Genetic characterization of fluoroquinolone-resistant Streptococcus pneumoniae strains isolated during ciprofloxacin therapy from a patient with bronchiectasis

Technetium-99m Tricarbonyl Labeled a Broad-spectrum Quinolone as a Specific Imaging Agent in Infection Diseases

Nuclear medicine imaging has been used to localize infection sites, and efforts have been continued to develop modified infection specific radiopharmaceuticals. In this study gemifloxacin as a broad-spectrum quinolone has been labeled with [^99mTc (CO)₃ (H₂O)₃]⁺ core in order to evaluate its feasibility as an infection imaging agent for in-vivo use. The stability of radioconjugate was checked in human serum at 37 °C and biodistribution was studied in mice. Labeling yield of > 95% was obtained corresponding to a specific activity of 0.14 GBq/μmol. The radioconjugate showed good stability in human serum. Our main achievement was the high accumulation in the infected muscle in mice (T/NT = 2.93 ± 0.3 at 1 h post injection), which may diagnostically be beneficial for differentiate sites of infection from sites of inflammation.

Infectious etiology of acute exacerbations in severe COPD patients

OBJECTIVES

Since the new GOLD guidelines were implemented no data have been published about the etiology of acute exacerbations (AECOPD) in severe COPD patients with a different frequency of annual episodes.

METHODS

One hundred and eleven COPD patients (FEV1 < 50%) were prospectively followed up for a year. Good-quality sputum samples recovered during AECOPD were processed, including quantitative culture and PCR detection of atypical bacteria.

RESULTS

A total of 188 sputum samples were obtained from AECOPD episodes. Forty patients had a single episode, and 71 patients had ≥2. In 128 episodes a single pathogen was isolated, while 42 episodes were polymicrobial (≥2 pathogens). Overall, the most frequent pathogen isolated was Pseudomonas aeruginosa (n = 54), followed by Haemophilus influenzae (n = 37), Streptococcus pneumoniae (n = 31), Moraxella catarrhalis (n = 29) and Staphylococcus aureus (n = 12). P. aeruginosa was the most frequent in both groups of patients (35% and 27% in those with 1 and ≥2 AECOPD, respectively). H. influenzae was associated with patients with a single annual AECOPD (33% vs. 16%; P = 0.006), while Enterobacteriaceae were associated with frequent exacerbators (0% vs. 12%; P < 0.044).

CONCLUSION

Overall, P. aeruginosa was the most frequent pathogen isolated from exacerbations. However, different bacterial etiology was observed depending on the number of annual episodes.

Some pneumococcal serotypes are more frequently associated with relapses of acute exacerbations in COPD patients

OBJECTIVES

To analyze the role of the capsular type in pneumococci causing relapse and reinfection episodes of acute exacerbation in COPD patients.

METHODS

A total of 79 patients with 116 recurrent episodes of acute exacerbations caused by S. pneumoniae were included into this study (1995-2010). A relapse episode was considered when two consecutive episodes were caused by the same strain (identical serotype and genotype); otherwise it was considered reinfection. Antimicrobial susceptibility testing (microdilution), serotyping (PCR, Quellung) and molecular typing (PFGE/MLST) were performed.

RESULTS

Among 116 recurrent episodes, 81 (69.8%) were reinfections, caused by the acquisition of a new pneumococcus, and 35 (30.2%) were relapses, caused by a pre-existing strain. Four serotypes (9V, 19F, 15A and 11A) caused the majority (60.0%) of relapses. When serotypes causing relapses and reinfection were compared, only two serotypes were associated with relapses: 9V (OR 8.0; 95% CI, 1.34-85.59) and 19F (OR 16.1; 95% CI, 1.84-767.20). Pneumococci isolated from relapses were more resistant to antimicrobials than those isolated from the reinfection episodes: penicillin (74.3% vs. 34.6%, p<0.001), ciprofloxacin (25.7% vs. 9.9%, p<0.027), levofloxacin (22.9% vs. 7.4%, p = 0.029), and co-trimoxazole (54.3% vs. 25.9%, p<0.001).

CONCLUSIONS

Although the acquisition of a new S. pneumoniae strain was the most frequent cause of recurrences, a third of the recurrent episodes were caused by a pre-existing strain. These relapse episodes were mainly caused by serotypes 9V and 19F, suggesting an important role for capsular type.

Pneumococci can persistently colonize adult patients with chronic respiratory disease

Streptococcus pneumoniae plays an important role in causing acute exacerbations in patients with chronic respiratory disease. However, few data are available regarding pneumococcal persistence in adult patients with chronic respiratory diseases. Fifty pneumococci recovered from sputum samples (1995 to 2010) from 13 adult patients with ≥ 3 episodes of acute exacerbation or pneumonia, with the same serotype and pulsed-field gel electrophoresis (PFGE) pattern, were studied. Multilocus sequence typing (MLST) loci, penicillin-binding protein (PBP) genes (pbp2x, pbp1a, pbp2b), and the quinolone-resistant determining regions (QRDRs) of parC, parE, and gyrA were PCR amplified and sequenced. The average time between the first and last episode was 582 days (standard deviation [SD], ± 362). All but two patients received multiple courses of β-lactam treatment, and all persistent strains were resistant to penicillin; however, the PBP sequences were stable over time apart from one variable nucleotide in pbp2x, observed among pneumococci isolated from three patients. In contrast, 7/11 patients treated with fluoroquinolones had fluoroquinolone-resistant pneumococci. In three patients, the initially fluoroquinolone-susceptible strain developed resistance after fluoroquinolone therapy, and in the remaining four patients, the persistent strain was fluoroquinolone resistant from the first episode. QRDR changes involved in fluoroquinolone resistance were frequently observed in persistent strains after fluoroquinolone treatment; however, the PBP sequences and MLST genotypes of these strains were stable over time.

Clonal spread of levofloxacin-resistant streptococcus pneumoniae invasive isolates in Madrid, Spain, 2007 to 2009

Among 1,349 Streptococcus pneumoniae invasive isolates, 45 (3.3%) were levofloxacin resistant. Serotype distribution was as follows: 8 (n=32 isolates), 19A (n=4 isolates), 7F (n=3 isolates), 9V (n=2 isolates), 10A (n=1 isolate), 19F (n=1 isolate), 6B (n=1 isolate), and nontypeable (n=1 isolate). Levofloxacin-resistant isolates had dual mutations in the gyrA and parC genes. Serotype 8 strains corresponded to a capsular switching of the Sweden(15A)-25 clone. Levofloxacin resistance was also detected among multiresistant (ST276(19A), Spain9V-ST156, ST88(19F), and ST1542(6B)) and among usually antibiotic-susceptible (Netherlands7F-ST191, ST1201(19A), and ST2639(10A)) clones.

Changes in fluoroquinolone-resistant Streptococcus pneumoniae after 7-valent conjugate vaccination, Spain

Among 4,215 Streptococcus pneumoniae isolates obtained in Spain during 2006, 98 (2.3%) were ciprofloxacin resistant (3.6% from adults and 0.14% from children). In comparison with findings from a 2002 study, global resistance remained stable. Low-level resistance (30 isolates with MIC 4-8 microg/mL) was caused by a reserpine-sensitive efflux phenotype (n = 4) or single topoisomerase IV (parC [n = 24] or parE [n = 1]) changes. One isolate did not show reserpine-sensitive efflux or mutations. High-level resistance (68 isolates with MIC >or=16 microg/mL) was caused by changes in gyrase (gyrA) and parC or parE. New changes in parC (S80P) and gyrA (S81V, E85G) were shown to be involved in resistance by genetic transformation. Although 49 genotypes were observed, clones Spain9V-ST156 and Sweden15A-ST63 accounted for 34.7% of drug-resistant isolates. In comparison with findings from the 2002 study, clones Spain14-ST17, Spain23F-ST81, and ST8819F decreased and 4 new genotypes (ST9710A, ST57016, ST43322, and ST71733) appeared in 2006.

Fitness of Streptococcus pneumoniae fluoroquinolone-resistant strains with topoisomerase IV recombinant genes

The low prevalence of ciprofloxacin-resistant (Cp r) Streptococcus pneumoniae isolates carrying recombinant topoisomerase IV genes could be attributed to a fitness cost imposed by the horizontal transfer, which often implies the acquisition of larger-than-normal parE-parC intergenic regions. A study of the transcription of these genes and of the fitness cost for 24 isogenic Cp r strains was performed. Six first-level transformants were obtained either with PCR products containing the parC quinolone resistance-determining regions (QRDRs) of S. pneumoniae Cp r mutants with point mutations or with a PCR product that includes parE-QRDR-ant-parC-QRDR from a Cp r Streptococcus mitis isolate. The latter yielded two strains, T6 and T11, carrying parC-QRDR and parE-QRDR-ant-parC-QRDR, respectively. These first-level transformants were used as recipients in further transformations with the gyrA-QRDR PCR products to obtain 18 second-level transformants. In addition, strain Tr7 (which contains the GyrA E85K change) was used. Reverse transcription-PCR experiments showed that parE and parC were cotranscribed in R6, T6, and T11; and a single promoter located upstream of parE was identified in R6 by primer extension. The fitness of the transformants was estimated by pairwise competition with R6 in both one-cycle and two-cycle experiments. In the one-cycle experiments, most strains carrying the GyrA E85K change showed a fitness cost; the exception was recombinant T14. In the two-cycle experiments, a fitness cost was observed in most first-level transformants carrying the ParC changes S79F, S79Y, and D83Y and the GyrA E85K change; the exceptions were recombinants T6 and T11. The results suggest that there is no impediment due to a fitness cost for the spread of recombinant Cp r S. pneumoniae isolates, since some recombinants (T6, T11, and T14) exhibited an ability to compensate for the cost.

Should patients with acute exacerbation of chronic bronchitis be treated with antibiotics? Advantages of the use of fluoroquinolones

The pathological changes in chronic bronchitis (CB) produce airflow obstruction, reduce the effectiveness of the mucocilliary drainage system and lead to bacterial colonisation of bronchial secretion. The presence of bacteria induces an inflammatory response mediated by leukocytes. There is a direct relationship between the degree of impairment of the mucocilliary drainage system, the density of bacteria in mucus and the number of leukocytes in the sputum. Purulent sputum is a good marker of a high bacterial load. Eventually, if the number of leukocytes is high, their normal activity could decrease the effectiveness of the drainage system, increase the bronchial obstruction and probably damage the lung parenchyma. Whenever the density of bacteria in the bronchial lumen is >or=10(6) CFU/mL, there is a high probability that the degree of inflammatory response will lead to a vicious cycle which in turn tends to sustain the process. This situation can arise during the clinical course of any acute exacerbation of CB, independently of its aetiology, provided the episode is sufficiently severe and/or prolonged. Fluoroquinolones of the third and fourth generation are bactericidal against most microorganisms usually related to acute exacerbations of CB. Their diffusion to bronchial mucus is adequate. When used in short (5-day) treatment they reduce the bacterial load in a higher proportion than is achieved by beta-lactam or macrolide antibiotics given orally. Although the clinical cure rate is similar to that obtained with other antibiotics, the time between exacerbations could be increased.

[Failure of levofloxacin therapy in two cases of community-acquired pneumonia caused by fluoroquinolone-resistant Streptococcus pneumoniae and complicated with empyema]

BACKGROUND

Community acquired pneumonia (CAP) due to Streptococcus pneumoniae is a frequent cause of morbidity and mortality. We communicate two cases of CAP with complications. In both cases levofloxacin-resistant S. pneumoniae was isolated in pleural effusion. Patient 1: A 51-year-old man who had not received previous treatment with quinolones was admitted to the hospital for CAP and initially treated with levofloxacin (500 mg/24h iv). Four days later pleural effusion developed and fluid culture isolated levofloxacin-resistant S. pneumoniae (MIC > 32 .g/ml). The outcome was favorable following chest tube placement and treatment with beta-lactam antibiotics. Patient 2: A 73-year-old man with a history of chronic obstructive pulmonary disease was admitted due to CAP and was initially treated with levofloxacin (500 mg/24 h iv). He was transferred to our hospital after 10 days of treatment with this antibiotic, following the development of pleural effusion with isolation of levofloxacin-resistant S. pneumoniae (MIC = 12 .g/ml). The patient was treated with chest tube placement and beta-lactam antibiotics with a favorable outcome.

CONCLUSIONS

Patients with CAP treated empirically must be closely followed, both clinically and radiologically, to facilitate early detection of complications due to bacterial resistance to the prescribed antibiotic. Patients with CAP who have received quinolones in the weeks before the development of pneumonia should not been treated empirically with these antibiotics because of the risk of resistance development.

In vivo development of high-level fluoroquinolone resistance in Streptococcus pneumoniae in chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease are generally subjected to multiple regimens of antimicrobial treatment. The development of high-level levofloxacin resistance (i.e., a minimum inhibitory concentration >8 mu g/mL) in 8 patients whose previous pneumococcal isolates showed susceptibility is described. Molecular methods were used to characterize the strains and to study the sequential changes in fluoroquinolone targets.

Nonresponses and treatment failures with conventional empiric regimens in patients with community-acquired pneumonia

Although most patients with suspected CAP respond to empiric therapy,a small number of patients do not respond in the expected fashion. Age and underlying comorbid conditions have a strong influence on the course of illness. Less common causes of treatment failures include overwhelming infection, antimicrobial resistance, and misdiagnosis. It is a common practice for empiric antimicrobial treatment of CAP to be initiated without microbiologic studies. Clinicians carefully should observe these patients for unusual or slow responses and should be ready to pursue a more extensive search for the cause of treatment failure.

Fluoroquinolone resistance in penicillin-resistant Streptococcus pneumoniae clones, Spain

Among 2,882 Streptococcus pneumoniae sent to the Spanish Reference Laboratory during 2002, 75 (2.6%) were ciprofloxacin-resistant. Resistance was associated with older patients (3.9% in adults and 7.2% in patients > or =65 years of age), with isolation from noninvasive sites (4.3% vs. 1.0%), and with penicillin and macrolide resistance. Among 14 low-level resistant (MIC 4-8 microg/mL) strains, 1 had a fluoroquinolone efflux phenotype, and 13 showed single ParC changes. The 61 high-level ciprofloxacin-resistant (MIC > or =16 microg/mL) strains showed either two or three changes at ParC, ParE, and GyrA. Resistance was acquired either by point mutation (70 strains) or by recombination with viridans streptococci (4 strains) at the topoisomerase II genes. Although 36 pulsed-field gel electrophoresis patterns were observed, 5 international multiresistant clones (Spain23F-1, Spain6B-2, Spain9V-3, Spain14-5 and Sweden15A-25) accounted for 35 (46.7%) of the ciprofloxacin-resistant strains. Continuous surveillance is needed to prevent the dissemination of these clones.

Fluoroquinolone and macrolide treatment failure in pneumococcal pneumonia and selection of multidrug-resistant isolates

Streptococcus pneumoniae serotype 3, isolated from a penicillin-allergic patient and initially susceptible to fluoroquinolones, macrolides, lincosamides, quinupristin-dalfopristin, and telithromycin, became resistant to all these drugs during treatment. Mutations in the parC and gyrA and in the 23S rRNA and the ribosomal protein L22 genes were detected in the resistant isolates.

The epidemiology of antibiotic resistance in Streptococcus pneumoniae and the clinical relevance of resistance to cephalosporins, macrolides and quinolones

Invasive non-meningeal pneumococcal infections remain a major cause of morbidity and mortality worldwide. The factors affecting the epidemiology and mortality of pneumococcal infections are discussed. The increase and spread of resistance to antimicrobial agents among pneumococci is a cause of concern to the clinician. There are links between the usage of antibacterial agents and the development of resistance. Resistance to penicillin and other beta-lactams has become widespread but this does not appear to have decreased the efficacy of some of these agents against non-meningeal infections. There is evidence that the good pharmacokinetic and pharmacodynamic features of the third generation cephalosporins (cefotaxime and ceftriaxone) contribute to their efficacy in vivo. New breakpoints for cefotaxime and ceftriaxone against non-meningeal pneumococcal isolates were proposed by the National Committee for Clinical Laboratory Standard (NCCLS, US), based on the clinical evidence of the efficacy of these drugs. In contrast there is increasing evidence that resistance to macrolides can lead to a poor clinical response. Fluoroquinolones have been widely used to treat respiratory tract infections among others, and pneumococcal resistance to these agents in vitro, although currently low, is increasing. There are reports that resistance to fluoroquinolones can develop during treatment and may be reflected in a lack of clinical response. Several clinical and epidemiological variables (e.g. prior antibiotic use) can be useful to identify patients at risk from infections with antibiotic-resistant pneumococci. These patients would be those who would benefit the most from a pneumococcal vaccination programme.

Antimicrobial susceptibility and serotype distribution of Streptococcus pneumoniae and molecular characterization of multidrug-resistant serotype 19F, 6B, and 23F Pneumococci in northern Thailand

Penicillin-resistant Streptococcus pneumoniae is widely spread worldwide. Our study was undertaken to examine the susceptibility and serotypes of S. pneumoniae in northern Thailand. Ninety-three S. pneumoniae strains were isolated from 93 patients at Chiang Mai University Hospital, Chiang Mai, Thailand, from September 1999 to June 2000. The strains were isolated from sputum (n = 51), blood (n = 15), nasopharynges (n = 14), and other sources (e.g., pus, ears, ascites, and cerebrospinal fluid) (n = 13). Of the 93 isolates, 29 (31.2%) were susceptible, 24 (25.8%) showed intermediate resistance (MIC, 0.12 to 1.0 micro g/ml), and 40 (43.0%) were fully resistant (MIC, >/=2.0 micro g/ml) to penicillin G. Seven (46.7%) from blood, 5 (35.7%) from nasopharynges, 15 (29.4%) from sputum, and 2 (15.4%) from other sources were susceptible isolates. Serotyping with the use of antiserum revealed differences in the predominant types that were susceptible (6A, 11A, and 19A), intermediately resistant (6B and 23F), and fully resistant (6B, 19F, and 23F). Molecular typing by pulsed-field gel electrophoresis of multidrug-resistant pneumococci showed four patterns (A, B, C, and D) for 16 isolates of serotype 19F, with pattern B being predominant (12 isolates). This finding was different from that with the Taiwan multidrug-resistant serotype 19F clone. Eleven isolates of serotype 6B all showed pattern E, and nine isolates of serotype 23F showed two patterns (F and G), with pattern F being predominant (seven isolates). This finding was similar to that with the Spanish multidrug-resistant serotype 23F clone. Our results indicated that the resistance of pneumococci to antibiotics in northern Thailand is progressing rapidly and that effort should be intensified to prevent any spread of pandemic multidrug-resistant serotypes 19F, 6B, and 23F.