in hospital epidemiology and infection control

Chapter 32 Role of The Clinical

Microbiology Laboratory in Hospital Epidemiology and

Infection Control

Hui Wang

IN HOSPITAL EPIDEMIOLOGY AND INFECTION CONTROL

Nosocomial infection : acquired in a hospital or healthcare facility an onset of symptom more than 48 hours

after admission (shorter hospital stays)

(eg. surgical wound infections ) may not be recognized until after discharge

(postdischarge surveillance )

EPIDEMIOLOGY CHARACTERISTICS OF NOSOCOMIAL INFECTIONS(1)

Main Infection Sites (5% to 10% of inpatients) UTI: urinary tract 35% to 40% SSI: surgical wound infections 20% LRI: lower respiratory tract 15% BSI: bloodstream infections 5% to 10%

Devices related: various catheters, tubes, etc.Device days —risk adjustment of nosocomial infection

rates (ICU)


Predominant Pathogens



NNIS :ICU

Jan 1986-Apr 1997 Infection Site Pathogen Percentag

e

Bloodstream CoNS 33.5

S. aureus 13.4

Enterococcus spp.

12.8

C. albicans 5.8

Enterobacter spp. 5.2

Pneumonia P. aeruginosa 17.4

S. aureus 17.4


K. pneumoniae 6.7

H. influenzae 4.9

Infection Site Pathogen Percentage

Surgical Site Enterococcus spp.

15.3

CoNS 12.6

S. aureus 11.2

P. aeruginosa 10.3


Urinary Tract

E. coli 19.2

C. albicans 14.4

Enterococcus spp.

14.1

P. aeruginosa 11.2

K. pneumoniae 5.8


NNIS :ICU

Jan 1986-Apr 1997



NNIS, ICU, HA-Candidemia, 1989-1999

The Hospital Infection Control Program surveillance of nosocomial infections continuing education of medical staff control of infectious diseases outbreaks protection of employees from infection advice on new products and procedures timely feedback of infection rates suggestions for improvement and reemphasis of

existing infection control practices


The Hospital Infection Control Program Device days — risk adjustment of nosocomial

infection rates (ICU)• CAUTI: urinary catheter-associated urinary tract

infection• CLAB: central line-associated bloodstream infection• VAP: ventilator-associated pneumonia


The Hospital Infection Control Program Surveillance -- essential • Limited resources focused in the highest risk areas

(ICUs, hematology-oncology, burn units, organ transplant wards)

• various screens :

microbiology reports, nursing care plans, antibiotic orders, and discharge diagnoses


The Hospital Infection Control Program Review of microbiology reports ward-based, laboratory-based linking data from• pharmacy (antimicrobial use) • laboratory • Radiology• billing (diagnostic codesnursing notes (temperature

charts, care plans)


The Hospital Infection Control Program sensitivity and specificity • frequency of culturing • quality of the specimens

Optimal surveillance a combination of all the above data charts deserve further review


MICROBIOLOGY TESTING IN NOSOCOMIAL INFECTION(1)

Specimens Collection

nosocomial pathogens

colonizing organisms

colonizing organisms

Specimens Collection inappropriate specimens • wrong transport media • leaking containers • undue delay from collection to transport

accurate, least misleading microbiological data • monitoring of specimen quality • enforcement of strict criteria for acceptance

MICROBIOLOGY TESTING IN NOSOCOMIAL INFECTION (2)


Accurate Identification of Nosocomial Pathogens capability to identify microorganisms to species level • Conventional identification methods• automated commercial systems • unusual nosocomial pathogens: send to a reference

laboratory


Accurate Identification of Nosocomial Pathogens


Antimicrobial Susceptibility Testing macro- and microbroth dilution method


Antimicrobial Susceptibility Testing agar dilution method


Antimicrobial Susceptibility Testing disk diffusion method


Antimicrobial Susceptibility Testing Etest


Antimicrobial Susceptibility Testing automated commercial systems

short (3- to 5-hour) incubation periods

significant AST errors

( ESBL-producing Enterobacteriaceae, MRS, VRE, VRSA, false resistance )

• Supplement with additional methods• keep up with current literature regarding the

ability of automated systems

Resistance Patterns Testing extended-spectrum β-lactamases (ESBL) stably derepressed Bush-Jacoby-Medeiros group 1

cephalosporinases among Enterobacteriaceae glycopeptide resistance among enterococci and

staphylococci penicillin resistance among S. pneumoniae and

viridans-group streptococci


Reporting of Laboratory Data direct communication between laboratory and

infection control personnel a weekly “work rounds”: • discuss areas of mutual concern • supplementary studies (molecular typing,

environmental cultures, etc.) an early phone call


Reporting of Laboratory Data an early phone call• positive blood or normally sterile site cultures • smears or cultures positive for acid-fast bacilli (AFB) • isolation of Salmonella or Shigella • isolation of MRSA, VRE, etc.• detection of new or unusual pathogens (e.g., Legionella spp., vancomycin-resistant Gram-

positive organisms)


Reporting of Laboratory Data a computer database facilitating retrieval and analysis • specimen type date of collection• patient identification hospital number• hospital service ward location• organisms identified specialized testing • antimicrobial susceptibility test results

establishing a baseline for nosocomial infection rates


Reporting of Laboratory Data Summary antibiogram • frequency of isolation of nosocomial pathogens

by anatomical site

by hospital service • empiric antimicrobial therapy


Organism Storage isolates from normally sterile sites important antibiotic-resistant organisms from any site

(MRSA, VRE, ESBL-producing Enterobacteriaceae) epidemiologically important pathogens (e.g., M.

Tuberculosis)

3 to 5 years


OUTBREAK RECOGNITION AND INVESTIGATION (1)

infection control committee • detects an outbreak of nosocomial infection• define the extent of the outbreak • learn the mode of transmission • institute appropriate control measures

clinical microbiology laboratory: support

Communication

infection control practitioners

& Laboratory personnel• outbreak types in the past• laboratory resources required in the future• extra costs


Problem 1: the number of cases necessary to constitute an outbreak

• organism• patient population• institution

Problem 2: pseudo-outbreak • misdiagnosis • misinterpretation of epidemiologic data


Quality control problems • contamination of strain preparation reagents • false antimicrobial susceptibility test results • culture specimen contamination

Resolvent• Care attention to quality control • sterile technique • construction controls


MOLECULAR TYPING IN THE OUTBREAKING SETTING (1)

hospital epidemiology • clinical setting • species identification an epidemiologic link • Antibiogram

phenotypic typing methods • AST• biochemical profiles • bacteriophage susceptibility patterns • multilocus enzyme electrophoresis profiles

epidemiologic objectives • etermination of the source and extent • the mode of transmission • efficacy of preventative measures • monitoring of infection in high risk areas

genotypic typing methods

MOLECULAR TYPING IN THE OUTBREAKING SETTING(2)


genotypic typing methods Plasmid fingerprinting


genotypic typing methods Restriction endonuclease analysis of chromosomal

DNA with conventional electrophoresis

MOLECULAR TYPING IN THE OUTBREAKING SETTING (5)

genotypic typing methods

Restriction-fragment length polymorphism (RFLP) analysis with nucleic acid probes


genotypic typing methods Pulsed-field gel electrophoresis


genotypic typing methods Polymerase chain reaction (e.g., RAPD, rep-PCR,

CFLP, AFLP)

CULTRUES OF HOSPITAL PERSONNEL AND ENVIRONMENT (1)

Only when involvement in transmission of a nosocomail pathogen.

• Blood products• Parenteral fluids and intravenous devices • Environmental surfaces • Tubes and containers • Disinfectants and Antiseptics

• Respiratory therapy equipment• Air • Water and ice • Hands of personnel • Anterior nares of personnel

hand of healthcare workers • an important vehicle for transmission • confirming the mechanism of cross-infection • Culture method: broth-bag technique

anterior nares • usual reservoir for S. aureus (including MRSA)

colonization


Result interpretation finding the outbreak strain

does not establish the direction of transmission or definitively implicate the health care worker as the source or reservoir for the outbreak

Indiscriminate culturing confusing results ill will toward the infection control program

CULTRUES OF HOSPITAL PERSONNEL AND ENVIRONMENT(3)

routine monitoring • sterilization • infant formula • other hospital-prepared products • blood components prepared in an “open” system • hemodialysis fluid • disinfected equipment

Others should not be performed.


CONCLUSION

Clinical microbiology laboratory --an essential component

Ongoing cooperation and collaboration between the laboratory and the infection–control personnel

Appropriate application of the newer methods for detection, identification, and typing of nosocomial pathogens

in hospital epidemiology and infection control

Documents

infection advice

admission shorter hospital

review microbiology

bloodstream infections

surgical wound infections

data charts

specimens optimal surveillance

urinary tract infectionclab