Antimicrobial resistance trends in community-acquired respiratory tract pathogens in the Western Pacific Region and South Africa: report from the SENTRY antimicrobial surveillance program, (1998-1999) including an in vitro evaluation of BMS284756

An overview of antimicrobial resistance surveillance among healthcare-associated pathogens in South Africa

Healthcare-associated infections are a serious public health concern resulting in morbidity and mortality particularly in developing countries. The lack of information from Africa, the increasing rates of antimicrobial resistance and the emergence of new resistance mechanisms intensifies this concern warranting the need for vigorous standardised surveillance platforms that produce reliable and accurate data which can be used for addressing these concerns. The implementation of national treatment guidelines, policies, antimicrobial stewardship programmes and infection prevention and control practices within healthcare institutions require a platform from which it can draw information and direct its approach. In this review, the importance of standardised surveillance systems, the challenges faced in the application of a surveillance system and the condition (existence and nonexistence) of such systems in African countries is discussed. This review also reports on some South African data.

Bronchiectasis in Children: Current Concepts in Immunology and Microbiology

Bronchiectasis is a complex chronic respiratory condition traditionally characterized by chronic infection, airway inflammation, and progressive decline in lung function. Early diagnosis and intensive treatment protocols can stabilize or even improve the clinical prognosis of children with bronchiectasis. However, understanding the host immunologic mechanisms that contribute to recurrent infection and prolonged inflammation has been identified as an important area of research that would contribute substantially to effective prevention strategies for children at risk of bronchiectasis. This review will focus on the current understanding of the role of the host immune response and important pathogens in the pathogenesis of bronchiectasis (not associated with cystic fibrosis) in children.

High prevalence of antimicrobial resistance among common bacterial isolates in a tertiary healthcare facility in Rwanda

Antimicrobial resistance (AMR) is a serious public health threat in both developed and developing countries. Many developing countries, including Rwanda, lack adequate surveillance systems, and therefore, the prevalence of AMR is not well-known. We conducted a prospective observational study to assess the prevalence of AMR among common bacterial isolates from clinical specimens obtained from patients on the medical wards of Kigali University Teaching Hospital (KUTH). We evaluated the antibiotic sensitivity patterns of bacterial pathogens cultured from urine, blood, sputum, and wound swab specimens obtained over a 6-month period (July 1 to December 30, 2013). There were 154 positive cultures from specimens obtained from 141 unique patients over the study period. Urine, blood, wound swab, and sputum cultures comprised 55.2%, 25.3%, 16.2%, and 3.3% of the total specimens evaluated; 31.4% and 58.7% of Escherichia coli and Klebsiella isolates, respectively, were resistant to at least one of the third generation cephalosporins. Eight percent of E. coli isolates were resistant to imipenem; 82% and 6% of Staphylococcus aureus strains were oxacillin- and vancomycin-resistant respectively. Antimicrobial resistance rates are high in Rwanda and pose a serious therapeutic challenge to the management of common infections.

Designing antibiotic cycling strategies by determining and understanding local adaptive landscapes

The evolution of antibiotic resistance among bacteria threatens our continued ability to treat infectious diseases. The need for sustainable strategies to cure bacterial infections has never been greater. So far, all attempts to restore susceptibility after resistance has arisen have been unsuccessful, including restrictions on prescribing [1] and antibiotic cycling [2], [3]. Part of the problem may be that those efforts have implemented different classes of unrelated antibiotics, and relied on removal of resistance by random loss of resistance genes from bacterial populations (drift). Here, we show that alternating structurally similar antibiotics can restore susceptibility to antibiotics after resistance has evolved. We found that the resistance phenotypes conferred by variant alleles of the resistance gene encoding the TEM β-lactamase (bla_TEM) varied greatly among 15 different β-lactam antibiotics. We captured those differences by characterizing complete adaptive landscapes for the resistance alleles bla_TEM-50 and bla_TEM-85, each of which differs from its ancestor bla_TEM-1 by four mutations. We identified pathways through those landscapes where selection for increased resistance moved in a repeating cycle among a limited set of alleles as antibiotics were alternated. Our results showed that susceptibility to antibiotics can be sustainably renewed by cycling structurally similar antibiotics. We anticipate that these results may provide a conceptual framework for managing antibiotic resistance. This approach may also guide sustainable cycling of the drugs used to treat malaria and HIV.

Efficacy and tolerability of moxifloxacin in 2338 patients with acute exacerbation of chronic bronchitis

OBJECTIVE

A post-marketing surveillance (PMS) study was conducted to evaluate the efficacy and tolerability of moxifloxacin 400mg once daily in patients with acute exacerbation of chronic bronchitis (AECB) treated by pulmonologists and pulmonary specialists in community-based practice settings.

PATIENT AND METHODS

2338 patients with AECB (54% male; 46% female) were included in the analysis. PMS studies are prospective, open, uncontrolled and observational in design. All therapeutic decisions were made by the attending physician, based on their clinical practice and experience. This approach was adopted in order to provide valuable information on the safety and efficacy of moxifloxacin therapy in routine clinical practice.

RESULTS

The main symptoms of AECB (cough, expectoration, dyspnoea, chest pain and fever) were either resolved or improved in 80-97% of patients. Most patients (65%) improved within 3 days of starting moxifloxacin therapy and 91.6% by day 5. Mean time to improvement was 3.2±1.6 days. Overall, 96.1% of patients were judged by their physician to be either cured or improved following moxifloxacin therapy. Approximately 57% of patients had previously been treated with an antibiotic for their last episode of AECB. The antibiotics used were mostly macrolides (18.2% of patients), beta-lactams (16.9%), tetracycline/ doxycycline (9.9%) and quinolones (9.5%). The tolerability of moxifloxacin therapy was rated as 'very good' or 'good' in 95.4% of patients. Adverse events were reported in only 1.5% of patients.

CONCLUSION

In conclusion, moxifloxacin 400mg once daily was effective and well tolerated in this group of patients with AECB, combined with a rapid onset of action and a similarly high clinical success rate to that observed in controlled comparative clinical trials.

Once-daily moxifloxacin therapy for community-acquired pneumonia in general practice : evidence from a post-marketing surveillance study of 1467 patients

OBJECTIVE

To assess the efficacy, safety and tolerability of oral moxifloxacin in outpatients with respiratory tract infections treated in general practices in Germany with the focus on community-acquired pneumonia (CAP). METHODS, DESIGN AND PATIENTS: This was an open-label, prospective, uncontrolled, post-marketing surveillance study undertaken between October 2001 and June 2002. Symptoms associated with pneumonia were documented at baseline and at follow-up visits. A general assessment was given and the number of days until improvement/cure were recorded by the attending physician at the end of therapy.

RESULTS

A total of 9036 patients were treated with moxifloxacin, of which 1467 had CAP. The recommended dosage of moxifloxacin (400mg once daily) was used in 97.8% of all CAP patients. Between the initial and final follow-up visits, symptoms of CAP were either improved or cured in 90-99% of patients. More than half of the patients showed improvement after 3 days (54.2%); 89.2% of patients were improved after 5 days. The mean time for patients to recover was 8.0 +/- 2.7 days, with 88.7% of patients recovered by day 10 of treatment. Physicians rated moxifloxacin therapy as 'very good' or 'good' in 96.6% of patients and virtually all favoured prescribing moxifloxacin again. Ten patients (0.7%) reported adverse events during moxifloxacin therapy, mostly gastrointestinal disturbances.

CONCLUSIONS

Moxifloxacin is a very effective and safe treatment for patients with CAP and is highly accepted by physicians and patients because of rapid symptom improvement and good tolerability.

Efficacy and tolerability of moxifloxacin in patients with sinusitis treated in general practice : results of a post-marketing surveillance study

OBJECTIVE

To assess the efficacy, safety and tolerability of moxifloxacin, an 8-methoxy fluoroquinolone, in patients with respiratory tract infections (RTIs) treated in general practice in Germany. Different RTIs were analysed separately, and this paper focuses on patients with acute sinusitis. METHODS, DESIGN AND PATIENTS: This was an open-label, prospective, uncontrolled, post-marketing surveillance study undertaken between October 2001 and June 2002. Symptoms of sinusitis (fever, cough, nasal obstruction, nasal secretion and headache) were assessed at baseline and at follow-up visits, and classified as 'absent', 'mild' or 'severe' by the attending physician.

RESULTS

Altogether 9036 patients were treated with moxifloxacin, of whom 2405 adult men and women had sinusitis. Sinusitis symptoms were improved or cured in at least 92% of patients. Moxifloxacin produced significant improvements after only 3 days (71.6% of patients); 96.2% of patients were improved after 5 days. Most patients (89.5%) had recovered by day 8 and 97.3% by day 10. Physicians rated moxifloxacin therapy as 'good' or 'very good' in 96.6% of patients and almost all favoured prescribing moxifloxacin in the future. Very few adverse events were reported with moxifloxacin (<0.4%), and were mostly gastrointestinal disturbances.

CONCLUSIONS

Moxifloxacin is a very effective and safe treatment for patients with acute sinusitis in general practice and is highly regarded by both physicians and patients because of rapid symptom improvement and good tolerability.

In vitro pharmacodynamics of moxifloxacin versus levofloxacin against 4 strains of Streptococcus pneumoniae: 1 wild type, 2 first-step parC mutants, and 1 pump mutant

Levofloxacin binds topoisomerase IV, whereas moxifloxacin preferentially binds DNA gyrase. Most 1st-step pneumococcal mutants have alterations in the parC gene of topoisomerase IV. Because of differential binding affinity, moxifloxacin may have superior activity against 1st-step mutants compared with levofloxacin. The purpose of this work was to compare rates and extent of bacterial killing of genetically characterized Streptococcus pneumoniae with moxifloxacin and levofloxacin. Four strains of S. pneumoniae were used: a wild type, 2 first-step parC mutants, and a pump mutant. Using an in vitro pharmacodynamic model run in duplicate, we exposed bacteria to unbound moxifloxacin and levofloxacin peaks of 2 and 4.5 mg/L, respectively, which emulated clinical dosing. Additional experiments were done in which the area under the curve (AUC)/MIC ratio of 1 agent was matched to the competing drug's clinical dose AUC/MIC ratio. Time kill curves were analyzed for rate and extent of bacterial kill and regrowth. Pre- and postexposure MIC and polymerase chain reaction (PCR) testing were done. Moxifloxacin and levofloxacin displayed similar rates and extent of bacterial kill for the wild type, efflux pump type, and parC mutant 27-1361B. Moxifloxacin initially achieved a faster rate of kill, regardless of the AUC/MIC ratio, against parC mutant 7362 (P < 0.05) but not an advantage in time to 3 log kill. Postexposure MIC values were elevated for strain 7362 in 2 moxifloxacin experiments and 1 levofloxacin experiment. Post-PCR analysis revealed new gyrA mutations for all 3 isolates. Both moxifloxacin and levofloxacin are effective against multiple strains of S. pneumoniae.

Resistance of Haemophilus influenzae isolates in children under 5 years old with acute respiratory infections in China between 2000 and 2002

This prospective, three-centre study tested for antimicrobial susceptibility in 898 isolates of Haemophilus influenzae between 2000 and 2002 in Chinese children aged under 5 years with acute upper respiratory tract infection. The average incidence of beta-lactamase production was 12.0%. Overall, 88.0% of isolates were susceptible to ampicillin, 100.0% were susceptible to amoxicillin/clavulanic acid, ceftriaxone, cefuroxime and azithromycin, and 99.0% were susceptible to ciprofloxacin. Isolates from Beijing and Shanghai had a lower susceptibility to tetracycline (57.0% and 61.0%, respectively) compared with those from Guangzhou (81.0%), while trimethoprim/sulfamethoxazole susceptibilities in Shanghai (47.0%) and Guangzhou (54.0%) were significantly higher than in Beijing (35.0%). A total of 34.5% of all the isolates were susceptible to all eight of these antimicrobial agents and 12.8% were multi-drug resistant. Ampicillin resistance increased over the duration of the study. These findings show that beta-lactamase production and ampicillin resistance among isolates from Chinese children with upper respiratory tract infection are increasing, and highlight the strong correlation between ampicillin resistance and resistance to cefaclor, chloramphenicol and tetracycline in H. influenzae isolates.

Cefepime versus ceftazidime: considerations for empirical use in critically ill patients

Sepsis and nosocomial infections continue to be a significant problem in intensive care, contributing heavily to mortality and prolonged hospital stay. Early and appropriate antibiotic therapy is critical for optimising outcomes. However, the emergence of highly resistant bacteria, coupled with reduced development of novel antibiotics, means that there is a real threat of development of untreatable nosocomial infections. Cefepime and ceftazidime are broad-spectrum cephalosporins that are widely used to treat Gram-negative nosocomial infections in critically ill patients. Available data suggest that cefepime may have advantages over ceftazidime owing to a broader spectrum of activity and reduced potential for development of bacterial resistance. However, whether either of these agents is superior can only be determined by a head-to-head study evaluating clinical and bacteriological outcomes. Such a study to determine whether apparent differences translate into clinically relevant differences in outcome is indicated.

Methicillin resistance among Staphylococcus aureus isolates from Saudi hospitals

OBJECTIVE

To determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) strains among clinical isolates collected from the 4 tertiary hospitals in Makkah, Saudi Arabia, and to test the antimicrobial susceptibility patterns of S. aureus isolates against 9 antimicrobial agents.

MATERIALS AND METHODS

A total of 512 S. aureus clinical isolates were collected during a period of 1 year starting in April 2003 in Al-Noor, King Abdul-Aziz, Hera and King Faisal Hospitals, Makkah, Saudi Arabia. The sensitivity patterns of these isolates were determined using the Kirby-Bauer disk diffusion method.

RESULTS

The prevalence of MRSA among S. aureus isolates was 38.9% (199/512). Among 199 MRSA isolates, 78.8% showed multidrug resistance to erythromycin, gentamicin and oxytetracycline.

CONCLUSION

The rate of MRSA resistance in this study was much higher than what had been reported in other areas of Saudi Arabia emphasizing the need for local or country-based surveillance to characterize and monitor MRSA and to develop strategies that will improve MRSA treatment and control.

Streptococcus pneumoniae: epidemiology and patterns of resistance

Streptococcus pneumoniae is a leading cause of bacterial pneumonia, meningitis, otitis media, and sinusitis; it results in significant morbidity and mortality in patients with pneumonia and meningitis. The pneumococcus is a common colonizing bacterium in the respiratory tract; it is especially common in the respiratory tracts of children, where it is frequently exposed to antimicrobial agents. This exposure can lead to resistance. Penicillin nonsusceptibility is found in nearly 40% of strains causing disease in adults, although often these cases are treatable with appropriate dosing regimens of many oral and parenteral beta-lactam agents. In the United States resistance to macrolides is widespread--averaging approximately 28%--but geographically variable, ranging from 23% in the northwest to 30% in the northeast. Resistance to tetracyclines and trimethoprim-sulfamethoxazole are reported in approximately 20% and 35% of isolates, respectively, and resistance to multiple classes of agents is increasingly common. Amoxicillin, amoxicillin-clavulanate, respiratory fluoroquinolones, and clindamycin are currently the most effective agents for treatment of respiratory tract infections caused by S pneumoniae, with >90% of isolates in the United States being susceptible. Vancomycin is the only agent against which resistance has not emerged. Patient groups that are at increased risk for developing resistant pneumococcal infections have been identified and include patients with malignancies, human immunodeficiency virus infection, and sickle-cell disease. Judicious use of antimicrobials is the key to preventing the emergence of further resistance, particularly as few new classes of agents are likely to become available for clinical use in the short term.

Antimicrobial activities of garenoxacin (BMS 284756) against Asia-Pacific region clinical isolates from the SENTRY program, 1999 to 2001

Between 1999 and 2001, 16,731 isolates from the Asia-Pacific Region were tested in the SENTRY Program for susceptibility to six fluoroquinolones including garenoxacin. Garenoxacin was four- to eightfold less active against Enterobacteriaceae than ciprofloxacin, although both drugs inhibited similar percentages at 1 microg/ml. Garenoxacin was more active against gram-positive species than all other fluoroquinolones except gemifloxacin. For Staphylococcus aureus, oxacillin resistance was high in many participating countries (Japan, 67%; Taiwan, 60%; Hong Kong, 55%; Singapore, 52%), with corresponding high levels of ciprofloxacin resistance (57 to 99%) in oxacillin-resistant S. aureus (ORSA). Of the ciprofloxacin-resistant ORSA isolates, the garenoxacin MIC was >4 microg/ml for only 9% of them. For Streptococcus pneumoniae, penicillin nonsusceptibility and macrolide resistance were high in many countries. No relationship was seen between penicillin and garenoxacin susceptibility, with all isolates being susceptible at <2 microg/ml. There was, however, a partial correlation between ciprofloxacin and garenoxacin MICs. For ciprofloxacin-resistant isolates for which garenoxacin MICs were 0.25 to 1 microg/liter, mutations in both the ParC and GyrA regions of the quinolone resistance-determining region could be demonstrated. No mutations conferring high-level resistance were detected. Garenoxacin shows useful activity against a wide range of organisms from the Asia-Pacific region. In particular, it has good activity against S. aureus and S. pneumoniae, although there is evidence that low-level resistance is present in those organisms with ciprofloxacin resistance.

Antimicrobial susceptibility of Haemophilus parasuis and Histophilus somni from pigs and cattle in Denmark

A total of 52 Haemophilus parasuis and 80 Histophilus somni isolates were tested for antimicrobial susceptibility by MIC-determinations. None of the isolates were resistant to ampicillin, ceftiofur, ciprofloxacin, erythromycin, florphenicol, penicillin, spectinomycin, tetracycline, tiamulin, or tilmicosin. Two H. parasuis isolates were resistant to trimethoprim + sulfamethoxazole. Six H. parasuis isolates had reduced susceptibility (0.06-0.5 microg/ml) to ciprofloxacin and 10 reduced susceptibility to TMP + sulfamethoxazole (1-2 microg/ml). This study showed that Danish isolates of H. parasuis and H. somni in general are fully susceptible to antimicrobial agents currently used for treatment of infections with these pathogens.

Molecular epidemiology of penicillin-susceptible non-beta-lactam-resistant Streptococcus pneumoniae isolates from Greek children

A total of 128 Streptococcus pneumoniae isolates that were susceptible to penicillin but resistant to non-beta-lactam agents were isolated from young carriers in Greece and analyzed by antibiotic susceptibility testing, serotyping, restriction fragment end labeling (RFEL), and antibiotic resistance genotyping. The serotypes 6A/B (49%), 14 (14%), 19A/F (11%), 11A (9%), 23A/F (4%), 15B/C (2%), and 21 (2%) were most prevalent in this collection. Of the isolates, 65% were erythromycin resistant, while the remaining isolates were tetracycline and/or trimethoprim-sulfamethoxazole resistant. Fifty-nine distinct RFEL types were identified. Twenty different RFEL clusters, harboring 2 to 19 strains each, accounted for 76% of all strains. Confirmatory multilocus sequence typing analysis of the genetic clusters showed the presence of three international clones (Tennessee(23F)-4, England(14)-9, and Greece(6B)-22) representing 30% of the isolates. The erm(B) gene was present in 70% of the erythromycin-resistant isolates, whereas 18 and 8% contained the mef(A) and mef(E) genes, respectively. The pneumococci representing erm(B), erm(A), and mef genes belonged to distinct genetic clusters. In total, 45% of all isolates were tetracycline resistant. Ninety-six percent of these isolates contained the tet(M) gene. In conclusion, penicillin-susceptible pneumococci resistant to non-beta-lactams are a genetically heterogeneous group displaying a variety of genotypes, resistance markers, and serotypes. This suggests that multiple genetic events lead to non-beta-lactam-resistant pneumococci in Greece. Importantly, most of these genotypes are capable of disseminating within the community.