Genetic relationships of penicillin-susceptible and -resistant Streptococcus pneumoniae strains isolated on different continents.

Sixty-six strains of Streptococcus pneumoniae isolated in different parts of the world, 46 resistant and 22 susceptible to penicillin, were subdivided by multilocus enzyme electrophoresis into 28 distinct electrophoretic types (ETs). The ETs to which penicillin-susceptible strains were assigned differed from those containing resistant isolates of the same serotype. Five common clones could be recognized among the penicillin-resistant bacteria by combining the ETs, the antigenic properties of penicillin-binding proteins PBP 1a and 2b, and the tetracycline and chloramphenicol resistance profiles. Two clones were found in Finland and were associated with capsular serotypes 6B and 23F, respectively. Two clones were from Spain (type 6B and 9V, respectively). The fifth clone was isolated in South Africa and in Spain and contained both serotype 23F isolates and one type 19F strain. The other resistant strains were represented by rare isolates distributed among 12 other ETs, confirming that resistance to penicillin has evolved by multiple branches. Because capsular type was mixed in several ETs, the results also demonstrate that it may vary among very closely related pneumococci.     

Meningitis due to mixed infection with penicillin-resistant and penicillin-susceptible strains of Streptococcus pneumoniae

Streptococcus pneumoniae is the major cause of bacterial meningitis. We report a case of meningitis due to a mixed infection with two distinct strains of S. pneumoniae: one penicillin-resistant strain of serotype 9V and one penicillin-susceptible strain of serotype 7. The two strains exhibited different pulsed-field gel electrophoresis profiles.     

Phenotypic and genotypic characterization of two penicillin-susceptible serotype 6B Streptococcus pneumoniae clones circulating in Italy

Twenty-nine penicillin-susceptible serotype 6B strains isolated from patients with invasive diseases and from healthy carriers were examined by different genotyping methods. Ten groups were identified on the basis of the pulsed-field gel electrophoresis (PFGE) profiles, and two of these contained multiple isolates and were analyzed further. PFGE group 1 comprised 12 isolates, the majority of which had a multiresistant phenotype (resistance to erythromycin, clindamycin, tetracycline, chloramphenicol, and trimethoprim-sulfamethoxazole), corresponding to that of a clone previously described in the Mediterranean area and related to penicillin-resistant clone Spain(6B)-2. The pbp2b, pbp2x, dhf, and pspA genes of the isolates had identical restriction profiles; and the partial sequence of pspA was identical to that of clone Spain(6B)-2. In all isolates the resistance determinants erm(B) and tet(M) were inserted in a Tn1545-like element; 11 isolates carried cat as part of the integrated plasmid pC194. Multilocus sequence typing (MLST) performed with two isolates confirmed that their profiles corresponded to that of the Mediterranean clone. PFGE group 2 comprised nine strains, of which the majority showed no antibiotic resistance. Their pspA profiles were different, and the partial sequences obtained for two representative isolates indicated the presence of PspA proteins of different clades. The MLST profile of one strain was identical to that of a serotype 6B strain from the United Kingdom, while two other isolates were novel one-allele variants. This clone appears to be related (five of seven identical alleles) to two other internationally disseminated clones, Hungary(19A)-6 and Poland(23F)-16, both of which are penicillin resistant. The presence of antibiotic-susceptible isolates of this clone suggests that traits other than antibiotic resistance can make a clone successful.     

In vivo efficacy of cefotaxime and amoxicillin against penicillin-susceptible, penicillin-resistant and penicillin-cephalosporin-resistant strains of Streptococcus pneumoniae in a mouse pneumonia model

Objective: To compare cefotaxime (CTX) to amoxicillin (AMO) (usually considered the definitive therapy for penicillinsusceptible Streptococcus pneumoniae infections) in an immunocompromised mouse pneumonia model.
Methods: Three S. pneumoniae clinical isolates were used: two serotype 19 strains, a penicillin-susceptible (P^s) strain (penicillin MIC = 0.03 μ/mL) and a highly penicillin-resistant (P^r) strain (penicillin MIC = 4 μ/mL), and one serotype 23F strain, a penicillin-cephalosporin-resistant (CFTR) strain (CTX MIC = 4 μ/mL).
Results: CTX activity in this mouse model of pneumonia induced by the highly penicillin-resistant strain of S. pneumoniae was lower than expected from its low MIC against this organism. Furthermore, AMO had greater efficacy than CTX against a CFTR S. pneumoniae strain.
Conclusion: Our data suggest that there is no major difference in the in vivo efficacy of the two agents, cefotaxime and amoxicillin, against penicillin-resistant and penicillin-cephalosporin-resistant S. pneumoniae.     

Stability of penicillin-susceptible and nonsusceptible clones of Streptococcus pneumoniae in southern Sweden

Understanding what determines the stability and global spread of pneumococcal clones is important for future public health interventions. This requires better knowledge about the stability and distribution of existing clones. In this study we characterized and compared penicillin nonsusceptible (PNSP) and susceptible pneumococci (PSP) from southern Sweden. A total of 166 isolates of Streptococcus pneumoniae, recovered in Malmohus County between 1982 and 1997, were analyzed with molecular and microbiological techniques; 107 PNSP isolates of serogroup 15, collected between 1992 and 1995, and 15 PNSP isolates of serogroup 9, isolated in 1996 and 1997, were studied. In addition, PSP of serogroups 9 and 15, isolated approximately 10 years apart, were studied; 23 of serogroup 9 and 21 of serogroup 15, isolated in 1982-1983 and 1992-1993. As expected, a high degree of homogeneity was found in the PNSP isolates, where all the isolates of serogroup 9 belonged to the same clone, Spain(9V)-3, and the majority of the serogroup 15 isolates belonged to the Sweden(15A)-25 clone. The remaining PNSP isolates of serogroup 15 belonged to a clone found in The Netherlands and Greece. An unexpectedly high degree of clonality and stability of the PSP isolates was observed. Isolates representing clones that remained stable for over 10 years were found among both serogroups. These results indicate that factors, other than antimicrobial resistance, play an important part in establishing successful clones of S. pneumoniae, and these factors may be instrumental in determining the success or failure of clones after they acquire resistance.     

Identifying non-capsulate strains of Streptococcus pneumoniae isolated from eyes.

Over six months 10 biochemically and physiologically atypical strains of Streptococcus pneumoniae were isolated from eye swabs. Conventional methodology showed that these strains possessed characteristics of both S pneumoniae and other alpha haemolytic streptococci. The use of sodium dodecyl sulphate - polyacrylamide gel electrophoresis (SDS-PAGE) enabled us to characterise these strains as S pneumoniae. Loss of the capsule seemed to be associated with atypical biochemical properties.     

Detection of SHV-5 extended-spectrum beta-lactamase inKlebsiella pneumoniae strains isolated in Italy

Thirty-fiveKlebsiella pneumoniae strains isolated during 1993–1994 in intensive care units of a large Italian hospital were examined for the presence of extended-spectrum -lactamases. Five strains showed a high level of simultaneous resistance to -lactam agents, including ceftazidime and aztreonam, conferred by a large (130 kb) self-transferable plasmid (in 4 of 5 strains). Isoelectrofocusing and hybridisation studies suggest that these enzymes can be identified as SHV-5 extended-spectrum -lactamases. Pulsed-field gel electrophoresis analysis showed three different genomic fingerprinting profiles, while plasmid restriction enzyme digestion revealed three different patterns, demonstrating that the diffusion of SHV-5 -lactamase is not the result of a single strain or plasmid dissemination.     

临床分离肺炎链球菌的毒力基因及血清型分析

目的 了解肺炎链球菌的5种常见毒力基因(psaA、pspA、nanA、ply、lytA)在临床分离株中的分布情况.方法 以2006-2008年从临床分离133株肺炎链球菌为研究对象,采用PCR法对5种常见的毒力基因进行检测.结果 lytA、psaA、nanA、pspA、ply这5种基因在133株菌中的检测阳性率分别为94.7%、85.0%、84.2%、60.2%、82.7%;5种毒力基因在87株常见血清型菌中的阳性率分别为100%、87.4%、89.7%、67.8%、86.2%.结论 5种毒力基因在本地区肺炎链球菌中的阳性检测率均较高,在常见血清型菌株中的阳性检测率较其他血清型高.这5种基因是肺炎链球菌致病的主要毒力基因,可能作为新刑肺炎蛋白疫苗的候选基因.     

Characterization of in vitro-generated and clinical optochin-resistant strains of Streptococcus pneumoniae isolated from Argentina

Optochin susceptibility is a key test used for pneumococcal diagnosis, but optochin-resistant (Opt(r)) pneumococci have been reported in the last 2 decades. In this work, we characterized eight Opt(r) clinical strains which presented a new mutation, G47V, a predominant A49S mutation (recently reported in Brazil) and A49T. These mutations were found in the c subunit of the F(0)F(1) ATPase encoded by the atpC gene, and W206C was found in the a subunit encoded by the atpA gene. The Opt(r) clinical isolates were analyzed by BOX PCR, multilocus sequence typing, and serotype and antimicrobial resistance profiles, and they showed no epidemiological relationship. To characterize the Opt(r) mutations that could emerge among clinical strains, we studied a pool of spontaneous Opt(r) colonies obtained in vitro from the virulent D39 strain. We compared the atpAC mutations of these Opt(r) pneumococci (with or without passage through C57BL/6 mice) with those described in the clinical isolates. This analysis revealed three new mutations, G47V and L26M in the c subunit and L184S in the a subunit. Most of the mutations identified in the laboratory-generated Opt(r) strains were also found in clinical strains, with the exception of the L26M and L184S mutations, and we suppose that both mutations could emerge among invasive strains in the future. Considering that atpAC are essential genes, we propose that all spontaneous mutations that confer in vitro optochin resistance would not present severe physiological alterations in S. pneumoniae and may be carried by circulating pneumococcal strains.     

Identification of multidrug-resistant Streptococcus pneumoniae strains isolated in Poland by multilocus sequence typing

Multilocus sequence typing (MLST) of 35 isolates of multidrug-resistant Streptococcus pneumoniae recovered in Poland during 1995-1996 distinguished 10 different sequence types (ST). The majority of the isolates were assigned to two Polish clones of serotypes 6B and 23F, although the international clones, Spain23F-1 and Spain9V-3, were also identified. Similar results were obtained using pulsed-field gel electrophoresis (PFGE), providing a direct comparison of these two typing methods.     

Comparative activity of linezolid against staphylococci and enterococci isolated in Italy

The activity of linezolid, a new oxazolidinone, was tested against 862 Gram-positive cocci isolated in Italy and compared with the activities of 12 antibiotics. Overall, MIC₉₀s for linezolid (2–4 mg/L) indicated an in vitro activity comparable to that of vancomycin in methicillin-resistant Staphylococcus aureus (4 mg/L), S. epidermidis (2 mg/L) and methicillin-susceptible strains. Enterococcus faecalis strains were susceptible to linezolid (MIC₉₀ 2–4 mg/L), glycopeptides and β -lactams. In E. faecium , only glycopeptides (MIC₉₀ 2 mg/L) and linezolid (MIC₉₀ 2 mg/L) were active. Linezolid was the only drug active against two strains of Enterococcus showing a VanA phenotype. Owing to its antibacterial profile, linezolid represents a promising drug for the treatment of Gram-positive infections.     

Serotype profile and antibiotyping of Streptococcus pneumoniae strains isolated from nasal carriage in pediatric patients

The aim of this study was to determine the serotype profile and antibiotyping of Streptococcus pneumoniae from nasal isolates in children. Nasopharyngeal swab samples obtained from 125 children were cultivated and screened for the presence of S. pneumoniae. Strains were identified according to standard microbiological methods. The isolates were serotyped by the Quellung reaction and resistance patterns were determined by the microdilution method according to NCCLS guidelines. Results indicate an overall pneumococcal carriage rate of 24% (n = 30). The most commonly isolated serotypes were 23F (20%), 6B (20%) and 14 (13%). 73% of isolates were resistant at least to one of the tested antibiotics. 47% of the strains were consistently resistant to penicillin and the serotypes 6B and 23F were frequently associated with this marker. 60% of the strains were resistant to doxycycline, 37% to trimethoprim/sulfamethoxazole and clindamycin, 30% to erythromycin, 23% to cloramphenicol, 7% to ceftriaxone and 3% to cefepime. All strains were sensible to ofloxacin, rifampin and vancomycin. The most common combined resistance patterns were PNC-ERI-TMP/SMX-DOX-CLO-CLI (16.59%) and PNC-DOX (13.27%). The results obtained in this study will allow to orient the empiric therapy for pneumococcal infections and a rational use of antibiotics in clinical practice, as well as the application of an appropriate vaccination program specially adapted to the serotypes more frequently found in children.     

Comparative activities of 15 beta-lactam antibiotics against 590 strains of Klebsiella pneumoniae according to the production of beta-lactamase

In October 1988, all non repetitive strains of K. pneumoniae isolated in 17 hospitals have been studied. Among these 590 strains: 451 (76%) only produce the specific beta-lactamase of the species SHV-1 (pI 7,7) or SHV-1 type (pI 7,1), while 74 (12.5%) produce a TEM-1 or TEM-2 type beta-lactamase, and 65 (11%) an extended broad spectrum beta-lactamase: 22 CTX-1, 5 SHV-2, 4 SHV-3, 26 SHV-4, 8 SHV-5. The minimum inhibitory concentrations of the following antibiotics were performed by a liquid micro dilution technic: amoxicillin (AMX), amoxicillin + clavulanic acid (CL), 5 mg/l, ticarcillin (TIC), piperacillin (PIP), cefazolin (CEZ), cefamandole (CFM), cefoperazone (CFP), cefotaxime (CTX), cefotaxime + clavulanic acid 5 mg/l, cefotaxime + sulbactam (SUL) 5 mg/l, cefpirome (CPI), ceftazidime (CAZ), azthreonam (AZT), latamoxef (MOX), cefoxitin (FOX), cefotetan (CTT), temocillin (TMO), imipenem (IMI). The "wild" strains with SHV-1 beta-lactamase are resistant to AMX and have a decreased susceptibility to TIC and PIP, but are susceptible to other antibiotics. The TEM producing strains are more resistant to PIP and TIC, have a decreased susceptibility to CEZ and CFM but are susceptible to other antibiotics. For the extended broad-spectrum beta-lactamase producing strains, the MIC of penicillin antibiotics (AMX, TIC, PIP) are very high and also the MIC of CEZ, CFM and CFP. The MIC of CTX are higher for CTX-1 or SHV-4 producing strains, than for SHV-2, SHV-3, or SHV-5 producing strains. The combination with CL is more efficacious than the one with SUL to reduce the MIC of CTX in susceptibility area.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antibiotic susceptibility patterns and serotypes of antibiotic resistant and/or invasive Streptococcus pneumoniae strains circulating in Italy

Antibiotic susceptibility patterns and serotypes of 397 Streptococcus pneumoniae recovered from 1994 to 1998 in Italy have been determined. This collection included 229 penicillin- and/or erythromycin-resistant strains and 168 isolates responsible for invasive infections. Among penicillin-resistant pneumococci, the most prevalent serotype was 23F, followed by 19F and 9V, while among erythromycin-resistant but penicillin-susceptible strains serotype 6B was predominant followed by 19A, 14, 19F, 15A, 15B, and 23F. The most common invasive serotypes were 6B, 19F, 23F, 3, 4, 14, 20, 15B, and 9N. The currently available 23-valent pneumococcal vaccine could cover 91% of noninvasive penicillin- and/or erythromycin-resistant strains, 84% of pneumococci isolated from sterile sites, and 83% of invasive antibiotic-resistant S. pneumoniae. Penicillin-resistant pneumococci also showed reduced susceptibility to other antimicrobial compounds. Against invasive pneumococci, amoxicillin, cefotaxime, ceftriaxone, imipenem, vancomycin, and rifampin were 100% effective. Penicillin, chloramphenicol, erythromycin, tetracycline, and co-trimoxazole resistance was 1.8%, 9.5%, 15.5%, 18.5%, and 21.4%, respectively.     

Comparative efficacy of pneumococcal neuraminidase and pneumolysin as immunogens protective against Streptococcus pneumoniae

Neuraminidase and pneumolysin were purified from cultures of Streptococcus pneumoniae and used, either singly or in combination, to immunize juvenile mice which were subsequently challenged intranasally with virulent S. pneumoniae. In each of two independent trials, a small but significant (P less than 0.05) increase in survival time (compared with that of non-immunized mice) was observed in groups which had been immunized with neuraminidase, but only if the enzyme had been pre-treated with 3.4% (v/v) formaldehyde. The median extension in survival time was significantly less (P less than 0.01) than that of mice which had been immunized with pneumolysin alone. The median survival time for mice which had received both formaldehyde-treated neuraminidase and pneumolysin was not significantly different from that of mice which had received pneumolysin alone. While these findings provide direct evidence that neuraminidase contributes to the pathogenicity of the pneumococcus in mice, they suggest that this protein may be of less value than pneumolysin as a vaccine component in the present experimental model.     

Streptococcus pneumoniae meningitis in Amiens Hospital between 1990 and 2005. Bacteriological characteristics of strains isolated

Streptococcus pneumoniae is actually the first most likely organism to cause meningitis in children 2 months to 2 years old and in adults older than 65 years. From January 1990 to December 2005, 72 cases of S. pneumoniae-positive cerebrospinal fluid culture were indexed in our hospital. Among the 72 cases, 25 came from children, and 60% of these came from children under two years of age and 47 came from adults whose the mean age was 55 years. The first penicillin-resistant S. pneumoniae (PNSP) meningitis was identified in 1993. The susceptibility to penicillin of pneumococcal isolates causing meningitis varied according to time; until 1995, 25% of the strains were PNSP, then from 1996 to 2005, 50% of strains were PNSP. The overall prevalence of non-susceptible was 34.7% (25/72). Among the 25 PNSP, 21 were intermediate to penicillin G and four of them were resistant. Among children, seven PNSP meningitis were indexed and one of them was resistant. The antimicrobial MICs of amoxicillin and cefotaxim varied from 0.064 to 1 mg/l and from 0.016 to 0.5 mg/l respectively. Among adults, 18 PNSP meningitis were indexed. Three strains were penicillin-resistant. The antimicrobial MICs of amoxicillin varied from 0.064 to 2 mg/l. Nine strains of 18 PNSP had cefotaxim MIC>/=0.5 mg/l and, four of them had MIC 1 mg/l. None amoxicillin and cefotaxim-resistant strain was isolated. Serotyping of all strains was performed in the Reference Center. Serotypes 6B, 9V and 19 were the most frequent in child and serotypes 6B, 23F, 19, 9, 4 were the most frequent in adult. So, all serotypes were represented.     

Comparison of in vitro activities of tigecycline with other antimicrobial agents against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in Taiwan

We compared the in vitro activities of tigecycline to those of other agents against 300 nonduplicate isolates of Streptococcus pneumoniae (194 isolates), Haemophilus influenzae (60 isolates), and Moraxella catarrhalis (46 isolates) recovered from patients treated in three major hospitals in Taiwan from August through December, 2003. All of these isolates were inhibited at 0.5 mg/L of tigecycline. For S. pneumoniae isolates, 72% were not susceptible to penicillin (69% intermediate and 3% resistant) and 96% were not susceptible to azithromycin. Among the 178 isolates resistant to azithromycin, 53 isolates (30%) had the M phenotype and 70% had the cMLSB phenotype. The rate of nonsusceptibility to ertapenem, telithromycin, moxifloxacin, and quinupristindalfopristin in S. pneumoniae was 3%, 2%, 1%, and 57%, respectively. For H. influenzae, 36 (60%) were not susceptible to ampicillin, among which 31 possessed beta-lactamase. A high rate (8.3%) of H. influenzae isolates with beta-lactamase-negative and ampicillin-resistant phenotype was found. All H. influenzae isolates were susceptible to azithromycin, but 40% of them were not susceptible to clarithromycin. Ninety-eight percent (44 isolates) of M. catarrhalis possessed beta-lactamase. All three fluoroquinolones tested were highly active (MIC90 < or =0.12 mg/L) against H. influenzae and M. catarrhalis.     

Comparative in vitro activity of penicillin G, levofloxacin, moxifloxacin, telithromycin, pristinamycin, quinupristin–dalfopristin and linezolid against ofloxacin-intermediate and -resistant Streptococcus pneumoniae

Screening by ofloxacin disk was carried out on 1158 strains of Streptococcus pneumoniae in order to investigate the in vitro bacteriostatic activity of penicillin G, levofloxacin, moxifloxacin, telithromycin, linezolid, pristinamycin and quinupristin–dalfopristin against ofloxacin-intermediate and -resistant S. pneumoniae strains. It was concluded that these new antimicrobial agents could be useful for the treatment of pneumococcal infections caused by penicillin-sensitive and -resistant S. pneumoniae , and would represent a valid therapeutic option for patients allergic to β -lactams, should they prove to be potent in vivo.