Cephalosporin Resistance in Enterobacteriaceae Formulated by Dr.T.V.Rao MD

Cephalosporin Resistance in Enterobacteriaceae

Formulated by Dr.T.V.Rao MD?

???????????????????????????????????? We are living in a world of change in Infectious diseases. The emergence and spread of drug resistance in Enterobacteriaceae are complicating the treatment of serious nosocomial infections and threatening to create species resistant to all currently available agents. The emergence and spread of resistance in Enterobacteriaceae are complicating the treatment of serious nosocomial infections and threatening to create species resistant to all currently available agents. Approximately 20% of Klebsiella pneumoniae infections and 31% of Enterobacter spp infections in intensive care units in the Developed nations?? However we lack much need data form hospitals in many developing countries. Many updated Microbiology departments identify much growing resistance in Enterobacteriaceae involve strains not susceptible to third-generation cephalosporins. ESBLs are primarily produced by the Enterobacteriaceae family of Gram-negative organisms, in particular Klebsiella pneumonia and Escherichia coli; they are also produced by nonfermentative Gram-negative organisms, such as Acinetobacter baumannii and Pseudomonas aeruginosa.? Resistance in K.pneumoniae to third-generation cephalosporins is typically caused by the acquisition of plasmids containing genes that encode for extended-spectrum beta-lactamases (ESBLs), and these plasmids often carry other resistance genes as well. ESBLs are Class A β-lactamases and may be defined as plasmid-mediated enzymes that hydrolyse oxyimino-cephalosporins, and monobactams but not Cephamycins or Carbapenems. In general they are inhibited in vitro by clavulanate. To understand the basics third-generation cephalosporins are broad-spectrum drugs with high intrinsic activity against gram-negative species. Enterobacteriaceae with extended-spectrum β-lactamases (ESBLs) are now widespread and simple phenotypic tests are required to detect them in diagnostic laboratories. ESBLs are bacterial enzymes that confer resistance to many highly effective antibiotic classes that can go undetected if conventional testing methods are used in the laboratory, ultimately leading to treatment failure. Cephalosporin resistance among Enterobacteriaceae is changing in nature and prevalence worldwide, largely owing to the proliferation of CTX-M β-lactamases. In the UK, CTX-M extended-spectrum β-lactamases (ESBLs) were unknown before 2000, but are now the predominant mechanism among cephalosporin-resistant Escherichia coli and Klebsiella pneumoniae. Laboratories adopted a variety of methods to screen for cephalosporin resistance; cefpodoxime (5 μg), cefotaxime (30 μg) and ceftazidime (30 μg) discs were a used. However Cefpodoxime has been proposed as the best single screening cephalosporin to detect those isolates warranting further investigation as plausible ESBL producers. Isolates found resistant to either cefotaxime or ceftazidime during disc screening mostly (>89%) had confirmed cephalosporin resistance and a demonstrable mechanism. However, screening based on cefotaxime and ceftazidime requires that both of these drugs are tested, so as to reliably detect both CTX-M producers and those with ceftazidime-type TEM variants, ESBLs are Class A β-lactamases and may be defined as plasmid-mediated enzymes that hydrolyse oxyimino-cephalosporins, and monobactams but not Cephamycins or Carbapenems. They are inhibited in vitro by clavulanate. There are various genotypes of ESBLs. Of these, the most common are the SHV, TEM, and CTX-M types. Other clinically important types include VEB, PER, BEL-1, BES-1, SFO-1, TLA, and IBC. In 1995, Bush et al. devised a classification of β-lactamases based upon their functional characteristics and substrate profile, a classification which is widely used. The enzymes are divided into three major groups: group 1 cephalosporinases which are not inhibited by clavulanic acid, the larger group 2, broad spectrum enzymes which are generally inhibited by clavulanic acid (except for the 2d and 2f groups) and the group 3 metallo-β-lactamases. Most ESBLs are assigned to group 2be, that is, hydrolyse penicillin’s, cephalosporins, and monobactams, and inhibited by clavulanic acid (as per the Ambler classification). It should be noted that the CTX-M genotype was not classified in this original schemata but still fulfils the above criteria for group 2be enzymes.

?

?????????????????????????????????? Today Medicine is complex and advancing with technical support, critically ill patients are especially prone to infection, and the nature and epidemiology of causative agents can vary tremendously. In particular, drug-resistant pathogens are of a major concern, as they carry a higher morbidity and mortality and are more difficult to identify by routine laboratory assays, which can lead to a delay in diagnosis and institution of appropriate antimicrobial therapy. The delay in laboratory diagnosis and time to appropriate antibiotic therapy has been strongly linked to an increased mortality in these cases. It is also known that organisms producing ESBLs also have the ready capacity to acquire resistance to other antimicrobial classes such as the quinolones, tetracycline’s, Cotromoxazole, trimethoprim, and aminoglycosides, which further limits therapeutic options.

?

??????????????????? Most developing countries do not have resources to establish the genotypic detection but depend on the phenotypic methods the screening tests are based on testing the organism for resistance to an indicator cephalosporin. There are a variety of commercial tools available to do this, including double disc synergy, combination disc method, and specific ESBL’s However, if the isolate produces an additional AmpC or metallo-β-lactamase (which are not inhibited by clavulanic acid), these methods will lose their sensitivity. In 2023 CLSI, to overcome several inherent difficulties in reporting an effective cephalosporin to treat the patients has lowered the susceptibility breakpoints of some cephalosporins and aztreonam for Enterobacteriaceae and eliminated the need to perform ESBL screening and confirmatory tests. The change was meant to simplify the testing of ESBL and carbapenemase-producing organisms with the intent to minimize the need for subsequent confirmatory testing. Reference laboratories can test for genes encoding ESBLs by molecular analysis, primarily polymerase chain reaction amplification of specific sequences. This is usually reserved for epidemiological purposes, as it identifies the particular genotype of ESBL. Newer technologies such as the molecular techniques and modifications of mass spectrometry (matrix-assisted light desorption ionisation time-of-flight; MALDI-TOF) are being mooted as quicker alternatives to conventional laboratory diagnosis. However, these technologies are still relatively new in development and are not for use in most clinical institutions. There is no doubt that ESBL-producing infections are of grave concern to the medical world. They are associated with an increased morbidity and mortality and can be difficult and time consuming to identify. Coupled with the fact that prevalence rates are rising globally, including in nonhospital settings, and the dire lack of effective antimicrobial therapy, the future is tremendously concerning. Urgent work is required to develop quicker, cost-effective and reliable diagnostic tools as well as new effective therapies. To make matters simple in your laboratory for the testing of ESBL and carbapenemase-producing organisms, make changes in WHONET as per the current?? CLSI 2023 guidelines with new zones of susceptibility and make an effective reporting. The science of detection of Antibiotic resistance is beyond the affordability of majority of laboratories, a little of quality work will still can benefit the patients.

The vast majority of Enterobacteriaceae, including ESBL producers, remain susceptible to carbapenems, and these agents are considered preferred empiric therapy for serious Enterobacteriaceae infections. Carbapenem resistance, although rare, appears to be increasing. Particularly troublesome is the emergence of KPC-type Carbapenemase Better antibiotic stewardship and infection control are needed to prevent further spread of ESBLs and other forms of resistance in Enterobacteriaceae throughout the world.

Antibiotic Audit and Antibiotic stewardship continues to be priority? to understand issues related to increasing Antibiotic resistance patterns in our Hospitals?

?

Formulated by Dr.T.V.Rao MD??????????????????????????

??????????????????????????????