Antibiograms constructed using standardized methods like CLSI guidelines allow for inter- and intra-hospital comparisons and help guide empiric antimicrobial treatment. However, antibiograms that include surveillance cultures or duplicate bacterial isolates can overestimate resistance rates. Laboratories should report bacterial isolates as either sensitive or resistant according to CLSI protocols, rather than using qualitative terms, in order to accurately inform clinicians' treatment decisions while avoiding increased emergence of drug resistance.

1. SCIENTIFIC UTILITY OF ANTIBIOGRAMS
(By disc diffusion method)
Dr.T.V.Rao MD
Hospital Antibiograms are commonly used to help guide empiric antimicrobial treatment and are an
important component of detecting and monitoring trends in antimicrobial resistance. To serve these
purposes, antibiogram must be constructed using standardized methods as many laboratories take the
advantage of CLSI guidelines that allow inter- and intra-hospital comparisons. Antibiogram that include
surveillance cultures and duplicate bacterial isolates can overestimate rates of resistance. In 2002, the
National Committee for Clinical Laboratory Standards (now known as the Clinical and Laboratory
Standards Institute [CLSI]) published standards for constructing antibiogram. According to national
surveys, many of the recommended elements of the CLSI document have not been fully adopted. If you
are using the WHONET software and the guidelines for measuring the Zone sizes, can be updated as
per the newer protocols of CLSI guidelines, as they updated every years, however many of us follow the
previous years as they involve with costs of buying the soft ware of updated protocols. Antibiogram have
several limitations, such as their inability to track emergence of resistance during therapy. The
antibiogram can serve as a valuable tool in guiding antimicrobial therapy, but other patient factors, such
as previous infection history and antibiotic use, also need to be considered. Additional data are needed
for specialized applications of resistance analyses. Hospitals are implementing antimicrobial
stewardship programs (ASPs) in response to national guidelines to improve the use and to extend the
utility of anti-infective drugs. An often-implied purpose of ASPs is to curb or reverse the emergence of
resistant bacteria. Because antibiotic use causes antibiotic resistance, there is a natural tendency to link
local measures of antibiotic use to local measures of bacterial resistance, and the hospital antibiogram
is a readily available measure of resistance
IMPORTANT CONCERNS – All laboratories should recognize and practice The laboratories should
report whether a Bacterial isolate is Sensitive (S) or Resistant R Rarely as Moderately sensitive (MS) to
be used as per the standard guidelines of the CLSI protocols and should be not be used loosely in view
exact determination with Minimal inhibitory concentration, many of use are doing
IT IS A GRAVE DANGER IF 1 THE LABORATORIES REPORT AS STRONGLY SENSITIVE
(+++++) AND WEAKLY SENSITIVE (++) OR 2 EXPRESS THE ZONE SIZES AS 23 mm OR
28 mm IT MAKES THE CLINICIANS TO THINK THE ANTIBIOTIC SHOWING +++++ is
more effective than ++ or 28 mm IS MORE EFFECTIVE THAN 23mm AS THE
ANTIBIOGRAMS ARE FORMULATED WITH ZONE SIZES IN RELATION TO
PARTICULAR ANTIBIOTIC and NATURE OF ISOLATE AND DEFINITELY ON ZONE
SIZES,
I wish that the Microbiologists should convey to the clinicians only limited
number or specified group of drugs to be tested on any particular isolate
IMPORTANT - WE ARE OBSERVING MANY LABORATORIES IN PRIVATE AND
PUBLIC INSTITUTES WHICH HAVE NO POLICY WHAT TO TEST FOR WHAT
BACTERIAL ISOLATED ARE PLAYING TO THE IGNORANCE OF CLINICIANS, AND
MICROBIOLOGISTS. HOWEVER IT WILL BE A GREAT THREAT TO MANY PATIENTS IN
CRITICAL CARE AREAS AND INCREASES THE DRUG RESISTANCE AND CREATES
SUPERBUGS IN MANY AREAS IN THE HOSPITAL ENVIRON MENT
DR.T.V.RAO MD PROFESSOR OF MICROBIOLOGY FREELANCE WRITER