Relatedness of strains of methicillin-resistant coagulase-negative Staphylococcus colonizing hospital personnel and producing bacteremias in a neonatal intensive care unit

Coagulase-negative staphylococci (CoNS) are a major cause of sepsis in neonatal intensive care units (NICU) worldwide. Infecting strains of these commensal bacteria may originate from NICU personnel. Therefore, we studied the characteristics of CoNS isolates from NICU personnel and compared them to those of isolates from the general population and from sepsis patients. Furthermore, we studied the epidemiological effect on CoNS carriage of NICU personnel after a period of absence. In our study, we isolated CoNS from the thumbs of NICU personnel every 2 weeks during the summer of 2005 and sampled personnel returning from vacation and a control group from the general population. Furthermore, we collected sepsis isolates from this period. Isolates were tested for antibiotic resistance, mecA and icaA carriage, biofilm production, and genetic relatedness. We found that mecA and icaA carriage as well as penicillin, oxacillin, and gentamicin resistance were significantly more prevalent in CoNS strains from NICU personnel than in community isolates. Similar trends were observed when postvacation strains were compared to prevacation strains. Furthermore, genetic analysis showed that 90% of the blood isolates were closely related to strains found on the hands of NICU personnel. Our findings revealed that CoNS carried by NICU personnel differ from those in the general population. Hospital strains are replaced by community CoNS after a period of absence. NICU personnel are a likely cause for the cross-contamination of virulent CoNS that originate from the NICU to patients.Coagulase-negative staphylococci (CoNS) are the most-frequent cause of late-onset sepsis among newborn infants in neonatal intensive care units (NICU) worldwide. Incidences of up to 66% of late-onset sepsis have been reported (8, 17). The high incidence of these infections is due not only to a high rate of invasive procedures in immunocompromised patients but also to the bacterium's ability to form biofilms (10).The biofilm-forming property of CoNS generally is considered their most important virulence factor. Biofilm formation is mediated by several factors, such as surface proteins and the polysaccharide intercellular adhesin (PIA). PIA is regulated by the ica operon, and the presence of the ica genes has been shown to be a predictor for biofilm formation in Staphylococcus epidermidis (8,9). Furthermore, we previously showed a strong association between the carriage of icaA and mecA, the gene coding for methicillin resistance.Antibiotic resistance in CoNS, especially against ␤-lactam antibiotics, has increased over the years. The mecA gene is present in more than 80% of the CoNS late-onset sepsis isolates (8). The high rate of antibiotic resistance and their biofilm-forming capacities probably enable CoNS to persist in the intensive care environment by giving them a selective advantage over other more-susceptible species.Since CoNS are commensal skin bacteria, it is generally hypothesized that infecting strains originate from NICU personnel. This theory i...

Section: Discussionsupporting

confidence: 54%

Coagulase-Negative Staphylococcal Skin Carriage among Neonatal Intensive Care Unit Personnel: from Population to Infection

Hira¹,

Sluijter²,

Goessens

et al. 2010

“…Venous catheters have been implicated in more than one-half of the cases of CoNS bacteremia in NICUs (2,11,15,26). Infections at metastatic sites, such as the central nervous system, heart, bones, and joints, are especially common; and such infections in this vulnerable population are especially difficult to treat (14,(28)(29)(30).…”

Section: Discussionmentioning

confidence: 99%

“…It has been postulated that the infants themselves are the reservoirs of endemic strains of staphylococci, with organism transmission occurring by the hands of health care workers (7). Although Low et al (24) did not investigate the reservoir or mode of transmission of the S. haemolyticus strain, Patrick et al (30) and Huebner et al (16) isolated from the nasopharynges and hands of health care workers, respectively, CoNS that were genetically related to the CoNS colonizing or causing disease in patients during the same time period.…”

Section: Discussionmentioning

confidence: 99%

“…The organ sites of CoNS infections vary, but virtually all infections involve contamination of an indwelling medical device (3,31,35). A prerequisite for infection is CoNS colonization, which the neonate largely acquires from environmental sources, including health care workers (16,30). Treatment of CoNS infections is complicated by certain unique characteristics of these organisms, most notably, their ability to express resistance to multiple antibiotics.…”

mentioning

confidence: 99%

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Decreased Vancomycin Susceptibility of Coagulase-Negative Staphylococci in a Neonatal Intensive Care Unit: Evidence of Spread of Staphylococcus warneri

Reboli¹,

Hubler

Rodgers

et al. 2003

Coagulase-negative staphylococci (CoNS) are important pathogens in premature neonates; decreasing glycopeptide susceptibility has been observed among these isolates. The epidemiology of colonization with CoNS, the organisms' vancomycin susceptibilities, and genetic relatedness were studied over 6 months in a tertiary-care neonatal unit. A total of 321 isolates of CoNS were isolated. Seventy-five percent of the infants were colonized at admission, and virtually all were colonized thereafter. Common species were Staphylococcus epidermidis (69%), S. warneri (12%), S. haemolyticus (9.7%), and S. hominis (5.6%). A total of 3.9% of CoNS isolates had decreased vancomycin susceptibility (DVS) (MICs > 2.0 g/ml); isolate recovery was associated with a stay in a neonatal intensive care unit for >28 days (P ‫؍‬ 0.039), vancomycin exposure (P ‫؍‬ 0.021), and S. warneri colonization (P < 0.0001). Nine of 12 (75%) CoNS with DVS were S. warneri, had enhanceable high-level resistance in vitro, were indistinguishable or closely related by pulsed-field gel electrophoresis, and were different from 29 vancomycin-susceptible S. warneri isolates. Epidemiological analysis suggested unsuspected nosocomial spread. Species determination in certain settings may aid in the understanding of emerging nosocomial problems.

“…Although we did not investigate the reservoir and mode of transmission, it has been postulated that the infants themselves are the reservoirs of endemic strains of staphylococci, with organism transmission occurring through contact with the hands of health care workers (4). Furthermore, other reports have shown that CoNS isolates from the nasopharynges and hands of health care workers are often genetically related to the organisms that colonize and/or cause disease in neonates, confirming the importance of health care workers in the nosocomial transmission of CoNS in the NICU setting (9,17).…”

mentioning

confidence: 94%

Nosocomial Spread of a Staphylococcus hominis subsp. novobiosepticus Strain Causing Sepsis in a Neonatal Intensive Care Unit

Cháves¹,

García–Álvarez²,

Sanz³

et al. 2005

From 2002 to 2003, 32 isolates of Staphylococcus hominis subsp. novobiosepticus (SHN) were recovered from 21 patients, 18 of whom were neonates, with 13 considered to have late-onset SHN sepsis. All isolates from neonates had an indistinguishable pulsed-field gel electrophoresis pattern. Our data support SHN as an important nosocomial pathogen in neonates.Coagulase-negative staphylococci (CoNS) are now recognized as a major cause of nosocomial infections in neonatal intensive care units (NICUs) (8) and are responsible for 48% of late-onset sepsis among very-low-birth-weight neonates (20). Although Staphylococcus epidermidis causes 60 to 93% of CoNS bloodstream infections, several other CoNS species are reported to cause disease in infants (10,11,18). Recently, a novel subspecies of Staphylococcus hominis, S. hominis subsp. novobiosepticus (SHN), was isolated from blood cultures and other clinical specimens (6, 12). The name derives from the combination of novobio, pertaining to the property of novobiocin resistance, and septicus, pertaining to the ability to cause sepsis. After isolating SHN from several blood cultures at the NICU during 2002 and 2003, we undertook a retrospective study in our 1,300-bed tertiary care institution to determine the prevalence of this subspecies, the clinical significance of the isolates, and whether the infections were clonal in origin.Clinical records of patients from whom SHN had been isolated were reviewed. Diagnosis of sepsis was based on the assessment of the attending physician. For NICU patients, true infection was defined either by isolation of SHN from two separate blood cultures or by a single SHN-positive blood culture and an elevated serum level of C-reactive protein (Ն2 mg/dl). Blood samples were inoculated and processed in an automated system (BacT/Alert [BioMérieux, Durham, NC] or BACTEC 9240 [BD Diagnostics, Sparks, MD]). The type strain of SHN (ATCC 700236) was used as a reference standard throughout the investigations. Identification and susceptibility testing were performed using conventional methods and the Wider system (Soria Melguizo, Madrid, Spain) (3, 16). A zone of inhibition measuring Յ15 mm in Mueller-Hinton agar or Յ11 mm on Trypticase soy agar plates was considered indicative of novobiocin resistance (12). All isolates of SHN underwent confirmatory PCR analysis for the mecA gene (7). To confirm the identification of SHN, broad-spectrum primers were used for sequencing the 5Ј ends of both strands of the 16S rRNA gene (2, 6) using an ABI Prism 3100 genetic analyzer (Applied Biosystems, Foster City, CA). Further molecular characterization of SHN isolates was performed by pulsed-field gel electrophoresis (PFGE) following digestion of DNA extracts with SmaI (5).During 2002 and 2003, 32 isolates of SHN were recovered from 21 patients. Twenty-three isolates were from blood cultures, six were from catheters, one was from cerebrospinal fluid (CSF), one was from a wound, and one was from external ear fluid. All 21 patients yielded an SHN-positive blood culture. A...