TARGETed surveillance: susceptibility of Streptococcus pneumoniae isolated from community-acquired respiratory tract infections in 2003 to fluoroquinolones and other agents

Appropriate use of fluoroquinolones in children

With the increasing resistance to antibiotics among common bacterial pathogens, challenges associated with the use of fluoroquinolones (FQs) in paediatrics have emerged. The majority of FQs have favourable pharmacokinetic properties, although these properties can differ in children compared with adults. Moreover, all FQs have broad antimicrobial activity both against Gram-positive and Gram-negative bacteria. However, only some FQs for which adequate studies are available have been approved for use in children in a limited number of clinical situations owing to the supposed risk of development of severe musculoskeletal disorders, as demonstrated in juvenile animals. Recent short- and long-term evaluations appear to indicate that, at least for levofloxacin, this risk, if present at all, is marginal. This marginal risk could lead to more frequent use of FQs in children, even to treat diseases for which several other drugs with documented efficacy, safety and tolerability are considered the first-line antibiotics. However, for most of the FQs, adequate long-term studies of safety are not available. This indicates that the use of FQs should be limited to selected respiratory infections (including tuberculosis), exacerbation of lung disease in cystic fibrosis, central nervous system infections, enteric infections, febrile neutropenia, as well as serious infections attributable to FQ-susceptible pathogen(s) in children with life-threatening allergies to alternative agents. When considering diseases that could benefit from the use of FQs, particular attention must be paid to the choice of drug and its dosage, considering that not all of the FQs have been evaluated in different diseases.

History of antibiotics: from fluoroquinolones to daptomycin (Part 2)

In the Modern Era, physicians attested to the reciprocal influence among a technologically advanced society, rapid scientific progresses in medicine, and the need for new antimicrobials. The results of these changes were not only seen in the prolongation of life expectancy but also by the emergence of new pathogens. We first observed the advent of Gram-negative bacteria as a major source of nosocomial infections. The treatment of these microorganisms was complicated by the appearance and spread of drug resistance. We first focused on the development of two major classes of antimicrobials still currently used for the treatment of Gram-negative bacteria, such as fluoroquinolones and carbapenemes. Subsequently, we directed our attention to the growth of the incidence of infections due to Methicillin-Resistant Staphylococcus aureus (MRSA). Although the first MRSA was already isolated in 1961, the treatment of this new pathogen has been based on the efficacy of vancomycin for more than four decades. Only in the last 15 yr, we assisted in the development of new antimicrobial agents such as linezolid and daptomycin.

The use of systemic and topical fluoroquinolones

Appropriate prescribing practices for fluoroquinolones are essential as evolving resistance patterns are considered, additional treatment indications are identified, and the toxicity profile of fluoroquinolones in children becomes better defined. Earlier recommendations for systemic therapy remain; expanded uses of fluoroquinolones for the treatment of certain infections are outlined in this report. Although fluoroquinolones are reasonably safe in children, clinicians should be aware of the specific adverse reactions. Use of fluoroquinolones in children should continue to be limited to treatment of infections for which no safe and effective alternative exists.

Antimicrobial susceptibility of bacterial isolates from community acquired infections in Sub-Saharan Africa and Asian low and middle income countries

OBJECTIVE

Antimicrobial resistance has arisen across the globe in both nosocomial and community settings as a consequence of widespread antibiotic consumption. Poor availability of laboratory diagnosis means that resistance frequently goes unrecognised and may only be detected as clinical treatment failure. In this review, we provide an overview of the reported susceptibility of common community acquired bacterial pathogens in Sub-Saharan Africa and Asia to the antibiotics that are most widely used in these areas.

METHODS

We reviewed the literature for reports of the susceptibility of prevalent pathogens in the community in SSA and Asia to a range of commonly prescribed antibiotics. Inclusion criteria required that isolates were collected since 2004 and that they were obtained from either normally sterile sites or urine. The data were aggregated by region and by age group.

RESULTS

Eighty-three studies were identified since 2004 which reported the antimicrobial susceptibilities of common bacterial pathogens. Different methods were used to assess in-vitro susceptibility in the different studies. The quality of testing (evidenced by resistance profiles) also varied considerably. For Streptococcus pneumoniae and Neisseria meningitidis most drugs maintained relatively high efficacy, apart from co-trimoxazole to which there were high levels of resistance in most of the pathogens surveyed.

CONCLUSIONS

Compared with the enormous infectious disease burden and widespread use of antibiotics there are relatively few reliable data on antimicrobial susceptibility from tropical Asia and Africa upon which to draw firm conclusions, although it is evident that many commonly used antibiotics face considerable resistance in prevalent bacterial pathogens. This is likely to exacerbate morbidity and mortality. Investment in improved antimicrobial susceptibility testing and surveillance systems is likely to be a highly cost-effective strategy and should be complemented by centralized and readily accessible information resources.

Susceptibility of bacterial isolates from community-acquired infections in sub-Saharan Africa and Asia to macrolide antibiotics

OBJECTIVE

To review the literature on the susceptibility of common community pathogens in sub-Saharan Africa and Asia to the macrolide antibiotics.

METHODS

Inclusion criteria required that isolates were collected since 2004 to ensure results were of contemporary relevance. The data were aggregated by region, age group and sterility of site of culture sample.

RESULTS

A total of 51 studies were identified, which reported the macrolide antimicrobial susceptibilities of common bacterial pathogens isolated since 2004. In general, there was less macrolide resistance in African than in Asian isolates. Most African studies reported high levels of macrolide susceptibility in Streptococcus pneumoniae, whereas most Chinese studies reported high levels of resistance. There was very little information available for Gram-negative organisms.

CONCLUSIONS

Susceptibility of the pneumococcus to macrolides in SSA remains high in many areas, and good activity of azithromycin has been shown against Salmonellae spp. in Asia. In urban areas where high antibiotic consumption is prevalent, there was evidence of increased resistance to macrolides. However, there is no information on susceptibility from large areas in both continents.

Clonal spread of levofloxacin-resistant streptococcus pneumoniae invasive isolates in Madrid, Spain, 2007 to 2009

Among 1,349 Streptococcus pneumoniae invasive isolates, 45 (3.3%) were levofloxacin resistant. Serotype distribution was as follows: 8 (n=32 isolates), 19A (n=4 isolates), 7F (n=3 isolates), 9V (n=2 isolates), 10A (n=1 isolate), 19F (n=1 isolate), 6B (n=1 isolate), and nontypeable (n=1 isolate). Levofloxacin-resistant isolates had dual mutations in the gyrA and parC genes. Serotype 8 strains corresponded to a capsular switching of the Sweden(15A)-25 clone. Levofloxacin resistance was also detected among multiresistant (ST276(19A), Spain9V-ST156, ST88(19F), and ST1542(6B)) and among usually antibiotic-susceptible (Netherlands7F-ST191, ST1201(19A), and ST2639(10A)) clones.

Emergence of fluoroquinolone-resistant Streptococcus pneumoniae in Lebanon: a report of three cases

The global emergence of Streptococcus pneumoniae resistance to fluoroquinolones is alarming and has grown to be a cause for significant concern worldwide. We report the first three cases of levofloxacin resistant S. pneumoniae isolates in a tertiary medical center in Beirut, Lebanon. Judicious use of antimicrobial agents is imperative to limit the spread of such resistant strains.

Probing the differential interactions of quinazolinedione PD 0305970 and quinolones with gyrase and topoisomerase IV

Quinazoline-2,4-diones, such as PD 0305970, are new DNA gyrase and topoisomerase IV (topo IV) inhibitors with potent activity against gram-positive pathogens, including quinolone-resistant isolates. The mechanistic basis of dione activity vis-à-vis quinolones is not understood. We present evidence for Streptococcus pneumoniae gyrase and topo IV that PD 0305970 and quinolones interact differently with the enzyme breakage-reunion and Toprim domains, DNA, and Mg2+-four components that are juxtaposed in the topoisomerase cleavage complex to effect DNA scission. First, PD 0305970 targets primarily gyrase in Streptococcus pneumoniae. However, unlike quinolones, which select predominantly for gyrA (or topo IV parC) mutations in the breakage-reunion domain, unusually the dione selected for novel mutants with alterations that map to a region of the Toprim domain of GyrB (R456H and E474A or E474D) or ParE (D435H and E475A). This "dione resistance-determining region" overlaps the GyrB quinolone resistance-determining region and the region that binds essential Mg2+ ions, each function involving conserved EGDSA and PLRGK motifs. Second, dione-resistant gyrase and topo IV were inhibited by ciprofloxacin, whereas quinolone-resistant enzymes (GyrA S81F and ParC S79F) remained susceptible to PD 0305970. Third, dione-promoted DNA cleavage by gyrase occurred at a distinct repertoire of sites, implying that structural differences with quinolones are sensed at the DNA level. Fourth, unlike the situation with quinolones, the Mg2+ chelator EDTA did not reverse dione-induced gyrase cleavage nor did the dione promote Mg2+-dependent DNA unwinding. It appears that PD 0305970 interacts uniquely to stabilize the cleavage complex of gyrase/topo IV perhaps via an altered orientation directed by the bidentate 3-amino-2,4-dione moiety.

Changes in fluoroquinolone-resistant Streptococcus pneumoniae after 7-valent conjugate vaccination, Spain

Among 4,215 Streptococcus pneumoniae isolates obtained in Spain during 2006, 98 (2.3%) were ciprofloxacin resistant (3.6% from adults and 0.14% from children). In comparison with findings from a 2002 study, global resistance remained stable. Low-level resistance (30 isolates with MIC 4-8 microg/mL) was caused by a reserpine-sensitive efflux phenotype (n = 4) or single topoisomerase IV (parC [n = 24] or parE [n = 1]) changes. One isolate did not show reserpine-sensitive efflux or mutations. High-level resistance (68 isolates with MIC >or=16 microg/mL) was caused by changes in gyrase (gyrA) and parC or parE. New changes in parC (S80P) and gyrA (S81V, E85G) were shown to be involved in resistance by genetic transformation. Although 49 genotypes were observed, clones Spain9V-ST156 and Sweden15A-ST63 accounted for 34.7% of drug-resistant isolates. In comparison with findings from the 2002 study, clones Spain14-ST17, Spain23F-ST81, and ST8819F decreased and 4 new genotypes (ST9710A, ST57016, ST43322, and ST71733) appeared in 2006.

In vitro selection of resistance in Streptococcus pneumoniae at in vivo fluoroquinolone concentrations

OBJECTIVES

To compare the ability to select for resistance in Streptococcus pneumoniae of levofloxacin, moxifloxacin, ciprofloxacin and prulifloxacin.

METHODS

Twenty strains of S. pneumoniae susceptible to fluoroquinolones were used. The frequencies of spontaneous single-step mutations at plasma and epithelial lining fluid (ELF) peak and trough antibiotic concentrations were calculated. Multi-step selection of resistance was evaluated by performing 10 serial subcultures on agar plates containing a linear gradient from peak to trough antimicrobial concentrations, followed by 10 subcultures on antibiotic-free agar. Resistant strains selected after multi-step selection were characterized for DNA mutations by sequencing gyrA, gyrB, parC and parE genes.

RESULTS

Levofloxacin and moxifloxacin showed the lowest frequencies of mutations (median <10(-11)) at plasma peak and at ELF concentrations, while medians ranging from 10(-8) to 10(-6) were observed for ciprofloxacin and prulifloxacin. In a multi-step selection assay, ciprofloxacin and prulifloxacin selected for the highest number of resistant strains (19 and 31, respectively). No selection of resistance was observed for levofloxacin at ELF concentrations and for moxifloxacin at plasma and ELF concentrations. Mutations in parC, parE and gyrA genes were found in ciprofloxacin- and prulifloxacin-resistant strains, while only parC mutations were found for levofloxacin.

CONCLUSIONS

Levofloxacin and moxifloxacin are characterized by a lower propensity to select in vitro for resistance in S. pneumoniae than ciprofloxacin and prulifloxacin, when tested at plasma and lung concentrations.

Antimicrobial susceptibility and molecular epidemiology of Streptococcus pneumoniae isolated from Shanghai, China

In this study, the antimicrobial resistance profiles of pneumococci isolated from respiratory specimens of patients from Shanghai, China, in 2004 and 2005 are described. Non-susceptible rates to penicillin and erythromycin among paediatric isolates (n=122) were 63.1% and 94.3%, respectively, whilst those of adult isolates (n=39) were 20.5% and 69.2%, respectively (P<0.0001 and P<0.0002). Nineteen serotypes were identified among 103 tested strains, 73.8% of which belonged to 19F, 14, 23F, 6B and 19A. The erm(B) gene was detected in 51 erythromycin-resistant strains (52.6%), the mef(E) gene in 5 strains (5.2%) and both erm(B) and mef(E) in 41 strains (42.3%). Among 45 sequence types (STs) determined by multilocus sequence typing (MLST) in these 103 isolates, 25 STs were new assignments and 9 STs contained 10 new alleles. On the other hand, 46 (68.7%) of 67 penicillin-non-susceptible S. pneumoniae and 51 (52.6%) of 97 macrolide-resistant S. pneumoniae were characterised as belonging to four international resistant clonal complexes, Taiwan(19F)-14, Spain(23F)-1, Spain(6B)-2 and Taiwan(23F)-15. Our findings indicate that the spread of international resistant clones played a predominant role in the emergence and increase of resistance in Shanghai. Conjugate vaccination may be a promising method to prevent the increase in pneumococcal resistance.