Effect of mutator P. aeruginosa on antibiotic resistance acquisition and respiratory function in cystic fibrosis

BACKGROUND

Cystic fibrosis patients suffer from recurrent bacterial infections that result in progressive deterioration of their respiratory function. Despite intensive antibiotic treatment, Pseudomonas aeruginosa is the main cause of such infections, with clones progressively developing multiple antibiotic resistance. We determined the relationship between the presence of P. aeruginosa mutator strains and cystic fibrosis clinical characteristics.

METHODS

We analyzed 136 strains of P. aeruginosa isolated from the expectorations of 36 CF patients. On all strains, mutation frequencies were determined by the mutation rate to rifampicin, and antibiotic susceptibility was determined by the disk diffusion method. The epidemiological relatedness of these 136 P. aeruginosa strains was studied by pulsed-field gel electrophoresis. The appearance of new antibiotic resistance by sequential analysis of genotypically identical strains was determined. Lung function test results, that is, forced expiratory volume in 1 sec and vital capacity, were also recorded from these patients.

RESULTS

We showed that bacteria with an enhanced mutation rate increase the rate of acquisition of new antibiotic resistance threefold and are associated with the deterioration of lung function.

CONCLUSIONS

This study demonstrates the effect of mutator bacteria on the efficiency of patient treatment and on their respiratory function. Given the consequence of antibiotic treatment failure and lung deterioration on the prognosis of CF patients, antibiotic treatment strategies may need to be optimized to prevent the emergence of mutator clones.

Severe osteoarticular infection associated with Panton-Valentine leukocidin-producing Staphylococcus aureus

We report here a case of osteoarticular infection associated with Panton-Valentine leukocidin-producing Staphylococcus aureus. The 3-year-old child presented osteoarthritis associated with toxic shock syndrome, which was complicated by thrombosis, pneumonia, and diaphysitis, despite appropriate antibiotic treatment. Osteitis associated with toxinogenic S. aureus is rarely described. This case highlights the need of early and aggressive surgical treatment, in addition to appropriate antimicrobial therapy.

Bacterial aetiology of acute osteoarticular infections in children

AIM

To study the bacterial aetiology of acute osteoarticular infections in children and to analyse the efficiency of culture methods.

METHODS

Bacteriological data of 407 cases of clinically suspected osteoarticular infections affecting 406 children hospitalized in an orthopaedic surgery department between 1999 and 2002 were retrospectively reviewed.

RESULTS

Bacterial cultures from clinical specimens were positive in 74 cases (18%): 38 cases of septic arthritis and 36 cases of bone infections (osteitis, osteomyelitis or osteoarthritis). The use of liquid medium bottles to grow bacteria from articular fluids increased the rate of positive cultures compared to the use of standard solid media (p = 0.0001). The most commonly recovered pathogen was Staphylococcus aureus (44%) followed by Kingella kingae (14%), Streptococcus pyogenes (10%) and Streptococcus pneumoniae (10%). K. kingae was most frequently isolated among children under 36 mo of age (p = 0.0003), whereas S. aureus was most frequently isolated among children over 36 mo (p = 0.0015).

CONCLUSION

By improving our culture method, we observed a recrudescence of isolation of K. kingae, but S. aureus remains the main pathogen isolated from osteoarticular infections in children. This finding is useful for the adaptation of a probabilistic antibiotic treatment of these infections.

Étude descriptive des bactériémies dans un hôpital gériatrique universitaire

OBJECTIVES

To describe clinical features, microbiologic characteristics and outcome of bacteremia in the elderly patients hospitalized in a geriatric hospital.

PATIENTS AND METHODS

All episodes of bacteremia diagnosed from January 1(st) to December 31(st) 1998 were analysed, excluding false-positive cases due to skin contamination. The hospital comprises 1084 geriatric beds distributed as 111 in acute care (ACF), 333 in rehabilitation and intermediate-care (RICF), and 516 in long-term-care facilities (LTCF).

RESULTS

Sixty-six episodes of bacteremia were observed in 65 patients. Among them 59 (89%) were nosocomial bacteremia distributed as 20 in ACF, 29 in RICF and 10 in LTCF (rates of 0.6, 0.35, and 0.05 episodes per 1000 patient-days, respectively.). Escherichia coli and Staphylococcus aureus were the main bacterial species involved in 31% and 28% of the cases, respectively. E. coli strains were 50% resistant to amoxicillin and 41% resistant to co-amoxiclav, and 68% of S. aureus strains were resistant to methicillin. Portals of entry were urinary tract (44%), respiratory tract (14%), digestive tract (11%), and soft tissue (8%). The same bacterial strain as in bacteremia was isolated from a peripheric site in 30 cases (47%), most of them being urines. For 15% cases, portal of entry cannot be determined. Mortality associated to nosocomial bacteremia was 25%, and death was significantly associated to MRSA, urinary or intravascular devices, chronic wounds and inappropriate antibiotic prescription.

CONCLUSION

In geriatric hospitals, bacteremia are mainly nosocomial cases. Prevention should focus on indwelling devices and antibiotic resistance.

Culture-negative pericarditis caused by Neisseria meningitidis serogroup C

We describe a case of primary purulent culture-negative pericarditis caused by Neisseria meningitidis serogroup C occurring in an 8-month-old previously healthy boy, which was detected in pericardial fluid by broad-spectrum PCR amplification.