The term “antibiotic” was put frontward by Vuillemin in 1889, to denominate the active constituent involved in the procedure of ‘antibiosis ‘ or to the resistance of one populating microorganism to another. Harmonizing to another school of thought – ‘antibiotics are nil but the microbic metabolites which in comparatively high dilution may suppress the growing of microorganisms ‘ .

Waksman proposed the widely cited definition that – ‘an antibiotics or an antibiotics substance is a substance produced by the microorganisms, which has the capacity of suppressing the growing and even destructing other microorganism ‘ .

However, the limitation that an antibiotic must be a merchandise of microorganism is non maintaining with common usage.


The antibiotics will be discussed explicitly under the undermentioned four chief caputs, viz. :

  1. ? – Lactum antibiotics
  2. Aminoglycoside antibiotics
  3. Chloramphenicol
  4. Tetracyclines


Beta – lactam anitibiotics are substrates for penicillinases and the interaction consequences in the devastation of thr antibiotics. There arenow known as agents which bind to the beta – lactamase enzymes and demobilize them, therefore saving ? – lactam antibiotics from devastation.

The ? – Lactum antibiotics may be farther divided into two classs, viz. :

( a ) Penicillins

( B ) Cephalosporins

1 ) Penicillins

Penicillin is the name assigned to the mixture of natural compounds holding the molecular expression C16H18N2O4S

The different merely in the nature of ‘R ‘ .

Assorted silent characteristics which finally determine the general construction of all penicillins:

1. The penicillins are all strong monobasic acids i.e. , they form salts.

2. The penicillins are hydrolysed by hot dilute inorganic acids ; one C atom is eliminated as C dioxide and two merchandises are obtained in equimolecular proportions, one being an aminoalkane, Penicillamine and the other an aldehyde, penniloaldehyde.

C9H11O4N2SR + 2H2O ? & gt ; CO2 + C5H11O2NS + C3H4O2NR

3. Combination of Cuprimine and Penilloaldehyde in Penicillin

It has been observed that the hydrolysis of penicillin with dilute base or with the enzyme ( beta-lactamase ) yields penicillonic acid ( a dicarboxlic acid ) , which readily eliminates a molecule of cabon dioxide to organize penilloic acid, thereby proposing that a carboxyl group is present in the ? – place with respect to a negative group.

4. Probablen structures for penicillin

Based on the foregoing chemical groundss likely constructions for penicillin are at that place:

Since penicillin is prone to undergo disconnected molecular rearrangement, e.g. , on intervention with dilute acid, penicillin rearranges to penillic acid.

Therefore, it was perfectly necessary to analyze the molecule by physical methods ( thereby go forthing the molecule integral ) . In fact, an intensive survey of the penicillins was carried out with regard to their infra-red and X-ray diffraction analysis.

Different types of penicillin

Chemical reaction utilizing penicillin

Man-made Penicillins

  • Penicilinase-resistant penicillins
  • Carbapenems: really wide spectrum
  • Monobactam: Gram negative
  • Extended-spectrum penicillins
  • Penicillins + b-lactamase inhibitors

2 ) Cephalosporins

The best known household of ? – lactams are termed as the Mefoxins, wherein the ? – lactam ring is strategically fused to a six-membered dihydrothiazine ring system. The thiazine pealing merger makes the ? – lactam system more stable but non to the full immune to opening by acids and beta-lactamase.


The Mefoxins may be classified under the undermentioned four classs:

  • First coevals
  • Second coevals
  • Third coevals
  • Fourth coevals

First coevals





Active against G+ coccus ( except.enterococci & A ; MRSA ) : s.pneumoniae, s.pyogenes, s. aureus, s.epidermidis

Indicated for streptococcic sore throat ( e.g. Keflex )

Normally used ( eg. Cefazolin ) as prophylacic for surgical processs.

Modest activity against G- bacteriums

Second coevals

Cefoxitin ( cephalosporin )

Cefuroxime ( cefuroxime )

Cef. axetil ( zinnat )

Cefaclor ( ceclor )

Cefprozil ( cefzil )

Chiefly effectual against G- bacteriums

Modest activity against G+ bacteriums

Cefoxitin active against intestine anaerobes ( B. fragilis )

Cefuroxim active against H. influenzae, M. catarrhalis, S. pneumoniae

Cef. Axetil- unwritten signifier of cefuroxim

Cefaclor active against H. influenzae, M. catarrhalis & A ; E.coli

Cefprozil- similar to cefaclor, c. axetil and augmentin- Liked by kids

Second Coevalss are used chiefly for URTIs ( acute otitis media, sinusitis ) and Lower RTIs ( acute aggravation of chronic bronchitis ) .

Third coevals

Cefotaxime ( cefotaxime )

Cetazidime ( fortum )

Cefoperazone ( cefoperazone )

Cefixime ( suprax )

They have enhanced G- activity, H. influenzae, N. meningitidis, N.gonorrhea, P. aeruginosae, M. catarrhalis, E.coli, most Klebsiella

Ceftriaxone has long half life. Not advised in newborns ( interferes with bilirubin metamorphosis )

Cefotaxime preferred in newborn ( does non interfere with bilirubin metamorphosis ) , as may ceftriaxone.

Ceftazidime & A ; Cefobid have first-class activity against p. aeruginosae.

Cefixime has similar activity to amoxicillin & amp ; cefaclor for actute otitis media

Fourth coevals


Active against G+ bacterium & gt ; than cefazolin against s. pyogenes, s.pneumoniae but lower against s. aureus.

Similar to cefotaxime against E.coli & A ; K. pneumoniae but & lt ; for p. aeruginosa.


The aminoglycoside antibiotics constitute an of import class of antibacterial agents in the curative armamentarium, e.g. , streptomycins, fradicins, paramomycin and the corresponding derived functions of these antibiotics.

These are a clump of closely related chemically basic saccharides that are largely water-soluble. Their several hydrochlorides and sulfates are crystalline in nature. They are found to be effectual in suppressing the growing of Gram-positive every bit good as Gram-negative bacteriums. They are besides effectual to a great extent against mycobacterium.

A few illustrations are discussed below:

( a ) Streptomycin is chiefly employed in the intervention of TB in concurrence with each other drugs such as INH and rifampicin.

Streptomycin and penicillin exerts a interactive action against bacteriums and are normally employed together in the intervention of subacute bacterial endocarditis caused by streptococci faecalis

Mechanism of Action: The ‘drug ‘ exerts its maximal effectivity against the being Mycobacterium TB. Interestingly, the antibiotic is non a remedy itself but has proved to be an first-class and valuable adjunct to other modes of curative intervention for TB. It acquires a rapid development with regard to certain strains of micro-organisms. The combined disposal of streptomycin and penicillin has been suggested to battle infection which may be due to organisms that are sensitive to both these antibiotics. The ‘drug ‘ is neither captive nor destroyed appreciably the GI piece of land.

( B ) Neomycin is largely used in a broad assortment of local infection such as Burnss, ulcers, lesions, impetigo, septic dermatoses, furunculosis etc. It is employed as an adjuvant in topical steroid readyings to command secondary infections in the instance of inflammatory upsets.

Structure of Neomycin

Mechanism of Action: The ‘drug ‘ normally gets captive really seldom from the digestive system ; hence, its unwritten disposal chiefly fails to bring forth any significant consequence. Mechanism of Action: The ‘drug ‘ normally gets captive really seldom from the digestive system ; hence, its unwritten disposal chiefly fails to bring forth any significant consequence.


Chloramphenicol is a levorotary broadspectrum antibiotic originally produced from a several streptomycetes, viz. : S.venezualae, S.omiyamensis and S.phacochromogenes var.chloromyceticus. It has been reported to be the drug of pick for the intervention of typhus and enteric fever febrility.

However, Chloromycetin is of paramount involvement owing to the undermentioned three reaons:

  1. It is of course happening aromatic nitro compound of which there is merely one antecedently recorded illustration of hiptagin, obtain organize the root bark of Hiptage madablota Gaertn is notable.
  2. It is capable of exercising its consequence against viral diseases every bit good as those due to bacterial invasion and opens up the whole field of the chemotherapy of virus and rickettsial infections in adult male including typhus, undulatory febrility, Salmonella blood poisoning, whooping cough, stomach flu, lymphogranuloma inguinale, enteric fever and paratyphoid. So far, chloramphenicol-fast strains have non been isolated.
  3. It is conformable to synthesis on an industrial graduated table.

Structure of Chloramphenicol

The construction of Chloromycetin has been established on the footing of the undermentioned critical chemical grounds. They are:

  1. The molecular expression of Chloromycetin is C11H12Cl2N2O5.
  2. Its soaking up spectrum is similar to the nitrobenzene.
  3. The presence of nitro group was revealed by the decrease of Chloromycetin with Sn ( Sn ) and hydrochloric acid, followed by diazotization and so matching to give an orange precipitate with ?-napthol.
  4. When reduced catalytically ( with Pd, Pd ) it gives a merchandise which has an soaking up spectrum really similar to that of para-toluidine and the resulting solution gives a positive trial for ionic Cl

Synthesis of Chloramphenicol


Acetic acid

Chloramphenicol Methanol


Tetracyclines are a group of wide spectrum antibiotics whose general utility has been reduced with the oncoming of bacterial opposition. Despite this they remain the intervention of pick of some specific indicant.

Structure of Tetracycline Charaterstics of Tetracyclines

  1. The Achromycin are obtained by agitation processs from streptomyces species or by the chemical transmutation of the natural merchandises.
  2. The of import members of this household are basically derived functions of an octahydronaphthacene, i.e. , a hydrocarbon made up of a system of four-fused rings.
  3. The antibiotic spectra and the chemical proprerties of these compounds are rather similar but non indistinguishable.
  4. The Achromycins are amphiprotic compounds, i.e. , organizing salts with either acids or bases. In impersonal solutions these substances exist chiefly as Zwitter ion.
  5. The corresponding hydrochloride salts are used most normally for unwritten disposal and are normally encapsulate owing to their acrimonious gustatory sensation.
  6. The H2O soluble salts are obtained from bases such as sodium/potassium hydrated oxides or formed with divalent/polyvalent metals, e.g. , Ca++ . The former 1s are non stable in aqueous solution, while the latter 1s, e.g. , Calcium salt give tasteless merchandises that may be employed to fix suspensions for liquid unwritten dose signifiers.


Antibiotics have revolutionized the modern medical sphere and saved countless lives. Antibiotics are good for those patients who are enduring from the bacterial diseases because it merely effects and bring around the bacterial diseases such as TB, etc. There are besides broad-spectrum types of antibiotics which work every bit good on bacteriums and fungus. It is cost effectual and readily available as compared to others. There are over a 100 of types of antibiotics but the bulk of the diseases can be cured from few types. Each antibiotic is effectual merely for some types of disease and your physician knows the best.
In most instances, the physician prescribes antibiotics with less side-effect which suits your organic structure phenomena. Suppose if you are enduring from pneumonia, the physicians knows good how to handle this by an antibiotic and which bacteria caused this respiratory system disease. It is necessary in antibiotics to take attention of the dosing because in antibiotic medicines, physician prescribes patient the whole class of the antibiotics and it will be harmful for the patient if he or she does n’t move consequently. If the right antibiotic is taken as prescribed, it will bring around the disease in the shortest span of clip.


As there are many advantages of the antibiotics, there are besides many disadvantages of utilizing antibiotics. Excess of everything is bad. The first and the major demerit of the antibiotics are in the signifier of side consequence. Some of the most common side effects are: Diarrhea, mild tummy disturbance, purging, soft stools, etc. and in serious instances the side effects will be: Severe watery diarrhoea and abdominal spasms, Allergic Reaction, Shortness of breath, vaginal itchiness or discharge, etc. So, if patient have any of these side effects, they must confer with their physician instantly.

The antibiotics were foremost given merely to those patients who had minor diseases like pot disturbance, etc. but is has been proved that the repeat of the antibiotics is harmful and may do serious diseases like Cancer. Many of the medical research centres has declared that the over usage of the antibiotics is harmful for the human organic structure as the frequent usage, effects and upset the human internal ecology and homeostasis.

In most instances, if physicians do n’t cognize about the bug, they prescribe their patients BROAD-SPECTRUM antibiotics and it harms because it removes all the bacteriums either they are good or harmful, hence in this manner BROAD-SPECTRUM antibiotics are harmful for human. Doctor prescribes kids tetracycline antibiotic and due to the side effects of these antibiotic medical specialties, it decreases the degree of Fe, Ca, Mg and can besides do psoriasis. Excessive usage of antibiotics can ensue in depletion of Fe content ensuing in sickle-cell anaemia.

In a nutshell, after sing all the advantages and disadvantages, we can clearly deduce that the frequent and over usage of antibiotic drugs is harmful for us. Medicines are for our public assistance but there are besides some side effects associated with them. Medical Science is working to cut down the side effects but we should take attention while covering with antibiotics.


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