Pneumococcal resistance to antimicrobial agents in the province of Québec, Canada

Reporting Emerging Resistance of Streptococcus pneumoniae from India

Background:

There are reports of emergence of resistant strains of S. pneumoniae showing resistance to penicillin from all over the world, and now, resistance to multiple drugs (multidrug-resistant strains) has been added to it. However, scanty reports are available so far from India, depicting such resistance.

Aims:

The aim of the present study is to look for the prevalence of penicillin-resistant pneumococci and also the multidrug-resistant strains among S. pneumoniae, isolated from respiratory specimens, in the coastal part of South India.

Settings and Design:

A cross-sectional study was conducted from June 2008 to December 2008, in our tertiary care center. Fifty pathogenic clinical isolates were collected from patients suffering from lower respiratory tract infections.

Materials and Methods:

Penicillin resistance was screened by 1 μg oxacillin disk on Muller-Hinton blood agar followed by Minimum Inhibitory Concentration (MIC) detection by the agar dilution method according to the Clinical Laboratory Standards Institute (CLSI) guidelines. Antibiotic susceptibility for other antibiotics was carried out by the Kirby Bauer disk diffusion method followed by an E-test with HiComb test strips from Hi-media.

Results:

Out of 50 isolates, 4% (95% Confidence Interval - 1.4, 9.4) showed total resistance to penicillin, whereas, 10% (95% CI; 1.6, 18.3) showed intermediate resistance. These penicillin-resistant pneumococci (4%) were also found to be multidrug-resistant (MDR) strains. Maximum resistance was observed for cotrimoxazole and tetracycline (24% each with 95% CI; 12.2, 35.8) followed by erythromycin and ciprofloxacin (14% each with 95%CI; 4.4, 23.6).

Conclusions:

Increasing emergence of the resistant strains of S. pneumoniae in the community set up requires continuous monitoring and a restricted use of antibiotics to keep a check on its resistance pattern, for an effective treatment plan.

Surveillance of invasive Streptococcus pneumoniae infection in the province of Quebec, Canada, from 1996 to 1998: serotype distribution, Antimicrobial susceptibility, and clinical characteristics

In the province of Quebec, Canada, from 1996 to 1998, 3,650 invasive Streptococcus pneumoniae infections were reported. A total of 1,354 isolates were serotyped and tested for antimicrobial susceptibility. The distribution of serotypes remained stable over the 3 years, with serotypes 14, 6B, 4, 9V, 23F, and 19F accounting for 61% of the isolates. Overall, 90% of isolates were included in the current 23-valent vaccine and 67% were included in the 7-valent conjugate vaccine. We were able to determine that resistance to penicillin and to other antibiotics is increasing.

Extremely high prevalence of nasopharyngeal carriage of penicillin-resistant Streptococcus pneumoniae among children in Kaohsiung, Taiwan

Resistance (intermediate and high) to penicillin among Streptococcus pneumoniae strains is an emerging problem worldwide. From 1995 to 1997, isolates of S. pneumoniae not susceptible to penicillin were seen with increasing frequency from blood, cerebrospinal fluid, pleural fluid, and middle ear fluid from pediatric patients at the Veterans General Hospital-Kaohsiung. To determine the prevalence of carriage of these penicillin-nonsusceptible S. pneumoniae isolates, we obtained nasopharyngeal swab specimens from 2,905 children (ages, 2 months to 7 years) attending day-care centers or kindergartens or seen in our outpatient clinic. S. pneumoniae was isolated from 611 children, and 584 strains were available for analysis. The oxacillin disc test was used as a screening test to evaluate penicillin susceptibility. The MICs of 11 antibiotics (penicillin, cefaclor, cefuroxime, ceftriaxone, cefotaxime, imipenem, chloramphenicol, clarithromycin, rifampin, vancomycin, and teicoplanin) were determined by the E-test. Only 169 (29%) of the strains were susceptible to penicillin; 175 (30%) strains were intermediately resistant and 240 (41%) were highly resistant. The isolates also demonstrated high rates of resistance to other beta-lactams (46% were resistant to cefaclor, 45% were resistant to cefuroxime, 45% were resistant to ceftriaxone, 31% were resistant to cefotaxime, and 46% were resistant to imipenem). The rate of resistance to macrolide antimicrobial agents was strikingly high; 95% of the isolates were not susceptible to clarithromycin. However, 97% were susceptible to rifampin and 100% were susceptible to the two glycopeptides (vancomycin and teicoplanin). While reports of penicillin-resistant S. pneumoniae increased worldwide through the 1980s, the high prevalence (71%) of resistance reported here is astonishing. Surveillance of nasopharyngeal swab specimen cultures may provide useful information on the prevalence of nonsusceptible strains causing invasive disease. Such information could be used to guide therapy of pneumococcal infections.

Invasive Streptococcus pneumoniae infections: serotype distribution and antimicrobial resistance in Canada, 1992-1995

OBJECTIVE

To report current information about invasive pneumococcal infections, capsular types and antimicrobial resistance in Canada.

DESIGN

Retrospective analysis.

SETTING

Canada.

PATIENTS

A total of 976 patients from whom Streptococcus pneumoniae was isolated from blood or cerebrospinal fluid between Jan. 1, 1992, and Dec. 31, 1995.

OUTCOME MEASURES

Capsular type and antimicrobial susceptibility.

RESULTS

Twenty types accounted for 90.8% of the isolates from patients over 5 years of age; all but type 15A are covered by the currently available 23-valent vaccine. Nine types accounted for 92% of the isolates recovered from children 5 years and less. Reduced susceptibility to penicillin was found in 7.8% of the collection and was associated with types 6B, 9V and 19A. Full resistance to penicillin was observed most frequently during 1995 and was associated with type 9V. Rates of reduced susceptibility over one 12-month period were 19.5% for trimethoprim-sulfamethoxazole and 4.5% or less for each of cefotaxime, ceftriaxone, chloramphenicol, erythromycin, ofloxacin and tetracycline.

CONCLUSIONS

Over 90% of invasive pneumococcal infections are covered by the currently available vaccines (for people over 2 years of age) and the pneumococcal protein-polysaccharide conjugate vaccines under development for young children. The high frequency of antimicrobial resistance observed requires more complete investigation and confirmation; however, taken from a global perspective, it supports the need to develop better control strategies, including greater use of new and existing vaccines.

Antibiotic selection in the treatment of endophthalmitis: the significance of drug combinations and synergy

Emerging resistance of organisms to standard antibiotic therapy has forced clinicians to continually evaluate the best intraocular antibiotics for the treatment of endophthalmitis. Early diagnosis and appropriate treatment with intraocular antibiotics are important factors in the successful management of endophthalmitis. Although drug combinations are necessary to cover the full range of bacteria causing endophthalmitis, antimicrobial synergy is probably less important in endophthalmitis treatment because of the high intravitreal concentration of individual antibiotics achieved by intravitreal injection. In the treatment of bacterial endophthalmitis, the combination of intravitreal vancomycin (1 mg/0.1 cc) and ceftazidime (2.25 mg/ 0.1 cc) is a reasonable alternative to the combination vancomycin and amikacin (0.4 mg/ 0.1 cc).

Cefotaxime. A reappraisal of its antibacterial activity and pharmacokinetic properties, and a review of its therapeutic efficacy when administered twice daily for the treatment of mild to moderate infections

Cefotaxime is well established as an effective and well tolerated antibacterial drug for 3 times daily parenteral treatment of a variety of moderate to severe infections in hospitalised patients. Its frequency of administration has recently been reassessed with a 12-hourly regimen. Comparative studies in hospitalised patients with nosocomial or community-acquired lower respiratory tract infections, demonstrate the similar clinical and bacteriological efficacy of twice daily cefotaxime 1 or 2 g and the same daily dose of ceftriaxone, usually administered once daily. Cefotaxime 2 g twice daily was also similar in efficacy to ceftriaxone 2 g once daily. Retrospective and post-marketing studies also reveal the similar efficacy of cefotaxime administered twice and 3 times daily, and pharmacoeconomic studies suggest that total direct costs of treatment with cefotaxime compared is similar to that with other third generation cephalosporins in currently used dosage regimens. When administered twice daily, cefotaxime is, thus, an effective antibacterial agent for the treatment of hospitalised patients outside the intensive care unit with a variety of mild to moderate non-CNS infections caused by susceptible organisms. When appropriately administered twice daily there is potential to lower the cost of antibacterial treatment without compromising efficacy.

Comparison of the serum-supplemented Todd-Hewitt and the new Haemophilus test media for broth microdilution susceptibility testing of Streptococcus pneumoniae

Horse serum-supplemented Todd-Hewitt broth (STH) in use at Hôpital Ste-Justine for the last 12 years was compared to the recently proposed Haemophilus test medium (HTM), for broth microdilution susceptibility testing of Streptococcus pneumoniae. One hundred and twenty S. pneumoniae isolates from pediatric clinical specimens were used in this study. In general, the minimum inhibitory concentrations (MICs) in STH for 15 antimicrobial agents were quite comparable to those determined in HTM but tended to be higher. Drugs which generated MICs within +/- 1 log2 concentration differences in both media included penicillin, ampicillin, oxacillin, cefuroxime, cefotaxime, cefixime, clindamycin, chloramphenicol, trimethoprim-sulfamethoxazole, rifampin, ciprofloxacin and vancomycin. Cefaclor and tetracycline MICs tended to be > or = 2 log2 dilutions higher with STH for most of the isolates tested, while erythromycin MICs were often 2 log2 dilutions lower with STH than with HTM. Despite some differences in MICs noted above, few very major (0.4%), major (0.2%) and minor interpretive category errors (4.4%) were observed. The visual reading of the MICs for most of the 120 clinical isolates tested was generally easier in STH which was superior in supporting best the bacterial growth as detected by spectrophotometry. The risk of false susceptibility is thus decreased by using STH rather than HTM; furthermore, STH is free of the technical problems of the lysed horse blood Mueller-Hinton (LHB-MH) recommended by the NCCLS.

Meningitis in a Canadian adult due to high level penicillin-resistant, cefotaxime-intermediate Streptococcus pneumoniae

Invasive penicillin-resistant pneumococcal (PRSP) infections are increasing worldwide. In Canada, the incidence of penicillin resistance among Streptococcus pneumoniae isolates is estimated at greater than 6%. In Quebec, only one case of PRSP meningitis has been reported and involved an infant. An adult patient is described who presented with meningitis caused by high level penicillin-resistant, cefotaxime-intermediate S pneumoniae.

Distribution of capsular types and antibiotic susceptibility of invasive Streptococcus pneumoniae isolated from aborigines in central Australia

Streptococcus pneumoniae strains isolated from 203 episodes of invasive disease in central Australian Aborigines were studied. Capsular types from children aged 0 to 4 years (n = 89) belonged most commonly to types 14, 6B, 9V, 4, 18C, and 19F, which together accounted for 67% of the pediatric strains. In adults (n = 98), types 1, 7F, 3, 4, 12F, and 8 contributed 68% of the isolates. Of 114 pneumococci from patients 5 years and older, 102 (89.5%) were types represented in the 23-valent pneumococcal polysaccharide vaccine. The MICs of five antibiotics were determined for 201 strains by using the E-Test (AB Biodisk). No chloramphenicol or ceftriaxone resistance was found, but 46 strains (22.9%) showed diminished susceptibility to one or more of the drugs penicillin, erythromycin, and trimethoprim-sulfamethoxazole. Penicillin resistance occurred in 15.4% of all isolates tested but only within the intermediate range (0.1 to 1.0 microgram/ml). Resistance to trimethoprimsulfamethoxazole affected 13.9% of the pneumococci tested. All type 23F and most type 19F organisms were resistant to one or more antibiotics. Resistance was significantly more common in pediatric isolates than in those from adults (chi 2(1) = 14.1; P < 0.001).

Evaluation of commercial methods for determining antimicrobial susceptibility of Streptococcus pneumoniae

Seven commercial systems for antimicrobial susceptibility testing of Streptococcus pneumoniae were evaluated by using a challenge set of 55 pneumococcal isolates with a variety of resistance phenotypes and genotypes. Overall, the results produced by the Pasco and Etest methods were found to be acceptable for all drugs tested except for trimethoprim-sulfamethoxazole testing by the Etest. The Just One system for penicillin MIC testing was also judged to be acceptable (minor error rate, 5.5%). Although the Sensititre and MicroTech methods both produced 12.7% minor errors with penicillin, the Sensititre method classified penicillin-intermediate strains as resistant or vice versa, while four of MicroTech's errors were among intermediate strains that were classified as susceptible. The MicroMedia (minor error rate, 16.4%) and MicroScan Rapid (minor error rate, 63.6%) methods produced unacceptably high levels of errors when testing penicillin. Minor error rates for cefotaxime and ceftriaxone ranged from a low of 12.7% (Etest and Sensititre) to a high of 28% (MicroMedia). Error rates were low for erythromycin, tetracycline, and chloramphenicol by most methods with the exception of the MicroScan method, which had a high very major error rate for erythromycin (34.6%). For testing of beta-lactam drugs, the Pasco, Etest, and Just One tests for penicillin are the most accurate methods; the Sensititre method also provided acceptable results.

Bactericidal activity of cefotaxime, desacetylcefotaxime, rifampin, and various combinations tested at cerebrospinal fluid levels against penicillin-resistant Streptococcus pneumoniae

Penicillin resistance is increasingly prevalent amongst clinical isolates of Streptococcus pneumoniae. Recently, isolates resistant to the extended-spectrum cephalosporins have also begun to emerge, and combination therapy may be necessary for infection with such organisms. We have studied the activity of cefotaxime, ceftriaxone, ceftazidime, rifampin, chloramphenicol, and vancomycin against 10 S. pneumoniae strains with penicillin minimum inhibitory concentrations (MICs) ranging from 0.03-8 micrograms/ml. The bactericidal activity of cefotaxime, desacetylcefotaxime, rifampin, and combinations of these agents (cerebrospinal fluid levels) against these isolates was determined. Elevated MICs to penicillin were associated with generally twofold lower cefotaxime MICs. All strains remained susceptible to vancomycin and rifampin. The bactericidal activity of cefotaxime with or without desacetylcefotaxime was reduced by the addition of rifampin. Pneumococcal isolates with penicillin MICs of < or = 1 microgram/ml were slowly killed by cefotaxime alone or with desacetycefotaxime. At present, there is little evidence to support the addition of rifampin to cefotaxime for therapy of meningitis.

The growing threat of antibiotic-resistant Streptococcus pneumoniae

Resistance to penicillin has spread worldwide during the past 25 years. Strains resistant to alternative antibiotics have also emerged. Strains resistant to multiple antibiotics increasingly are isolated worldwide. Recently, isolates of penicillin-resistant S. pneumoniae resistant to cefotaxime and ceftriaxone have caused meningitis. As a result, recommendations for the empiric therapy of pneumococcal infections, especially meningitis, are changing.

Occurrence of pneumococci with resistance or decreased susceptibility to penicillin in southeast Sweden

The minimal inhibitory concentrations (MICs) of 14 beta-lactam and non-beta-lactam antibiotics were determined for all pneumococci with intermediate susceptibility (I), (n = 26) or resistance (R), (n = 15) to penicillin G isolated at the Clinical Microbiology Laboratory, University Hospital, Linköping, Sweden during 1994. These isolates accounted for 3% of all pneumococcal isolates. The results were compared with those of 26 penicillin-susceptible isolates. The MICs of all tested beta-lactam antibiotics increased with MICs of penicillin G. The least increase and the lowest MICs of these agents were recorded for cefotaxime and imipenem. 27% of I- and R-strains were multiple-resistant, most often to tetracycline, trimethoprim-sulfametoxazole, erythromycin, chloramphenicol and clindamycin. All strains were susceptible to vancomycin and rifampicin. I-strains belonged to at least 5 different serotypes. However, 12 of the 15 R-strains were serotype 9 and 6 of these were recovered during contact tracing, indicating spread of a single clone within day-care centres.