Outbreak due to methicillin- and rifampin-resistant Staphylococcus aureus: epidemiology and eradication of the resistant strain from the hospital.

A methicillin- and rifampin-resistant strain of Staphylococcus aureus was introduced into a university hospital by interstate transfer of an infected surgical patient. An outbreak occurred, and 17 patients became infected or colonized with the epidemic strain. Reservoirs appeared to be patients who were infected or colonized with the resistant S aureus and possibly two nurses who were nasal carriers. The outbreak isolate was likely spread by contact with contaminated hands of personnel. A retrospective case-control study identified tracheostomy, débridement, and irrigation of wounds by power spray and prolonged nasogastric intubation as risk factors for acquisition of the epidemic strain. Analysis of factors by groups indicated that surgical procedures, wound care procedures and instrumentation of the respiratory tract were significantly associated with cases. The nasal carrier state was eradicated in two nurses by topical application of 5% vancomycin. The epidemic strain was eradicated from the hospital 8 months after it was introduced.

Outbreak of Salmonella typhimurium gastroenteritis due to an imported strain resistant to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole in a nursery.

An outbreak caused by a highly resistant strain of Salmonella typhimurium occurred in a nursery at a university medical center. The outbreak strain, which was resistant to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole, was apparently imported from the Far East by a Cambodian refugee. The five patients involved had severe underlying diseases, and bacteremia and meningitis developed in one of these patients. The only reservoir identified was the gastrointestinal tracts of the infected patients, and infection was probably transmitted by the contaminated hands of hospital personnel. The outbreak was rapidly brought under control by isolating cases outside of the nursery and by instituting enteric precautions for infants who remained in the nursery. When compared by disk diffusion susceptibility tests with 353 strains of S. typhimurium tested at the Centers for Disease Control, the imported strain had a unique antibiogram. Bacteriophage typing of the strains revealed that all were untypable; this, in itself, was a good marker, because only 5 to 10% of S. typhimurium isolates in this country have this property. Agarose gel electrophoresis of isolates from the five patients revealed an identical plasmid banding pattern consisting of three large and three small plasmids. Highly resistant strains of S. typhimurium imported from the Far East may spread rapidly when introduced into a hospital nursery. Prompt institution of control measures may limit the outbreak and prevent systemic infections for which there are few effective therapeutic agents.

Streptococcus faecium outbreak in a neonatal intensive care unit.

An outbreak of bacteremia and meningitis in a neonatal intensive care unit is described. Seven cases occurred in premature infants with severe underlying diseases. An epidemiological investigation failed to document the reservoir of the epidemic strain but suggested that its transmission among the infants was via the hands of hospital personnel. All patients had nasogastric tubes and multiple intravascular devices, and the portal of entry may have been either the gastrointestinal tract or the sites of the intravascular devices. Conventional biotyping of isolates failed to differentiate between isolates from infected patients and isolates recovered from prevalence surveys and from the environment. However, rapid identification systems (API-20S [Analytab Products, Plainview, N.Y.] and the AutoMicrobic system [Vitek Systems, Inc., Hazelwood, Mo.]) were able to distinguish isolates recovered from infected patients and hands of hospital personnel from isolates recovered during prevalence and environmental surveys and 29 isolates from widespread geographical areas. This is the first known report of a nosocomial neonatal outbreak of bacteremia and meningitis due to Streptococcus faecium; it underscores the importance of identifying streptococci to species level.

Ventriculostomy-related infections. A prospective epidemiologic study.

We concluded a prospective epidemiologic study of ventriculostomy-related infections (ventriculitis or meningitis) in 172 consecutive neurosurgical patients over a two-year period to determine the incidence, risk factors, and clinical characteristics of the infections. Ventriculitis or meningitis developed in 19 of 172 patients (11 per cent) undergoing a total of 213 ventriculostomies. When data from all these cases plus five cases of nonventriculostomy-related infection were combined, cerebrospinal-fluid pleocytosis was more significantly associated with the diagnosis of ventriculitis or meningitis (P less than 0.0001) than were fever and leukocytosis (P = 0.07). Risk factors for ventriculostomy-related infections included intracerebral hemorrhage with intraventricular hemorrhage (P = 0.027), neurosurgical operations (P = 0.016), intracranial pressure of 20 mm Hg or more (P = 0.019), ventricular catheterization for more than five days (P = 0.017), and irrigation of the system (P = 0.021). Previous ventriculostomy did not increase the risk of infection with subsequent procedures. We conclude that ventriculostomy-related infections may be prevented by maintenance of a closed drainage system and by early removal of the ventricular catheter. If monitoring is required for more than five days, the catheter should be removed and inserted at a different site.

Nosocomial klebsiella infection in a neonatal unit: identification of risk factors for gastrointestinal colonization.

Sequential outbreaks of infection due to gentamicin-resistant Klebsiella pneumoniae (GRKP) types 30 and 19 occurred in the neonatal intensive care unit (NICU) at the Medical College of Virginia in 1977 and 1978. The extensive epidemiologic investigation carried out included a case-control study, careful review of aseptic technique, and cultures from nursery staff and environment. The gastrointestinal (GI) tracts of the patients were the reservoirs for GRKP, and the epidemic strain was transmitted by hands of personnel. The case-control study showed a significant relationship between acquisition of GRKP by patients and oropharyngeal and GI instrumentation, including use of bag resuscitation, oropharyngeal suctioning, and use of nasogastric feeding tubes. The findings of the case-control study were supported by observation of the patient care techniques practiced by NICU staff. Institution of control measures based on results of the epidemiologic investigation of the first outbreak rapidly brought the second outbreak under control, even though cohorting or use of routine isolation was not possible. Whereas GI colonization and hand transmission have been described previously in outbreaks of K. pneumoniae infections in NICUs, this study is the first to document the mode of inoculation of patients' GI tracts by contaminated hands of personnel.

Sequential outbreaks of infection due to Klebsiella pneumoniae in a neonatal intensive care unit: implication of a conjugative R plasmid.

Sequential outbreaks of infection in a neonatal intensive care unit were due to multiple antibiotic-resistant strains of Klebsiella pneumoniae of different serotypes. In investigations of these outbreaks, the transfer of resistance to gentamicin, ampicillin, cephalothin, carbenicillin, and kanamycin from gentamicin-resistant organisms to standard laboratory recipients and between recipients was observed. Purified plasmid DNA, isolated from all multiple antibiotic-resistant strains, was analyzed by agarose gel electrophoresis, which revealed a common, large plasmid component with a molecular size of 71 megadaltons. Analysis of drug-resistant progeny suggested this plasmid encoded resistance to antibiotics and the information needed for its transmission. The identity of the plasmid from three different sources was established by the use of restriction-enzyme fingerprinting. The dissemination and persistence of this plasmid in environmental and fecal organisms, despite the disappearance of multiple antibiotic-resistant K. pneumoniae, provided a potential source for spread to other bacteria.

Enterobacter cloacae septicemia in a burn center: epidemiology and control of an outbreak.

An outbreak of infections due to Enterobacter cloacae occurred in the burn center at the Medical College of Virginia (Richmond, Virginia) in 1976. Fifteen patients had bacteremia due to E. cloacae; 10 cases of bacteremia occurred during a six-week period in January and February. The development of bacteremia was significantly related to the extent of third-degree burn and to admission to the burn center in January and February but not to the presence of an intravenous cannula, underlying disease, or antimicrobial therapy. E. cloacae was spread by contaminated hands of personnel and by cross-contamination of hydrotherapy water. A shortage of staff appeared to be an important factor in the occurrence of the outbreak. Control measures included an increase in the number of personnel, instruction of personnel in proper aseptic technique, and adoption of a new hydrotherapy protocol.

Resistant Enterobacter cloacae in a burn center: the ineffectiveness of silver sulfadiazine.

Enterobacter cloacae sepsis was found in 15 burn center patients in 1976, of whom 13 died. Nine of the deaths occurred in the first 60 days. The Burn Center isolates were resistant to silver sulfadiazine (AgSD) in agar cup-plate tests and confirmed by tube dilution tests. Hospital, non-burn isolates of E. cloacae were sensitive to AgSD. All E. cloacae isolates were sensitive to mafenide acetate (MA) in the agar cup-plate tests, but this was not confirmed by the tube dilution tests. The agar cup-plate susceptibility test is a simple, rapid and effective technique for determining resistant and sensitive isolates of E. cloacae. Patients who were changed from AgSD to MA because of resistant E. cloacae infection did not have improved survival. An animal study showed that AgSD was ineffective against this strain of E. cloacae and that MA was more effective than AgSD when applied 24 hr postburn but neither were effective at 48 hr postburn. MA was bacteriostatic but not bactericidal with this E. cloacae strain.

Electrochemical method for the early detection of urinary-tract infections.

A method for detecting the presence of bacteria in urine based on measuring a change in potential between two electrodes was tested in a clinical microbiology laboratory. Initial tests were conducted with 13 bacteria commonly associated with urinary-tract infections; all of the test organisms were detected within 2--9 hours. A linear relationship was established between inoculum size and the time an increase in voltage was observed on a strip-chart recorder. No response was seen with sterile urine, but urine samples inoculated with Escherichia produced the expected positive response. One hundred twenty-eight urine specimens from hospitalized persons were simultaneously tested by the electrochemical detection method (ECDM) and by conventional bacteriologic procedures. Ninety-four per cent of 49 positive samples with counts of 10(5) organisms per ml. or more were detected within 4 hours and 100% at 10 hours with the ECDM. Twenty-nine specimens with counts less than 10(5) cells per ml. were detected in 3.5 to 9 hours; two samples (8%) in this group were positive within 4 hours. Fifty samples were negative for bacterial growth, and no increase in voltage was found with these samples.