Abstract
Due to slow diagnostics, physicians must optimize antibiotic therapies based on clinical evaluation of patients without specific information on causative bacteria. We have investigated metabolomic analysis of blood for the detection of acute bacterial infection and early differentiation between ineffective and effective antibiotic treatment. A vital and timely therapeutic difficulty was thereby addressed: the ability to rapidly detect treatment failures because of antibiotic-resistant bacteria. Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) were used in vitro and for infecting mice, while natural MSSA infection was studied in humans. Samples of bacterial growth media, the blood of infected mice and of humans were analyzed with combined Gas Chromatography/Mass Spectrometry. Multivariate data analysis was used to reveal the metabolic profiles of infection and the responses to different antibiotic treatments. In vitro experiments resulted in the detection of 256 putative metabolites and mice infection experiments resulted in the detection of 474 putative metabolites. Importantly, ineffective and effective antibiotic treatments were differentiated already two hours after treatment start in both experimental systems. That is, the ineffective treatment of MRSA using cloxacillin and untreated controls produced one metabolic profile while all effective treatment combinations using cloxacillin or vancomycin for MSSA or MRSA produced another profile. For further evaluation of the concept, blood samples of humans admitted to intensive care with severe sepsis were analyzed. One hundred thirty-three putative metabolites differentiated severe MSSA sepsis (n = 6) from severe Escherichia coli sepsis (n = 10) and identified treatment responses over time. Combined analysis of human, in vitro, and mice samples identified 25 metabolites indicative of effective treatment of S. aureus sepsis. Taken together, this study provides a proof of concept of the utility of analyzing metabolite patterns in blood for early differentiation between ineffective and effective antibiotic treatment in acute S. aureus infections.
Highlights
The intensive use of antibiotics for 60 years has resulted in a challenge of global scale - the increasing rates of antibiotic resistance among bacteria
To evaluate if efficiency of antibiotic treatment can be measured by metabolic profiling of bacterial growth in vitro, we initially studied methicillin resistant and sensitive S. aureus (MRSA and methicillin-sensitive S. aureus (MSSA), respectively) grown in presence or absence of cloxacillin or vancomycin
Overnight cultures of clinical isolates of Methicillin resistant Staphylococcus aureus (MRSA) and MSSA were diluted to OD600,0.02 in 80% human heat inactivated serum with 20% LB and grown to OD600,0.2 when each strain was subdivided into three separate cultures; non-treated bacteria for continued growth, vancomycin treated bacteria, and cloxacillin treated bacteria
Summary
The intensive use of antibiotics for 60 years has resulted in a challenge of global scale - the increasing rates of antibiotic resistance among bacteria. We are running out of treatment options for many infections [1,2,3]. Methicillin resistant Staphylococcus aureus (MRSA) is a prime example of a common, global, and potentially dangerous pathogen that has acquired antibiotic resistance [2]. The current situation is a reminder of past times when little could be done to combat a S. aureus infection except surgical drainage of infected body sites. MRSA is resistant to all members of the b-lactam class of antibiotics including all penicillins, cephalosporins and carbapenems, thereby disarming all previous mainstay treatments against. MRSA is frequently resistant to other common antimicrobial agents [4]
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