Pneumococcal resistance patterns in Europe

Evolution of Antimicrobial Susceptibility to Penicillin in Invasive Strains of Streptococcus pneumoniae during 2007-2021 in Madrid, Spain

The use of pneumococcal conjugate vaccines has affected the epidemiology and distribution of Streptococcus pneumoniae serotypes causing Invasive Pneumococcal Disease (IPD). The aim of this study was to analyze the evolution of the phenotypical profiles of antimicrobial susceptibility to penicillin (PEN) in all IPD strains isolated in Madrid, Spain, during 2007-2021. In total, 7133 invasive clinical isolates were characterized between 2007 and 2021. Levels of PENR and PNSSDR were 2.0% and 24.2%, respectively. In addition, 94.4% of all the PENR belonged to four serotypes, including 11A (33.6%), 19A (30.8%), 14 (20.3%) and 9V (9.8%). All the strains of serotype 11A, which is a non-PCV13 serotype, were detected after the year 2011. Serotypes 6C, 15A, 23B, 24F, 35B, 19F, 16F, 6B, 23F, 24B, 24A, 15F and a limited number of strains of serogroups 16 and 24 (non-typed at serotype level) were associated with PNSSDR (p < 0.05). PNSSDR strains of non-PCV13 serotypes 11A, 24F, 23B, 24B, 23A and 16F were more frequent from 2014 to 2021. The changes in S. pneumoniae serotype distribution associated with the use of conjugate vaccines had caused in our region the emergence of non-PCV13 pneumococcal strains with different PENR or PNSSDR patterns. The emergence of serotype 11A resistant to penicillin as the most important non-PCV13 serotype is a worrisome event with marked relevance from the clinical and epidemiological perspective.

Limosilactobacillus (Lactobacillus) fermentum ALAL020, a Probiotic Candidate Bacterium, Produces a Cyclic Dipeptide That Suppresses the Periodontal Pathogens Porphyromonas gingivalis and Prevotella intermedia

Periodontal disease develops as a result of oral microbiota in dysbiosis, followed by the growth of periodontal pathogens such as Porphyromonas gingivalis and Prevotella intermedia. In case of acute symptoms, antibacterial agents and disinfectants are administered, however the appearance of drug-resistant bacteria and allergies cause problems. In recent years, studies on the effects of probiotics have been conducted as an alternative therapy for periodontitis. However, the basic mechanism of the inhibitory effect of probiotic bacteria on periodontal disease has not been clearly elucidated. To clarify the antibacterial mechanism of probiotics against periodontal pathogens, we used Limosilactobacillus (Lactobacillus) fermentum ALAL020, which showed the strongest antibacterial activity against P. gingivalis and P. intermedia among 50 screened lactic acid bacteria strains. The antibacterial substances produced were identified and structurally analyzed. After neutralizing the MRS liquid culture supernatant of ALAL020 strain, the molecular weight (m/z) of the main antibacterial substance separated by gel filtration column chromatography and reverse phase HPLC was 226.131. This low molecular weight compound was analyzed by LC-MS and disclosed the composition formula C₁₁H₁₈O₃N₂, however the molecular structure remained unknown. Then, structural analysis by NMR revealed C₁₁H₁₈O₃N₂ as the cyclic dipeptide, “hexahydro-7-hydroxy-3- (2-methylpropyl) pyrrolo [1,2-a] pyrazine-1,4-dion cyclo (Hyp-Leu) “. Based on the results of this analysis, cyclo (Hyp-Leu) was chemically synthesized and the antibacterial activity against P. gingivalis and P. intermedia was measured. The minimum inhibitory concentration (MIC) was 2.5 g/L and the minimum bactericidal concentration (MBC) was shown to be less than 5 g/L. In addition, an in vitro epithelial tissue irritation test at 10 g/L showed no tissue toxicity. So far there are no reports of this peptide being produced by probiotic bacteria. Furthermore, antibacterial activity of this cyclic dipeptide against periodontal disease bacteria has not been confirmed. The results of this study might lead to a comprehensive understanding of the antibacterial mechanism against periodontal disease bacteria in future, and are considered applicable for the prevention of periodontal disease.

Assessment of attitudes and practices of young Malaysian adults about antibiotics use: a cross-sectional study

Objective:

The present study was aimed to evaluate the practices and attitudes of young Malaysian adults towards the use of antibiotics, and to determine the socioeconomic factors associated with the antibiotic use.

Methods:

A survey was carried in Cheras community by approaching a conveniently selected sample of 480 participants. A pre-tested questionnaire was used for data collection.

Result:

Of 480 participants approached, 400 agreed to participate in this study, giving a response rate of 83.3%. The study results showed that 42.75% of the participants exhibited poor attitudes towards antibiotic usage. Chinese race and high income were significantly associated with the positive attitudes towards antibiotic usage. It is shown that the practice of the participants towards antibiotics was relatively poor. The majority of participants agreed that they do not consult a doctor for minor illnesses (64%). The main reason for not consulting a doctor was the high fees of consultation (34.25%) and the inconvenience of visit (29.25%). However, a large proportion of respondents (77.5%) agreed that there is a need to enhance antibiotic education among public.

Conclusion:

The study results identified some crucial gaps in the attitudes and practices of Cheras community about the use of antibiotics. Thus, improving the public knowledge and changing their attitude towards antibiotic use along with proper interventions to regulate the ease of their availability would play a significant role for the effective use of antibiotics in the community.

Population structure, epidemiology and antibiotic resistance patterns of Streptococcus pneumoniae serotype 5: prior to PCV-13 vaccine introduction in Eastern Gambia

Background

Streptococcus pneumoniae serotype 5 is among the most common serotypes causing invasive pneumococcal disease (IPD) in The Gambia. We anticipate that introduction of the 13-valent pneumococcal conjugate vaccine (PCV-13) into routine vaccination in The Gambia will reduce serotype 5 IPD. However, the emergence of new clones that have altered their genetic repertoire through capsular switching or genetic recombination after vaccination with PCV-13 poses a threat to this public health effort. In order to monitor for potential genetic changes post-PCV-13 vaccination, we established the baseline population structure, epidemiology, and antibiotic resistance patterns of serotype 5 before the introduction of PCV-13.

Methods

Fifty-five invasive S. pneumoniae serotype 5 isolates were recovered from January 2009 to August 2011 in a population-based study in the Upper River Region of The Gambia. Serotyping was done by latex agglutination and confirmed by serotype-specific Polymerase Chain Reaction (PCR). Genotyping was undertaken using Multilocus Sequence Typing (MLST). Antimicrobial sensitivity was done using disc diffusion. Contingency table analyses were conducted using Pearson’s Chi² and Fisher’s exact test. Clustering was performed using Bionumerics version 6.5.

Results

MLST resolved S. pneumoniae serotype 5 isolates into 3 sequence types (ST), namely ST 289(6/55), ST 3339(19/55) and ST 3404(30/55). ST 289 was identified as the major clonal complex. ST 3339, the prevalent genotype in 2009 [84.6 % (11/13)], was replaced by ST 3404 [70.4 % (19/27)] in 2010 as the dominant ST. Interestingly, ST 3404 showed lower resistance to tetracycline and oxacillin (P < 0.001), an empirical surrogate to penicillin in The Gambia.

Conclusions

There has been an emergence of ST 3404 in The Gambia prior to the introduction of PCV-13. Our findings provide important background data for future assessment of the impact of PCV-13 into routine immunization in developing countries, such as The Gambia.

Controlled-delivery chlorhexidine chip versus amoxicillin/metronidazole as adjunctive antimicrobial therapy for generalized aggressive periodontitis: a randomized controlled clinical trial

BACKGROUND

Subgingival application of chlorhexidine via a controlled-delivery device (CHX chip) improves the clinical outcome of scaling/root planing (SRP) in therapy for chronic periodontitis. Generalized aggressive periodontitis (GAP) is commonly treated with SRP and adjunctive antimicrobial medication. To date, the efficacy of CHX chips in GAP therapy has not been evaluated.

AIM

To compare SRP plus adjunctive CHX chip placement with SRP plus adjunctive systemic amoxicillin/metronidazole with regard to clinical efficacy in first-line therapy for GAP.

MATERIAL AND METHODS

Thirty-six GAP patients were treated with SRP and randomly with either placement of CHX chips or systemic amoxicillin/metronidazole. Clinical attachment level (CAL), probing depth (PD), bleeding on probing (BoP) and suppuration (Pus) were measured at baseline, 3 and 6 months after therapy.

RESULTS

CAL, PD, BoP and Pus were significantly reduced in both groups after 3 months. In the CHX chip group, PD significantly increased again between 3 and 6 months. Finally, amoxicillin/metronidazole patients presented significantly more CAL "gain", PD reduction and less remaining deep sites after 6 months. Pus remained detectable in CHX chip patients only.

CONCLUSIONS

In first-line non-surgical therapy for GAP, SRP plus adjunctive systemic amoxicillin/metronidazole was more efficacious in clinically relevant measures of outcome than SRP plus adjunctive placement of CHX chips.

Proportion of antibiotic resistance in subgingival plaque samples from Mexican subjects

AIM

To determine the proportion of bacteria resistant to amoxicillin and doxycycline in subgingival plaque samples from Mexican subjects.

MATERIALS AND METHODS

Two subgingival plaque samples were taken from 20 Mexican subjects. Samples were dispersed, diluted and plated on non-antibiotic agar plates and on plates containing 0.5, 1, 2, 4, 8 and 16 microg/ml of either amoxicillin or doxycycline. The proportion of resistant bacteria was calculated based on the total number of colony-forming units present in the non-antibiotic containing plates.

RESULTS

On average, 0.4-13.4% and 0.9-20.4% of the total cultivable subgingival microbiota was resistant to the concentrations tested of amoxicillin and doxycycline, respectively. The differences between antibiotics were statistically significant for the 0.5, 2 and 4 mug/ml concentrations (p < 0.05, Wilcoxon's test).

CONCLUSIONS

Our findings revealed that a relatively small proportion of the total cultivable subgingival microbiota from Mexican subjects was resistant to amoxicillin and doxycycline.

Effect of intervention promoting a reduction in antibiotic prescribing by improvement of diagnostic procedures: a prospective, before and after study in general practice

OBJECTIVE

To investigate if an intervention aimed at improving the quality of the diagnostic procedures in Spanish general practice could lower antibiotic prescribing in patients with respiratory tract infections (RTIs).

METHODS

GPs in the intervention group (n=17) registered all patients with RTIs during a 3-week period before and after the intervention. The intervention was aimed at reducing prescribing of inappropriate antibiotics for RTIs by improving the diagnostic procedures and thereby helping the GPs to distinguish between bacterial and viral infections. It consisted of courses in management of RTI according to local clinical guidelines, and included implementation of two rapid diagnostic tests (StrepA and CRP measurement). Diagnoses and prescribing of antibiotics were assessed before and after the intervention, and compared to a control group not exposed to intervention (35 GPs).

RESULTS

The intervention led to a significant reduction in antibiotic prescribing. Before the intervention 36% (29%-44%) of consultations were followed by antibiotic prescribing, after the intervention 24% (20%-29%). Antibiotic prescribing in the control group not exposed to intervention was 32% (27%-38%). The reduction was most pronounced in patients with sinusitis and lower RTIs.

CONCLUSION

Quality improvement of diagnostic procedures may lead to a reduction of antibiotic prescribing in primary health care in Spain.

Trends in antibiotic resistance of respiratory tract pathogens in children in Geneva, Switzerland

Bacteria increasingly resistant to antibiotics are a major treatment concern of respiratory tract pathogens in children. The aim of this study was to assess the trends of resistance of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis to several classes of antibiotics in children<16 years of age and to compare its prevalence with surrounding countries. We studied retrospectively the susceptibility of respiratory tract pathogens isolated from specimens collected from patients at the Geneva Children's Hospital between 1989 and 2004. The susceptibility of S. pneumoniae to penicillin decreased from 98% to 58% (P<0.001) within 16 years, mainly due to strains intermediately resistant (MICs 0.12-1.0 microg/ml). Also erythromycin-susceptible pneumococci decreased from 97% to 63% (P<0.001). The susceptibility of H. influenzae to amoxicillin also significantly declined (87% vs. 82%, P<0.001), and the susceptibility of M. catarrhalis to this drug almost disappeared (29% vs. 5%, P<0.001). However, in 2004 these two bacteria remained 100% susceptible to amoxicillin-clavulanic acid, second and third generation cephalosporins. Invasive H. influenzae strains were significantly more resistant to ampicillin than non-invasive strains, but no susceptibility difference between invasive and non-invasive S. pneumoniae was determined.

CONCLUSION

During the 16 years studied, the antibiotic resistance of respiratory tract pathogens steadily and significantly increased in children, especially S. pneumoniae. This situation in Geneva is similar to neighbouring France rather than to the rest of Switzerland. A permanent surveillance of microbial susceptibility to antibiotics is essential and a limitation of antibiotic prescription together with information of the judicious use may impede the actual resistance trend.

Variabilidad de la prescripción antibiótica en las infecciones respiratorias en dos países de Europa

BACKGROUND

Treatment for respiratory tract infections (RTI) in the primary care setting is empirical. Antibiotic prescribing patterns differ among countries and are based on the prevalence of antibiotic resistance in the geographical area. The aim of this study was to compare the antibiotics prescribed by general practitioners (GPs) for RTIs between Spain and Denmark.

METHODS

Observational multicenter survey carried out in the primary healthcare setting. Two groups of GPs in Spain and Denmark recorded all contacts with RTI patients during a 3-week period between November 2001 and January 2002.

RESULTS

A total of 2833 RTI cases were registered. Broad-spectrum penicillins and combinations of these drugs plus beta-lactamase inhibitors were the antibiotics most frequently prescribed by Spanish GPs (62.3%), followed by macrolides (22.3%). In contrast, narrow-spectrum penicillins were most commonly prescribed by Danish GPs (58% of all prescriptions), followed by macrolides (29%) (P < .001). Antibiotics most frequently prescribed for ear, tonsillar, sinus and bronchopulmonary infections were broad-spectrum penicillins among Spanish GPs and narrow-spectrum penicillins in Denmark. Spanish GPs prescribed penicillin V only for tonsillitis, accounting for 5.1% of the antibiotics used for this condition, whereas this drug accounted for 91.7% of the prescriptions by their Danish colleagues for the same indication.

CONCLUSIONS

The substantial differences in RTI management between the participating GPs should make us reflect on the rational use of antibiotics. The discrepancies disclosed may indicate dissimilarities in recommendations, traditions, habits, or antibiotic pressures between the countries studied.

Self-medication with antibiotics--does it really happen in Europe?

AIMS AND METHODS

The aim of this study was to determine whether antibiotics are used for self-medication in southern Spain, a region belonging to European Union. The data were collected by a survey in the Costa del Sol region, Spain during 2002 by using a convenience sample of 1000 Finns living permanently in the area (response rate 53%, n=530).

RESULTS

Antibiotics were used by 28% of the respondents during the previous 6 months before the query. Of the antibiotic users, 41% had bought their antibiotics without a prescription. Clearly the most common indication for antibiotic use was common cold, with almost half (45%) of the antibiotic users reporting it as purpose of medication, followed by sore throat (17%). The number of courses did not differ between prescription and non-prescription antibiotic users, most (64%) of the users having used one course. Neither did the groups differ according to background variables used, including the frequency of experiencing adverse reactions.

CONCLUSIONS

Unnecessary and unrational self-medication with antibiotics seems to be common in southern Spain among Finnish immigrants. This may indicate that Spanish health care system, including community pharmacies are failing their task in enhancing rational use of medicines. It is important that all the member countries within EU will take their responsibility in promoting public health goals in their national policy, e.g., in minimising the antibiotic resistance for expanding.

Antimicrobial profiles of periodontal pathogens isolated from periodontitis patients in the Netherlands and Spain

BACKGROUND AND AIM

Antimicrobial resistance of periodontal pathogens towards currently used antibiotics in periodontics has been investigated in a previous study. Microbial resistance in the periodontal microflora was more frequently observed in Spanish patients in comparison with Dutch patients. The aim of the present study was to compare antimicrobial susceptibility profiles of five periodontal bacteria isolated from periodontitis patients in Spain and in The Netherlands.

MATERIAL AND METHODS

Subgingival plaque samples from adult patients with periodontitis were collected and cultured on selective and non-selective plates. Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum and Micromonas micros were isolated and used for minimal inhibitory concentration tests using the Epsilometer (E-test) technique. Eight different antibiotics were tested on all bacterial isolates. MIC50 and MIC90 values for each antibiotic and each species were determined and the percentage of resistant strains was calculated.

RESULTS

Significantly higher MIC values were noted in Spanish strains of F. nucleatum for penicillin, ciprofloxacin, of P. intermedia for penicillin, amoxicillin and tetracycline, of M. micros for tetracycline, amoxicillin and azithromycin, and of P. gingivalis for tetracycline and ciprofloxacin. Based on breakpoint concentrations, a higher number of resistant strains in Spain were found in F. nucleatum for penicillin, amoxicillin and metronidazole, in Prevotella intermedia for tetracycline and amoxicillin, and in A. actinomycetemcomitans for amoxicillin and azithromycin. Resistance of P. gingivalis strains was not observed for any of the antibiotics tested both in Spain and The Netherlands.

CONCLUSIONS

Differences exist in the susceptibility profiles of periodontal pathogens isolated from periodontitis patients in Spain and in The Netherlands. This implicates that antibiotic susceptibility testing is necessary to determine efficacy of antimicrobial agents. Also, clinical studies with antibiotics should take these differences into account. The information from the present study indicates that it may not be possible to develop uniform protocols for usage of antibiotics in the treatment of severe periodontitis in the European Union.

Improving adherence with antimicrobial therapy for respiratory tract infections: a discussion of directly observed therapy (DOT) and short-course therapies

Although some of the variables associated with adherence (eg, patient age, place of residence) cannot be influenced, others are very amenable to modifications. Levels of adherence correlate with the convenience of dosage regimens, as shown in a number of clinical trials. Therefore, antimicrobial agents that are well accepted by patients should be considered whenever feasible. Such agents include those that enable shortterm therapy with the fewest daily doses and shortest effective treatment regimens. DOT, a cost-effective and clinically effective approach for certain chronic conditions, may also have practical implications for the treatment of acute infectious diseases, such as CAP, AECB, and otitis media. Although there are a number of challenges to the implementation of DOT for these conditions, such an approach may be beneficial, particularly when short-course antibiotic therapy is indicated and appropriate candidates are identified for treatment.

Characterization of German penicillin non-susceptible serotype 23F pneumococci using multilocus sequence typing

Three nationwide multicentre studies (n = 5071) showed an increase in antibiotic resistance in pneumococci in Germany. Serotype 23F was the predominant serotype (n = 45, 22.4 %), followed by 6B (n = 30, 14.9 %) and 9V (n = 19, 9.5 %). Multilocus sequence typing was used to characterize 45 serotype 23F strains with reduced penicillin susceptibility. The Spanish(23F)-1 clone [profile 4-4-2-4-4-1-1, sequence type (ST) 81] contributes significantly to the emergence of penicillin resistance in Germany (n = 21, 46.7 % of all penicillin non-susceptible serotype 23F isolates). Isolates of ST 277 (profile 7-13-8-6-6-12-8), which has been found previously in the Netherlands, are also observed, particularly in western Germany (n = 8, 17.8 %). A high proportion of strains (n = 11, 24.4 %) have sequence types that have not been reported to date from other countries (STs 353-362). The major penicillin-resistant clones are present in Germany, a country with relatively low levels of beta-lactam resistance.

Microbial shifts after subgingival debridement and formation of bacterial resistance when combined with local or systemic antimicrobials

Antibiotics have played a major role in the improvement of life expectancy in the last 50 years and have led many to believe that bacterial infections were about to vanish as a disease entity of any importance. Emerging problems resulting from a widespread use of antibiotics have modified the general perception of the capabilities of antimicrobial agents. Over the years, bacteria have become increasingly resistant to formerly potent antimicrobial agents, including some antiseptics. The use of antimicrobials may also disturb the delicate ecological equilibrium of the body, allowing the proliferation of resistant bacteria or non-bacterial micro-organisms. This shift may initiate new infections that are worse than the ones originally treated. No antimicrobial drug is absolutely non-toxic and the use of an agent carries accompanying risks. This paper discusses the development and occurrence of antimicrobial resistance in the subgingival flora towards antiseptics and local or systemic antibiotics and is focussed on the question: how can the outcome of periodontal therapy with/without antimicrobials be improved?

Outpatient antibiotic use and prevalence of antibiotic-resistant pneumococci in France and Germany: a sociocultural perspective

The prevalence of penicillin-nonsusceptible pneumococci is sharply divided between France (43%) and Germany (7%). These differences may be explained on different levels: antibiotic-prescribing practices for respiratory tract infections; patient-demand factors and health-belief differences; social determinants, including differing child-care practices; and differences in regulatory practices. Understanding these determinants is crucial for the success of possible interventions. Finally, we emphasize the overarching importance of a sociocultural approach to preventing antibiotic resistance in the community.

The future challenges facing the development of new antimicrobial drugs

The emergence of resistance to antibacterial agents is a pressing concern for human health. New drugs to combat this problem are therefore in great demand, but as past experience indicates, the time for resistance to new drugs to develop is often short. Conventionally, antibacterial drugs have been developed on the basis of their ability to inhibit bacterial multiplication, and this remains at the core of most approaches to discover new antibacterial drugs. Here, we focus primarily on an alternative novel strategy for antibacterial drug development that could potentially alleviate the current situation of drug resistance--targeting non-multiplying latent bacteria, which prolong the duration of antimicrobial chemotherapy and so might increase the rate of development of resistance.

Narrow versus broad spectrum antibacterials: factors in the selection of pneumococcal resistance to beta-lactams

Streptococus pneumoniae represents an interesting model to discuss the relative impact of broad versus narrow spectrum antibacterials as potential selectors for resistance. Indeed, this pathogen is responsible for potentially severe infections in the community, and has a great capacity for acquisition of resistance to antibacterial agents. It has been the focus of many studies to elucidate some unique aspects of molecular biology, including the adaptive mechanisms responsible for emergence and spread of multiresistance. In the past, the use of narrow spectrum agents was recommended in order to try to reduce the risk of selection of resistance. This concept is nowadays somewhat obsolete for several reasons. S. pneumoniae is able to acquire resistance to antibacterials belonging to different families of drugs through different molecular mechanisms. Thus, selection of multiresistant pneumococci can result from exposure to very different agents, including narrow spectrum as well as broad spectrum agents. In vitro studies have shown a different potential for selection of resistance among the beta-lactam agents. Furthermore, several studies have more or less directly established a close relationship between the level of antibacterial use and the rate of selection of resistance. In addition to the overall amount of antibacterials prescribed in the community, several other factors have been shown to influence the rate of selection of resistance, including the use of doses that are too low, the length of therapy and the duration of bacterial exposure to long-acting agents compared to drugs with short half-lives. Therefore, there are three main ways to control selection and spread of resistant strains: by (i) reducing the amount of antibacterials used; (ii) using optimal dosages (avoiding underdosing) and treatments of short duration; and (iii) reducing the risk of transmission among young children attending daycare centres or kindergartens. In order to help physicians reduce the number of unnecessary prescriptions, it is important to develop rapid tests to recognise the bacterial origin of a febrile illness and even more important to detect resistance to antibacterials. However, apart from rapid diagnostic tests for streptococcal pharyngitis, those tests are not currently available. As a consequence, currently, the debate around narrow versus broad spectrum antibacterials remains a false debate. Physicians should use broad spectrum agents in many instances of upper or lower respiratory tract infection, taking into consideration the probable pathogens and the risk of (multi)resistance to antibacterials. Once rapid diagnostic are available in community practice, allowing a precise diagnosis of the offending agent and its susceptibility profile, physicians will be able to add to their current criteria the selective potential for resistance of the antibacterials that appear to be active in vitro.

Change of pneumococcal resistance to antibiotics in adults between 1995 and 1997: a study in eight French counties

The main object of this study was to describe the evolution of antibiotic resistance in pneumococci from adults, in eight French counties of France between 1995 and 1997. Despite the high and increasing prevalence (23-35%) of pneumococci with diminished susceptibility to penicillin G (PSDP), resistance to amoxycillin (0.8-0.5%) and to cefotaxime (0-0.3%) was rare in both 1995 and 1997 respectively. The percentage of pneumococci resistant to penicillin G (PRP, minimum inhibitory concentration >1 mg/l) remained stable between the two periods. PSDP showed increased resistance to macrolides (30-41%), to cotrimoxazole (28-34%) and to tetracycline (19-25%). These figures are lower than those obtained over the same periods and the same regions in children. The distribution of PSDP serotypes isolated in adults was the same as that seen in children: by descending order serotypes 23, 14, 9 and 6. This study by the Regional Pneumococcal Observatories confirms the high prevalence and the main characteristics of antibiotic resistance among pneumococci with variations in levels of resistance with the age of patients, with the site of sampling and from one Observatory to another.

Streptococcus pneumoniae as an agent of nosocomial infection: treatment in the era of penicillin-resistant strains

Streptococcus pneumoniae is a well-known agent of community-acquired infections such as sinusitis, otitis media, pneumonia, bacterial meningitis, bacteremia and acute exacerbations of chronic bronchitis. However, the role of S. pneumoniae as a cause of nosocomial infections of respiratory tract, bloodstream and central nervous system is more and more recognized, primarily in high-risk patients with depression of their immune function. Therapy of pneumococcal infections is made difficult by the emergence and spread of bacterial resistance to penicillin and other beta-lactams as well as to a number of antimicrobials such as macrolides, chloramphenicol, tetracyclines and sulfonamides. This epidemiological situation is a cause for concern world-wide, but it primarily affects some European countries, North America, South Africa and the Far East. The main consequence on therapeutic grounds is that in severe infections such as bacterial meningitis, the addition of vancomycin to a third-generation cephalosporin is advisable while awaiting laboratory test results, even in areas with low prevalence of penicillin-resistant pneumococci. However, a beta-lactam agent can also be a valid choice in the presence of potentially lethal infections such as pneumonia or in the case of penicillin intermediately resistant isolates. In recent years, new alternative molecules have been introduced into clinical practice for therapy of infections caused by penicillin-resistant pneumococci. In both in vivo and in vitro studies, drugs of the classes of fluoroquinolones (levofloxacin, moxifloxacin, gatifloxacin), streptogramins (quinupristin/dalfopristin) and oxazolidinones (linezolid) have shown good microbiologic and clinical efficacy against penicillin-resistant pneumococci. In this era of world-wide spread of penicillin-resistant pneumococci, use of polysaccaride or conjugated vaccines is highly recommended.

The prevalence of antibiotic resistance in bacterial respiratory pathogens from Norway is low

OBJECTIVES

To determine the degree of bacterial susceptibility to the most commonly used drugs for respiratory infections in Norway, and to find if bacterial resistance is emerging.

METHODS

Clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae and group A streptococci from respiratory tract specimens and from the eye were collected from different parts of Norway during two study periods. During the first period (1993-1994), three laboratories, covering 15% of the Norwegian population, participated. During the second study period in 1997, five laboratories, covering 27% of the population, collected respiratory isolates. In total, 494 isolates of S. pneumoniae, 696 isolates of H. influenzae and 694 isolates of group A streptococci were included in the study. The study population comprised children and adults attending hospital and general practice. Bacterial susceptibility was determined by the E test, and breakpoints were according to the National Committee for Clinical Laboratory Standards (NCCLS).

RESULTS

The prevalence of bacterial resistance was low, and we observed no significant increase in bacterial resistance between the two study periods. In 1997, only 0.6% of pneumococci had decreased susceptibility to penicillin, 1.6% of group A streptococci were resistant to erythromycin, and 6.7% of all isolates of H. influenzae produced beta-lactamase.

CONCLUSIONS

The prevalence of antibiotic resistance in respiratory pathogens in Norway is low.

Epidemiology of major respiratory pathogens

A vast literature attests to the fact that Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis represent the prevailing bacterial pathogens of community-acquired lower respiratory tract infections. Their specific incidence as causative agents of the more common syndromes is known to vary even profoundly, depending on geographic area, and the same holds true for their rates of resistance to antimicrobial drugs. Europe does not escape the threat posed by the present pandemic spread of penicillin resistance in S. pneumoniae although, as expected, some countries like Spain and France are highly affected and others including Germany, Italy, The Netherlands and the Scandinavian region, are relatively spared. In several sites multiple resistance has been described in S. pneumoniae with the most affected drugs being penicillin, the macrolides, co-trimoxazole and tetracycline. In H. influenzae synthesis of beta-lactamases is the main resistance trait expressed. Lack of susceptibility to beta-lactams dictated by a different mechanism remains extremely rare. Large variations in the incidence of this character are apparent when considering European countries. France and Spain are again widely affected while Germany, The Netherlands and Italy display rates of beta-lactamase-positive H. influenzae of about 16%. M. catarrhalis must be considered generally resistant to non-protected aminopenicillins since over 90% of these organisms produce beta-lactamases.

Two-year surveillance of antibiotic resistance in Streptococcus pneumoniae in four African cities

Worldwide spread of antibiotic resistance in Streptococcus pneumoniae is a major problem. However, data from West and North African countries are scarce. To study the level of resistance and compare the situations in different cities, a prospective study was conducted in Abidjan (Ivory Coast), Casablanca (Morocco), Dakar (Senegal), and Tunis (Tunisia), from 1996 to 1997. The resistances to eight antibiotics of 375 isolates were studied by E test, and the results were interpreted using the breakpoints recommended by the National Committee for Clinical Laboratory Standards. Overall, 30.4% of the isolates were nonsusceptible to penicillin G (25.6% were intermediate and 4.8% were resistant). Amoxicillin (96.3% were susceptible) and parenteral third-generation cephalosporins (92.7%) were highly active. Resistance to chloramphenicol was detected in 8.6% of the isolates. High levels of resistance were noted for erythromycin (28%), tetracycline (38.3%), and cotrimoxazole (36.4%). Resistance to rifampin was rare (2.1%). There were significant differences in resistance rates between individual countries. Multiple resistance was more frequent in penicillin-nonsusceptible isolates than in penicillin-susceptible isolates. Recommendations for treatment could be generated from these results in each participating country.

Antibiotic susceptibility and serotype distribution of Streptococcus pneumoniae causing meningitis in Italy, 1997-1999

Because few data are available in Italy regarding antimicrobial susceptibility and serotype distribution of invasive Streptococcus pneumoniae strains, meningeal isolates collected at Italian hospitals during the years 1997-1999 were studied. The 12 most common serogroups, representing > 85% of the isolates, were 14, 23, 6, 4, 3, 9, 19, 8, 1, 12, 18, and 7 (in order of frequency). The serogroups identified in children < 5 years old were more limited in number: 80% are included in the 7-valent conjugate vaccines. Penicillin resistance was observed in 14 (9.5%) of 148 strains and increased from 5% in the first part of the study to 13% in the last part. Only 2 strains were fully penicillin resistant, and these belonged to serotype 9V. Thirty percent of the strains, mostly belonging to serogroups 14 or 6 and carrying either the ermB or the mef genes, were resistant to erythromycin.

Genetic diversity of the tet(M) gene in tetracycline-resistant clonal lineages of Streptococcus pneumoniae

The aim of the present study was to examine the stability and evolution of tet(M)-mediated resistance to tetracyclines among members of different clonal lineages of Streptococcus pneumoniae. Thirty-two tetracycline-resistant isolates representing three national (Spanish serotype 14, Spanish serotype 15, and Polish serotype 23F) and one international (Spanish serotype 23F) multidrug-resistant epidemic clones were all found to be tet(M) positive and tet(O), tet(K), and tet(L) negative. These isolates all carried the integrase gene, int, which is associated with the Tn1545-Tn916 family of conjugative transposons. High-resolution restriction analysis of tet(M) products identified six alleles, tet(M)1 to tet(M)6: tet(M)1 to tet(M)3 and tet(M)5 in isolates of the Spanish serotype 14 clone, tet(M)4 in both the Spanish serotype 15 and 23F clones, and tet(M)6, the most divergent allele, in the Polish 23F clone. This indicates that tet(M) variation can occur at the inter- and intraclone levels in pneumococci. Two alleles of int were identified, with int1 being found in all isolates apart from members of the international Spanish 23F clone, which carried int2. Susceptibility to tetracycline, doxycycline, and minocycline was evaluated for all isolates with or without preincubation in the presence of subinhibitory concentrations of tetracyclines. Resistance to tetracyclines was found to be inducible in isolates of all clones; however, the strongest induction was observed in the Spanish serotype 15 and 23F clones carrying tet(M)4. Tetracycline was found to be the strongest inducer of resistance, and minocycline was found to be the weakest inducer of resistance.

The impact of antibiotic use on resistance development and persistence

The intense use and misuse of antibiotics are undoubtedly the major forces associated with the high numbers of resistant pathogenic and commensal bacteria worldwide. Both the volume and the way antibiotics are applied contributes to the selection of resistant strains. Still, other social, ecological and genetic factors affect a direct relationship between use and frequency of resistance. Resistant bacteria, following their emergence and evolution in the presence of antibiotics, appear to acquire a 'life of their own'. They proliferate and maintain the resistance traits even in the absence of antibiotics, thus jeopardizing the reversal of bacterial resistance by simple reduction in antibiotic use. Reversing resistance requires restoration of the former susceptible flora in people and in the environment. Copyright 2000 Harcourt Publishers Ltd.

Experimental study of the virulence of Streptococcus pneumoniae with reduced susceptibility to penicillin

Streptococcus pneumoniae is a major cause of morbidity and mortality in all age groups. In a few years, penicillin non-susceptible pneumococci (PNSP) have emerged worldwide as a new threat. In order to better understand the mechanisms behind the rapid expansion of these strains, the virulence of 10 clinical and two transformed PNSP strains were compared with the virulence of three fully susceptible strains in a mouse model of bacteremia and a rat model of acute otitis media. Serotype, antibiotic susceptibility, and to some extent also genetic profile and growth rate of the strains were investigated before inoculation. The animals were monitored for up to 7 days after challenge by clinical examinations/otomicroscopy and cultures from middle ears and blood. The results of the study demonstrated that the PNSP strains had a significantly reduced ability to persist at the infectious site, and to some extent also to induce infections, compared with fully susceptible strains. The reduction was most evident for strains isolated from sources other than blood. It is therefore possible that other factors than virulence factors are of importance for the ability of PNSP strains to expand.

Prevalence and patterns of resistance of Streptococcus pneumoniae strains isolated from carriers attending day care centers in the area of Athens

The prevalence and patterns of Streptococcus pneumoniae resistance to antibiotics was examined in 146 nasopharyngeal carrier strains obtained during April and May, 1997, from 382 healthy children attending eight day care centers (DCCs) in the area of Athens. Reduced susceptibility to at least one antibiotic was found in 32.6% as follows: penicillin 11.4% (intermediate), cefotaxime 0.8% (intermediate), trimethoprim-sulfamethoxazole 22.7%, erythromycin 13.6%, tetracycline 11.4%, chloramphenicol 8.3%. Most of the nonsusceptible to penicillin isolates belonged to serogroups 23, 9, and 19. Multidrug resistance was detected in 11.4% of S. pneumoniae isolates including five penicillin nonsusceptible serogroup 23 strains. More than half of the multidrug resistant strains were susceptible to penicillin and belonged to serogroups 6 (4), 23 (1), 19 (1), and 1(1). Strains that belonged to the same serogroup/serotype and had identical resistance patterns appeared to cluster in some DCCs. Antibiotic use in the previous month was associated with reduced susceptibility to penicillin (p = 0.007) and multidrug resistance (p = 0.012). In conclusion, a moderate prevalence of reduced susceptibility to penicillin in pneumococcal carrier strains was found in our community. Multidrug resistance was common and was often associated with susceptibility to penicillin. Several distinct patterns of resistance were observed, suggesting the spread of resistant clones to our country.

Duration of penicillin prophylaxis in sickle cell anemia: issues and controversies

Functional asplenia occurs in 94% of patients with homozygous sickle cell anemia by 5 years of age and may result in fatal septicemia due to encapsulated microorganisms such as Streptococcus pneumoniae. Penicillin prophylaxis in these patients significantly reduces the risk of septicemia; however, continuation of prophylaxis beyond 5 years of age is controversial, since the risk of developing septicemia is reduced after this age and prolonged prophylaxis may lead to emergence of penicillin resistance. Although reports of penicillin-resistant pneumococci in patients receiving penicillin prophylaxis are conflicting, the prevalence of these organisms in the general population in North America increased from 5% in 1989 to more than 35% in 1997. Discontinuation of prophylaxis after age 5 years may be recommended because of lack of benefit, difficulty maintaining compliance, reduced risk of developing pneumococcal bacteremia after that age, and increase in prevalence of penicillin-resistant pneumococci worldwide.

The microbial genetics of antibiotic cycling

Cycling of currently available antibiotics to reduce resistance is an attractive concept. For cycling strategies to be successful, their implementation must have a demonstrable impact on the prevalence of resistance determinants already dispersed throughout the hospital and associated healthcare facilities. While antibiotic use in hospitals clearly constitutes a stimulus for the emergence of resistance, it is by no means the only important factor. The incorporation of resistance determinants into potentially stable genetic structures, including bacteriophages, plasmids, transposons, and the more newly discovered movable elements termed integrons and gene cassettes, forces some degree of skepticism about the potential for such strategies in institutions where resistance determinants are already prevalent. In particular, the expanding role of integrons may pose an ultimate threat to formulary manipulations such as cycling. Despite these concerns, the crisis posed by antimicrobial resistance warrants investigation of any strategy with the potential for reducing the prevalence of resistance. Over the next decade, new studies with carefully designed outcomes should determine the utility of antibiotic cycling as one control measure for nosocomial resistance.

Antimicrobial-drug use and changes in resistance in Streptococcus pneumoniae

Resistance of Streptococcus pneumoniae to antimicrobial drugs is increasing. To investigate the relationship between antimicrobial use and susceptibility of S. pneumoniae isolates at 24 U.S. medical centers, we obtained data on outpatient antimicrobial-drug use for the regions surrounding 23 of these centers. We found an association between decreased penicillin susceptibility and use of beta-lactam antimicrobial drugs.

Correlation between consumption of antimicrobials in humans and development of resistance in bacteria

The correlation between consumption of antimicrobials in humans and the emergence of resistance in bacteria is complex and has proved difficult to establish. Besides antimicrobial use, many other distinct contributing factors are also involved in the issue. Despite this complexity, there is a substantial body of evidence that the use of antibiotics in prophylaxis and in therapy is associated with the development of resistance in the hospital and in the community. Some examples are reviewed, including increase of resistance in enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter spp., Streptococcus pneumoniae, Staphylococcus aureus, Coagulase Negative Staphylococci and Streptococcus pyogenes after the use of beta-lactam antibiotics, aminoglycosides, fluoroquinolones and macrolides. Success in reversing the rise of resistant strains has been rarely described. Two examples are highlighted, the reduction in the incidence of nasal carriage of penicillin-resistant pneumococci in Icelandic children, and a significant decline in erythromycin resistance in S. pyogenes after the reduction in the use of macrolides in Finland.

In vitro activity of quinupristin/dalfopristin against selected bacterial pathogens isolated in Italy

OBJECTIVE: To evaluate the activity of quinupristin/dalfopristin, a new injectable streptogramin, against 732 clinical strains recently isolated in Italy. METHODS: Susceptibility tests were performed according to NCCLS-guided MIC methodology. Pathogens included in the evaluation included 108 Staphylococcus aureus isolates, 124 coagulase-negative staphylococcal isolates, 158 Streptococcus pyogenes isolates, 30 Streptococcus agalactiae isolates, 30 b-hemolytic streptococcal isolates, 18 Streptococcus sanguis isolates, 80 Streptococcus pneumoniae isolates, 69 Enterococcal isolates, 40 Haemophilus influenzae isolates, 30 Moraxella catarrhalis isolates and, finally, 30 Gram-positive and 25 Gram-negative anaerobes. RESULTS: Quinupristin/dalfopristin inhibited Staphylococcus aureus and other Staphylococcus spp., irrespective of their oxacillin or erythromycin resistance phenotypes. Similarly, streptococci were fully inhibited by quinupristin/dalfopristin. Enterococcus faecalis was not included in the spectrum of this streptogramin, while isolates of Enterococcus faecium were inhibited by the new compound. Respiratory pathogens such as H. influenzae and M. catarrhalis were inhibited by quinupristin/dalfopristin as well as all Gram-negative anaerobes tested. CONCLUSIONS: These findings suggest a putative role for quinupristin/dalfopristin in the empirical treatment of severe nosocomial and community-acquired infections caused by pathogens often displaying resistance to multiple antibiotics. This drug may provide an alternative to glycopeptide compounds.

Pharmacodynamics of trovafloxacin in a mouse model of cephalosporin-resistant Streptococcus pneumoniae pneumonia

Trovafloxacin is a potentially useful agent for treatment of infections caused by cephalosporin-resistant Streptococcus pneumoniae. We studied the effectiveness of trovafloxacin therapy and examined the correlation between pharmacodynamic indices in serum and lung, and bacterial killing. Immunocompetent Balb/c mice were infected by intranasal inoculation of a cephalosporin-resistant S. pneumoniae isolate (MIC of ceftriaxone and trovafloxacin 2 and 0.06 mg/L, respectively). Trovafloxacin 10-30 mg/kg/day in one or three divided doses was started 15 h after infection. Serum and lung drug concentrations were measured at multiple time points for 24 h. Serum concentrations peaked at 30-60 min and lung concentrations approximately 30 min later. The serum T1/2 was approximately 9 h and lung T1/2 varied from 5 to 9 h. Lung AUC and Cmax values were 2-3 times greater than those in serum. At the start of therapy lung bacterial concentrations were 8.4 +/- 0.3 log10 cfu/mL and 24 h later had decreased by 3.5 +/- 0.2, 4.0 +/- 0.2, 0.8 +/- 0.3 and 1.0 +/- 1.2 log10 cfu/mL with 30 mg/kg x 1, 10 mg/kg x 3, 10 mg/kg x 1 and 3.3 mg/kg x 3 regimens, respectively. Although the larger dosages were more effective (P < 0.001) the differences between divided and single dosage regimens were not significant. Trovafloxacin serum AUC/MIC ratio correlated best with bacterial killing in the lungs over 24 h. Trovafloxacin is likely to be useful in the treatment of cephalosporin-resistant S. pneumoniae pneumonia.

Antibiotic resistance and therapeutic options in lower respiratory tract infections

The emergence of some strains of common pathogens of community acquired pneumonia resistant to one or more of the frequently used antimicrobials is becoming widespread. The clinical significance and implications of these resistance patterns are, however, unclear. Studies of the clinical progress of patients with pneumonia or bacteraemia infected with penicillin-resistant organisms show that patients frequently recover when treated with penicillins or cephalosporins. Beta-Lactam drugs and macrolides are still associated with clinical success in lower respiratory tract infections despite increasing resistance to these agents in vitro. Therefore, when making therapeutic choices, in vitro resistance data cannot always be used to predict clinical outcome. Infections caused by resistant organisms can usually be successfully treated using traditional therapeutic approaches.

Incidence of antibiotic resistance in blood and urine isolates from hospitalized patients. Report from a European collaborative study. European Study Group on Antibiotic Resistance (ESGAR)

During 1992-93, 2544 isolates from blood cultures, comprising 52% gram-negative bacilli, 24% Staphylococcus aureus, 15% other staphylococci, 7% Enterococcus faecalis and 2% E. faecium, were consecutively collected and identified in 30 laboratories in 21 European countries. In addition 2512 urine isolates, comprising 82% gram-negative bacilli, 3% S. aureus, 4% other staphylococci and 11% enterococci were collected. The bacteria were sent to 3 laboratories for susceptibility testing by the microdilution method in Mueller-Hinton broth. The MICs of penicillins and aztreonam for all susceptible gram-negative bacilli were 0.25-8 mg/l, penems 0.032-2 mg/l, cefotaxime, ceftazidime and cefpirome or cefepime 0.032-0.25 mg/l, gentamicin, tobramycin and netilmicin 0.125-2 mg/l, amikacin 0.5-4 mg/l, ciprofloxacin 0.016-1 mg/l, trimethoprim 0.25-1 mg/l and tetracycline 1-2 mg/l. For susceptible staphylococci the MICs of erythromycin were 0.25-0.5 mg/l, clindamycin 0.125-0.25 mg/l, methicillin 2-8 mg/l, vancomycin and trimethoprim 1-4 mg/l, ciprofloxacin 0.25-1 mg/l, gentamicin and tobramycin 0.25-1 mg/l. For the enterococci the MICs of ampicillin and vancomycin were 2-4 mg/l and of imipenem, teicoplanin and trimethoprim 0.5-1 mg/l. The antibiotic resistance rates varied between laboratories, being lower in northern Europe, except for the penems, cefpirome and cefepime, which showed uniformly lower resistance rates. Compared to the earlier European studies the resistance rates to beta-lactam antibiotics among the gram-negatives have not changed except with an increase to cefotaxime and ceftazidime in central Europe. Resistance to aminoglycosides had also increased in central Europe from 7-8% to 20-21%, but decreased in southern Europe from 22-24% to 13-14% among the blood isolates and from 12-28% to 6-7% among the urine isolates. There was an increase in resistance to ciprofloxacin and gentamicin in staphylococci from southern Europe. The prevalence of MRSA was significant in central and southern Europe. It is of importance that collaborative national and international studies on the incidence of antibiotic resistance are being performed on a repetitive basis.