Volume 16, Supplement 1, 2008
Review
Intra-abdominal infections: definitions and classification
Menichetti Francesco,
Sganga Gabriele
Intra-abdominal infections (IAIs) represent a wide variety of pathological conditions that involve lesions of all the intra-abdominal organs. They include both inflammation of single organs and any sort of peritonitis (primary, secondary, tertiary), where the severity of the disease often depends from the extension of the inflammation ((local or diffuse peritonitis). They include also the intraperitoneal, retroperitoneal and parenchymal abscesses. The aim of current review is that of analyse the current definitions and classifications of intra-abdominal infections.
Intra-abdominal infections: etiology, epidemiology, microbiological diagnosis and antibiotic resistance issues
Nicoletti Giuseppe,
Nicolosi Daria,
Rossolini Gian Maria,
Stefani Stefania
Intra-abdominal infections (IAIs) are commonly encountered in clinical practice. The etiology of these infections, often polymicrobial in nature, can be variable and usually includes organisms derived from the gut microbiota. In community-acquired IAIs enterobacteria predominate (mostly Escherichia coli) in combination with anaerobes (mostly Bacteroides fragilis). In nosocomial IAIs, which can complicate abdominal surgery, other pathogens can also play a role, such as Pseudomonas aeruginosa, Acinetobacter baumannii, Staphylococcus aureus, Enterococcus spp. e Candida spp. Diagnostic microbiology of IAIs is complex and plays a relevant role especially in some situations (e. g. presence of foreign bodies, potential presence of resistant or uncommon pathogens, nosocomial infections in subjects with risk factors). Antibiotic resistance issues are currently encountered in most pathogenic species causing IAIs. Resistance affects all major classes of antimicrobial agents, often involving multiple classes and resulting in complex resistance phenotypes for which only a very limited number of drugs remain active.
Diagnosis of intra-abdominal infections: clinical findings and imaging
Emmi Vincenzo,
Sganga Gabriele
Abdominal sepsis carries a high morbidity and mortality. Intraabdominal infectious complications are one of the most common infectious etiologies seen in critically ill patients. Approximately 30% of patients admitted to an ICU with intra-abdominal infection succumb to their illness, and when peritonitis arises as a complication of a previous surgical procedure, or recurs during ICUadmission, mortality rates exceed 50%. Thus early detection and treatment is essential to minimize patient complications.
Critically ill patients are often clinically non valuable due to distracting injuries, respiratory failure, obtundation, or other pathology. Even when patients can be examined, the clinical exam is frequently unreliable and/or misleading. The diagnostic approach to identify abdominal problems will differ depending upon the hemodynamic stability of the patient. Patients who have low systolic blood pressures, who are pressor-dependent, may be too unstable to undergo studies that require trips away from the ICU or emergency department. Intra-abdominal pathology may be detected by ultrasound or diagnostic peritoneal lavage (DPL).
When critically ill patients are stable enough to undergo some diagnostic evaluation of their abdomen the approach is somewhat simpler. Overall, computerized tomography (CT) is the imaging modality of choice for most intra-abdominal processes. For diagnosis of intra-abdominal conditions using CT scanning it is optimal if patients receive both oral and intravenous contrast.
An exception to the use of CT scanning is evaluation of suspected biliary pathology, which is best imaged by ultrasound. It will identify cholecystitis with or without calculus and may show changes in the gallbladder or common bile duct associated with biliary obstruction.
Pharmacological rationale for choice of antibiotics for intra-abdominal infections
Mazzei Teresita,
Novelli Andrea
The pharmacodynamic and pharmacokinetic characteristics of antimicrobial agents are the two fundamental pharmacological components which provide a rationale for the choice of therapy for intra-abdominal infections, and especially serious infections. The most important PK-PD parameters are well known which can increase therapeutic efficacy. Antimicrobial agents can be subdivided into categories based on whether their activity is dependent on concentration or exposure time. Therefore, a correct dosing regimen for the time-dependent molecules (i.e. beta-lactams, linezolid, tigecycline) should prolong the maximum exposure time to maintain serum levels over the minimum inhibitory concentration (MIC). The concentration-dependent molecules, on the other hand, which include aminoglycosides and fluoroquinolones, should be given in order to reach maximum concentrations, since they are bactericidal in direct proportion to their concentrations and possess a prolonged post-antibiotic effect.
Intra-abdominal infections: analysis of current guidelines
Esposito Silvano,
Leone Sebastiano,
Carosi Giampiero
Intra-abdominal infections (IAIs) are a frequent cause of mobility and mortality. These infections can be caused by a wide variety of microorganisms, including both aerobes and anaerobes, and are often polymicrobial. Several studies observed that mortality depends on initiating early appropriate antimicrobial therapy. Moreover, the inappropriate choice of initial antibiotic therapy result in a longer hospital stay and higher costs of hospitalization compared with appropriate initial antibiotic therapy. The aim of current review is that of summarize the recommendations of several guidelines on the management of IAIs.
New options for treatment of intra-abdominal infections: tigecycline
Menichetti Francesco
Tigecycline is a new antimicrobial agent; it is the first in a new class of antibiotics, the glycylcyclines, with properties conferring the ability to overcome many common resistance mechanisms, thus allowing its use for many serious and life-threatening infections for which the use of other antibiotics is no longer appropriate. It has a wide antibacterial spectrum including most methicillin-resistant Staphylococci, vancomycin-resistant Enterococci, ESBL-producing Gram negative bacteria, and other MDR Gram negative bacteria such as Acinetobacter, and Stenotrophomonas. It has good antibacterial activity also against anaerobes and atypical pathogens.
Tigecycline is available only as parenteral formulation. It has a high volume of distribution (>10 l/kg), and long half-life (36 hrs). It has been approved in USA and Europe for the treatment of complicated skin and soft tissue infections and for the complicated community acquired intraabdominal infections. Phase III studies for treatment of community acquired and nosocomial acquire pneumonia, and sepsis sustained by multi-drugresistant pathogens are ongoing.
Antimicrobial management of intra-abdominal infections
Concia Ercole,
Viscoli Claudio
Antimicrobial therapy of intra-abdominal infection should consider its aetiology, which is generally polimicrobial, and its location with the aim of selecting the most suitable antimicrobial agents not only according to its spectrum but also to its pharmacokinetics profile
Currently, both monotherapy and association therapy can be used, thanks the availability of newer drugs characterized by a wide range of antimicrobial activity both against aerobes and anaerobes.
Antibiotic choice and duration therapy vary also according to the infection severity .
Hospital management of complicated intra-abdominal infections: pharmacoeconomic evaluations
Eandi Mario
Due to their high incidence and large resource consumption, complicated intra-abdominal infections (cIAIs) represent a heavy burden for the Italian National Health System (NHS) and the Italian society, with estimated annual costs of 1,5 and 3 billions Euro, respectively.
The different strategies, monotherapy or antibiotic combinations, indicated for treating cIAIs induce significantly different acquisition and administration costs but substantially equivalent therapeutic results, with average clinical effectiveness rates of 70-80%. This apparent equivalence among different antibiotic protocols presumably depends on the widespread trend to individualize the therapeutic strategy according to the clinical severity and the community or nosocomial origin of cIAIs, as well as on some degree of non-appropriateness when empirically choosing a first-line antibiotic.
The average cost for the nosocomial management of cIAI patients depends on several factors: posologies and antibiotic drug acquisition and administration costs, days of antibiotic therapy, mix of antibiotic schedules, rates of the therapeutic failures that induce further drug consumption, prolong hospitalization and often require re-intervention and ICU utilization.
The introduction in the therapeutic arsenal of a new antibiotic like tigecycline leads to a mild increase of the average antibiotic acquisition and treatment costs per patient: this increase is proportional to the percentage of patients treated with the new antibiotic.
According to a decisional model, implemented on international outcome data and Italian costs, the mean cost for first-line antibiotic acquisition and the mean cost for first- and second-line antibiotic treatment represent respectively only 2% and 8% of the mean overall hospitalization cost. The mean hospitalization cost estimated by the model is noticeably higher than the mean value of DRG tariffs presumably reimbursed by the Italian NHS to hospitals for cIAI-related hospitalizations.
Greater overall efficiency levels in the nosocomial management of cIAI patients are achievable mainly through the reduction of non-appropriateness rates in first line antibiotic choices and better treatment individualization, possible if the physician is offered the choice of as many valid therapeutic options as possible, in order to guarantee the best cure chances to each patient.
