Levels Of Penicillin Resistance Research Articles

Synergistic Killing of Streptococcus pneumoniae with the Bacteriophage Lytic Enzyme Cpl-1 and Penicillin or Gentamicin Depends on the Level of Penicillin Resistance

A combination of Cpl-1, a bacteriophage lytic enzyme, and penicillin, gentamicin, levofloxacin, or azithromycin was tested against Streptococcus pneumoniae strains with various susceptibilities to penicillin. Activities of Cpl-1 and gentamicin were increasingly synergistic with a decreasing penicillin MIC, while Cpl-1 and penicillin showed synergy against an extremely penicillin-resistant strain.

Reduced susceptibility to penicillin of viridans group streptococci in the oral cavity of patients with haematological disease

The occurrence of oral penicillin-resistant viridans group streptococci (VGS) was studied in 50 patients with either newly diagnosed acute leukaemia or autologous peripheral stem cell transplants. One patient was excluded because of Staphylococcus aureus growth in the stem cell harvest. VGS were isolated from the oral cavity of 48 of the remaining 49 patients. Of these 48 patients, 12 (25%) yielded VGS resistant (MIC > 2 mg/L) to penicillin. These 12 patients had a higher frequency of septicaemia (p 0.04) and more days of treatment with trimethoprim-sulphamethoxazole (p 0.04) than patients who harboured susceptible or intermediately resistant VGS (MIC 2 mg/L). There were no other statistically significant differences between the two groups. It is important to be aware of the high level of penicillin resistance in oral VGS in patients with haematological disease, and this parameter should be considered when selecting antibiotic therapy for cases of septicaemia caused by VGS in immunocompromised patients.

Increasing antibiotic resistance of streptococcus species in New York City.

Streptococcus species are common pathogens in head and neck infections and are leading causes of morbidity and mortality. Emerging penicillin-resistant streptococcal pathogens have shifted empirical antibiotic therapy in favor of valuable alternatives, including erythromycin and clindamycin. This study was undertaken to determine the magnitude of antimicrobial resistance to these antibiotics. Retrospective review. A retrospective study of two streptococcal species isolates, Streptococcus pyogenes (163 specimens) and Streptococcus pneumoniae (164 specimens), collected between January 1, 2001 and January 1, 2002 at two academic institutions. The antibiotic susceptibility patterns were analyzed for penicillin, erythromycin, and clindamycin according to the National Committee for Clinical Laboratory Standards. Fourteen percent to 34% of S. pyogenes isolates were erythromycin-resistant, and 0% to 28% were clindamycin-resistant. None of the S. pyogenes isolates were resistant to penicillin. Of the S. pneumoniae isolates, 33% to 50% were resistant to erythromycin, and 18% to 33% were resistant to clindamycin. The penicillin resistance levels for S. pneumoniae were 0% to 45%. Our antimicrobial resistance levels for S. pyogenes and S. pneumoniae significantly exceeded national and worldwide levels of erythromycin and clindamycin resistance. With a diverse population of over 8 million residents and high physician supply, our model is a microcosm for the study of antimicrobial use and susceptibility patterns and of clinical failure.

Nasopharyngeal carriage and susceptibility patterns of Streptococcu Pneumoniae in Kumasi, Ghana

Penicillin resistant Streptococcus pneunmoniae poses an increasing problem in paediatrics, particularly in less developed countries. Outside of South Africa, little is known about S. pneumoniae susceptibilities in Sub-Saharan Africa. The objective of this study was to determine the prevalence of pneumococcal colonization and antimicrobial susceptibility among children in urban Ghana. Nasopharyngeal pneumococcal colonization was examined in 311 children attending a polyclinic for sick children and an immunization clinic in Kumasi, Ghana. Isolates were tested for antibiotic susceptibility to penicillin, tetracycline, erythromycin, chloramphenicol, cefuroxime, cefotaxime, ceftriaxone, and trimethoprim-sulfamethoxazole. Over half (51.4%) of subjects were colonized with S. pneumoniae and 17% of isolates were resistant to penicillin, all demonstrating intermediate resistance. S. pneumoniae strains were also frequently resistant to trimethoprim-sulfamethoxazole and tetracycline, less so to chloramphenicol and cefuroxime and were almost uniformly sensitive to cefotaxime, cefriaxone and erythromycin. Our study shows a high rate of pneumococcal nasopharyngeal colonization and a concerning level of penicillin resistance although at a less alarming rate than seen in some other countries. Multiple antimicrobial resistance was also noted especially among drugs readily available and commonly used. These data impact treatment choices in pneumococcal disease. Vaccine may play an important role in disease limitation. An effort to curtail the misuse of antibiotics, by prescription and otherwise, may prevent further increases in resistance rates.

Epidemiology of invasive Streptococcus pneumoniae infections in children in an area of Barcelona, Spain.

Streptococcus pneumoniae is the most common cause of bacteraemia, pneumonia, sinusitis and acute otitis media. With the advent of conjugate vaccines, there is now the possibility of preventing disease caused by this organism. However, little is known about the epidemiology of invasive pneumococcal disease in children in Spain. The aim of this study was to determine the incidence and the clinical and microbiologic characteristics of invasive pneumococcal disease in Sabadell, an industrial area in the province of Barcelona, Spain. From January 1990 to December 2000, the case records of children with pneumococcal invasive disease at Sabadell Hospital were retrospectively (1990-1996) reviewed and prospectively (1997-2000) collected. The hospital serves a population of 61,143 children under 15 y of age, 18,073 children under 4 y of age and 7300 children under 2 y of age. A total of 112 children (54% under 24 mo of age and 93% under 6 y of age) with invasive pneumococcal disease were diagnosed during a period of 11 y. The incidence of invasive pneumococcal disease was 76 per 100,000 for children aged 0 to 24 mo, 45 for children aged 0-48 mo and 16.6 for children aged 0-14 y. Occult bacteraemia was the most common manifestation of invasive pneumococcal disease (66 cases), pneumonia was the second form (34 cases) and meningitis (10 cases) and arthritis (2 cases) were the other clinical manifestations. Of the 105 strains tested, 8.6% were highly penicillin resistant, 37.1% were intermediately penicillin resistant. 16.2% were intermediately cefotaxime resistant and 32.4% were erythromycin resistant. Pneumococci of serogroups 6, 14, 18, 19, 1, 5, 4, 9, 23 and 33 were the most frequently isolated groups (92%) but only 6, 9, 14, 19 and 23 were resistant to penicillin, cefotaxime, or erythromycin. In this study the incidence of invasive pneumococcal disease was found to be greater than that reported elsewhere in Spain and Europe. Penicillin resistance levels are high but the trend towards increasing penicillin resistance may have ended over the past few years. The currently licensed seven-valent (7-V) pneumococcal conjugate vaccine would cover 78% of cases of invasive pneumococcal in children aged 0-14 y, 80% in children aged 0-24 mo and 100% of cases of penicillin- or cefotaxime-resistant invasive pneumococcal disease.

Epidemiology of invasive Streptococcus pneumoniae infections in children in an area of Barcelona, Spain

Aim: Streptococcus pneumoniae is the most common cause of bacteraemia, pneumonia, sinusitis and acute otitis media. With the advent of conjugate vaccines, there is now the possibility of preventing disease caused by this organism. However, little is known about the epidemiology of invasive pneumococcal disease in children in Spain. The aim of this study was to determine the incidence and the clinical and microbiologic characteristics of invasive pneumococcal disease in Sabadell, an industrial area in the province of Barcelona, Spain. Methods: From January 1990 to December 2000, the case records of children with pneumococcal invasive disease at Sabadell Hospital were retrospectively (1990–1996) reviewed and prospectively (1997–2000) collected. The hospital serves a population of 61 143 children under 15 y of age, 18 073 children under 4y of age and 7300 children under 2 y of age. Results: A total of 112 children (54% under 24 mo of age and 93% under 6 y of age) with invasive pneumococcal disease were diagnosed during a period of 11 y. The incidence of invasive pneumococcal disease was 76 per 100000 for children aged 0 to 24 mo, 45 for children aged 0–48 mo and 16.6 for children aged 0‐14 y. Occult bacteraemia was the most common manifestation of invasive pneumococcal disease (66 cases), pneumonia was the second form (34 cases) and meningitis (10 cases) and arthritis (2 cases) were the other clinical manifestations. Of the 105 strains tested, 8.6% were highly penicillin resistant, 37.1% were intermediately penicillin resistant, 16.2% were intermediately cefotaxime resistant and 32.4% were erythromycin resistant. Pneumococci of serogroups 6, 14, 18, 19, 1, 5, 4, 9, 23 and 33 were the most frequently isolated groups (92%) but only 6, 9, 14, 19 and 23 were resistant to penicillin, cefotaxime, or erythromycin. Conclusions. In this study the incidence of invasive pneumococcal disease was found to be greater than that reported elsewhere in Spain and Europe. Penicillin resistance levels are high but the trend towards increasing penicillin resistance may have ended over the past few years. The currently licensed seven‐valent (7‐V) pneumococcal conjugate vaccine would cover 78% of cases of invasive pneumococcal in children aged 0–14 y, 80% in children aged 0–24 mo and 100% of cases of penicillin‐ or cefotaxime‐resistant invasive pneumococcal disease.

Childhood invasive pneumococcal disease in Tasmania, 1994-2000.

To describe the burden of invasive pneumococcal disease in Tasmanian children, including age-specific incidence and antibiotic-resistance pattern. A population-based retrospective study was carried out, examining cases of childhood disease associated with isolates of Streptococcus pneumoniae from normally sterile sites, identified via scrutiny of laboratory records at all major Tasmanian laboratories during a 7-year period between January 1994 and December 2000. Medical records were sub-sequently examined for information describing the clinical syndrome and course of disease. Invasive pneumococcal disease was identified in 76 children during the 7-year period. The incidence per 100 000 children was 28.5 (95% CI 22.0-36.3) in children under 5 years and 54.3 (95% CI 40.2-71.8) in children under 2 years. The incidence of meningitis in children younger than 2 years was 12.2 (95% CI 6.1-21.8). Penicillin resistance was observed in 2.6% of cases, with no high level resistance. Predisposing conditions were identified in 34% of children with invasive disease. The incidence of invasive pneumococcal disease was comparable to many urban populations in Australia. The high rate of predisposing conditions supports the recommendations of the Australian Technical Advisory Group on Immunisation for targeted immunization in this group. The paucity of data describing Indigenous status is an argument for improved data collection in this area. The low level of penicillin resistance necessitates ongoing surveillance, and the lack of serotype information requires prospective data collection.

Analysis of penicillin-binding protein genes of clinical isolates of Streptococcus pneumoniae with reduced susceptibility to amoxicillin.

The recent emergence of pneumococcal isolates exhibiting an unusual resistance phenotype of higher amoxicillin MICs in relation to the penicillin MICs prompted an analysis of the pbp genes from three such strains isolated in France. For comparison, three amoxicillin-susceptible strains were included in the study. DNA sequence analysis of the pbp2x, pbp2b, and pbp1a genes revealed extensive sequence divergence in all six isolates compared to the sequences of the genes of penicillin-susceptible strain R6. With the exception of pbp2b, no amino acid mutations were unique to the resistant isolates. Transformation experiments with cloned pbp genes isolated from one of the resistant isolates demonstrated a stepwise development of amoxicillin resistance involving penicillin-binding proteins (PBPs) 2X, 2B, and 1A. Full resistance, equivalent to that of the donor strain, was achieved only when genomic DNA was transformed into R6(2x/2b/1a) mutants, suggesting that full resistance development in this isolate is mediated by a non-PBP determinant. Moreover, the recently identified murMN resistance determinant does not appear to have any impact on resistance in this isolate. This determinant (from the French isolate) was, however, able to transform an R6 mutant harboring pbp2x, pbp2b, and pbp1a genes from a Hungarian clone with an extremely high level of penicillin resistance so that it had increased levels of penicillin resistance. These results indicate that the development of high-level beta-lactam resistance is a complex process and that the involvement of MurMN in penicillin resistance appears to be dependent on specific mutations in PBPs 2X, 2B, and/or 1A. Furthermore, an additional (as yet unidentified) non-PBP-mediated resistance determinant is required for full resistance development in some pneumococci.

The murMN operon: a functional link between antibiotic resistance and antibiotic tolerance in Streptococcuspneumoniae.

Inactivation of the recently identified murMN operon in penicillin-resistant strains of Streptococcus pneumoniae was shown already to cause two major effects: elimination of branched-structured muropeptides from the cell wall and complete loss of penicillin resistance. We now show that cells with inactivated murMN also have a third phenotype: an increased susceptibility to lysis when exposed to low concentrations of fosfomycin, d-cycloserine, vancomycin, and nisin, indicating a wide-spectrum hypersensitivity to inhibitors of both early and late stages of cell wall biosynthesis. Mutants of murMN also lysed faster than the parental strain when treated with the detergent deoxycholate. Several different alleles of murM cloned in plasmid pLS578 and introduced into a murM deletion mutant of the penicillin-resistant strain Pen6 were able to reconstitute each one of the three mutant phenotypes: the highly branched cell wall structure, original high level of penicillin resistance, and normal sensitivity to lysis. In a penicillin-susceptible strain the same experiments caused increased concentration of cell wall branched peptides and suppression of sensitivity to antibiotic induced lysis. The observations suggest that the murMN operon plays a key role in the regulation of a stress-response pathway that can be triggered by perturbation of cell wall biosynthesis in S. pneumoniae.

Is antimicrobial resistance also subject to globalization?

In recent years one of the more alarming aspects of clinical microbiology has been the dramatic increase in the incidence of resistance to antibacterial agents among pathogens causing nosocomial as well as community-acquired infections. There are profound geographic differences in the incidence of resistance among pathogens of the respiratory tract, only some of which can be explained by the local use of antibiotics. A high percentage of Moraxella catarrhalis strains produce beta-lactamase and are thus resistant to many beta-lactam antibiotics. In contrast, beta-lactamase production among strains of Haemophilus influenzae rarely reaches more than 30% around the world. Methicillin-resistance in Staphylococcus aureus is a common and increasing problem in hospitals but its extent varies both locally and nationally. Resistance is usually associated with the local spread of resistant strains. High standards of hygiene in hospitals can prevent the spread of such strains but once established they can be difficult to eradicate. Although Streptococcus pyogenes remains highly susceptible to penicillins, even after many decades of their use, resistance to macrolides has occurred. This resistance can rise and fall. Although the increase of macrolide resistance in S. pyogenes can often be associated with an increase in the use of these drugs, this is not always so. In some cases it has been shown to be caused by the spread of one or more resistant clones. Eradication of these clones can reduce the level of resistance markedly. Resistance to both macrolides and penicillins among strains of Streptococcus pneumoniae is seen world-wide but is highly variable from country to country. Local habits of drug usage may play a part. In Italy, for example, there is preference for the use of parenteral third-generation cephalosporins for some severe infections and there is a corresponding low level of penicillin-resistance among pneumococci.

The role of murMN operon in penicillin resistance and antibiotic tolerance of Streptococcus pneumoniae.

The recently identified murMN operon is essential for the production of branched-structured muropeptides in the cell wall and also for the expression of the resistant phenotype in penicillin-resistant strains of Streptococcus pneumoniae. The purpose of studies described in this communication was to understand better the role of murMN in penicillin resistance. Deletion of murM in the penicillin-resistant strain Pen6, which causes reduction in the penicillin MIC from 6.0 to 0.03 microg/ml, was successfully complemented to recover the original high level of penicillin resistance in transformants that received functional murM alleles cloned in plasmid pLS578. Inactivation of penicillin resistance was not accompanied by any detectable change in the low affinity or abnormal molecular size pattern of the penicillin-binding proteins (PBPs) nor in the mosaic sequence of PBP2X typical of resistant strain Pen6. Exposure of strain Pen6 with inactivated murM to 0.05 microg/ml of penicillin (i.e., a concentration more than 100 times below the MIC of the parental strain) initiated a phenotypic response typical of penicillin-susceptible strains of pneumococci: inhibition of growth followed by rapid and extensive loss of viability and lysis. Unexpectedly, inactivation of murMN also caused hypersensitivity to lysis by low concentrations of a variety of cell wall active antibiotics such as fosfomycin, D-cycloserine, and nisin, suggesting that the murMN operon may perform an important regulatory role in the control of the irreversible antimicrobial effects of cell wall inhibitors.

Alterations to penicillin-binding proteins 1A, 2B and 2X amongst penicillin-resistant clinical isolates of Streptococcus pneumoniae serotype 23F from the nasopharyngeal flora of children.

Various amino acid substitutions were identified in the three major penicillin-binding proteins (PBP1A, PBP2B and PBP2X) of eight clinical isolates of Streptococcus pneumoniae serotype 23F collected from children. The particular changes related to the level of penicillin resistance. Alterations were detected in an isolate with a penicillin MIC as low as 0.06 mg/L. These results confirm that the level of penicillin resistance in pneumococci reflects with sequential alterations of PBPs in clinical isolates.

Mechanisms other than penicillin-binding protein-2 alterations may contribute to moderate penicillin resistance in Neisseria meningitidis

Penicillin resistance in Neisseria spp is thought to be generated by the interspecies transfer of genetic material from naturally penicillin-resistant, commensal species. We examined a series of successive transformants with increasing levels of penicillin resistance, obtained by co-cultivation of Neisseria meningitidis derivatives with Neisseria polysaccharea. Our results suggest that, in addition to the well-known decrease in penicillin affinity of penicillin-binding protein-2 (PBP-2), decreased expression of the class 3 porin as well as decreased affinity of PBP-1 may contribute to higher level resistance of N. meningitidis to penicillin G and other β-lactam compounds.

Antimicrobial resistance and serotype distribution of Streptococcus pneumoniae isolates from Crete, Greece

Susceptibility to 14 antibiotics was determined for 125 clinical isolates of Streptococcus pneumoniae collected over a 3-year period in Crete, Greece. Twenty-three isolates (18.4%) showed intermediate resistance and 15 (12%) high-level resistance to penicillin. Erythromycin, chloramphenicol, tetracycline, trimethoprim-sulphamethoxazole and sparfloxacin resistance rates were 16.8, 10.4, 19.2, 24.8 and 9.6%, respectively. Multiple resistance was observed in 22 strains. Vancomycin and levofloxacin were the most active agents tested. The most prevalent serotype among penicillin-susceptible pneumococci was 14, followed by 9, 7 and 1, while among penicillin-intermediate or -resistant strains serotype 23 was predominant followed by 19 and 9. These results show that as well as a high level of penicillin resistance in this region, some strains are also resistant to other antibiotics and may show multi-drug resistance.

Changes in the resistance patterns among upper respiratory tract infection pathogens

The evolution of antibacterial resistance in human pathogenic and commensal micro-organisms is the result of the interaction between the antibiotic exposure and the transmission of resistance among micro-organisms, but also depends on the environment and the social habits of individuals. Antibiotic use and bacterial resistance are, therefore, a public health problem subjected to discussion not only in the scientific community, but also having a strong impact in the public media. Among bacterial diseases, respiratory tract infections are a group of diseases ranging from pharyngitis and otitis media to acute bronchitis and to pneumonia. As a group, respiratory infections are the most common diseases and associated with considerable burden, both for the patient and the healthcare system. In most cases, treatment is started before the results of sensitivity testing are known. Empiric therapy is guided by the patient’s symptoms and the clinician’s experience. Resistance to antibiotics is an increasing problem in community-acquired respiratory pathogens such as Streptococcus pneumoniae, Haemophilus influenzae, Haemophilus parainfluenzae, and Moraxella catarrhalis. Although there are important geographical differences between cities and countries, this problem should be addressed by continuous epidemiological surveillance and by studies to understand the molecular mechanisms of resistance both at the biochemical and genetic level. It is vital that physicians make the therapeutic choice based on this kind of information for bacteria eradication and clinical cure. The Alexander Project is an ongoing, international multicentre study investigating antimicrobial susceptibility patterns in common respiratory pathogens, both in the USA and Europe [1]. The incidence of b-lactamase positive H. influenzae was 30.1% in the USA and 15.5% in Europe, and the incidence of b-lactamase positive M. catarrhalis was up to \90% in Europe and the USA. The incidence of penicillin-resistance in S. pneumoniae is higher in Europe (24.9%) than in the USA (12.3%); the geographical distribution of this resistance varies: ie. in France and Spain it is about 40%. For the majority of centres included in the study, there is a marked association between penicillin and macrolide resistance in S. pneumoniae, with MICs for erythromycin \32 mg/l in penicillin-resistant strains. Cross-resistance was seen also for cotrimoxazole, chloramphenicol and tetracycline [2]. A 3-year systematic Italian survey program for monitoring the resistance of the most common respiratory pathogens, The Italian Epidemiological Observatory, was instituted in Italy. The aims of the study were to obtain national and regional data on the distribution of resistance and support for general practitioners for empiric therapy using these data [3]. In Italy S. pneumoniae shows an overall level of intermediate-resistance (reduced susceptibility) and resistance to penicillin of 13% with a geographical variation ranging from 10% in the north, to 26% in the south. The level of penicillinresistant strains (MIC \4 mg/l) was 4%. In this study macrolide resistance in S. pneumoniae ranged from 29% to 31%, clearly exceeding the level of penicillin resistance. Ten to thirteen percent of pneumococcal strains showed co-resistance to penicillin, erythromycin and cotrimoxazole; about 6% were also resistant to tetracycline. The percentage of b-lactamase production in H. influenzae and H. parainfluenzae was 12.2 and 13% respectively, while in M. catarrhalis it was 84.5%. The incidence of b-lactamase positive Haemophilus spp. and M. catarrhalis, the resistance to penicillin by means of an altered penicillin-binding-protein in S. pneumoniae, and the increased level of macrolide resistance, reduce the choice of oral antibiotics currently used in the treatment of acute respiratory tract infec* Tel.: +39-095-311352; fax: +39-095-325032. E-mail address: stefanis@mbox.unict.it (S. Stefani).

Impact of Streptococcus pneumoniae on pneumonia in Latin American children. SIREVA-Vigía Group

Community-acquired pneumonia is one of the leading causes of infant morbidity and mortality. Studies conducted in developing countries indicate that the most serious symptoms of pneumonia are associated with bacterial causes, mainly Streptococcus pneumoniae, followed by Haemophilus influenzae type b. Managing those infections in children under two years of age is hindered by the lack of appropriate vaccines and by the decreased susceptibility of S. pneumoniae to penicillin and other antibiotics. In 1993, at the initiative of the Regional System for Vaccines of the Pan American Health Organization, and with funding from the Canadian International Development Agency, a study was designed to identify the S. pneumoniae capsular types that cause invasive disease in Latin American children under 5 years of age. The objective of the study was to determine the ideal composition of a conjugate vaccine that could be used in Latin America, and the penicillin susceptibility of the S. pneumoniae isolates. The initiative was undertaken in Argentina, Brazil, Chile, Colombia, Mexico, and Uruguay. This report analyzes the information that the participating countries generated on pneumococcal pneumonia. A total of 3,393 children were found with systemic S. pneumoniae infections, of which 1,578 corresponded to pneumonias. The analysis focused on 1,409 cases of pneumonia in Argentina, Brazil, Colombia, Mexico, and Uruguay. Of the children, 63.8% of them were under two years of age. Twelve prevalent capsular types were identified, of which serotypes 14, 5, and 1 were the three most common in the majority of the countries. At the beginning of the study the highest level of penicillin resistance was found in Mexico (47.0%), and the lowest in Colombia (12.1%). Over the 1993-1998 period, resistance to penicillin increased in the five countries. Penicillin resistance was associated with a small number of capsular serotypes, mainly 14 and 23F. The first of those serotypes was resistant to penicillin and to trimethoprim-sulfamethoxazole, and the second was multiresistant. The frequency of resistance to trimethoprim-sulfamethoxazole was high in all of the countries; Argentina had the highest level, 58.0%. A decrease in susceptibility to chloramphenicol was uncommon, except in Colombia, where there was a resistance level of 23.4%. Resistance to erythromycin was low in all the countries, and all the isolates were susceptible to vancomycin.

Analysis of penicillin-binding protein lb and 2a genes from Streptococcus pneumoniae.

Fifty clinical isolates (penicillin MICs, 0.03-8 microg/mL) of Streptococcus pneumoniae were randomly selected from hospitals throughout South Africa, together with seven strains isolated in Hungary (penicillin MICs, 16-32 microg/mL). Penicillin-binding protein (pbp) 1b and 2a genes were amplified by PCR, and the purified DNA was digested with HinfI, StyI, and MseI + DdeI restriction enzymes. The fragments were radioactively end-labeled and separated on polyacrylamide gels, and the DNA fingerprints were visualized following autoradiography. A collection of isolates was further selected for sequence analysis of pbp1b and 2a. DNA fingerprint analysis revealed a uniform profile amongst all isolates for both genes. All isolates revealed a maximum of only seven nucleotide substitutions in their pbp1b genes, resulting in a maximum of three amino acid substitutions in PBP 1B. In the case of the pbp2a gene, up to 13 nucleotide substitutions were observed randomly distributed amongst penicillin-susceptible and resistant isolates, revealing a maximum of five amino acid substitutions in PBP 2A. No amino acid substitutions were found to be common amongst all penicillin-resistant isolates. Transformation experiments with pbp1b and 2a genes isolated from two resistant strains (MICs, 4 and 16 microg/mL) failed to transform pneumococcal strains to increased levels of penicillin resistance. These results show that the pbp1b and 2a genes examined here do not display the typical mosaic gene patterns observed in the pbp2x, 2b, and 1a genes of penicillin-resistant pneumococci. In addition, the transformation studies suggest that PBPs 1B and 2A may not play a role in the development of penicillin resistance in some pneumococci.

Trend of antimicrobial resistance in Neisseria gonorrhoeae at New Delhi, India.

We aim to monitor the trends of antimicrobial resistance in Neisseria gonorrhoeae and to compare the results of antimicrobial sensitivity by disc diffusion and minimum inhibitory concentration (MIC). Two hundred and eleven confirmed strains of N. gonorrhoeae were subjected to antimicrobial sensitivity testing by disc diffusion using penicillin, tetracycline, ciprofloxacin and ceftriaxone from 1995 to June 1999. Penicillinase-producing Neisseria gonorrhoeae (PPNG) were detected by lodometric method. Minimum inhibitory concentration was determined by E test. A low level of penicillin resistance and PPNG detected in 1996 was maintained over the years. Significant increasing trend of tetracycline and ciprofloxacin resistance with high MIC i.e. 2-96 microg/ml and 1-32 microg/ml respectively were found. Ceftriaxone was found to be the drug of choice, being 100% sensitive. Comparison of resistance pattern by the 2 tests showed satisfactory agreement. Emergence of penicillin, quinolone and tetracyline resistance in N. gonorrhoeae isolates from a major STD centre at New Delhi indicates the need for increased awareness, prudent use of antimicrobials, and evaluation of new antimicrobials for the treatment of gonorrhoea.

Penicillin-resistant pneumococci in southern Sweden, 1993-1997.

In Malmöhus County, Southern Sweden, the frequency of penicillin-resistant pneumococci in nasopharyngeal specimens of outpatients with respiratory tract infections increased from 3.1% in 1993 to 7.6% in 1995, and was thereafter rather stable. Over the period, 82-85% of the patients with penicillin-resistant strains were children 0-6 years of age. Ten groups/types constituted 96-100% of the penicillin-resistant isolates. Grouping/typing of 200 consecutive isolates in October and November each year indicated that the distribution of groups/types amongst patients with respiratory tract infections was rather constant over the period. The frequency of penicillin-resistant pneumococci of groups/types 6, 14, and 19 roughly corresponded to the occurrence of these groups/types amongst the consecutive isolates. Other groups/types 9, 15, 21, and 23 either showed a pronounced increase or decrease, which could not be related to the prevalence of these groups/types among the consecutive isolates or degree of antibiotic resistance. Penicillin-resistant group 9, introduced in the area in 1993, consisted of one single clone, 9V. The stabilized level of penicillin resistance since 1995 may be related to the preventive measures implemented in the area, including day-care interventions, and measures to reduce the prescription rate of antibiotics to outpatients with respiratory tract infections.

Evolving Resistance Patterns of Streptococcus pneumoniae: A Link with Long-Acting Macrolide Consumption?

The Alexander Project indicates an increase in the prevalence of S. pneumoniae resistance to macrolide antibiotics. In some centers, the prevalence of S. pneumoniae macrolide resistance exceeds that of penicillin resistance. Centers with a high level of macrolide resistance tend to also have high levels of penicillin resistance. Antimicrobial use may be an important driver of resistance. The application of pharmacodynamic concepts suggests that bacterial exposure to low and prolonged concentrations of macrolides may have a role in the selection of resistance. Analysis of macrolide prescribing and resistance patterns indicates a correlation between increasing macrolide resistance and the increased use of newer, long-acting macrolides, although further study is required to investigate the causality of this correlation. In order to attempt to prevent the further spread of resistance, antibiotic choice should maximize the opportunity for bacterial eradication.