3. Antibiotic resistance is the ability of bacteria to resist
the effects of an antibiotic – that is, the bacteria are not
killed, and their growth is not stopped
It is a natural phenomenon accelerated by use of
antibiotics. Resistant strains survive and aggregate
4. “The time may come when penicillin can be bought by
anyone in the shops. Then there is the danger that the
ignorant man may easily underdose himself and by
exposing his microbes to non-lethal quantities of the
drug make them resistant.”
- Alexander Fleming
‘Penicillin’ Nobel Lecture, December 11, 1945
7. • Non-susceptibility to at least one agent in
three or more antimicrobial categories
Multidrug- resistant
(MDR) bacteria
• Non-susceptibility to at least one agent
in all but two or fewer antimicrobial
categories
Extensively drug-
resistant (XDR) bacteria
• Non-susceptibility to all agents in all
antimicrobial categories
Pandrug-resistant (PDR)
bacteria
Non-susceptibility refers to either a resistant, intermediate or non-
susceptible result obtained from in vitro antimicrobial susceptibility testing
9. MDR-TB
Beijing strain responsible for majority of cases
Drug resistance acquired through genetic mutations;
cannot be transmitted to other bacteria via plasmids
10. Detection of decreased susceptibility to 3rd generation cephalosporin and
treatment failures
Neisseria gonorrhoeae
12. Antibiotics are given to
food producing animals
and crops
Animals develop drug-
resistant bacteria in their gut
Drug-resistant bacteria reaches
humans through food, the
environment (water, soil, air) or by
direct human-animal contact
Antibiotics are given to patients,
which can result in drug-resistant
bacteria developing in the gut
Patient attends
hospital/clinic
Drug-resistant bacteria spreads
to other patients through poor
hygiene and unclean facilities
Drug-resistant bacteria
spreads to the general
public
17. Why do bacteria become resistant to antibiotics to
which they were earlier susceptible?
Bacteria have to adapt and evolve to survive as the
environmental conditions change
Genetic variability
Antibiotic
resistance
Acquired Resistance
Antimicrobial agents exert strong selective pressures on
bacterial populations, favouring organisms that are capable of
resisting them
20. Point mutations
Spontaneous
Replacement of only one base pair in the DNA structure
Preserved due to “selection pressures” exerted by antibiotics
Resistance is of low level, to a single drug
The trait is passed vertically to daughter cells; termed as
“vertical transfer”; cannot be transferred to other bacterial
species
E.g. Resistance of M. tuberculosis to rifampicin due to
mutation in the rpoB gene which encodes the beta subunit
of the bacteria's RNA polymerase
21. External Acquisition of Genetic elements
Drug resistance acquired by horizontal transfer of resistance
determinant genes from a donor cell
This transfer can occur between bacteria of the same species or of
different species
Mobile genetic
elements
1.Plasmids
1.Bacteriophag
es
Specialized genetic
elements
1.Transposons
1.Integrons
1.Transformati
on
Transduction
Conjugation
GENETIC ELEMENTS PROCESSES
22. Conjugative
plasmids
Extrachromosomal, autonomously replicating agents of
genetic exchange, present in cytoplasm
Consist of covalently closed, circular, double-stranded DNA
molecules
Plasmids that carry resistance genes are called R-plasmids
R-genes are readily transferred from R-plasmid to another
plasmid or chromosome
23. Transposons
Short segments of DNA with their
own recombination enzyme,
transposase
Translocate as a unit from one area
of the bacterial chromosome to
another or plasmid or
bacteriophage DNA
May transpose to nonhomologous
sequences of DNA
Must exist on a replicon (plasmid
or bacteriophage) to be replicated
Integrons
Integrase - Receptor for resistance
gene cassettes
Promoters - Initiation site for their
transcription
Cannot promote self-transfer
“Hot-spots” for site-specific
recombination events between
nonhomologous sequences of DNA
Located on a transposon or a
conjugative plasmid
24. Conjugation
Common mechanism of resistance transfer among Gr –
ve bacilli present in high density in the gut
Resident nonpathogenic microflora serve as a reservoir
for the resistant genes which can be transferred to other
organisms that invade the host
• Eg. Chloramphenicol resistance of typhoid bacilli
• Streptomycin resistance of E. coli
• Penicillin resistance of Hemophilus and Gonococci
25. Transduction
Plasmid DNA enclosed in a
bacteriophage is transferred to
another bacterium of the same
species
Transformation
Resistant bacterium releases the
resistance carrying DNA into the
medium
Certain bacteria pick up free
homologous DNA from the
environment
New DNA is then incorporated into
the genome of the bacteria which
then becomes resistant
Strains of Staph aureus
Penicillin resistance in Pneumococci and Neisseria
26. Mechanisms of antibiotic resistance
1. Enzymatic modification
2. Decreased Permeability of Bacterial Membranes
3. Promotion of Antibiotic Efflux
4. Altered Target Sites
5. Overproduction of Target
6. Bypass of Antibiotic Inhibition
27. 1. Enzymatic modification
ß-lactamases inactivate β-lactam antibiotics by splitting the
amide bond of the ß-lactam ring
β-lactamase
β-lactamase Bacterial species Hydrolyze
Penicillinase E. coli, S. aureus Penicillin
TEM-1 (Temoniera),
SHV-1
(Sulfhydryl variable-1)
Enterobacteriaceae,
P. aeruginosa, H.
influenzae, and N.
gonorrhoeae
Penicillins and
narrow-spectrum
cephalosporins
28. Extended Spectrum
β-lactamase
Bacterial species Hydrolyze Susceptibility to β-
lactamase inhibitor
TEM-3 Enterobacteriaceae Third-generation
cephalosporins,
aztreonam
Susceptible to
clavulanic acid
CTX-M
(Cefotaxime-M)
E. coli Third-generation
cephalosporins
Susceptible to
tazobactam
OXA
(Oxacillin)
P. aeruginosa Oxymino-β-lactams Poorly inhibited by
clavulanic acid
Carbapenemase K. pneumoniae Carbapenems -
New Delhi metallo-
β-lactamase
K. pneumoniae All β-lactams except
aztreonam
Resistant to
clavulanic acid,
tazobactam and
sulbactam
Aminoglycoside-modifying enzymes confer antibiotic resistance through three
general reactions: N-acetylation , O-nucleotidylation, and O-phosphorylation
29. 2. Decreased Permeability of Bacterial Membranes
Emergence of imipenem resistance during therapy, observed
in up to 25% of P. aeruginosa infections has been ascribed to
mutational loss of its OprD protein aka the D2 porin
30. 3. Promotion of Antibiotic Efflux
Bacteria can overexpress efflux pumps and then expel antibiotics to
which the bacteria would otherwise be susceptibleAntibiotics
Efflux
pumps
Bacterial species Gene designation Resistant against
Streptococcus
pneumoniae
mef (macrolide
efflux)
Macrolides
Staphylococcus
aureus
msr (macrolide
streptogramin
resistance)
Macrolides,
Streptogramins
Enteric Gr-ve
bacteria
Tetracycline-
resistance
determinant (Tet)
Tetracyclines
31. Mechanism of MDR among aerobic and anaerobic Gr +ve bacteria for
macrolides, lincosamides, and streptogramin B (MLSB)
Resistance mediated by methylase enzymes, products of the erm
(erythromycin ribosome methylation) gene → dimethylate adenine
residues on the 23S ribosomal RNA (rRNA) of the 50S subunit of the
prokaryotic ribosome, disrupting the binding of MLSB to the ribosome
4.1. Alteration of ribosomal target sites
4.2. Alteration of target enzymes
Mechanism of resistance in narrow-spectrum penicillin
In S. aureus, methicillin resistance is conferred by the expression of the
mecA gene, which encodes PBP2a, a protein with low affinity for β-
lactam antibiotics, conferring resistance to nafcillin, oxacillin and
methicillin
32. 4.3. Alteration of cell wall precursor targets
Mechanism of resistance to vancomycin and teicoplanin in strains of E.
faecium and E. faecalis
vanA gene on the plasmid encodes an inducible protein that is related to
the d-ala-d-ala ligases involved in cell wall synthesis
Synthesizes peptidoglycan precursors that have a depsipeptide terminus
(d-alanine d-lactate) instead of the usual d-ala-d-ala
Modified peptidoglycan binds glycopeptide antibiotics with reduced
affinity, conferring resistance
33. 5. Overproduction of target
Sulfonamides compete with para-
aminobenzoic acid to bind the
enzyme DHPS and halt the
generation of pteridines and nucleic
acids
Sulfonamide resistance is mediated
by the gene felP by the
overproduction of the synthetic
enzyme DHPS
Excess DHPS can overwhelm sulfa
inhibition
6. Bypass of antibiotic inhibition
Auxotrophs are mutants that require
substrates normally synthesized by the
target enzymes
But if the substrates are present in the
environment, the organisms are able to
grow despite inhibition of the synthetic
enzyme
Enterococci can be folate auxotrophs
requiring environmental acquisition of
folic acid for growth
They become intrinsically resistant to
the folic acid inhibitors (sulfa drugs or
trimethoprim) in the process
34. Cross resistance
Acquisition of resistance to one antibiotic conferring resistance to another
antibiotic, to which the bacteria has not been exposed
More common between chemically related drugs
Complete
Resistance to one tetracycline
means insensitivity to others
Partial
Gentamicin-resistant strains may
respond to amikacin
Two-way
Erythromycin and clindamycin
and vice versa
One-way
Enterobacteriaceae resistant to
neomycin will be resistant to
streptomycin, but many other
bacteria resistant to streptomycin
remain susceptible to neomycin
35. Constitutive resistance vs. Inducible resistance
Resistant strains of Gr+ve and Gr-ve bacteria inactivate chloramphenicol
by producing chloramphenicol acetyltransferase
Gr-ve bacteria exhibit five-fold higher resistance compared to Gr+ve
bacteria
In Gr-ve bacteria , the enzyme is present constitutively, i.e. available
even when the substrate drug is absent
In Gr+ve bacteria this enzyme is inducible, synthesized only when the
drug is present even in sub-therapeutic concentrations
The r-genes, usually present on plasmids, are
disposed of when bacteria are in antibiotic-free
media
In presence of repeated environmental antibiotic
exposure, eg. In hospitals and ICUs
37. Measures to combat antibiotic resistance
1. Public awareness and education
2. Antibiotic Stewardship Program
3. Rapid point-of-care diagnostic tests
4. WASH and IPC
5. Development of new antibiotics/Alternatives
39. Antibiotic Stewardship Program: Goals
Optimal treatment with antibiotics
Prevent antimicrobial overuse, misuse, and abuse
Minimize the development of resistance
Secondary goal: Reduce healthcare costs without adversely impacting
quality of care
1.
2.
3.
Right antibiotic
Right dose
Right route
Right time
Right duration
41. Antimicrobial Stewardship Strategies:
Multidisciplinary
Individual instruction by an antibiotic-utilization expert appears to be the
most successful educational strategy, whereas utilization review is less
useful
Continuous reinforcement is necessary
Limiting the availability of agents on formulary - most direct method to
influence antimicrobial utilization
Simple way to prohibit the use of newer, more expensive antibiotics in
favor of older, equally effective drugs
1. Education
2. Antimicrobial Formulary Restriction
42. Certain antibiotic classes or agents have a lower intrinsic risk of
selecting for antimicrobial resistance
Antimicrobial “cycling” ensures homogenous antimicrobial use delaying
emergence of resistance
Justification by prescribers and approval by infectious diseases
physicians to limit the use of systemic antimicrobial agents
Prospective audit of antimicrobial prescribing (usually accomplished by
daily review of prescriptions of targeted antimicrobials), coupled with
feedback to physicians to improve antimicrobial use
Resistance in Pseudomonas spp. was more difficult to achieve with
meropenem than with imipenem because two mutations were required
rather than one
3. Prior Approval and Justification
4. Prospective Audit and Feedback
43. Clinic Hospital
Does the patient have a
bacterial infection?
No
No
antibiotics
Conduct proper microbiological diagnosis
Yes
Interpret results; evaluate AST data
Does the patient have a
bacterial infection?
Initiate prompt empiric
antibiotic therapy
Prescribe/ de-escalate the empiric therapy to a
narrow spectrum antibiotic
Appropriate antibiotic therapy with shortest duration
Is the patient prone to
a bacterial infection?
Optimal antibiotic
for short duration:
Bactericidal
Non-toxic
Inexpensive
Active against
typical pathogens
Prefer monotherapy over combination
Prefer oral dosing over intravenous
administration
Bacteriostatic vs. bactericidal antibiotic
Host factors
Supervise for potential contraindications like
allergies and toxicity
Reassess within 48 hours and adjust antibiotic
if necessary or stop antibiotic if indicated
Ensure patient adherence
46. Infection Prevention & Control
Hand hygiene compliance
Surveillance of infections due to MDROs and surveillance
cultures for asymptomatic MDROs colonization
Contact precautions: gowns, gloves, PPE
Patient isolation: patient cohorting or single room isolation
Environmental cleaning
Multimodal IPC strategies
47. The US National Institutes of Health (NIH), the world’s
largest single funder of health research, allocated just
1.2 percent of its grant funding to AMR-related
research between 2009 and 2014, compared to 18.6
percent (more than five billion USD annually) to cancer
research
Lack of investment in R & D
48.
49. Quorum Sensing Inhibitors (QSIs)
Bacteria communicate with each other and exchange chemical signal
molecules called autoinducers
This process termed as quorum sensing allows bacteria to co-ordinate
gene expression for resistance
Occurs only when the population of bacterial cells reach a critical
density (quorum) with a minimal threshold stimulatory concentration
of an autoinducer
Bacteria Autoinducer
Gr+ve Acylhomoserine lactone (AHL)
Gr-ve Autoinducing peptide (AIP)
Gr+ve and Gr-ve Autoinducer-2 (AI-2)
Synthetic furanones
50. Phage Therapy
Therapeutic use of bacteriophages to treat pathogenic bacterial
infections
Bacteriophages are very specific, targeting only one or a few strains of
bacteria
Harmless to the gut flora, reducing the chances of opportunistic
infections
Especially successful in case of a biofilm covered by a polysaccharide
layer, which antibiotics typically cannot penetrate
Phages currently being used therapeutically to treat bacterial infections
that do not respond to conventional antibiotics in Russia, Georgia and
Poland
In 2007, a Phase 1/2 clinical trial was completed at the Royal National
Throat, Nose and Ear Hospital, London, for P. aeruginosa infections
(chronic otitis)
Phase 1 clinical trial completed in the Southwest Regional Wound
Care Center, Lubbock, Texas for an approved cocktail of phages
against bacteria, including P. aeruginosa, S. aureus and E. coli.
(chronic venous leg ulcers)
51. “Some experts say we are moving back to the pre-
antibiotic era. No. This will be a post-antibiotic era. In
terms of new replacement antibiotics, the pipeline is
virtually dry. A post-antibiotic era means, in effect, an
end to modern medicine as we know it. Things as
common as strep throat or a child's scratched knee
could once again kill.”
- Margaret Chan
Former Director-General, WHO
52. References
Opal SM, Pop-Vicas A. Molecular Mechanisms of Antibiotic Resistance in
Bacteria. In: Bennett JE, Dolin R, Blaser MJ, editors. Mandell, Douglas, and
Bennett’s Principles and Practice of Infectious Diseases. 8th ed. Philadelphia.
Saunders; 2015.
Gumbo T. General Principles of Antimicrobial Therapy. In: Brunton LL, Hilal-
Dandan R, Knollmann BC, editors. Goodman & Gilman’s The Pharmacological
Basis of Therapeutics. 13th ed. New York. The McGraw-Hill Companies, Inc.;
2018.
Satoskar RS, Rege NN, Bhandarkar SD. Pharmacology and
Pharmacotherapeutics. 25th ed. Mumbai: Popular Prakashan Private Limited;
2013. Chapter 51, General Principles of Chemotherapy of Infections; p.718-28.
Tripathi KD. Essentials of Medical Pharmacology. 7th Ed. New Delhi: Jaypee
Brothers Medical Publishers (P) Ltd; 2013. Chapter 49, Antimicrobial Drugs:
General Considerations; p.688-703.
Sharma HL, Sharma KK. Sharma’s & Sharma’s Principles of Pharmacology. 3rd
Ed. New Delhi: Paras Medical Publisher; 2017. Chapter 52, Introduction to
Chemotherapy; p.699-713.
MacDougall C. Antimicrobial Stewardship. In: Bennett JE, Dolin R, Blaser MJ,
editors. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious
Diseases. 8th ed. Philadelphia. Saunders; 2015.
53. References
Magiorakos AP et al. Multidrug-resistant, extensively drug-resistant and
pandrug-resistant bacteria: an international expert proposal for interim standard
definitions for acquired resistance. Clin Microbiol Infect. 2012 Mar;18(3):268-81.
Rice LB. Federal funding for the study of antimicrobial resistance in nosocomial
pathogens: no ESKAPE. J Infect Dis. 2008 Apr 15;197(8):1079-81.
Singhal N, Kumar M, Kanaujia PK, Virdi JS. MALDI-TOF mass spectrometry: an
emerging technology for microbial identification and diagnosis. Front Microbiol.
2015 Aug 5;6:791.
Ling LL, Schneider T, Peoples AJ, Spoering AL, Engels I, Conlon BP, Mueller A,
Schäberle TF, Hughes DE, Epstein S, Jones M, Lazarides L, Steadman VA, Cohen
DR, Felix CR, Fetterman KA, Millett WP, Nitti AG, Zullo AM, Chen C, Lewis K. A
newantibiotic kills pathogens without detectable resistance. Nature. 2015 Jan
22;517(7535):455-9.
https://www.Nobelprize.org/nobel_prizes/medicine/laureates/1945/fleming-lecture.pdf
Discovered the world's first antibiotic substance benzylpenicillin (Penicillin G) from the mould Penicillium notatum in 1928, for which he shared the Nobel Prize in Physiology or Medicine in 1945 with Howard Florey and Ernst Boris Chain
(i.e. bacterial isolates remain susceptible to only one or two categories)
(i.e. no agents tested as susceptible for that organism)
MDROs
ESKAPE pathogen (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species), a group of pathogens with a high rate of antibiotic resistance that are responsible for the majority of nosocomial infections
Methicillin
Vancomycin
Carbapenem
Colistin
Clostridium difficile
Neisseria gonorrhoeae
WHO
Treatment of MDR-TB requires second-line drugs (i.e., Fluoroquinolones, IV aminoglycosides – amikacin, kanamycin, capreomycin
), which in general are less effective, more toxic and much more expensive than first-line drugs. Treatment schedules for MDR-TB involving fluoroquinolones and aminoglycosides can run for 2 years, compared to the 6 months of first-line drug treatment, and cost over $100,000 USD
Global Surveillance Report 2014 on AMR by WHO
Elevated MIC: Cefixime - 0.25 mcg/L Ceftriaxone – 0.125 mcg/L
UK Prime Minister commissioned the Review on
Antimicrobial Resistance in 2015 David Cameron
They lack the metabolic process or the target site which is affected by the particular drug
Bacteria are divided into two groups, Grampositive and Gram-negative, based on their cell wall formation and staining properties. Penicillin is effective only against Gram-positive bacteria because Gram negative bacteria have a lipopolysaccharide and protein layer that surrounds the peptidoglygan layer of the cell wall, preventing penicillin from attacking.
This type of resistance does not pose a significant clinical problem
Genetic variability is an evolutionary phenomenon which may occur by a variety of mechanisms – mutations, whole-scale rearrangements of large segments of DNA or acquisition of foreign DNA
When a microbial species is subjected to an existential threat, chemical or otherwise, that pressure will select for random mutations in the species’ genome that permit survival. Pathogens will evolve to develop resistance to the chemical warfare to which we subject them
Any sensitive population of a bacteria contains a few mutant cells which require higher concentration of the antibiotic for inhibition. These are selectively preserved and get a chance to proliferate when the sensitive cells are eliminated by the antibiotic. Thus, in time it would appear that a sensitive strain has been replaced by a resistant one. E.g. Rifampicin resistance
a mutation in the rpoB gene, which encodes the beta subunit of the bacteria's RNA polymerase. In non-resistant TB, rifampin binds the beta subunit of RNA polymerase and disrupt transcription elongation. Mutation in the rpoB gene changes the sequence of amino acids and eventual conformation of the beta subunit. In this case rifampin can no longer bind or prevent transcription, and the bacteria is resistant
here are many mutations that confer resistance to isoniazid (INH), including in the genes katG, inhA, ahpC and others. Amino acid replacements in the NADH binding site of InhA apparently result in INH resistance by preventing the inhibition of mycolic acid biosynthesis, which the bacterium uses in its cell wall. Mutations in the katG gene make the enzyme catalase peroxidase unable to convert INH to its biologically active form
Most common method
Gene cassettes have been identified for all antibiotics except for fluoroquinolones.
Direct physical mating between bacteria
Chromosomal or extrachromosomal conjugative plasmids containing r-genes , make a connecting tube (sex pili) between the two bacteria through which the plasmid itself can pass
Eg. Chloramphenicol resistance of typhoid bacilli, Streptomycin resistance of E. coli, penicillin resistance of Hemophilus and gonococci
(i.e., from a cell belonging to closely related or the same strain)
β-Lactamases can be classified according to their amino-acid structure into four molecular classes, A through D (Table 18-2), as first suggested by Ambler
Aminoglycoside-modifying enzymes confer antibiotic resistance through three general reactions: N-acetylation , O-nucleotidylation, and O-phosphorylation.
The outer membrane in Gr –ve bacteria is made of lipopolysaccharide is made up of tightly bound hydrocarbon molecules that impede the entry of hydrophobic antibiotics, such as nafcillin or erythromycin
The passage of hydrophilic antibiotics through this outer membrane is facilitated by the presence of porins, proteins that are arranged so as to form water-filled diffusion channels through which antibiotics may traverse.
Resistance to nalidixic acid and other quinolones in P. aeruginosa – mutational
Plasmid-mediated chloramphenicol resistance in E. coli
DNA gyrase is necessary for the supercoiling of chromosomal DNA in Gr –ve enteric bacteria to have efficient cell division
Alteration in DNA gyrase due to spontaneous mutations in gyrA gene that code of the two B subunits of the enzyme confer resistance to fluoroquinolones
IDSA – Infectious Diseases Society of America
SHEA – Society for Healthcare Epidemiology of America
alternating the predominant antimicrobial used for empirical therapy for all patients in a particular patient care area in a regular pattern over time
as bacteria in an intensive care unit (ICU) or hospital acquire new resistance genes directed against a predominant antibiotic, a new antibiotic to which the organism is susceptible will be introduced into the environment and will eradicate the emerging pathogens that are resistant to the prior antibiotics
Computer-assisted Stewardship Program affords a unique opportunity for instantaneous feedback, education, and alteration in prescription patterns
Common cold and flu
Investigate for potential focus of infection
targeting the most likely pathogen based on site of infection, age or prior antibiotic usage
For bacteria, dilution tests employ antibiotics in serially diluted concentra
tions
on solid agar or in broth medium that contains a culture of the test
microorganism. The lowest concentration of the agent that prevents visible
growth after 18–24 h of incubation is known as the minimum inhibitory
concentration (MIC).
Recently, nucleic acid amplification–based reactions of specific bacte
rial
genes have been used in the clinic for rapid diagnosis of drug resis
tance.
The genes targeted are those encoding known drug resistance
proteins or processes. For example, rifampin resistance in Mycobacterium
tuberculosis has been difficult to ascertain in a timely fashion: The bacteria
take 2 to 3 weeks to grow in order to identify them as a cause of disease,
and then a similar amount of time is needed to form some version of the
broth dilution tests. Small PCR reactors at points of care can purify and
concentrate a patient’s fluid sample, perform nucleic acid amplification of
a target gene, identify mutations, and provide a result in less than 2 h. In
other bacteria, MALDI-TOF MS is being used for identification of resis
tance
to drugs such as vancomycin in Staphylococcus aureus and is being
extended to many other compounds and bacterial species.
India, Indonesia, Nigeria and Brazil
Guidelines for the Prevention and Control of Carbapenem-Resistant Enterobacteriaceae, Acinetobacter baumannii and Pseudomonas aeruginosa in Health Care Facilities. Geneva: World Health Organization; 2017
WHO Guidelines on hand hygiene in health care should be implemented
Phages have been investigated as a potential means to eliminate pathogens like Campylobacter in raw food[23] and Listeria in fresh food or to reduce food spoilage bacteria
George Eliava Institute, Tbilsi, Georgia
Despite the limited effectiveness of colistin at 1 curing infection,
1
the risk of deteriorating renal function, and the fact that it has little activity against
2
Serratia spp., Providencia spp., and Proteus mirabilis [36, 37], in centres with
3
endemic carbapenem resistance, empiric therapy decisions now may likely dictate the
4
use of colistin over other agents
Keynote address at the conference on Combating antimicrobial resistance: time for action Copenhagen, Denmark 14 March 2012