Trends in the antimicrobial susceptibility of bacterial respiratory tract pathogens--findings of the Alexander Project 1992-1996

Exploration of space to achieve scientific breakthroughs

Living organisms adapt to changing environments using their amazing flexibility to remodel themselves by a process called evolution. Environmental stress causes selective pressure and is associated with genetic and phenotypic shifts for better modifications, maintenance, and functioning of organismal systems. The natural evolution process can be used in complement to rational strain engineering for the development of desired traits or phenotypes as well as for the production of novel biomaterials through the imposition of one or more selective pressures. Space provides a unique environment of stressors (e.g., weightlessness and high radiation) that organisms have never experienced on Earth. Cells in the outer space reorganize and develop or activate a range of molecular responses that lead to changes in cellular properties. Exposure of cells to the outer space will lead to the development of novel variants more efficiently than on Earth. For instance, natural crop varieties can be generated with higher nutrition value, yield, and improved features, such as resistance against high and low temperatures, salt stress, and microbial and pest attacks. The review summarizes the literature on the parameters of outer space that affect the growth and behavior of cells and organisms as well as complex colloidal systems. We illustrate an understanding of gravity-related basic biological mechanisms and enlighten the possibility to explore the outer space environment for application-oriented aspects. This will stimulate biological research in the pursuit of innovative approaches for the future of agriculture and health on Earth.

Patterns of Macrolide Resistance Determinants among S. pyogenes and S. pneumoniae Isolates in Saudi Arabia

In the study we characterized the macrolide sensitivity of recent clinical isolates of Streptococcus pyogenes and S. pneumoniae collected from major Saudi Arabian hospitals. Susceptibility testing was performed using standard National Committee for Clinical Laboratory Standards methodology on 335 S. pyogenes and 350 S. pneumoniae isolates. Macrolide resistance mechanism phenotypes were identified using double-disk diffusion. All S. pyogenes were penicillin sensitive, while 6.3% were macrolide resistant, the main mechanism of which was of M phenotype (96%). Approximately 51% of S. pneumoniae were penicillin non-susceptible. Macrolide resistance in S. pneumoniae accounted for 18.8%, the majority of which were M phenotype (91%). Low-level resistance mediated by mef-bearing strains predominated. Newer macrolides, including azithromycin, are still considered drugs of choice for empirical treatment of respiratory infection in such circumstances.

Antimicrobial susceptibility and genetic characteristics of Haemophilus influenzae isolated from community-acquired respiratory tract infection patients in Shanghai City, China

Haemophilus influenzae is an important causative pathogen of community-acquired respiratory infection in China. In this study we investigated 37 H. influenzae strains isolated from patients with community-acquired respiratory tract infections (CARTI) in Shanghai city between Dec 2008 and Apr 2009. H. influenzae clinical isolates were identified, and b-lactamase production tests were conducted and minimal inhibitory concentrations(MIC) were measured. Pulsed-field gel electrophoresis(PFGE) was introduced as an effective finger printing method. Two isolates (5.4%) were verified as serotype b strains, and 30 strains (81.1%) were nontypeable H. influenzae. Furthermore, 10 (27.0%) were b-lactamase-producing ampicillin-resistance (BLPAR) (TEM-1 type)strains, 11 (29.8%) were low-b-lactamase-nonproducing ampicillin-resistant H. influenzae (Low-BLNAR) strains,and the rest were b-lactamase-negative ampicillin-susceptible(BLNAS) strains. Minimum inhibitory concentrations(MIC90; lg/ml) were 2 for ampicillin/sulbactam, 0.05 force fotaxime, 16 for cefaclor, 2 for azithromycin, 0.12 for levofloxacin, and 4 for imipenem. Fingerprint typing by PFGE revealed 23 independent patterns for the isolates. Pattern A (defined in this study) was predominant in BLPAR strains, and a variety of other patterns were detected in Low-BLNAR and BLNAS strains. Although the incidence of ampicillin resistant H. influenzae is increasing in CARTI patients in China, current antimicrobial chemotherapy seems to be effective.

Clonal spread of beta-lactamase-producing amoxicillin-clavulanate-resistant (BLPACR) strains of non-typeable Haemophilus influenzae among young children attending a day care in Japan

OBJECTIVE

Resistant strains of non-typeable Haemophilus influenzae (NTHi) are one of the principal causes of recurrent acute otitis media (otitis prone), rhinosinusitis, and pneumonia in young children. Beta-lactamase-nonproducing ampicillin-resistant (BLNAR) strains are particularly common in Japan, and beta-lactamase-producing amoxicillin-clavulanate resistant (BLPACR) strains are now emerging. We investigated the nasopharyngeal carriage status of these resistant strains among children attending a same day care center during a 10-year period.

METHODS

From 1999 to 2008, we obtained nasopharyngeal swab specimens from young children attending a same day care center and examined the incidence of resistant strains of NTHi. Antimicrobial resistance of NTHi was identified based on PCR analysis of mutation of the penicillin binding protein (PBP) genes. Pulsed-field gel electrophoresis (PFGE) was performed to examine the clonal relationship of each resistant strain.

RESULTS

The prevalence of resistant strains of NTHi among the children attending this day care has significantly increased during the past 10 years and most of this day care children recently have resistant strains with PBP gene mutations in their nasopharynx. Genetically BLPACR (gBLPACR) strains have rapidly increased since 2007 and PFGE analysis demonstrated that all gBLPACR were clonally identical. This is the first report of apparent clonal dissemination of gBLPACR strains of NTHi occurring in a certain environment such as day care.

CONCLUSIONS

The rapidly increasing prevalence of resistant strains, in particular gBLPACR, in this day care center may predict a high incidence of these resistant bacteria from clinical isolates in the near future and potential serious medical problems worldwide.

Amoxicillin and amoxicillin plus clavulanate: a safety review

Despite the considerable number of newer antibacterials made available over the past decades, amoxicillin, alone or in combination with clavulanic acid, still accounts among the most widely used antibacterial agents. Although they are often considered 'twin drugs', they are different both in terms of antibacterial activities and of safety profile. It is well documented that the clavulanate component may cause adverse reactions by itself, thus exposing patients to further, and sometimes undue, risks. Although amoxicillin/clavulanate should be considered as an alternative agent only for the treatment of resistant bacteria, evidence shows that it is often used also when a narrow-spectrum antibiotic would have been just as effective. This prescription habit may have serious consequences in terms of patients' safety, as well as in terms of the development of bacterial resistance.

Low incidence of antibiotic resistance among invasive and nasopharyngeal isolates of Streptococcus pneumoniae from children in rural Philippines between 1994 and 2000

The purpose of this study was to determine the prevalence of acquired antimicrobial resistance in Streptococcus pneumoniae isolated from nasopharyngeal swabs and blood and cerebrospinal fluid (CSF) specimens of 3,028 children hospitalized with signs or symptoms of pneumonia, sepsis, or meningitis in rural Philippines between 1994 and 2000. Pneumococci were identified using standard methods, serotyped, and their susceptibility to oxacillin, erythromycin, tetracycline, chloramphenicol, and trimethoprim-sulfamethoxazole was determined using the disk diffusion method. Penicillin minimum inhibitory concentrations (MICs) of the oxacillin-resistant isolates were further tested. The clonality of the penicillin-nonsusceptible (PNSP) isolates was analyzed using pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Altogether 1,048 isolates were analyzed, of which 35 were invasive and 1,013 nasopharyngeal isolates. None was resistant, but 22 (2.1%) were intermediately resistant to penicillin, 4 (0.2%) were resistant to chloramphenicol, 3 (0.2%) to erythromycin, 39 (3.7%) to tetracycline, and 4 (0.2%) to trimethoprim/sulfamethoxazole. Twelve of the 22 PNSP isolates were of serotype 14 and of sequence type 63. These included the two invasive PNSP isolates. PFGE profiling further identified three separate clusters among the sequence of type 63, serotype 14 (ST63(14)) isolates. Antimicrobial resistance in both invasive and nasopharyngeal pneumococcal pediatric isolates in rural Philippines is rare. In spite of this remote setting, the PNSP isolates of the serotype 14 clusters were of ST63 type, which has been described previously on other continents.

Galactose residues on the lipooligosaccharide of Moraxella catarrhalis 26404 form the epitope recognized by the bactericidal antiserum from conjugate vaccination

Lipooligosaccharide (LOS) from Moraxella catarrhalis has the potential to elicit bactericidal antibodies against the pathogen. We generated LOS-based conjugate vaccines that elicited bactericidal antibodies in animal models. However, epitopes on the LOS recognized by the functional anti-LOS antibodies remain unidentified. In this study, a mutant strain, D4, which lost the recognition by a bactericidal anti-LOS rabbit serum in Western blotting was generated from a serotype C strain 26404 by random transposon mutagenesis. Sequence analysis revealed there was an insertion of a kanamycin resistance gene in the lgt2 gene of D4, which encodes beta(1-4)-galactosyltransferase. An isogenic lgt2 mutant, 26404lgt2, was constructed. Structural analysis indicated that the mutant strain produced a truncated LOS lacking terminal galactoses from 4- and 6-linked oligosaccharide chains of strain 26404. Further studies showed that the antiserum lost the recognition of both mutant cells and LOSs in Western blotting, an enzyme-linked immunosorbent assay (ELISA), or a flow cytometry assay. The antiserum also lost the ability to kill the mutant strain in a bactericidal assay, whereas it showed a bactericidal titer of 1:80 to strain 26404. In an inhibition ELISA, d-(+)-galactose or 26404lgt2 LOS showed no inhibition. However, the 26404 LOS and a serotype A O35E LOS with terminal galactoses on its 6-linked oligosaccharide chain showed >90% inhibition, while a serotype B 26397 LOS showed >60% inhibition. These studies suggest that the terminal alpha-Gal-(1-->4)-beta-Gal on the 6-linked oligosaccharide chain of 26404 LOS plays a critical role in forming the epitope recognized by the bactericidal antiserum induced by immunization with our conjugate vaccine.

Positive selection in penicillin-binding proteins 1a, 2b, and 2x from Streptococcus pneumoniae and its correlation with amoxicillin resistance development

The efficacy of beta-lactam antibiotics in Streptococcus pneumoniae has been compromised because of the development of altered penicillin-binding proteins (PBPs), however, this has been less so for amoxicillin than for penicillin. Recently, there have been a number of important methods developed to detect molecular adaptation in protein coding genes. The purpose of this study is to employ modern molecular selection approaches to predict sites under positive selection pressure in PBPs, derived from a large international S. pneumoniae collection of amoxicillin resistant and susceptible isolates, and encompassing a comparative data set of 354 pbp1a, 335 pbp2b, and 389 pbp2x gene sequences. A correspondence discriminant analysis (CDA) of positively selected pbp sites and amoxicillin MIC (minimum inhibitory concentration) values is then used to detect sites under positive selection pressure that are important in discriminating different amoxicillin MICs. Molecular adaptation was evident throughout PBP2X, with numerous positively selected sites in both the transpeptidase (TP) and C-terminal domains, strongly correlated with discriminating amoxicillin MICs. In the case of PBP1A positive selection was present in the glycosyltransfer (GT), TP and C-terminal domains. Sites within the TP domain tended to be correlated with the discrimination of low from intermediate MICs, whereas sites within the C-terminal tail, with a discrimination of intermediate from fully resistant. Most of the positively selected sites within PBP2B were in the N-terminal domain and were not correlated with amoxicillin MICs, however, several sites taken from the literature for the TP domain were strongly associated with discriminating high from intermediate level amoxicillin resistance. Many of the positively selected sites could be directly associated with functional inferences based on the crystal structures of these proteins. Our results suggest that clinical emphasis on TP domain sequences of these proteins may result in missing information relevant to antibiotic resistance development.

Emergence and trends of penicillin non-susceptible Streptococcus pneumoniae in Saudi Arabia and Kuwait - perspective and outstanding issues

For many years in the past Streptococcus pneumoniae was uniformly susceptible to penicillin until the sudden and unexpected emergence of clinical infections caused by penicillin-resistant S. pneumoniae (PRSP) in 1967. Within the following decade, reports of nosocomial and community outbreaks of infections due to PRSP became widespread all over the world. Recent reports suggest that the incidence of resistance rates is rising in many countries although there are geographical variations in the prevalence and patterns of resistance between countries. The problem of antibiotic resistance is further compounded by the emergence of resistance to many beta-lactam antibiotics. The first report of PRSP in Saudi Arabia was in 1991. Barely a year after, PRSP infection was reported in Kuwait in 1992. Since then, studies from various parts of these countries have recorded prevalence rates ranging from 6.2% in Riyadh to 34% in Jeddah and 20% to 56% in neighboring Kuwait. These suggest considerable variation in the prevalence of PRSP in different cities in the Saudi Kingdom and Kuwait. The mechanism of resistance is due to chromosomally mediated alteration of penicillin-binding proteins (PBPs), which are target sites for beta-lactam antibiotics. It would appear that the spread of PRSP strains in Saudi Arabia is driven by the selective pressure created by excessive use and misuse of antimicrobial agents made possible by the easy availability of these agents, often frequently obtainable over the counter. In Kuwait, irrational and misguided use of antibiotics may be the major driving force favoring the spread of PRSP. The serotypes of strains encountered in Saudi Arabia and Kuwait are almost identical, with serotypes 19, 6, 15, 14 and 23 being the most common; together they constitute about 70% of the isolates circulating in these countries. In general, almost 90% of the serotypes included in the 23-polyvalent vaccine are present in the general population. However, a much lower percentage of these serotypes is found in the conjugated vaccines, which are more relevant to our communities. This paper reviews the emergence and the steady increase in the prevalence of penicillin-resistant pneumococcal strains in Saudi Arabia and Kuwait during the last 10 years. It discusses the trends, mechanisms of resistance and factors associated with the emergence, dissemination, and colonization of resistant organisms and suggests options available to clinicians for management of infections due to PRSP.

National and regional assessment of antimicrobial resistance among community-acquired respiratory tract pathogens identified in a 2005-2006 U.S. Faropenem surveillance study

Surveillance studies conducted in the United States over the last decade have revealed increasing resistance among community-acquired respiratory pathogens, especially Streptococcus pneumoniae, that may limit future options for empirical therapy. The objective of this study was to assess the scope and magnitude of the problem at the national and regional levels during the 2005-2006 respiratory season (the season when community-acquired respiratory pathogens are prevalent) in the United States. Also, since faropenem is an oral penem being developed for the treatment of community-acquired respiratory tract infections, another study objective was to provide baseline data to benchmark changes in the susceptibility of U.S. respiratory pathogens to the drug in the future. The in vitro activities of faropenem and other agents were determined against 1,543 S. pneumoniae isolates, 978 Haemophilus influenzae isolates, and 489 Moraxella catarrhalis isolates collected from 104 U.S. laboratories across six geographic regions during the 2005-2006 respiratory season. Among S. pneumoniae isolates, the rates of resistance to penicillin, amoxicillin-clavulanate, and cefdinir were 16, 6.4, and 19.2%, respectively. The least effective agents were trimethoprim-sulfamethoxazole (SXT) and azithromycin, with resistance rates of 23.5 and 34%, respectively. Penicillin resistance rates for S. pneumoniae varied by region (from 8.7 to 22.5%), as did multidrug resistance rates for S. pneumoniae (from 8.8 to 24.9%). Resistance to beta-lactams, azithromycin, and SXT was higher among S. pneumoniae isolates from children than those from adults. beta-Lactamase production rates among H. influenzae and M. catarrhalis isolates were 27.4 and 91.6%, respectively. Faropenem MICs at which 90% of isolates are inhibited were 0.5 mug/ml for S. pneumoniae, 1 mug/ml for H. influenzae, and 0.5 mug/ml for M. catarrhalis, suggesting that faropenem shows promise as a treatment option for respiratory infections caused by contemporary resistant phenotypes.

The relative frequency of intraspecific lateral gene transfer of penicillin binding proteins 1a, 2b, and 2x, in amoxicillin resistant Streptococcus pneumoniae

Evidence exists for both interspecific and intraspecific recombination (lateral gene transfer; LGT) involving Streptococcus pneumoniae pbp (penicillin binding protein) loci. LGT of capsular genes, or serotype switching, is also know to occur between S. pneumoniae of different serotype. It is not clear whether intraspecific pbp LGT is relatively common, whether there is a difference in the relative frequency of intraspecific LGT of different pbps, and whether serotype switching is more or less frequent than pbp LGT. The purpose of this study was to use comparative evolutionary biology analysis of 216 international clinical S. pneumoniae isolates, from the Alexander Project collection, to gain insight on these issues, as well as the possible role they might be playing in spreading amoxicillin resistance. All 216 isolates were genotyped using MLST and complete or nearly complete sequences for pbp1a, pbp2b, and pbp2x were determined. Amoxicillin MICs were available for each isolate. pbps were genotyped using phylogenetics and two or more pbp types within a MLST sequence type (ST) or clonal complex were taken as putative cases of pbp LGT; these hypotheses were statistically evaluated using the approximately unbiased (AU) test. Serotypes were determined for 171 of these isolates and the minimum number of switching events necessary to explain the serotype phenotypes for each of the STs and clonal complexes were evaluated. The majority (78%) of the amoxicillin resistant isolates were comprised in 5 clonal complexes. The relative frequency of pbp LGT was greatest for pbp2b and 2x (minimum of 10.2 and 7.8%, respectively, of the isolates consistent with the LGT hypothesis), followed by 1a (3.9%). Serotype switching was more frequent than intraspecific pbp LGT (33% of isolates consistent with serotype switching hypothesis). Although intraspecific LGT of pbps is occurring and has played a role in the spread of amoxicillin resistance in S. pneumoniae, clonal dissemination appears to be more significant.

Microbiology and Principles of Antimicrobial Therapy for Head and Neck Infections

The principles of antimicrobial management for head and neck infections include establishing an accurate clinical and microbiologic diagnosis and treating the patient initially with an empiric antimicrobial regimen based on predicted likelihood of success and reduced potential for resistance. Subsequent adjustments may be required based on clinical response and available culture results. This article summarizes the aerobic and anaerobic microbiology of selected acute and chronic infections of the head and neck and the approaches to antimicrobial therapy.

Activity of faropenem against middle ear fluid pathogens from children with acute otitis media in Costa Rica and Israel

Faropenem was tested against 1,188 middle ear fluid pathogens from children in Israel and Costa Rica. Against Streptococcus pneumoniae and Haemophilus influenzae, faropenem was the most active beta-lactam, with activity that was similar to or greater than of the other oral antimicrobial classes studied. Faropenem was also active against Moraxella catarrhalis and Streptococcus pyogenes.

Antimicrobial susceptibility of common pathogens from community-acquired lower respiratory tract infections in Estonia

Antimicrobial resistance among clinical isolates of Streptococcus pneumoniae (n = 49), Haemophilus influenzae (n = 66) and Moraxella catarrhalis (n = 25) from adults with community-acquired lower respiratory tract infections (CALRTI) was assessed in a national surveillance study in Southern Estonia during 2000-2003. In S. pneumoniae, no penicillin resistance and only 2.0% resistance to clarithromycin was present, although intermediate resistance to trimethoprim-sulphamethoxazole (TMP-SMX) reached 24.5%. Beta-lactamase production rate was 96.0% in M. catarrhalis, but only 3.0% in H. influenzae. Both Gram-negative strains lacked resistance to ciprofloxacin. Clarithromycin resistance was 12% in M. catarrhalis but lacking among H. influenzae (except for 18.2% intermediate resistance). Resistance to TMP-SMX was 12.0% and 24.2% in M. catarrhalis and H. influenzae, respectively. In summary, a favorable resistance pattern of the main CALRTI pathogens is preserved in Estonia to core antibacterials. Nevertheless, use of TMP-SMX in CALRTI is discouraged and clinical response should be carefully monitored, when clarithromycin is chosen against M. catarrhalis or H. influenzae.

Characterization of macrolide resistance in Gram-positive cocci from Colombian hospitals: a countrywide surveillance

OBJECTIVE

The characterization of macrolide resistance in Gram-positive cocci recovered from Colombian hospitals.

METHODS

The resistance profiles and mechanism of macrolide resistance were investigated in isolates of Streptococcus pneumoniae (1679), Staphylococcus aureus (348), coagulase-negative staphylococci (CoNS) (175), and Enterococcus spp (123). Minimum inhibitory concentrations (MICs) for erythromycin (ERY) and clindamycin (CLI), detection of macrolide resistance genes, phenotypic characterization, and pulsed field gel electrophoresis (PFGE) of macrolide-resistant pneumococci were performed.

RESULTS

Resistance to ERY and CLI was 3.3% and 2.3% for S. pneumoniae, 58% and 57% for S. aureus (94% for both compounds in methicillin-resistant Staphylococcus aureus (MRSA)), and 78.6% and 60.7% in methicillin-resistant Staphylococcus epidermidis, respectively. ERY resistance was 62% in Enterococcus faecalis and 82% in Enterococcus faecium. The MLS(B)-type accounted for 71% of S. pneumoniae and 100% of MRSA. The erm(A) gene was prevalent in MRSA, erm(B) in S. pneumoniae and enterococci, and erm(C) in CoNS isolates. Efflux pump genes (mef(A) genes) were mostly identified in S. pneumoniae (24%). The most common genotype amongst ERY-resistant pneumococci was the Spain(6B)-2 clone.

CONCLUSIONS

The prevalence of macrolide resistance is low in Colombian pneumococci and high in MRSA (cMLS(B)-type).

Comparison of the serological responses to Moraxella catarrhalis immunoglobulin D-binding outer membrane protein and the ubiquitous surface proteins A1 and A2

Moraxella catarrhalis immunoglobulin D-binding protein (MID) is a complex antigen with unique immunoglobulin D (IgD)-binding, adhesion, and hemagglutination properties. Previous studies have shown that antibodies raised against MID764-913 in rabbits inhibited M. catarrhalis adhesion to human alveolar epithelial cells, and immunization with MID764-913 resulted in an increased pulmonary clearance in a murine model. Strong immune responses against MID have also consistently been shown in humans. Here, the MID-specified IgG responses were compared to those of ubiquitous surface proteins A1 and A2 (UspA1/A2) using a series of recombinant fragments that spanned all three proteins. Sera were obtained from young children, aged 6 months to 1 year (n=8) and 2 to 3 years (n=15), and healthy adults (n=16). Acute- and convalescent-phase sera from chronic obstructive pulmonary disease (COPD) patients with M. catarrhalis infective exacerbations (n=23) were also analyzed. Young children, who are at risk of M. catarrhalis infection, had low levels of anti-MID and anti-UspA1/A2 antibodies. Healthy adults and the majority of COPD patients (16/23) had high levels of antibodies directed against, among others, the adhesive domain of MID and the fibronectin- and C3-binding domains of UspA1/A2. Among eight COPD patients in whom a rise in antibody levels could be detected, these functional domains were also the main regions targeted by the antibodies. In addition, human IgG directed against MID was bactericidal and anti-MID antibodies were additive to antibodies targeting UspA1/A2. Hence, the functional domains in these three antigens may have significant potential in a future vaccine against M. catarrhalis.

Short report: antimicrobial susceptibility and genetic characteristics of Haemophilus influenzae isolated from patients with respiratory tract infections between 1987 and 2000, including beta-lactamase-negative ampicillin-resistant strains

The minimum inhibitory concentration (MIC) of five antibiotics and the presence of resistance genes was determined in 163 Haemophilus influenzae isolates collected over 13 years (1987-2000) in four two-yearly sampling periods from patients with respiratory tract infections. The prevalence of beta-lactamase-negative ampicillin-susceptible strains was approximately 80% over the sampling period although fewer strains (65.9%) were recovered in the period 1995-1997. TEM-1 type beta-lactamase-producing strains were less frequent starting at 15.6% and declining to 2.2% in the final sampling period. Low-beta-lactamase-negative ampicillin-resistant (BLNAR) strains were uncommon in 1987-1989 (2.2%), peaked to 19.5% in 1995-1997, but fell back to 11.1% by 2000. Fully BLNAR strains were not detected until the last sampling period (6.7%). The MICs of ampicillin, levofloxacin, cefditoren and ceftriaxone remained stable but there was an eight-fold increase in the MIC of cefdinir over the sampling period. Pulsed-field gel electrophoresis of DNA digests showed that three representative BLNAR strains were genetically distinct and 11 DNA profiles were identified among 17 low-BLNAR strains. These data suggest that the number of genetically altered BLNAR and low-BLNAR strains are increasing in Japan.

Impact of antibiotic restrictions: the physician's perspective

In recent years, there have been worldwide efforts to reduce inappropriate antibiotic prescribing. This has mainly been in response to mounting concerns about the emergence of antimicrobial resistance. Surprisingly, there has been little systematic investigation of the impact of antibiotic restrictions on the complications of infection. It is difficult to address this question using randomised clinical trials in light of the often limited numbers of patients that can be included, who are also often atypical of the broad population of patients receiving antibiotic therapy. Observational data from the UK indicate an association between recent reductions in antibiotic prescribing for lower respiratory tract infection in general practice and an increase in pneumonia mortality. These studies suggest a need for further investigations examining the changing patterns of antibiotic prescribing and their effects on patient outcomes in other countries and in other common infectious diseases. Such studies may provide a useful comparison with the changes observed in lower respiratory tract infection in the UK, and could help to improve antibiotic prescribing practices worldwide. It is also important to study whether associated worse outcomes are limited to certain at-risk groups who should be targeted for care.

An overview of the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program: 1997-2004

This overview provides a summary of the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program over an 8-year period from 1997 to 2004. The evolution of the MYSTIC Program is described, as well as its design compared with other surveillance programs. In addition, the global MYSTIC Program data, published to date, are summarized, and the empiric use of carbapenems, their current indications, and meropenem usage versus resistance was discussed. From 1997 to 2004, 120 medical centers that were actively prescribing meropenem in 32 countries worldwide participated in the program. The MYSTIC Program results demonstrate the sustained potency and continued effectiveness of meropenem globally against clinically relevant Gram-negative and Gram-positive pathogens including extended spectrum beta-lactamase- and AmpC beta-lactamase-producing organisms, which may also display resistance to the fluoroquinolones and/or aminoglycosides. Furthermore, in centers actively prescribing meropenem, resistance to meropenem is not increasing despite greater resistance among the comparator antimicrobial agents. Thus, antipseudomonal carbapenems such as meropenem and imipenem remain an effective treatment option.

Priorities for antibiotic resistance surveillance in Europe

Antibiotic resistance is an increasing global problem. Surveillance studies are needed to monitor resistance development, to guide local empirical therapy, and to implement timely and adequate countermeasures. To achieve this, surveillance studies must have standardised methodologies, be longitudinal, and cover a sufficiently large and representative population. However, many fall short of these requirements that define good surveillance studies. Moreover, current efforts are dispersed among many, mostly small, initiatives with different objectives. These studies must be tailored to the various reservoirs of antibiotic-resistant bacteria, such as hospitalised patients, nursing homes, the community, animals and food. Two studies that could serve as examples of tailored programmes are the European Antimicrobial Resistance Surveillance System (EARSS), which collects resistance data during the diagnosis of hospitalised patients, and the DANMAP programme, which collects data in the veterinary sector. As already noted by the WHO, genetic studies that include both the typing of isolates and the characterisation of resistance determinants are necessary to understand fully the spread and development of antibiotic resistance.

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.

Epidemiological survey on incidence and treatment of community acquired pneumonia in Italy

STUDY OBJECTIVES

To estimate annual incidence of community acquired pneumonia (CAP) in an Italian general population sample.

DESIGN AND PARTICIPANTS

Two hundred and eighty-seven family practitioners (64.6% of those selected) recorded suspected or ascertained CAP cases for 1 year. Information on smoking habit, respiratory symptoms and signs, co-morbidity, antibiotic and corticosteroid therapy, hospitalization, mortality and recovery were obtained.

RESULTS

Six hundred and ninety-nine case forms were collected (53.1% females, mean age 59.6+/-19.5, 20.6% smokers). CAP incidence rates per 1000 population were: 1.69 in men vs. 1.71 in women; 2.33 in the North vs. 1.29 in the Centre-South of Italy; between 0.73 in 14-, and 3.34 in 64+year-old subjects. Main symptoms and signs were cough (73.3%), crackles (72.8%), dullness (57.3%), asthenia (53.4%). 59.5% of subjects had concurrent diseases, mostly cardiac and respiratory. 77.2% of cases had chest X-ray (with parenchymal density in 90.6%). Phlegm microbiological examination was performed in 12.8% of cases. First choice antibiotics were cephalosporins (45.8%), macrolides (20.2%), other beta-lactams (18.6%), and fluoroquinolones (12.2%). Rates of hospitalization and of mortality were 31.8% and 6.0%, respectively.

CONCLUSION

This study confirmed that the annual CAP incidence rate in the general population of South Europe is about 2 per 1000 population and showed a wide choice of antibiotic treatment.

Demographic analysis of antimicrobial resistance among Streptococcus pneumoniae: worldwide results from PROTEKT 1999–2000

DESIGN

The influence of demographic factors upon antimicrobial resistance among 3362 isolates of Streptococcus pneumoniae from 25 countries was investigated, using univariate comparison and multivariate logistic regression.

RESULTS

Eleven countries had significantly higher rates (Odds ratios [OR]: 2.50-64.79) of penicillin and/or erythromycin resistance than the UK. After taking country effects into account, rates of penicillin resistance (OR 1.98) and erythromycin resistance (OR 1.89) were significantly higher among infants than adults. Fewer (OR 0.69) erythromycin-resistant isolates were collected from male than female patients. There was no difference in the incidence of penicillin or erythromycin resistance among inpatients or outpatients. Penicillin resistance was more prevalent among ear swabs than blood cultures (OR 2.07). Erm(B), the predominant macrolide resistance mechanism across all age groups, was particularly prevalent among bronchoalveolar lavage (69.1%) and sinus (68.8%) isolates. Isolates possessing both erm(B) and mef(A) were generally collected from South Korea and were most common among infants and children (10.3%) and ear samples (17.3%). Telithromycin susceptibility was >99.5%, irrespective of demography.

CONCLUSIONS

Although demography had a significant impact on antimicrobial resistance of pneumococci, telithromycin remained highly active across all demographic groups.

Evolving Concepts of Pharmaceutical Company–Sponsored Surveillance Studies

As a result of increasing bacterial resistance to antimicrobial agents, there is a need to conduct studies that monitor changes in susceptibility. In addition to studying the emergence and dissemination of antibacterial resistance, pharmaceutical companies perform surveillance studies for a number of reasons. As an example, the Alexander Project was conducted to study community-acquired respiratory infections internationally over 10 years. The project's findings have been valuable in the study of antimicrobial resistance. The Alexander Project has also been instrumental in the study of the evolution of resistance genes and in predictions of future rates of resistance, as well as in establishing the importance of high-quality data, the complexity of the evolution of resistance, and the need to disseminate the results in a variety of formats. Although there has been a reduction in pharmaceutical company studies, consolidated efforts between industry, government, and private groups have increased. Future surveillance efforts by pharmaceutical companies will likely be more targeted and disease directed.

Increasing prevalence of multidrug-resistant Streptococcus pneumoniae in the United States over a 10-year period: Alexander Project

The Alexander Project is a global surveillance study conducted from 1992 to 2001. Minimum inhibitory concentrations and percent resistance to a panel of antimicrobial agents were determined according to National Committee for Clinical Laboratory Standards methodology. Resistance to penicillin (PEN-R) and erythromycin (ERY-R) have increased in the period 1992-2001 by 3.9 and 4.5 times to 20.7% and 27.9%, respectively. Joint PEN-ERY-R has increased 4.9 times, up to 15.3%. In 1992, 57.1% of all PEN-R isolates were also ERY-R, whereas in 2001, 75.8% were ERY-R. Resistance to only 1 antibiotic increased slightly, from 8% in 1992 to 12% in 2001, whereas resistance to more than 1 antibiotic increased 4.3 times, from 6.4% in 1992 to 27.8% of all strains in 2001. Multidrug-resistant pneumococci are an increasingly common finding in the United States. Three of four PEN-R isolates are also multiresistant. The rate of growth of multidrug resistance is higher than that of single antibiotic resistance.

Antibiotic prescribing patterns for sore throat infections in a university-based primary care clinic

BACKGROUND

Recent studies reveal that a high percentage (over 50%) of episodes for upper respiratory tract infections (URTIs) are treated with antibiotics, regardless of appropriateness or the necessity for prescription. We identified antibiotic prescriptions in a primary health care centre (PHC) and evaluated their suitability for sore throat infections. We also explored whether symptoms, signs, diagnosis and antibiotics prescribed differed by gender.

PATIENTS AND METHODS

We collected data on all patients visiting the centre over a period of 12 weeks with a main complaint of sore throat who were prescribed antibiotics after taking a blood count and throat culture. Patients older than 16 years of age were included in the study irrespective of sex, nationality, marital status, occupation or location of residence. The chi square (chi2) statistical test was used in comparing categorical variables. A P value of < 0.05 was considered significant.

RESULTS

During the period of study, 579 patients with URTIs presented to the health centre, from which 339 patients with a sore throat were enrolled. Of the study group, 48.7% (165) were male and 51.3% (174) female, with the majority of patients being under 30 years old (54.3%). Throat cultures were positive in 56 patients (16.5%). Most of patients were diagnosed as having pharyngitis (22.7%), and the most frequently prescribed medicine was an oral penicillin (39.1%). Two hundred eight-six patients (84.4%) had 2 or fewer Centor criteria.

CONCLUSIONS

Throat cultures were positive in only 16.5% of the patients prescribed antibiotics. This indicates that physicians in the health centre of the university are prescribing antibiotics inappropriately and inconsistently. This also highlights the need for more prescriber education, especially as the range of medications available to the general practitioner for prescribing increases.

Rhinosinusitis: establishing definitions for clinical research and patient care

Background

There is a need for more research on all forms of rhinosinusitis. Progress in this area has been hampered by a lack of consensus definitions and the limited number of published clinical trials.

Objectives

To develop consensus definitions for rhinosinusitis and outline strategies useful in clinical trials.

Methods

Five national societies, The American Academy of Allergy, Asthma and Immunology; The American Academy of Otolaryngic Allergy; The American Academy of Otolaryngology Head and Neck Surgery; The American College of Allergy, Asthma and Immunology; and the American Rhinologic Society formed an expert panel from multiple disciplines. Over two days, the panel developed definitions for rhinosinusitis and outlined strategies for design of clinical trials.

Results

Committee members agreed to adopt the term “rhinosinusitis” and reached consensus on definitions and strategies for clinical research on acute presumed bacterial rhinosinusitis, chronic rhinosinusitis without polyposis, chronic rhinosinusitis with polyposis, and classic allergic fungal rhinosinusitis. Symptom and objective criteria, measures for monitoring research progress, and use of symptom scoring tools, quality-of-life instruments, radiologic studies, and rhinoscopic assessment were outlined for each condition.

Conclusion

The recommendations from this conference should improve accuracy of clinical diagnosis and serve as a starting point for design of rhinosinusitis clinical trials.

Rhinosinusitis: Establishing definitions for clinical research and patient care

Background

There is a need for more research on all forms of rhinosinusitis. Progress in this area has been hampered by a lack of consensus definitions and the limited number of published clinical trials.

Objectives

To develop consensus definitions for rhinosinusitis and outline strategies useful in clinical trials.

Study design

Five national societies, The American Academy of Allergy, Asthma and Immunology; The American Academy of Otolaryngic Allergy; The American Academy of Otolaryngology Head and Neck Surgery; The American College of Allergy, Asthma and Immunology; and the American Rhinologic Society formed an expert panel from multiple disciplines. Over two days, the panel developed definitions for rhinosinusitis and outlined strategies for design of clinical trials.

Results

Committee members agreed to adopt the term “rhinosinusitis” and reached consensus on definitions and strategies for clinical research on acute presumed bacterial rhinosinusitis, chronic rhinosinusitis without polyposis, chronic rhinosinusitis with polyposis, and classic allergic fungal rhinosinusitis. Symptom and objective criteria, measures for monitoring research progress, and use of symptom scoring tools, quality-of-life instruments, radiologic studies, and rhinoscopic assessment were outlined for each condition.

Conclusions

The recommendations from this conference should improve accuracy of clinical diagnosis and serve as a starting point for design of rhinosinusitis clinical trials.

A randomized, double-blind study comparing 5 days oral gemifloxacin with 7 days oral levofloxacin in patients with acute exacerbation of chronic bronchitis

OBJECTIVE

To demonstrate that 5 days of treatment with a new fluoroquinolone, gemifloxacin, is at least as effective as 7 days of treatment with levofloxacin in adult patients with acute exacerbation of chronic bronchitis (AECB).

DESIGN

Randomized, double-blind, double dummy, multicentre, parallel group study

SETTING

Sixty different medical centers in US, UK and Germany.

MATERIAL AND METHODS

A total of 360 adults (>40 years of age) with AECB were randomly assigned to receive gemifloxacin 320 mg once daily for 5 days or levofloxacin 500mg once daily for 7 days. The primary efficacy parameter was a clinical response at follow-up (Days 14-21).

RESULTS

In total, 335/360 patients completed the study (93.1%). Seven patients receiving gemifloxacin withdrew from the study compared to 18 patients receiving levofloxacin; this difference was statistically significant (Fisher's exact test: p=0.02). In the intent-to-treat (ITT) population, the clinical success rate at follow-up (Days 14-21) was 85.2% (155/182) with gemifloxacin and 78.1% (139/178) with levofloxacin. Clinical success rate in the per-protocol (PP) population was 88.2% (134/152) with gemifloxacin and 85.1% (126/148) with levofloxacin. At long-term follow-up (Days 28-35), the clinical success rates in the PP population were 83.7% (123/147) with gemifloxacin and 78.4% (109/139) with levofloxacin. The difference in success rates was 5.26% (95% CI: -3.83, 14.34).

CONCLUSION

The clinical efficacy of gemifloxacin 320 mg once daily for 5 days in AECB was at least as good as levofloxacin 500 mg once daily for 7 days. Fewer withdrawals and superior clinical efficacy at long-term follow-up were also seen with gemifloxacin.

Global distribution of Streptococcus pneumoniae serotypes isolated from paediatric patients during 1999–2000 and the in vitro efficacy of telithromycin and comparators

Few data exist on the distribution of Streptococcus pneumoniae serotypes in many countries and in non-invasive disease overall. Here, data are presented from 772 paediatric isolates from children with community-acquired respiratory tract infections isolated from the PROTEKT global surveillance study during 1999–2000. Overall, 60.0 % of isolates were covered by the 7-valent pneumococcal vaccine formulation (PCV7), with greater coverage in the USA compared with Europe (69.6 vs 55.5 %, P = 0.014). Geographically dispersed clones of serogroups 3, 11 and 15 accounted for most of the isolates outside PCV7 coverage. Overall, macrolide, penicillin and cotrimoxazole non-susceptibility rates were high; however, all isolates were susceptible to telithromycin. Although only 7.4 % of isolates were resistant to amoxycillin/clavulanate, a higher prevalence of resistance was found in isolates from the USA and South Korea. This study shows the feasibility and importance of serotyping antibiotic surveillance study isolates and the potential of telithromycin as an important option for empiric therapy.

Limited spread of penicillin-nonsusceptible pneumococci, Skåne County, Sweden

In response to increasing frequencies of penicillin-nonsusceptible pneumococci (PNSP), for which the MIC of penicillin was >0.12 mg/L, in Skåne County, southern Sweden, national recommendations were initiated in 1995 to limit the spread of pneumococci with high MICs (> or =0.5 mg/L) of penicillin (PRP), especially among children of preschool age. Traditional communicable disease control measures were combined with actions against inappropriate antimicrobial drug use. During the first 6 years that these recommendations were applied in Skåne County, the average frequency of penicillin-resistant pneumococci has been stable at =2.6%, as has the average PNSP frequency (7.4%). However, PNSP have been unevenly distributed in the county, with the highest frequencies in the southwest. Simultaneously, the rate of antimicrobial drug use for children <6 years of age was reduced by 20%. Thus the spread of PNSP between and within the municipalities in the county has been limited.

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.

Antimicrobial susceptibility patterns of Streptococcus pneumoniae in Mexico

The susceptibility to 14 beta-lactam and non-beta-lactam antimicrobial agents was evaluated for Streptococcus pneumoniae from patients with community-acquired respiratory infections in a Mexican medical center. Three hundred fifteen pneumococcal isolates obtained from patients between 1995 and 2001 were tested by the broth microdilution test. Fifty-two percent of the isolates were nonsusceptible to penicillin (minimal inhibitory concentration, >0.06 microg/mL). Penicillin-nonsusceptible isolates were more likely to exhibit resistance to cephalosporins, macrolides, ciprofloxacin, trimethoprim/sulfamethoxazole, chloramphenicol, and tetracycline when compared to penicillin-susceptible isolates. Ninety-three percent of the penicillin-nonsusceptible isolates were resistant to at least one other class of antimicrobials, in contrast to only 47% of the penicillin-susceptible strains (p < 0.0001). More than 90% of the tested isolates were susceptible to amoxicillin/clavulanate, ceftriaxone, levofloxacin, and gatifloxacin. Reduced susceptibility to penicillin was considered to be a reliable marker for the higher probability of multidrug resistance, thus requiring in vitro tests to guide chemotherapy or the choices of parenteral extended spectrum cephalosporins or newer respiratory quinolones.

Molecular epidemiology of multiresistant Streptococcus pneumoniae with both erm(B)- and mef(A)-mediated macrolide resistance

Of a total of 1043 macrolide-resistant Streptococcus pneumoniae isolates collected from 24 countries as part of PROTEKT 1999-2000, 71 isolates tested positive for both the mef(A) and erm(B) genes. Of 69 isolates subjected to further molecular investigations, all were resistant to tetracycline, 63 (91.3%) were resistant to penicillin, and 57 (82.6%) were resistant to trimethoprim-sulfamethoxazole. One isolate was also fluoroquinolone resistant, and another was resistant to quinupristin-dalfopristin. The ketolide telithromycin retained activity against all of the isolates. Of the 69 of these 71 isolates viable for further testing, 46 were from South Korea, 13 were from the United States, 8 came from Japan, and 1 each came from Mexico and Hungary. One major clonal complex (59 [85.5%] of 69 isolates) was identified by serotyping (with 85.5% of the isolates being 19A or 19F), pulsed-field gel electrophoresis, and multilocus sequence typing. The remaining isolates were less clonal in nature. Representative isolates were shown to carry the mobile genetic elements Tn1545 and mega, were negative for Tn1207.1, had tetracycline resistance mediated by tet(M), and contained the mef(E) variant of mef(A). All isolates were positive for mel, a homologue of the msr(A) efflux gene. These clones are obviously very efficient at global dissemination, and hence it will be very important to monitor their progress through continued surveillance. Telithromycin demonstrated high levels of activity (MIC for 90% of the strains tested, 0.5 micro g/ml; MIC range, 0.06 to 1 micro g/ml) against all isolates.

Antimicrobial treatment guidelines for acute bacterial rhinosinusitis

Treatment guidelines developed by the Sinus and Allergy Health Partnership for acute bacterial rhinosinusitis (ABRS) were originally published in 2000. These guidelines were designed to: (1) educate clinicians and patients (or patients’ families) about the differences between viral and bacterial rhinosinusitis; (2) reduce the use of antibiotics for nonbacterial nasal/sinus disease; (3) provide recommendations for the diagnosis and optimal treatment of ABRS; (4) promote the use of appropriate antibiotic therapy when bacterial infection is likely; and (5) describe the current understanding of pharmacokinetic and pharmacodynamics and how they relate to the effectiveness of antimicrobial therapy. The original guidelines are updated here to include the most recent information on management principles, antimicrobial susceptibility patterns, and therapeutic options.

Burden of disease

An estimated 20 million cases of ABRS occur annually in the United States. According to National Ambulatory Medical Care Survey (NAMCS) data, sinusitis is the fifth most common diagnosis for which an antibiotic is prescribed. Sinusitis accounted for 9% and 21% of all pediatric and adult antibiotic prescriptions, respectively, written in 2002. The primary diagnosis of sinusitis results in expenditures of approximately $3.5 billion per year in the United States.

Definition and diagnosis of ABRS

ABRS is most often preceded by a viral upper respiratory tract infection (URI). Allergy, trauma, dental infection, or other factors that lead to inflammation of the nose and paranasal sinuses may also predispose individuals to developing ABRS.

Patients with a “common cold” (viral URI) usually report some combination of the following symptoms: sneezing, rhinorrhea, nasal congestion, hyposmia/anosmia, facial pressure, postnasal drip, sore throat, cough, ear fullness, fever, and myalgia. A change in the color or the characteristic of the nasal discharge is not a specific sign of a bacterial infection. Bacterial superinfection may occur at any time during the course of a viral URI. The risk that bacterial superinfection has occurred is greater if the illness is still present after 10 days. Because there may be cases that fall out of the “norm” of this typical progression, practicing clinicians need to rely on their clinical judgment when using these guidelines. In general, however, a diagnosis of ABRS may be made in adults or children with symptoms of a viral URI that have not improved after 10 days or worsen after 5 to 7 days. There may be some or all of the following signs and symptoms: nasal drainage, nasal congestion, facial pressure/pain (especially when unilateral and focused in the region of a particular sinus), postnasal drainage, hyposmia/anosmia, fever, cough, fatigue, maxillary dental pain, and ear pressure/fullness.

Physical examination provides limited information in the diagnosis of ABRS.

While sometimes helpful, plain film radiographs, computed tomography (CT), and magnetic resonance imaging scans are not necessary for cases of ABRS.

Microbiology of ABRS

The most common bacterial species isolated from the maxillary sinuses of patients with ABRS are Streptococcus pneumoniae , Haemophilus influenzae , and Moraxella catarrhalis , the latter being more common in children. Other streptococcal species, anaerobic bacteria and Staphylococcus aureus cause a small percentage of cases.

Bacterial resistance in ABRS

The increasing prevalence of penicillin nonsusceptibility and resistance to other drug classes among S pneumoniae has been a problem in the United States, with 15% being penicillin-intermediate and 25% being penicillin-resistant in recent studies. Resistance to macrolides and trimethoprim/sulfamethoxazole (TMP/SMX) is also common in S pneumoniae . The prevalence of β-lactamase-producing isolates of H influenzae is approximately 30%, while essentially all M catarrhalis isolates produce β-lactamases. Resistance of H influenzae to TMP/SMX is also common.

Antimicrobial treatment guidelines for ABRS

These guidelines apply to both adults and children. When selecting antibiotic therapy for ABRS, the clinician should consider the severity of the disease, the rate of progression of the disease, and recent antibiotic exposure. The guidelines now divide patients with ABRS into two general categories: (1) those with mild symptoms who have not received antibiotics within the past 4 to 6 weeks, and (2) those with mild disease who have received antibiotics within the past 4 to 6 weeks or those with moderate disease regardless of recent antibiotic exposure. The difference in severity of disease does not imply infection with a resistant pathogen. Rather, this terminology indicates the relative degree of acceptance of possible treatment failure and the likelihood of spontaneous resolution of symptoms—patients with more severe symptoms are less likely to resolve their disease spontaneously. The primary goal of antibiotic therapy is to eradicate bacteria from the site of infection, which, in turn, helps (1) return the sinuses back to health; (2) decrease the duration of symptoms to allow patients to resume daily activities more quickly; (3) prevent severe complications such as meningitis and brain abscess; and (4) decrease the development of chronic disease. Severe or life-threatening infections with or without complications are rare, and are not addressed in these guidelines.

Prior antibiotic use is a major risk factor associated with the development of infection with antimicrobial-resistant strains. Because recent antimicrobial exposure increases the risk of carriage of and infection due to resistant organisms, antimicrobial therapy should be based upon the patient’s history of recent antibiotic use. The panel’s guidelines, therefore, stratify patients according to antibiotic exposure in the previous 4 to 6 weeks.

Lack of response to therapy at ≥72 hours is an arbitrary time established to define treatment failures. Clinicians should monitor the response to antibiotic therapy, which may include instructing the patient to call the office or clinic if symptoms persist or worsen over the next few days.

The predicted bacteriologic and clinical efficacy of antibiotics in adults and children has been determined according to mathematical modeling of ABRS developed by Michael Poole, MD, PhD, based on pathogen distribution, resolution rates without treatment, and in vitro microbiologic activity.

Antibiotics can be placed into the following relative rank order of predicted clinical efficacy for adults: 90% to 92% = respiratory fluoroquinolones (gatifloxacin, levofloxacin, moxifloxacin), ceftriaxone, high-dose amoxicillin/clavulanate (4 g/250 mg/day), and amoxicillin/clavulanate (1.75 g/250 mg/day); 83% to 88% = high-dose amoxicillin (4 g/day), amoxicillin (1.5 g/day), cefpodoxime proxetil, cefixime (based on H influenzae and M catarrhalis coverage), cefuroxime axetil, cefdinir, and TMP/SMX; 77% to 81% = doxycycline, clindamycin (based on gram-positive coverage only), azithromycin, clarithromycin and erythromycin, and telithromycin; 65% to 66% = cefaclor and loracarbef. The predicted spontaneous resolution rate in patients with a clinical diagnosis of ABRS is 62%.

Antibiotics can be placed into the following relative rank order of predicted clinical efficacy in children with ABRS: 91% to 92% = ceftriaxone, high-dose amoxicillin/clavulanate (90 mg/6.4 mg per kg per day) and amoxicillin/clavulanate (45 mg/6.4 mg per kg per day); 82% to 87% = high-dose amoxicillin (90 mg/kg per day), amoxicillin (45 mg/kg per day), cefpodoxime proxetil, cefixime (based on H influenzae and M catarrhalis coverage only), cefuroxime axetil, cefdinir, and TMP/SMX; and 78% to 80% = clindamycin (based on gram-positive coverage only), cefprozil, azithromycin, clarithromycin, and erythromycin; 67% to 68% = cefaclor and loracarbef. The predicted spontaneous resolution rate in untreated children with a presumed diagnosis of ABRS is 63%.

Recommendations for initial therapy for adult patients with mild disease (who have not received antibiotics in the previous 4 to 6 weeks) include the following choices: amoxicillin/clavulanate (1.75 to 4 g/250 mg per day), amoxicillin (1.5 to 4 g/day), cefpodoxime proxetil, cefuroxime axetil, or cefdinir. While TMP/SMX, doxycycline, azithromycin, clarithromycin, erythromycin, or telithromycin may be considered for patients with β-lactam allergies, bacteriologic failure rates of 20% to 25% are possible. Failure to respond to antimicrobial therapy after 72 hours should prompt either a switch to alternate antimicrobial therapy or reevaluation of the patient (see Table 4).When a change in antibiotic therapy is made, the clinician should consider the limitations in coverage of the initial agent.

Recommendations for initial therapy for adults with mild disease who have received antibiotics in the previous 4 to 6 weeks or adults with moderate disease include the following choices: respiratory fluoroquinolone (eg, gatifloxacin, levofloxacin, moxifloxacin) or high-dose amoxicillin/clavulanate (4 g/250 mg per day). The widespread use of respiratory fluoroquinolones for patients with milder disease may promote resistance of a wide spectrum of organisms to this class of agents. Ceftriaxone (parenteral, 1 to 2 g/day for 5 days) or combination therapy with adequate gram-positive and negative coverage may also be considered. Examples of appropriate regimens of combination therapy include high-dose amoxicillin or clindamycin plus cefixime, or high-dose amoxicillin or clindamycin plus rifampin. While the clinical effectiveness of ceftriaxone and these combinations for ABRS is unproven; the panel considers these reasonable therapeutic options based on the spectrum of activity of these agents and on data extrapolated from acute otitis media studies. Rifampin should not be used as monotherapy, casually, or for longer than 10 to 14 days, as resistance quickly develops to this agent. Rifampin is also a well-known inducer of several cytochrome p450 isoenzymes and therefore has a high potential for drug interactions. Failure of a patient to respond to antimicrobial therapy after 72 hours of therapy should prompt either a switch to alternate antimicrobial therapy or reevaluation of the patient (see Table 4). When a change in antibiotic therapy is made, the clinician should consider the limitations in coverage of the initial agent. Patients who have received effective antibiotic therapy and continue to be symptomatic may need further evaluation. A CT scan, fiberoptic endoscopy or sinus aspiration and culture may be necessary.

Recommendations for initial therapy for children with mild disease and who have not received antibiotics in the previous 4 to 6 weeks include the following: high-dose amoxicillin/clavulanate (90 mg/6.4 mg per kg per day), amoxicillin (90 mg/kg per day), cefpodoxime proxetil, cefuroxime axetil, or cefdinir. TMP/SMX, azithromycin, clarithromycin, or erythromycin is recommended if the patient has a history of immediate Type I hypersensitivity reaction to β-lactams. These antibiotics have limited effectiveness against the major pathogens of ABRS and bacterial failure of 20% to 25% is possible. The clinician should differentiate an immediate hypersensitivity reaction from other less dangerous side effects. Children with immediate hypersensitivity reactions to β-lactams may need: desensitization, sinus cultures, or other ancillary procedures and studies. Children with other types of reactions and side effects may tolerate one specific β-lactam, but not another. Failure to respond to antimicrobial therapy after 72 hours should prompt either a switch to alternate antimicrobial therapy or reevaluation of the patient (see Table 5).When a change in antibiotic therapy is made, the clinician should consider the limitations in coverage of the initial agent.

The recommended initial therapy for children with mild disease who have received antibiotics in the previous 4 to 6 weeks or children with moderate disease is high-dose amoxicillin/clavulanate (90 mg/6.4 mg per kg per day). Cefpodoxime proxetil, cefuroxime axetil, or cefdinir may be used if there is a penicillin allergy (eg, penicillin rash); in such instances, cefdinir is preferred because of high patient acceptance. TMP/SMX, azithromycin, clarithromycin, or erythromycin is recommended if the patient is β-lactam allergic, but these do not provide optimal coverage. Clindamycin is appropriate if S pneumoniae is identified as a pathogen. Ceftriaxone (parenteral, 50 mg/kg per day for 5 days) or combination therapy with adequate gram-positive and -negative coverage may also be considered. Examples of appropriate regimens of combination therapy include high-dose amoxicillin or clindamycin plus cefixime, or high-dose amoxicillin or clindamycin plus rifampin. The clinical effectiveness of ceftriaxone and these combinations for ABRS is unproven; the panel considers these reasonable therapeutic options based on spectrum of activity and on data extrapolated from acute otitis media studies. Rifampin should not be used as monotherapy, casually, or for longer than 10 to 14 days as resistance quickly develops to this agent. Failure to respond to antimicrobial therapy after 72 hours of therapy should prompt either a switch to alternate antimicrobial therapy or reevaluation of the patient (see Table 5). When a change in antibiotic therapy is made, the clinician should consider the limitations in coverage of the initial agent. Patients who have received effective antibiotic therapy and continue to be symptomatic may need further evaluation. A CT scan, fiberoptic endoscopy or sinus aspiration and culture may be necessary.

Antimicrobial Resistance among Isolates of Respiratory Tract Infection Pathogens from the Southern United States: Data from the PROTEKT US Surveillance Program 2000/2001

BACKGROUND

PROTEKT US (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin in the United States) was established in 2000 to monitor antimicrobial resistance among respiratory tract pathogens across the United States.

METHODS

During 2000 to 2001, 75 southern US centers collected 3,867 Streptococcus pneumoniae, 1,455 Streptococccus pyogenes and 1,042 Haemophilus influenzae.

RESULTS

Overall, 46.1% of S. pneumoniae isolates were nonsusceptible to penicillin, 35.8% were resistant to erythromycin, and 0.5% were resistant to fluoroquinolones. Against S. pneumoniae the most active agents were telithromycin (99.7% susceptible), linezolid (99.8%) and the fluoroquinolones (levofloxacin 99.4%, gatifloxacin 99.5%). The prevalence of erythromycin-resistant S. pyogenes isolates was 4.5%. Telithromycin, at concentration of < or = 1 mg/L, inhibited 99.9% of S. pyogenes. The prevalence of beta-lactamase positive H. influenzae was 26.2%. Telithromycin was active (MIC90 4 mg/L) against H. influenzae, irrespective of beta-lactamase production.

CONCLUSION

The prevalence of penicillin and macrolide resistance among respiratory tract pathogens from the southern United States is high. Fluoroquinolone resistance is low. Telithromycin is highly active against respiratory tract pathogens with reduced susceptibility to beta-lactams, macrolides, and fluoroquinolones.

Comparative in vitro activity of telithromycin and beta-lactam antimicrobials against bacterial pathogens from community-acquired respiratory tract infections: data from the first year of PROTEKT (1999-2000)

The in vitro activity of telithromycin, a new ketolide, was compared with beta-lactam antimicrobials against pathogens commonly associated with community-acquired respiratory tract infections. These pathogens were collected during 1999-2000 as part of the ongoing PROTEKT surveillance study. Globally, penicillin nonsusceptibility among Streptococcus pneumoniae (n = 3362) was 36.3%, ranging from 21.5% (Australasia) to 68.0% (Far East). Telithromycin showed higher potency (MIC90 0.12 mg/L) than beta-lactams against S. pneumoniae; 99.9% of all and 99.6% of multi-resistant isolates were susceptible to telithromycin. Among Streptococcus pyogenes isolates (n = 1485), 100% were susceptible to beta-lactams, and the telithromycin MIC50 and MIC90 were both 0.015 mg/L. Among Haemophilus influenzae (n = 2948), 16.6% produced beta-lactamase, which reduced the activity of ampicillin, cefaclor and cefprozil. 99.9% of H. influenzae were susceptible to telithromycin and the MIC range for M. catarrhalis was 0.004-0.5 mg/L. The first year results of PROTEKT confirmed high potency for telithromycin against common respiratory tract pathogens, including beta-lactam-resistant strains.

In vitro susceptibility of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis: a European multicenter study during 2000-2001

OBJECTIVE

To assess the current (2001) activity of respiratory fluoroquinolones and comparator agents against respiratory pathogens isolated in European countries.

METHODS

During 2000-2001, we prospectively collected 1995 isolates of Haemophilus influenzae, 1870 isolates of Streptococcus pneumoniae and 649 isolates of Moraxella catarrhalis from hospital laboratories in France, Germany, Greece, Italy, Spain and the UK. National Committee for Clinical Laboratory Standards (NCCLS)-approved broth microdilution antimicrobial susceptibility testing methods and interpretive criteria were used throughout.

RESULTS

Of the S. pneumoniae isolates, 99.6% were susceptible to moxifloxacin, gatifloxacin and levofloxacin; the corresponding figure for H. influenzae was 100%. All M. catarrhalis isolates had moxifloxacin MICs </= 0.12 mg/L. For all three pathogens, fluoroquinolone susceptibility remained unchanged from the previous 1997-98 study. The incidence of penicillin non-susceptibility in the S. pneumoniae isolates tested remained similar to or higher than that recorded in previous studies: France, 165/291 (56.7%); Germany, 46/506 (9.1%); Greece, 20/55 (36.4%); Italy, 45/364 (12.4%); Spain, 146/268 (54.5%); and the UK, 26/386 (6.7%). Significant levels of resistance to oral compounds (cefuroxime, cefaclor, cefdinir, clarithromycin, azithromycin, tetracycline, and trimethoprim-sulfamethoxazole) were detected among S. pneumoniae isolates. beta-Lactamase production among H. influenzae isolates ranged from 6.2% to 33.1% per country, and ampicillin, clarithromycin or trimethoprim-sulfamethoxazole resistance were the most common phenotypes detected. beta-Lactamase production among M. catarrhalis isolates ranged from 94.1% to 100% per country.

CONCLUSIONS

With the exception of a few localized reports, resistance to moxifloxacin and other new fluoroquinolones in common respiratory pathogens is a rare occurrence, despite significant resistance to other compound classes. Surveillance will play a key role in tracking changes in fluoroquinolone susceptibility in European countries.

Guidelines for the management of community-acquired pneumonia in Saudi Arabia: a model for the Middle East region

Worldwide, community-acquired pneumonia (CAP) is a common respiratory tract infection and is now a growing public health concern in Saudi Arabia. In an effort to simplify treatment regimens to aid the practitioner, empirical treatment guidelines for CAP have evolved across the international medical community, reducing the number of antibiotics used and improving outcomes. Saudi Arabia and the surrounding region have no such consensus guidelines and this document aims to redress this lack. The potential impacts of developing and implementing CAP treatment guidelines in Saudi Arabia, which are new to the Kingdom, will be examined. Widespread adoption of these SACAP guidelines could lead to nationwide reductions of antibiotic resistance and improvement of clinical outcomes. Ultimately, Kingdomwide uniformity of treatment algorithms provides a foundation for both database generation and valuable outcomes of research in the future.

Variable sensitivity to bacterial methionyl-tRNA synthetase inhibitors reveals subpopulations of Streptococcus pneumoniae with two distinct methionyl-tRNA synthetase genes

As reported previously (J. R. Jarvest et al., J. Med. Chem. 45:1952-1962, 2002), potent inhibitors (at nanomolar concentrations) of Staphylococcus aureus methionyl-tRNA synthetase (MetS; encoded by metS1) have been derived from a high-throughput screening assay hit. Optimized compounds showed excellent activities against staphylococcal and enterococcal pathogens. We report on the bimodal susceptibilities of S. pneumoniae strains, a significant fraction of which was found to be resistant (MIC, > or =8 mg/liter) to these inhibitors. Using molecular genetic techniques, we have found that the mechanism of resistance is the presence of a second, distantly related MetS enzyme, MetS2, encoded by metS2. We present evidence that the metS2 gene is necessary and sufficient for resistance to MetS inhibitors. PCR analysis for the presence of metS2 among a large sample (n = 315) of S. pneumoniae isolates revealed that it is widespread geographically and chronologically, occurring at a frequency of about 46%. All isolates tested also contained the metS1 gene. Searches of public sequence databases revealed that S. pneumoniae MetS2 was most similar to MetS in Bacillus anthracis, followed by MetS in various non-gram-positive bacterial, archaeal, and eukaryotic species, with streptococcal MetS being considerably less similar. We propose that the presence of metS2 in specific strains of S. pneumoniae is the result of horizontal gene transfer which has been driven by selection for resistance to some unknown class of naturally occurring antibiotics with similarities to recently reported synthetic MetS inhibitors.

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.

Antibacterial resistance in Streptococcus pneumoniae and Haemophilus influenzae from Italy and Spain: data from the PROTEKT surveillance study, 1999-2000

Antibacterial resistance was evaluated among Streptococcus pneumoniae (n=252) and Haemophilus influenzae (n=202) from two centres in Spain (Barcelona and Madrid) and two centres in Italy (Genoa and Catania) collected during 1999-2000 as part of the ongoing PROTEKT (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin) international surveillance program. Pneumococcal nonsusceptibility to penicillin G was found to be considerably higher in Spain (53.4%) than in Italy (15.1%), whereas erythromycin A resistance was higher in Italy (42.9%) than in Spain (28.6%). Among macrolide-resistant isolates investigated for resistance genes, the prevalence of mefA was higher among isolates from Italy (20/51, 39.2%) than among Spanish isolates (2/38, 5.3%). All other macrolide-resistant isolates possessed ermB. Telithromycin possessed good anti-pneumococcal activity against isolates from both countries (MIC90 0.03 mg/L [Spain]; 0.25 mg/L [Italy]), irrespective of resistance to other antibacterials. Beta-lactamase production among H. influenzae was low: Spain, 10.9%; Italy, 1.8%. With the exception of ampicillin and co-trimoxazole, all H. influenzae isolates were highly susceptible to the antibacterials tested, and all were inhibited by telithromycin at a concentration of < or = 2 mg/L. The findings of PROTEKT 1999-2000 highlight the importance of local resistance patterns in guiding the choice of empirical antibacterials for community-acquired respiratory tract infections.

Antimicrobial susceptibility of 840 clinical isolates of Haemophilus influenzae collected in four European countries in 2000-2001

In 2000-2001, 840 clinical isolates of Haemophilus influenzae were collected from laboratories in France, Germany, Italy and Spain (210 isolates/country). Beta-Lactamase production among the isolates varied considerably by country, ranging from 8.1% in Germany to 34.8% in France. H. influenzae from patients <or=4 years old showed the highest prevalence of beta-lactamase production (23.2%), compared with isolates from patients aged 5-17 years (17.8%) and >or=18 years (16.5%). All isolates were susceptible to amoxicillin-clavulanate, ciprofloxacin and levofloxacin; 99.6% and 98.9% of isolates were susceptible to azithromycin and cefuroxime, respectively. Among the macrolides tested, azithromycin (MIC90, 2 mg/L) was eight-fold more potent than clarithromycin (MIC90, 16 mg/L) and roxithromycin (MIC90, 16 mg/L). Despite variations in beta-lactamase production between different countries, > 99% of all isolates were susceptible to amoxicillin-clavulanate, ciprofloxacin, levofloxacin, and azithromycin.

In vitro antibacterial activity and pharmacodynamics of new quinolones

This synopsis of published literature summarises data on the in vitro antibacterial activity and pharmacodynamics of fluoroquinolones. Data were compiled for ciprofloxacin, levofloxcin, moxifloxacin, gatifloxacin, grepafloxacin, gemifloxacin, trovafloxacin, sitafloxacin and garenoxacin. All of these quinolones are almost equipotent against gram-negative bacteria but demonstrate improved activity against gram-positive species. The new quinolones are uniformly active against gram-positive species except Streptococcus pneumoniae; against which gemifloxacin, sitafloxacin and garenoxacin are one to two dilution steps more active than moxifloxacin. All of the new quinolones except gemifloxacin demonstrate enhanced activity against anaerobes. Since all the new quinolones show similar activity against the major respiratory tract pathogens except Streptococcus pneumoniae and members of the family Enterobacteriaceae, their pharmacokinetics and pharmacodynamics will be clinically relevant differentiators and determinants of their overall activity and efficacy. In vitro simulations of serum concentrations revealed that (i). gemifloxacin and levofloxacin were significantly and gatifloxacin moderately less active than moxifloxacin against Streptococcus pneumoniae and Staphylococcus aureus, and (ii). resistant subpopulations emerged following exposure to levofloxacin and gatifloxacin (gemifloxacin not yet published) but not to moxifloxacin. The emergence of resistance is a function of drug concentrations achievable in vivo and the susceptibility pattern of the target organisms. Therefore, the use of less potent fluoroquinolones with borderline or even suboptimal pharmacokinetic/pharmacodynamic surrogate parameters will inadvertently foster the development of class resistance. Drugs with the most favourable pharmacokinetic/pharmacodynamic characteristics should be used as first-line agents in order to preserve the potential of this drug class and, most importantly, to provide the patient with an optimally effective regimen.