Microbiologia AULA Antibióticos 1

Prévia do material em texto

Controle Microbiano II
Antibioticos
Antibioticos – definicoes precisos 
• Os produtos microbianas mais importantes 
• Definição microbiologico: Substancia química produzido 
por m/o que inibe crescimento ou mata outros m/os 
• Definicao mais amplo (farmacia): Qualquer substancia 
quimica de qualquer tipo de celula (ate planta) que 
inibe ou mata celulas de outros organismos 
• No definicao microbiologico - Metabolitos secundários 
produzidos por fungos filamentosos e bactérias 
Antibioticos Semisinteticos - moleculas produzidas por 
microbios que sao modificados via quimica organica para 
aumentar atividade antimicrobiana ou modificar 
suficientemente para gerar novo patente ! 
Caracteristicas de Antibioticos
Efeitos - cida (mata) ou estatica (inhibitoria) effect
Espectro de acao – gama de mos afetados por certo antibiotico
Largo espectro – mata gama grande de bacterias Gram-positivos e Gram-negativos 
Estreito espectro – efetivo contra Gram-positivos OU Gram-negativos 
Espectro limitado – efetivo contra um organismo so
Espectros diversos
Caracteristicas ideias de antibiotico clinicamente util:
-Largo espectro 
-nao toxico no hospedeiro, sem efeitos colaterias 
-nao alergenico no hospedeiro 
-nao elimina microbiota normal no hospedeiro 
-alcance regiao do hospedeiro onde infeccao ocorre (ex - nao 
inativado pelo suco gastrico ou proteinas do sangue)
-barato e facil de producao
-Quimicamente estavel (longo prazo de validade) 
-Desenvolvimento de resistencia microbiana raro 
Some clinically important antibiotics
Antibiotic Producer organism Activity Site or mode of action
Penicillin Penicillium chrysogenum Gram-positive bacteria Wall synthesis
Cephalosporin Cephalosporium acremonium Broad spectrum Wall synthesis
Griseofulvin Penicillium griseofulvum Dermatophytic fungi Microtubules
Bacitracin Bacillus subtilis Gram-positive bacteria Wall synthesis
Polymyxin B Bacillus polymyxa Gram-negative bacteria Cell membrane
Microrganismos, alvo, e modo de acao
Polymyxin B Bacillus polymyxa Gram-negative bacteria Cell membrane
Amphotericin B Streptomyces nodosus Fungi Cell membrane
Erythromycin Streptomyces erythreus Gram-positive bacteria Protein synthesis
Neomycin Streptomyces fradiae Broad spectrum Protein synthesis
Streptomycin Streptomyces griseus Gram-negative bacteria Protein synthesis
Tetracycline Streptomyces rimosus Broad spectrum Protein synthesis
Vancomycin Streptomyces orientalis Gram-positive bacteria Protein synthesis
Gentamicin Micromonospora purpurea Broad spectrum Protein synthesis
Rifamycin Streptomyces mediterranei Tuberculosis Protein synthesis
Table 20.1
Histórico dos antibióticos e descobertas relacionadas
Paul Ehrlich (1854 - 1915): Desenvolveu o conceito de toxicidade seletiva, indicando que determinado agente exibia 
uma ação danosa aos microrganismos, sem afetar as células do hospedeiro. Esperava encontrar um corante tóxico aos 
microrganismos ("bala mágica").
1904 - Uso prático do vermelho de tripan, composto ativo contra o tripanossoma que causava a doença africana do 
sono.
Ehrlich & Hata: realização de testes com compostos arsenicais, em coelhos com sífilis. Descobriram que 
o composto 606, arsfenamida, era ativo => Em 1910, foi lançado o medicamento Salvarsan (nome 
comercial da arsfenamida), para o tratamento da sífilis.
1896 - E. Duchesne: descobriu a penicilina, mas raramente tal pesquisador é citado, pois seus achados 
nunca foram devidamente publicados ou notificados, sendo esquecids durante vários anos.
A. Fleming: Busca de um tratamento eficaz para os feridos na II Guerra Mundial. Foi o "segundo" 
descobridor da penicilina e tentou, sem sucesso, purificá-la em quantidades suficientes para ser descobridor da penicilina e tentou, sem sucesso, purificá-la em quantidades suficientes para ser 
utilizada como medicamento.
1944 - S. Waksman: descobrimento da estreptomicina (Streptomyces griseus), a partir do teste de cerca 
de 10.000 linhagens de bactérias e fungos do solo.
Até 1953 - Isolamento de microrganismos produtores de cloranfenicol, neomicina, terramicina e 
tetraciclina.
A partir de 1953 - a indústria investiu centenas de milhares de dólares na busca de novas drogas 
antimicrobianas, sendo que tal linha de pesquisa perdura até hoje em todo o mundo, empregando 
diversos tipos de abordagens.
Alexander 
Fleming
Microrganismos produtores
Fungos - Penicillium e Cephalosporium - produzem antibioticos beta-lactam 
- penicilinas e cephalosporinas
Servem como base para desenvolvimento de antibioticos beta-lactam semi-
sinteticos, como amoxacillina e ampicillina
Antibioticos Beta-lactam usados para tratar 30% de pacientes (for a do 
hospital – outpatients) com infecoes bacterianas
The natural habitat of molds is soil. And although sex is sometimes involved, 
they reproduce by spore formation. They are foremost in their abilities to 
degrade organic matter, and they play their most important role in natures in 
biodegradation and the carbon cycle. Most of us know that molds will grow biodegradation and the carbon cycle. Most of us know that molds will grow 
on nearly anything that is organic and moist, so they are also responsible for 
a lot food spoilage as well as decomposition of our structural materials and 
textiles. "Nothing is forever", with molds around.
Three colonies of a Penicillium mold 
growing on an agar medium. The green 
fuzzy appearance is the asexual spores of 
the fungus.
2. Actinomycetes, mainly Streptomyces species, 
produce tetracyclines, aminoglycosides
(streptomycin and its relatives), macrolides
(erythromycin and its relatives), chloramphenicol, 
ivermectin, rifamycins, and most other clinically-
useful antibiotics that are not beta-lactams. 
Actinomycetes are the mainstay of the antibiotics 
industry.
Actinomycetes are a group of branched bacteria 
that reproduce by spore formation. They come 
from a phylum of Bacteria, Actinobacteria, and from a phylum of Bacteria, Actinobacteria, and 
they are landed in Order Actinomycetales. Some of 
the representative family include such diverse 
bacteria as Actinomyces, Corynebacterium, 
Nocardia, Propionibacter, Streptomyces, 
Micromonospora and Frankia. Most actinomycetes 
are inhabitants of the soil. The characteristic odor 
of damp soil is due to the production of 
substances, called geosmins, by these bacteria
Geosmin is a volatile compound that's Geosmin is a volatile compound that's 
made by soil bacteria like Streptomyces, 
as well as some plants like sugar beets, 
and cyanobacteria. It gets blamed quite 
often for making water taste like dirt. Only 
a small amount is required (10 nanograms 
per liter) for detection by the human 
palate (1) and it's been blamed for adding 
a "dirt-like" taste to many things like 
water, wine, apple-juice, and catfish.
5 especies de Streptomycin
Metagenoma – 16S rDNA analise -
actinomicetos
3. Bacillus species, such as B. polymyxa and B. subtilis, produce 
polypeptide antibiotics (e.g. polymyxin and bacitracin), and B. cereus
produces zwittermicin. Bacillus species have the relatively rare ability to 
form a type of resting cell called an endospore. Bacilli are Gram-positive, 
rod-shaped, aerobic bacteria that live in the soil. They play an important 
ecological role in aerobic decomposition, biodegradation and mineral 
recycling.
A swirl of Bacillus mycoides colonies 
growth amidst other bacteria and molds 
from the soil. The swirls are always 
counterclockwise, at least in the Northern 
These organisms all have in common that they live in soil and they form some sort 
of a spore or resting structure. It is notknown why these microorganisms produce 
antibiotics, but the answer may be in the obvious - it affords them some 
nutritional or spatial advantage in their habitat by antagonizing the competition; 
or it may be in the subtle - it acts as some sort of hormone or signal molecule 
associated with sporulation or dormancy or germination. Antibiotics are 
secondary metabolites and they are produced at the same time that the cells 
begin their sporulation processes. 
counterclockwise, at least in the Northern 
Hemisphere 
Toxicidade seletivo de antibioticos = altamente efetivo contra microrganismo, 
toxicidade minimo contra humanos
Na pratica – expresso como therapeutic index (TI) da droga:
= razao entre dosagem toxico (no paciente) e dosagen terapico (para eliminar a infecao)
Maior o indice = droga mais seguro para uso humano
The selective toxicity of antibiotics is brought about by finding vulnerable targets for the 
drug in the microbe that do not exist in the animal (eucaryote) that is given the drug. 
Most antibiotics in clinical usage are directed against bacterial cell wall synthesis, Most antibiotics in clinical usage are directed against bacterial cell wall synthesis, 
bacterial protein synthesis, or bacterial nucleic acid synthesis, which are unique in some 
ways to bacteria. For example, the beta lactam antibiotics (penicillin and its relatives) 
inhibit peptidoglycan synthesis in the cell wall. Humans have neither a cell wall nor 
peptidoglycan and so are unaffected by the action of the drug. Other antibiotics, 
including streptomycin and the tetracyclines, target bacterial protein synthesis because 
bacterial ribosomes (termed 70S ribosomes) are different from the ribosomes (80S) of 
humans and other eucaryotic organisms. Antibiotics such as the flouroqinolones (e.g. 
ciprofloxacin) inhibit procaryotic (not eucaryotic) DNA replication, and rifamycins inhibit 
bacterial (not eucaryotic) DNA transcription. 
• Quanto à ação: "státicos" ou "cidas"
Os "cidas" podem ser "státicos" dependendo da concentração, ou do tipo de 
organismo.
Os "staticos" tem sua ação vinculada à resistência do hospedeiro.
• CMI e CML: 2 parâmetros que indicam a eficiência da droga.
A droga "cida" geralmente elimina o agente em concentrações de 2 a 4 vezes 
maior que a "stática“.maior que a "stática“.
• Atingir concentrações efetivas nos tecidos e entrar em contato com o 
microrganismo.
• Não alterar os mecanismos naturais de defesa do hospedeiro.
Teste de Susceptibilidade de bacterias
� CMI - Teste de Difusão em Placa
The agar diffusion test (Bauer-Kirby test)
A procedure commonly used in clinical labs to determine antimicrobial
susceptibility is the Bauer-Kirby disc diffusion method. In this test, the in
vitro response of bacteria to a standardized antibiotic-containing disc has
been correlated with the clinical response of patients given that drug.
Concentração Bactericida Mínima - CML
Antimicrobial Agents Used in the Treatment of Infectious Disease
Examination of the foregoing table reveals that there are a handful of fundamental ways that 
antibacterial antibiotics work as therapeutic agents. Recall that the target of an antibiotic should be 
unique to the bacterium and not found, or not accessible to the antibiotic, in the patient. These are the 
most important targets in bacteria that have been exploited so far.
1. Attack bacterial cell wall synthesis. Bacteria have murein in their cell walls, not found in the host, and 
murein (peptidoglycan) is essential to the viability of the bacterium.
2. Interfere with protein synthesis. Attack is almost always at the level of translation using 70S 
ribosomes in the translation machinery. 70S cytoplasmic ribosomes are absent in eucaryotes.
3. Interference with nucleic acid synthesis (RNA and DNA), which exploits differences between RNA 3. Interference with nucleic acid synthesis (RNA and DNA), which exploits differences between RNA 
polymerases and DNA replication strategies in bacteria and eucaryotes.
4. Inhibition of an essential metabolic pathway that exists in the bacterium but does not exist in the 
host. This is usually brought about through the use of competitive chemical analogs for bacterial 
enzymatic reactions.
5. Membrane inhibition or disruption doesn't work too well because of the similarities between 
eucaryotic and bacterial membranes. However, the outer membrane of Gram-negative bacteria is a 
reasonable point of attack and some membrane inhibitors are included in the discussion below
Mecanismos de ação de drogas antimicrobianas
Figure 20.2
Inibição da síntese da Parede Celular 
Cell wall synthesis inhibitors generally inhibit some step in the synthesis of 
bacterial peptidoglycan. They exert their selective toxicity against bacteria 
because humans cells lack cell walls. 
Beta lactam antibiotics. Chemically, these antibiotics contain a 4-membered beta 
lactam ring. They are the products of two genera of fungi, Penicillium and 
Cephalosporium, and are correspondingly represented by the penicillins and 
cephalosporins.
Chemical structures of some beta-lactam antibiotics. 
Clockwise: penicillin, cephalosporin, monobactam, 
carbapenem. Note the characteristic structure of the beta 
lactam ring.lactam ring.
The beta lactam antibiotics are stereochemically related to D-alanyl-D-alanine, which is a substrate for the last step in peptidoglycan 
synthesis, the final cross-linking between between peptide side chains. Penicillins bind to and inhibit the carboxypeptidase and
transpeptidase enzymes that are required for this step in peptidoglycan biosynthesis. Beta lactam antibiotics are bactericidal and require 
that cells be actively growing in order to exert their toxicity. 
Different beta lactams differ in their spectrum of activity and their effect on Gram-negative rods, as well as their toxicity, stability in the 
human body, rate of clearance from blood, whether they can be taken orally, ability to cross the blood-brain barrier, and susceptibility to 
bacterial beta-lactamases. 
Natural penicillins, such as penicillin G or penicillin V (benzyl penicillin), are 
produced by fermentation of Penicillium chrysogenum. They are effective against 
streptococci, gonococci and staphylococci, except where resistance has developed. 
They are considered narrow spectrum since they are not effective against Gram-
negative rods.
Penicillin G (Benzylpenicillin) is typically given by parenteral administration 
because it is unstable in the acid of the stomach. However, this achieves higher 
tissue concentrations than orally-administered penicillins and this increases its 
antibacterial potential. "PenG" may be used in treatment of bacterial 
endocarditis, gonorrhea, syphilis, meningitis, and pneumonia.
•Modo de Acao geral de penicilinas:
•Prevencao de sintese de tetrapeptideos (ligacoes cruzados no peptideoglicano, na parede celular)
•Penicilina liga com as enzimas transpeptidase, carboxipeptidase e endopeptidase) localizam-se logo abaixo 
da parede celular e são denominadas de " proteínas ligadoras de penicilina" (penicillin-binding proteins –
PBPs). 
•Resultado – as enzimas nao podem catalizar mais o reacao de transpeptidase, que faz a ligação entre as 
cadeias peptídicas, impedindo o desenvolvimento da estrutura normal do peptidoglicano
•Celulas existentes nao sao danificados
•Novas celulas crescem anormal – sem rigidez na parede celular – suscetivel a lise osmotica•Novas celulas crescem anormal – sem rigidez na parede celular – suscetivel a lise osmotica
•Penicilina G: inibe G+vos (mas sensivel a B-lactamase – enzima produzido por bacterias resistentes a 
penicilina)
•Ampicilina: inibe G+vos e G-vos (resistente a B-lactamase)
Gram+ e Gram –
Qual a diferença?
Penicillin Mode of Action – Inibicao 
de atividade enzimatica:
Semelhanca entre estrutura de 
penicilina e cadeia peptidica na 
parede celular bacteriana – explica 
modo de acao de antibioticos beta-
lactam
Parede Celular
� Estrutura complexo, semi rigida,
responsavel pela forma da celula
� Existem diferenças em bacterias
gram-positivas, gram-negativas
,arquibacterias e micoplasmas
� Circunda a membrana plasmatica (=
citoplasmática)
� Protege a celula: prevenir a ruptura da
celula quando a pressão da água
dentro e maior do que fora
� Forma usado para diferenciar
principais tipos de bacterias
Composição:
� Uma rede macromolecular –
PEPTIDEOGLICANA (= MUREÌ NA)
� Composto de um dissacarídeo
repetitivo unido por polipeptideos,
formando um rede
� dissacarideo e composto de
monossacarídeos de NAG e NAM
(N-acetilglicosamina e N-
acetilmurâmico)
� Moleculas alternadas de NAM e NAG (10 – 65
açucares)
� Filas adjacentes ligados por polipeptídeos
Parede celulare de celulas Gram-positivas 
� Muitas camadas de peptideoglicana 
� Acidos teicóicos (um alcool – glicerol ou ribitol) e 
fosfato 
� Acido lipoteicóico: atravessa as camadas de 
peptideoglicana para tocar a membrana 
plasmatica 
� Acido tecóico de parede: ligando as camadas 
de peptideoglicana 
� Acidos teicoicos tem carga negativa – regulam 
entrada de cations para dentro e fora da celula 
� Acidos teicoicos fornecem boa parte da 
especificidade antigenica da parede (usado na 
identificação de certos bacterias) identificação de certos bacterias) 
 
Parede celular de celulas Gram-negativos
•Uma ou algumas camadas de peptideoglicana mais 
uma membrana externa
•Peptideoglicana no espaço periplásmico (entre 
membrana externa e membrana plasmatico), ligado a 
lipoproteinas
•Não tem acidos teicoicos
•Pouco peptideoglicana = suscetivel ao rompimento 
mecanico
•Membrana externa: 
•Contem lipoproteinas, lipopolissacaridios, fosfolipidios
•Carga negativa forte (evita ação de fagocitos)
•Barreira para antibioticos (que atacam peptideoglicana)
•Porinas de proteinas: canais na membrana para o •Porinas de proteinas: canais na membrana para o 
movimento de moleculas (nucleotideos, dissacarideos, 
peptideos, aminoacidos, vitaminas) (e tambem 
invasores – eg virus)
•Lipopolissacarideos: contem polissacarideo O (atua 
como atigeno e util na identificação de Gram-negativos), 
e Lipideo A (uma endotoxina – toxico quando presente 
no sangue o trato gastrintestinal)
Penicillium notatum
inibindo a bacteria 
Mycococcus luteus
Efeito morfogenetico: 
�Esquerda – celulas bacterianas sem ampicilina no meio
�Direito – celulas bacterianas com ampicilina (celulas maiores (e mais fragil), e 
menos divisao celular)
Link: http://helios.bto.ed.ac.uk/bto/microbes/penicill.htm#crest
Semisynthetic penicillins first appeared in 1959. A mold produces the main part of 
the molecule (6-aminopenicillanic acid), which can be modified chemically by the 
addition of side chains. Many of these compounds have been developed to have 
distinct benefits or advantages over penicillin G, such as increased spectrum of 
activity (effectiveness against Gram-negative rods), resistance to penicillinase, 
effectiveness when administered orally, etc.; amoxicillin and ampicillin have 
broadened spectra against Gram-negative bacteria and are effective orally; 
methicillin is penicillinase-resistant. 
The semisynthetic beta-lactam, amoxicillin. Amoxicillin is usually 
the drug of choice within the class because it is better absorbed the drug of choice within the class because it is better absorbed 
following oral administration than other beta-lactam antibiotics. It 
is susceptible to degradation by bacterial beta-lactamase enzymes 
so it may be given with calvulanic acid (below) to decrease its 
susceptibility. It is used against a wide range of Gram-positive 
bacteria, including Streptococcus pyogenes, penicillin-sensitive
Streptococcus pneumoniae, non beta-lactamase producing strains 
of Staphylococcus aureus and Enterococcus faecalis. Susceptible 
Gram-negative organisms include non beta-lactamase producing 
strains of Haemophilus influenzae, Neisseria gonorrhoeae and N. 
meningitidis.
Penicilinas
Figure 20.6
Cephalosporins are beta lactam antibiotics with a similar mode of action to 
penicillins. They are produced by species of Cephalosporium molds. The have a low 
toxicity and a somewhat broader spectrum than natural penicillins. They are often 
used as penicillin substitutes against Gram-negative bacteria and in surgical 
prophylaxis. They are subject to degradation by some bacterial beta-lactamases, but 
they tend to be resistant to beta-lactamases from S. aureus.
The core structure of 
cephalosporin. Substituent cephalosporin. Substituent 
groups added at position X on 
the six-membered ring generates 
variants of the antibiotic.
Glycopeptides, such as the antibiotic vancomycin, inhibit both transglycosylation and 
transpeptidation reactions during peptidoglycan assembly. They bind to the 
muropeptide subunit as it is transferred out of the cell cytoplasm and inhibit 
subsequent polymerization reactions. Vancomycin is not effective against Gram-
negative bacteria because it cannot penetrate their outer membrane. However, it has 
become important in clinical usage for treatment of infections by strains of 
Staphylococcus aureus that are resistant to virtually all other antibiotics (MRSA).
Vancomycin is a glycopeptide antibiotic used in the 
prophylaxis and treatment of infections caused by Gram-
positive bacteria. It has traditionally been reserved as a drug 
of "last resort", used only after treatment with other of "last resort", used only after treatment with other 
antibiotics had failed, although the emergence of 
vancomycin-resistant organisms means that it is increasingly 
being displaced from this role by linezolid and the 
carbapenems. 
Vancomicina: Se liga a D-Ala-D-Ala, 
impedindo o crosslinking de G +
Alternativa a MARSA