Comparative in vitro activity of piperacillinl tazobactam against Gramnegative bacilli

Objective. To describe the in vitro activity of piperacillinl tazobactam against clinical isolates of Gram-negative bacteria, compared with other antibacterial agents.Design. Survey of susceptibility of clinical isolates of Gram-negative bacilli.Setting. Academic hospitals of the University of the Witwatersrand teaching complex. Bacterial strains_ 180 selected clinical isolates of Gramnegative bacilli.Main outcome measures. Minimum inhibitory concentrations (MICs) determined by agar dilution using techniques according to the recommendations of the National Committee for Clinical Laboratory Standards.Results. Ciprofloxacin, biapenem, imipenem, cefepime and cefpirome were all highly active against most of the Enterobacteriaceae. All the ampicillin-resistant strains of Enterobacteriaceae were susceptible to piperacillinl tazobactam, MICSll values being 4/4 mgll for Klebsiella and Proteus/Providencia spp., 8/4 mg/l for Citrobacter and Serratia spp_, and 16/4 mg/l for Escherichia coli. All the agents, with the exception of ampicillin (MIC90 4 mg/l) and chloramphenicol (MIC90 4 mg/l), were highly active against the Haemophilus influenzae isolates tested. All Bacteroides fragilis strains were susceptible to piperacillinllazobaclam (MIC90 8/4 mgll), as well as 10 co-amoxiclav (MIC90 4/2 mg/I), biapenem and imipenem (MIC90 0.5 mg/l). The Pseudomonas spp. lested included strains resistant to piperacillinltazobactam, ceftazidime, biapenem, gentamicin, tobramycin and ciprofloxacin. Cefepime was the most active agent against Pseudomonas isolates, with 90% of the strains being susceptible to this agent, while biapenem was the mast active agent against the Acinetobacter isolates investigated.Conclusions. The in vitro spectrum of activity of piperacillin!tazobactam against the majority of isolates was comparable to those of the other new agents tested

Risk factors for antibiotic resistance in Streptococcus pneumoniae

Streptococcus pneumoniae (the pneumococcus) is the leading vaccine preventable cause of death in children and adults. The management of pneumococcal infections is complicated by the development of resistance to antimicrobials. Risk factors for increased resistance include young age, isolation from the upper respiratory tract, hospitalization, residence in an urban area, attendance of day care, previous exposure to antibiotics, female gender, exposure to specific serotypes and clones, HIV infection and exposure to a class of drug to which resistance can be easily selected from a susceptible population of organisms. Conjugate pneumococcal vaccine affords protection from resistant strains belonging to vaccine serotypes, but resistance is emerging in non – vaccine types

Novel Approaches to the Identification of Streptococcus pneumoniae as the Cause of Community-Acquired Pneumonia

Current diagnostic tests lack sensitivity for the identification of the bacterial etiology of pneumonia. Attempts during the past 2 decades to improve sensitivity of detection of bacterial constituents in blood by use of antibody-antigen complexes and polymerase chain reaction have been disappointing. Recent data using pneumococcal conjugate vaccines as probes suggest that increased levels of both C-reactive protein and procalcitonin may be useful adjuncts to chest radiographs in the selection of patients with presumed bacterial pneumonia for inclusion in clinical trials. Among pneumococcal diagnostics currently under investigation, quantitative real-time polymerase chain reaction of respiratory secretions, as well as urinary antigen detection and pneumococcal surface adhesin A serological analysis for adults, are candidates for use in future clinical trials of antibiotic

Trends in antimicrobial resistance and serotype distribution of blood and cerebrospinal fluid isolates of streptococcus pneumoniae in South Africa, 1991–1998

AbstractObjective: Since 1979, the South African Institute for Medical Research (SAIMR) has served as the national reference center for pneumococcal serotyping and monitoring of antibiotic resistance trends. This study documents trends in antimicrobial resistance in pneumococci isolated from blood or cerebrospinal fluid (CSF) between 1991 and 1998 in South Africa.Methods: Pneumococcal isolates (n = 7406) from either blood or CSF were sent to the SAIMR reference laboratory for serotyping. The isolates were evaluated for resistance to penicillin, chloramphenicol, tetracycline, erythromycin, clindamycin, and rifampicin.Results: Resistance to one or more antibiotics increased significantly from 19% in 1991 to 1994 to 25% in 1995 to 1998 in all ages, and in children from 32% to 38% (P < 10−6). Although penicillin resistance did not increase in children (28.1% vs. 28.9%), penicillin resistance in all ages increased from 9.6% to 18.0%. Significant increases in resistance to chloramphenicol, tetracycline, erythromycin, and rifampicin also were seen in both groups. Multiple resistance increased significantly, from 2.2% to 3.8%. The proportion of isolates with intermediate or high-level penicillin resistance remained constant during the surveillance period. Erythromycin resistance, predominantly expressed as simultaneous resistance to erythromycin and clindamycin, increased from 1.6% to 2.6%. The percentage of erythromycin-resistant isolates that were resistance to erythromycin alone increased from 10.6% to 28.7%, suggesting the emergence of mefE-mediated resistance. In children 2 years of age and younger, although serogroup 6 remained the most common, there were significant increases in serogroups 19, 18, and 13. The percentage of the total invasive pneumococcal disease in this population that is caused by serogroups found in the nonavalent pneumococcal conjugate vaccine (serogroups 1, 4, 5, 613, 9V, 14, 18C, 19F, 23F) increased from 72% to 91%.Conclusions: Antibiotic resistance in the pneumococcus is increasing in South Africa, although the proportion of strains with high-level penicillin resistance has not increased. New conjugate vaccines may not only decrease the burden of all pneumococcal disease but, in addition, lower the incidence of antibiotic-resistant disease in South Africa

The Anticipated Severity of a “1918-Like” Influenza Pandemic in Contemporary Populations: The Contribution of Antibacterial Interventions

Recent studies have shown that most of deaths in the 1918 influenza pandemic were caused by secondary bacterial infections, primarily pneumococcal pneumonia. Given the availability of antibiotics and pneumococcal vaccination, how will contemporary populations fare when they are next confronted with pandemic influenza due to a virus with the transmissibility and virulence of that of 1918? To address this question we use a mathematical model and computer simulations. Our model considers the epidemiology of both the influenza virus and pneumonia-causing bacteria and allows for co-infection by these two agents as well as antibiotic treatment, prophylaxis and pneumococcal vaccination. For our simulations we use influenza transmission and virulence parameters estimated from 1918 pandemic data. We explore the anticipated rates of secondary pneumococcal pneumonia and death in populations with different prevalence of pneumococcal carriage and contributions of antibiotic prophylaxis, treatment, and vaccination to these rates. Our analysis predicts that in countries with lower prevalence of pneumococcal carriage and access to antibiotics and pneumococcal conjugate vaccines, there would substantially fewer deaths due to pneumonia in contemporary populations confronted with a 1918-like virus than that observed in the 1918. Our results also predict that if the pneumococcal carriage prevalence is less than 40%, the positive effects of antibiotic prophylaxis and treatment would be manifest primarily at of level of individuals. These antibiotic interventions would have little effect on the incidence of pneumonia in the population at large. We conclude with the recommendation that pandemic preparedness plans should consider co-infection with and the prevalence of carriage of pneumococci and other bacteria responsible for pneumonia. While antibiotics and vaccines will certainly reduce the rate of individual mortality, the factor contributing most to the relatively lower anticipated lethality of a pandemic with a 1918-like influenza virus in contemporary population is the lower prevalence of pneumococcal carriage