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PubMed2006

Antimicrobial susceptibility, serotype and genotype distribution of meningococci in Portugal, 2001-2002.

One hundred and eighteen Neisseria meningitidis isolates were recovered from patients with invasive meningococcal disease in Portugal, over one year. Our study was undertaken to evaluate antimicrobial susceptibility, serogroup, serotype and genotype of isolates. One quarter (24.6%) of the isolates showed moderate resistance to penicillin and 47.4% were resistant to sulphadiazine. The two most common serosubtypes were C:2b:P1.5,2 (31.3%) and B:4:P1.15 (3.4%). Half (53.6%) of the isolates with moderate resistance to penicillin were phenotype C:2b:P1.5,2 (n=14), C:2b:P1.2 (n=1) or C:2b:NST (n=1); Pulsed-field gel electrophoresis (PFGE) showed that all these isolates were genetically related. Multilocus sequence typing (MLST) analysis of representative clones from each PFGE pattern showed the predominance of the ST-8 complex/cluster A4 among N. meningitidis with moderate resistance to penicillin. This clonal complex has been principally found in Southern Europe. The apparent emergence and dissemination of the hypervirulent ST-8 complex/cluster A4 among serogroup C strains increases the need for a continued surveillance of antimicrobial susceptibility of meningococci and of genotypic markers in Portugal.

Anti-Infective Agents↗

PubMed2003

Infections by Neisseria meningitidis serogroup X in Spain.

We describe an atypical presentation of bacteremia caused by N. meningitidis serogroup X. By multilocus sequence typing the isolate was characterized to the sequence type 2139, which is not related with the clonal complex recently isolated in Africa. Since 1984, only six cases of serogroup X N. meningitidis infections have been diagnosed in Spain. Nevertheless, after the application of the conjugated vaccine, attention should be paid to the emergence of infections caused by unusual serogroups of N. meningitidis.

Anti-Bacterial Agents↗

PubMed2005

Necrotizing fasciitis caused by community-associated methicillin-resistant Staphylococcus aureus in Los Angeles.

BACKGROUND: Necrotizing fasciitis is a life-threatening infection requiring urgent surgical and medical therapy. Staphylococcus aureus has been a very uncommon cause of necrotizing fasciitis, but we have recently noted an alarming number of these infections caused by community-associated methicillin-resistant S. aureus (MRSA). METHODS: We reviewed the records of 843 patients whose wound cultures grew MRSA at our center from January 15, 2003, to April 15, 2004. Among this cohort, 14 were identified as patients presenting from the community with clinical and intraoperative findings of necrotizing fasciitis, necrotizing myositis, or both. RESULTS: The median age of the patients was 46 years (range, 28 to 68), and 71 percent were men. Coexisting conditions or risk factors included current or past injection-drug use (43 percent); previous MRSA infection, diabetes, and chronic hepatitis C (21 percent each); and cancer and human immunodeficiency virus infection or the acquired immunodeficiency syndrome (7 percent each). Four patients (29 percent) had no serious coexisting conditions or risk factors. All patients received combined medical and surgical therapy, and none died, but they had serious complications, including the need for reconstructive surgery and prolonged stay in the intensive care unit. Wound cultures were monomicrobial for MRSA in 86 percent, and 40 percent of patients (4 of 10) for whom blood cultures were obtained had positive results. All MRSA isolates were susceptible in vitro to clindamycin, trimethoprim-sulfamethoxazole, and rifampin. All recovered isolates belonged to the same genotype (multilocus sequence type ST8, pulsed-field type USA300, and staphylococcal cassette chromosome mec type IV [SCCmecIV]) and carried the Panton-Valentine leukocidin (pvl), lukD, and lukE genes, but no other toxin genes were detected. CONCLUSIONS: Necrotizing fasciitis caused by community-associated MRSA is an emerging clinical entity. In areas in which community-associated MRSA infection is endemic, empirical treatment of suspected necrotizing fasciitis should include antibiotics predictably active against this pathogen.

Adult↗

PubMed2002

The evolutionary history of methicillin-resistant Staphylococcus aureus (MRSA).

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospital-acquired infections that are becoming increasingly difficult to combat because of emerging resistance to all current antibiotic classes. The evolutionary origins of MRSA are poorly understood, no rational nomenclature exists, and there is no consensus on the number of major MRSA clones or the relatedness of clones described from different countries. We resolve all of these issues and provide a more thorough and precise analysis of the evolution of MRSA clones than has previously been possible. Using multilocus sequence typing and an algorithm, BURST, we analyzed an international collection of 912 MRSA and methicillin-susceptible S. aureus (MSSA) isolates. We identified 11 major MRSA clones within five groups of related genotypes. The putative ancestral genotype of each group and the most parsimonious patterns of descent of isolates from each ancestor were inferred by using BURST, which, together with analysis of the methicillin resistance genes, established the likely evolutionary origins of each major MRSA clone, the genotype of the original MRSA clone and its MSSA progenitor, and the extent of acquisition and horizontal movement of the methicillin resistance genes. Major MRSA clones have arisen repeatedly from successful epidemic MSSA strains, and isolates with decreased susceptibility to vancomycin, the antibiotic of last resort, are arising from some of these major MRSA clones, highlighting a depressing progression of increasing drug resistance within a small number of ecologically successful S. aureus genotypes.

Alleles↗

PubMed2003

Subtyping of Mycoplasma pneumoniae isolates based on extended genome sequencing and on expression profiles.

Mycoplasma pneumoniae isolates from patients, collected over a period of 12 years in Germany, were characterized by various methods (parameters) including multilocus sequence typing, restriction fragment length polymorphisms, Western blotting with mono-specific antibodies directed against selected proteins or with polyspecific antibodies directed against the Triton X-114-soluble protein fraction, and two-dimensional gel electrophoresis. The results for 91 isolates from Germany, which were complemented with 14 isolates from the USA and 10 isolates from France, clearly showed that M. pneumoniae is a highly uniform species and that most of the isolates could be assigned to one of the two subtypes 1 and 2. The members of one subtype differ from the other with respect to the sequence of the P1 gene, the ORF6 gene, the P65 gene, and by a typical DNA restriction fragment pattern. We observed four isolates (variants), which seemed identical by the above mentioned criteria, but did not belong to either one of the two subtypes. They showed most of the subtype 2-specific features, but differed in the sequence of the P1 gene and showed a variation in the restriction fragment pattern. The appearance of subtype 1 or 2 over the last 12 years in Germany showed a dominance of subtype 1 between 1989 and 1996 and a dominance of subtype 2 between 1997 and 1998. The variant (neither subtype 1 nor subtype 2) was only detected in 1991 and 1995 but it had no epidemiological consequences.

Adhesins, Bacterial↗

PubMed2001

Clones of Streptococcus pneumoniae isolated from nasopharyngeal carriage and invasive disease in young children in central Tennessee.

To determine whether nasopharyngeal carriage isolates of Streptococcus pneumoniae are of the same genetic background as isolates that caused invasive disease in one community, IS1167 and boxA genotypes were obtained for 182 pneumococcal isolates from children living in central Tennessee. The isolates represented 70 combined IS1167-boxA genotypes. The genotypic diversity of the invasive isolates was significantly less than that of the total population (P=.003). Most of the carriage isolates belonged to genotypes unique to carriage, whereas most of the invasive isolates belonged to genotypes common to carriage and disease (P=.02). Monte Carlo simulations showed a greater number of genotypes unique to carriage than can be explained by chance (P<.05 in all cases). Two genotypes were identified by multilocus sequence typing as members of globally disseminated clones, and one such genotype that was strictly carriage in this sample caused disease in other studies. Thus, clones can have different propensities for carriage and invasion.

Bacterial Capsules↗

PubMed2002

Prospective study of a serogroup X Neisseria meningitidis outbreak in northern Ghana.

After an epidemic of serogroup A meningococcal meningitis in northern Ghana, a gradual disappearance of the epidemic strain was observed in a series of five 6-month carriage surveys of 37 randomly selected households. As serogroup A Neisseria meningitidis carriage decreased, an epidemic of serogroup X meningococcal carriage occurred, which reached 18% (53/298) of the people sampled during the dry season of 2000, coinciding with an outbreak of serogroup X disease. These carriage patterns were unrelated to that of Neisseria lactamica. Multilocus sequence typing and pulsed-field gel electrophoresis of the serogroup X bacteria revealed strong similarity with other strains isolated in Africa during recent decades. Three closely related clusters with distinct patterns of spread were identified among the Ghanian isolates, and further microevolution occurred after they arrived in the district. The occurrence of serogroup X outbreaks argues for the inclusion of this serogroup into a multivalent conjugate vaccine against N. meningitidis.

Adolescent↗

PubMed2003

Dynamics of the penA gene in serogroup C meningococcal strains.

The transpeptidase encoding region of the penA gene was sequenced in 44 meningococcal strains (41 serogroup C [23 characterized as serotype 2b and 18 as serotype 2a] and 3 serogroup B [B:2b:P1.2,5]). All strains were characterized by multilocus sequence typing and were determined to be susceptible or intermediate resistant to penicillin (Pen(s) or Pen(i), respectively). A high degree of homology was found among the penA alleles identified in the Pen(s) strains. All the Pen(i) C:2b strains, which belonged to 2 different clonal complexes, showed the same penA gene allele. This fact suggests that 1 of the clonal complexes acquired that allele, spreading it to the other by horizontal transfer. The same allele also was found in the B:2b strains studied, indicating that 1 of the Pen(i) C:2b strains underwent a capsular switching event. A different mosaic penA allele was identified in the Pen(i) C:2a strains, which belonged to the ET37 cluster.

Alleles↗

PubMed2003

Clonal relationships between invasive and carriage Streptococcus pneumoniae and serotype- and clone-specific differences in invasive disease potential.

By use of multilocus sequence typing, Streptococcus pneumoniae isolates causing invasive disease (n=150) were compared with those from nasopharyngeal carriage (n=351) among children in Oxford. The prevalence of individual clones (sequence types) and serotypes among isolates from invasive disease was related to their prevalence in carriage, and an odds ratio (OR) for invasive disease was calculated for the major clones and serotypes. All major carried clones and serotypes caused invasive disease, although their ability to do so varied greatly. Thus, 2 serotype 14 clones were approximately 10-fold overrepresented among disease isolates, compared with carriage isolates, whereas a serotype 3 clone was approximately 10-fold underrepresented. The lack of heterogeneity between the ORs of different clones of the same serotype, and analysis of isolates of the same genotype, but different serotype, suggested that capsular serotype may be more important than genotype in the ability of pneumococci to cause invasive disease.

Carrier State↗

PubMed2003

Epidemiology of acute otitis media caused by Streptococcus pneumoniae before and after licensure of the 7-valent pneumococcal protein conjugate vaccine.

We studied, by pulsed-field gel electrophoresis, multilocus sequence typing and penicillin-binding protein 2b amplicon-restriction profiles, pneumococcal isolates recovered from children with acute otitis media during 1 January-31 December 1999 and 2001. The proportion of nonvaccine serogroups increased from 14.8% (13/88) to 36.5% (23/63) from 1999 to 2001 (P<.01). Among children who received at least 2 doses of the pneumococcal 7-valent protein conjugate (PNC7) vaccine, 46.7% (7/15) of the isolates had nonvaccine serogroups, compared with 20.8% (26/125) of the isolates from children who did not receive the PNC7 vaccine (P=.05). Overall, the serogroups involved in capsular switching were 6-19-NT, 6-14-35, 15-19, and the 19-Spanish 23F clone. In 1999 and 2001, 30.8% (4/13) and 26.1% (6/23) of the nonvaccine serogroups were implicated in capsular switching, respectively. Continued surveillance will be of great importance as the distribution of the PNC7 vaccine increases.

Acute Disease↗

PubMed2004

Evolution of erythromycin-resistant Streptococcus pneumoniae from Asian countries that contains erm(B) and mef(A) genes.

To investigate the genetic characteristics of erythromycin-resistant Streptococcus pneumoniae in Asian countries, 110 pneumococcal isolates were analyzed by multilocus sequence typing (MLST). MLST analysis showed that 2 clonal complexes--CC236 (Taiwan19F-14 clone) and CC81 (Spain23F-1 clone)--are the major lineages of erythromycin-resistant S. pneumoniae in the Asian region. Pneumococcal isolates containing both the erm(B) and the mef(A) genes are thought to have originated from the Taiwan19F-14 clone containing the mef(A) gene, after introduction of the erm(B) gene. Further evolution of this variant clone has generated resistant strains with different sequence types. Dissemination of these variant clones of the Taiwan19F-14 could be the main reason for the high frequency of pneumococcal isolates containing both erm(B) and mef(A) in some Asian countries. Data suggest that the high prevalence of erythromycin-resistant S. pneumoniae in the Asian region is partly due to the clonal spread of a few multidrug-resistant clones.

Asia↗

PubMed2004

An outbreak of conjunctivitis due to a novel unencapsulated Streptococcus pneumoniae among military trainees.

BACKGROUND: Bacterial conjunctivitis usually occurs as sporadic cases; outbreaks are uncommon and usually are associated with school campuses. We report an outbreak of Streptococcus pneumoniae conjunctivitis at a military training facility. METHODS: An outbreak investigation was done. Each case of conjunctivitis was evaluated with an assessment tool including demographic and clinical data. Conjunctival swabs were obtained. Pneumococci underwent standard testing, including serotyping with the Quellung reaction, capsular staining, and multilocus sequence typing. Sequence types were compared with previous reported outbreak strains by construction of dendrograms. Carriage rates of S. pneumoniae were determined among previously undiagnosed case patients with conjunctivitis, and a case-control study was performed. Control measures included education to increase hand washing, distribution of alcohol-based hand gel, and prompt treatment of patients with conjunctivitis. RESULTS: During a 6-week period, 92 cases of conjunctivitis occurred among 3500 persons, with an attack rate of 1.75 cases per 100 person-months. Eighty cases (87%) were due to S. pneumoniae; 45 (49%) were confirmed, and 35 (38%) were probable. Ten percent of recruits surveyed carried the outbreak strain. Twenty-two percent self-reported symptoms consistent with conjunctivitis during the outbreak period; sharing washcloths was associated with conjunctivitis (odds ratio, 11.7; P=.03). The causative organism was resistant to azithromycin but susceptible to telithromycin. The outbreak strain was an unencapsulated S. pneumoniae that has not been previously described; it was most closely related to the sequence type causing the Dartmouth College (Hanover, NH) outbreak of conjunctivitis in 2002. CONCLUSIONS: We report a conjunctivitis outbreak among military trainees caused by a novel, unencapsulated strain of S. pneumoniae.

Adolescent↗

PubMed2005

Rapid and fatal meningococcal disease due to a strain of Neisseria meningitidis containing the capsule null locus.

BACKGROUND: Neisseria meningitidis continues to be an important cause of invasive bacterial disease among children and young adults worldwide. In Canada, N. meningitidis strains that bear serogroups B and C polysaccharide capsules predominate. We report the first documented case of invasive meningococcal disease in an immunocompetent host caused by an acapsular strain of N. meningitidis containing the capsule null locus (cnl). METHODS: Analysis of the isolate was performed with use of serological and molecular methods, including multilocus sequence typing and cnl gene identification. Analysis of 16S ribosomal RNA (rRNA) and porA genes was also performed to confirm the identity of the bacterium. RESULTS: The patient was a healthy, immunocompetent 13-year-old child, and N. meningitidis was recovered from a sample of her cerebrospinal fluid before death. The isolate was nontypeable by both conventional antisera and indirect whole-cell enzyme-linked immuosorbent assay methods using antibodies to serogroups B, C, Y, and W135. The isolate was further identified as a cnl strain, serotype 15 (ST-198). N. meningitidis-specific DNA was identified in the isolate and in the pre- and postmortem specimens by 16S rRNA and porA gene analysis. CONCLUSIONS: This is the first reported case of fatal meningococcal disease caused by an acapsular cnl strain of N. meningitidis that was isolated from an immunocompetent host. Routine molecular diagnostic methods targeted at the cnl locus failed to detect this organism, indicating a need to determine the incidence of infection with cnl strains among patients with culture-negative invasive disease.

Adolescent↗

PubMed2005

Genetic analysis of meningococci carried by children and young adults.

BACKGROUND: Neisseria meningitidis is a diverse commensal bacterium that occasionally causes severe invasive disease. The relationship between meningococcal genotype and capsular polysaccharide, the principal virulence factor and vaccine component, was investigated in carried meningococci isolated from 8000 children and young adults in Bavaria, Germany. METHODS: Of the 830 meningococci isolated (carriage rate, 10.4%) by microbiological techniques, 822 were characterized by serogrouping, multilocus sequence typing, and genetic analysis of the capsule region. Statistical and population genetic analyses were applied to these data. RESULTS: The rapid increase in carriage rates with age of carrier, the low prevalence of hyperinvasive meningococci, and the relative prevalence of the 4 disease-associated serogroups were consistent with earlier observations. There was no genetic structuring of the meningococcal population by age of carrier or sampling location; however, there was significant geographic structuring of the meningococci isolated in civil, but not military, institutions. The rate of capsule gene expression did not vary with age of carrier or meningococcal genotype, except for serogroup C, for which increased expression was associated with ST-11 (formerly ET-37) complex meningococci. CONCLUSIONS: Serogroup C capsule expression during carriage may contribute to the invasive character of ST-11 complex meningococci and to the high efficacy of meningococcal serogroup C conjugate polysaccharide vaccine.

Adolescent↗

PubMed2005

An outbreak of serotype 1 Streptococcus pneumoniae meningitis in northern Ghana with features that are characteristic of Neisseria meningitidis meningitis epidemics.

BACKGROUND: The Kassena-Nankana District (KND) of northern Ghana lies in the African meningitis belt, where epidemics of bacterial meningitis have been reoccurring every 8-12 years. These epidemics are generally caused by Neisseria meningitidis, an organism that is considered to be uniquely capable of causing meningitis epidemics. METHODS: We recruited all patients with suspected meningitis in the KND between 1998 and 2003. Cerebrospinal fluid samples were collected and analyzed by standard microbiological techniques. Bacterial isolates were subjected to serotyping, multilocus sequence typing (MLST), and antibiotic-resistance testing. RESULTS: A continual increase in the incidence of pneumococcal meningitis was observed from 2000 to 2003. This outbreak exhibited strong seasonality, a broad host age range, and clonal dominance, all of which are characteristic of meningococcal meningitis epidemics in the African meningitis belt. The case-fatality rate for pneumococcal meningitis was 44.4%; the majority of pneumococcal isolates were antibiotic sensitive and expressed the serotype 1 capsule. MLST revealed that these isolates belonged to a clonal complex dominated by sequence type (ST) 217 and its 2 single-locus variants, ST303 and ST612. CONCLUSIONS: The S. pneumoniae ST217 clonal complex represents a hypervirulent lineage with a high propensity to cause meningitis, and our results suggest that this lineage might have the potential to cause an epidemic. Serotype 1 is not included in the currently licensed pediatric heptavalent pneumococcal vaccine. Mass vaccination with a less complex conjugate vaccine that targets hypervirulent serotypes should, therefore, be considered.

Drug Resistance, Bacterial↗

PubMed2005

Population dynamics of nasal strains of methicillin-resistant Staphylococcus aureus--and their relation to community-associated disease activity.

BACKGROUND: Nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) plays a key role in the epidemiology and pathogenesis of disease. The purpose of this study was to determine the characteristics and dynamics of nasal strains of MRSA, as well as their relation to community-associated disease activity. METHODS: This study is a cross-sectional survey and molecular epidemiologic analysis of nasal colonization by S. aureus in homeless and runaway youths, an underserved population at high risk for staphylococcal disease. RESULTS: Of the 308 study participants, 27.6% carried S. aureus, and 6.2% carried MRSA. Subgroups of individuals with increased MRSA carriage rates were also at highest risk for community-associated MRSA infection; these subgroups included individuals with either HIV infection or AIDS, injection drug users, patients with abscesses, and those recently hospitalized. Multilocus sequence typing and pulsed-field gel electrophoresis identified 2 genotypes--ST59:P (USA1000) and ST8:S (USA300)--that accounted for 84.2% (16/19) of the MRSA isolates carried. The genotypes were distinct from nosocomial genotypes endemic in the hospital, although they originated from individuals with prior exposure to health care. CONCLUSIONS: Comparison of MRSA strains from asymptomatic carriers versus concurrently collected community-associated clinical strains from patients treated at local health-care facilities allowed for the identification of 3 population dynamics of nasal strains of MRSA: (1) endemic clones--for example, ST8:C and ST59:P--sustained asymptomatic carriage and infection over prolonged periods; (2) an epidemic clone, ST8:S, demonstrated enhanced capacity for rapid transmission and widespread infections; and (3) an outbreak clone, ST30:Z (USA1100), was highly infectious but exhibited poor asymptomatic transmission.

Adolescent↗

PubMed2005

Associations between Staphylococcus aureus Genotype, Infection, and In-Hospital Mortality: A Nested Case-Control Study.

We screened 14,008 adult nonsurgical patients for Staphylococcus aureus nasal carriage at hospital admission and assessed them for invasive S. aureus disease and in-hospital mortality. Multilocus sequence typing was performed on endogenous invasive strains and nasal strains of matched asymptomatic carriers to investigate whether virulent clones could be identified in nasal carriers. Clonal complex (CC) 45 was significantly underrepresented (odds ratio [OR], 0.16 [95% confidence interval {CI}, 0.04-0.59]) and CC30 was overrepresented (not statistically significant) among invasive strains (OR, 1.91 [95% CI, 0.91-4.0]). The distribution of CCs of invasive S. aureus strains in noncarriers did not differ from that in carriers. Those infected with S. aureus strains belonging to a CC had higher mortality than those infected with strains not belonging to a CC (P<.05), which indicates the coevolution of S. aureus virulence and spread in humans.

Adult↗

PubMed2005

Postvaccine genetic structure of Streptococcus pneumoniae serotype 19A from children in the United States.

BACKGROUND: The introduction of the 7-valent conjugate pneumococcal vaccine (PCV7) in children may result in serotype replacement. We estimated the rate of increase of invasive pneumococcal disease (IPD) caused by serotype 19A in children <5 years old and determined the genetic composition of these isolates. METHODS: Cases of IPD between July 1999 and June 2004 were identified through the Active Bacterial Core Surveillance. Serotype 19A isolates obtained from children <5 years old between January 2003 and June 2004 were characterized by serotyping, antibiotic susceptibility testing, and pulsed-field gel electrophoresis (PFGE). Select isolates representing homologous PFGE clusters were subjected to multilocus sequence typing, and eBURST was used to delineate clonal groups. RESULTS: Between July 1999 and June 2004, the overall rate of IPD decreased from 23.3 to 13.1 cases/100,000 population (P<.00001). In children <5 years old, the rate decreased from 88.7 to 22.4 cases/100,000 population (P<.00001), whereas the rate in persons > or =5 years old decreased from 18.4 to 12.4 cases/100,000 population (P<.0001). The rate of serotype 19A IPD in children <5 years old increased significantly from 2.6 cases/100,000 population in 1999-2000 to 6.5 cases/100,000 population in 2003-2004; this was accompanied by significant increases in penicillin nonsusceptibility (P=.008) and multidrug resistance (P=.002) among serotype 19A isolates. As was observed during the pre-PCV7 era, clonal complex (CC) 199 predominated within serotype 19A, representing approximately 70% of invasive serotype 19A isolates from children <5 years old during 2003-2004. New serotype 19A genotypes were observed during 2003-2004, including 6 CCs that were not found among pneumococcal serotype 19A isolates during surveillance in 1999. CONCLUSION: Serotype 19A is, at present, the most important cause of IPD by replacement serotypes, and it is increasingly drug resistant. CC199 is the predominant CC among type 19A serotypes in children <5 years old. Our data suggest that some of the increase in rates of infection with serotype 19A may be due to serotype switching within certain vaccine type strains.

Anti-Bacterial Agents↗