Multiple intensive care unit outbreak of Acinetobacter calcoaceticus subspecies anitratus respiratory infection and colonization associated with contaminated, reusable ventilator circuits and resuscitation bags

Ribotyping of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex

The Acinetobacter calcoaceticus-Acinetobacter baumannii complex consists of four genotypically distinct but phenotypically very similar bacterial species or DNA groups: A. calcoaceticus (DNA group 1), A. baumannii (DNA group 2), unnamed DNA group 3 (P. J. M. Bouvet and P. A. D. Grimont, Int. J. Syst. Bacteriol. 36:228-240, 1986), and unnamed DNA group 13 (I. Tjernberg and J. Ursing, APMIS 97:595-605, 1989). Because strains in this complex cause nosocomial outbreaks, it is important to be able to identify them as completely as possible. Ribotyping could provide such identification. Therefore, ribotyping was done on 70 strains in the A. calcoaceticus-A. baumannii complex with known DNA group affiliations by use of restriction enzymes EcoRI, ClaI, and SalI. A nonradioactive digoxigenin-11-dUTP-labeled Escherichia coli rRNA-derived probe was used. With any of the three restriction enzymes, banding patterns that were specific for each DNA group were seen. All 70 strains showed banding patterns that could identify them to the correct DNA group by use of any two of the three enzymes. In addition, banding patterns that could separate strains within any one DNA group were present. The discriminatory index of P. Hunter and M. Gaston (J. Clin. Microbiol. 26:2465-2466, 1988), applied to all strains with the combined results obtained with all three enzymes, revealed a value of 0.99. For strains in each DNA group, the value varied from 0.93 to 0.98. These results indicate the high discriminatory power of the system when used for epidemiological typing.

Drug treatment of pneumonia in the hospital. What are the choices?

Mortality and morbidity of nosocomial pneumonia remain high. Successful treatment of pulmonary infections depends on several factors including type of infection, offending pathogen, status of host defences, and adequate choice of antibiotic therapy. The physician's decision should aim at achieving antibiotic concentrations beyond the MIC at the site of infection. Gram-negative bacilli, notably Pseudomonos aeruginosa, Klebsiella pneumoniae and Escherichia coli, remain the most frequent agents in nosocomial pneumonia. Staphylococcus aureus and Streptococcus pneumoniae predominate among the Gram-positive cocci. Pneumocystis carinii predominates in immunocompromised patients. Protected sample bronchoscopy associated with quantitative cultures of samples, and quantification of intracellular microorganisms in cells recovered by broncho-alveolar lavage are two promising procedures which might replace previous, more aggressive methods. Penetration of antibiotics into lung tissue depends on physicochemical properties of the drug and the degree of inflammation of lung tissue. Quinolones, macrolides, tetracyclines and trimethoprim penetrate well into bronchial secretions. Penetration is moderate to low for aminoglycosides and beta-lactams. Fluoroquinolones and new beta-lactam agents, including third-generation cephalosporins imipenem, aztreonam and ticarcillin-clavulanate, showed comparative clinical efficacy in treatment of nosocomial pneumonia, with an efficacy rate close to 80%. Aminoglycosides should not be used alone. Combination therapy reduces but does not eliminate the risk of selection of Gram-negative resistant mutants. It should not be used routinely except for P. aeruginosa, Enterobacter cloacae and Serratia marcescens infections.

Association of contaminated gloves with transmission of Acinetobacter calcoaceticus var. anitratus in an intensive care unit

PURPOSE

Acinetobacter calcoaceticus var. anitratus is an important nosocomial pathogen that has been associated with environmental reservoirs. An increased isolation rate of A. anitratus in our intensive care units (ICUs), from 0.03% (two of 7,800) to 0.5% (seven of 1,300) (p less than 0.00003), prompted an investigation.

PATIENTS, METHODS, AND RESULTS

Ten patients were admitted to the surgical ICU and nine to the medical ICU during the outbreak period (late December 1987 to January 1988). Controls were all patients on the units who were not infected or colonized with the transmitted strain of A. anitratus. Three patients had A. anitratus pneumonia. A throat culture prevalence survey demonstrated three patients colonized with A. anitratus. Cases were placed in a cohort and symptomatic cases treated. An epidemiologic investigation was conducted to identify reservoirs and modes of transmission. Latex gloves were being used for universal precautions without routine changing of gloves between patients. Environmental sources culture-positive for A. antitratus included a small volume medication nebulizer and gloves in use for patient care. Plasmid typing showed that plasmid profiles of isolates from two symptomatic patients, two colonized patients, the nebulizer, and the gloves were identical. Other A. anitratus ICU isolates had distinct plasmid profiles. All patients with the transmitted strain had been in the surgical ICU. The need for changing gloves between patients and contaminated body sites was reinforced.

CONCLUSION

Gloves, used incorrectly for universal precautions, may potentially transmit A. anitratus.

Serotyping of clinical isolates of Acinetobacter baumannii and genospecies 3: detection of additional serovars

Continued serological monitoring of clinical isolates of Acinetobacter baumannii and genospecies 3 permitted identification of 7 new serovars of A. baumannii and 8 additional serovars of genospecies 3.

Epidemiological surveillance of Acinetobacter species

Two hundred and sixty Acinetobacter isolates were recovered from 237 patients over a 2-year period; 156 isolates from 135 spinal cord injuries unit (SCIU) patients and 104 isolates from 102 patients in all the other hospital units. In SCIU patients, 133 isolates were recovered from the urine, 21 from wounds and aspirates, one from sputum and one from blood culture. In non-SCIU patients, 12 isolates were recovered from urine, 43 from wounds and aspirates, 48 from sputum and one from blood culture. Sixty-nine percent of isolates from SCIU patients showed resistance to gentamicin compared to 3% from non-SCIU patients. Gentamicin-resistant Acinetobacter anitratus was recovered from many environmental sites in the SCIU wards and from the hands of seven of 94 SCIU staff members tested. Serial rectal swabs were obtained from 79 newly-diagnosed SCIU patients. Ninety-two percent of those patients followed for up to 5 months acquired gentamicin-resistant Acinetobacter anitratus in their intestinal tract. API 2ONE profiles and antibiograms suggested that two distinct gentamicin-resistant strains of A. anitratus had become endemic in the SCIU and that nosocomial transmission was a frequent occurrence.

Manual ventilation bags as a source for bacterial colonization of intubated patients

A group of 14 intensive care unit (ICU) patients were studied to determine if manual ventilation bags (MVB) could serve as a source of bacterial or fungal pathogens that could colonize the respiratory tract of intubated patients. A total of 51 cultures were simultaneously obtained of patient's sputum, the exterior MVB surface, MVB port, and MVB interior (postexhalation valve). Pathogens colonizing or infecting the respiratory tract of intubated ICU patients were frequently simultaneously present on the exterior surface of the MVB and inside the MVB port used to connect the MVB with the endotracheal tube. In addition, coagulase-negative staphylococci and yeast were frequently present on the exterior surface of the MVB. The interior of the MVB was usually sterile. In three instances pathogens were isolated from the MVB before isolation from the patient's sputum. MVB may serve as a source for colonizing the respiratory tract of intubated ICU patients and/or the hands of medical personnel. The exterior surface and port of MVB should be cleaned of visible debris and disinfected at least once a day.

Serotyping of clinical isolates of Acinetobacter: serovars of genospecies 3

A total of 156 clinical isolates of genospecies 3, the second most commonly encountered member of the genus Acinetobacter at our institution, were identified with carbon source utilization tests among 400 Acinetobacter isolates. Checkerboard tube agglutination tests and reciprocal cross-absorption studies with polyclonal rabbit immune sera against heated (100 degrees C, 1 h) cells of serovar candidate strains of genospecies 3 permitted identification of 13 serovars. Minor one-way crossreactions were noted between serovars 10 and 8 and between serovars 2 and 12, respectively. Isolates of serovar 13 cross-reacted extensively one-way with serovar 2 and less so with serovars 4 and 12. Genospecies 3 serovars 3, 7, 8, and 9 cross-reacted with Acinetobacter baumannii serovars 19, 21, 6, and 15, respectively.

Acinetobacter baumannii serotyping for delineation of outbreaks of nosocomial cross-infection

A total of 152 clinical isolates of Acinetobacter baumannii from 152 patients were identified by carbon source utilization tests and examined serologically. Polyclonal rabbit immune sera against A. baumannii strains were used in checkerboard tube agglutination tests, and 20 serovars were identified. One (serovar 19) cross-reacted with genospecies 3 (serovar 3), a closely related member of the genus Acinetobacter. Several outbreaks of nosocomial cross-infection caused by serovars 4 and 10 were delineated.

The inanimate environment of an intensive care unit as a potential source of nosocomial bacteria: evidence for long survival of Acinetobacter calcoaceticus

Environmental surface and personnel hand impression cultures were obtained during 13 sampling periods in the University of Virginia Pediatric Intensive Care Unit to document potential reservoirs of nosocomial pathogens. In 78 environmental cultures Staphylococcus aureus was found eight times and gram-negative bacilli ten times. The patient chart cover was the most commonly contaminated surface. Acinetobacter calcoaceticus was found in five of ten cultures positive for gram-negative bacilli. Thirty of 59 hand cultures were positive for S aureus and gram-negative bacilli; nurses and residents had both, respiratory therapists only gram-negative bacilli, and A calcoaceticus was the most commonly isolated bacterium of potentially nosocomial significance (14/30). Laboratory investigation of bacterial survival revealed that gram-negative bacilli survived on a dry formica surface from a few hours up to three days but Acinetobacter survived up to 13 days. Since A calcoaceticus has been implicated in many nosocomial infections, its long survival on a dry surface may be an additional factor in its transmission in hospitals and suggests that more attention be paid to environmental surfaces as a source of significant nosocomial pathogens.