The battle against emerging antibiotic resistance: should fluoroquinolones be used to treat children?

Prevalence and nature of off-label antibiotic prescribing for children in a tertiary setting: A descriptive study from Jordan

Objective:

The aim of the present study was to evaluate the use of off-label antibiotics in neonatal intensive care units (NICUs) and paediatric wards in Jordan.

Methods:

Data of patients admitted to the neonatal intensive care units and paediatric wards in King Abdulla University Hospital were collected over an 8-week survey between May and July 2012. Data collected in this study included patients’ age, weight, medical history, diagnosis and the details of antibiotics prescribed to each patient.

Results:

The study involved a total of 250 children (80 admitted to the NICU and 170 admitted to the wards). A total of 598 antibiotic prescriptions were issued for these patients (244 in NICUs and 354 in paediatricwards). The results of the present study show that off-label antibiotic prescribing to paediatric patients is very common. Off-label antibiotic prescribing to paediatric patients is related mostly to doses and indications, and rarely to age. The majority of admitted patients received at least one off-label antibiotic during their hospital stay.

Conclusion:

This study reveals the high prevalence of off-label use of antibiotic among paediatric children in Jordan. There is a serious need for robust and continuous educational programs to improve the awareness of paediatricians of guidelines surrounding the use of antibiotics in paediatric patients. Furthermore, true collaboration between paediatricians and clinical pharmacists towards safe and effective antibiotic prescribing in paediatric patients is crucial.

Safety Concerns Surrounding Quinolone Use in Children

Fluoroquinolones are highly effective antibiotics with many desirable pharmacokinetic and pharmacodynamic properties including high bioavailability, large volume of distribution, and a broad spectrum of antimicrobial activity. Despite their attractive profile as anti-infective agents, their use in children is limited, primarily due to safety concerns. In this review we highlight the pharmacological properties of fluoroquinolones and describe their current use in pediatrics. In addition, we provide a comprehensive assessment of the safety data associated with fluoroquinolone use in children. Although permanent or destructive arthropathy remains a significant concern, currently available data demonstrate that arthralgia and arthropathy are relatively uncommon in children and resolve following cessation of fluoroquinolone exposure without resulting in long-term sequelae. The concern for safety and risk of adverse events associated with pediatric fluoroquinolone use is likely driving the limited prescribing of this drug class in pediatrics. However, in adults, fluoroquinolones are the most commonly prescribed broad-spectrum antibiotics, resulting in the development of drug-resistant bacteria that can be challenging to treat effectively. The consequence of misuse and overuse of fluoroquinolones leading to drug resistance is a greater, but frequently overlooked, safety concern that applies to both children and adults and one that should be considered at the point of prescribing.

Simultaneous Semimechanistic Population Analyses of Levofloxacin in Plasma, Lung, and Prostate To Describe the Influence of Efflux Transporters on Drug Distribution following Intravenous and Intratracheal Administration

Levofloxacin (LEV) is a broad-spectrum fluoroquinolone used to treat pneumonia, urinary tract infections, chronic bacterial bronchitis, and prostatitis. Efflux transporters, primarily P-glycoprotein (P-gp), are involved in LEV's tissue penetration. In the present work, LEV free lung and prostate interstitial space fluid (ISF) concentrations were evaluated by microdialysis in Wistar rats after intravenous (i.v.) and intratracheal (i.t.) administration (7 mg/kg of body weight) with and without coadministration of the P-gp inhibitor tariquidar (TAR; 15 mg/kg administered i.v.). Plasma and tissue concentration/time profiles were evaluated by noncompartmental analysis (NCA) and population pharmacokinetics (popPK) analysis. The NCA showed significant differences in bioavailability (F) for the control group (0.4) and the TAR group (0.86) after i.t. administration. A four-compartment model simultaneously characterized total plasma and free lung (compartment 2) and prostate (compartment 3) ISF concentrations. Statistically significant differences in lung and prostate average ISF concentrations and levels of kidney active secretion in the TAR group from those measured for the control group (LEV alone) were observed. The estimated population means were as follows: volume of the central compartment (V1), 0.321 liters; total plasma clearance (CL), 0.220 liters/h; TAR plasma clearance (CLTAR), 0.180 liters/h. The intercompartmental distribution rate constants (K values) were as follows: K12, 8.826 h(-1); K21, 7.271 h(-1); K13, 0.047 h(-1); K31, 7.738 h(-1); K14, 0.908 h(-1); K41, 0.409 h(-1); K21 lung TAR (K21LTAR), 8.883 h(-1); K31 prostate TAR (K31PTAR), 4.377 h(-1). The presence of P-gp considerably impacted the active renal secretion of LEV but had only a minor impact on the efflux from the lung following intratracheal dosing. Our results strongly support the idea of a role of efflux transporters other than P-gp contributing to LEV's tissue penetration into the prostrate.

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.

Levofloxacin: update and perspectives on one of the original ‘respiratory quinolones’

The fluoroquinolone class of antimicrobials has enjoyed enormous clinical and marketing success over the past 20 years. These drugs have proven to be extremely useful in a broad range of clinical indications including both common community-acquired as well as nosocomial bacterial infections. Levofloxacin (Levaquin, Tavanic), like ciprofloxacin (Cipro), has established an enviable record of safe and efficacious use, and in many ways has become the agent against which all of the newer fluoroquinolones are judged. New clinical indications in complicated skin and skin structure infections, nosocomial pneumonia and chronic bacterial prostatitis continue to expand the important role of this already versatile drug. In addition, the use of 'short-course, high-dose' therapies are being studied in indications, such as community-acquired pneumonia, in an effort to optimize the efficacy and convenience of the drug while minimizing the future development of resistance. As the use of levofloxacin continues to expand, future challenges will include the threat of increasing antimicrobial resistance and the availability of newer alternative agents, both newer fluoroquinolones as well as agents of other antibiotic classes.

Future Trends in Antimicrobial Chemotherapy: Expert Opinion on the 43rdICAAC

The current document bestows an expert synopsis of key new information presented at the 43rd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) meeting in 2003. Data is presented on the socio-political aspects of and policies on antimicrobial prescribing, novel mechanisms of resistance in Streptococcus pneumoniae, and current epidemiological trends in global resistance. Novel information on new (and existing) antimicrobial agents--new penicillins, cephalosporins, monobactams and oxipenem inhibitors, ketolides, glycopeptides, fluoroquinolones (and hybrids), peptides, daptomycin, aminomethylcyclines, glycylcyclines, and newer formulations of agents such as amoxycillin-clavulanate--provides renewed hope that resistant pathogens can be controlled through use of more potent agents. Improved strategies for the use of existing antimicrobial agents, such as the use of high-dose regimens, short-course therapy, also may delay or reduce the development of resistance and preserve the value of our antibiotic armamentarium.

A one-year prospective study on the antibiotic resistance of E. coli strains isolated in urinary specimens of children hospitalized at the University Pediatric Medical Center in Novi Sad, Serbia

PURPOSE

Urinary tract infections (UTIs), the most common serious bacterial infections in children, are frequently caused by Escherichia coli. The purpose of this study was to investigate E. coli resistance/multidrug resistance to antibiotics most frequently used for UTIs.

METHODS

Children 0-18 years of age, hospitalized at the University Pediatric Hospital in Novi Sad, Serbia, were included in a 1-year observational prospective study. The microbiological analysis was performed using the standard Kirby-Bauer disk diffusion method. The results were analyzed using WHONET 5.4 software.

RESULTS

E. coli was isolated from 61.7 % of positive urine specimens. In general, higher average E. coli antibiotic resistance was found in infants and toddlers compared to children and adolescents (33.4 vs. 25.0 %) (p < 0.0001). Furthermore, it was observed that the average resistance to all the tested antibiotics was higher in boys than in girls (37.0 vs. 25.1 %) (p < 0.0001). E. coli was highly susceptible to piperacillin/tazobactam (>93.1 %), amikacin (86.3 %), quinolones (>75.0 %), and penems (>96.6 %). The prevalence of multiresistant E. coli strains was significantly higher in infants and toddlers (72.3 vs. 36.8 %) (p < 0.0001).

CONCLUSIONS

E. coli, a common cause of UTIs in children admitted to pediatric hospitals, is highly resistant/multidrug-resistant to commonly used antibiotics. Higher average resistance is found in infants and toddlers than in children and adolescents, as well as in boys compared to girls. These findings are important for the regional empiric therapy of UTIs and call for actions to decrease E. coli antibiotic resistance.

A clinical trial comparing parenteral oxytetracyline and enrofloxacin on time to recovery in sheep lame with acute or chronic footrot in Kashmir, India

BACKGROUND

No clinical trials have been conducted in India on the efficacy of parenteral antibacterials to treat footrot in sheep. In addition, there are no studies worldwide on the efficacy of parenteral antibacterials to treat chronic footrot. Sixty two sheep with acute footrot and 30 sheep with chronic footrot from 7 villages in Kashmir, India were recruited into two separate trials. Sheep with acute footrot were allocated to one of three treatments using stratified random sampling: long acting parenteral oxytetracycline, long acting parenteral enrofloxacin and topical application of potassium permanganate solution (a traditional treatment used by sheep farmers in India). In a quasi pre-post intervention design, sheep with chronic footrot that had not responded to treatment with potassium permanaganate were randomly allocated to treatment with one of the two parenteral antibacterials mentioned above. Sheep with acute footrot were treated on day 0 and those with chronic footrot on days 0, 3, 6 and 9. Sheep were monitored for up to 28 days after treatment. Time to recovery from lameness and initial healing of lesions was assessed using Kaplan-Meier survival curves, nonparametric log-rank and Wilcoxon sign-rank tests.

RESULTS

There was significant correlation in recovery from lameness and presence of healing lesions in sheep with acute (r = 0.94) or chronic (r = 0.98) footrot. Sheep with acute footrot which were treated with parenteral antibacterials had a significantly more rapid recovery from lameness and had healing lesions (median = 7 days) compared with those treated with topical potassium permanganate solution (less than 50% recovered in 28 days). The median time to recovery in sheep with chronic footrot treated with either antibacterial was 17 days; this was significantly lower than the median of 75 days lame before treatment with antibacterials. The median time to recovery for both acute and chronic footrot increased as the severity of lesions increased. There was no difference in time to recovery by age, body condition score, duration lame, or presence of pus in the foot within acute and chronically affected sheep.

CONCLUSIONS

We conclude that use of parenteral antibacterials to treat sheep lame with either acute or chronic footrot in India is highly effective. This is likely to improve welfare and give economic benefits to the farmers.

A stable phage lysin (Cpl-1) dimer with increased antipneumococcal activity and decreased plasma clearance

Bacteriophages (phages) produce endolysins (lysins) as part of their lytic cycle in order to degrade the peptidoglycan layer of the infected bacteria for subsequent release of phage progeny. Because these enzymes maintain their lytic and lethal activity against Gram-positive bacteria when added extrinsically to the cells, they have been actively exploited as novel anti-infectives, sometimes termed enzybiotics. As with other relatively small peptides, one issue in their clinical development is their rapid inactivation through proteolytic degradation, immunological blockage and renal clearance. The antipneumococcal lysin Cpl-1 was shown to escape both proteolysis and immunological blockage. However, its short plasma half-life (20.5 min in mice) may represent a shortcoming for clinical usefulness. Here we report the construction of a Cpl-1 dimer with a view to increasing both the antipneumococcal specific activity and plasma half-life of Cpl-1. Dimerisation was achieved by introducing specific cysteine residues at the C-terminal end of the enzyme, thus favouring disulphide bonding. Compared with the native monomer, the constructed dimer demonstrated a two-fold increase in specific antipneumococcal activity and a ca. ten-fold decrease in plasma clearance. As several lysins are suspected to dimerise on contact with their cell wall substrate to be fully active, stable pre-dimerised enzymes may represent a more efficient alternative to the native monomer.

Association between fluoroquinolone usage and a dramatic rise in ciprofloxacin-resistant Streptococcus pneumoniae in Canada, 1997-2006

This study evaluated the prevalence of fluoroquinolone usage and investigated the association between usage and resistance in respiratory isolates of Streptococcus pneumoniae in Canada. Fluoroquinolone susceptibility testing was conducted on S. pneumoniae collected from 25 medical centres across Canada over nine study years. Fluoroquinolone prescriptions and consumption figures were derived from data in the IMS Health, Canada CompuScript Audit. Between 1997 and 2006, 11825 S. pneumoniae isolates were collected. Ciprofloxacin resistance rates increased significantly (P<0.01) during the study from 0% to 4.5% in children (0-15 years), from 0.2% to 5.4% in adults (16-64 years) and from 1.4% to 11.6% in the elderly (> or = 65 years). Outpatient ciprofloxacin and respiratory fluoroquinolone prescriptions increased by 55.6% (38.2 prescriptions/1000 population to 59.4 prescriptions/1000 population; P<0.01) and 416.2% (5.3 prescriptions/1000 to 27.4 prescriptions/1000; P<0.01), respectively. Ciprofloxacin and respiratory fluoroquinolone consumption increased by 10.6% [1.1 defined daily doses (DDDs)/1000/day to 1.2 DDDs/1000/day; P=0.02] and 38.2% (0.5 to 0.7 DDDs/1000/day; P=0.02), respectively, from 2001 to 2006. A strong association between ciprofloxacin use and resistance (R(2)=0.89) was identified. Fluoroquinolone resistance in S. pneumoniae increased significantly in Canada from 1997 to 2006 in conjunction with increased ciprofloxacin and respiratory fluoroquinolone consumption. Ciprofloxacin usage appears to be the biggest driver of resistance; however, total fluoroquinolone usage is also important.

Molecular characterization of emerging non-levofloxacin-susceptible pneumococci isolated from children in South Africa

Fluoroquinolones are not indicated for use for the treatment of pneumonia in children; however, non-levofloxacin-susceptible Streptococcus pneumoniae (NLSSP) has emerged in South Africa among children receiving treatment for multidrug-resistant tuberculosis. This study aimed to genotypically characterize NLSSP isolates. Invasive isolates were collected through active national laboratory-based surveillance for invasive pneumococcal disease (IPD) from 2000 through 2006 (n = 19,404). Carriage studies were conducted at two hospitals for patients with tuberculosis in two provinces. Phenotypic characterization was performed by determination of MICs and serotyping. Fluoroquinolone resistance mutations were identified, and clonality was investigated by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing. Twelve non-levofloxacin-susceptible cases of IPD were identified, and all were in children <15 years of age. Ten isolates were serotype 19F and formed two clusters according to their PFGE profiles, antibiogram types, and fluoroquinolone resistance-conferring mutations. All nine carriage isolates from children in hospital A were NLSSP, serotype 19F, were indistinguishable by PFGE, and were related to invasive isolates in cluster 2. Of 26 child carriers in hospital B, 22 (85%) were colonized with NLSSP. The isolates were indistinguishable by PFGE, although they displayed two serotypes, serotypes 19F and 23F. The isolates were related to invasive isolates in cluster 1; however, higher levofloxacin MICs and different fluoroquinolone resistance mutations were suggestive of horizontal gene transfer. A serotype 23F carriage isolate displayed increased fitness compared with the fitness of an otherwise indistinguishable serotype 19F carriage isolate. These data suggest that a low-level non-levofloxacin-susceptible strain transformed into a highly resistant strain under antibiotic pressure and underwent capsular switching in order to have increased fitness.

Quinolone-induced arthropathy: an update focusing on new mechanistic and clinical data

Quinolones possess favourable antibacterial and pharmacokinetic characteristics and are often used as anti-infective agents in adults. They are contraindicated in children and adolescents because they damage weight-bearing joints in juvenile animals. In addition, they possess a tendotoxic potential. Since ciprofloxacin has been used off-label for decades in children and adolescents, it is known today that no pronounced risks for arthropathies or tendinopathies exist in humans. Recently published clinical studies with gatifloxacin in children support this clinical experience. However, a low risk for joint disorders cannot be excluded and tendinopathies are a generally accepted rare adverse effect of quinolones at least in adults. Isolated case reports of arthralgia in children following quinolone therapy have been published and in studies with levofloxacin the incidence of musculoskeletal disorders was significantly greater in levofloxacin-treated patients than in control patients treated with comparator antibiotics. As a consequence, only life-threatening infections for which other antimicrobials cannot be used are possible indications for quinolones in children, for example the use of ciprofloxacin in cystic fibrosis patients with a bronchopulmonary exacerbation, chronic suppurative otitis media caused by Pseudomonas sp., complicated urinary tract infections and enteritis caused by invasive multidrug-resistant pathogens (e.g. Salmonella, Shigella).

Emergence of levofloxacin-non-susceptible Streptococcus pneumoniae and treatment for multidrug-resistant tuberculosis in children in South Africa: a cohort observational surveillance study

BACKGROUND

Use of fluoroquinolones to treat paediatric cases of multidrug-resistant tuberculosis could affect the emergence of resistance to this class of drugs. Our aim was to estimate the incidence of, and risk factors for, invasive pneumococcal disease caused by fluoroquinolone-resistant Streptococcus pneumoniae in children in South Africa.

METHODS

21,521 cases of invasive pneumococcal disease were identified by active national surveillance between 2000 and 2006, with enhanced surveillance at 15 sentinel hospitals in seven provinces introduced in 2003. We screened 19,404 isolates (90% of cases) for ofloxacin resistance and measured levofloxacin minimum inhibitory concentrations (MICs) for all isolates that were ofloxacin resistant. Non-susceptibility to levofloxacin was defined as an MIC of 4 mg/L or more. Nasopharyngeal pneumococcal carriage was assessed in 65 children in two tuberculosis hospitals where invasive pneumococcal disease caused by levofloxacin-non-susceptible S pneumoniae had been detected.

FINDINGS

12 cases of invasive pneumococcal disease were identified as being non-susceptible to levofloxacin, all in children aged under 15 years. All isolates were rifampicin resistant. Outcome was known for 11 of these patients; five (45%) died. Invasive disease caused by levofloxacin-non-susceptible S pneumoniae was associated with a history of tuberculosis treatment (eight [89%] of nine children with non-susceptible isolates had a history of treatment vs 396 [18%] of 2202 children with susceptible isolates; relative risk [RR] 35.78, 95% CI 4.49-285.30) and nosocomial invasive pneumococcal disease (eight [80%] of ten children with non-susceptible isolates had acquired infection nosocomially vs 109 [4%] of 2709 with susceptible isolates; RR 88.96, 19.10-414.29). 31 (89%) of 35 pneumococcal carriers had bacteria that were non-susceptible to levofloxacin.

INTERPRETATION

Our data suggest that the use of fluoroquinolones to treat multidrug-resistant tuberculosis in children has led to the emergence of invasive pneumococcal disease caused by levofloxacin-non-susceptible S pneumoniae and its nosocomial spread.

Resolution of Ofloxacin–Ciprofloxacin and Ofloxacin–Norfloxacin Binary Mixtures by Flow-Injection Chemiluminescence in Combination with Partial Least Squares Multivariate Calibration

A flow-injection chemiluminescence (CL) method is described for the determination of ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL), commonly used antibiotics of the fluoroquinolones family. The method is based on the CL reaction of the fluoroquinolones with tris(2,2'-bipyridyl) ruthenium(II) and Ce (IV), in sulfuric acid medium. The maximum CL emission, given at 0.45 min for CIP, at 0.35 min for NOR and at 0.04 min for OFL, respectively, were measured, allowing the simple application of the proposed method to the routine analysis of the antibiotics. The methods were applied to the determination of CIP, NOR and OFL, in several pharmaceutical preparations, with very satisfactory results, and validated by a previously reported HPLC method. The time-resolved equipment allowed the measurement of the kinetic evolution of the chemiluminescence signals. In base to the differences in the kinetic behaviour of ofloxacin with respect to ciprofloxacin and norfloxacin, binary mixtures of the drugs were resolved by using the time-resolved chemiluminescence signals, in combination with first-order partial least-squares (PLS) multivariate calibration.

Pediatric uses of fluoroquinolone antibiotics

Current data, although incomplete, suggest that pediatric administration of a fluoroquinolone, especially the best-studied ciprofloxacin, is safe. However, many experts have raised concerns regarding the emergence of fluoroquinolone-resistant pathogens such as pneumococcus if more children are treated with fluoroquinolones. Examination of the available data suggests that these concerns remain valid. Therefore, most experts continue to advise against expanded pediatric use of fluoroquinolones, except in those selected clinical situations where the benefits clearly outweigh the risks of therapy and there are few other antibiotic choices.

In vitro antibacterial activity of beta-lactams and non-beta-lactams against Streptococcus pneumoniae isolates from Sydney, Australia

AIMS

This study was undertaken to determine the antimicrobial resistance patterns of strains of Streptococcus pneumoniae from Sydney, Australia, comparing penicillin-susceptible, -intermediate and -resistant isolates.

METHODS

Non-duplicate cultures of S. pneumoniae were collected from 1 January to 31 December 2002 in the three penicillin-susceptibility categories. Minimum inhibitory concentrations (MICs) of 19 antibacterial agents were determined by agar dilution based on the National Committee for Clinical Laboratory Standards (NCCLS) methodology. Overall for 2002, 687 non-duplicate isolates were obtained, of which 190 (28%) were intermediate or resistant to penicillin. From this set, 183 isolates were selected for study: 88 (48%) in the penicillin-susceptible group (MIC <or= 0.06 mg/L), 25 (14%) in the penicillin-intermediate group (MIC 0.125-1.0 mg/L) and 70 (38%) in the penicillin-resistant group (MIC >or= 2.0 mg/L).

RESULTS

Resistance to non-beta-lactams was more common in penicillin-intermediate or -resistant strains. Multidrug resistance (resistance to >or= 2 non-beta-lactams) was found in 3% of penicillin-susceptible, 52% of penicillin-intermediate and 87% of penicillin-resistant isolates. Erythromycin resistance was seen in 22% of the penicillin-susceptible strains but increased significantly to 60% and 89% in the penicillin-intermediate and resistant strains, respectively. Clindamycin, tetracycline and trimethoprim/sulfamethoxazole showed similar diminished activity in penicillin-intermediate and -resistant strains; 64, 84 and 91% of the penicillin-resistant isolates were resistant to clindamycin, tetracycline and to trimethoprim/sulfamethoxazole, respectively. Chloramphenicol resistance was comparatively low level except 19% of the penicillin-resistant strains were resistant. Ciprofloxacin MICs for 14 strains were raised (MICs 4-16 mg/L); three of these were penicillin-susceptible, one penicillin-intermediate and 10 penicillin-resistant. Only one isolate was resistant to moxifloxacin and to gatifloxacin. Resistance to rifampicin, vancomycin, oritavancin, or linezolid was not detected. Twenty-three isolates were intermediate and one resistant to quinupristin/dalfopristin - 22 of these were penicillin resistant.

CONCLUSIONS

Streptococcus pneumoniae isolates from Sydney are commonly resistant to beta-lactams and available non-beta-lactam agents, especially if they are penicillin non-susceptible. Resistance to moxifloxacin and gatifloxacin is still rare, but some isolates were non-susceptible to quinupristin/dalfopristin. It is important to continue to survey resistance patterns to recognise emerging resistances which affect the selection of empirical antimicrobials to treat infections with S. pneumoniae.

Increase in numbers of β-lactam-resistant invasive Streptococcus pneumoniae in Brazil and the impact of conjugate vaccine coverage

A comprehensive investigation of invasive Streptococcus pneumoniae was carried out in Brazil as part of the programme of the national epidemiological surveillance system. The investigation provided data on the trends of resistance to antimicrobial agents. A total of 6470 isolates of S. pneumoniae collected in the country from 1993 to 2004 were tested. During this period of time, the number of penicillin-resistant strains rose from 10.2 to 27.9%. The proportions of intermediate and high-level resistant strains in 1993, which were 9.1 and 1.1%, respectively, rose to 22.0 and 5.9% in 2004. Geometric mean MICs for penicillin increased after the year 2000, to 0.19 microg ml(-1) in 2004; most of these isolates were from patients with pneumonia and from children under 5 years old, and belonged to serotype 14. There was a significant increase in the number of isolates belonging to serotypes included in the 7-valent conjugate vaccine from children under 5 years old: from 48.6% in 1993 to 69.6% in 2004, mainly related to an increase in the frequency of serotype 14 isolates. From 2000 to 2004, meningitis isolates showed higher resistance rates to cefotaxime (2.6%) compared to non-meningitis isolates (0.7%); percentages of isolates resistant to trimethoprim-sulfamethoxazole, tetracycline, erythromycin, chloramphenicol and rifampicin were 65, 14.6, 6.2, 1.3 and 0.7 %, respectively. No levoflaxin resistance was observed. Multidrug resistance was identified in 4.6% of isolates, of which 3.8% were resistant to three classes, 0.7% to four classes and 0.1% to five classes of antimicrobial agent. The study provides valuable information that may support empirical antimicrobial therapy for severe S. pneumoniae infections in Brazil, and emphasizes the need for conjugate pneumococcal vaccination.

Activity of gatifloxacin tested against isolates from pediatric patients: report from the SENTRY Antimicrobial Surveillance Program (North America, 1998-2003)

The SENTRY Antimicrobial Surveillance Program has monitored the activity of antimicrobial agents worldwide since 1997. The increasing number of clinical failures with established anti-infectives (penicillins, other beta-lactams, macrolides) among pediatric patients has stressed the importance for alternative therapeutic options. Ciprofloxacin has been recently approved for expanded use as treatment of complicated urinary tract infections in children, and gatifloxacin has been used successfully in clinical trials in selected children with severe or refractory otitis media. We evaluated the activity of gatifloxacin against strains isolated from children < 7 years of age and compared this to the general patient population (all ages included) using the SENTRY Program database. A total of 59826 North American isolates were collected, of which 4641 were from children (< 7 years old); all isolates were tested using reference broth microdilution methods. In contrast to the general population (GP), gatifloxacin resistance rates were very low among isolates from this younger patient group. Gatifloxacin susceptibility rates were > 84% for all pathogens evaluated in younger patients. All Streptococcus pneumoniae strains from children < 7 years old were susceptible to gatifloxacin, and susceptibility among the Enterobacteriaceae species was > 98%. The greatest difference in susceptibility rates between the younger children and the GP was observed among nonfermentative gram-negative bacilli (95.0-100% versus 64.8-83.7%, respectively) and Enterococcus faecalis (94.7% versus 58.4%). Gatifloxacin susceptibilities of Pseudomonas aeruginosa and Acinetobacter spp. isolates from the pediatric population were > or = 95% (> 97% for ciprofloxacin) compared to the GP at only 64.8-69.1%. In conclusion, gatifloxacin remains very active against bacterial isolates from children < 7 years, indicative of the limited exposure of this population to fluoroquinolones. Continued resistance surveillance will be necessary to monitor the activity of the fluoroquinolone class as they are introduced for specific clinical indications into the pediatric age groups, especially if re-studied against S. pneumoniae (refractory otitis media) and P. aeruginosa (cystic fibrosis associated pneumonia).

Molecular evolution perspectives on intraspecific lateral DNA transfer of topoisomerase and gyrase loci in Streptococcus pneumoniae, with implications for fluoroquinolone resistance development and spread

Fluoroquinolones are an important class of antibiotics for the treatment of infections arising from the gram-positive respiratory pathogen Streptococcus pneumoniae. Although there is evidence supporting interspecific lateral DNA transfer of fluoroquinolone target loci, no studies have specifically been designed to assess the role of intraspecific lateral transfer of these genes in the spread of fluoroquinolone resistance. This study involves a comparative evolutionary perspective, in which the evolutionary history of a diverse set of S. pneumoniae clinical isolates is reconstructed from an expanded multilocus sequence typing data set, with putative recombinants excluded. This control history is then assessed against networks of each of the four fluoroquinolone target loci from the same isolates. The results indicate that although the majority of fluoroquinolone target loci from this set of 60 isolates are consistent with a clonal dissemination hypothesis, 3 to 10% of the sequences are consistent with an intraspecific lateral transfer hypothesis. Also evident were examples of interspecific transfer, with two isolates possessing a parE-parC gene region arising from viridans group streptococci. The Spain 23F-1 clone is the most dominant fluoroquinolone-nonsusceptible clone in this set of isolates, and the analysis suggests that its members act as frequent donors of fluoroquinolone-nonsusceptible loci. Although the majority of fluoroquinolone target gene sequences in this set of isolates can be explained on the basis of clonal dissemination, a significant number are more parsimoniously explained by intraspecific lateral DNA transfer, and in situations of high S. pneumoniae population density, such events could be an important means of resistance spread.

Fluoroquinolone Antibiotics in Infants and Children

The use of fluoroquinolones in children is limited because of the potential of these agents to induce arthropathy in juvenile animals and to potentiate development of bacterial resistance. No quinolone-induced cartilage toxicity as described in animal experiments has been documented unequivocally in patients, but the risk fro rapid emergence of bacterial resistance associated with widespread, uncontrolled fluoroquinolones use in children is a realistic threat. Overall, the fluoroquinolones have been safe and effective in the treatment of selected bacterial infections in pediatric patients. There are clearly defined indications for these compounds in children who are ill.

Decreased levofloxacin susceptibility in Haemophilus influenzae in children, Hong Kong

Among 563 strains of Haemophilus influenzae from young children in Hong Kong, 5 (0.9%) had decreased susceptibility to quinolones. The five strains had a Ser-84-Lys or Asp-88-Asn substitution in GyrA. Pulsed-field gel electrophoresis showed that the isolates are genetically diverse.

Randomized, investigator-blinded, multicenter study of gatifloxacin versus amoxicillin/clavulanate treatment of recurrent and nonresponsive otitis media in children

BACKGROUND

Decreased susceptibility of pathogens to currently used agents for recurrent otitis media has provided the impetus for identifying new antimicrobial options.

OBJECTIVE

To compare gatifloxacin with amoxicillin/clavulanate in children with recurrent or nonresponsive acute otitis media (AOM).

METHODS

Included in this multicenter randomized trial were 413 patients, ranging in age from 6 months to 7 years, who had recurrent AOM (at least 3 episodes in the previous 6 months or 4 episodes in the previous 12 months) and/or had failed antibiotic therapy for AOM within 14 days of enrollment. Diagnosis required evidence of acute inflammation and otoscopic findings of middle ear effusion; baseline tympanocentesis was optional and encouraged. Children were randomly assigned (2:1) to 10 days of oral therapy with gatifloxacin suspension (10 mg/kg of body weight once daily) or amoxicillin/clavulanate suspension (45/6.4 mg/kg/d in 2 divided doses).

RESULTS

: Clinical cure was obtained in 90.2% (222 of 246) of patients in the gatifloxacin group and 84.3% (102 of 121) of those in the amoxicillin/clavulanate group (95% confidence interval, -1.9-12.9) 3-10 days after treatment ended. Gatifloxacin was associated with higher clinical cure rates than was amoxicillin/clavulanate in children younger than 2 years of age (92.0% versus 80.0%, respectively). Cure rates by pretreatment pathogen in the gatifloxacin and amoxicillin/clavulanate groups were 92.1% (35 of 38) versus 88.9% (16 of 18) for Streptococcus pneumoniae infections and 88.2% (30 of 34) versus 92.3% (12 of 13) for Haemophilus influenzae infections, respectively. Sustained clinical cures 3-4 weeks after treatment ended were obtained in 74.4% (183 of 246) of patients treated with gatifloxacin and 72.7% (88 of 121) of those treated with amoxicillin/clavulanate. Adverse events considered drug-related occurred with similar frequency in the 2 groups. Six patients (2.2%) in the gatifloxacin group and 2 patients (1.5%) in the amoxicillin/clavulanate group developed transient symptoms of mild or moderate arthralgia.

CONCLUSIONS

In this comparative evaluation of fluoroquinolone therapy in children with AOM, gatifloxacin was similar in clinical efficacy to amoxicillin/clavulanate 45/6.4 mg/kg/d for treatment of recurrent/nonresponsive infections.

Randomized, investigator-blinded, multicenter, comparative study of gatifloxacin versus amoxicillin/clavulanate in recurrent otitis media and acute otitis media treatment failure in children

BACKGROUND

Recurrent otitis media and acute otitis media treatment failure are commonly encountered in the pediatric population.

OBJECTIVE

To compare the clinical efficacy of gatifloxacin with amoxicillin/clavulanate for the treatment of acute otitis media treatment failure and recurrent otitis media.

METHODS

Three hundred fifty-four children 6 months-7 years with recurrent otitis media and/or acute otitis media failure were stratified according to age (younger than 2 years versus 2 years or older) and then randomly assigned to 10 days of treatment with gatifloxacin 10 mg/kg once daily or amoxicillin/clavulanate 90 mg/6.4 mg in 2 divided doses. Tympanocentesis was performed in 116 children with acute otitis media treatment failure and 52 with recurrent otitis media at study entry to validate the clinical diagnosis and provide microbiologic data. The primary outcome measure was clinical resolution of infection at the test-of-cure visit 3-10 days after completing treatment.

RESULTS

Clinical resolution of acute otitis media was observed in 79.0% (49 of 62) of clinically evaluable children younger than 2 years and 90.3% (56 of 62) of those 2 years or older who were treated with gatifloxacin as compared with 77.6% (45 of 58) of children younger than 2 years and 79.7% (47 of 59) of children 2 years or older treated with amoxicillin/clavulanate. In patients with acute otitis media treatment failure, clinical response rates for children younger than 2 years and those 2 years or older were 87.5% (21 of 24) and 97.0% (32 of 33) with gatifloxacin versus 63.6% (14 of 22) and 83.9% (26 of 31) with amoxicillin/clavulanate. The corresponding clinical response rates in patients with recurrent otitis media were 79.2% (19 of 24) and 85.7% (18 of 21) with gatifloxacin and 90.5% (19 of 21) and 76.0% (19 of 25) with amoxicillin/clavulanate. Clinical success in those subjects having pretreatment middle ear fluid pathogens was similar for the 2 regimens [80.0% (24 of 30) gatifloxacin, 77.1% (27 of 35) amoxicillin/clavulanate]. Emergence of fluoroquinolone-resistant strains was not observed. Both drugs were generally well-tolerated. Diarrhea was the most common drug-related adverse event (10% gatifloxacin, 18% amoxicillin/clavulanate). No evidence of abnormal joint or gait findings was found during a 12-month follow-up.

CONCLUSIONS

Gatifloxacin once daily is at least as effective and well-tolerated as amoxicillin/clavulanate twice daily in children with acute otitis media treatment failure or recurrent otitis media. There was no evidence of arthrotoxicity or emergence of fluoroquinolone-resistant bacteria in gatifloxacin-treated children.

Novel Antibiotic-Resistant Pneumococcal Strains Recovered from the Upper Respiratory Tracts of HIV-Infected Adults and Their Children in Kisumu, Kenya

In a survey of genetic diversity within penicillin-nonsusceptible pneumococcal isolates in Kenya, we examined 162 upper respiratory isolates from 104 human immunodeficiency virus (HIV)-infected adults and 46 children in a cotrimoxazole prophylaxis study. Antibiotic resistance levels were high; 152 (94.4%) were cotrimoxazole nonsusceptible (134 fully resistant) and 124 (77%) were intermediately penicillin resistant. Isolates nonsusceptible to penicillin and cotrimoxazole (PNCNP) were found among 24 of the 29 serotypes encountered, 15 of which have rarely or never had documented nonsusceptibility to penicillin. These included serotypes 3, 4, 7C, 7F, 10A, 11A, 13, 15A, 15B, 16F, 17F, 19B, 21, 35A, and 35B. Segments of pbp2b genes from 9 PNCNP (serotypes 3, 13, 15A, 16F, 20, and 35A) were typical of resistance-conferring alleles in that they were highly divergent and contained two substitutions thought to be critical for resistance. Similarly, the dhfr genes from 3 PNCNP were divergent and contained a substitution required for cotrimoxazole resistance. Multilocus sequence typing (MLST) of 48 PNCNP revealed 33 sequence types (STs), none of which were previously recorded at http://www.mlst.net. Comparisons with all known STs revealed that 23 of these STs were unrelated to other known STs, whereas 10 STs were highly related to STs from internationally disseminated strains, including 2 of the 26 antibiotic-resistant clones recognized by the Pneumococcal Molecular Epidemiology Network. Based upon differing serotypes expressed by strains of identical or closely similar genotypes, there has been an extensive history of capsular switching within seven genetic clusters represented by these 10 STs and related STs described at http://www.mlst.net.

Invasive Haemophilus influenzae type B diseases in Bangladesh, with increased resistance to antibiotics

OBJECTIVE

To determine the prevalence, age-group distribution, serotype, and antibiotic susceptibility patterns of invasive Haemophilus influenzae type b (Hib) isolates in Bangladeshi children because data regarding Hib diseases in developing countries are scarce, which has led to delay of the introduction of Hib vaccine in these countries.

METHODS

Children diagnosed with meningitis (n = 1412) and pneumonia (n = 2434) were enrolled in this surveillance study for Hib invasive diseases. Cerebrospinal fluid (CSF) and blood specimens, and the subsequent isolates, were processed using standard procedures.

RESULTS

During 1993 to 2003, 455 H influenzae strains were isolated from patients with meningitis (n = 425) and pneumonia (n = 30), and an additional 68 Hib meningitis cases were detected by latex agglutination (LA) testing. Overall, 35% of pyogenic meningitis cases were a result of H influenzae, 97.1% of which were Hib. Most (91.4%) cases occurred during the first year of life. Resistance to ampicillin, chloramphenicol, and cotrimoxazole was 32.5%, 21.5%, and 49.2%, respectively. There was a trend toward increasing resistance for all three drugs. Resistance to ampicillin and chloramphenicol was almost universally coexistent and was associated with increased sequelae compared with the patients infected with susceptible strains (31% [23/75] vs 11% [21/183]; P <.001).

CONCLUSION

Hib is the most predominant cause of meningitis in young Bangladeshi children. Resistance to ampicillin and chloramphenicol and the high cost of third-generation cephalosporin highlight the importance of disease prevention through vaccination against Hib.

Fluoroquinolone and other antimicrobial resistance in invasive pneumococci, Hong Kong, 1995-2001

Fluoroquinolone resistance among invasive pneumococci in Hong Kong was high and a result of clonal expansion and spread.

We determined the susceptibilities of 265 invasive isolates of pneumococci obtained during 1995 to 2001 in Hong Kong to 11 antimicrobial agents and their serotypes. Overall, 62.6% isolates were susceptible to penicillin, 20% were intermediately resistant, and 17.4% were resistant. The overall prevalence of levofloxacin resistance (MIC >8 µg/mL) was 3.8% but increased to 15.2% among the penicillin-resistant isolates. All levofloxacin-resistant isolates were clonally related; had reduced susceptibility to penicillin, cefotaxime, and clarithromycin; and were derived from adults >50 years of age. Of the penicillin-nonsusceptible pneumococci, 90% from children <5 years of age and 54.8% from persons of all ages were of serotypes that are included in the 7-valent pneumococcal conjugate vaccine; 93.5% from children <5 years of age and 93% from persons of all ages were of serotypes that are included in the 23-valent polysaccharide vaccine.

Antibacterial agents in pediatrics

Antibiotics are among the most widely prescribed therapeutic agents in children. Several new trends in antibiotic usage for pediatric care have emerged. New mechanisms of antibacterial resistance have required a broader repertoire of antibiotic usage, including new agents directed at multidrug resistance. After promotion of judicious antibiotic use, there has been a decline in the number of pediatric prescriptions for antibiotics. Recent legislation addresses the necessity for pediatric clinical drug trials, ensuring development of further antibacterial agents for use in pediatric patients.

Activity of telithromycin and comparators against bacterial pathogens isolated from 1,336 patients with clinically diagnosed acute sinusitis

Background

Increasing antimicrobial resistance among the key pathogens responsible for community-acquired respiratory tract infections has the potential to limit the effectiveness of antibiotics available to treat these infections. Since there are regional differences in the susceptibility patterns observed and treatment is frequently empirical, the selection of antibiotic therapy may be challenging. PROTEKT, a global, longitudinal multicentre surveillance study, tracks the activity of telithromycin and comparator antibacterial agents against key respiratory tract pathogens.

Methods

In this analysis, we examine the prevalence of antibacterial resistance in 1,336 bacterial pathogens, isolated from adult and paediatric patients clinically diagnosed with acute bacterial sinusitis (ABS).

Results and discussion

In total, 58.0%, 66.1%, and 55.8% of S. pneumoniae isolates were susceptible to penicillin, cefuroxime, and clarithromycin respectively. Combined macrolide resistance and reduced susceptibility to penicillin was present in 200/640 (31.3 %) of S. pneumoniae isolates (128 isolates were resistant to penicillin [MIC >= 2 mg/L], 72 intermediate [MIC 0.12–1 mg/L]) while 99.5% and 95.5% of isolates were susceptible to telithromycin and amoxicillin-clavulanate, respectively. In total, 88.2%, 87.5%, 99.4%, 100%, and 100% of H. influenzae isolates were susceptible to ampicillin, clarithromycin, cefuroxime, telithromycin, and amoxicillin-clavulanate, respectively. In vitro, telithromycin demonstrated the highest activity against M. catarrhalis (MIC₅₀ = 0.06 mg/L, MIC₉₀ = 0.12 mg/L).

Conclusion

The high in vitro activity of against pathogens commonly isolated in ABS, together with a once daily dosing regimen and clinical efficacy with 5-day course of therapy, suggest that telithromycin may play a role in the empiric treatment of ABS.

Clinical relevance of antimicrobial resistance in the management of pneumococcal community-acquired pneumonia

Streptococcus pneumoniae remains the most common bacterial cause of community-acquired pneumonia, and these infections are associated with significant morbidity and mortality worldwide. A major concern is the increasing incidence of antibiotic resistance among pneumococcal isolates, which, in the case of certain of the antibiotic classes, has been associated with treatment failure. Yet despite multiple reports of infections with penicillin-resistant pneumococcal isolates, no cases of bacteriologic failure have been documented with the use of penicillin or ampicillin in the treatment of pneumonia caused by penicillin-resistant pneumococci. Current prevalence and levels of penicillin resistance among pneumococal isolates in most areas of the world do not indicate a need for substantial treatment changes with regard to the use of the penicillins. For infections with penicillin-sensitive strains, penicillin or an aminopenicillin in a standard dosage will still be effective for treatment. In the cases of strains with intermediate resistance, beta-lactam agents are still considered appropriate treatment, although higher dosages are recommended. Infections with isolates of high-level penicillin resistance should be treated with alternative agents such as the third-generation cephalosporins or the new antipneumococcal fluoroquinolones. In the case of the cephalosporins, pharmacodynamic/pharmacokinetic parameters help predict which of those agents are likely to be successful, and the less active agents should not be used. Debate continues in the literature with regard to the impact of macrolide resistance on the outcome of pneumococcal pneumonia, with some investigators providing evidence of an "in vivo-in vitro paradox," referring to discordance between reported in vitro resistance and clinical success of macrolides/azalide in vivo. However, several cases of macrolide/azalide treatment failure have been documented, and many clinicians recommend that these agents not be used on their own in areas with a high prevalence and levels of macrolide/azalide resistance. However, evidence is emerging to show beneficial effects on outcome with combination therapy, especially that of a beta-lactam agent and a macrolide given together to sicker, hospitalized patients with pneumococcal pneumonia. In an attempt to prevent the emergence of resistance, it has been recommended by some that the new fluoroquinolones not be used routinely as first-line agents in the treatment of community-acquired pneumonia; instead, they say, these agents should be reserved for patients who are allergic to the commonly used beta-lactam agents, for infections known to be or suspected of being caused by highly resistant strains, and for patients in whom initial therapy has failed.

Optimizing antibacterial therapy for community-acquired respiratory tract infections in children in an era of bacterial resistance

The spread of antibacterial resistance in bacteria that commonly cause childhood community-acquired respiratory tract infections (RTIs), such as acute otitis media, community-acquired pneumonia, and acute pharyngitis, is a major healthcare problem. One of the foremost concerns is the rapid increase in penicillin, macrolide, and multidrug resistance in Streptococcus pneumoniae. There is also a rising prevalence of macrolide resistance in Streptococcus pyogenes in pockets of the United States, and beta-lactamase production in Haemophilus influenzae is widespread. Although data are limited, some evidence suggests that resistance to antibacterials can impair bacteriologic and clinical outcomes in childhood RTIs. Optimizing antibacterial use is important both in the care of individual patients and within strategies to address the wider problem of antibacterial resistance. This involves encouraging judicious antibacterial use (i.e., reducing overuse for viral infection and prophylaxis), and preventing misuse through the wrong choice, dosage, and duration of therapy. Given that initial therapy is usually empiric, antibacterials used to treat community-acquired RTIs in children should ideally have the following properties: an optimal targeted spectrum of activity; high clinical and bacteriologic efficacy against respiratory pathogens, including resistant strains; simple, short-course therapy; and good tolerability and palatability. New antibacterials will continue to have a role in the treatment of RTIs in children, especially where resistance compromises existing therapies.

Antimicrobial resistance among pediatric respiratory tract infections: clinical challenges

Considerable development of antimicrobial resistance has occurred in the major pediatric bacterial pathogens, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. However, most of the respiratory infections that children suffer are viral and self-limiting, and only a small percentage of them will develop secondary bacterial infections with the pathogens listed. The challenge for rational antibiotic use is to determine which patients can be treated conservatively and which require antimicrobial intervention to avoid prolonged discomfort or development of permanent sequelae. The basis for rational use of antibiotic in the era of resistance in these major pathogens is to avoid overuse of antimicrobial agents, tailor treatment to identified pathogens as much as possible, and base empiric treatment on the disease being treated and the susceptibility of the probable pathogens at breakpoints based on pharmacokinetic and pharmacodynamic parameters. With appropriate dosing regimens based on these parameters and despite development of resistance, amoxicillin is still one of the most active oral agents against S. pneumoniae and non-beta-lactamase producing strains of H. influenzae, whereas amoxicillin-clavulanate is active against beta-lactamase-producing strains of H. influenzae and M. catarrhalis. Parenteral ceftriaxone and oral and parenteral fluoroquinolones are active against all 3 species, but fluoroquinolones should be used with utmost caution when all other options have been considered because of concerns about toxicity and development of resistance. Introduction of a 7-valent conjugate pneumococcal vaccine in the United States in 2000 reduced the prevalence of invasive pneumococcal disease in children younger than 2 years old, but, as of 2001, had not had a major impact on decreasing antimicrobial resistance.

Fluoroquinolone AUIC Break Points and the Link to Bacterial Killing Rates Part 2: Human Trials

OBJECTIVE

To review clinical trials with fluoroquinolones and the pharmacokinetic and pharmacodynamic parameters predictive of clinical and microbiologic outcomes and resistance. Data on fluoroquinolones are summarized and the premise that a single AUIC target >125 may be used for all fluoroquinolones against all target organisms is examined.

DATA SOURCES

Primary articles were identified by a MEDLINE search (1966-February 2002) and through secondary sources.

STUDY SELECTION AND DATA EXTRACTION

All of the articles identified from the data sources were evaluated and all information deemed relevant was included.

DATA SYNTHESIS

The fluoroquinolones exhibit concentration-dependent killing. This effect clearly depends upon concentrations achieved and outcomes depend upon endpoints established by individual investigators. With AUIC values <60, the actions of fluoroquinolones are essentially bacteriostatic; any observed bacterial killing is the combined effect of low concentrations in relation to minimum inhibitory concentration and the action of host factors such as neutrophils and macrophages. AUIC values >100 but <250 yield bacterial killing at a slow rate, but usually by day 7 of treatment. AUICs >250 produce rapid killing, and bacterial eradication occurs within 24 hours. Disagreements regarding target endpoints are the expected consequences of comparing microbial and clinical outcomes across animal models, in vitro experiments (Part 1), and humans when the endpoints are clearly not equivalent. Careful attention to time-related events such as speed of bacterial killing versus global endpoints such as bacteriologic cure allows optimal break points to be defined.

CONCLUSIONS

Evidence from human trials favors the use of AUIC values >250 for rapid bactericidal action, regardless of whether the organism is gram-negative or gram-positive.

Fluoroquinolones in paediatrics: a risk for the patient or for the community?

Fluoroquinolones are an important group of antibiotics widely used in adult patients because of their excellent tissue penetration and their bactericidal activity. They are not authorised for paediatric use (except the limited indication of pseudomonas infections in cystic fibrosis), however, because of the potential for joint toxicity reported from experiments with young animals. Despite the absence of official approval, fluoroquinolones are widely used in paediatrics as second-line antibiotics when all other treatments have failed. Most of the information available about paediatric use concerns ciprofloxacin, which is used in children much more often than the other members of this class. The published paediatric series have shown that frequency of articular side-effects varies according to age: all the surveys have reported frequencies of around 0.1% in adults and 2-3% in children. Outside of cystic fibrosis and severe infections in which no other treatment is possible, the only paediatric situations where fluoroquinolones are superior to standard treatments for children, in speed of recovery and comfort as well as in efficacy, are typhoid fever, severe shigella dysenteries, and enterobacteria meningitis. Should the use of new fluoroquinolones active against pneumococci be authorised for upper respiratory infections (including recurrent otitis) in children, the potential emergence and dissemination of pneumococci strains in which multidrug resistance includes fluoroquinolones would create a real risk in the community. It is, therefore, important to continue the policy of second-line use in children, only after failure of an earlier treatment, and when other antibiotics approved for paediatric use cannot be used.

Susceptibilities to levofloxacin in Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis clinical isolates from children: results from 2000-2001 and 2001-2002 TRUST studies in the United States

Among respiratory tract isolates of Streptococcus pneumoniae from children, resistance to penicillins, cephalosporins, macrolides, and trimethoprim-sulfamethoxazole (SXT) increases on an annual basis. Pediatric patients who do not respond to conventional therapy for respiratory tract infections someday may be treated with fluoroquinolones. In this study, MICs of beta-lactams, azithromycin, SXT, and levofloxacin were determined and interpreted by using NCCLS guidelines for isolates of S. pneumoniae (2,834 from children and 10,966 from adults), Haemophilus influenzae (629 from children and 2,281 from adults), and Moraxella catarrhalis (389 from children and 1,357 from adults) collected during the 2000-2001 and 2001-2002 respiratory illness seasons in the United States as part of the ongoing TRUST surveillance studies. Rates of resistance to penicillin, azithromycin, and SXT were > or = 7.5% higher among patients < or = 4 years old than among patients 5 to 10, 11 to 17, and > or = 18 years old in both the 2000-2001 and the 2001-2002 respiratory illness seasons. Levofloxacin resistance was detected in 2 of 2,834 isolates (0.07%) from patients <18 years old. Levofloxacin MICs of 0.25 to 1 micro g/ml accounted for 99.6, 99.5, 99.3, 99.7, 98.4, and 98.0% of isolates from patients < 2, 2 to 4, 5 to 10, 11 to 17, 18 to 64, and > 64 years old. Multidrug resistance was twice as common among patients < or = 4 years old (25.3%) as among patients 5 to 10 years old (13.7%), 11 to 17 years old (11.9%), 18 to 64 years old (12.1%), and > 64 years old (12.4%). The most common multidrug resistance phenotype in S. pneumoniae isolates for all age groups was resistance to penicillin, azithromycin, and SXT (70.3 to 76.6%). For H. influenzae and M. catarrhalis isolates from patients < 2, 2 to 4, 5 to 10, 11 to 17, 18 to 64, and > 64 years old, levofloxacin MICs at which 90% of the isolates were inhibited were 0.015 and 0.03 to 0.06 microg/ml, respectively, in the 2000-2001 and 2001-2002 respiratory illness seasons. In the 2000-2001 and 2001-2002 respiratory illness season surveillance studies in the United States, 99.9% of pediatric isolates of S. pneumoniae were susceptible to levofloxacin. If fluoroquinolones become a treatment option for pediatric patients, careful monitoring of fluoroquinolone susceptibilities will be increasingly important in future surveillance studies.

Fluoroquinolone resistance among Gram-positive cocci

Resistance to fluoroquinolones among Gram-positive cocci has emerged as these antimicrobial agents have become extensively used in clinical medicine. Resistance is effected by changes in the bacterial target enzymes DNA gyrase and topoisomerase IV, which reduce drug binding, and by action of native bacterial membrane pumps that remove drug from the cell. In both cases, quinolone exposure selects for spontaneous mutants that are present in large bacterial populations, and which contain chromosomal mutations that alter the target protein or increase the level of pump expression. Resistance among clinical isolates has been greatest in Staphylococcus aureus and particularly among meticillin-resistant strains, in which both selection by quinolone exposure and transmission of clonal strains in health-care settings have contributed to high prevalence. Resistance in Streptococcus pneumoniae has also emerged in the community. Fluoroquinolone resistance has arisen in multidrug-resistant clones and its prevalence has been especially high in Hong Kong and Spain. Further spread and selection of such resistance could compromise the utility of a valuable class of antimicrobial agents, a point that emphasises the importance of the careful use of these agents in appropriate patients and doses, as well as careful infection-control practices.