Epidemiological markers of Acinetobacter baumannii clinical isolates from a spinal cord injury unit

Clinical Features and Epidemiology ofAcinetobacter baumanniiColonization and Infection in Spanish Hospitals

Objective:

To investigate the clinical features and the epidemiology ofAcinetobacter baumanniiin Spanish hospitals.

Design:

Prospective multicenter cohort study.

Setting:

Twenty-seven general hospitals and one paraplegic center in Spain.

Methods:

All cases ofA. baumanniicolonization or infection detected by clinical samples during November 2000 were included. Isolates were identified using phenotypic and genotypic methods. The molecular relatedness of the isolates was assessed by pulsed-field gel electrophoresis.

Results:

Twenty-five (89%) of the hospitals had 221 cases (pooled rate in general hospitals, 0.39 case per 1,000 patient-days; range, 0 to 1.17). The rate was highest in intensive care units (ICUs). Only 3 cases were pediatric. The mean age of the patients in the general hospitals was 63 years; 69% had a chronic underlying disease and 80% had previously received antimicrobial treatment. Fifty-three percent of the patients had an infection (respiratory tract, 51%; surgical site, 16%; and urinary tract, 11%). Crude mortality was higher in infected than in colonized patients (27% vs 10%; relative risk, 1.56; 95% confidence interval, 1.2 to 2.0;P= .003). Molecular analysis disclosed 79 different clones. In most hospitals, a predominant epidemic clone coexisted with other sporadic clones. Imipenem resistance was present in 39% of the hospitals.

Conclusions:

A. baumanniiwas present in most participating Spanish hospitals (particularly in ICUs) with different rates among them. The organisms mainly affected predisposed patients; half of them were only colonized. Epidemic and sporadic clones coexisted in many centers.

Clonal diversity of nosocomial epidemic Acinetobacter baumannii strains isolated in Spain

Acinetobacter baumannii is one of the major pathogens involved in nosocomial outbreaks. The clonal diversity of 729 epidemic strains isolated from 19 Spanish hospitals (mainly from intensive care units) was analyzed over an 11-year period. Pulsed-field gel electrophoresis (PFGE) identified 58 PFGE types that were subjected to susceptibility testing, rpoB gene sequencing, and multilocus sequence typing (MLST). All PFGE types were multidrug resistant; colistin was the only agent to which all pathogens were susceptible. The 58 PFGE types were grouped into 16 clones based on their genetic similarity (cutoff of 80%). These clones were distributed into one major cluster (cluster D), three medium clusters (clusters A, B, and C), and three minor clusters (clusters E, F, and G). The rpoB gene sequencing and MLST results reflected a clonal distribution, in agreement with the PFGE results. The MLST sequence types (STs) (and their percent distributions) were as follows: ST-2 (47.5%), ST-3 (5.1%), ST-15 (1.7%), ST-32 (1.7%), ST-79 (13.6%), ST-80 (20.3%), and ST-81 (10.2%). ST-79, ST-80, and ST-81 and the alleles cpn60-26 and recA29 are described for the first time. International clones I, II, and III were represented by ST-81, ST-2, and ST-3, respectively. ST-79 and ST-80 could be novel emerging clones. This work confirms PFGE and MLST to be complementary tools in clonality studies. Here PFGE was able to demonstrate the monoclonal pattern of most outbreaks, the inter- and intrahospital transmission of bacteria, and their endemic persistence in some wards. MLST allowed the temporal evolution and spatial distribution of Spanish clones to be monitored and permitted international comparisons to be made.

Integron-mediated antibiotic multiresistance in Acinetobacter baumannii clinical isolates from Spain

OBJECTIVE

To determine whether non-epidemiologically related, antibiotic-resistant isolates of Acinetobacter baumannii from different geographical origins possess common type 1 integrons.

METHODS

The epidemiologic relationships between seven A. baumannii strains recovered from different Spanish hospitals were established by pulsed-field gel electrophoresis, the presence of integrons being determined by PCR and DNA sequencing.

RESULTS

Integron analysis showed the presence of four different integrons, containing six different known genes (aacC1, aacA4, aadA1, aadB, oxa21 and oxa37) plus an ORF. It was found that the same integron was present in different unrelated strains and that related strains could have different integrons.

CONCLUSION

These results show the potential risk of integron dissemination among different strains of A. baumannii.

Multiresistant Acinetobacter infections: a role for sulbactam combinations in overcoming an emerging worldwide problem

Recent studies have highlighted the emergence of infections involving multiresistant Acinetobacter clinical isolates. Sulbactam offers direct antimicrobial activity against Acinetobacter species. Accordingly, co-administration of sulbactam with ampicillin or cefoperazone offers the potential of effective empirical therapy against Acinetobacter and other bacteria such as Enterobacteriaceae in institutions in which they are susceptible. Many in vitro studies have indicated that Acinetobacter remains fully susceptible to ampicillin-sulbactam or cefoperazone-sulbactam. Furthermore, ampicillin-sulbactam has proven clinically effective and well tolerated in the treatment of severe acinetobacter infections, including bacteremia. Therefore, ampicillin-sulbactam is a sensible option for the treatment of life-threatening acinetobacter infections.

Hospital-acquired urinary tract infections associated with the indwelling catheter

Indwelling urethral catheters are commonly used in patients admitted to acute care hospitals. Forty percent of nosocomial infections occur in the urinary tract, and greater than 80% of these infections are secondary to an indwelling urethral catheter. Fortunately, the majority of catheters are left indwelling for a short period of time. The duration of catheterization is directly related to the development of bacteriuria, nosocomial infection, and possible bacteremia with sepsis. A relatively low percentage of patients become infected during the first 3 to 5 days if sterile technique and proper maintenance of a closed system are performed. Bacteria may grow in the urine (planktonic) and ascend via the lumen, or bacteria in the biofilm around the outside of the catheter may infect the bladder. Most organisms are from the patient's intestinal flora, but exogenous sources on or near the patient may be involved. The major morbid events associated with the catheter are fever and the possible progression to bacteremia and sepsis. Early recognition of complications and arresting their progression, especially in the high-risk patient, are essential. Current research is directed at developing ways to reduce infection beyond the sterile closed system.

Unusual genetic heterogeneity of Acinetobacter baumannii isolates in a university hospital in Italy

BACKGROUND

Acinetobacter baumannii has become an increasingly important nosocomial pathogen, particularly in intensive care units (ICUs). The aim of this investigation was to study the molecular epidemiology of A baumanii in a university hospital in Italy.

METHODS

All A baumanii isolates were collected and typed with phenotypic and genotypic methods during a 7-month period. A 1-year prospective surveillance of ICU-acquired infections was performed by using the National Nosocomial Infections Surveillance methodology.

RESULTS

A baumanni accounted for 28.4% of all infections and 46.7% of all pneumonia acquired in the ICU, with a nosocomial infection rate of 12.4% or 8 infections per 1000 patient-days. Risk factors for A baumannii acquisition in the ICU were mechanical ventilation and previous use of broad-spectrum antibiotics, whereas administration of carbapenems showed a significant protective effect. Pulsed-field gel electrophoresis of genomic Apa I digests identified at least 5 outbreaks in the ICU caused by 5 different clones, one replacing the other in a well-defined temporal order.

CONCLUSIONS

Whereas the sequential temporal cluster of epidemic clones in the ICU is intriguing and requires further research, the clear evidence of cross-contamination of A baumannii isolates involved with infections in the ICU demands extensive preventive efforts.

Spread of amikacin resistance in Acinetobacter baumannii strains isolated in Spain due to an epidemic strain

Sixteen amikacin-resistant clinical Acinetobacter baumannii isolates from nine different hospitals in Spain were investigated to determine whether the high incidence of amikacin-resistant A. baumannii was due to the dissemination of an amikacin-resistant strain or to the spread of an amikacin resistance gene. The epidemiological relationship studied by repetitive extragenic palindromic PCR and low-frequency restriction analysis of chromosomal DNA showed that the same clone was isolated in eight of nine hospitals, although other clones were also found. The strains were studied for the presence of the aph(3')-VIa and aac(6')-I genes, which encode enzymes which inactivate amikacin, by PCR. All 16 clinical isolates had positive PCRs with primers specific for the amplification of the aph(3')-VIa gene, whereas none had a positive reaction for the amplification of the aac(6')-I gene. Therefore, the high incidence of amikacin resistance among clinical A. baumannii isolates in Spain was mainly due to an epidemic strain, although the spread of the aph(3')-VI gene cannot be ruled out.

Verification of a PCR-based typing method for Acinetobacter baumannii in a pseudo-outbreak investigation

Acinetobacter spp. isolates were increasingly obtained from clinical specimens and sterility samples, and a subsequent epidemiological investigation implicated an intermittently contaminated supply of commercially acquired enrichment broths. Typing was performed with DNA amplification by the polymerase chain reaction (PCR) using enterobacterial repetitive intergenic consensus sequence primers, ERIC2 and reverse ERIC1R. The reliability of this PCR-based typing method was verified by the ability of the technique to demonstrate homology and differences among isolates from an epidemiologically well-defined pseudo-outbreak.

Investigation of the epidemiology of hospital isolates of Acinetobacter anitratus by two molecular methods

Two hundred and two isolates of Acinetobacter anitratus from 126 patients in 36 wards belonging to 11 specialties of a university teaching hospital were compared by ribotyping and restriction enzyme digest analysis (REA) of total DNA. Forty-six groups were defined by both techniques and there was 96 center dot 5% agreement between the methods for the designation of isolates into groups. Only two groups were endemic and circulating in the whole hospital while others were less common. Burns and intensive therapy units had the highest number of isolates and these were mainly of the two endemic groups while renal dialysis and neonatal units had isolates belonging to the less common groups. Of the 32 patients with multiple isolates, 17 were infected or colonized at different sites by two and up to four groups of A. anitratus. Both ribotyping and REA of total DNA are discriminatory methods for typing A. anitratus, however, the latter is a simpler and more rapid method and it can be used in a routine clinical laboratory.

Mutation in the gyrA gene of quinolone-resistant clinical isolates of Acinetobacter baumannii

The gyrA gene mutations associated with quinolone resistance were determined in 21 epidemiologically unrelated clinical isolates of Acinetobacter baumannii. Our studies highlight the conserved sequences in the quinolone resistance-determining region of the gyrA gene from A. baumannii and other bacteria. All 15 isolates for which the MIC of ciprofloxacin is > or = 4 micrograms/ml showed a change at Ser-83 to Leu. Six strains for which the MIC of ciprofloxacin is 1 microgram/ml did not show any change at Ser-83, although a strain for which the MIC of ciprofloxacin is 1 microgram/ml exhibited a change at Gly-81 to Val. Although it is possible that mutations in other locations of the gyrA gene, the gyrB gene, or in other genes may also contribute to the modulation of the MIC level, our results suggest that a gyrA mutation at Ser-83 is associated with quinolone resistance in A. baumannii.