Antibacterial resistance among children with community-acquired respiratory tract infections (PROTEKT 1999-2000)

Use of antibiotics for common illnesses among children aged under 5 years in a rural community in Indonesia: a cross-sectional study

Background

The incidence of antimicrobial resistance has been increasing worldwide in the past decades, which includes resistance to bacteria that cause common childhood illnesses, such as acute respiratory infections and diarrhea. Numerous children with those common illnesses are treated with antibiotics. However, in such cases, antibiotic treatment is not required. Community-based studies focusing on antibiotic use among children are still limited. This study aimed to identify the prevalence of antibiotic use for common childhood illnesses and to investigate factors associated with antibiotic use in children under 5 years old as well as female caregivers in a rural community in Indonesia.

Methods

A cross-sectional study of 334 children in three villages of Banten Province, located in the western part of Java Island, was conducted in May 2018. Female caregivers who were responsible for providing medications to children were interviewed. We obtained information such as demographic data, any common clinical illness within the last 30 days, and antibiotic usage during an episode of illness. We excluded children with underlying disease that require a regular follow-up and children who were hospitalized in the last 30 days in the analysis. Antibiotic use answered by female caregivers was verified by checking its package or showing photos of various antibiotics to the female caregivers. Crushed antibiotics were confirmed with health professionals.

Results

A total of 203 children had clinical symptoms, and the most common symptom was fever and respiratory symptoms. In total, 49.3% received antibiotics, and 66% of them were prescribed by private health professionals. Only two children received antibiotics without a prescription. The most common antibiotic used among children was amoxicillin.

Conclusions

The high prevalence of antibiotic use was observed in children under 5 years of age, and the major source to obtain antibiotics was to consult health professionals. Training on appropriate antibiotic use must be conducted for health professionals in not only public but also private sectors.

Molecular Cloning and Docking of speB Gene Encoding Cysteine Protease With Antibiotic Interaction in Streptococcus pyogenes NBMKU12 From the Clinical Isolates

Streptococcus pyogenes causes a variety of diseases ranging from mild diseases to severe invasive infections which result in significant morbidity and mortality. This study focuses on the antibiotic resistance of S. pyogenes and their interaction with cysteine protease. Around 36 beta-hemolytic isolates were collected from the clinical lab, of which seven isolates (19.4%) were identified as Streptococcus pyogenes. One of the seven isolates was collected from a urinary tract infection, which was identified by antibody agglutination and MALTI-TOF-MS, and it is designated as S. pyogenes NBMKU12. Around 8.3 to 66.6 % of the isolates were found to be resistant to one or more antimicrobial agents, especially, penicillin-G resistance was exhibited by 29.1% of the isolates. In the NBMKU12 isolate, the beta lactem (TEM) gene was detected among the 13 antibiotic genes for which it was tested. Furthermore, when analysis for presence of 13 virulence genes were carried out in NBMKU12 isolate, only speJ and speB were detected. The speB (streptococcal pyrogenic exotoxin B) encoding cysteine protease gene was cloned. This was followed by performing DNA sequencing to understand the putative cysteine protease interaction with antibiotics, inhibitors, and substrate. The speB gene consists of 1197 nucleotides and encodes a protein with multiple domains, including a signal peptide (aa 1-22), an inhibitor region (aa 27-156), and a catalytic cysteine domain (aa 160-367). The signal peptide cleavage site is predicted between Ala22 and Asn23. The putative 398 amino acid residues were found to have a theoretical pI of 8.76 and a molecular mass of 43,204.36 Da. The tested culture supernatants of NBMKU12 isolate exhibited the proteolytic activity against casein, papaya and pineapple used as substrates. The proteolytic activity suggests the expression of speB gene. Molecular docking analysis of cysteine protease showed that erythromycin (bond length 2.41 Å), followed by chloramphenicol (2.51 Å), exhibited a strong interaction; while penicillin-G (3.24 Å) exhibited a weak interaction, and this factor could be considered as a cause for penicillin-G resistance. The present study contributes to a better understanding of speB gene encoding cysteine protease, antibiotic resistance, and their interaction in the isolate, S. pyogenes NBMKU12. The antibiotics and cysteine protease interaction study confirms the resistance or sensitivity of S. pyogenes. Hence, it could be hypothesized that the isolate NBMKU12 is resistant to most of the tested antibiotics, and this resistance might be a cause for mutation.

Antimicrobial resistance in bacterial pathogens among hospitalized children with community acquired lower respiratory tract infections in Dongguan, China (2011-2016)

BACKGROUND

Bacterial pathogens are a major cause of childhood community acquired lower respiratory tract infections (CA-LRTIs), and few data described the impact of antimicrobial resistance on children with CA-LRTIs. This study aims to investigate the antimicrobial resistance in common bacterial agents among hospitalized children with CA-LRTIs between 2011 and 2016 in Dongguan, China.

METHODS

Sputum samples were collected from hospitalized children (0-5 years old) with CA-LRTIs in Dongguan Children's Hospital. Bacterial pathogens were detected using traditional culture methods, and disc diffusion tests were used to determine antibiotic resistance.

RESULTS

Among the 2360 samples analyzed, 342 (14.5%) were positive for bacterial infection. The most prevalent pathogen was MSSA (2.3%), followed by MRSA (1.5%), E. coli (1.7%), E. coli ESBLs (1.2%), K. pneumonia ESBLs (1.5%), K. pneumonia (1.4%) and S. pneumonia (1.3%). Of the hospitalized patients with bacteria causing of CA-LRTIs, 90.1% were less than 1-year-old. MSSA and MRSA were more commonly isolated in infants less than 3 months. E. coli, K. pneumonia and K. pneumonia ESBLs were more common bacteria causing CA-LRTIs in infants less than 1 month. Resistance levels to penicillins, fluoroquinolones, macrolides, cephalosporins, carbapenems and vancomycin varied in different bacteria.

CONCLUSIONS

S. aureus, E coli and K. pneumonia were the common bacterial isolates recovered from chidren with CA-LTRIs during 2011-2015. Age group of under 1 year old was at a high risk of bacterial infections. Many isolates showed antibiotic resistance level was associated with antibiotic usage in clinic. Increasing surveillance of antibiotic resistance is urgently needed and develops better strategies to cure the antibiotic abuse in China.

Antibacterial resistance in Streptococcus pyogenes (GAS) from healthy carriers and tonsillitis patients and association with antibacterial sale in the Faroe Islands

The aim of this study was to investigate the antibacterial resistance of Streptococcus pyogenes (GAS), and correlate the findings with the sales of erythromycin and tetracycline. General practitioners in the Faroe Islands were recruited to send oropharyngeal swabs. From an ongoing pneumococcal study, nasopharyngeal swabs were sampled from healthy children 0-7 years of age. Erythromycin susceptibility data from Iceland were obtained from the reference laboratory at the Landspitali University Hospital. Susceptibility testing in the Faroe Islands and Iceland was performed according to CLSI methods and criteria. The resistance rate to erythromycin and tetracycline found in patients in the Faroe Islands in 2009/2010 was 6% and 30% respectively. Tetracycline resistance in patients declined significantly from 2009 to 2010 (37-10%, p-value = 0.006 < 0.05) and differed significantly between age groups (p-value = 0.03 < 0.05). In Iceland, there was a peak in erythromycin resistance in 2008 (44%) and a substantial decrease in 2009 (5%). Although the prevalence of erythromycin and tetracycline resistance in the Faroe Islands and Iceland may be associated with antimicrobial use, sudden changes can occur with the introduction of new resistant clones.

Gemifloxacin for the Management of Community-Acquired Respiratory Tract Infections

Community-acquired lower respiratory tract infections (LRTIs) exert a growing clinical and financial burden on healthcare systems and employers. In addition, antimicrobial resistance among pathogens, such as Streptococcus pneumoniae, has compromised the use of commonly prescribed antimicrobial compounds. Newer fluoroquinolones have been developed to meet these emerging demands. Gemifloxacin is a potent, dual-acting fluoroquinolone with excellent activity against S. pneumoniae (MIC(90)0.03-0.06 microg/ml) including those strains demonstrating resistance to other classes of antibiotics. Gemifloxacin demonstrated excellent clinical success in community-acquired lower respiratory infections, has an acceptable safety profile, and is a cost-effective alternative in the management of LRTIs including those caused by resistant pathogens.

Description of macrolide-resistant and potential virulent clones of Streptococcus pyogenes causing asymptomatic colonization during 2000-2006 in the Lisbon area

The asymptomatic oropharyngeal colonization rate by Streptococcus pyogenes was 10.7% in children (901 among 8,405 children 0-16 years old) and 3.3% in adults (37 among 1,126 households of children) in the Lisbon area during 2000-2006. Macrolide-resistant S. pyogenes from children (n = 149) was variable with time: 9.8-10.7% in 2000-2002, 28.1% in 2003, 19.6-2.7% in 2004-2005 and 14.6% in 2006. Eight lineages (97.3% of isolates) were identified based on at least 80% similarity of PFGE patterns, T types, emm types and multilocus sequence types (ST). The elevated frequency of macrolide resistance was associated with M phenotype lineages I (emm12/ST36) and V (emm4, emm75/ST39 and a novel emmstMrp6 type) and with one cMLS(B) lineage IV (emm28/ST52) known to be associated with upper respiratory tract and invasive infections. Significant associations (p < 0.05) between emm type/virulence genotype were found, such as emm1/speA (+) ssa (-), emm4/ssa (+) prtF1 (+), emm12/speA (-) ssa (-). The high prevalence (>20%) of speC, prtF1 or ssa was probably caused either by clonal dissemination (speC), or to horizontal gene transfer events (prtF1 and ssa). This report contributes to a better understanding of the molecular epidemiology and evolution of macrolide-resistant S. pyogenes causing symptom-free oropharyngeal colonization. These colonizing strains carry macrolide resistance and virulence genes capable of being transferred to other bacterial species sharing the same niche.

Pneumonia in the developed world

In this paper, we review the literature on the management of pneumonia in the developed world setting. Pneumonia is usually diagnosed on the basis of a cough, respiratory distress, a fever, and chest X-ray changes. Pneumonia affects all paediatric age groups, though the highest incidence is in the under 5s. There is a significant burden of primary and secondary care illness, although mortality is low. Inpatient admission rates for pneumonia may have increased in recent years in some regions. Pneumonia is unlikely if a child presents with solely wheeze. In routine clinical practice, a microbiological diagnosis is often not made, because current tests are insensitive. Aetiology varies with geographical location, but approximately half of cases are viral. The mainstay of management of moderate pneumonia (the commonest group presenting to secondary care) is careful assessment, and oral antibiotics, followed by early discharge when the patient shows signs of improvement. We summarise the available clinical trial data from the developed world; most of these trials are not adequately powered. Patients with moderately severe pneumonia do not require invasive investigation, but clinical judgement should be used to identify and investigate more complex cases. We discuss several pathogens that have gained importance as causal agents, including non-vaccinated strains of S. pneumoniae, Panton Valentine leucocidin S. aureus, H1N1 Influenza A and Human Bocavirus. The importance of antimicrobial resistance is considered, and we review recent data on long term effects of pneumonia in childhood. By reviewing the available literature, we demonstrate that there are clear evidence gaps, and we suggest future areas for clinical research.

Comparison of transformation frequencies among selected Streptococcus pneumoniae serotypes

Although there are over 90 serotypes of Streptococcus pneumoniae, antimicrobial resistance is predominantly found in a limited number of serotypes/serogroups, namely 6, 9, 14, 19 and 23. There is no compelling mechanism to account for this restriction. We aimed to determine whether serotypes commonly associated with drug resistance have higher transformation frequencies than those that are susceptible to antimicrobial agents. An in vitro investigation of the genetic transformation frequency of drug-resistant serotypes compared with that of susceptible serotypes under the influence of synthetic competence-stimulating peptides was performed. The transforming DNA was genomic DNA carrying a Tn916-like transposon containing the mefE gene that confers resistance to erythromycin. It was observed that serotypes 6, 9, 14, 19 and 23, which are highly associated with drug resistance, do not exhibit a higher degree of transformation efficiency than other serotypes. These findings suggest that the association of serotype with drug resistance is likely due to prolonged exposure to transforming DNA resulting from longer nasopharyngeal carriage and to a greater selective pressure from antimicrobials, particularly in children. This is the first study to compare the transformation frequencies of pneumococcal clinical isolates using genomic DNA that carries the composite Tn916-like element.

Current issues in the management of acute bacterial sinusitis in children

OBJECTIVE

To review and summarize recent challenges in the microbiology and treatment of acute bacterial sinusitis (ABS), one of the most common infectious diseases in the pediatric community.

METHODS

A review of recent medical literature from 1990 to 2006 was acquired using the National Library of Medicine's PUBMED database.

RESULTS

Multiple mechanisms of penicillin resistance have been identified: porin channel blockage, beta-lactamase production, and changes in penicillin-binding proteins (PBPs). Other factors affecting treatment efficacy include the role of normal nasopharyngeal flora, such as alpha-streptococci. The more widely documented shift in the causative pathogens of acute otitis media (AOM) following the release of the heptavalent pneumococcal conjugate vaccine (PCV7) has also been documented in two studies of ABS in children.

CONCLUSIONS

Treatment of ABS in children is complicated by a number of emerging changes in pathogen resistance patterns. These include beta-lactamase-negative ampicillin resistance (BLNAR) and multi-drug resistance, bacterial interference, and geographic data. These phenomena are likely to impact the treatment of URIs. Appropriate diagnosis and differentiation from viral sinusitis is essential prior to initiating therapy. Clinician education about these emerging issues remains an important strategy in diagnosing and treating ABS in children. This includes an understanding of known patient adherence to antibiotic therapy, such as taste, tolerability, dosing schedule, therapy duration, and patient preference. Clinicians should review judicious ABS treatment approaches that employ agents with documented efficacy against implicated pathogens.

Mechanisms, molecular and sero-epidemiology of antimicrobial resistance in bacterial respiratory pathogens isolated from Japanese children

Background

The clinical management of community-acquired respiratory tract infections (RTIs) is complicated by the increasing worldwide prevalence of antibacterial resistance, in particular, β-lactam and macrolide resistance, among the most common causative bacterial pathogens. This study aimed to determine the mechanisms and molecular- and sero-epidemiology of antibacterial resistance among the key paediatric respiratory pathogens in Japan.

Methods

Isolates were collected at 18 centres in Japan during 2002 and 2003 from children with RTIs as part of the PROTEKT surveillance programme. A proportion of Haemophilus influenzae isolates was subjected to sequencing analysis of the ftsI gene; phylogenetic relatedness was assessed using multilocus sequence typing. Streptococcus pneumoniae isolates were screened for macrolide-resistance genotype by polymerase chain reaction and serotyped using the capsular swelling method. Susceptibility of isolates to selected antibacterials was performed using CLSI methodology.

Results and Discussion

Of the 557 H. influenzae isolates collected, 30 (5.4%) were β-lactamase-positive [BL+], 115 (20.6%) were BL-nonproducing ampicillin-resistant (BLNAR; MIC ≥ 4 mg/L) and 79 (14.2%) were BL-nonproducing ampicillin-intermediate (BLNAI; MIC 2 mg/L). Dabernat Group III penicillin binding protein 3 (PBP3) amino acid substitutions in the ftsI gene were closely correlated with BLNAR status but phylogenetic analysis indicated marked clonal diversity. PBP mutations were also found among BL+ and BL-nonproducing ampicillin-sensitive isolates. Of the antibacterials tested, azithromycin and telithromycin were the most active against H. influenzae (100% and 99.3% susceptibility, respectively). A large proportion (75.2%) of the 468 S. pneumoniae isolates exhibited macrolide resistance (erythromycin MIC ≥ 1 mg/L); erm(B) was the most common macrolide resistance genotype (58.8%), followed by mef(A) (37.2%). The most common pneumococcal serotypes were 6B (19.7%), 19F (13.7%), 23F (13.5%) and 6A (12.8%). Telithromycin and amoxicillin-clavulanate were the most active antibacterials against S. pneumoniae (99.8% and 99.6% susceptibility, respectively).

Conclusion

Approximately one-third of H. influenzae isolates from paediatric patients in Japan are BLNAI/BLNAR, mainly as a result of clonally diverse PBP3 mutations. Together with the continued high prevalence of pneumococcal macrolide resistance, these results may have implications for the clinical management of paediatric RTIs in Japan.

Effective treatment strategies for paediatric community-acquired pneumonia

Pneumonia is the leading cause of death in children under 5 years of age worldwide and a cause of morbidity in a considerable number of children. A number of studies have sought to identify the ideal choice of antibiotics, route of administration and optimum duration of treatment based on the most likely aetiological agents. Emerging bacterial resistance to antibiotics is also an important consideration in treatment. However, inconsistent clinical and radiological definitions of pneumonia make comparison between studies difficult. There is also a lack of well designed adequately powered randomised controlled trials. This review describes the difficulties encountered in diagnosing community-acquired pneumonia, aetiology, treatment strategies with recommendations and highlights areas for further research.

Application of two methods to determine killing of Streptococcus pneumoniae by various fluoroquinolones

Minimum inhibitory concentration (MIC) testing measures the lowest drug concentration that prevents microbial growth using an inoculum of 10(5) colony forming units/ml (cfu/ml) whereas the mutant prevention concentration (MPC) (inoculum approximately 10(10) cells) defines the antimicrobial drug concentration threshold that would require an organism to possess two simultaneous mutations for continued growth in the presence of the drug. The rates at which multidrug-resistant Streptococcus pneumoniae [MDRSP] were killed by the respiratory fluoroquinolones, gatifloxacin, gemfloxacin, levofloxacin and moxifloxacin, were compared based on the MIC and MPC drug concentrations and at inocula ranging from 10(6)-10(9) cfu/ml. The MIC drug concentration failed to eradicate all viable cells whereas the MPC drug concentration resulted in 99.9% to 100% cellular reduction following 12-24 hours of drug exposure. MPC values against S. pneumoniae were different for each fluoroquinolone. The MPC drug concentration prevents the selection of multidrug-resistant or fluoroquinolone-resistant S. pneumoniae. The value of dosing of antimicrobial agents based on MPC thresholds results in a rapid reduction in viable cells--even at higher inocula which are more reflective of organism burden in pneumonia. The rapid reduction in viable cells observed at MPC drug concentrations may not only have an impact on preventing the selection of resistant mutants but may also help explain the rapid symptom resolution seen with new fluoroquinolones since these agents lead to little or low release of cell contents which are known to drive the inflammatory response.

Genetic diversity of pneumococcal surface protein A of Streptococcus pneumoniae meningitis in German children

Pneumococcal surface protein A (PspA) is a possible candidate for the development of a pneumococcal vaccine that has the potential to offer a broad range of protection. PspA genes of pneumococcal meningitis isolates (n=40) isolated as part of an ongoing population-based nation-wide surveillance program on invasive pneumococcal disease in children in Germany were analyzed to expand our knowledge on the distribution of PspA families of this important vaccine candidate in Germany. The serotype distribution of the strains was as follows: serotype 4 (n=3), 6B (5), 9V (2), 14 (8), 18C (6), 19F (5), 23F (6), and 7F (5). The pspA genes of these strains could be assigned to 2 families containing 20 pneumococcal strains each. Family I could be subdivided into 2 clades with 17 strains in clade 1 and 3 strains in clade 2, and family II could be subdivided into 3 subgroups (clades 3-5) containing 16, 3, and 1 strain, respectively. Pneumococcal serotypes were distributed evenly over all clades and families. Interestingly, the distribution of the PspA gene families in Germany was seen to differ slightly that found in other countries.

Antibiotic resistance patterns among respiratory pathogens at a German university children's hospital over a period of 10 years

Growing antimicrobial resistance among Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis is raising major concern worldwide. Strains of S. pneumoniae, H. influenzae and M. catarrhalis isolated from children with respiratory tract as well as invasive infection in a South-Western region of Germany between 1993 and 2002 were tested for susceptibility to common antibiotics including penicillins, cephalosporins and macrolides. A total of 2,362 S. pneumoniae, 2,501 H. influenzae, and 1,982 M. catarrhalis isolates were tested. Only two S. pneumoniae strains were found to be highly resistant to penicillin. The overall rate of intermediate resistance to penicillin was 3.5%. There was a significant increase in erythromycin resistance from 5% in 1993 to 12.2% in 2002 (P=0.001). No increase in ampicillin resistance was observed for H. influenzae over time. The rate of cefaclor resistance, however, increased from 4.5% to 11.8% (P<0.0001). Furthermore, a massive increase in erythromycin resistance from 26% to 40% was observed (P<0.0001). The vast majority of M. catarrhalis isolates were beta-lactamase positive, the minimal inhibitory concentration to ampicillin, however, exceeded only in 3% of all strains the cut-off of 1.5 mg/l. The erythromycin resistance rate of M. catarrhalis was 0.3%.

CONCLUSION

There is still a low rate of penicillin/ampicillin resistance in S. pneumoniae, and H. influenzae, but an alarming increase in resistance to erythromycin, and in H. influenzae a significant increase in cefaclor resistance was observed over the 10-year period in South-Western Germany.

In-vitro susceptibility and molecular characterisation of macrolide resistance mechanisms among Streptococcus pneumonia isolates in The Netherlands: the DUEL 2 study

In total, 881 presumptive clinical isolates of Streptococcus pneumoniae collected from throughout The Netherlands were analysed to determine their mechanisms of macrolide resistance. Isolates were identified initially by participating laboratories using their own standard identification technique, followed by determination of MICs with Etests. Only 797 isolates were confirmed as pneumococci following bile-solubility tests, lytA PCR and 16S rRNA sequencing. Of these confirmed pneumococci, 59 (7.4%) isolates were macrolide-resistant. Analysis by PCR indicated that 34 (57.6%) isolates harboured only the erm(B) gene and 16 (27.1%) only the mef gene. Three (5.1%) isolates carried both erm(B) and mef, while six (10.2%) isolates were negative for both mechanisms. Of the six negative isolates, three had a mutation in the 23S rRNA gene, and three were negative for all mechanisms tested. No isolates with the erm(A) subclass erm(TR) gene were detected. Among the 19 mef-positive isolates, 14 (73.7%) carried the mef(A) gene, and only five (26.3%) carried the mef(E) gene. No linezolid cross-resistance or multiresistance (resistance to more than two classes of antibiotics) was observed.

Epidemiologic study of conjunctivitis-otitis syndrome

We conducted a prospective cross-sectional epidemiologic study of conjunctivitis-otitis syndrome during two 3-week periods of consecutive winters. A representative sample of 184 pediatricians and ear, nose and throat specialists in the Paris area recruited 2901 children from 6 to 36 months of age presenting with acute otitis media, of whom 465 (16%) also had purulent conjunctivitis. In sampled children, the culture of the conjunctival exudate yielded bacterial pathogens in 419 patients: Haemophilus influenzae, 371 (89%); Streptococcus pneumoniae, 72 (17%); and Branhamella catarrhalis, 23 (5%). Pulsed field gel electrophoresis analysis of paired H. influenzae isolates from the conjunctival exudate and middle ear fluid of 21 patients showed identical strains in each patient.

Erregerspektrum der akuten bakteriellen Rhinitis/Sinusitis und Resistenzlage

BACKGROUND AND OBJECTIVE

Bacterial rhinosinusitis is one of the most frequent indications for an antibiotic therapy. The objective of this study was the analysis of the current pathogen spectrum and its antimicrobial susceptibility.

MATERIAL AND METHODS

Between 1999 and 2004, 188 specimens obtained from 170 patients with acute, purulent rhinosinusitis were analysed.

RESULTS

A total of 217 pathogens were isolated. The most common isolates were Streptococcus pneumoniae (33%), Haemophilus influenzae (27%), Staphylococcus aureus (13%), Moraxella catarrhalis (11%) and streptococci (7%). S. pneumoniae, H. influenzae and M. catarrhalis were the predominant pathogens in children. S. pneumoniae, S. aureus and streptococci, however, dominated in specimens from adults.

CONCLUSION

Based on these results, adults should be treated with an aminopenicillin with beta-lactamase inhibitor or a cephalosporin of the second generation. For children , however, the first line antibiotic is an aminopenicillin.

Molecular epidemiology of macrolide-resistant isolates of Streptococcus pneumoniae collected from blood and respiratory specimens in Norway

Norway has a low prevalence of antimicrobial resistance, including macrolide-resistant Streptococcus pneumoniae (MRSP). In a nationwide surveillance program, a total of 2,200 S. pneumoniae isolates were collected from blood cultures and respiratory tract specimens. Macrolide resistance was detected in 2.7%. M-type macrolide resistance was found in 60% of resistant isolates, and these were mainly mef(A)-positive, serotype-14 invasive isolates. The erm(B)-encoded macrolide-lincosamide-streptogramin B (MLS(B)) type dominated among the noninvasive isolates. One strain had an A2058G mutation in the 23S rRNA gene. Coresistance to other antibiotics was seen in 96% of the MLS(B)-type isolates, whereas 92% of the M-type isolates were susceptible to other commonly used antimicrobial agents. Serotypes 14, 6B, and 19F accounted for 84% of the macrolide-resistant isolates, with serotype 14 alone accounting for 67% of the invasive isolates. A total of 29 different sequence types (STs) were detected by multilocus sequence typing. Twelve STs were previously reported international resistant clones, and 75% of the macrolide-resistant isolates had STs identical or closely related to these clones. Eleven isolates displayed 10 novel STs, and 7/11 of these "Norwegian strains" coexpressed MLS(B) and tetracycline resistance, indicating the presence of Tn1545. The invasive serotype-14 isolates were all classified as ST9 or single-locus variants of this clone. ST9 is a mef-positive M-type clone, commonly known as England(14)-9, reported from several European countries. These observations suggest that the import of major international MRSP clones and the local spread of Tn1545 are the major mechanisms involved in the evolution and dissemination of MRSP in Norway.

Antimicrobial susceptibility survey of Streptococcus pyogenes isolated in Japan from patients with severe invasive group A streptococcal infections

We assessed antimicrobial susceptibility against 211 Streptococcus pyogenes strains isolated from patients with severe invasive group A streptococcal infections. Overall, 3.8, 1.4, 1.4, and 0.5% of the isolates were resistant to erythromycin, clindamycin, telithromycin, and ciprofloxacin, respectively, and 10.4% had intermediate resistance to ciprofloxacin. All isolates were susceptible to ampicillin and cefotaxime.

Clonal spread of fluoroquinolone non-susceptible Streptococcus pyogenes

BACKGROUND

Fluoroquinolones are an important group of antibiotics widely used in adults, and, despite the absence of official approval, these drugs are also used in children. So far, resistance to fluoroquinolones in Streptococcus pyogenes is very rare.

METHODS

During a national surveillance programme in Belgium from 1999 to 2002, 2793 non-duplicate S. pyogenes recovered from tonsillopharyngitis patients were screened for fluoroquinolone resistance. Mutations in topoisomerase genes and the presence of any efflux pump activity were investigated to elucidate the fluoroquinolone resistance mechanisms. Clonality was assessed by pulsed-field gel electrophoresis (PFGE) and emm typing.

RESULTS

Non-susceptibility to fluoroquinolones, defined as ciprofloxacin MIC > or = 2 mg/L, was identified in 152 (5.4%) of 2793 S. pyogenes. Fifty-five (36%) fluoroquinolone non-susceptible isolates were investigated for known resistance mechanisms; all showed mutations in parC, and 29 (19%) isolates also in parE; antibiotic efflux was not noted. Two major PFGE types comprised 88% of fluoroquinolone non-susceptible S. pyogenes and belonged to serotypes emm6 and emm75. Overall, emm6 and emm75 constituted >90% of all fluoroquinolone non-susceptible isolates and showed a significant temporal and geographical shift within Belgian provinces. Although fluoroquinolone-susceptible S. pyogenes also showed fluctuations in the predominant S. pyogenes serotypes, emm6 or emm75 were under-represented in this population. Approx. 55% of the fluoroquinolone non-susceptible isolates were recovered from children ( < or =16 years).

CONCLUSIONS

We show here, for the first time, a multi-clonal spread of fluoroquinolone non-susceptible S. pyogenes exhibiting a known resistance mechanism. Non-susceptibility to fluoroquinolones in paediatric isolates is of concern.

Identification of a hemin utilization protein of Moraxella catarrhalis (HumA)

Moraxella catarrhalis is a major cause of acute otitis media in young children and has also been implicated as an important cause of exacerbations in adults with underlying pulmonary disease. Due to the considerable level of antibiotic resistance and the high degree of carriage rates in young children, it is likely that the incidence of M. catarrhalis infections will continue to rise. M. catarrhalis is a strict human respiratory pathogen, and this bacterium uses both transferrin and lactoferrin receptors to fulfill the essential iron requirement for survival in vivo. However, these are the only described iron acquisition systems for this organism. In this report we have demonstrated that M. catarrhalis can also utilize hemin as a sole source of iron for growth. In addition, we have identified and characterized an outer membrane protein with homology (26 to 28% similarity) to other known hemin binding and uptake proteins in related gram-negative organisms (i.e., Bordetella and Yersinia spp.). This newly described M. catarrhalis protein, termed HumA, is capable of directly binding to hemin coupled to a solid-phase matrix. M. catarrhalis HumA expressed on the surface of an Escherichia coli hemA-deficient strain (K-12 EB53) is fully capable of complementing the defect and thus restoring the ability of this strain to grow in the presence of hemin. When M. catarrhalis is grown in the presence of hemin, HumA expression is clearly increased as shown by Western blotting with polyclonal antiserum developed against a HumA peptide. In addition, growth analyses revealed that a HumA-deficient mutant of M. catarrhalis (7169::humA) is restricted for growth in the presence of hemin as the sole iron source compared to the wild-type strain. We conclude that HumA is an essential component of a hemin uptake and utilization system previously undescribed for M. catarrhalis, thus providing another mechanism of iron acquisition that may facilitate persistent colonization of the mucosal surface.

Therapeutic implications of macrolide resistance in pneumococcal community-acquired lower respiratory tract infections

Macrolide anti-bacterials are widely used for the empirical treatment of lower respiratory tract infections (RTIs) due to their activity against Streptococcus pneumoniae and other common respiratory pathogens and good safety/tolerability profile. However, the prevalence of macrolide resistance, particularly pneumococcal macrolide resistance, is increasing all around the world. The mechanisms underlying macrolide resistance include efflux pump, methylase activity and, less commonly, ribosomal mutation, which produce differing levels of resistance. Growth in macrolide resistance has been linked to the increased use of these agents, and several risk factors for the development of resistance have been identified. There are emerging data to suggest that in vitro macrolide resistance may increase the likelihood of treatment failure in patients with lower RTIs. However, at present, treatment failure is rare and randomised; intervention-based trials investigating the impact of anti-bacterial resistance on clinical outcomes are lacking. Strategies to promote appropriate use of macrolides and other anti-bacterials are needed, both to maximise therapeutic impact and to minimise the development of resistance. Furthermore, there is a need for alternative anti-bacterial agents which have high efficacy against respiratory pathogens (including resistant strains) and a low potential to induce resistance.