The MIC test demonstrates the lowest level of antimicrobial agent that inhibits growth, the MBC demonstrates the lowest level of antimicrobial agent that results in microbial death. This means that even if a particular MIC shows inhibition, plating the bacteria onto agar might still result in organism proliferation because the antimicrobial did not cause death. Antibacterial agents are usually regarded as bactericidal if the MBC is no more than four times the MIC

The MIC test demonstrates the lowest level of antimicrobial agent that inhibits growth, the MBC demonstrates the lowest level of antimicrobial agent that results in microbial death. This means that even if a particular MIC shows inhibition, plating the bacteria onto agar might still result in organism proliferation because the antimicrobial did not cause death. Antibacterial agents are usually regarded as bactericidal if the MBC is no more than four times the MIC

your results are ok. MBC: means, minimum bactericidal concentration (99% of killing bacteria), on the other hand MIC: the concentration needed to kill 90% of bacteria. so theoretically, the MBC should be higher than MIC

an other advice, for MIC and MBC examinations, i prefer to used the plating system, Although, it is tough but more accurate than tubing.

Thank you so much Prof.Tamara and Prof . Ebrahim, I am grateful to you.

So, we can say that my extract tend to be more bacteriostatic rather than bactericidal . 

Or, this extract is bactericidal at high concentrations and bacteriostatic at low concentrations.

Regarding MBC methodology, yes Prof. Ebrahim I agree with you,  have a look to my MBC plate!

C= positive control (bacteria only), 1 to 7= 400 to 6.5 mg/ml

from this pic. you have 3 concentrations with the same effect, but i can not say that this could act as MBC, because the pic is not very clear. according to my experience, you can use other plating technique called micro dilution agar plate.

you prepare plates inoculated with a specific number of bacteria (usually 10 power 5 or 6/ml). then you add the medium that contains the antibacterial with specific concentrations, pouring and incubating at the optimum temperature, then count the bacteria in comparison to the control, in this case you can calculate exactly the % of inhibition and you can extract the MIC and MBC.

Refer to the following book, the answer you'll find may help you.

Nice day

https://books.google.iq/books?id=QZXnCAAAQBAJ&pg=PA51&lpg=PA51&dq=Could+you+please+help,+MBC+are+higher+than+MIC?&source=bl&ots=Ye4Xon8MXg&sig=JIXTUhvMRKghX5fYKn1cAF-prd0&hl=ar&sa=X&ved=0ahUKEwjz8tG5ntjKAhUrqXIKHcWdC0wQ6AEIMjAD#v=onepage&q=Could%20you%20please%20help%2C%20MBC%20are%20higher%20than%20MIC%3F&f=false

Thank you so much my dear collages for all these valuable information which solved my problem, and added me new ideas.

Thank you Prof. Ebrahim, Prof. Bhoj and Prof. Ali . I am greatly thankful.

Emad

In some cases it will occur as that could be the concentration that killed the bacteria completely- MBC while the other concentration(MIC) only inhibited the bacteria from normal growth. Some of the times both concentration may be same so it proper just to use a simple explanation. 

you are most welcome.

I would worry only if it were the other way around. This is just fine. MBC≥MIC, the former is a measure of cidality whereas the latter is minimum drug concentration required to inhibit the growth of bacteria. 

So, Dr. Krishan , 

In my case, how to classify this plant extract?

Bactericidal or bacteriostatic?

Regards

Emad

By definition (MBC:MIC::1:1-2:1), I would say this could be categorized as bacteriostatic. But these methods of MIC/MBC determination and definitions/guidelines have been standardized for reporting purposes. 

Dear Researchers,

You all must be knowing that minimum inhibitory concentration (MIC) is the lowest concentration of an antimicrobial agent that will inhibit the visible growth of a microorganism after overnight incubation. Whereas, minimum bactericidal concentration (MBC) is the lowest concentration of an antibacterial agent required to kill a particular bacterium.

Definitely more amount (concentration) of an agent is required to completely kill a bacterium {Bactericidal intervention} than to just inhibit its growth {Bacteriostatic intervention}. So, its perfectly obvious to get MBC higher than MIC. 

Regards

Pallavi Thakur

Researcher

DRDO, Ministry of Defence

Govt. of India

When performing antimicrobial susceptibility we determine both MIC and MBC. Sometimes both values are equal while sometimes MBC value is higher. While interpretimg activity of antibiotics we compare our MIC values with reference values against each organism like CLSI standards or BASC or other international standards. This figure can not be generalized when evaluatiog other agents like plant extracts since no approved standards are available. Just compare your MIC and MBC values with those of other related stufies available. This is the role till approved values are standardized. Good luck

Thank you so much all, for your kindness and generosity. When I wrote this question I did not expect  fast interaction.I appreciate and thankful.

Good luck all and best wishes.

Regards

Emad

MBC≥MIC because MIC is the concentration to inhibit the growth while the MBC concentration is necessary to kill the microorganism (bactericidal).

Thanks a lot Dr. Ivana

Best wishes

MBC greater or equal to MIC is the expected one. It is a good finding. In your extract, it required 4x MIC to kill all the bacteria (cidal effect). To this effect, we cant call it bactericidal or bacteriostatic right now. I f by chance your extract reaches clinical trial, then we can classify it as bactericidal if this bactericidal concentration of 50 mg/ml could be reached at the site of infection without causing unacceptable toxicity to any part of the body, i mean below minimum toxic concentration. Otherwise, it could be labelled bacteriostatic if it could be given only to achieve below that concentration.

Your result is not out of place MBC can be equal or greater than MIC 

Mr. Emad M. Abdallah, your results are completely perfect because MIC is that minimum concencentration at which the growth of bacteria started to get inhibit, while in case of MBC the growth get completely disappear that's why it is bactericidal concentration, which should be higher than MIC.

Thanks Drs: Yadesa, Stephen and Ankita. I am grateful.

Truly yours,

Emad

your results are perfect, because MIC means: the minimum concentration that stop bacterial growth against MBC means: the minimum concentration which "kills" bacteria. so it's normal to have this result

In most of the cases MBC values are higher than MIC values. In some case it will be equal but not less.

I agree with the above contributors. MBC is expected to be higher than or equal to MIC - definitely not less than MIC. The closer in value the MBC is to MIC the more bactericidal a drug is considered to be; if the MIC of an agent is also its MBC that would suggest perfectly ‘cidal’ activity.

It is also not surprising to note that you had a confusing result with your extract. This is because plant extracts often show confusing results on tube dilution technique, compared with pure compounds.

Wonderful!

Very clear interpretation!.

Thank you so much Prof. Emele.

Truly yours

Emad

MBC ≥MIC 

This is a normal situation, since the MIC was defined as the lowest concentration of extracts at which microorganisms showed no visible growth, but MBC is defined as the lowest concentration of the extracts at which 99.9 % of inoculated microorganisms were killed.Therefore, the MBC is always equal or higher than MIC.

In my current research work, on a plant extract, MBC is always equal or higher than MIC because of MIC is showed the concentration of drug i. e. Plant extracts which showed that there is no growth of a particular microorganism but MBC showed the total bactericidal action of lowest concentration of any Drug  in which microorganisms were killed.

It is logical that MBC is either equal or more than MIC

MIC it is minimal inhibitory concentration , just inhibitory while MBC minimal bacteriocidal concentration so may be your cons. just inhibit the growth of microorganism while the cons. which kill the organism iits more higher from the MIC

good luck

Ya of course that would be.

MBCs are normally expected to be higher than or equal to MIC. If the two  values are  equal it means  the agent is essentially microbicidal.

But plant crude extracts often give confusing results,  especially if tested by broth dilution method - possibly due to spontaneous sedimentation of the extract.

Based on my experience, agar dilution technique gives the most reliable  results.

One reason could be that the dilution may have resulted in the release of the main antimicrobial agent present in the crude extract. I mean inhibitory substance to the antimicrobial agent might have been diluted more at MIC than at MBC.

i agreed with Mahboob Hossain opinion.

MIC= Can inhibit Bacteria ( ~ 90%)

MBC= Can kill Bacteria ( ~ 99%)

MIC= MBC≥ MIC

yeah, MBC will be obviously higher than MIC. your results are in right direction.

Definitely , MBC will be greater than MIC for a particular pathogen.

MBC will be always equal to or greater than MIC

MBC > or = MICis surely in order

That is in order as MBC can be equal to or greater than MIC

The possible release of the main antimicrobial agent present in a crude extract, due to dilution (as suggested by Mahboob Hossain), will affect the MIC as much as the MBC.

Therefore, MBC is always equal to or greater than the MIC.

That's correct. MBC as the Minimal Bactericidal Concentration is greater that MIC which is the Minimal Inhibitory Concentration of antibiotic .

MBC will be always higher or equal to MIC. It is better you should do it in microtiter plate, where you can check many concentrations of your drug together.

Hello

Your results explaine by the redistance of S.aureus. and the the nature of the tested. Compounds

Hi,

MBC always is higher than MIC and sometimes is equal with MIC.

Antibacterial agents are usually evaluated as bactericidal if the MBC is less than 4 times the MIC. Your plant extract is bactericidal.

MBC is not expected to be less than the MIC.

The level of drug dilution in a test tube should not be confused with the drug concentration in the tube; for example, while ½ dilution is a lower dilution compared with ¼ dilution, the drug concentration of the ½ dilution is higher than that of the ¼ dilution.

For instance, if you have ten test tubes of the following dilution series: 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256, 1/512, 1/1024, containing the following corresponding drug concentrations (µg/ml): 200, 100, 50, 25, 12.5, 6.25, 3.12, 1.56, 0.78, and 0.39, respectively; 1/1024 represents the highest dilution, while 1/2 represents the lowest. If the MIC is 3.12µg/ml, then the corresponding dilution (1/128 dilution) is the minimum inhibitory dilution. In that case, MBC would be 3.12µg/ml or greater (ie. either 3.12, or 6.25 or 12.5 ……. etc (µg/ml), whereas the minimum bactericidal dilution would be 1/128 or less (ie. 1/64, or 1/32, or 1/16 ………. etc).

While minimum bactericidal concentration (MBC) of a drug is usually equal to or greater than the minimum inhibitory concentration (MIC) of the drug, the minimum bactericidal dilution of a drug is, on the contrary, equal to or less than the minimal bactericidal dilution.

Confusing the available concentration with the degree of dilution can lead to interpretation error.

Sir, the result obtained is not a variation from the order, I suggest literature will provide more information.