:
1. Coagulase negative staphylococci
2. Streptococcus aureus
3. Enterococci
4. Candida
5. Gram-negative bacteria
Risk factors:
1. Age less than 1 year and more than 60 years and
malnutrition
2. Low immunity or severe underlying disease
3. Loss of skin integrity (burn or bed sore)
4. Prolonged hospital stay, especially in ICUs
5. Presence of intravascular catheters

26. Gram negative bacilli
65%
Gram-positive cocci
30%
Yeast
5%
HOSPITALACQUIRED INFECTIONS IN THE TERTIARY
CARE HOSPITAL, MUMBAI(MAHARASHTRA)
Gram negative bacilli
Gram-positive cocci
Yeast

27. Klebsiella pneumoniae,
19%
E. coli, 17%
Psudomonas aeuruginosa,
13%
Staphylococcus aureus,
12%
Enterococcus sp., 10%
Enterobacter sp., 4%
Acinetobacter baumannii,
5%
other GNB, 6%
Coagulase negative
Stapylococcus sp., 7%
Streptococcus sp., 2%
Candida , 5%
HOSPITALACQUIRED INFECTIONS IN THE TERTIARY
CARE HOSPITAL, MUMBAI (MAHARASHTRA)

28. Prevention of HAIs
Standard
Precautions
Specific
Precautions

29. Standard
Precautions
Hand
hygiene
Personal
protective
Equipment
Waste
handling
Spillage
cleaning
Disinfection
Sharp
Handling

30. Standard Precautions:
Standard precautions are a set of infection control practices used to prevent transmission of
diseases that can be acquired by contact with blood, body fluids, non-intact skin and mucous
membranes.
They are indicated while handling all patients, specimens and sharps. Component of standard
precautions include:
Hand hygiene:
• Wash hands properly after contact with infective material
• Use no touch technique wherever possible

31. Hand washing Technique with soap and water

32. Personal protective Equipment:
• Wear gloves, when excepting contact with blood, body fluids, secretions, excretions, mucous
membrane and contaminated items and wash hands immediately after removing gloves.
Sharp Handling:
• All sharps should be handled with extreme care.
Spillage cleaning:
• Clean up spills of infective material promptly.
Disinfection:
• Ensure that patient care equipment, supplies and linen contaminated with infective material are
either discarded, or sterilized between each patient use.
Waste handling:
• Ensure appropriate biomedical waste segregation and disposal .

33. Specific
Precautions
Contact
Precautions
Droplet
Precautions
Precautions
for patients
with
MDROs
Airborne
Precautions

34. Specific Precautions:
Additional precautions are needed for preventing specific modes of transmission.
It includes:
Airborne Precautions
The following measures are required :
• Individual room should be provided with adequate ventilation with negative pressure facility.
• Staff should wear high-efficiency masks in the room.
• Patient should be confined to the room.
Droplet Precautions:
The following procedures are required:
• Individual room for the patient, if available.
• Mask for health care workers.
• Restricted movement of the patient; patient should wears a surgical mask while leaving the room.

35. Contact Precautions
These are required for the patients with Diarrhoea and Enteric infections or skin lesions.
• Individual room for the patient if available; cohorting of patient if possible.
• Staff should wear gloves and gowns on entering the room.
• Hand washing should be done before and after contact with the patient, and on leaving the room.
• Appropriate environmental and equipment cleaning, disinfection and sterilization to be followed.
Precautions for patients with MDROs
• Minimize ward transfer of staff and patients.
• Ensure early detection of cases especially if admitted from another hospital; screening of high risk
patients may be required.
• Isolation of infected or colonized patients is required.
• Reinforce hand washing by staff after contact with infected or colonized patients.
• Ensure careful handling and disposal of medical devices, linen, waste etc.

36. HOSPITAL INFECTION CONTROL COMMIITEE (HICC CONSTITUTION)
1. Chairperson, usually the Medical Superintendent
2. Secretary, usually the head of department of microbiology
3. Hospital Infection Control Officer (HICO), usually a representative from the department of microbiology
4. Hospital Infection Control Nurses (HICN)
5. Head of all the clinical (medical and surgical) departments
6. Nursing Superintendent
7. Head of the Staff clinic
8. Operation Room Supervisor
9. In-charge of Central Sterile Supplies Department (SSD)
10. In-charge of Pharmacy
11. In-charge of hospital linen
12. In-charge of hospital laundry
13. In-charge of hospital kitchen
14. Epidemiologist
15. In-charge of engineering department of hospital

37. 1. HAI surveillance
2. Develop a system
3. Antibiotics usage
4. Policies
5. Education
6. Staff health
7. Outbreak management
8. Other departments
9. Reviews risk
10. HICC Meetings
Functions of the HICC

38. Functions of the HICC
HAI surveillance:
The four key parameters used for HAI surveillance are as follows:
1. CA-UTI (Catheter associated urinary tract infection)
2. CLABSI (Central line associated bloodstream infection)
3. VAP (Ventilator associated pneumonia)
4. SSI(surgical site infection)
Develop a system for identifying , reporting, analyzing, investigating and controlling hospital
acquired infections.

39. Antibiotics usage:
Develop antibiotic policies, monitors the antibiotic usage, advices the MS on matters related to the
proper use of antibiotics and also recommends remedial measures when antibiotics resistant strains
are detected.
Policies:
Reviews and updates hospital infection control policies and procedures from time to time.
Education:
Conducts teaching sessions for healthcare workers regarding matters related to HIAs.
Staff health:
Monitors employee health activities regarding matters related to HIAs such as Hepatitis B
vaccination etc.

40. Outbreak management:
Develops strategies to identify infectious outbreaks, their sources and implements preventive
and corrective measures.
Other departments:
Communicates and cooperates with other departments of the hospital.
Reviews risk associated with new technologies and monitor infectious risks of the new devices
and products, prior to their approval for use.
HICC Meetings:
• Shall meet regularly not less than once a month and as often as required.
• However, in an emergency this committee must be able to meet promptly.

41. References:
1. Shah, S., Singhal, T., Naik, R., & Thakkar, P. (2020). Predominance of multidrug-resistant Gram-
negative organisms as cause of surgical site infections at a private tertiary care hospital in Mumbai,
India. Indian Journal of Medical Microbiology, 38(3-4), 344-350.
2. D’Accolti, M., Soffritti, I., Mazzacane, S., & Caselli, E. (2019). Fighting AMR in the healthcare
environment: Microbiome-based sanitation approaches and monitoring tools. International journal of
molecular sciences, 20(7), 1535.
3. Gomila, A., Carratalà, J., Eliakim-Raz, N., Shaw, E., Wiegand, I., Vallejo-Torres, L., & Pujol, M.
(2018). Risk factors and prognosis of complicated urinary tract infections caused by Pseudomonas
aeruginosa in hospitalized patients: a retrospective multicenter cohort study. Infection and drug
resistance, 11, 2571-2581.
4. Singhal, T., Shah, S., Thakkar, P., & Naik, R. (2019). The incidence, aetiology and antimicrobial
susceptibility of central line-associated bloodstream infections in intensive care unit patients at a private
tertiary care hospital in Mumbai, India. Indian Journal of Medical Microbiology, 37(4), 521-526.
5. Seyedeh Marzieh, J. S., Pormohammad, A., Hashemi, A., & Lak, P. (2019). Global prevalence of
antibiotic resistance in blood-isolated Enterococcus faecalis and Enterococcus faecium: A systematic
review and meta-analysis. Infection and Drug Resistance, 12, 2713-2725.
6. Sastry, S. A., & Bhat, S. (2021). Essentials of Medical Microbiology. Macmillan Publishers.