Presentation on theme: "Daniel Garang Kuir. BBioMedSci, USQ M App Sci (MedSci), RMIT."— Presentation transcript:
Daniel Garang Kuir. BBioMedSci, USQ M App Sci (MedSci), RMIT
Members of Enterobacteriaceae family are a heterogeneous group of gram negative bacteria. Are part of human’s normal enteric flora. Are also abundantly distributed in nature. Include some prominent, often opportunistic, human pathogens; Such as E. coli (e.g uropathogenic E. coli), Klebsiella spp, Enterobacter spp, Citrobacter spp, Salmonella spp, Shigella spp, Yersinia pestis, Serratia marcescens, Proteus spp, Morganella spp, & Providencia spp. Majority are often expediently termed as the “ESCPPM” organisms – which stands for Enterobacter spp, Serratia spp, Citrobacter freundii, Proteus vulgaris & penneri, Providencia spp, & Morganella morganii. Several members of this group are ESBL - &/or AmpC- producers. K. pneumoniae & E. coli are major producers of ESBLs in this group of gram negative bacteria.
Production of β-lactamases in Enterobacteriaceae is a common mechanism of antimicrobial resistance. These β-lactamases include the novel β-lactamases such as ESBLs, AmpC…etc, & others such as; ◦ Penicillinase, cephalosporinase, broad-spectrum, extended-spectrum, carbapenemase. AmpC β-lactamases are chromosomally encoded cephalosporinases (chromosomal bla genes). AmpC are expressed in many Enterobacteriaceae and other organisms. AmpC induce, by constitutive hyperproduction or mutation, wide-ranging resistance to first-, second-, and third- generation cephalosporins, most penicillins, and beta- lactam/beta-lactam-inhibitor (BL/BLI) combinations.
Production of novel β-lactamases e.g. ESBLs, AmpC; In tandem with production of β-lactamases, Enterobacteriaceae employ other mechanisms of resistance such as; ◦ enzymatic inactivation; ◦ efflux pumps; ◦ outer membrane porin loss; ◦ target modifications; ◦ transfer or acquisition of new genetic material, or ◦ mutations – ESBLs are essentially derivative enzymes acquired through mutations - substitution or deletion of amino acids - in progenitor β- lactamases (e.g TEM, SHV or CTX-M).
ESBLs are novel β-lactamases - are newer β-lactamases of pathogenic gram negative bacteria (esp. Enterobacteriaceae family). ◦ These novel β-lactamases also include; Plasmid-mediated AmpC β-lactamases; Carbapenem-hydrolysing β-lactamases (e.g. Klebsiella pneumoniae carbapenemases (KPC)); Β-lactamases with reduced sensitivity to β-lactamases inhibitors Definition: ESBLs are bacterial enzymes capable of hydrolysing and thus conferring resistance to all penicillins, first-, second-, & third- generation cephalosporins, and aztreonam. And are inhibited by β-lactamase inhibitors such as clavulanic acid, sulbactam and tazobactam. ESBLs are plasmid-mediated enzymes that confer multi-drug resistance to gram negative bacteria. ESBLs may be co-expressed &/or co-transmitted with chromosomally- encoded AmpC β-lactamases – thus presence of ESBLs may be masked by AmpC.
ESBLs hydrolyse all β-lactam antibiotics – penicillins and cephalosporins. β-lactamases possess either a serine moiety or a zinc atom in the active site, Either of which is vital for hydrolysis of the β-lactam ring of a β–lactam antibiotic. ESBLs are diverse, quickly evolving & therapeutically difficulty to eradicate. ESBL production in Enterobacteriaceae also render them resistant to other major classes of antibiotics such as; ◦ Fluoroquinolones (e.g. ciprofloxacin, norfloxacin), ◦ Aminoglycosides (e.g. gentamicin, tobramycin, amikacin) ◦ Tetracyclines (e.g. tetracycline) ◦ Trimethroprims-sulfamethoxazole (Cotrimoxazole) ◦ Other antibiotic classes NB : β-lactamase production, co-expression of ESBL &/or AmpC, carriage of other resistance gene on the same plasmid account for multidrug resistance in this group of bacteria. ESBL-mediated extensive antimicrobial resistance poses public health risks. ESBL-producing Enterobacteriaceae are essentially multidrug resistant bacteria.
Source: Rosário NA, Grumach AS. Allergy to beta-lactams in paediatrics: a practical approach. J Pediatr (Rio J). 2006;82(5 Suppl):S181-8.
Source: Partridge, S. (2014). Movement of resistance genes in hospitals. Microbiology Australia.
ESBL-producing Enterobacteriaceae (ESBL-PE) cause significant mortality and morbidity globally. ESBL-PE cause a range of infections including uncomplicated UTIs, life- threatening bacteraemia, URTIs, gastroentritis, & colonising wound infections. Mortality of patients with ESBL +ve sepsis is significantly higher than those with ESBL -ve sepsis – up to 30% of GNB-caused sepsis is fatal. Are implicated in large scale outbreaks in hospital or community settings. Cause localised or institutionalised outbreaks. Infections caused by ESBL-PE are associated with rising healthcare cost. Decreased productivity as a consequence of prolonged hospitalisation. ESBL-PE are associated with increasing episodes of clinical treatment failure.
ESBL producing organisms have important therapeutic and clinical ramifications for patients from whom they are isolated. ESBL-PE pose significant public health risks. ESBL-PE pose serious infection control challenges. ESBL production in Enterobacteriaceae has been a consequence of widespread use of broad spectrum antibiotics in hospital settings. Increasing prevalence is reported in isolates recovered from community- based patients. ESBLs are transferrable via conjugative plasmids thus dissemination of resistance genes among bacterial populations can occur and spread in larger geographic regions. Treatment of ESBL-PE involves a combination of antibiotics, some of which have undesirable side effects including nephrotoxicity.
Risk factors for infections with ESBL-PE in healthcare- or community-acquired infections include; ◦ Previous use of antibiotics including broad spectrum antibiotics e.g 3GC cephalosporins; ◦ Recent or prolonged hospital admissions including admissions to ICU; ◦ Recurrent UTIs; ◦ Empiric antibiotic therapy ◦ Increased age; female gender; institutionalised residential care e.g. nursing homes; ◦ Intravenous therapy; ◦ International travels to areas of established endemicity e.g India subcontinent, the Middle East and Africa; ◦ Immunosuppressive chemotherapy; ◦ Invasive procedures- indwelling urinary catheters; central venous catheter, and ◦ Underlying comorbidities such as chronic renal insufficiencies, haemodialysis, liver disease, diabetes mellitus, malignancy, hypertension, heart disease, neutropenia, and HIV infection
ESBLs were first reported in Germany in 1983. This followed introduction of broad spectrum 3G cephalosporins into clinical use. ESBLs have been reported in all parts of the world – except Antarctica. ESBLs are derivatives of classic β-lactamases eg SHV-2 is derived from SHV-1. ESBLs are occasioned by single mutations in progenitor (parent) enzymes ◦ A mutation of few amino acids. ESBLs exhibit fundamental changes in substrate spectra, substrate profile, reactions to inhibitors & isoelectric point – important distinguishing factors. Over 200 ESBLs are characterised & classified – there is still no consensus on exact figure. Β-lactamases have been variously classified over time. Two commonly used classification schemes are; ◦ Ambler molecular classification system ◦ Bush-Jacoby-Medeiros functional classification system.
The Ambler molecular system classifies β-lactamases on the basis of protein homology (amino acid similarities); ◦ 4 major classes (A, B, C & D). The Bush-Jacoby-Medeiros functional system classifies β- lactamases, on the basis of functional similarities/substrate and profile inhibitor profile; ◦ 4 main groups (1, 2, 3 & 4). ESBLs are derived from group 2be β-lactamases; ◦ the `e’ of 2be denotes the extended-spectrum capability of the newly derived enzyme. ESBLs are quite diverse. Clinically important ESBLs are derived from 3 major types of classic beta-lactamases; TEM-, SHV-, & CTX-M-type β- lactamases. ◦ Temoniera – a Greek patient from whom this ESBL type was first isolated. ◦ SHV - Sulfhydryl Variable. ◦ CTX-M - Cefotaxime – Munich (first isolated in Munich)
Snapshot of major ESBLs – SHV -, TEM- & CTX-M-types including rare and peculiar ESBLs
Enzyme familyFunctional group or subgroup No. of enzymesRepresentative enzymes CMY1, 1e50CMY-1 to CMY-50 TEM2b, 2be, 2br, 2ber172 2b12TEM-1, TEM-2, TEM-13 2be79TEM-3, TEM-10, TEM-26 2br36 TEM-30 (IRT-2), TEM-31 (IRT-1), TEM- 163 2ber9TEM-50 (CMT-1), TEM-158 (CMT-9) SHV2b, 2be, 2br127 2b30SHV-1, SHV-11, SHV-89 2be37SHV-2, SHV-3, SHV-115 2br5SHV-10, SHV-72 CTX-M2be90CTX-M-1, CTX-M-44 (Toho-1) to CTX- M-92 PER2be5PER-1 to PER-5 VEB GES 2be 2f 7 15 VEB-1 to VEB-7 GES-2 to GES-7 (IBC-1) to GES-15 KPC2f9KPC-2 to KPC-10 SME2f3SME-1, SME-2, SME-3 OXA2d, 2de, 2df158 2d5OXA-1, OXA-2, OXA-10 2de 2df 9 48 OXA-11, OXA-14, OXA-15 OXA-23 (ARI-1), OXA-51, OXA-58 IMP3a26IMP-1 to IMP-26 VIM3a23VIM-1 to VIM-23 IND3a8IND-1, IND-2, IND-2a, IND-3 to IND-7 [i] [i] Enzyme families classified on the basis of amino acid structures (G. Jacoby and K. Bush, http://www.lahey.org/studies/). http://www.lahey.org/studies/). [ii] [ii] The sum of the subgroups in each family does not always equal to overall number of enzymes in each family due to withdrawn or non-classification of some enzymes.
Stats of ESBL epidemiology are profoundly varied – all parts of the world have different rates of prevalence. In general terms; ◦ TEM-type ESBLs are predominantly reported in the United States, ◦ SHV-type ESBLs are most frequently isolated in Western Europe. ◦ CTX-M-type ESBLs have been detected in Australia, Latin America, Eastern Europe, and in specific countries such as Japan, Spain, & Kenya. Global epidemiology captures in major surveillance studies; ◦ AGAR (Australia) ◦ SENTRY (US, Canada & Latin America) ◦ SMART ( Global - US, SE Asia) ◦ EARSS (European countries)
CountryStudy name or period K. pneumoniaeE. coli Number of isolates Percentage of ESBL positive Number of isolatesPercentage of ESBL positive CanadaSENTRY 1997- 1999 3864.912034.2 US and CanadaSENTRY 19981924.2-- USASENTRY 1997- 1999 20177.949663.3 USASENTRY 1997409447714.7 Latin AmericaSENTRY 1997- 2000 25543.911425.4 Latin AmericaSENTRY 1997- 2000 1274023310.0 Latin AmericaSENTRY 1997- 2000 66447.312396.7 Latin AmericaSENTRY 1997- 1999 89745.420268.5 EuropeSENTRY 1997- 1999 94622.638225.3 Italy199994620.0 46041.2 SpainEARSS 2001--19621.55 France1996-2000612111.4-- GermanyPEG 20012688.26190.8 Netherlands1997196<1571<1 Turkey19974348.85301.1 Western Pacific area SENTRY 1997- 1999 56024.611047.9 Asian Pacific area SENTRY 1998- 1999 67825.2133710.1 China19995595142723.6 Taiwan200012411.317711.9 Hong Kong19984721370211
Use of both genotypic and phenotypic techniques. Phenotypic testing – a 2 steps process; ◦ Screening; screening process aims to exclude potential ESBL-producing isolates by testing for resistance or reduced susceptibility to 3GC cephalosporins. Screening using cefotaxime, cefpodoxime, ceftazidime, and aztreonam discs. multiple 3GC agents reliably improves sensitivity by offering wider ESBL substrate base. ◦ Confirmation; second step tests for synergy between 3GC cephalosporins & clavulanates (synergy between β-lactams and β-lactams-clavulanate combinations) – also known as DDST (double disc synergy test). A disc zone diameter difference of ≥5 mm between a cephalosporin and its respective cephalosporin- clavulanate is taken as a phenotypic confirmation of ESBL production. e.g an ESBL-producer tested against ceftazidime produces these resistance zones: ceftazidime zone = 16; ceftazidime-clavulanic acid zone = 21) Automated (Vitek 2 systems) MBD ◦ Automated microbroth dilution - growth at or above screening concentrations (breakpoint) may indicate production of ESBL (that is, for E. coli and K. pneumoniae, MIC ≥ 2 μg/mL for ceftriaxone, ceftazidime, aztreonam, or cefpodoxime). E-test, microScan panels and other discs-based methods are also used.
Can you tell a plate depicting ESBL positive in the Figure above?
SettingESBL positiveESBL negativeTotal Hospital30259289 community75402477 Total105661766 Frequencies at assigned age categories 0-20 years old21-40 years old41-60 years old≥61 years old 11261553
Comparison of percentage resistance of ESBL-producing isolates recovered from patients in hospital (HP) and community (CP) settings
What should be done to curb increasing threats pose by ESBL- mediated antibiotic resistance; ◦ Robust antibiotic stewardship – appropriate use of antibiotics ◦ Effective infection control measures in hospitals – effective preventive measures to curb transmission; Contact precautions, Hand hygiene, Disinfections of inanimate objects, surfaces, medical devices in healthcare facilities ◦ Public education – antibiotic resistance awareness campaign. ◦ Controlling use of antibiotics in food chains – control & regulation of antibiotic use in agriculture. ◦ Immunization – preventative & indirect ◦ Development of newer, potent antibiotics against emerging multidrug resistant bacteria. ◦ Timely detection, and reporting of ESBL producing bacteria by medical laboratories. ◦ Instituting infection control measures in institutionalised care settings – eg nursing homes. ◦ Active screening for multi-drug resistant Enterobacteriaceae. ◦ Classifying ESBL-PE as notifiable infections???
Therapeutic options are very limited. Treatment usually involves a combination of drugs. These are usually the expensive, last line of antibiotics; Carbapenems (e.g meropenem, ertapenem) Fosfomycin. β-lactam/β-lactam-inhibitor combination drugs (e.g Amoxicillin-clavulanate, piperacillin-tazobactam…etc) – supporting evidence from clinical studies is, however, controversial. Limitation of therapeutic drugs is also compounded by other factors such as ; ◦ Site of infection, ◦ Severity of infection, ◦ Renal or liver functions of a patient, ◦ Age, ◦ Pregnancy or lactation status, ◦ Other medications the patient may be taking.