Enlargement of the WHO international repository for platelet transfusion-relevant bacteria reference strains.

BACKGROUND AND OBJECTIVES: Interventions to prevent and detect bacterial contamination of platelet concentrates (PCs) have reduced, but not eliminated the sepsis risk. Standardized bacterial strains are needed to validate detection and pathogen reduction technologies in PCs. Following the establishment of the First International Reference Repository of Platelet Transfusion-Relevant Bacterial Reference Strains (the 'repository'), the World Health Organization (WHO) Expert Committee on Biological Standardisation (ECBS) endorsed further repository expansion. MATERIALS AND METHODS: Sixteen bacterial strains, including the four repository strains, were distributed from the Paul-Ehrlich-Institut (PEI) to 14 laboratories in 10 countries for enumeration, identification and growth measurement on days 2, 4 and 7 after low spiking levels [10-25 colony-forming units (CFU)/PC bag]. Spore-forming (Bacillus cereusPEI-B-P-07-S, Bacillus thuringiensisPEI-B-P-57-S), Gram-negative (Enterobacter cloacaePEI-B-P-43, Morganella morganiiPEI-B-P-74, PEI-B-P-91, Proteus mirabilisPEI-B-P-55, Pseudomonas fluorescensPEI-B-P-77, Salmonella choleraesuisPEI-B-P-78, Serratia marcescensPEI-B-P-56) and Gram-positive (Staphylococcus aureusPEI-B-P-63, Streptococcus dysgalactiaePEI-B-P-71, Streptococcus bovisPEI-B-P-61) strains were evaluated. RESULTS: Bacterial viability was conserved after transport to the participating laboratories with one exception (M. morganiiPEI-B-P-74). All other strains showed moderate-to-excellent growth. Bacillus cereus, B. thuringiensis, E. coli, K. pneumoniae, P. fluorescens, S. marcescens, S. aureus and S. dysgalactiae grew to >106 CFU/ml by day 2. Enterobacter cloacae, P. mirabilis, S. epidermidis, S. bovis and S. pyogenes achieved >106 CFU/ml at day 4. Growth of S. choleraesuis was lower and highly variable. CONCLUSION: The WHO ECBS approved all bacterial strains (except M. morganiiPEI-B-P-74 and S. choleraesuisPEI-B-P-78) for repository enlargement. The strains were stable, suitable for spiking with low CFU numbers, and proliferation was independent of the PC donor.

Fulminant endocarditis and disseminated infection caused by carbapenem-resistant Acinetobacter baumannii in a renal-pancreas transplant recipient.

Acinetobacter baumannii is an important cause of healthcare-associated infections, and is particularly problematic among patients who undergo organ transplantation. We describe a case of fulminant sepsis caused by carbapenem-resistant A. baumannii harboring the blaOXA-23 carbapenemase gene and belonging to international clone II. This isolate led to the death of a patient 6 days after simultaneous kidney-pancreas transplantation. Autopsy findings revealed acute mitral valve endocarditis, myocarditis, splenic and renal emboli, peritonitis, and pneumonia. This case highlights the severe nature of certain A. baumannii infections and the vulnerability of transplanted patients to the increasingly intractable "high-risk" clones of multidrug-resistant organisms.

An international, prospective, multicenter evaluation of the combination of AdvanDx Staphylococcus QuickFISH BC with mecA XpressFISH for detection of methicillin-resistant Staphylococcus aureus isolates from positive blood cultures.

Sepsis caused by Staphylococcus aureus is a major health problem worldwide. Better outcomes are achieved when rapid diagnosis and determination of methicillin susceptibility enable early optimization of antimicrobial therapy. Eight large clinical laboratories, seven from the United States and one from Scotland, evaluated the combination of the Staphylococcus QuickFISH BC and the new mecA XpressFISH assay (both AdvanDx, Woburn, MA, USA) for the detection of methicillin-resistant S. aureus in positive blood cultures. Blood cultures flagged as positive by automated blood culture instruments and demonstrating only Gram-positive cocci in clusters on Gram stain were tested by QuickFISH, a 20-min assay. If only S. aureus was detected, mecA XpressFISH testing followed. The recovered S. aureus isolates were tested by cefoxitin disk diffusion as the reference method. The QuickFISH assay results were concordant with the routine phenotypic testing methods of the testing laboratories in 1,211/1,221 (99.1%) samples and detected 488/491 S. aureus organisms (sensitivity, 99.4%; specificity, 99.6%). Approximately 60% of the samples (730) contained coagulase-negative staphylococci or nonstaphylococci as assessed by the QuickFISH assay and were not tested further. The 458 compliant samples positive exclusively for S. aureus by the QuickFISH assay were tested by the mecA XpressFISH assay, which detected 209 of 211 methicillin-resistant S. aureus organisms (sensitivity, 99.1%; specificity, 99.6%). The mecA XpressFISH assay also showed high reproducibility, with 534/540 tests performed by 6 operators over 5 days achieving reproducible results (98.9% agreement). The combination of the Staphylococcus QuickFISH BC and mecA XpressFISH assays is sensitive, specific, and reproducible for the detection of methicillin-resistant S. aureus and yields complete results in 2 h after the blood culture turns positive.

Disseminated Bacillus Calmette-Guérin (BCG) infection following allogeneic hematopoietic stem cell transplant in a patient with Bare Lymphocyte Syndrome type II.

We describe the first case, to our knowledge, of disseminated Mycobacterium bovis Bacillus Calmette-Guérin infection in a child with Bare Lymphocyte Syndrome type II after undergoing hematopoietic stem cell transplantation (HSCT). The patient presented 30 days post HSCT with fever and lymphadenitis. Lymph node, blood, and gastric aspirates were positive for M. bovis. The patient received a prolonged treatment course with a combination of isoniazid, levofloxacin, and ethambutol. Her course was further complicated by granulomatous lymphadenitis and otitis media associated with M. bovis that developed during immune suppression taper and immune reconstitution. Ultimately, the patient recovered fully, in association with restoration of immune function, and has completed 12 months of therapy.

Serratia marcescens strains implicated in adverse transfusion reactions form biofilms in platelet concentrates and demonstrate reduced detection by automated culture.

BACKGROUND AND OBJECTIVES: Serratia marcescens is a gram-negative bacterium that has been implicated in adverse transfusion reactions associated with contaminated platelet concentrates. The aim of this study was to investigate whether the ability of S. marcescens to form surface-attached aggregates (biofilms) could account for contaminated platelet units being missed during screening by the BacT/ALERT automated culture system. MATERIALS AND METHODS: Seven S. marcescens strains, including biofilm-positive and biofilm-negative control strains and five isolates recovered from contaminated platelet concentrates, were grown in enriched Luria-Bertani medium and in platelets. Biofilm formation was examined by staining assay, dislodging experiments and scanning electron microscopy. Clinical strains were also analysed for their ability to evade detection by the BacT/ALERT system. RESULTS: All strains exhibited similar growth in medium and platelets. While only the biofilm-positive control strain formed biofilms in medium, this strain and three clinical isolates associated with transfusion reactions formed biofilms in platelet concentrates. The other two clinical strains, which had been captured during platelet screening by BacT/ALERT, failed to form biofilms in platelets. Biofilm-forming clinical isolates were approximately three times (P<0·05) more likely to be missed by BacT/ALERT screening than biofilm-negative strains. CONCLUSION: S. marcescens strains associated with transfusion reactions form biofilms under platelet storage conditions, and initial biofilm formation correlates with missed detection of contaminated platelet concentrates by the BacT/ALERT system.

Establishment of the first international repository for transfusion-relevant bacteria reference strains: ISBT working party transfusion-transmitted infectious diseases (WP-TTID), subgroup on bacteria.

BACKGROUND: Bacterial contamination of platelet concentrates (PCs) still remains a significant problem in transfusion with potential important clinical consequences, including death. The International Society of Blood Transfusion Working Party on Transfusion-Transmitted Infectious Diseases, Subgroup on Bacteria, organised an international study on Transfusion-Relevant Bacteria References to be used as a tool for development, validation and comparison of both bacterial screening and pathogen reduction methods. MATERIAL AND METHODS: Four Bacteria References (Staphylococcus epidermidis PEI-B-06, Streptococcus pyogenes PEI-B-20, Klebsiella pneumoniae PEI-B-08 and Escherichia coli PEI-B-19) were selected regarding their ability to proliferate to high counts in PCs and distributed anonymised to 14 laboratories in 10 countries for identification, enumeration and bacterial proliferation in PCs after low spiking (0·3 and 0·03 CFU/ml), to simulate contamination occurring during blood donation. RESULTS: Bacteria References were correctly identified in 98% of all 52 identifications. S. pyogenes and E. coli grew in PCs in 11 out of 12 laboratories, and K. pneumoniae and S. epidermidis replicated in all participating laboratories. The results of bacterial counts were very consistent between laboratories: the 95% confidence intervals were for S. epidermidis: 1·19-1·32 × 10(7) CFU/ml, S. pyogenes: 0·58-0·69 × 10(7) CFU/ml, K. pneumoniae: 18·71-20·26 × 10(7) CFU/ml and E. coli: 1·78-2·10 × 10(7) CFU/ml. CONCLUSION: The study was undertaken as a proof of principle with the aim to demonstrate (i) the quality, stability and suitability of the bacterial strains for low-titre spiking of blood components, (ii) the property of donor-independent proliferation in PCs, and (iii) their suitability for worldwide shipping of deep frozen, blinded pathogenic bacteria. These aims were successfully fulfilled. The WHO Expert Committee Biological Standardisation has approved the adoption of these four bacteria strains as the first Repository for Transfusion-Relevant Bacteria Reference Strains and, additionally, endorsed as a project the addition of six further bacteria strain preparations suitable for control of platelet contamination as the next step of enlargement of the repository.

Antimicrobial activity of B-Lock against bacterial and Candida spp. causing catheter-related bloodstream infections.

The triple combination trimethoprim, EDTA, and ethanol (B-Lock), is an antimicrobial lock solution for use in indwelling intravascular catheters to prevent and treat catheter-associated infections. B-Lock demonstrated MICs of ≤0.05% (percentage of solution) against Candida spp. (n = 125) and 0.003% to 25% against bacterial strains (n = 175). B-Lock was also fungicidal against the majority of the Candida strains at 6% to 25%. B-Lock demonstrates potential value for the prevention and treatment of catheter-associated infections.

Bacterial clearance of biologic grafts used in hernia repair: an experimental study.

BACKGROUND: Biologic grafts used in ventral hernia repair are derived from various sources and undergo different post-tissue-harvesting processing, handling, and sterilization techniques. It is unclear how these various characteristics impact graft response in the setting of contamination. We evaluated four materials in an infected hernia repair animal model using fluorescence imaging and quantitative culture studies. METHODS: One hundred seven rats underwent creation of a chronic hernia. They were then repaired with one synthetic polyester control material (n = 12) and four different biologic grafts (n = 24 per material). Biologic grafts evaluated included Surgisis (porcine small intestinal submucosa), Permacol (crosslinked porcine dermis), Xenmatrix (noncrosslinked porcine dermis), and Strattice (noncrosslinked porcine dermis). Half of the repairs in each group were inoculated with Staphylococcus aureus at 10(4) CFU/ml and survived for 30 days without systemic antibiotics. Animals then underwent fluorescence imaging and quantitative bacterial studies. RESULTS: All clean repairs remained sterile. Rates of bacterial clearance were as follows: polyester synthetic 0%, Surgisis 58%, Permacol 67%, Xenmatrix 75%, and Strattice 92% (P=0.003). Quantitative bacterial counts had a similar trend in bacterial clearance: polyester synthetic 1×10(6) CFU/g, Surgisis 4.3×10(5) CFU/g, Permacol 1.7×10(3) CFU/g, Xenmatrix 46 CFU/g, and Strattice 31 CFU/g (P=0.001). Fluorescence imaging was unable to detect low bacterial fluorescence counts observed on bacterial studies. CONCLUSION: Biologic grafts, in comparison to synthetic material, are able to clear a Staphylococcus aureus contamination; however, they are able to do so at different rates. Bacterial clearance correlated to the level of residual bacterial burden observed in our study. Post-tissue-harvesting processing, handling, and sterilization techniques may contribute to this observed difference in ability to clear bacteria.

Characterization of penicillin intermediate serotypes of Streptococcus pneumoniae carried by human immunodeficiency virus-infected adults and healthy children in Uganda.

There are little data on the genetic relatedness between antibiotic-resistant pneumococcal isolates colonizing the Ugandan population. Penicillin-intermediate pneumococci of serogroups or serotypes rarely or not previously reported as being penicillin nonsusceptible were selected out of 166 isolates representing 26 capsular serogroups or serotypes isolated from Ugandan children in 1995 and human immunodeficiency virus (HIV) infected Ugandan adults in 2004-2005. Pairs of penicillin-intermediate pneumococci of the same serogroup or serotype present in both patient populations were characterized further by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Seven such pairs of isolates were found and included serogroups 7, 11, 15B/C, and 16 as well as serotypes 13, 21, and 35B. PFGE of these seven pairs showed no clonality between serogroups or serotypes, and clonality only within serogroup 11 and serotype 13. MLST of the 14 individual isolates revealed 13 different sequence types (STs), 11 of which had not previously been recorded. Comparisons with all known STs revealed that most of these strains were related only to strains of the same serotype in other countries, with these related strains frequently also being penicillin intermediate. These findings suggest that penicillin nonsusceptibility in Uganda is likely due to the introduction of antibiotic-resistant pneumococcal clones into Uganda rather than development of resistance within the country.

Activity of the new quinolone WCK 771 against pneumococci.

The activity of WCK 771, a new experimental quinolone being developed to overcome quinolone resistance in staphylococci, against quinolone-susceptible and -resistant pneumococci was determined. Comparative activities of ciprofloxacin, levofloxacin, gatifloxacin, moxifloxacin, clinafloxacin, vancomycin, linezolid, amoxycillin, cefuroxime, azithromycin and clarithromycin were determined with MIC and time-kill experiments. Animal experiments were also performed to test the in-vivo anti-pneumococcal activity of WCK 771 compared to levofloxacin. WCK 771 MIC50/90 values for 300 quinolone-susceptible Streptococcus pneumoniae isolates (108 penicillin-susceptible, 92 penicillin-intermediate and 100 penicillin-resistant) were 0.5/0.5 mg/L; the MICs of beta-lactams and macrolides rose with those of penicillin G, and all isolates were susceptible to vancomycin and linezolid. WCK 771 MIC50/90 values for 25 quinolone-resistant pneumococcal isolates were 4/8 mg/L, compared to 0.5/1 mg/L for clinafloxacin, 2/4 mg/L for gatifloxacin and moxifloxacin, 8/16 mg/L for levofloxacin, and 16/>32 mg/L for ciprofloxacin. Time-kill studies showed that WCK 771 was bactericidal against pneumococci after 24 h at 4 x MIC, as were the other quinolones tested. Animal model studies showed that WCK 771 had efficacy comparable to that of levofloxacin, by both the oral and subcutaneous routes, for systemic infection caused by three quinolone-susceptible isolates of pneumococci. Overall, WCK 771 was potent both in vivo and in vitro against quinolone-susceptible, but not quinolone-resistant, S. pneumoniae, regardless of penicillin susceptibility.

Streptococcus mitis. A cause of serious infection in adults.

Twenty strains of Streptococcus mitis were isolated from blood or body fluids at the Cleveland Veterans Administration Medical Center from Jan 1, 1981, to April 30, 1984. Fifteen (75%) isolates were considered contaminants. Five (25%) were clinically important and associated with a serious infection of the oropharynx or gastrointestinal tract (three of five), endovascular system (one of five), or a prosthetic hip. Four of five patients required surgical intervention for treatment. Two of five died; one death was directly attributable to S mitis infection. Eighteen strains were available for detailed bacteriologic study. Three strains had a minimum inhibitory concentration of greater than 0.1 micrograms/mL of penicillin and six other strains were tolerant to penicillin. This review suggests that S mitis can be an important pathogen in adults and may cause infections other than endocarditis.

A phase II/III trial of antimicrobial therapy with or without amikacin in the treatment of disseminated Mycobacterium avium infection in HIV-infected individuals. AIDS Clinical Trials Group Protocol 135 Study Team.

OBJECTIVE: To determine the clinical and microbiologic benefit of adding amikacin to a four-drug oral regimen for treatment of disseminated Mycobacterium avium infection in HIV-infected patients. DESIGN: A randomized, open-labeled, comparative trial. SETTING: Outpatient clinics. PATIENTS: Seventy-four patients with HIV and symptomatic bacteremic M. avium infection. INTERVENTIONS: Rifampin 10 mg/kg daily, ciprofloxacin 500 mg twice daily, clofazimine 100 mg every day, and ethambutol 15 mg/kg orally daily for 24 weeks, with or without amikacin 10 mg/kg intravenously or intramuscularly 5 days weekly for the first 4 weeks. MAIN OUTCOME MEASURE: Clinical and microbiologic response at 4 weeks; quantitative level of bacteremia with M. avium. RESULTS: No difference in clinical response was noted with the addition of amikacin to the four-drug oral regimen, and only 25% in either group had a complete or partial response at 4 weeks. A comparable quantitative decrease in bacteremia was noted in both treatment groups, with 16% of patients being culture-negative at 4 weeks and 38% at 12 weeks. Toxicities were mainly gastrointestinal. Amikacin was well tolerated. Median survival was 30 weeks in both groups. CONCLUSIONS: The addition of amikacin to a four-drug oral regimen of rifampin, ciprofloxacin, clofazimine, and ethambutol did not provide clinical or microbiologic benefit.

Evaluation of the bactericidal activity of temafloxacin.

Although the fluoroquinolones share many properties, these agents differ in their ability to kill the same bacterial strain. The bactericidal activity of temafloxacin against a number of pathogens has been compared with that of other fluoroquinolones by determination of minimal bactericidal concentration, time-kill kinetics, and postantibiotic effect. Studies have demonstrated that temafloxacin has equivalent or superior ability to kill when compared with other fluoroquinolones. Temafloxacin, ciprofloxacin, and PD 117558 were more active than other fluoroquinolones against Mycobacterium avium complex, with 90% minimal bactericidal concentrations (MBC90S; 8-16 micrograms/mL) four- to eightfold greater than 90% minimal inhibitory concentrations (MIC90S; 2 micrograms/mL). Against Chlamydia trachomatis the MIC90 and MBC90 of temafloxacin were both 0.25 microgram/mL; ciprofloxacin was less active (MBC90 twice the MIC90), and norfloxacin was least active. Temafloxacin demonstrated more rapid killing kinetics than did ciprofloxacin or ofloxacin at all concentrations tested against Streptococcus pyogenes. Findings were similar against Streptococcus pneumoniae at antibiotic concentrations of 1-2 micrograms/mL. Similar time-kill curves against Escherichia coli were observed for temafloxacin, ciprofloxacin, and difloxacin. Time-kill kinetics of temafloxacin against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) were superior to those of ciprofloxacin and ofloxacin. Postantibiotic effect with temafloxacin against Legionella pneumophila showed a considerable delay in regrowth, and temafloxacin delayed regrowth of MRSA and MSSA to a greater extent than did ciprofloxacin or ofloxacin. By the three methods used in the studies to assess bactericidal activity that are currently published, temafloxacin had equivalent or superior activity to the comparative fluoroquinolones tested. Other organisms remain to be tested and the significance of these findings determined in clinical studies.

Drug-resistant Streptococcus pneumoniae: rational antibiotic choices.

Increasingly, Streptococcus pneumoniae with reduced susceptibility to penicillin is becoming a healthcare concern, not only because of the high prevalence of infections caused by this pathogen but also because of the rate at which resistance has progressed. The incidence of penicillin resistance in strains of S. pneumoniae approaches 40% in some areas of the United States, and the incidence of high-level resistance has increased by 60-fold during the past 10 years. With the exception of meningitis and otitis media, there is no conclusive evidence that the acquisition of resistance by S. pneumoniae to beta-lactam antibiotics incurs greater morbidity and mortality in infections caused by this pathogen. However, if the current trends of resistance patterns continue, one can expect the morbidity and mortality to increase. The mechanism of beta-lactam resistance of S. pneumoniae involves genetic mutations which alter penicillin-binding protein structure, resulting in a decreased affinity for all beta-lactam antibiotics. In the treatment of infections caused by S. pneumoniae, it should not be assumed that nonsusceptibility to beta-lactam antibiotics correlates with clinical ineffectiveness of these agents. On the contrary, the recommended therapy for nonmeningeal pneumococcal infections (e.g., pneumonia, sepsis, acute otitis media) includes a beta-lactam antibiotic: penicillin G, amoxicillin, amoxicillin/clavulanate, cefuroxime, cefotaxime, or ceftriaxone. Recommended therapy for meningitis is cefotaxime or ceftriaxone, with the addition of vancomycin until susceptibility is known. These agents are recommended because of their ability to achieve serum/tissue concentrations greater than the minimum inhibitory concentrations (MICs) of these agents against penicillin-susceptible, penicillin-intermediate, and most penicillin-resistant strains (e.g., penicillin G, cefotaxime, ceftriaxone, amoxicillin, amoxicillin/clavulanate, and cefuroxime), or their ability to provide adequate concentrations in cerebrospinal fluid (e.g., cefotaxime, ceftriaxone).

Activity of quinolones against mycobacteria.

The fluoroquinolones have been shown to be highly active in vitro against many mycobacterial species, including most strains of Mycobacterium tuberculosis and M. fortuitum, and some strains of M. kansasii, M. avium-intracellulare (MAI) complex and M. leprae. Ciprofloxacin, ofloxacin and sparfloxacin are the best studied of this class of drugs to date, and they are among the most active of these against M. tuberculosis and other mycobacteria. The use of ofloxacin in the treatment of patients with multidrug-resistant pulmonary tuberculosis has resulted in the selection of quinolone-resistant mutants in a few patients. Many strains of MAI, however, are resistant to fluoroquinolones, and structure-activity relationship studies have been undertaken to identify the moieties associated with activity and inactivity. The most important features determining activity against MAI were found to be a cyclopropyl ring at the N1 position, fluorine atoms at positions C6 and C8, and a C7 heterocyclic substituent. On the basis of these structural requirements, a series of compounds were tested, and many did indeed show good activity against MAI in vitro. Application of these data to macrophage and animal models is in progress. Clinical evaluation of some of these new fluoroquinolones is also being undertaken in multidrug-resistant tuberculosis and MAI and M. leprae infections. Although the development of resistance and the influence of host factors may limit their use, they have considerable potential if prudently used.

Activity of quinolones against mycobacteria.

The fluoroquinolones have been shown to be active in vitro against many mycobacterial species, including most strains of Mycobacterium tuberculosis complex and M. fortuitum, and some strains of M. kansasii, M. avium-intracellulare (MAI) complex and M. leprae. Ciprofloxacin, ofloxacin and sparfloxacin are the best studied of these agents to date, and are among the most active of this group against M. tuberculosis and other mycobacteria. Treatment of patients with multidrug-resistant pulmonary tuberculosis using ofloxacin has resulted in the selection of quinolone-resistant mutants in a few patients. Many strains of MAI, however, are resistant to fluoroquinolones, and structure-activity relationships and DNA gyrase studies have been undertaken to identify the moieties associated with activity and the lack thereof. The genetic and molecular basis of quinolone resistance in mycobacteria has revealed both the recent progress made in these areas and the limitations of the quinolones against this genus. Considerable progress will need to be made in resolving these issues in order for the quinolones to become clinically useful antimycobacterial agents.

Use of real time pulsed field gel electrophoresis to guide interventions during a nursery outbreak of Serratia marcescens infection.

BACKGROUND: Pulsed field gel electrophoresis (PFGE) is a commercially available technique that can establish clonal relationships among many common hospital-derived organisms with a high degree of accuracy and can yield results in a sufficiently short time to guide interventions during an outbreak investigation. METHODS: The CHEF Genomic Bacterial DNA Plug Kit (Bio-Rad) was applied to an unfolding nursery outbreak of Serratia marcescens infections according to the manufacturer's guidelines. Bacterial genomic DNA was digested with XbaI or SpeI and separated on 1% agarose gels, and the isolates were grouped by restriction endonuclease patterns according to established standards. RESULTS: S. marcescens was isolated from nine patients in an intensive care nursery during an 8-week period. Initial PFGE analysis performed after identification of the first eight patients, when closure of the nursery was imminent, revealed that the epidemic was caused by two groups of four isolates each. In both instances the group was geographically contained, and the nursery remained open. A second PFGE analysis indicated that a ninth S. marcescens isolate, recovered in Week 8, was genetically unrelated to the other two. Surveillance during an additional 6 weeks revealed no new cases, and the epidemic was declared over. No cases of invasive S. marcescens infection were identified during the subsequent 10 months. CONCLUSION: Real-time PFGE determined that an apparent nursery outbreak of S. marcescens infection was, in fact, caused by three genetically distinct strains. This information allowed the nursery to remain open after other appropriate infection control measures had been imposed.

Bacteriologic and clinical efficacy of high dose amoxicillin/clavulanate in children with acute otitis media.

OBJECTIVES: To determine the bacteriologic and clinical efficacy of high dose amoxicillin/clavulanate (90/6.4 mg/kg/day) against common bacterial pathogens causing acute otitis media (AOM), including penicillin-resistant Streptococcus pneumoniae (PRSP). METHODS: In this open label multicenter study, 521 infants and children with AOM [mean age, 18.6 months; age < 24 months, n = 375 (72%)] were treated with amoxicillin/clavulanate 90/6.4 mg/kg/day in two divided doses for 10 days. Bilateral otitis media, previous episodes of AOM, antibiotic treatment within 3 months and day-care attendance were recorded in 60.1, 35.7, 50.2 and 38.2% of the children, respectively. Tympanocentesis was performed before the first dose and repeated on Days 4 to 6 for all children with S. pneumoniae at 22 centers and for all children with any pathogen at 3 centers. Clinical response was assessed at end of therapy. RESULTS: Pathogens were isolated from 355 (68%) of 521 enrolled children; 180 children underwent repeat tympanocentesis and were bacteriologically evaluable. Baseline pathogens were S. pneumoniae (n = 122 enrolled/93 bacteriologically evaluable), Haemophilus influenzae (n = 160/51), both (n = 37/32) and others (n = 36/4). Pathogens were eradicated from 172 (96%) of 180 bacteriologically evaluable children. Overall 122 (98%) of 125 isolates of S. pneumoniae were eradicated, including 31 (91%) of 34 PRSP isolates (penicillin MICs 2 to 4 micrograms/ml). Seventy-eight (94%) of 83 isolates of H. influenzae were eradicated. Symptoms and otoscopic signs of acute inflammation were completely resolved or improved on Days 12 to 15 in 263 (89%) of 295 clinically evaluable children with bacteriologically documented AOM. CONCLUSIONS: On the basis of bacteriologic outcome on Days 4 to 6 and clinical outcome on Days 12 to 15, we found that high dose amoxicillin/clavulanate (90/6.4 mg/kg/day) was highly efficacious in children with AOM, including those most likely to fail treatment, namely children < 24 months of age and those with infectious caused by PRSP.

Bacteriologic and clinical efficacy of amoxicillin/clavulanate vs. azithromycin in acute otitis media.

OBJECTIVES: To compare the bacteriologic and clinical efficacy of amoxicillin/clavulanate and azithromycin in patients with acute otitis media (AOM), particularly the ability to eradicate the predominant AOM pathogens from middle ear fluid as assessed by mandatory second tympanocentesis. METHODS: In this single blind study 238 infants and children with AOM were randomized to receive amoxicillin/clavulanate (45/6.4 mg/kg/day in two divided doses for 10 days) or azithromycin (10 mg/kg on Day 1, then 5 mg/kg daily on Days 2 through 5). Tympanocentesis was performed before the first dose and repeated on Day 4, 5 or 6. Clinical response was assessed at end of therapy between Days 12 and 14 and at follow-up between Days 22 and 28. RESULTS: Amoxicillin/clavulanate was significantly more likely to eradicate all bacterial pathogens [83% (54 of 65) vs. 49% (35 of 71), P = 0.001] and Haemophilus influenzae [87% (26 of 30) vs. 39% (13 of 33), P = 0.0001] from middle ear fluid than was azithromycin. Amoxicillin/clavulanate was also more likely to eradicate Streptococcus pneumoniae, but the difference was not statistically significant [90% (18 of 20) vs. 68% (13 of 19) [corrected], P = 0.095]. On Days 12 to 14, signs and symptoms were more likely to resolve completely or improve in all culture-positive patients [86% (60 of 70) vs. 70% (51 of 73), P = 0.023] and in those with H. influenzae infections [91% (30 of 33) vs. 65% (22 of 34), P = 0.010] who received amoxicillin/clavulanate compared with those who received azithromycin. Otherwise there were no significant differences between groups in clinical outcomes on Days 12 to 14 or at follow-up. CONCLUSIONS: Our findings indicate that amoxicillin/clavulanate has superior bacteriologic and clinical efficacy compared with azithromycin in children with AOM.