Baraka, M.

Electronic Sumy State University Institutional Repository

SUSCEPTIBILITY OF STAPHYLOCOCAL BIOFILMS TO MULTIPLE COMBINATION OF ANTIMICROBIALS Baraka M., the 4th–year student Scientific supervisor – professor A. G. Dyachenko Sumy State University, department of hygiene and ecology with course of microbiology, virology and immunology  Background. Staphylococcus epidermidis and Staphylococcus aureus are the most common pathogens associated with infections of surgical implants and other prosthetic devices. These organisms have been shown to form in vivo biofilms on implanted devices. Standardized susceptibility testing fails to predict in vivo resistance of Staphylococcus spp.-related infections to antimicrobials. Antimicrobial therapy is guided by the results obtained from conventional antimicrobial testing of planktonic (free-growing) bacteria. However, this may not necessarily reflect the susceptibilities of these same bacteria when they are grown as biofilms. Biofilm associated bacteria are 100 to 1,000 times less susceptible to antibiotics than are planktonic bacteria, and agents active against planktonic bacteria, but not against biofilms, fail to cure patients with infected prostheses. The objective of this study was to compare susceptibilities of planktonic and biofilm-grown bacteria to single antibiotics and to combinations of antibiotics in order to identify antibiotic combinations that were effective against staphylococci retrieved from nosocomial infections. It was hypothesized that biofilm-grown bacteria would demonstrate greater resistance to single and combination antibiotics compared to the same bacteria grown under planktonic conditions. Bacterial strains. In this work Staphylococci isolates associated with hospital infections were obtained from the clinical microbiology laboratories of Kharkov city (usually, from the bacterial museum of I. Mechnikov memorial Inst.Microbiol.Immunol.). Preference was given to isolates recovered from the local site of infection or the device itself. Blood culture isolates from patients with clinically defined line sepsis were also used. Staphylococci were identified by colonial morphology, Gram stain, and coagulase testing. Methicillin-resistant S. aureus (MRSA) was further confirmed by coagulase testing and growth on oxacillin salt agar screen plate. In total, 10 isolates of S. epidermidis, 4 isolates of methicillin-sensitive S. aureus (MSSA), and 6 isolates of methicillin-resistant S. aureus (MRSA) were obtained and studied. Antibiotics. Antibiotics tested were azithromycin (Pfizer, Zetamax), cefazolin (Arterium), ciprofloxacin (Arterium), fusidic acid (Arterium), gentamicin (KMP), linezolid (Pfizer), teicoplanin (Aventis Pharma), rifampin (KMP), and vancomycin (Sigma). Interpretation criteria for susceptibility testing were based on NCCLS, now CLSI guidelines. Results. We assessed agents and combinations of antimicrobials against isolates of S. epidermidis and S. aureus retrieved from medical devices and instruments. Isolates were grown planktonically and as biofilms. Biofilm cultures of the organisms were found to be much more resistant to inhibitory and bactericidal effects of single and combination antibiotics than planktonic cultures (P < 0.001). Rifampin was the most common constituent of antibiotic combinations active against staphylococcal biofilms. Other frequently effective antimicrobials were vancomycin and fusidic acid.  Conclusion. Susceptibility testing involving biofilm-associated bacteria suggests new options for combination antibiotic therapy.   

Susceptibility of staphylococal biofilms to multiple combination of antimicrobials

SocioEconomic Challenges Journal (Sumy State University)

SUSCEPTIBILITY OF STAPHYLOCOCAL BIOFILMS TO MULTIPLE COMBINATION OF 
ANTIMICROBIALS 
Baraka M., the 4
th–year student 
Scientific supervisor – professor A. G. Dyachenko 
Sumy State University, department of hygiene and ecology with course of microbiology, virology and immunology 
 
Background. Staphylococcus epidermidis and Staphylococcus aureus are the most common pathogens 
associated with infections of surgical implants and other prosthetic devices. These organisms have been shown to form 
in vivo biofilms on implanted devices. Standardized susceptibility testing fails to predict in vivo resistance of 
Staphylococcus spp.-related infections to antimicrobials. Antimicrobial therapy is guided by the results obtained from 
conventional antimicrobial testing of planktonic (free-growing) bacteria. However, this may not necessarily reflect the 
susceptibilities of these same bacteria when they are grown as biofilms. Biofilm associated bacteria are 100 to 1,000 
times less susceptible to antibiotics than are planktonic bacteria, and agents active against planktonic bacteria, but not 
against biofilms, fail to cure patients with infected prostheses. 
The objective of this study was to compare susceptibilities of planktonic and biofilm-grown bacteria to single 
antibiotics and to combinations of antibiotics in order to identify antibiotic combinations that were effective against 
staphylococci retrieved from nosocomial infections. It was hypothesized that biofilm-grown bacteria would demonstrate 
greater resistance to single and combination antibiotics compared to the same bacteria grown under planktonic 
conditions. 
Bacterial strains. In this work Staphylococci isolates associated with hospital infections were obtained from 
the clinical microbiology laboratories of Kharkov city (usually, from the bacterial museum of I. Mechnikov memorial 
Inst.Microbiol.Immunol.). Preference was given to isolates recovered from the local site of infection or the device itself. 
Blood culture isolates from patients with clinically defined line sepsis were also used. Staphylococci were identified by 
colonial morphology, Gram stain, and coagulase testing. Methicillin-resistant S. aureus (MRSA) was further confirmed 
by coagulase testing and growth on oxacillin salt agar screen plate. In total, 10 isolates of S. epidermidis, 4 isolates of 
methicillin-sensitive S. aureus (MSSA), and 6 isolates of methicillin-resistant S. aureus (MRSA) were obtained and 
studied. 
Antibiotics. Antibiotics tested were azithromycin (Pfizer, Zetamax), cefazolin (Arterium), ciprofloxacin 
(Arterium), fusidic acid (Arterium), gentamicin (KMP), linezolid (Pfizer), teicoplanin (Aventis Pharma), rifampin 
(KMP), and vancomycin (Sigma). Interpretation criteria for susceptibility testing were based on NCCLS, now CLSI 
guidelines. 
Results. We assessed agents and combinations of antimicrobials against isolates of S. epidermidis and S. 
aureus retrieved from medical devices and instruments. Isolates were grown planktonically and as biofilms. Biofilm 
cultures of the organisms were found to be much more resistant to inhibitory and bactericidal effects of single and 
combination antibiotics than planktonic cultures (P < 0.001). Rifampin was the most common constituent of antibiotic 
combinations active against staphylococcal biofilms. Other frequently effective antimicrobials were vancomycin and 
fusidic acid.  
Conclusion. Susceptibility testing involving biofilm-associated bacteria suggests new options for combination 
antibiotic therapy. 
 
 


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Susceptibility of staphylococal biofilms to multiple combination of antimicrobials

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Electronic Sumy State University Institutional Repository

SocioEconomic Challenges Journal (Sumy State University)