Changing antimicrobial susceptibility patterns among Streptococcus pneumoniae and Haemophilus influenzae from Brazil: Report from the SENTRY Antimicrobial Surveillance Program (1998-2004)

Although antimicrobial resistance rates among Streptococcus pneumoniae and Haemophilus influenzae have increased significantly in most countries in the last years, most studies from Brazil report relatively low resistance rates among these pathogens. In this study, we analyzed the susceptibility patterns of S. pneumoniae and H. influenzae from Brazil during a 7-year period. A total of 829 S. pneumoniae and 718 H. influenzae consecutively collected from 1998 to 2004, mainly from respiratory tract and bloodstream infections, were susceptibility tested by broth microdilution methods against >30 drugs and the results were analyzed by year. Overall, 77.8% of S. pneumoniae strains were considered susceptible (MIC, < or =0.06 microg/ml) to penicillin. Resistance to penicillin (MIC, > or =2 microg/ml) and ceftriaxone (MIC, > or =4 microg/ml) were detected in 7.5 and 0.5% of strains, respectively. The fluoroquinolones, levofloxacin (MIC90) 1 microg/ml) and gatifloxacin (MIC90, 0.5 microg/ml), were active against 99.8% of the isolates tested. Among the other non-beta-lactam drugs tested, the rank order of susceptibility rates was chloramphenicol (98.9%) > clindamycin (96.4%) > erythromycin (90.6%) > tetracycline (69.8%) > trimethoprim/sulfamethoxazole (36.7%). Resistance to penicillin has increased markedly among S. pneumoniae isolates over 7 years (from 2.9 to 11.0%). Additionally, resistance rates against erythromycin, clindamycin, and tetracycline decreased among pneumococcal strains during the same period. S. pneumoniae recovered from pediatric patients (< or =5 years) showed increased penicillin and trimethoprim/sulfametroxazole resistance rates compared to older populations. The rate of ampicillin resistance among H. influenzae was 14.0%, which also corresponds with the beta -lactamase production rate. All H. influenzae isolates were susceptible to amoxicillin/clavulanate (MIC90, 1 microg/ml), ceftriaxone (MIC90, < or =0.008 microg/ml), cefepime (MIC90, 0.12 microg/ml), ciprofloxacin (MIC90, < or = 0.12microg/ml), levofloxacin (MIC90, < or =0.5 microg/ml), and gatifloxacin (MIC90, < or =0.03 microg/ml). Resistance to the antimicrobials tested remained very stable among H. influenzae isolates during the 7-year study period. The continued emerging antimicrobial resistances found in these pathogens (mainly S. pneumoniae) highlight the need for alternative agents for the treatment of infections caused by these species.     

Resistance patterns of selected respiratory tract pathogens in Poland

This study presents the results of a survey of the in-vitro susceptibility to antimicrobial agents of major pathogens responsible for community-acquired respiratory tract infections in Poland during 2002-2004. The collection of 1184 bacterial isolates comprised 398 Streptococcus pneumoniae, 344 Haemophilus influenzae, 302 Streptococcus pyogenes and 140 Moraxella catarrhalis. Among the pneumococcal isolates, 16.8% were penicillin-non-susceptible (PNSP), of which 80.6% were identified as multidrug-resistant. Overall, 9.0% of H. influenzae isolates were beta-lactamase-positive, although this percentage increased noticeably in the third year of the study. Based on PCR results, 12.8% of H. influenzae isolates were identified as low-level beta-lactamase-negative, ampicillin-resistant (BLNAR), and one isolate as low-level beta-lactamase-positive, amoxycillin-clavulanic acid-resistant (BLPACR). Pulsed-field gel electrophoresis (PFGE) classified 45 H. influenzae isolates with altered penicillin-binding proteins into 15 PFGE types, including two predominant types (with four and six sub-types) containing 15 and ten isolates, respectively. Resistance to tetracycline, erythromycin and clindamycin was found in 20.9%, 8.9% and 4.6% of S. pyogenes isolates, respectively. The production of beta-lactamase characterised 91.4% of M. catarrhalis isolates. In summary, the overall occurrence of PNSP in Poland remains stable, although there was a noticeable increase in the proportion of fully-resistant isolates. A rising trend in the prevalence of beta-lactamase producers and low-level BLNAR isolates was observed among Polish isolates of H. influenzae.     

Increased prevalence of erythromycin resistance in streptococci: substantial upsurge in erythromycin-resistant M phenotype in Streptococcus pyogenes (1979-1998) but not in Streptococcus pneumoniae (1985-1999) in Taiwan

A total of 394 nonduplicate isolates of Streptococcus pyogenes collected from 1979 to 1998 and 267 nonduplicate isolates of Streptococcus pneumoniae collected from October, 1998, to May, 1999, in Taiwan were evaluated. Among the 220 erythromycin-resistant (MIC, > or =1 microg/ml) S. pyogenes isolates, 35% had an M phenotype and 65% had an ML phenotype (inducible resistance [iML], 0.5%, and constitutive resistance [cML], 64.5%). Among the 243 erythromycin-resistant S. pneumoniae isolates, the majority (65.4%) had an ML phenotype (iML, 0.4%, and cML, 65%) and 34.6% had an M phenotype. A substantial upsurge in the incidence of M-phenotype erythromycin-resistant isolates was found with time for S. pyogenes (0% in 1979-1984 and 100% in 1997-1998), and an increasing incidence of M-phenotype among erythromycin-resistant S. pneumoniae was also noted (<20% before 1994 and 45.4% in 1999). All S. pyogenes and all but four S. pneumoniae isolates exhibiting a cML or iML phenotype had harbored the ermAM gene. The presence of the mefA gene was demonstrated in all isolates of S. pyogenes and the mefE gene in all but four S. pneumoniae isolates exhibiting the M phenotype. Due to the increasing susceptibility of S. pyogenes and S. pneumoniae isolates to clindamycin, susceptibility tests of these two organisms to macrolides and clindamycin should be performed simultaneously in the clinical microbiology laboratory, particularly in areas with high rates of macrolide resistance.     

In vitro activity of telithromycin (HMR 3647) against Greek Streptococcus pyogenes and Streptococcus pneumoniae clinical isolates with different macrolide susceptibilities

The susceptibilities to macrolides and telithromycin of 161 Streptococcus pyogenes and 145 Streptococcus pyogenes strains, consecutively isolated from five Greek hospitals, were determined by Etest. Moreover, mechanisms of resistance to macrolides were phenotypically and genetically determined by double disk induction test and PCR, respectively. Of the S. pneumoniae and S. pyogenes isolates, 42.8% and 30.8%, respectively, were found to be resistant to erythromycin. Of the erythromycin-resistant S. pneumoniae and S. pyogenes isolates, 57.5% and 59.5%, respectively, displayed the M phenotype and harbored the mefA/E gene. Telithromycin was found to be more active than both erythromycin and clarithromycin against both species, with considerably lower MIC₅₀ and MIC₉₀ values.     

Branhamella catarrhalis: incidence in pulmonary infections and determination of sensitivity to 5 antibiotics

This study reports 45 cases of respiratory tract infection associated with Branhamella catarrhalis, diagnosed by bacteriological examination out of 980 sputum samples studied over a 6 months period. These infections were observed mainly in patients with chronic respiratory disease (68.9%). More than half of the isolates were found in pure culture, others were isolated from mixed infections most often with Haemophilus influenzae, Streptococcus pneumoniae or H. influenzae plus S. pneumoniae. 64.7% of Branhamella catarrhalis isolates produced beta-lactamase. In vitro antimicrobial susceptibility testing demonstrated that the B. catarrhalis isolates, including beta-lactamase producing strains, were very susceptible to clavulanic acid plus amoxycillin (MIC90:0.12 microgram/ml) as well as to doxycycline and erythromycin (MIC90:0.5 microgram/ml).     

Simultaneous detection of pathogens in clinical samples from patients with community-acquired pneumonia by real-time PCR with pathogen-specific molecular beacon probes

In this study, real-time PCR with pathogen-specific molecular beacons (MB) and primers was evaluated for prediction of community-acquired pneumonia (CAP) causative agents, detecting six main CAP agents, Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila, and Streptococcus pyogenes, simultaneously. The PCR assay was evaluated for fresh clinical specimens from infants and children (n = 389) and from adults (n = 40). The MB probes and primers are both pathogen specific, namely, the lytA gene for S. pneumoniae, the mip gene for L. pneumophila, and 16S rRNA genes for the remaining four organisms. DNA extraction of clinical specimens was performed with a commercially available EXTRAGEN II kit, and amplification was performed with Stratagene Mx3000P. The limit of detection for these pathogens ranged from 2 copies to 18 copies. The whole process from DNA extraction to the analysis was finished in less than 2 h. The obtained sensitivity and specificity of this real-time PCR study relative to those of conventional cultures were as follows: 96.2% and 93.2% for S. pneumoniae, 95.8% and 95.4% for H. influenzae, 100% and 100% for S. pyogenes, and 100% and 95.4% for M. pneumoniae, respectively. The sensitivity and specificity for M. pneumoniae relative to those of a serologic assay were 90.2% and 97.9%, respectively. In six clinical samples of C. pneumoniae, the real-time PCR gave positive predictable values, and in those cases, elevation of the titer value was also observed. In conclusion, we demonstrated that a real-time PCR assay with pathogen-specific MB is useful in identifying CAP causative agents rapidly and in examining the clinical course of empirical chemotherapy in a timely manner, supporting conventional culture methods.     

National surveillance programme on susceptibility patterns of respiratory pathogens in South Africa: moxifloxacin compared with eight other antimicrobial agents

AIMS: The susceptibility patterns of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Klebsiella pneumoniae, and Streptococcus pyogenes isolated from specimens submitted to 12 private laboratories in South Africa were determined. METHODS: Minimum inhibitory concentration (MIC) determinations were performed on the isolates in the microbiology laboratory at Tygerberg Hospital according to the recommendations of the National Committee for Clinical Laboratory Standards (NCCLS). RESULTS: According to the NCCLS breakpoints, 24% of 729 S pneumoniae isolates were sensitive, 30% intermediate, and 46% resistant to penicillin. Rates of macrolide resistance were high, with 61% of the pneumococci being resistant to clarithromycin and azithromycin. Co-trimoxazole resistance was also high, with 28% of pneumococcal strains being sensitive, 21% intermediate, and 51% resistant. beta Lactamase was produced by 7% of 736 H influenzae isolates and 91% of 256 M catarrhalis isolates. The quinolones, moxifloxacin and levofloxacin, were universally active against all isolates tested, which included S pneumoniae, H influenzae, M catarrhalis, K pneumoniae, and S pyogenes. CONCLUSIONS: Haemophilus influenzae and S pneumoniae were the most commonly isolated organisms. Resistance to penicillin was one of the highest reported in the world (76%) in S pneumoniae, as was macrolide resistance in pneumonocci, although surprisingly, only 14% of S pyogenes were resistant. The quinolones, moxifloxacin and levofloxacin, were active against all organisms tested, including the penicillin and macrolide resistant strains and moxifloxacin was more active than levofloxacin against pneumococci.     

Use of Haemophilus test medium for broth microdilution antimicrobial susceptibility testing of Streptococcus pneumoniae.

A recently described medium (Haemophilus test medium [HTM]) for antimicrobial susceptibility testing of Haemophilus influenzae was evaluated in this study for broth microdilution testing of Streptococcus pneumoniae. A total of 137 clinical isolates was tested against 11 antimicrobial agents, using Mueller-Hinton broth supplemented with 3% lysed horse blood in parallel with HTM. Inocula of 5 X 10(5) CFU/ml and incubation for 20 to 24 h were used with both media. All isolates of S. pneumoniae produced acceptable growth in both media, and MICs determined in HTM agreed closely with those determined in lysed horse blood. Drugs which provided a MIC within 1 log2 concentration difference in both media included penicillin (100%), ampicillin (98.0%), amoxicillin-clavulanate (100%), ampicillin-sulbactam (100%), cephalexin (98.9%), cefaclor (96.8%), cefuroxime (99.0%), chloramphenicol (96.2%), tetracycline (96.2%), and erythromycin (100%). HTM MICs with trimethoprim-sulfamethoxazole were 1 to 2 log2 concentration increments higher in 92.0% of isolates than MICs determined in lysed horse blood. Based on the results of this study, HTM appears to represent a promising alternative medium for broth microdilution susceptibility testing of S. pneumoniae.     

Antimicrobial susceptibility and survey of macrolide resistance mechanisms among Streptococcus pyogenes isolated in Rio de Janeiro,Brazil

A total of 357 clinical Streptococcus pyogenes isolates collected between 1994 and 1999 in Rio de Janeiro city were tested for susceptibility to 10 antimicrobial drugs by agar-diffusion tests. All isolates were susceptible to penicillin, cephems, and vancomycin. High resistance rates were observed for tetracycline (43.1%) and trimethoprim/sulfamethoxazole (77.9%). Three isolates (0.8%) were resistant to erythromycin, and three exhibited intermediate susceptibility. Determination of the erythromycin MICs by the agar dilution method, showed 1.6% of erythromycin resistant isolates (the three erythromycin-resistant and the three erythromycin-intermediate isolates found by agar-diffusion test). Of the erythromycin-resistant isolates subjected to the double-disc diffusion test for erythromycin and clindamycin, three isolates expressed the iMLSB and three the M phenotype. The resistance phenotypes were confirmed by comparing the clindamycin MICs determined under normal testing conditions and those determined after induction by pre-growth in 0.06 microg/ml of erythromycin. Three ermTR and three mefA-containing isolates were detected by PCR. In strains belonging to the iMLSB phenotype, two clones were identified by PFGE following restriction with SmaI. M phenotype isolates could not be restricted with SmaI. Our results indicate a low rate of erythromycin resistance among S. pyogenes isolated in Rio de Janeiro, Brazil, and pointed to the presence of both resistance mechanisms found in streptococci.     

Macrolide resistance trends in beta-hemolytic streptococci in a tertiary Korean hospital

PURPOSE: Erythromycin-resistant beta-hemolytic streptococci (BHS) has recently emerged and quickly spread between and within countries throughout the world. In this study, we evaluate the antimicrobial susceptibility patterns and erythromycin resistance mechanisms of BHS during 2003-2004. MATERIALS AND METHODS: The MICs of seven antimicrobials were determined for 204 clinical isolates of BHS from 2003 to 2004. Resistance mechanisms of erythromycin-resistant BHS were studied by the double disk test as well as by polymerase chain reaction (PCR). RESULTS: Compared with our previous study, resistance among Streptococcus pyogenes isolates to a variety of drugs decreased strikingly: from 25.7% to 4.8% in erythromycin; 15.8% to 0% in clindamycin; and 47.1% to 19.0% in tetracycline. The prevalent phenotypes and genotypes of macrolide-lincosamide-streptograminB (MLSB) resistance in Streptococcus pyogenes isolates have been changed from the constitutive MLSB phenotype carrying erm(B) to the M phenotype with mef(A) gene. In contrast with Streptococcus pyogenes, resistance rates to erythromycin (36.7%), clindamycin (43.1%), and tetracycline (95.4%) in Streptococcus agalactiae isolates did not show decreasing trends. Among the Streptococcus dysgalactiae subsp. equisimilis isolates (Lancefield group C, G), resistance rates to erythromycin, clindamycin, tetracycline and chloramphenicol were observed to be 9.4%, 3.1%, 68.8%, and 9.4%, respectively. Conclusion: Continual monitoring of antimicrobial resistance among large-colony-forming BHS is needed to provide the medical community with current data regarding the resistance mechanisms that are most common to their local or regional environments.     

The effect of carbon dioxide on susceptibility testing of azithromycin, clarithromycin and roxithromycin against clinical isolates of Streptococcus pneumoniae and Streptococcus pyogenes by broth microdilution and the Etest: Artemis Project—first-phase study

Objective: To evaluate the effect of carbon dioxide on the susceptibility testing, using broth microdilution and the Etest (AB Biodisk, Solna, Sweden), of azithromycin, clarithromycin and roxithromycin against Streptococcus pneumoniae and Streptococcus pyogenes .
Methods: Fresh clinical isolates collected from 36 hospital laboratories in 12 countries were evaluated using the Etest in the presence of carbon dioxide. The isolates were retested under ambient conditions (absence of carbon dioxide) using broth microdilution and/or the Etest.
Results: Carbon dioxide falsely elevated azithromycin, clarithromycin and roxithromycin MIC₉₀S for S. pneumoniae , determined by the Etest, approximately 12-fold. Also, the azithromycin MIC₉₀ for S. pyogenes was increased fourfold; the effect was less marked for clarithromycin and roxithromycin. When isolates were retested in the absence of carbon dioxide, using the Etest or microdilution, susceptibilities to azithroymycin were comparable to those to clarithromycin ( S. pneumoniae , 93.4% versus 91.3%; S. pyogenes , 96.4% versus 95.8%). Both organisms were less susceptible to roxithromycin ( S. pneumoniae , 71.3%; S. pyogenes , 85.7%). An internal standard control, consisting of 50 isolates each of S. pneumoniae, S. pyogenes and Haemophilus influenzae , confirmed that azithromycin susceptibility testing resulted in falsely elevated MICs.
Conclusions: Carbon dioxide falsely elevated azithromycin MICs for S. pneumoniae and S. pyogenes , with an apparent reduction in susceptibility. When the in vitro activity of azithromycin and other macrolides against S. pneumoniae and S. pyogenes is being evaluated, awareness of the pH effect is essential.     

Is There an Ecological Relationship between Rates of Antibiotic Resistance of Species of the Genus Streptococcus?

The relationship between resistance to antibiotics on the part of Streptococcus pneumoniae and Streptococcus pyogenes was studied by comparing different prevalences of resistance among hospitals obtained from a recent microbiological surveillance of community-acquired respiratory tract infections. A high correlation for erythromycin resistance was found between S. pneumoniae isolates from lower respiratory tract infections and S. pyogenes isolates collected from pharyngeal swabs.     

Etiology of invasive bacterial infections in immunocompetent children in Korea (1996-2005): a retrospective multicenter study

The purpose of this study was to identify the major etiological agents responsible for invasive bacterial infections in immunocompetent Korean children. We retrospectively surveyed invasive bacterial infections in immunocompetent children caused by eight major pediatric bacteria, namely Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pyogenes, Listeria monocytogenes, and Salmonella species that were diagnosed at 18 university hospitals from 1996 to 2005. A total of 768 cases were identified. S. agalactiae (48.1%) and S. aureus (37.2%) were the most common pathogens in infants younger than 3 months. S. agalactiae was a common cause of meningitis (73.0%), bacteremia without localization (34.0%), and arthritis (50%) in this age group. S. pneumoniae (45.3%) and H. influenzae (20.4%) were common in children aged 3 months to 5 yr. S. pneumoniae was a common cause of meningitis (41.6%), bacteremia without localization (40.0%), and bacteremic pneumonia (74.1%) in this age group. S. aureus (50.6%), Salmonella species (16.9%), and S. pneumoniae (16.3%) were common in older children. A significant decline in H. influenzae infections over the last 10 yr was noted. S. agalactiae, S. pneumoniae, and S. aureus are important pathogens responsible for invasive bacterial infections in Korean children.     

Associated antimicrobial resistance in Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes

Associated resistance to four to six related and unrelated antimicrobial agents was investigated in consecutive non-duplicate isolates of Escherichia coli (n = 39 425), Pseudomonas aeruginosa (n = 1070), Staphylococcus aureus (n = 7489), Streptococcus pneumoniae (n = 1604) and Streptococcus pyogenes (n = 2531). In all species, high proportions (76.5-88.9%) of isolates were susceptible to all the drugs investigated. Irrespective of species, isolates resistant to one drug were more likely to be resistant to any of the other drugs than were susceptible isolates. Thus, trimethoprim resistance in E. coli was 38.4% among ampicillin-resistant vs. 3.9% among ampicillin-susceptible isolates, and erythromycin resistance in Strep. pneumoniae was 41% among doxycycline-resistant vs. 1% among doxycycline-susceptible isolates. In all five species investigated, there was also significant associated resistance among unrelated drugs, highlighting the fact that resistance development occurs primarily among bacteria already resistant to one or more antimicrobial agents. For the clinician, pronounced resistance associations mean that when empirical therapy fails because of resistance, there is a reduced chance of choosing an alternative successful empirical agent. For the epidemiologist, who uses routine clinical susceptibility data to describe resistance development, resistance associations mean that if the dataset contains results for isolates selected on the basis of their susceptibility to another drug, structurally related or not, a bias of false resistance is introduced.     

A multicenter study of the antimicrobial susceptibility of Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis isolated from patients with community-acquired lower respiratory tract infections in 1999 in Portugal

A nationwide multicenter study (including 25 laboratories) of the antimicrobial susceptibility of bacterial pathogens commonly associated with community-acquired lower respiratory tract infections (LRTI), with testing undertaken in a central laboratory, was conducted in Portugal in 1999. Antimicrobial resistance in Haemophilus influenzae has not increased in the last decade. Of the 498 isolates tested, 12.4% produced beta-lactamase and >95% were susceptible to all antimicrobials except ampicillin. In contrast, there was a rapid increase of resistance in Streptococcus pneumoniae. Of the 312 isolates tested, 24.7% exhibited decreased susceptibility to penicillin (13.5% showed low-level and 11.2% high-level resistance), 13.8% were resistant to erythromycin, clarithromycin and azithromycin, and 13.6% to cefuroxime and to tetracycline. Of the 38 Moraxella catarrhalis tested, 81.6% produced beta-lactamase. Resistance to penicillin, cefuroxime, erythromycin, clarithromycin, and azithromycin in S. pneumoniae and beta-lactamase production in H. influenzae were significantly higher in pediatric patients than in adults. Overall, amoxycillin/clavulanate was the most active antimicrobial agent in vitro against H. influenzae, S. pneumoniae, and M. catarrhalis isolated from patients with community-acquired LRTI in Portugal.     

Characteristics of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis isolated from the nasopharynges of asymptomatic children and molecular analysis of S. pneumoniae and H. influenzae strain replacement in the nasopharynx

Nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in 226 children in different settings (in a crèche [day care center], in an orphanage, and at home) during two seasons (winter and spring) was studied. The rates of carriage of S. pneumoniae and H. influenzae were markedly higher in the crèche and in the orphanage than in the home setting (e.g., 56.5, 63.3, and 25.9%, respectively, for S. pneumoniae in winter). Approximately 80% of the S. pneumoniae isolates identified in the crèche and in the orphanage belonged to the serotypes represented in the seven-valent pneumococcal vaccine, and 4.4% of the children were colonized by H. influenzae type b. Almost all H. influenzae isolates were fully susceptible to the antimicrobial agents tested, and only five (3.6%) produced beta-lactamase; in contrast, 100% of the M. catarrhalis isolates were beta-lactamase positive. Among S. pneumoniae isolates, 36.2% were nonsusceptible to penicillin (PNSP) and 11.8% were fully resistant to penicillin (PRP). All PNSP isolates were obtained from children at the crèche and at the orphanage but not among children brought up at home, and all PRP isolates showed a multiresistant phenotype. Colonization by PRP isolates correlated well with prior treatment with beta-lactams. For the majority of children colonized at both sampling times, strain replacement of S. pneumoniae and H. influenzae was observed; long-term colonization by a single strain was rare.     

Antimicrobial susceptibility patterns of Haemophilus influenzae and Streptococcus pneumoniae isolates in a Beirut general university hospital between 2000 and 2004

Susceptibility patterns of Streptococcus pneumoniae and Haemophilus influenzae collected over a 5-year period in a Beirut general university hospital were studied. Only 40.6-50% of S. pneumoniae isolates were susceptible to penicillin G. Susceptibility to clindamycin and erythromycin decreased from 94.1% and 89.7%, respectively, in 2000 to 75% and 71.9%, respectively, in 2004. All isolates were susceptible to ceftriaxone, ciprofloxacin and vancomycin. For H. influenzae, no resistance was observed to amoxycillin-clavulanate, ceftriaxone, ciprofloxacin and rifampicin, with >92% of isolates showing susceptibility to cefuroxime, chloramphenicol, erythromycin and tetracycline. The proportion of beta-lactamase-positive isolates varied between 22.7 and 30.8%.     

Rapidly increasing prevalence of penicillin-resistant Streptococcus pneumoniae in middle Tennessee: a 10-year clinical and molecular analysis

The clinical and molecular epidemiology of penicillin-resistant Streptococcus pneumoniae and the diagnostic accuracy of a six-primer PCR assay in identifying penicillin resistance were analyzed by using clinical isolates recovered over a 10-year period in middle Tennessee. The prevalence of non-penicillin-susceptible S. pneumoniae isolates (MIC, > or =0.1 microg/ml) increased from 10% in 1990 to 70% in 1999 (P < 0.001). Among S. pneumoniae isolates for which the penicillin MIC was > or =2 microg/ml (highly penicillin-resistant S. pneumoniae [PRSP]), 23 and 5% were resistant to at least three and at least five other antimicrobial classes, respectively. Pulsed-field gel electrophoresis identified 13 unique strain types, with type B accounting for 33% of PRSP isolates. The sensitivity, specificity, and negative and positive predictive values of the PCR assay in detecting PRSP were 99, 100, 99, and 100%, respectively. Penicillin resistance is rapidly increasing among S. pneumoniae isolates in Tennessee. The simultaneous detection of S. pneumoniae and high-level penicillin resistance can be accurately performed with the six-primer PCR assay.     

Increasing prevalence of antimicrobial resistance in Streptococcus pneumoniae in Kuwait: implications for therapy

From 2001 to 2004, 824 consecutive Streptococcus pneumoniae isolates obtained from all the teaching hospitals and primary-care centers serving all of Kuwait were studied for their susceptibility to a number of antibiotics. Of these, 514 (63%) were resistant to penicillin, 55% of which were of intermediate resistance, with a minimum inhibitory concentration (MIC) of 0.16-1 microg/ml, and 8% were of full resistance (MIC > or =2 microg/ml). The prevalence of penicillin resistance was significantly higher among the eye isolates than the rest of the isolates combined. Resistance across all classes of antibiotics was more common with the isolates from blood and cerebrospinal fluid (CSF). Decreased susceptibility to ceftriaxone, cefotaxime, imipenem, meropenem, erythromycin, and cotrimoxazole was observed in 15%, 12.8%, 10.2%, 8.6%, 42%, and 69% of isolates, respectively. Multidrug-resistant S. pneumoniae was isolated mostly from invasive diseases. There has been a remarkable increase in the prevalence of drug-resistant S. pneumoniae isolates in Kuwait over the past 20 years, and Kuwait has thus joined the league of hyperendemic countries for penicillin-resistant S. pneumoniae (PRSP). It is also conceivable that Kuwait, with a large expatriate population of workers, may serve as a focal point for further dissemination of resistant clones to the rest of the world. These data are unique because they are representative of the whole Kuwaiti population.     

Characterization of erythromycin-resistant Streptococcus pneumoniae in Korea, and In Vitro activity of telithromycin against erythromycin-resistant Streptococcus pneumoniae

To characterize the phenotypes and genotypes of erythromycin-resistant clinical isolates of Streptococcus pneumoniae in Korea and to evaluate the in vitro activity of telithromycin against these erythromycin-resistant isolates, we tested a total of 676 isolates of S. pneumoniae collected from 1997 to 2002 in a tertiary hospital in Seoul, Republic of Korea. MICs for erythromycin and telithromycin were determined by the agar dilution method. The macrolide resistance phenotypes of erythromycin-resistant isolates were determined by the erythromycin- clindamycin-rokitamycin triple disk (ECRTD) and MIC induction tests, whereas their macrolide resistance genotypes were determined by PCR for the erm(B), erm(A), subclass erm(TR), and mef genes. To discriminate between mef(A) and mef(E), PCR-restriction fragment length polymorphism (RFLP) analyses were performed. Of the 676 S. pneumoniae isolates, 459 (67.9%) were resistant to erythromycin. Of the 459 erythromycin-resistant isolates, 343 (74.7%) were assigned to the cMLS phenotype, 48 (10.4%) to the iMcLS phenotype, 4 (0.9%) to the iMLS phenotype, and 64 (14.0%) to the M phenotype. The erm(B) gene was detected in 251 (54.6%) isolates, the mef gene was detected in 64 (14.0%), and both the erm(B) and mef genes were detected in 144 (31.4%) isolates. All of the mef genes detected were identified as mef(E). Of the 459 erythromycin- resistant isolates, all but one were susceptible to telithromycin. The MIC(50)/MIC(90) to telithromycin of isolates carrying erm(B), mef(E), and both genes was 0.06/0.5 microg/ml, 0.03/0.125 microg/ml, and 0.5/1.0 microg/ml, respectively. Although the MICs of telithromycin for the erythromycin-resistant isolates varied according to genotype, telithromycin was very active against these erythromycin-resistant S. pneumoniae.