Experimental aspects of intraabdominal abscess

Lung abscess caused by Streptococcus pneumoniae serotype 6B

Lung abscess has been considered to be a rare complication of pneumococcal infection, and most cases are reported to be Streptococcus pneumoniae serotype 3. A 67-year-old man presented with fever and was diagnosed to have lung abscess caused by S. pneumoniae serotype 6B. The minimal inhibitory concentration (MIC) of penicillin for the isolate was 1 μg/mL. He was treated with high-dose intravenous sulbactam/ampicillin as definitive therapy based on susceptibility testing for S. pneumoniae and recovered successfully without surgical intervention. S. pneumoniae serotype 6B can cause lung abscess.

A medicinal chemists' guide to the unique difficulties of lead optimization for tuberculosis

Tuberculosis is a bacterial disease that predominantly affects the lungs and results in extensive tissue pathology. This pathology contributes to the complexity of drug development as it presents discrete microenvironments within which the bacterium resides, often under conditions where replication is limited and intrinsic drug susceptibility is low. This consolidated pathology also results in impaired vascularization that limits access of potential lead molecules to the site of infection. Translating these considerations into a target-product profile to guide lead optimization programs involves implementing unique in vitro and in vivo assays to maximize the likelihood of developing clinically meaningful candidates.

The Microbiology of Community-acquired Peritonitis in Children

BACKGROUND

microbiologic data are lacking regarding pediatric community-acquired peritonitis (CAP).

METHODS

we conducted a 2-year retrospective single center study. Consecutive children undergoing CAP surgery were included. Microbiology and antimicrobial susceptibility of peritoneal isolates were analyzed.

RESULTS

a total of 70 children from 3 months to 14 years of age were included. A total of 123 bacterial isolates were analyzed. Escherichia coli was the predominant aerobic organism (51% of isolates); 54.8% were susceptible to amoxicillin whereas 90.3% were susceptible to amoxicillin-clavulanate. Anaerobes accounted for 29% of isolates, and 94.3% of strains were susceptible to amoxicillin-clavulanate and 68.5% were susceptible to clindamycin. Pseudomonas aeruginosa was present in 6% of isolates and in 10% of children. The presence of E. coli resistant to amoxicillin or to amoxicillin-clavulanate was the only independent risk factor associated with postoperative peritonitis.

CONCLUSION

microbiology of pediatric CAP is similar to adult CAP with a predominancy of E. coli and anaerobes. P. aeruginosa in peritoneal samples had no apparent influence on the outcome.

Clinical pharmacology and lesion penetrating properties of second- and third-line antituberculous agents used in the management of multidrug-resistant (MDR) and extensively-drug resistant (XDR) tuberculosis

Failure of first-line chemotherapy to cure tuberculosis (TB) patients occurs, in part, because of the development of resistance to isoniazid (INH) and rifampicin (RIF) the two most sterilizing agents in the four-drug regimen used to treat primary infections. Strains resistant to both INH and RIF are termed multidrug-resistant (MDR). Treatment options for MDR patients involve a complex array of twenty different drugs only two classes of which are considered to be highly effective (fluoroquinolones and aminoglycosides). Resistance to these two classes results in strains known as extensively drug-resistant (XDR) and these types of infections are becoming increasingly common. Many of the remaining agents have poorly defined pharmacology but nonetheless are widely used in the treatment of this disease. Several of these agents are known to have highly variable exposures in healthy volunteers and little is known in the patients in which they must be used. Therapeutic drug monitoring (TDM) is infrequently used in the management of MDR or XDR disease yet the clinical pharmacokinetic studies that have been done suggest this might have a large impact on disease outcome. We review what is known about the pharmacologic properties of each of the major classes of second- and third-line antituberculosis agents and suggest where judicious use of TDM would have the maximum possible impact. We summarize the state of knowledge of drug-drug interactions (DDI) in these classes of agents and those that are currently in clinical trials. Finally we consider what little is known about the ability of TB drugs to reach their ultimate site of action--the interior of a granuloma by penetrating the diseased lung area. Careful consideration of the pharmacology of these agents is essential if we are to avoid further fueling the growing epidemic of highly drug-resistant TB and critical in the development of new antituberculosis drugs.

Antibiotic abscess penetration: fosfomycin levels measured in pus and simulated concentration-time profiles

The present study was performed to evaluate the ability of fosfomycin, a broad-spectrum antibiotic, to penetrate into abscess fluid. Twelve patients scheduled for surgical or computer tomography-guided abscess drainage received a single intravenous dose of 8 g of fosfomycin. The fosfomycin concentrations in plasma over time and in pus upon drainage were determined. A pharmacokinetic model was developed to estimate the concentration-time profile of fosfomycin in pus. Individual fosfomycin concentrations in abscess fluid at drainage varied substantially, ranging from below the limit of detection up to 168 mg/liter. The fosfomycin concentrations in pus of the study population correlated neither with plasma levels nor with the individual ratios of abscess surface area to volume. This finding was attributed to highly variable abscess permeability. The average concentration in pus was calculated to be 182 +/- 64 mg/liter at steady state, exceeding the MIC(50/90)s of several bacterial species which are commonly involved in abscess formation, such as streptococci, staphylococci, and Escherichia coli. Hereby, the exceptionally long mean half-life of fosfomycin of 32 +/- 39 h in abscess fluid may favor its antimicrobial effect because fosfomycin exerts time-dependent killing. After an initial loading dose of 10 to 12 g, fosfomycin should be administered at doses of 8 g three times per day to reach sufficient concentrations in abscess fluid and plasma. Applying this dosing regimen, fosfomycin levels in abscess fluid are expected to be effective after multiple doses in most patients.

Principles of Antibiotic Penetration into Abscess Fluid

Although drainage is considered the gold standard in abscess treatment, abscesses of different sizes and locations have been successfully cured by means of antibiotic treatment alone. The penetration of an antibiotic into an encapsulated purulent lesion is limited and highly dependent on the degree of abscess maturation. In fact, in vivo pharmacokinetic data demonstrate that substantial antibiotic concentrations can be reached within abscesses in humans and animals, provided the choice of an appropriate agent and an optimal dosing regimen. However, the efficacy of antibiotics in pus may be hampered by various factors like low pH, protein binding and degradation by bacterial enzymes. This article provides a comprehensive review on conservative abscess treatment, presenting clinical data on success rates of antibiotic therapy. Antibiotic concentrations measured in abscesses of humans and animals are outlined, and theoretical considerations on the understanding of pharmacokinetics and efficacy of antibiotics in abscesses are discussed.

Intrauterine bacterial findings in postpartum cows with retained fetal membranes

Eleven Swedish postpartum cows with retained fetal membranes (RFM) were studied to determine the intrauterine bacterial flora. Bacteriological examination was performed from twice weekly uterine biopsies. A total of 161 biopsies were collected during the first 8 weeks postpartum of which 82 (50.9%) were found with bacterial growth. Seventy-one of the 82 bacteria-positive biopsies (86.6%) showed mixed infections whereas the remaining 11 (13.4%) were pure cultures. Generally, a total of 322 isolates belonging to 12 different genera of bacteria, 6 facultative and 6 obligate anaerobic pathogens were identified. Mixed infections were most frequent for Actinomyces pyogenes together with obligate anaerobic bacteria, especially Bacteroides levii/spp. and Fusobacterium necrophorum. All of the studied cows had an infection that involved the first two genera of bacteria, whereas F. necrophorum was found in 8 of the 11 animals. The present work suggests that a possible pathogenic synergism between A. pyogenes and the two main Gram-negative anaerobes might have caused early endometritis and/or persistent infection.

Penetration of prophylactic antibiotics into peritoneal fluid

This study evaluates the penetration of cephalosporins into the peritoneal fluid. Forty-six patients scheduled for abdominal surgery were randomized into three groups. On call to the operating room each patient was given a single 1 g dose of cefazolin, cefuroxime, or ceftazidime. Samples of the peritoneal fluid and blood were simultaneously obtained immediately after opening the peritoneal cavity. The mean serum cefazolin concentration was the highest. High peritoneal fluid levels of all three antibiotics were found; however, the antibacterial activity against common intestinal pathogens varied significantly. Cefazolin is the only study drug that possesses marginal in vitro activity against Streptococcus faecalis, a species generally considered resistent to cephalosporins. This study suggests that prophylactic second and third generation cephalosporins are not superior to cefazolin.

Bacteroides fragilis: current susceptibilities, mechanisms of drug resistance, and principles of antimicrobial therapy

The Bacteroides fragilis group of organisms includes the most clinically important anaerobic bacteria. Optimal therapy of infections in which these organisms are involved includes adequate and timely surgical drainage of all collections, debridement of necrotic tissue, optimal nutritional support, and administration of appropriate empiric antibiotics to cover both the aerobic and anaerobic bacterial components of these mixed infections. Special attention must be paid to the B. fragilis group because of its high rate of resistance to many of the commonly used antibiotics. Of the currently available beta-lactam antibiotics, piperacillin has the lowest rate of resistance. Successful antimicrobial agents include clindamycin, chloramphenicol, and metronidazole plus an aminoglycoside. Piperacillin, cefoxitin, and moxalactam can be used with an aminoglycoside or alone if no resistant organisms are revealed on culture and susceptibility testing. Beta-lactam-based regimens are potentially less toxic and may be less costly than those that contain one or more non-beta-lactam antibiotics.

Acute enteric sepsis: bacteriology and antibiotic cover

Most cases of enteric sepsis are caused by both aerobic and anaerobic organisms which form the normal flora of the mouth and lower gastrointestinal tract. This flora is extremely variable and subject to change due to disease and antimicrobial treatment. Bacteriological investigation of patients with severe enteric sepsis is important and should be undertaken before antibiotic treatment is commenced. The choice of antibiotics depends on the nature of the infection and its location. Initially they should be given in maximum dosage. If polymicrobial infection is suspected both aerobes and anaerobes should be covered to prevent bacteraemic shock and abscess formation. If abscesses have formed or the patient fails to respond to appropriate antibiotics, surgical exploration and drainage remain the treatment of choice. Antibiotics often fail to eradicate organisms from established abscesses and are responsible for some serious complications.