Methicillin-resistant Staphylococcus aureus prevalence: Current susceptibility patterns in Trinidad

Background  

Methicillin-resistant Staphylococcus aureus (MRSA) has become one of the most widespread causes of nosocomial infections worldwide. Recently, reports have emerged that S. aureus strains recovered from community-acquired infections are also methicillin-resistant. This study was undertaken to analyze the prevalence of methicillin resistance among isolates at a regional hospital in Trinidad, and document the current resistance profile of MRSA and methicillin-sensitive Staphylococcus aureus (MSSA) to the commonly used anti-staphylococcal agents.     

Listeria monocytogenes: maternal-foetal infections in Denmark 1994-2005

Maternal-foetal infection by Listeria monocytogenes is a rare complication in pregnancy. In the period 1994-2005, 37 culture-confirmed cases of maternal-foetal Listeria monocytogenes infections were reported in Denmark. We examined 36 patients' files in order to evaluate risk factors, clinical and laboratory findings, response to therapy, and outcome for maternal-foetal listeriosis. Patient data and bacteriological findings were divided into 2 groups for comparison: 1 group with children born alive (n=24) and another group with abortion or stillbirth (n=12). 23 of the 36 children survived the acute infection, as did all the mothers. The mothers were generally only mildly affected by the infection. In contrast, among the children born alive, 15 were diagnosed with bacteraemia/septicaemia, 3 children with pneumonia, 3 with neonatal meningitis, and 3 were unaffected. Despite the high frequency of illness only 1 of the live-born children died from the infection and none of the surviving children showed signs of permanent damage at the time they were discharged from hospital. Listeriosis during pregnancy is a serious threat to the unborn child. One-third of culture-confirmed cases of maternal-foetal infections resulted in abortion or stillbirth; however, the prognosis for live-born children is good, even in severely ill newborns.     

Role of integrons in antimicrobial susceptibility patterns of Acinetobacter baumannii

The relationship between the presence and types of integrons and the antimicrobial susceptibility patterns of Acinetobacter baumannii was investigated. A total of 134 non-duplicated A. baumannii isolates, 54.5% (n=73) of which were subsequently found to carry class 1 integrons, were collected from a regional hospital in Taiwan between March and September 2007. Only two types of gene cassette array, aacA4-catB8-aadA1 and aacC1-orfP-orfP-orfQ-aadA1, were identified. Susceptibility data showed that those strains carrying integrons were significantly more resistant to all antibiotics tested except ampicillin/sulbactam and imipenem. An epidemiological study revealed that the same integron could be found in different unrelated strains. These findings suggest that the presence of integrons in A. baumannii is responsible for both the horizontal transfer of antibiotic-resistance genes related to aminoglycosides and chloramphenicol and also represents a marker of multidrug resistance and epidemic potential.     

Pneumococcal and Haemophilus influenzae meningitis in a children's hospital in Ethiopia: serotypes and susceptibility patterns

Streptococcus pneumoniae and Haemophilus influenzae are responsible for most pyogenic meningitis cases in children in Ethiopia. Resistance of S. pneumoniae and H. influenzae to penicillin and chloramphenicol respectively has been reported globally. Resistance has been related to specific serotypes of S. pneumoniae or to beta-lactamase-producing H. influenzae strains. This study describes the serotypes/ serogroups and susceptibility pattern of the two organisms causing meningitis in Ethiopian children. There were 120 cases of meningitis caused by S. pneumoniae (46) and H. influenzae (74) over a period of 3 years (1993-95). Nineteen children died from pneumococcal and 28 from haemophilus meningitis. Penicillin-resistant pneumococcal meningitis (4/8 = 50%) caused a greater mortality rate than penicillin-susceptible pneumococcal meningitis (15/38 = 39%). Common serotypes accounting for 76% of S. pneumoniae were type 14, 19F, 20, 1, 18 and 5; and serotypes 14, 19F and 7 (accounting for 17% of strains) showed intermediate resistance to penicillin G. 97% of the H. influenzae isolates were type b, and in only two cases beta-lactamase-producing. 72% of isolates of the S. pneumoniae we identified belong to serotypes preventable by a 9-valent vaccine. Our study highlights the possibility of resistant pyogenic meningitis in children in Ethiopia due to emerging resistant strains of S. pneumoniae and H. influenzae isolates.     

Pneumococcal antimicrobial resistance: the problem in Hungary.

An epidemiological survey of penicillin resistance as determined by minimum inhibitory concentrations (MICs) in Streptococcus pneumoniae strains collected from several Hungarian laboratories in 1988-1989 indicated a prevalence of 58% among a total of 135 isolates. A significantly higher resistance rate (69.2%) was found for isolates from pediatric patients than from adult patients (44.0%). Penicillin-resistant strains were more frequently resistant to non-beta-lactam antibiotics (tetracycline, erythromycin, co-trimoxazole, and chloramphenicol) than were penicillin-sensitive strains. On the basis of the MIC50 and MIC90 values of ampicillin and five cephalosporins for penicillin-resistant strains, it was established that ampicillin and cephalexin were not superior to penicillin. The low MIC90 of ceftriaxone and cefotaxime for these organisms reflects promising therapeutic potential, even in septicemia and meningitis caused by penicillin-resistant strains. The therapeutic alternative to penicillin in the treatment of respiratory tract infection may be second-generation cephalosporins such as cefuroxime or cefamandole.     

Epidemiology of calicivirus infections in Sweden, 1994-1998

Outbreaks of acute gastroenteritis are frequently caused by caliciviruses. Electron microscopy was used to search for these viruses in fecal samples from patients with acute gastroenteritis. Of 5800 samples collected and analyzed from November 1994 to June 1998, 3700 were associated with outbreaks. A total of 676 outbreaks were analyzed, and viruses were found in 67%. Caliciviruses, usually Norwalk-like viruses (NLVs), were found in 407 (89%) of 455 outbreaks, while Sapporo-like viruses were identified in nine outbreaks, including six that were suspected to include foodborne transmission. Sixty percent of the 1041 patients with calicivirus infections were between 70 and 90 years of age. Food- and waterborne infections were associated with 66 calicivirus outbreaks. Virus-positive outbreaks were documented mainly during winter and spring. The longitudinal survey showed that caliciviruses, and especially the NLVs, cause most nosocomial and community-associated outbreaks in Sweden.     

Pneumococcal and influenza immunization in asplenic persons: a retrospective population-based cohort study 1990-2002

Background  

Splenectomy is associated with increased risk for bacteremia, due to impaired clearance of bloodborne agents and to altered phagocytosis and humoral immunity. We conducted a retrospective cohort study of patients at risk for splenectomy for a 13-year period to determine immunization coverage, and outcomes of those with and without splenectomy, and with or without receipt of influenza or pneumococcal vaccine.     

Pneumococcal infections in HIV-infected adults.

Bacterial pneumonia, specifically pneumococcal infection, is a frequent cause of morbidity and mortality in persons infected with human immunodeficiency virus (HIV). It causes morbidity directly and possibly progression of HIV infection. The clinical presentation and response to therapy are usually similar to that of patients without HIV infection, although radiographic presentations may be atypical. There is a higher incidence of invasive disease and extrapulmonary disease, and mortality may be increased in HIV-infected patients. HIV infection impairs the host response to pneumococcus in a variety of ways. Colonization with Streptococcus pneumoniae may be prolonged for reasons that are incompletely understood. Concern about the rising prevalence of resistant pneumococcal strains is increasing, but the clinical relevance is uncertain. At least 90% of the strains that cause invasive disease are present in the 23-valent pneumococcal vaccine. The response to vaccination declines as immunodeficiency progresses; however, the potential benefit to responders is great and the risk is minimal. Therefore, this vaccine is recommended for all HIV-infected persons.     

Pneumococcal carriage among indigenous Warao children in Venezuela: serotypes, susceptibility patterns, and molecular epidemiology.

Little attention has been paid to pneumococcal carriage and disease in Amerindians from Latin America. The Warao people, an indigenous population from Venezuela, live in the delta of the Orinoco River in geographically isolated communities with difficult access to medical care. To obtain insight into pneumococcal carriage and the theoretical coverage of pneumococcal vaccines in this population, we investigated pneumococcal colonization, serotype, and genotype distribution among Warao children in 9 distinct, geographically isolated communities in the Delta Amacuro area in the northeast of Venezuela. From April 2004 through January 2005, a total of 161 Streptococcus pneumoniae isolates were recovered from single nasopharyngeal swab samples obtained from 356 children aged 0-72 months. The overall pneumococcal carriage rate was 49%, ranging from 13% to 76%, depending on the community investigated and the age of the children (50% among children aged <2 years and 25% among children aged >2 years). The most frequent serotypes were 23F (19.5% of isolates), 6A (19.5%), 15B (10.4%), 6B (9.1%), and 19F (7.2%). The theoretical coverage of the 7-valent pneumococcal conjugate vaccine, including the cross-reactive nonvaccine serotype 6A, was 65%. A total of 26% of the isolates were resistant to first-line antibiotics, with 70% of these strains being covered by the 7-valent pneumococcal conjugate vaccine. Restriction fragment end labelling analysis revealed 65 different genotypes, with 125 (80%) of the isolates belonging to 27 different genetic clusters, suggesting a high degree of horizontal spread of pneumococcal strains in and between the villages. The high colonization rates and high (registered) acute respiratory tract infection morbidity and mortality in this part of Venezuela suggest that Warao children are at increased risk for pneumococcal disease and, therefore, benefit from vaccination.     

Serotype and antimicrobial susceptibility patterns of isolates of Streptococcus pneumoniae causing invasive disease in The Gambia 1996-2003

OBJECTIVES: To describe the characteristics of pneumococcal isolates obtained from patients with invasive pneumococcal disease in The Gambia. METHODS: Pneumococcal isolates were obtained from children aged < or =6 years with invasive pneumococcal disease during a Haemophilus influenzae vaccine effectiveness study (1997-2002) and from patients with invasive pneumococcal disease admitted to the MRC hospital, Fajara, for routine care (1996-2003). Isolates were identified, serotyped and tested for antibiotic susceptibility. RESULTS: Five hundred and thirty one pneumococcal isolates were obtained from 518 patients; 55 (10.6%) patients died; 415 isolates (79%) were from blood culture, 84 (16%) from CSF, and 42 (8%) from lung aspirates. Forty serogroups and serotypes were identified; six accounted for 64% and 16 for 86% of all episodes; 33.7% were of serotypes 1 and 5. 23.5% were of a 7-valent vaccine serotype, 57.1% were of a 9-valent vaccine serotype; 56% were of a 7-valent serogroup and 78% were of a 9-valent serogroup. There was a significant increase in the proportion of isolates of non-vaccine serogroup with increasing age (P < 0.0001). Antibiotic resistance had not significantly increased over time; but intermediate non-susceptibility to penicillin had risen and resistance to chloramphenicol had fallen in isolates of vaccine serotype compared with those of non-vaccine serotype. CONCLUSIONS: The majority of invasive pneumococcal disease in The Gambia is caused by pneumococci of relatively few serogroups. A conjugate vaccine would be expected to reduce the pneumococcal disease burden substantially and to have a beneficial effect on pneumococcal antibiotic resistance to penicillins.     

Pneumococcal infections in children after transplantation.

Bacterial infections in recipients of bone marrow and solid-organ transplants remain a major cause of morbidity and death. The cases of 42 children who had undergone transplantation and developed an infection with Streptococcus pneumoniae were retrospectively reviewed. Thirty-four patients had 1 episode of infection, whereas 7 had 2 episodes and 1 had 3 episodes of infection. Solid-organ recipients were more likely to have recurrent invasive disease (P<.02). A total of 31 (74%) of 42 patients were on immunosuppressive therapy, and 74% had been on antimicrobial therapy within 30 days before diagnosis of S. pneumoniae infection. Only 33% of eligible patients had received a pneumococcal vaccine. Twenty-six percent of isolates recovered were not susceptible to penicillin, and 18% were not susceptible to ceftriaxone. Two patients experienced infection-related deaths; one of these had a penicillin-nonsusceptible isolate. The antimicrobial susceptibilities and outcome of infections with S. pneumoniae in patients who have undergone transplantation are similar to those in the general pediatric population.     

Precise spatial structure impacts antimicrobial susceptibility of S. aureus in polymicrobial wound infections

A hallmark of microbial ecology is that interactions between members of a community shape community function. This includes microbial communities in human infections, such as chronic wounds, where interactions can result in more severe diseases. Staphylococcus aureus is the most common organism isolated from human chronic wound infections and has been shown to have both cooperative and competitive interactions with Pseudomonas aeruginosa. Still, despite considerable study, most interactions between these microbes have been characterized using in vitro well-mixed systems, which do not recapitulate the infection environment. Here, we characterized interactions between S. aureus and P. aeruginosa in chronic murine wounds, focusing on the role that both macro- and micro-scale spatial structures play in disease. We discovered that S. aureus and P. aeruginosa coexist at high cell densities in murine wounds. High-resolution imaging revealed that these microbes establish a patchy distribution, only occupying 5 to 25% of the wound volume. Using a quantitative framework, we identified a precise spatial structure at both the macro (mm)- and micro (µm)-scales, which was largely mediated by P. aeruginosa production of the antimicrobial 2-heptyl-4-hydroxyquinoline N-oxide, while the antimicrobial pyocyanin had no impact. Finally, we discovered that this precise spatial structure enhances S. aureus tolerance to aminoglycoside antibiotics but not vancomycin. Our results provide mechanistic insights into the biogeography of S. aureus and P. aeruginosa coinfected wounds and implicate spatial structure as a key determinant of antimicrobial tolerance in wound infections.

Polymicrobial human infections are a major burden on human health. These infections are often more tolerant to antibiotics and have worse clinical outcomes compared to their single-microbe counterparts (1–7). Properties specific to polymicrobial infections are often attributed to interactions occurring between microbes, and much work has been done to identify and mechanistically understand these interactions (8–12). Recent evidence using preclinical infection models has shown that interactions between microbes impact the micron-scale spatial structure of the infecting community (13–16), implicating the spatial structure as a key component controlling community function, and thus infection outcomes (17). However, most of our understanding of polymicrobial interactions is derived from studies using in vitro models (13, 14). Hence, key elements of infection dynamics and the role of host factors are often overlooked.Pseudomonas aeruginosa and Staphylococcus aureus are commonly used to study microbe–microbe interactions, both in vitro and in vivo (11, 13, 18–24). These microbes cooccur in several polymicrobial human infections, including chronic wounds and in the lungs of people with cystic fibrosis (1–3, 5, 25–29). There is conflicting evidence regarding the impact of coinfection on human disease outcomes, with some studies concluding that P. aeruginosa alone has worse outcomes (32–34) while others conclude that P. aeruginosa–S. aureus coinfections lead to more severe diseases (35–37). The experimental data are clearer in murine models of infection, which have shown that coinfection can result in increased antibiotic tolerance and worse infection outcomes (8, 10, 20, 28). While the mechanisms controlling these synergistic interactions are largely unknown in vivo, it has been hypothesized that P. aeruginosa and S. aureus occupy distinct regions in human chronic wounds (28), suggesting that biogeography may play a role in mediating polymicrobial wound infection outcomes.Here, we collected more than 100 high-resolution confocal images of mouse chronic wounds infected with P. aeruginosa and S. aureus in mono- and co-infection. Using these images, we quantified the 3-dimensional macro- and micron-scale spatial structure of P. aeruginosa and S. aureus communities in vivo and defined the role of known P. aeruginosa extracellular antimicrobials on the spatial structure. We discovered that S. aureus and P. aeruginosa coexist in mouse wound infections at high bacterial densities, but their distribution is patchy. In addition, we discovered and quantified a precise, micron-scale spatial structure dependent on the P. aeruginosa-secreted small-molecule 2-heptyl-4-hydroxyquinoline N-oxide (HQNO) and that this spatial structure is different at the healing edge versus the center of the wound. Finally, we show that the community spatial structure has clinically important outcomes, including altered antibiotic tolerance.     

Acute rhinosinusitis during Hajj season 2014: Prevalence of bacterial infection and patterns of antimicrobial susceptibility

BackgroundThe presence of large number of pilgrims during Hajj in Makkah region increases the risk of respiratory diseases. In this study, we aimed to assess the bacteriology of acute rhinosinusitis (ARS) during Hajj season and to demonstrate the antimicrobial susceptibility patterns that should guide the clinicians towards more appropriate antibiotic use.MethodsPatients with ARS presenting during Hajj season of 2014 were prospectively enrolled. According to EPOS2012 criteria. Sampling of sinus secretions was performed from the middle meatus adjacent to the maxillary sinus ostium via endoscopic guidance. Over all, the study has covered all ENT, emergency and outpatient departments in Hajj.ResultsTwo hundred and twenty six patients with ARS were enrolled in the study. Pathogenic bacteria were identified in 93 (41.2%) patients. Of the 93 patients with bacterial ARS, Staphylococcus aureus was isolated in 46 (49.5%) patients, out of which 13 (28.3%) were methicillin-resistant Staphylococcus aureus (MRSA).The second most common group of bacterial isolates was Enterobacteriaceae such as Escherichia coli, and various Klebsiella species. Antibiotic sensitivity showed that methicillin-sensitive Staphylococcus aureus (MSSA) was also sensitive to cephalosporins, quinolones and clindamycin, while exhibiting relatively less sensitivity rates to amoxicillin-clavulinic acid and macrolides.ConclusionOur study demonstrates the importance of assessing the bacteriology of ARS to help implement guidelines for proper treatment and prevention protocols during Hajj season.     

Climate, mosquito indices and the epidemiology of dengue fever in Trinidad (2002-2004)

Between January 2002 and December 2004, a population-based study on the effects of climate and mosquito indices on the incidences of dengue fever (DF) and dengue haemorrhagic fever (DHF) was conducted in Trinidad, West Indies. The incidence of DF was 5.05 cases/1000 population in 2002, largely as the result of a major outbreak, but declined to 0.49 case/1000 in 2004. The monthly Aedes aegypti (L.) Breteau indices (BI) did not decline over the 3-year study period, however, but increased from a mean of 29 in 2002 to one of 36 in 2004, with seasonal variations (BI of 30-46 and 20-34 were recorded in the wet and dry seasons, respectively). No significant correlations were observed between temperature and DF or DHF incidence but rainfall was found to be significantly correlated with DF incidence, with a clearly defined 'dengue season', between June and November, in two of the study years. The apparent decline in dengue transmission since 2002 appears to be largely attributable to the development of 'herd immunity' in the general population and not to the attempts at vector control. Since the introduction of new serotypes or the fading of the herd immunity could lead to an explosive epidemic of dengue in Trinidad, there is clearly a need for continued surveillance.